JP6644307B2 - Force sensor - Google Patents

Description

  The present invention relates to a force sensor, and more particularly to a sensor having a function of outputting a force acting in a predetermined axial direction and a moment (torque) acting around a predetermined rotation axis as an electric signal.

  A force sensor having a function of outputting, as an electric signal, a force acting along a predetermined axis direction and a moment acting around a predetermined rotation axis is described in, for example, Patent Document 1, and the force of an industrial robot is disclosed. Widely used for control. In recent years, it has also been adopted for life support robots. Under such circumstances, the magnitude of the force or moment to be detected is wide, and the development of a force sensor capable of measuring such a wide range of force or moment with high accuracy and high sensitivity is being promoted. .

  By the way, as a force sensor, a capacitance-type force sensor that detects a force or a moment based on the amount of change in the capacitance value of the capacitive element, or a force sensor based on the amount of change in the electric resistance value of the strain gauge. Or, a strain gauge type force sensor for detecting a moment is used. For this reason, it is convenient if a force sensor capable of detecting force or moment with high accuracy and high sensitivity can be provided regardless of whether it is configured as a capacitance type or a strain gauge type.

JP-A-2004-354049

  The present invention has been made in view of the above circumstances. That is, an object of the present invention is to provide a force sensor capable of detecting a force or moment with high accuracy and high sensitivity regardless of whether it is configured as a capacitance type or a strain gauge type. .

The present invention is a force sensor for detecting a uniaxial force,
A fixed part,
A movable portion that moves relative to the fixed portion by the action of a force,
A deformed body connected to the fixed part and the movable part, the elastic part being elastically deformed in a direction non-parallel to the uniaxial direction by the movable part moving relatively to the fixed part,
A detection circuit that outputs an electric signal indicating a force applied to the movable portion based on the elastic deformation generated in the deformable body,
The deformable body includes a first detection portion having a first spring constant, and a second detection portion having a second spring constant different from the first spring constant,
The detection circuit is a force sensor that outputs the electric signal based on elastic deformation occurring in at least one of the first detection portion and the second detection portion.

  According to the present invention, by disposing a capacitive element at a detection site where a spring constant is relatively small, that is, a detection site where relatively large elastic deformation occurs, a force sense capable of detecting force with high accuracy and high sensitivity is provided. A sensor can be provided. Furthermore, by arranging the strain gauge at the detection site where the spring constant is relatively large, that is, the detection site where the stress generated by the elastic deformation is relatively large, the force that can detect the force with high accuracy and high sensitivity is obtained. A haptic sensor can be provided. As described above, according to the present invention, it is possible to provide a force sensor capable of detecting force with high accuracy and high sensitivity regardless of whether it is configured as a capacitance type or a strain gauge type.

  The first detection part and the second detection part may be arranged in parallel between the movable part and the fixed part. In this case, since a large deformation can be caused in the first detection site and the second detection site, the applied force can be detected with higher accuracy and higher sensitivity.

The first detection portion has a shape along a part of an arc having a predetermined radius,
The second detection portion may have a shape along a part of an arc having a radius different from the predetermined radius. In this case, displacement can be generated in the first detection portion and the second detection portion in a direction orthogonal to the applied force, so that force measurement is easy.

The above force sensor can be configured as a capacitance type. That is, the force sensor includes a displacement electrode disposed on at least one of the first detection portion and the second detection portion,
A fixed electrode that is arranged to face the displacement electrode and does not move relative to the fixed portion,
The displacement electrode and the fixed electrode constitute a capacitance element,
The detection circuit may output an electric signal indicating a force acting on the movable portion based on a variation amount of a capacitance value of the capacitance element.

Alternatively, the above-mentioned force sensor can be configured as a strain gauge type. That is, the force sensor is provided with a strain gauge on at least one of the first detection portion and the second detection portion,
The detection circuit may output an electric signal indicating a force acting on the movable portion based on a variation amount of an electric resistance value of the strain gauge.

The first detection portion has a first displacement portion, and a pair of first deformation portions provided on both sides of the first displacement portion and connected to the fixed portion and the movable portion, respectively.
The second detection portion may include a second displacement portion, and a pair of second deformation portions provided on both sides of the second displacement portion and connected to the fixed portion and the movable portion, respectively. .

  In this case, a displacement in a direction orthogonal to the applied force can be generated in the first detection portion and the second detection portion in a relatively small space.

With such a force sensor having the first detection portion and the second detection portion, it is easy to provide a capacitance type force sensor with high accuracy and high sensitivity. That is, a displacement electrode disposed on at least one of the first displacement portion of the first detection portion and the second displacement portion of the second detection portion,
A fixed electrode that is arranged to face the displacement electrode and does not move relative to the fixed portion,
The displacement electrode and the fixed electrode constitute a capacitance element,
The detection circuit may output an electric signal indicating the uniaxial force acting on the movable portion based on a variation amount of a capacitance value of the capacitance element.

Of course, the force sensor having such a first detection part and a second detection part may be configured as a strain gauge type. That is, at least one of the first displacement portion and the second displacement portion is made of a material having elasticity, and a strain gauge is disposed on a surface thereof.
The detection circuit may be configured to output an electric signal indicating the uniaxial force acting on the movable portion based on a variation amount of an electric resistance value of the strain gauge.

Alternatively, the present invention is a force sensor that detects at least one of a force in each axis direction and a moment around each axis in an XYZ three-dimensional coordinate system,
A fixed part fixed with respect to the XYZ three-dimensional coordinate system;
A movable portion that moves relative to the fixed portion by the action of force or moment,
A deformable body that is connected to the fixed part and the movable part and that elastically deforms by moving the movable part relative to the fixed part;
A detection circuit that outputs an electric signal indicating a force or a moment applied to the movable portion based on the elastic deformation generated in the deformable body,
The deformed body is
An annular first deformable body made of a material that undergoes elastic deformation by the action of a force or a moment and having a first through opening;
An annular second deformable body that is made of a material that undergoes elastic deformation by the action of force or moment, has a second through opening, and surrounds the first deformable body;
The first deformation body and the second deformation body are connected by a connection member,
The first deformation body has at least one first detection portion having a first spring constant,
The second deformed body has at least one second detection portion having a second spring constant different from the first spring constant,
The detection circuit is a force sensor that outputs the electric signal based on elastic deformation occurring in at least one of the first detection portion and the second detection portion.

  According to the present invention, force or moment can be detected with high accuracy and high sensitivity by arranging a capacitive element at a detection site where a spring constant is relatively small, that is, a detection site where relatively large elastic deformation occurs. A force sensor can be provided. Furthermore, by locating the strain gauge at the detection site where the spring constant is relatively large, that is, the detection site where the stress generated by the elastic deformation is relatively large, force or moment can be detected with high accuracy and high sensitivity. It is possible to provide a simple force sensor. According to the present invention, it is possible to provide a force sensor capable of detecting a force or moment with high accuracy and high sensitivity regardless of whether it is configured as a capacitance type or a strain gauge type. it can.

  The first deformable body and the second deformable body are both annular, and may be concentric with each other. In this case, the force sensor can be configured with a simple configuration.

The above force sensor can be configured as a capacitance type. That is, a displacement electrode disposed on at least one of the first detection site of the first deformable body and the second detection site of the second deformable body,
A fixed electrode that is arranged to face the displacement electrode and does not move relative to the fixed portion,
The displacement electrode and the fixed electrode constitute a capacitance element,
The detection circuit may output an electric signal indicating an applied force or moment based on a variation amount of a capacitance value of the capacitance element.

Alternatively, the above-mentioned force sensor can be configured as a strain gauge type. That is, a strain gauge is provided on at least one of the first deformation body and the second deformation body,
The detection circuit may output an electric signal indicating the applied force or moment based on the amount of change in the electric resistance value of the strain gauge.

  The connecting member includes a first connecting member that connects two portions where a positive X axis overlaps the first deformed body and the second deformed body, as viewed from the Z axis direction, and a positive Y axis that is the first connecting member. A second connecting member that connects two parts overlapping the deformed body and the second deformed body, and a third connecting member that connects two parts where the negative X connects the first deformed body and the second deformed body. And a fourth connecting member for connecting two portions where the negative Y axis overlaps the first deformed body and the second deformed body.

Further, when the V axis and the W axis passing through the origin O and forming 45 ° with respect to the X axis and the Y axis are defined on the XY plane,
The first deformation body has the first detection portion at four portions overlapping the V axis and the W axis when viewed from the Z axis direction,
The second deformation body may have the second detection portion at four portions overlapping the V axis and the W axis when viewed from the Z axis direction.

  In this case, since the applied force or moment causes symmetrical elastic deformation in the first deformable body and the second deformable body, it is easy to detect the force or moment.

Further, the first deformed body has at least one first gap,
The first detection portion is interposed in the first gap,
The first detection portion has a first displacement portion, and a pair of first deformation portions provided on both sides of the first displacement portion and connected to both ends of the corresponding first gap,
The second variant has at least one second gap,
The second detection portion is interposed in the second gap,
The second detection portion may include a second displacement portion and a pair of second deformation portions provided on both sides of the second displacement portion and connected to both ends of the corresponding second gap.

  In this case, a displacement in a direction orthogonal to the applied force can be generated in the first detection portion and the second detection portion in a relatively small space.

With such a force sensor having the first detection portion and the second detection portion, it is easy to provide a capacitance type force sensor with high accuracy and high sensitivity. That is, a displacement electrode disposed on at least one of each first displacement portion of the first detection portion and each second displacement portion of the second detection portion,
A fixed electrode that is arranged to face the displacement electrode and does not move relative to the fixed portion,
The displacement electrode and the fixed electrode constitute a capacitance element,
The detection circuit may output an electric signal indicating a force or a moment applied to the movable portion based on a variation amount of a capacitance value of the capacitance element.

Of course, the force sensor having such a first detection part and a second detection part may be configured as a strain gauge type. That is, at least one of each of the first displacement portions and each of the second displacement portions is made of a material having elasticity, and a strain gauge is disposed on the surface thereof,
The detection circuit may be configured to output an electric signal indicating the uniaxial force acting on the movable portion based on a variation amount of an electric resistance value of the strain gauge.

In another example, each first detection portion has a smaller thickness than other regions of the first deformed body,
Each second detection portion may be thinner than other regions of the second deformed body.

  In this case, since the degree of elastic deformation generated in the first detection portion and the second detection portion can be adjusted as desired, a more accurate and sensitive force sensor can be provided.

  In the above-described force sensor, the first detection portion and the second detection portion may have an arc shape. Also in this case, a displacement in a direction orthogonal to the applied force can be generated in the first detection portion and the second detection portion in a relatively small space.

Alternatively, according to the present invention, it is possible to diagnose the failure of the force sensor using a single force sensor. That is, such a force sensor detects a uniaxial force,
A fixed part,
A movable portion that moves relative to the fixed portion by the action of a force,
A deformed body connected to the fixed part and the movable part, the elastic part being elastically deformed in a direction non-parallel to the uniaxial direction by the movable part moving relatively to the fixed part,
A detection circuit that outputs an electric signal indicating a force applied to the movable portion based on the elastic deformation generated in the deformable body,
The deformable body includes a first detection portion having a first spring constant, and a second detection portion having a second spring constant different from the first spring constant,
The detection circuit,
Outputting, as the electric signal, a first electric signal provided based on elastic deformation generated at the first detection portion and a second electric signal provided based on elastic deformation generated at the second detection portion; ,
The force sensor is configured to determine whether the force sensor is functioning normally based on the first electric signal and the second electric signal.

Alternatively, the force sensor capable of performing a failure diagnosis detects at least one of a force in each axis direction and a moment around each axis in the XYZ three-dimensional coordinate system,
A fixed part fixed with respect to the XYZ three-dimensional coordinate system;
A movable portion that moves relative to the fixed portion by the action of force or moment,
A deformable body that is connected to the fixed part and the movable part and that elastically deforms by moving the movable part relative to the fixed part;
A detection circuit that outputs an electric signal indicating a force or a moment applied to the movable portion based on the elastic deformation generated in the deformable body,
The deformed body is
An annular first deformable body made of a material that undergoes elastic deformation by the action of a force or a moment and having a first through opening;
An annular second deformable body that is made of a material that undergoes elastic deformation by the action of force or moment, has a second through opening, and surrounds the first deformable body;
The first deformation body and the second deformation body are connected by a connection member,
The first deformation body has at least one first detection portion having a first spring constant,
The second deformed body has at least one second detection portion having a second spring constant different from the first spring constant,
The detection circuit,
As the electric signal, a first electric signal provided based on elastic deformation generated in the first detection portion, and a second electric signal provided based on elastic deformation generated in at least one of the second detection portion, And output
The force sensor is configured to determine whether the force sensor is functioning normally based on the first electric signal and the second electric signal.

  In these force sensors, the detection circuit includes a storage unit that stores a ratio between the first electric signal and the second electric signal in a state where the force sensor is functioning normally as a reference ratio. It is determined whether the difference between the ratio of the first electrical signal to the second electrical signal and the reference ratio is within a predetermined range, thereby determining whether the force sensor is functioning normally. You may be able to. In this case, the failure of the force sensor can be reliably determined. The principle of this determination will be described later in detail.

FIG. 1 is a schematic top view showing a basic structure of a force sensor according to a first embodiment of the present invention. 2 is a chart showing displacement in the X-axis direction and stress in the Y-axis direction generated at each detection site when the movable portion of the basic structure in FIG. FIG. 2 is a schematic top view showing a capacitance type force sensor having the basic structure of FIG. 1. FIG. 2 is a schematic top view showing a strain gauge type force sensor having the basic structure of FIG. 1. FIG. 3 is a schematic top view showing a modification of the basic structure of FIG. 1. FIG. 6 is a schematic top view showing a state where a force acts on the basic structure of FIG. 5. FIG. 6A shows a state in which a compressive force f1 along the Y-axis direction acts on the basic structure, and FIG. 6B shows a state in which a tensile force f2 along the Y-axis direction acts on the basic structure. is there. FIG. 6 is a partial schematic top view of a first detection portion A of a strain gauge type force sensor employing the modification shown in FIG. 5. FIG. 7A is a schematic diagram showing an initial state of the first detection site A, and FIG. 7B is a schematic diagram showing the first detection site A when a compressive force acts on the basic structure. FIG. 7C is a schematic view showing the first detection portion A when a tensile force acts on the basic structure. FIG. 9 is a schematic top view illustrating a basic structure of a force sensor according to a second embodiment of the present invention. FIG. 9 is a schematic top view showing the basic structure of FIG. 8 when a moment about the Z axis acts on the movable part. FIG. 9 is a schematic top view showing a second quadrant portion of the basic structure in FIG. 8. FIG. 9 is a schematic upper view showing a capacitance type force sensor having the basic structure of FIG. 8. FIG. 9 is a schematic top view showing a strain gauge type force sensor having the basic structure of FIG. 8. FIG. 9 is a schematic top view showing a first modification of the basic structure of FIG. 8. FIG. 9 is a schematic top view showing a second modification of the basic structure in FIG. 8. FIG. 10 is a schematic top view showing a third modification of the basic structure in FIG. 8. FIG. 9 is a diagram for explaining elastic deformation that occurs in a deformable body when a force + Fx in the positive X-axis direction acts on the movable portion of the basic structure in FIG. 8. FIG. 9 is a diagram for describing elastic deformation that occurs in a deformable body when a force + Fy in the positive Y-axis direction acts on the movable portion of the basic structure in FIG. 8. FIG. 9 is a diagram for explaining stress generated at a detection portion of a deformable body when a force in the positive direction of the X-axis acts on the movable portion of the basic structure in FIG. 8. FIG. 9 is a diagram for explaining stress generated in a detection unit of a deformable body when a force + Fy in the positive Y-axis direction acts on the movable unit having the basic structure in FIG. 8. FIG. 9 is a schematic top view showing the basic structure of FIG. 8 in which the structure shown in FIG. 21 is a schematic side view of a 1-1 detection site A1 of the basic structure shown in FIG. 20 as viewed from the V-axis positive direction. FIG. 21 is a diagram for explaining stress generated at a detection portion of a deformed body when a moment about the Z axis acts on the movable portion of the basic structure in FIG. 20. 21 is a diagram for describing a force acting on a detection portion of a deformable body when a force in the X-axis positive direction acts on the movable portion of the basic structure in FIG. 20. FIG. When no metal fatigue occurs in the force sensor of FIG. 3 (initial state), the magnitude of the force acting on the force sensor, and the first electric signal T1a and the second electric signal T2a output from the force sensor. 5 is a graph showing the relationship Relationship between the magnitude of the force acting on the force sensor and the first electric signal T1b and the second electric signal T2b output from the force sensor when metal fatigue occurs in the force sensor of FIG. FIG. When no metal fatigue occurs in the force sensor of FIG. 4 (initial state), the magnitude of the force acting on the force sensor and the first electric signal T1a and the second electric signal T2a output from the force sensor 6 is a graph showing the relationship between. Relationship between the magnitude of the force acting on the force sensor and the first electric signal T1b and the second electric signal T2b output from the force sensor when metal fatigue occurs in the force sensor of FIG. FIG. It is the schematic which shows the modification of a detection part. FIG. 29A is a schematic diagram showing the detection site when a compressive force in the Y-axis direction is applied to the detection site shown in FIG. 28, and FIG. 29B is a diagram showing the detection site shown in FIG. It is the schematic which shows the said detection part when the tensile force of a direction acts. FIG. 29 is a schematic top view showing an example of a deformed body having the detection site shown in FIG. 28. FIG. 31A is a schematic top view showing another example of the deformed body having the detection site shown in FIG. 28, and FIG. 31B is a cross-sectional view taken along line bb of FIG. 31A. . FIG. 29 is a schematic diagram showing a detection site in FIG. 28 where a capacitance element is arranged. FIG. 29 is a schematic diagram showing a detection site in FIG. 28 where a strain gauge is arranged.

<<<< §1. Force sensor according to first embodiment of the present invention >>>
Hereinafter, the force sensor according to the first embodiment of the present invention will be described in detail with reference to the accompanying drawings.

<1-1. Basic structure>
FIG. 1 is a schematic top view showing a basic structure 1 of the force sensor according to the first embodiment of the present invention. In this drawing, it is assumed that the X axis is defined in the horizontal direction, the Y axis is defined in the vertical direction, and the Z axis is defined in the depth direction. As shown in FIG. 1, the basic structure 1 includes a fixed part 10, a movable part 20 that relatively moves along the Y-axis direction with respect to the fixed part 10 by the action of a force, and a fixed part 10 and a movable part 20. And a deformable body 30 that is elastically deformed when the movable section 20 moves relative to the fixed section 10.

  The basic structure 1 according to the present embodiment is used for a force sensor capable of detecting a force in the Y-axis direction. As shown in FIG. 1, the fixed part 10 and the movable part 20 are arranged at a predetermined interval in the Y-axis direction. The movable portion 20 functions as a force receiving member that receives a force.

  The deformable body 30 connected to the fixed part 10 and the movable part 20 has a first deformable body 31 and a second deformable body 32 arranged in parallel in the X-axis direction. The first deformable body 31 is connected to the first fixed portion side connection portion 31f connected to the fixed portion 10 and a second fixed body side connection portion 31f connected to the movable portion 20 and spaced apart from the first fixed portion side connection portion 31f in the Y-axis direction. It has a first movable portion side connection portion 31m and an elastically deformable arc-shaped first elastic body 31e connecting the first fixed portion side connection portion 31f and the first movable portion side connection portion 31m. The second deformable body 32 is connected to the second fixed portion side connecting portion 32f connected to the fixed portion 10 and a second fixed portion side connected portion 32f connected to the movable portion 20 and arranged separately from the second fixed portion side connecting portion 32f in the Y-axis direction. It has a second movable portion side connection portion 32m and an elastically deformable arc-shaped second elastic body 32e connecting the second fixed portion side connection portion 32f and the second movable portion side connection portion 32m. In the present embodiment, as shown in FIG. 1, the first elastic body 31e and the second elastic body 32e are both arranged so as to be convex in the negative X-axis direction (right direction in FIG. 1).

  In the first elastic body 31e and the second elastic body 32e, a portion located closest to the X axis negative direction side (the right side in FIG. 1), that is, the first elastic body 31e and the second elastic body 32e on the X axis negative side. A first detection site A and a second detection site B are defined at sites that provide a tangent parallel to the Y axis when viewed from the Z axis direction. When the basic structure 1 shown in FIG. 1 is used as a force sensor, it acts on the movable part 20 based on the stress or displacement in the X-axis direction generated at the first detection part A and the second detection part B. Force is measured. As shown in FIG. 1, the first elastic body 31e and the second elastic body 32e have different radii of curvature. Specifically, the radius of curvature of the second elastic body 32e is larger than the radius of curvature of the first elastic body 31e. On the other hand, although not shown, the first elastic body 31e and the second elastic body 32e have the same cross-sectional shape cut along the XZ plane. Thus, the spring constant of the second elastic body 32e is smaller than the spring constant of the first elastic body 31e. Here, the spring constant of the first elastic body 31e and the second elastic body 32e is the magnitude of the force acting on the movable part 20 in the Y-axis direction, and the magnitude of the displacement in the X-axis direction generated at the detection parts A and B. Means the value divided by

  FIG. 2 is a table showing the displacement in the X-axis direction and the stress in the Y-axis direction generated at each of the detection portions A and B when the movable portion 20 of the basic structure 1 in FIG. 1 is displaced by 100 μm in the negative direction of the Z-axis. It is.

  As shown in FIG. 2, when the movable portion 20 is displaced (relatively moved) in the negative Y-axis direction (downward in FIG. 1) with respect to the fixed portion 10 by the action of a force, the movable portion 20 is generated at each of the detection portions A and B. The displacement in the X-axis direction and the stress in the Y-axis direction are different from each other. Specifically, when the movable part 20 moves relative to the fixed part 10 by 100 μm in the negative Y-axis direction, the magnitude of the displacement generated in the X-axis direction is larger than that of the first detection part A in the second detection part B. Are larger, and the stress is larger in the first detection portion A than in the second detection portion B. Therefore, in the basic structure 1 shown in FIG. 1, the second detection part B has higher sensitivity than the first detection part A in terms of displacement, and the first structure has a higher sensitivity than the second detection part B in terms of stress. The detection site A has a characteristic of higher sensitivity.

<1-2. Capacitive force sensor>
Next, a capacitance type force sensor 1c using the above basic structure 1 will be described.

  FIG. 3 is a schematic top view showing a capacitance type force sensor 1c according to the basic structure 1 of FIG. As shown in FIG. 3, the force sensor 1 c is disposed to face the first displacement electrode Em 1 disposed at the first detection site A and the first displacement electrode Em 1, and does not move relative to the fixed unit 10. A first fixed electrode Ef1, a second displacement electrode Em2 arranged at the second detection site B, and a second fixed electrode Ef2 arranged facing the second displacement electrode Em2 and not moving relative to the fixed portion 10. ,have. As shown in FIG. 1, the first displacement electrode Em1 and the first fixed electrode Ef1 constitute a first capacitance element C1, and the second displacement electrode Em2 and the second fixed electrode Ef2 constitute a second capacitance element C2. ing. In the present embodiment, the first displacement electrode Em1 and the second displacement electrode Em2 have the same area. Further, the first fixed electrode Ef1 and the second fixed electrode Ef2 have the same area. Further, the effective facing area of the first displacement electrode Em1 and the first fixed electrode Ef1 and the distance between the electrodes are equal to the effective facing area of the second displacement electrode Em2 and the second fixed electrode Ef2 and the distance between the electrodes. Each of the electrodes Em1, Ef1, Em2, and Ef2 is arranged so as to be parallel to the YZ plane.

  Further, as shown in FIG. 3, the force sensor 1 c outputs an electric signal indicating a force in the Y-axis direction applied to the movable unit 20 based on the elastic deformation generated in the first deformable body 31 and the second deformable body 32. It has a detection circuit 40 for outputting. The detection circuit 40 outputs an electric signal indicating a force acting on the movable unit 20 based on the amount of change in the capacitance value of each of the capacitance elements C1 and C2. Note that the wiring for electrically connecting each of the capacitance elements C1 and C2 and the detection circuit 40 is not shown.

  Next, the operation of the force sensor 1c will be described.

  Here, the case where a force in the Y-axis negative direction (downward direction in FIG. 3) acts on the movable portion 20 will be described as an example. When a force in the Y-axis negative direction acts on the movable unit 20, the movable unit 20 moves relative to the fixed unit 10 in the Y-axis negative direction. As a result, the arc-shaped first elastic body 31e and second elastic body 32e are elastically deformed by the action of the compressive force. This elastic deformation is a deformation in which the radii of curvature of both the first elastic body 31e and the second elastic body 32e decrease. Thereby, both the first detection site A and the second detection site B are displaced in the negative direction of the X axis. For this reason, the first capacitance element C1 and the second capacitance element C2 both increase in capacitance value as the distance between the electrode plates decreases. In the present embodiment, as described above, since the spring constant of the second elastic body 32e is smaller than the spring constant of the first elastic body 31e, the displacement of the second detection portion B in the negative direction of the X axis is smaller. Is larger than the displacement of the first detection portion A in the negative direction of the X-axis. For this reason, the capacitance value of the second capacitance element C2 fluctuates more greatly than that of the first capacitance element C1. That is, the second capacitive element C2 has higher sensitivity than the first capacitive element C1.

  Then, the detection circuit 40 measures the force applied to the movable unit 20 based on the amount of change in the capacitance value of one of the first capacitance element C1 and the second capacitance element C2. The capacitance type force sensor 1c is excellent in S / N by measuring the force acting on the basis of the variation amount of the capacitance value of the second capacitance element C2, which has relatively high sensitivity. Measurement becomes possible. Of course, the force acting on the movable portion 20 can be measured based on the amount of change in the capacitance value of the first capacitance element C1, and for example, the change in the capacitance value of the first capacitance element C1 can be measured. The average value of the force measured based on the amount and the force measured based on the amount of change in the capacitance value of the second capacitive element C2 can be treated as the applied force.

  In the above description, the case where a force in the negative direction of the Y-axis acts on the movable portion 20 has been described as an example. Conversely, a force in the positive direction of the Y-axis (upward in FIG. 3) is applied. The force can be measured even if it acts on the movable part 20. In this case, the first elastic body 31e and the second elastic body 32e elastically deform so that their radii of curvature both increase. Accordingly, the first detection part A and the second detection part B are both displaced in the positive direction of the X-axis (left direction in FIG. 3), and the capacitance values of the first capacitance element C1 and the second capacitance element C2 are Both decrease. Note that also in this case, the capacitance value of the second capacitance element C2 fluctuates more greatly than that of the first capacitance element C1.

<1-3. Strain gauge type force sensor>
Alternatively, the basic structure 1 as described above can be used for a strain gauge type force sensor 1s.

  FIG. 4 is a schematic top view showing a strain gauge type force sensor 1s according to the basic structure 1 of FIG. As shown in FIG. 4, the force sensor 1 s has a first strain gauge R <b> 1 arranged at the first detection site A and a second strain gauge R <b> 2 arranged at the second detection site B. . The first strain gauge R1 and the second strain gauge R2 have the same characteristics. The other configuration is the same as that of the force sensor 1c shown in FIG. 3 except that it does not have a capacitive element, and thus a detailed description thereof is omitted.

  In addition, as the strain gauges R1 and R2, for example, a metal foil strain gauge or a semiconductor strain gauge can be adopted. The metal foil strain gauge has a property that the resistance value decreases when a compressive stress acts, and conversely, the resistance value increases when a tensile stress acts. The semiconductor strain gauge is a strain gauge utilizing a piezoresistive effect. When a tensile stress acts on the semiconductor strain gauge, the resistance value increases in the p-type semiconductor strain gauge and the n-type semiconductor strain gauge increases. Gauges have the characteristic that the resistance value decreases. On the other hand, when a compressive stress acts on this semiconductor strain gauge, the resistance value decreases in the p-type semiconductor strain gauge and increases in the n-type semiconductor strain gauge. Here, it is assumed that a metal foil strain gauge is employed as the first strain gauge R1 and the second strain gauge R2.

  Next, the operation of the force sensor 1s will be described.

  When a force in the negative direction of the Y-axis acts on the movable portion 20, the movable portion 20 relatively moves in the negative direction of the Y-axis with respect to the fixed portion 10, and as described above, the first elastic body 31e and the second elastic body 32e Elastically deform so that both the radii of curvature decrease. Accordingly, a tensile stress is generated in a region including each of the detection sites A and B on the surface on the negative side of the X-axis of the arc-shaped first elastic body 31e and second elastic body 32e. As described above, since the spring constant of the first elastic body 31e is larger than the spring constant of the second elastic body 32e, the tensile stress generated at the first detection site A is larger than the tensile stress generated at the second detection site B. . This is as described above with reference to FIG. For this reason, the electric resistance value of the first strain gauge R1 fluctuates (increases) more than that of the second strain gauge R2.

  Then, the detection circuit 40 measures the applied force based on the amount of change in the electric resistance value of one of the first strain gauge R1 and the second strain gauge R2. In the strain gauge type force sensor 1 s, by measuring the force acting on the basis of the variation of the electric resistance value of the first strain gauge R <b> 1, which has relatively high sensitivity, measurement excellent in S / N can be performed. It becomes possible. Of course, it is also possible to measure the force acting on the basis of the amount of change in the electric resistance of the second strain gauge R2. For example, the force is measured based on the amount of change in the electric resistance of the first strain gauge R1. The average value of the force and the force measured based on the amount of change in the electric resistance value of the second strain gauge R2 can be treated as the applied force.

  In the above description, the case where the force in the negative direction of the Y-axis acts on the movable portion 20 has been described as an example. On the contrary, the force in the positive direction of the Y-axis (upward in FIG. 4) The force can be measured even if it acts on the movable part 20. In this case, as described above, the first elastic body 31e and the second elastic body 32e are elastically deformed so that their radii of curvature both increase. As a result, compressive stress is generated in a region including each of the detection sites A and B on the surface of the arc-shaped first elastic body 31e and the second elastic body 32e on the negative side of the X-axis, and the electric potential of each of the strain gauges R1 and R2 is increased. The resistance decreases together. Also in this case, the electric resistance of the first strain gauge R1 fluctuates more greatly than that of the second strain gauge R2.

  According to the force sensors 1c and 1s according to the present embodiment as described above, the second capacitance element is provided in the second detection portion B having a relatively small spring constant, that is, the second detection portion B having a relatively large elastic deformation. By disposing C2, it is possible to provide a capacitance type force sensor 1c capable of detecting force with high accuracy and high sensitivity. Alternatively, by disposing the first strain gauge R1 at the first detection site A where the spring constant is relatively large, that is, the first detection site A where the stress generated due to the elastic deformation is relatively large, high accuracy and high accuracy are achieved. A force sensor 1s capable of detecting a force with sensitivity can be provided. As described above, according to the present embodiment, regardless of whether it is configured as a capacitance type or a strain gauge type while having the common basic structure 1, detection of a force acting with high accuracy and high sensitivity is achieved. Can be provided.

<1-4. Basic structure with waveform detection part>
Next, FIG. 5 is a schematic top view showing a modification of the basic structure 1 of FIG. FIG. 6 is a schematic top view showing a state where a force in the Y-axis direction is acting on the basic structure 1w of FIG. FIG. 6A shows a state where a compressive force f1 along the Y-axis direction is acting on the basic structure 1w, and FIG. 6B shows a state where a tensile force f2 along the Y-axis direction is applied to the basic structure 1w. It is working.

  As shown in FIG. 5, in this modified example, two corrugated elastic structures are employed in place of the two arc-shaped elastic members shown in FIG. Here, the elastic structures having these waveforms are referred to as a first detection site A and a second detection site B. As illustrated, the first detection portion A is provided via a first displacement portion 61d and connection portions 61m and 61f provided on both sides of the first displacement portion 61d and arranged at intervals in the Y-axis direction. It has a pair of first deformation parts 61e1 and 61e2 connected to the fixed part 10 and the movable part 20, respectively, and the second detection part B is provided on both sides of the second displacement part 62d and the second displacement part 62d. And a pair of second deformable portions 62e1 and 62e2 connected to the fixed portion 10 and the movable portion 20 via connecting portions 62m and 62f arranged at intervals in the Y-axis direction. As shown in FIG. 5, the pair of second deformed portions 62e1 and 62e2 are configured to stand up in the Y-axis direction more than the pair of first deformed portions 61e1 and 61e2.

  In the case of the example shown here, the pair of first deformed portions 61e1 and 61e2 and the pair of second deformed portions 62e1 and 62e2 are formed of flexible plate-like pieces, and have a first displacement portion 61d and a second displacement portion. 62d is constituted by a third plate-shaped piece. Each plate-like piece is made of the same material as each of the connection portions 61f, 61m, 62f, 62m, but is a relatively thin plate-like member as shown in FIGS. Therefore, it has flexibility.

  In the case of the example shown here, the first displacement portion 61d and the second displacement portion 62d are also flexible because they are thin plate-shaped members. When used as a force sensor, the first displacement portion 61d and the second displacement portion 62d do not necessarily need to be flexible members. On the other hand, when the basic structure 1w is used as a strain gauge type force sensor, the first displacement portion 61d and the second displacement portion 62d need to be members having flexibility. In the example shown in FIGS. 5 and 6, the left and right surfaces of the first displacement portion 61d and the second displacement portion 62d (third plate-shaped piece) are parallel to the YZ plane.

  Next, referring to FIGS. 6A and 6B, when a force along the Y-axis direction is applied to the movable portion 20 of the basic structure 1 w, each of the detection portions A and B has The operation will be described. In FIGS. 6A and 6B, thick black arrows indicate the direction of the acting force, and thick white arrows indicate the directions of the displacement of the displacement units 61d and 62d. I have.

  As shown in FIG. 6 (a), when a compressive force f1 along the Y-axis direction acts on the movable portion 20 of the basic structure 1w, a compression along the Y-axis direction is applied to each of the detection portions A and B. Force acts. Therefore, the postures of the pair of first deformed portions 61e1 and 61e2 and the pair of second deformed portions 62e1 and 62e2 change to a state of lying more horizontally. As a result, each of the displacement portions 61d and 62d is displaced in the negative direction of the X-axis (the right direction in FIG. 6A) as indicated by the white arrow in the figure. On the other hand, as shown in FIG. 6B, when a tensile force f2 in the positive direction of the Y-axis acts on the movable portion 20 of the basic structure 1w, the detection portions A and B are applied along the Y-axis direction. Tensile force acts. Therefore, the postures of the pair of first deformed portions 61e1 and 61e2 and the pair of second deformed portions 62e1 and 62e2 change to a more vertically standing state. As a result, each of the displacement portions 61d and 62d is displaced in the positive direction of the X-axis (the left direction in FIG. 6B), as indicated by white arrows in the figure.

  As described above, in the initial state (see FIG. 5), the pair of first deformed portions 61e1 and 61e2 are configured to rise in the Y-axis direction more than the pair of second deformed portions 62e1 and 62e2. Therefore, as shown in FIGS. 6A and 6B, the displacement caused by the action of the force is relatively larger in the second displacement portion 62d than in the first displacement portion 61d. In other words, the spring constant of the second detection part B is relatively smaller than the spring constant of the first detection part A. Here, the spring constant of the first detection portion A and the second detection portion B means a value obtained by dividing the force acting on the movable portion 20 by the displacement in the X-axis direction generated in the displacement portions 61d and 62d. .

  In the force sensor using the basic structure 1w, the direction and magnitude of the applied force are detected by utilizing such displacement. That is, the direction of the applied force is detected by the displacement direction of each of the displacement portions 61d and 62d, and the magnitude of the applied force is detected by the magnitude of the displacement.

  According to the force sensor according to the present embodiment as described above, the capacitive element C2 is arranged at the second detection portion B having a relatively small spring constant, that is, the second detection portion B at which relatively large elastic deformation occurs. Thus, it is possible to provide the force sensor 1c capable of detecting force with high accuracy and high sensitivity.

  Alternatively, the above basic structure 1w can be used for a strain gauge type force sensor. In order to configure a strain gauge type force sensor, a strain gauge is used instead of the capacitance element arranged in each of the displacement portions 61d and 62d of the capacitance type force sensor, specifically, instead of the displacement electrode. R1 and R2 may be arranged.

  FIG. 7 is a partial schematic top view of the first detection portion A of the strain gauge type force sensor configured as described above. FIG. 7A is a schematic diagram illustrating an initial state of the first detection site A, and FIG. 7B is a schematic diagram illustrating the first detection site A when a compressive force acts on the basic structure 1w. FIG. 7 (c) is a schematic view showing the first detection portion A when a tensile force acts on the basic structure 1w. In each figure, the thick black arrow indicates the direction of the acting force, and the thin arrow indicates the stress generated on the surface on the negative side of the X-axis of each of the displacement parts 61d and 62d (“→ ←” indicates the compressive stress, “← →” indicates tensile stress).

  As shown in FIG. 7A, the first displacement portion 61d of the first detection portion A in the initial state is parallel to the ZY plane. Then, as shown in FIG. 7B, when a compressive force acts on the basic structure 1w, as described above, the posture of the pair of first deformed portions 61e1 and 61e2 changes to a state of lying more horizontally. As a result, as shown in FIG. 7B, the first displacement portion 61d of the first detection portion A bends and deforms so as to project in the negative direction of the X-axis (the right direction in FIG. 7B). . That is, as shown in the drawing, a tensile stress is generated along the Y-axis direction on the surface on the negative side of the X-axis of the first displacement portion 61d where the first strain gauge R1 is disposed. On the other hand, as shown in FIG. 7C, when a tensile force acts on the basic structure 1w, as described above, the posture of the pair of first deformed portions 61e1 and 61e2 changes to a more vertically standing state. As a result, as shown in FIG. 7C, the first displacement portion 61d of the first detection portion A is bent and deformed so as to be convex in the X-axis positive direction (left direction in FIG. 7C). . That is, as shown in the drawing, a compressive stress is generated along the Y-axis direction on the surface on the X-axis negative side of the first displacement portion 61d where the first strain gauge R1 is disposed. As a result, the direction of the force (compression or tension) acting on the first detection portion A1 and the direction of the stress (compression or tension) generated on the negative surface of the first displacement portion 61d on the X-axis side are opposite to each other. . As understood from the modes of the bending deformation in FIGS. 7B and 7C, the direction of the stress (compression or tension) generated on the surface on the X-axis positive side of the first displacement portion 61d is as follows. The direction of the force (compression or tension) acting on the first detection site A1 is the same.

  Although the second detection portion B is not shown in FIG. 7, a similar bending deformation occurs in the second displacement portion 62d also in the second detection portion B. However, as described above, since the second detection portion has a relatively smaller spring constant than the first detection portion A, the stress generated in the first displacement portion 61d is applied to the second displacement portion 62d. Greater than the stresses that occur. From this, it is possible to provide a force sensor 1s capable of detecting a force with high accuracy and high sensitivity by detecting the force Fy applied by using the first strain gauge disposed on the first displacement portion 61d. Can be.

  As described above, according to the present embodiment, the force sensors 1c and 1s capable of detecting force with high accuracy and high sensitivity regardless of whether they are configured as a capacitance type or a strain gauge type are provided. can do.

  Further, since the first detection part A and the second detection part B are arranged in parallel between the movable part 20 and the fixed part 10, the first detection part A and the second detection part B are greatly deformed or displaced. Can be generated, and the applied force can be detected with higher accuracy and higher sensitivity.

  Further, the first detection site A of the basic structure 1 shown in FIG. 1 has a shape along a part of an arc having a predetermined radius, and the second detection site B has a radius different from the predetermined radius. It has a shape along a part of the circular arc. For this reason, displacement can be generated in the first detection portion A and the second detection portion B in a direction orthogonal to the applied force, and the measurement of the force is easy. The same applies to the basic structure 1w shown in FIG.

<<<< §2. Force sensor according to second embodiment of the present invention >>>
Next, a force sensor according to a second embodiment of the present invention will be described in detail.

<2-1. Basic structure>
FIG. 8 is a schematic top view showing the basic structure 101 of the force sensor according to the second embodiment of the present invention, and FIG. 9 shows that a moment around the Z axis acts on the movable part 120 as a force receiving body. FIG. 10 is a schematic top view showing the basic structure 101 of FIG. 8 at the time, and FIG. 10 is a schematic top view showing a second quadrant portion of the basic structure 101 of FIG.

  The force sensor according to the present embodiment detects at least one of a force in each axis direction and a moment around each axis in the XYZ three-dimensional coordinate system. As shown in FIGS. 8 to 10, the basic structure 101 includes a fixed part 110 fixed with respect to the XYZ three-dimensional coordinate system, and a movable part 120 relatively moved with respect to the fixed part 110 by the action of force or moment. And a deformable body 140 that is connected to the fixed part 110 and the movable part 120, and that is elastically deformed when the movable part 120 relatively moves with respect to the fixed part 110.

  As shown in FIGS. 8 to 10, the fixing portion 110 is fixed on the XY plane, and has a disk shape centered on the origin when viewed from the positive direction of the Z axis. The movable section 120 has an annular shape that is arranged concentrically with the fixed section 110 on the XY plane when viewed from the positive direction of the Z axis. Note that the fixing portion 110 may also have an annular shape.

  Further, as shown in FIGS. 8 to 10, the deformable body 140 is arranged so as to surround the first deformable body 141 in the shape of an annular ring made of an elastic body, and the elastic body , And a second deformable body 142 having a ring shape. When viewed from the positive direction of the Z-axis, the first deformable body 141 is disposed concentrically with the fixed part 110 so as to surround the fixed part 110, and the second deformable body 142 is formed between the first deformable body 141 and the movable part 120. Concentrically arranged with them in between. As a result, the fixed part 110, the first deformable body 141, the second deformable body 142, and the movable part 120 are arranged concentrically with each other and in this order radially outward as viewed from the positive direction of the Z axis. I have.

  In addition, the first deformable body 141 and the second deformable body 142 of the basic structure 101 according to the present embodiment have the same cross-sectional shape. For this reason, the spring constant of each detection part A1 to A4 of the first deformation body 141 is larger than the spring constant of each detection part B1 to B4 of the second deformation body due to the difference in diameter of each of the deformation bodies 141 and 142. Here, the spring constant of each of the detection parts A1 to A4 and B1 to B4 is the displacement of the detection parts 1 to A4 and B1 to B4 in the V-axis direction and the W-axis direction which is applied to the movable part 20. Means the divided value.

  As shown in FIGS. 8 to 10, the fixed part 110 and the first deformable body 141 are connected to each other by a connecting body 133 arranged on the positive Y axis and a connecting body arranged on the negative Y axis in a gap between each other. 137 are connected to each other. Further, the first deformed member 141 and the second deformed member 142 are connected to each other by a connecting member 134 disposed on the positive Y axis and a connecting member 138 disposed on the negative Y axis in a gap between each other. Have been. As a result, in the first deformable body 141 and the second deformable body 142, each of the two portions located on the Y axis does not relatively move with respect to the fixed portion 110.

  Further, as shown in FIGS. 8 to 10, the first deformable body 141 and the second deformable body 142 are disposed on the positive X axis in the gap between each other, and are disposed on the negative X axis. Are connected to each other by the connected body 135. Further, the movable portion 120 and the second deformable member 142 are connected to each other by a connecting member 132 disposed on the positive X axis and a connecting member 136 disposed on the negative X axis in a gap between each other. I have. As a result, in the first deformable body 141 and the second deformable body 142, each of the two portions located on the X axis moves relative to the fixed portion 110 integrally with the movable portion 120. .

  Next, the operation of the basic structure 101 when a moment −Mz around the Z axis acts on the movable portion 120 of the basic structure 101 will be described with reference to FIG. In FIG. 9, thick black arrows indicate the direction of the acting force, and thick white arrows indicate the directions of displacement of the detection parts A1 to A4 and B1 to B4.

  As shown in FIG. 9, when the movable portion 120 is rotated clockwise relative to the fixed portion 110 by the action of the moment −Mz, the first and second deformable bodies 141 and 142 are rotated. The portion on the positive X-axis connected by the connectors 131 and 132 is in the negative Y-axis direction (downward in FIG. 9), and the portion on the negative X-axis connected by the connectors 135 and 136 is They move in the positive Y-axis direction (upward in FIG. 9). On the other hand, of the first and second deformed bodies 141 and 142, the parts on the Y axis connected by the connected bodies 133, 134, 137 and 138 do not move. As a result, the following elastic deformation occurs in each of the deformable bodies 141 and 142. In other words, when the V axis and the W axis passing through the origin O and forming 45 ° with respect to the X axis and the Y axis are defined on the XY plane, the portions of the deformable bodies 141 and 142 that are located on the W axis , A radial outward displacement occurs, and a radially inward displacement occurs at a portion located on the V-axis. On the other hand, although not shown, when a force in the opposite direction acts on the movable unit 120 and the movable unit 120 is rotated counterclockwise relative to the fixed unit 110, at a position located on the W axis, Displacement occurs radially inward, and displacement occurs radially outward at a portion located on the V-axis.

  Since these displacements are maximum on the W axis and the V axis, pay attention to the displacement or stress at a portion of each of the deformable bodies 141 and 142 that intersects the W axis and the V axis when viewed from the positive Z axis direction. It is efficient to measure the force or moment that is applied. Therefore, here, as shown in FIG. 9, four portions of the first deformed body 141 that intersect with the W axis and the V axis are arranged in the order from the first quadrant to the 1-1 detection portion A1 and the 1-2 detection portion. A2, the first to third detection sites A3 and the first to fourth detection sites A4, and four portions of the second deformed body 142 that intersect with the W axis and the V axis are sequentially referred to as a 2-1 detection site B1, A 2-2 detection site B2, a 3-3 detection site B3, and a 2-4 detection site B4.

  Here, the relationship between the basic structure 101 according to the present embodiment and the basic structure 1 according to the first embodiment will be described with reference to FIG.

  As described above, in the basic structure 101 according to the present embodiment, a portion of the deformable bodies 141 and 142 located on the positive Y axis is fixed with respect to the XYZ three-dimensional coordinate system. , 142 located on the negative X axis move together with the movable unit 120 relative to the fixed unit 110. In such a structure, the portion of each of the deformable bodies 141 and 142 located on the positive Y axis is regarded as the fixing portion 10 of the basic structure 1 according to the first embodiment, and the negative X of each of the deformable bodies 141 and 142 is By treating the portion located on the axis as the movable portion 20 of the basic structure 1 according to the first embodiment, the structure shown in FIG. 10 and the basic structure 1 according to the first embodiment have substantially the same structure. It is understood that there is. The same holds for the first, third and fourth quadrants. Furthermore, the relationship between the spring constants of the respective deformable bodies 141 and 142 is such that the spring constant of the first detection portion A of the first deformable body 31 is the second constant of the second deformable body 32 in the basic structure 1 in the first embodiment. This also corresponds to being larger than the spring constant of the detection site B.

  After all, it can be said that the basic structure 101 shown in FIGS. 8 and 9 is a combination of four basic structures 1 according to the first embodiment. That is, as described in the first embodiment, the basic structure 101 according to the present embodiment has a larger displacement than the first to fourth detection portions A1 to A4 in terms of displacement. The 2-4 detection sites B1 to B4 have higher sensitivity, and the stresses are more sensitive to the 1-1 to 1-4 detection sites A1 to A4 than the 2-1 to 2-4 detection sites B1 to B4. Has the characteristic that it has higher sensitivity.

<2-2. Capacitive force sensor>
Next, a capacitance type force sensor 101c using the above basic structure 101 will be described.

  FIG. 11 is a schematic top view showing a capacitance type force sensor 101c having the basic structure 101 of FIG. As shown in FIG. 11, the force sensor 101c includes first to first to fourth displacement electrodes Em11 to Em14 arranged on the outer surfaces of the first to first to fourth detection portions A1 to A4. 1-1 to 1-4 fixed electrodes Ef11 to Ef14 which are arranged to face the displacement electrodes Em11 to Em14 and do not relatively move with respect to the fixed portion 110, and 2-1 to 2-4 detection sites B1 to The 2-1 to 2-4 displacement electrodes Em21 to Em24 disposed on the outer surface of B4 and the 2-1 to 2-4 displacement electrodes Em21 to Em24 which are disposed to face the displacement electrodes Em21 to Em24 and do not relatively move with respect to the fixed portion 110. 2-4 fixed electrodes Ef21 to Ef24.

  As shown in FIG. 11, the 1-1 displacement electrode Em11 and the 1-1 fixed electrode Ef11 form a 1-1 capacitance element C11, and the 1-2 displacement electrode Em12 and the 1-2 fixed electrode Ef12. Constitutes a 1-2 capacitance element C12, the 1-3 displacement electrode Em13 and the 1-3 fixed electrode Ef13 constitute a 1-3 capacitance element C13, and a 1-4 displacement electrode Em14 and a The 1-4 fixed electrode Ef14 forms a 1-4 capacitance element C14. Further, the 2-1 displacement electrode Em21 and the 2-1 fixed electrode Ef21 form a 2-1 capacitive element C21, and the 2-2 displacement electrode Em22 and the 2-2 fixed electrode Ef22 form the The second capacitance element C22 is formed, and the second to third displacement electrodes Em23 and the second to third fixed electrodes Ef23 form the second to third capacitance elements C23. The second to fourth displacement electrodes Em24 and the second to fourth fixed electrodes are formed. Ef24 forms the second-fourth capacitive element C24. Each of the fixed electrodes Ef11 to Ef24 is connected to the first and second deformable bodies 141 and 142 even when a force is applied to the movable section 120 by a support (not shown) fixed to the XY plane and extending in the positive Z-axis direction. It is supported at a position where it does not interfere.

  In the present embodiment, the 1-1 to 1-4 displacement electrodes Em11 to Em14 and the 2-1 to 2-4 displacement electrodes Em21 to Em24 all have the same area. Furthermore, the 1-1 to 1-4 fixed electrodes Ef11 to Ef14 and the 2-1 to 2-4 fixed electrodes Ef21 to Ef24 all have the same area. Further, the effective facing area of each electrode constituting each of the capacitive elements C11 to C24 and the distance between the facing electrodes are all the same.

  Further, as shown in FIG. 11, the force sensor 101c outputs an electric signal indicating the force or moment acting on the movable portion 120 based on the elastic deformation generated in the first deformable member 141 and the second deformable member 142. It has a detection circuit 150. The detection circuit 150 of the force sensor 101c shown in FIG. 11 outputs an electric signal indicating the force or moment applied to the movable unit 120 based on the amount of change in the capacitance value of each of the capacitance elements C11 to C24. Has become. In addition, the wiring which electrically connects each of the capacitance elements C11 to C24 and the detection circuit 150 is not shown.

  Next, the operation of the force sensor 101c will be described.

  Here, a case where a clockwise force (moment) acts on the movable unit 120 when viewed from the positive direction of the Z axis will be described as an example (see FIG. 9). In this case, as described above, among the deformed bodies 141 and 142, the 1-2, 2-2, 1-4, and 2-4 detection sites A2, B2, A4, In B4, displacement occurs in the radially outward direction, and in the 1-1, 2-1, 1-3, and 2-3 detection sites A1, B1, A3, and B3 located on the V axis. , Radially inward displacement occurs. As a result, the capacitance values of the 1-2, 2-2, 1-4, and 2-4 capacitive elements C12, C22, C14, and C24 increase because the distance between the electrodes decreases. On the other hand, the capacitance values of the 1-1, 2-1, 1-3, and 2-3 capacitance elements C11, C21, C13, and C23 decrease because the distance between the electrodes increases. .

  In the present embodiment, as described above, since the spring constant of each of the detection portions B1 to B4 of the second deformable member 142 is smaller than the spring constant of each of the detection portions A1 to A4 of the first deformable member 141, Focusing on the absolute value of the amount of change in the capacitance value, the amount of change in the capacitance value of each of the 2-1 to 2-4 capacitive elements C21 to C24 disposed on the second deformable body 142 is equal to that of the first deformable body. It is larger than the amount of change in the capacitance value of the first to first to fourth to fourth capacitance elements C11 to C14 arranged on the 141.

Then, the detection circuit 150 measures the applied moment Mz around the Z axis using the following [Equation 1]. In [Equation 1], Mz1 is a moment about the Z axis measured based on the elastic deformation of the first deformable body 141, and Mz2 is a moment around the Z axis measured based on the elastic deformation of the second deformable body 142. Is the moment. In the following formulas, C11 to C24 indicate the amounts of change in the capacitance values of the first to second to fourth capacitance elements C11 to C24. This is the same in the other expressions in this specification.
[Equation 1]
-Mz1 = -C11 + C12-C13 + C14
-Mz2 = -C21 + C22-C23 + C24

  In the capacitance type force sensor 101c, based on the amount of change in the capacitance values of the 2-1 to 2-4 capacitance elements C21 to C24, which are relatively highly sensitive, that is, [Equation 1] By measuring the applied moment based on -Mz2, it is possible to perform a measurement excellent in S / N. Of course, the applied moment may be measured based on the amount of change in the capacitance values of the first to first to fourth to fourth capacitance elements C11 to C14. If only the moment Mz around the Z axis is measured, only one of the first to fourth capacitance elements C11 to C14 and the second to fourth capacitance elements C21 to C24 is provided. It is good if it is done.

<2-3. Strain gauge type force sensor>
The basic structure 101 as described above can also be used for a strain gauge type force sensor 101s.

  FIG. 12 is a schematic top view showing a strain gauge type force sensor 101s having the basic structure 101 of FIG. As shown in FIG. 12, the force sensor 101 s includes, on the outer surface of the first annular deformable body 141, a 1-1 strain gauge R <b> 11 disposed at the 1-1 detection site A <b> 1 and a 1-2 detection site. A1-2 strain gauge R12 arranged at A2, a 1-3 strain gauge R13 arranged at the 1-3 detection site A3, and a 1-4 strain gauge arranged at the 1-4 detection site A4. And a gauge R14. Further, the force sensor 101s is arranged on the outer surface of the annular second deformable body 142 at the 2-1 strain gauge R21 disposed at the 2-1 detection site B1 and at the 2-2 detection site B2. A 2-2 strain gauge R22, a 2-3 strain gauge R23 disposed at the 2-3 detection site B3, and a 2-4 strain gauge R24 disposed at the 2-4 detection site B4. Have. Each of the strain gauges R11 to R24 is a metal foil strain gauge, and all have the same characteristics. The other configuration is the same as that of the force sensor 1c shown in FIG. 11 except that it does not have a capacitive element, and thus a detailed description thereof is omitted.

  Next, the operation of the force sensor 101s will be described.

  Here, a case where a clockwise force (moment) acts on the movable unit 120 when viewed from the positive direction of the Z axis will be described as an example (see FIG. 9). In this case, as described above, among the deformed bodies 141 and 142, the 1-2, 2-2, 1-4, and 2-4 detection sites A2, B2, A4, In B4, displacement occurs in the radially outward direction, and in the 1-1, 2-1, 1-3, and 2-3 detection sites A1, B1, A3, and B3 located on the V axis. , Radially inward displacement occurs. As a result, tensile stress is generated at the 1-2, 2-2, 1-4, and 2-4 detection sites A2, B2, A4, and B4 located on the W axis, and the detection sites are located on the V axis. The first, second, first, third, and second detection sites A1, B1, A3, and B3 generate compressive stress. As described above, the spring constant of each of the detection portions A1 to A4 of the first deformable member 141 is larger than the spring constant of each of the detection portions B11 to B14 of the second deformable member 142. The absolute value of the stress generated at the detection portions A1 to A4 is larger than the absolute value of the stress generated at each of the detection portions B1 to B4 of the second deformable body 142. For this reason, the electrical resistance values of the 1-1 to 1-4 strain gauges R11 to R14 fluctuate more greatly than the electrical resistance values of the 2-1 to 2-4 strain gauges R21 to R24.

Then, the detection circuit 150 uses, for example, the following [Equation 2] and, for example, at least one of the 1-1 to 1-4 strain gauges R11 to R14 and the 2-1 to 2-4 strain gauges R21 to R24. The applied moment Mz around the Z-axis is measured based on the variation of the electric resistance value. In [Equation 2], Mz1 is a moment around the Z axis measured based on the elastic deformation of the first deformable body 141, and Mz2 is a moment around the Z axis measured based on the elastic deformation of the second deformable body 142. Is the moment. Further, in the following equations, R11 to R24 indicate the amount of change in the electric resistance value of the first to second to fourth strain gauges R11 to R24. This is the same in the other expressions in this specification.
[Equation 2]
-Mz1 = -R11 + R12-R13 + R14
-Mz2 = -R21 + R22-R23 + R24

  In the strain gauge type force sensor 101c, based on the fluctuation amounts of the electrical resistance values of the first to the first to fourth strain gauges R11 to R14, which are relatively highly sensitive, that is,-of [Expression 2]. By measuring the applied moment based on Mz1, measurement excellent in S / N becomes possible. Of course, the moment acting on the basis of the variation of the electric resistance value of the second to second to fourth strain gauges R21 to R24 may be measured. In the measurement, the first to the first to fourth strain gauges R11 to R14 or the 2-1 to the second to fourth strain gauges R21 to R24 acted by forming a Wheatstone bridge circuit (not shown). It is also possible to measure the moment. If only the moment Mz around the Z axis is measured, only one of the first to first to fourth strain gauges R11 to R14 and the second to second to fourth strain gauges R21 to R24 is provided. It is good if it is done.

  According to the above-described force sensor according to the present embodiment, the capacitance is set in the 2-1 to 2-4 detection portions B1 to B4 where the spring constant is relatively small, that is, the generated elastic deformation is relatively large. By disposing the elements C21 to C24, it is possible to provide the force sensor 101c capable of detecting a moment with high accuracy and high sensitivity. Furthermore, by disposing the strain gauges R11 to R14 at the first to first to fourth detection portions A1 to A4 where the spring constant is relatively large, that is, the stress generated due to the elastic deformation is relatively large. Thus, it is possible to provide the force sensor 101s that can detect a moment with high accuracy and high sensitivity. As described above, according to the present embodiment, the force sensors 101c and 101s capable of detecting force with high accuracy and high sensitivity regardless of whether they are configured as a capacitance type or a strain gauge type are provided. can do.

  In the above-described force sensors 101c and 101s, the first deformable body 141 and the second deformable body 142 are both annular and concentric with each other. Therefore, the force sensors 101c and 101s can be configured with a simple configuration.

  Further, the first deformation body 141 has first to first to fourth detection parts A1 to A4 at four parts overlapping the V axis and the W axis when viewed from the Z axis direction, and the second deformation body 142 , And two to two detection parts B1 to B4 at four parts overlapping the V axis and the W axis when viewed from the Z axis direction. For this reason, symmetrical elastic deformation occurs in the first deformable body 141 and the second deformable body 142 due to the applied moment, so that there is no influence of a force other than the applied moment.

<2-4. Modified example of basic structure>
Next, a modified example of the above basic structure 101 will be described. FIG. 13 is a schematic top view showing a first modification of the basic structure 101 of FIG. 8, and FIG. 14 is a schematic top view showing a second modification of the basic structure 101 of FIG. FIG. 10 is a schematic top view showing a third modification of the basic structure 101 in FIG.

  First, a basic structure 101a according to a modification shown in FIG. 13 will be described. The basic structure 101a is different from the above-described basic structure 101 in that a thin portion having a small thickness is provided in an annular second deformable body 142. Specifically, the second deformable body 142 has 2-1 to 2-4 thin portions 142t1 to 142t4 in a region including portions located on the V axis and the W axis. Therefore, the 2-1 to 2-4 detection parts B1 to B4 are provided in the 2-1 to 2-4 thin portions 142t1 to 142t4, respectively. On the other hand, the first modified body 141 is the same as the first modified body 141 of the basic structure 101 shown in FIGS.

  In the present modification, as shown in FIG. 13, each of the thin portions 142t1 to 142t4 is formed by making the radial thickness of the second deformable body 142 thin. Of course, in another modified example, the second modified body 142 may be formed by making the thickness in the Z-axis direction thin. The other configurations are the same as those of the basic structure 101 shown in FIGS. 8 to 10, and the corresponding components are denoted by the same reference numerals and detailed description thereof will be omitted.

  When a clockwise (for example, the same direction as in FIG. 9) moment acting on the basic structure 101a having such a configuration as viewed from the positive direction of the Z-axis acts on each of the deformed bodies 141 and 142, the same elasticity as in FIG. Deformation occurs. However, the elastic deformation generated in the thin portions 142t1 to 142t4 of the second deformable body 142 is larger than in the case of FIG.

  According to the basic structure 101a having such a configuration, the spring constants of the 2-1 to 2-4 detection portions B1 to B4 are relatively reduced due to the presence of the thin portions 142t1 to 142t4. Therefore, when the basic structure 101a is used as a capacitance-type force sensor, it is provided at the 2-1 to 2-4 detection sites B1 to B4 as compared with the basic structure 101 described above. In the capacitive element, a particularly large amount of variation in the capacitance value is observed. That is, in the force sensor of the capacitance type, the force or moment acting on the basis of the fluctuation amount of the capacitance value of the 2-1 to 2-4 capacitance elements C21 to C24, which are relatively sensitive. , It is possible to perform measurement with even better S / N. Of course, the force acting on the basis of the amount of change in the capacitance value of the first to first to fourth to fourth capacitance elements C11 to C14 may be measured.

  A further modified example of the basic structure in which the deformed body having such thin portions 142t1 to 142t4 is provided will be described with reference to FIG.

  The basic structure 101b shown in FIG. 14 is different from the basic structure 101a according to the first modification in that the second deformed body 142b is divided into four parts by the X axis and the Y axis. That is, the second deformed body 142b includes a 2-1 deformed body 142b1 arranged in the first quadrant on the XY plane, a 2-2 deformed body 142b2 arranged in the second quadrant on the XY plane, and It has a 2-3 modified body 142b3 arranged in the third quadrant and a 2-4 modified body 142b4 arranged in the fourth quadrant on the XY plane. As shown in FIG. 14, the 2-1 modified body 142b1 has a portion near the positive Y axis connected to the first deformable body 141 by a connector 134a extending in parallel with the Y axis, and has a portion near the positive X axis. Are connected to the movable part 120 by a connector 132b extending in parallel with the X axis. Further, the 2-2 deformation body 142b2 has a portion near the positive Y axis connected to the first deformation body 141 by a connecting body 134b extending parallel to the Y axis, and a portion near the negative X axis has an X axis. Are connected to the movable part 120 by a connecting body 136a extending in parallel with the movable part 120. The second to third deformed bodies 142b3 are connected to the first deformed body 141 by a connecting body 136b that extends in the vicinity of the negative X axis in parallel with the X axis, and the parts in the vicinity of the negative Y axis are parallel to the Y axis. Are connected to the movable part 120 by a connecting body 138a extending to the movable part 120. The second to fourth deformed bodies 142b4 are connected to the first deformed body 141 by a connecting body 138b that extends in the vicinity of the negative Y axis in parallel with the Y axis, and the parts in the vicinity of the positive X axis are parallel to the X axis. Are connected to the movable section 120 by a connecting body 132a extending to the movable section 120.

  Further, as shown in FIG. 14, the two connecting members 132a and 132b extending in parallel with the X axis are separated from each other in the Y axis direction, and a second connecting member 132a and 132b is provided between the two connecting members 132a and 132b. A connecting body 131l that connects the first deformable body 141 and the movable part 120 extends along the X axis. Similarly, two connecting members 136a and 136b extending in parallel with the X axis are separated from each other in the Y axis direction, and a first deformed member is provided between the two connecting members 136a and 136b. A connecting body 135l connecting the 141 and the movable part 120 extends along the X-axis. The other configuration is the same as that of the first modified example shown in FIG. 14, and therefore, the same components are denoted by the same reference numerals, and detailed description thereof will be omitted.

  When a clockwise (in the same direction as in FIG. 9) moment acts on the basic structure 101b having such a configuration, for example, as viewed from the positive direction of the Z axis, the deformable bodies 141 and 142 have the same elasticity as in FIG. Deformation occurs. However, the elastic deformation that occurs in the thin portions 142t1 to 142t4 of the second deformable body 142 is the same as the basic structure 101a according to the first modified example shown in FIG. 13 and is larger than that in FIG.

  Next, a third modified example of the basic structure in which the deformed body having the thin portions 142t1 to 142t4 is provided will be described with reference to FIG. The basic structure 101b ′ according to the third modified example is different from the basic structure 101b ′ shown in FIG. 14 in that the 2-1 to 2-4 modified bodies 142b1 to 142b4 are not directly connected to the movable section 120. This is different from the basic structure 101b according to the modification. That is, as shown in FIG. 15, in the basic structure 101b ′ according to the third modification, the regions near the positive X axis of the 2-1 modified body 142b1 and the 2-4 modified body 142b4 are connected to the coupled bodies 132d and 132e. The regions near the negative X-axis of the 2-2 deformation body 142b2 and the 2-3 deformation body 142b3 are connected to the first deformation body 141 by the connection bodies 136c and 136d, respectively. Are linked. In this modification, none of the 2-1 to 2-4 deformation bodies 142b1 to 142b4 is connected to the movable portion 120, but instead, the connection portion between the connection body 131l and the first deformation body 141 is changed. The ends of the connectors 132d and 132e are connected to the first deformable body 141 in the vicinity, and the ends of the connectors 136c and 136d near the connecting portion between the connector 135l and the first deformable body 141. The part is connected to the first deformable body 141. Therefore, also in this modification, substantially the same operation as the basic structures 101a and 101b shown in FIGS. 13 and 14 is provided.

<2-5. Detection principle of force Fx in X-axis direction and force Fy in Y-axis direction>
In the above description, the method of measuring the moment Mz around the Z axis by the force sensors 101c and 101s has been described. Can also be measured.

  First, a principle for measuring the force + Fx in the positive direction of the X-axis will be described with reference to FIG. FIG. 16 is a diagram for explaining elastic deformation that occurs in the deformable body 140 when a force + Fx in the positive X-axis direction acts on the movable portion 120 of the basic structure 101 in FIG. Since the elastic deformations generated in the first deformable body 141 and the second deformable body 142 are different in degree but the same, only a single deformable body 140 is shown in FIG. 16 for simplicity. . In addition, for simplicity, the illustration of the fixing portion 110 and the connecting body that connects the fixing portion 110 and the deformable body 140 is omitted, but the points P1 and P2 in FIG. Do not move. On the outer surface of the portion of the deformable body 140 that intersects the V axis and the W axis when viewed from the positive direction of the Z axis, four detection sites A, B, C, and D are arranged in this order in a counterclockwise direction from the first quadrant. Is provided. In FIG. 16, thick black arrows indicate the direction of the acting force, and thick white arrows indicate the directions of displacement of the detection parts A to D.

  As shown in FIG. 16, when a force + Fx in the positive X-axis direction acts on the movable portion 120 of the basic structure 101, the portion on the X-axis of the deformable body 140 moves in the positive X-axis direction together with the movable portion 120. On the other hand, the parts on the Y axis corresponding to the points P1 and P2 do not move. From this, of the deformed body 140, of the four detection parts A to D, the detection parts A and D located in the first quadrant and the fourth quadrant are displaced inward in the radial direction of the deformed body 140. The detection portions B and C located in the second and third quadrants are elastically deformed so as to be displaced radially outward of the deformable body 140.

  From the above, the following is understood. That is, when a force + Fx in the positive direction of the X-axis acts on the movable portion 120 of the force sensor 101c shown in FIG. 11, the 1-1 capacitance element C11 and the 2-1 capacitance element C21 arranged in the first quadrant, and The capacitance values of the first to fourth capacitive elements C14 and C24 located in the fourth quadrant decrease because the distance between the fixed electrode and the displacement electrode increases. On the other hand, the 1-2 capacitance element C12 and the 2-2 capacitance element C22 located in the second quadrant, and the 1-3 capacitance element C13 and the 2-3 capacitance element C23 located in the third quadrant, Since the separation distance between the fixed electrode and the displacement electrode decreases, the capacitance value increases.

Therefore, the detection circuit 150 measures the applied force Fx in the X-axis direction using the following [Equation 3]. In [Equation 3], Fx1 is the force in the X-axis direction measured based on the elastic deformation of the first deformable body 141, and Fx2 is the X-axis direction measured based on the elastic deformation of the second deformable body 142. Power.
[Equation 3]
Fx1 = -C11 + C12 + C13-C14
Fx2 = -C21 + C22 + C23-C24

  Next, the principle for measuring the force + Fy in the Y-axis positive direction will be described with reference to FIG. FIG. 17 is a diagram for explaining elastic deformation that occurs in the deformable body 140 when a force + Fy in the Y-axis positive direction acts on the movable portion 120 of the basic structure 101 in FIG. Although the elastic deformations generated in the first deformable body 141 and the second deformable body 142 are different in degree but the same, the single deformable body 140 is shown in FIG. 17 for simplicity even in FIG. . In addition, for simplicity, the illustration of the fixing portion 110 and a connecting body that connects the fixing portion 110 and the deformable body 140 is omitted, but the points P1 and P2 in FIG. Do not move. In the deformed body 140, four detection portions A, B, C, and D are provided in the order intersecting the V axis and the W axis as viewed in the positive Z axis direction from the first quadrant in a counterclockwise direction. Have been. In FIG. 17, the thick black arrows indicate the direction of the acting force, and the thick white arrows indicate the directions of displacement of the detection parts A to D.

  As shown in FIG. 17, when a force + Fy in the positive direction of the Y axis acts on the movable portion 120 of the basic structure 101, the portion on the X axis of the deformable body 140 moves in the positive direction of the Y axis together with the movable portion 120. On the other hand, the parts on the Y axis corresponding to the points P1 and P2 do not move. From this, in the deformed body 140, of the four detection sites A to D, the detection sites A and B located in the first quadrant and the second quadrant move radially outward of the deformed body 140, and on the other hand, The detection portions C and D located in the third and fourth quadrants are elastically deformed so as to move radially inward of the deformable body 140.

  From the above, the following is understood. That is, when a force + Fy in the positive direction of the Y-axis acts on the movable portion 120 of the force sensor 101c shown in FIG. 11, the 1-1-th capacitive element C11 and the 2-1-th capacitive element C21 located in the first quadrant, and The capacitance values of the first to second capacitance elements C12 and C22 located in the second quadrant increase because the distance between the fixed electrode and the displacement electrode decreases. On the other hand, the first to third capacitive elements C13 and C23 located in the third quadrant, and the first to fourth capacitive elements C14 and C24 located in the fourth quadrant are: Since the distance between the fixed electrode and the displacement electrode increases, the capacitance value decreases.

Therefore, the detection circuit 150 measures the applied force Fy in the Y-axis direction using the following [Equation 4]. In [Equation 4], Fy1 is a force in the Y-axis direction measured based on the elastic deformation of the first deformable body 141, and Fy2 is a Y-axis direction measured based on the elastic deformation of the second deformable body 142. Power.
[Equation 4]
Fy1 = C11 + C12-C13-C14
Fy2 = C21 + C22-C23-C24

  As described above, in the capacitance-type force sensor 101c, based on the fluctuation amounts of the capacitance values of the 2-1 to 2-4 capacitance elements C21 to C24, which are relatively highly sensitive. That is, when obtaining the force Fx in the X-axis direction, the applied force is measured based on Fx2 in [Equation 3], and when obtaining the force Fy in the Y-axis direction, based on Fy2 in [Equation 4]. Thereby, measurement excellent in S / N becomes possible. Of course, the applied force may be measured based on the amount of change in the capacitance value of the first to first to fourth to fourth capacitance elements C11 to C14.

  Here, the force sensor 101c provided with a total of eight capacitive elements of the first to first to fourth capacitive elements C11 to C14 and the second to second to fourth capacitive elements C21 to C24 will be described as an example. Was done. However, if only the force Fx in the X-axis direction and / or the force Fy in the Y-axis direction are measured, the first to first to fourth capacitance elements C11 to C14 and the second to second to fourth capacitances are used. It is sufficient that only one of the elements C21 to C24 is provided.

  When the direction of the acting force is the negative direction of the X axis, the fluctuations of the capacitance values of the respective capacitance elements C11 to C24 are all reversed. Therefore, the signs of the forces Fx1 and Fx2 measured by [Equation 3] are both opposite. That is, the direction (sign) and magnitude of the applied force Fx are measured by [Equation 3]. This is the same when measuring the force Fy in the Y-axis direction using [Equation 4].

  Next, a method of measuring a force in the X-axis direction by the strain gauge type force sensor 101s will be described with reference to FIG.

  FIG. 18 is a diagram for explaining stresses generated at the detection parts A to D of the deformable body 140 when a force in the positive direction of the X-axis acts on the movable part 120 of the basic structure 101 in FIG. Since the elastic deformations generated in the first deformable body 141 and the second deformable body 142 are different in degree but the same, only a single deformable body 140 is shown in FIG. 18 for simplicity. . The arrangement of the detection sites A to D is the same as in FIGS. In FIG. 18, the thick black arrows indicate the direction of the acting force, and the thin arrows indicate the stress (“→ ←” indicates a compressive stress, and “← →” indicates a tensile stress) at each of the detection sites A to D. ).

  As shown in FIG. 18, when a force + Fx in the positive direction of the X-axis acts on the movable portion 120 of the basic structure 101, the deformable body 140 is elastically deformed as in FIG. At this time, focusing on the change in the radius of curvature at each of the detection sites A to D, as shown in FIG. 18, the detection sites A and D located in the first quadrant and the fourth quadrant bend so that the radius of curvature becomes large. On the other hand, the detection portions B and C located in the second and third quadrants are bent so as to have a small radius of curvature. Due to such bending deformation, compressive stress is generated in the detection portions A and D located in the first and fourth quadrants, and is detected in the detection portions B and C located in the second and third quadrants. , Tensile stress occurs.

  From the above, the following is understood. That is, when a force + Fx in the positive direction of the X axis acts on the movable portion 120 of the force sensor 101s shown in FIG. 12, the 1-1 strain gauge R11 and the 2-1 strain gauge R21 arranged in the first quadrant, and The electrical resistance of the first to fourth strain gauges R14 and R24 located in the fourth quadrant decreases due to compressive stress. On the other hand, the 1-2 strain gauge R12 and the 2-2 strain gauge R22 arranged in the second quadrant, and the 1-3 strain gauge R13 and the 2-3 strain gauge R23 located in the third quadrant are: The electric resistance increases due to the tensile stress.

Therefore, the detection circuit 150 measures the applied force Fx in the X-axis direction using the following [Equation 5]. In [Equation 5], Fx1 is the force in the X-axis direction measured based on the elastic deformation of the first deformable body 141, and Fx2 is the X-axis direction measured based on the elastic deformation of the second deformable body 142. Power.
[Equation 5]
Fx1 = -R11 + R12 + R13-R14
Fx2 = -R21 + R22 + R23-R24

  Next, the principle for measuring the force + Fy in the Y-axis positive direction will be described with reference to FIG. FIG. 19 is a diagram for explaining the stress generated in the deformation unit detection unit 140 when a force + Fy in the positive Y-axis direction acts on the movable unit of the basic structure 101 in FIG. 8. Since the degree of elastic deformation generated in the first deformable body 141 and the second deformable body 142 is different but the same, the single deformable body 140 is shown only in FIG. 19 for simplicity in FIG. . In addition, for simplicity, the illustration of the fixing portion 110 and the connecting body that connects the fixing portion 110 and the deformable body 140 is omitted, but the points P1 and P2 in FIG. Do not move. The arrangement of the detection sites A to D is the same as in FIGS. In FIG. 19, the thick black arrows indicate the direction of the acting force, and the thin arrows indicate the stress generated at each of the detection sites A to D (“→ ←” indicates a compressive stress, and “← →” indicates a tensile stress. ).

  As shown in FIG. 19, when a force + Fy in the Y-axis positive direction acts on the movable portion 120 of the basic structure 101, the deformable body 140 is elastically deformed as in FIG. At this time, focusing on the change in the radius of curvature at each of the detection sites A to D, as shown in FIG. 19, the detection sites A and B located in the first quadrant and the second quadrant bend so that the radius of curvature becomes small. On the other hand, the detection portions C and D located in the third and fourth quadrants are bent so as to increase the radius of curvature. Due to such bending deformation, tensile stress is generated in the detection sites A and B located in the first and second quadrants, and is detected in the detection sites C and D located in the third and fourth quadrants. Compressive stress occurs.

  From the above, the following is understood. That is, when a force + Fy in the positive Y-axis direction acts on the movable portion 120 of the force sensor 101s shown in FIG. 12, the 1-1 strain gauge R11 and the 2-1 strain gauge R21 arranged in the first quadrant, and The electrical resistance of the 1-2 strain gauge R12 and the 2-2 strain gauge R22 located in the second quadrant increases due to tensile stress. On the other hand, the 1-3 strain gauge R13 and the 2-3 strain gauge R23 arranged in the third quadrant, and the 1-4 strain gauge R14 and the 2-4 strain gauge R24 located in the fourth quadrant are: The electric resistance decreases due to the compressive stress.

Therefore, the detection circuit 150 measures the applied force Fy in the Y-axis direction using the following [Equation 6]. In [Equation 6], Fy1 is a force in the Y-axis direction measured based on the elastic deformation of the first deformable body 141, and Fy2 is a Y-axis direction measured based on the elastic deformation of the second deformable body 142. Power.
[Equation 6]
Fy1 = R11 + R12-R13-R14
Fy2 = R21 + R22-R23-R24

  In the strain gauge type force sensor 101s, the applied force is measured based on the variation of the electric resistance value of the first to the first to fourth strain gauges R11 to R14, which are relatively sensitive. Thereby, measurement excellent in S / N becomes possible. Of course, the applied force may be measured based on the amount of change in the electric resistance of each of the 2-1 to 2-4 strain gauges R21 to R24.

  Here, the force sensor 101s provided with a total of eight strain gauges of the first to first to fourth strain gauges R11 to R14 and the second to second to fourth strain gauges R21 to R24 will be described as an example. Was done. However, if only the force Fx in the X-axis direction and / or the force Fy in the Y-axis direction are measured, the 1-1 to 1-4 strain gauges R11 to R14 and the 2-1 to 2-4 strain gauges are used. It is sufficient that only one of the gauges R21 to R24 is provided.

  When the direction of the acting force is the negative direction of the X-axis or the negative direction of the Y-axis, the variation amounts of the electric resistances of the respective strain gauges R11 to R24 are all reversed. Therefore, the signs of the forces Fx1 and Fx2 measured by [Equation 5] are both opposite. That is, the direction (sign) and magnitude of the applied force are measured by [Equation 5]. This is the same when measuring the force in the Y-axis direction using [Equation 6].

  In the strain gauge type force sensor 101 s described above, each of the strain gauges R <b> 11 to R <b> 24 may be disposed on the radially inner surface of the deformable bodies 141 and 142 on the V axis and the W axis. In this case, the electric resistance value of each of the strain gauges R11 to R24, and the electric resistance value due to the force acting on the movable portion 120 when each of the strain gauges R11 to R24 is disposed on the radially outer surface of the deformable body 141 or 142. A change opposite to the change occurs. Therefore, by inverting the sign on the right or left side of [Equation 5] and [Equation 6] described above, it is possible to measure the direction (sign) and magnitude of the applied force or moment even in this case. .

<2-5. Basic structure with waveform detection part>
Next, FIG. 20 is a schematic top view showing an annular basic structure 101w in which the structure shown in FIG. 5 is adopted for each of the detection portions A1 to A4 and B1 to B4 of the deformable bodies 141 and 142, and FIG. FIG. 22 is a schematic side view of a 1-1 detection part A1 of the basic structure 101w shown in FIG.

  As shown in FIGS. 20 and 21, each of the detection portions A1 to A4 and B1 to B4 of the basic structure 101w is a detection portion having a downwardly convex waveform having the structure shown in FIG. Each of the detection sites A1 to A4 of the first deformable body 141 has the same structure. Further, each of the detection sites B1 to B4 of the second deformable body 142 has the same structure. On the other hand, each of the detection portions B1 to B4 of the second deformable member 142 is relatively longer in the circumferential direction than each of the detection portions A1 to A4 of the first deformable member 141. Specifically, in the circumferential direction of each of the deformed bodies 141 and 142, the pair of second deformed portions 62e1 and 62e2 of the 2-1 to 2-4 detection parts B1 to B4 are the first to first-first. It is longer than the pair of first deformed portions 61e1 and 61e2 of the four detection portions A1 to A4, and is in a state of lying on the XY plane. Further, in the circumferential direction of each of the deformable bodies 141 and 142, the second displacement portions 62d of the 2-1 to 2-4 detection portions B1 to B4 are connected to the 1-1 to 1-4 detection portions A1 to A4. It is longer than the first displacement portion 61d. With such a configuration, the displacement caused by the action of the force or the moment is relatively larger in the second displacement portion 62d than in the first displacement portion 61d. In other words, the spring constant of the second detection portion B is relatively smaller than the spring constant of the first to first to fourth detection portions A1 to A4. Here, the spring constant means a value obtained by dividing the force acting on the movable portion 20 by the displacement in the Z-axis direction generated at each of the detection portions A1 to A4 and B1 to B4.

  Next, the operation of the basic structure 101w will be described with reference to FIG.

  FIG. 22 shows stresses generated at the detection portions A1 to A4 and B1 to B4 of the deformable bodies 141 and 142 when a moment Mz around the Z axis acts clockwise on the movable portion 120 of the basic structure 101w of FIG. FIG. In FIG. 22, a thick black arrow shown on the movable portion 120 indicates an acting moment −Mz, and a black solid arrow shown in a gap between the first deformable body 141 and the second deformable body 142. Thick arrows indicate the directions of the forces acting on the detection sites A1 to A4 and B1 to B4.

  As shown in FIG. 22, the 1-1 detection site A1 and the 2-1 detection site B1 located in the first quadrant, and the 1-3 detection site A3 and the 2-3 detection detected in the third quadrant are located. A tensile force is generated at the portion B3. On the other hand, the 1-2 detection site A2 and the 2-2 detection site B2 located in the second quadrant and the 1-4 detection site A4 and the 2-4 detection site B4 located in the fourth quadrant include: A compressive force occurs.

  When the basic structure 101w is used as a force sensor of a capacitance type, each of the 1-1 to 1-2 detection sites A1 to A4 and the 2-1 to 2-4 detection sites B1 to B4 What is necessary is just to arrange | position a capacitive element to the displacement parts 61d and 62d. As a specific arrangement method, as shown in FIG. 21, for example, at the 1-1st detection site A1, a displacement electrode Em11 is provided on a displacement portion 61d via a displacement substrate Im11, and faces the displacement electrodes Em11. Thus, the fixed electrode Ef11 may be arranged so as not to move relative to the fixed portion 110. The fixed electrode Ef11 is arranged on the fixed substrate 73 via the fixed substrate If11 (insulator). Such an arrangement is the same in the other displacement parts 61d and 62d. As can be understood from FIG. 21, both the displacement electrode Em11 and the fixed electrode Ef11 employed here have surfaces parallel to the XY plane, and are separated by a predetermined distance in the Z-axis direction. In this manner, a total of eight capacitive elements C11 to C14 and C21 to C24 are configured by the eight sets of the opposing displacement electrodes and fixed electrodes.

  When examining the variation of the capacitance value of each of the capacitance elements C11 to C24 when a clockwise moment −Mz as viewed from the positive direction of the Z-axis acts on such a capacitance type force sensor, the following is considered. It is on the street. That is, the above-described tensile force or compressive force acts on each of the detection portions A1 to A4 and B1 to B4. For this reason, the 1-1 capacitance element C11 and the 2-1 capacitance element C21 arranged in the first quadrant, and the 1-3 capacitance element C13 and the 2-3 capacitance element C23 arranged in the third quadrant. In any case, since the distance between the displacement electrode and the fixed electrode increases, the capacitance value decreases. On the other hand, the 1-2 capacitive element C12 and the 2-2 capacitive element C22 arranged in the second quadrant, and the 1-4 capacitive element C14 and the 2-4 capacitive element C24 arranged in the fourth quadrant, In any case, since the separation distance between the displacement electrode and the fixed electrode decreases, the capacitance value increases.

Therefore, the detection circuit 150 measures the applied moment Mz around the Z axis using the following [Equation 7]. In Equation 7, Mz1 is a moment about the Z axis measured based on the elastic deformation of the first deformable body 141, and Mz2 is a moment around the Z axis measured based on the elastic deformation of the second deformable body 142. Is the moment.
[Equation 7]
-Mz1 = -C11 + C12-C13 + C14
-Mz2 = -C21 + C22-C23 + C24

  As described above, in the capacitance-type force sensor using the basic structure 101w, the fluctuations in the capacitance values of the 2-1 to 2-4 capacitance elements C21 to C24, which are relatively sensitive. By measuring the force acting on the basis of the amount, a measurement excellent in S / N becomes possible. Of course, the applied force may be measured based on the amount of change in the capacitance value of the first to first to fourth to fourth capacitance elements C11 to C14.

  When the direction of the acting moment is reverse (counterclockwise as viewed from the positive direction of the Z axis), the amounts of change in the capacitance values of the respective capacitance elements C11 to C24 are all reversed. Therefore, the signs of the moments Mz1 and Mz2 measured by [Equation 7] are both opposite. That is, the direction and magnitude of the applied moment Mz are measured by [Equation 7].

  Alternatively, when the basic structure 101w is used as a strain gauge type force sensor, the first to the 1-2th detection sites A1 to A4 and the 2-1 to the 2-4th detection sites B1 to B4 are used. Strain gauges R11 to R24 may be arranged in place of the capacitance elements C11 to C24 provided in the displacement parts 61d and 62d, specifically, instead of the displacement electrodes. In this case, the displacement parts 61d and 62d need to be formed of an elastic body.

  When examining the fluctuation of the electric resistance value of each of the strain gauges R11 to R24 when a clockwise moment −Mz acts on such a strain gauge type force sensor as viewed from the positive direction of the Z axis, the following is obtained. is there. That is, the above-described tensile force or compressive force acts on each of the detection portions A1 to A4 and B1 to B4. For this reason, the 1-1 strain gauge R11 and the 2-1 strain gauge R21 arranged in the first quadrant, and the 1-3 strain gauge R13 and the 2-3 strain gauge R23 arranged in the third quadrant. In any case, the electric resistance decreases due to the action of the compressive stress (see FIG. 7C). On the other hand, the 1-2 strain gauge R12 and the 2-2 strain gauge R22 arranged in the second quadrant, and the 1-4 strain gauge R14 and the 2-4 strain gauge R24 arranged in the fourth quadrant In any case, the electric resistance increases due to the action of tensile stress (see FIG. 7B).

Accordingly, the detection circuit 150 measures the applied moment Mz around the Z axis using the following [Equation 8]. In Equation 8, Mz1 is a moment about the Z axis measured based on the elastic deformation of the first deformable body 141, and Mz2 is a moment around the Z axis measured based on the elastic deformation of the second deformable body 142. Is the moment.
[Equation 8]
-Mz1 = -R11 + R12-R13 + R14
-Mz2 = -R21 + R22-R23 + R24

  As described above, in the strain gauge type force sensor using the basic structure 101w, the variation in the electric resistance value of the first to the first to fourth strain gauges R11 to R14, which are relatively highly sensitive, is reduced. By measuring the force acting on the basis of this, a measurement excellent in S / N becomes possible. Of course, the applied force may be measured based on the amount of change in the electric resistance of each of the 2-1 to 2-4 strain gauges R21 to R24. In the measurement, the first to the first to fourth strain gauges R11 to R14 or the 2-1 to the second to fourth strain gauges R21 to R24 acted by forming a Wheatstone bridge circuit (not shown). It is also possible to measure the moment.

<2-6. Measurement principle of force Fx in X-axis direction and force Fy in Y-axis direction by basic structure having waveform detection part>
In the above description, the method of measuring the moment Mz around the Z axis using the basic structure 101w shown in FIG. 20 has been described. However, the present force sensor uses the force Fx in the X axis direction and the force Fy in the Y axis direction. Can also be measured. As an example, a principle for measuring the force in the X-axis positive direction + Fx will be described with reference to FIG.

  FIG. 23 is a view for explaining forces acting on the detection portions A1 to A4 and B1 to B4 of the deformed body when a force in the positive direction of the X axis acts on the movable portion 120 having the basic structure in FIG. In FIG. 23, a thick black arrow shown in parallel with the X axis indicates the acting force + Fx, and a thick black arrow shown in a gap between the first deformable body 141 and the second deformable body 142. Arrows indicate the directions of forces acting on the respective detection sites A1 to A4 and B1 to B4.

  As shown in FIG. 23, when a force + Fx in the positive direction of the X-axis acts on the movable portion 120 of the basic structure 101w, of the deformed bodies 141 and 142, the 1-1 detection portion A1 and the A tensile force acts on the 2-1 detection site B1, and the 1-4 detection site A4 and the 2-4 detection site B4 located in the fourth quadrant. On the other hand, among the deformed bodies 141 and 142, the first to second detection parts A2 and B2 located in the second quadrant, and the first to third detection parts A3 and B3 located in the third quadrant are located. A compressive force acts on the 2-3 detection site B3. This can be understood from the state of the elastic deformation of the deformable body 140 shown in FIG. 16 and FIG. For this reason, in the basic structure 101w, the 1-1 detection part A1 and the 2-1 detection part B1 located in the first quadrant, and the 1-4 detection part A4 and the second detection part A4 located in the fourth quadrant are located. At the 4 detection site B4, the displacement units 61d and 62d are displaced in the positive direction of the Z-axis (forward direction in FIG. 23). On the other hand, in the 1-2 detection site A2 and the 2-2 detection site B2 located in the second quadrant, and the 1-3 detection site A3 and the 2-3 detection site B3 located in the third quadrant, The displacement units 61d and 62d are displaced in the negative Z-axis direction (the depth direction in FIG. 23).

  In other words, when the basic structure 101w is used as a force sensor of the capacitance type, the first capacitance element C11 and the second capacitance element C21 disposed in the first quadrant, and the fourth quadrant are used. The arranged first to fourth capacitive elements C14 and C24 each have a reduced capacitance value. On the other hand, the 1-2 capacitive element C12 and the 2-2 capacitive element C22 arranged in the second quadrant, and the 1-3 capacitive element C13 and the 2-3 capacitive element C23 arranged in the third quadrant, In any case, the capacitance value increases.

Therefore, the detection circuit 150 measures the applied force Fx in the X-axis direction using the following [Equation 9]. In [Equation 10], Fx1 is the force in the X-axis direction measured based on the elastic deformation of the first deformable body 141, and Fx2 is the X-axis direction measured based on the elastic deformation of the second deformable body 142. Power.
[Equation 9]
Fx1 = -C11 + C12 + C13-C14
Fx2 = -C21 + C22 + C23-C24

  On the other hand, although not shown, when a force + Fy in the positive Y-axis direction acts on the movable portion 120, as will be understood from the elastic deformation of the deformable body 140 shown in FIGS. The capacitance value fluctuates. That is, the electrostatic capacitances of the 1-1 capacitance element C11 and the 2-1 capacitance element C21 located in the first quadrant, and of the 1-2 capacitance element C12 and the 2-2 capacitance element C22 located in the second quadrant. The capacitance value increases, and the first to third capacitance elements C13 and C23 located in the third quadrant, and the first to fourth capacitance elements C14 and C4 located in the fourth quadrant The capacitance value of C24 decreases.

Therefore, the detection circuit 150 measures the applied force Fy in the Y-axis direction using the following [Equation 10]. In [Equation 10], Fy1 is a force in the Y-axis direction measured based on the elastic deformation of the first deformable body 141, and Fy2 is a Y-axis direction measured based on the elastic deformation of the second deformable body 142. Power.
[Equation 10]
Fy1 = C11 + C12-C13-C14
Fy2 = C21 + C22-C23-C24

  As described above, in the capacitance-type force sensor using the basic structure 101w, the fluctuations in the capacitance values of the 2-1 to 2-4 capacitance elements C21 to C24, which are relatively sensitive. By measuring the force acting on the basis of the amount, a measurement excellent in S / N becomes possible. Of course, the applied force may be measured based on the amount of change in the capacitance value of the first to first to fourth to fourth capacitance elements C11 to C14.

  When the direction of the acting force is the negative direction of the X-axis or the negative direction of the Y-axis, the variation amounts of the capacitance values of the respective capacitance elements C11 to C24 are all reversed. Therefore, the signs of the forces Fx1 and Fx2 measured by [Equation 9] are both opposite. That is, by examining the sign and magnitude of the force Fx obtained by [Equation 9], the direction and magnitude of the applied force are measured. This is the same when measuring the force in the Y-axis direction using [Equation 10].

  On the other hand, if a strain gauge is arranged in each of the displacement portions 61d of the first to first to fourth detection portions A1 to A4, the basic structure 101w can be used as a strain gauge type force sensor. The stress generated in each displacement portion 61d when a force acts on the basic structure 101w is as already described with reference to FIG. Therefore, according to the force Fx shown in FIG. 23, the 1-1 strain gauge R11 and the 2-1 strain gauge R21 arranged in the first quadrant, and the 1-4 strain gauge R21 arranged in the fourth quadrant. The electrical resistance of the R14 and the second-fourth strain gauge R24 decreases due to the action of the compressive stress (see FIG. 7C). On the other hand, the 1-2 strain gauge R12 and the 2-2 strain gauge R22 arranged in the second quadrant, and the 1-3 strain gauge R13 and the 2-3 strain gauge R23 arranged in the third quadrant The electric resistance increases due to the action of tensile stress (see FIG. 7B).

  Here, it is necessary to pay attention to the following points. That is, in FIG. 7, when a compressive stress acts on the deformed body (see FIG. 7B), as shown by a thin arrow in the figure, a tensile stress is generated on the surface on the X axis negative side of the displacement portion 61d, When a tensile force (see FIG. 7C) acts on the deformable body, a compressive stress is generated on the surface on the X axis negative side of the displacement portion 61d. Therefore, the strain gauges R11, R21 arranged in the first quadrant and the strain gauges R14, R24 arranged in the fourth quadrant of FIG. 22 have an electric resistance value reduced by the action of compressive stress, and are arranged in the second quadrant. The strain gauges R12, R22 and the strain gauges R13, R14 arranged in the third quadrant have their electrical resistance increased by the action of tensile stress.

From this, the detection circuit 150 measures the applied force Fx in the X-axis direction using the following [Equation 11]. In [Equation 11], Fx1 is a force in the X-axis direction measured based on the elastic deformation of the first deformable body 141, and Fx2 is an X-axis direction measured based on the elastic deformation of the second deformable body 142. Power.
[Equation 11]
Fx1 = -R11 + R12 + R13-R14
Fx2 = -R21 + R22 + R23-R24

  On the other hand, though not shown, when a force + Fy in the positive Y-axis direction acts on the movable portion 120, as will be understood from the state of elastic deformation of the deformable body 140 shown in FIGS. The resistance value fluctuates. That is, the 1-1 strain gauge R11 and the 2-1 strain gauge R21 located in the first quadrant, and the 1-2 strain gauge R12 and the 2-2 strain gauge R22 located in the second quadrant have a tensile strength. Due to the action of the stress (see FIG. 7C), the electric resistance value increases. On the other hand, the 1-3 strain gauge R13 and the 2-3 strain gauge R23 located in the third quadrant, and the 1-4 strain gauge R14 and the 2-4 strain gauge R24 located in the fourth quadrant, The action of the compressive stress (see FIG. 7B) reduces the electric resistance value.

Accordingly, the detection circuit 150 measures the applied force Fy in the Y-axis direction using the following [Equation 12]. In [Equation 12], Fy1 is a force in the Y-axis direction measured based on the elastic deformation of the first deformable body 141, and Fy2 is a Y-axis direction measured based on the elastic deformation of the second deformable body 142. Power.
[Equation 12]
Fy1 = R11 + R12-R13-R14
Fy2 = R21 + R22-R23-R24

  In the case of the above-described strain gauge type force sensor, the electric resistance values of the strain gauges R11 to R14 disposed at the first to first to fourth detection sites A11 to A14 where relatively large stress occurs. By measuring the force or moment acting on the basis of the amount of variation, high-sensitivity measurement excellent in S / N can be performed.

<<<< §3. Principle of failure diagnosis of force sensor according to the present invention >>>
The force sensor using the basic structures 1, 101, and 101w according to the present invention can perform failure diagnosis with a single force sensor. Since each of the deformed bodies 30, 141, 142 of the basic structures 1, 101, 101w has flexibility, metal fatigue occurs due to overload or repeated load. As a result, cracks and the like may occur in the elastic bodies constituting the deformable bodies 30, 141, and 142, which may eventually break. For this reason, if a force sensor capable of performing failure diagnosis can be provided, the reliability and safety of the force sensor can be improved. The principle of the failure diagnosis is described, for example, in International Application PCT / JP2016 / 75236 by the present applicant.

<3-1. Fault Diagnosis in Capacitive Force Sensor>
First, returning to FIGS. 1 to 4, the principle of failure diagnosis will be described using the basic structure 1 as an example.

  When a repetitive load (force-Fy) acts on the basic structure 1 shown in FIGS. 1 to 4, metal fatigue occurs in the first deformed body 31 and the second deformed body 32. When the metal fatigue accumulates, the strength of the first deformable body 31 and the second deformable body 32 decreases, and ultimately, each of the deformable bodies 31 and 32 breaks. In general, when metal fatigue accumulates in a metal material, the metal material is softened, so that each of the deformable bodies 31 and 32 has a reduced spring constant. In other words, the sensitivity of the deformable bodies 31 and 32 to the force -Fy is higher than that in the initial state due to accumulation of metal fatigue. This can be understood by comparing FIGS. 24 and 25. In the force sensor 1c, the metal fatigue is remarkably exhibited in the first deformable body 31 where a relatively large stress is generated. Therefore, the change (decrease) in the spring constant, that is, the increase in the sensitivity to the force -Fy is remarkable in the first deformable body 31.

  FIG. 24 shows the magnitude of the force acting on the force sensor 1c and the first electric signal output from the force sensor 1c when no metal fatigue occurs in the force sensor 1c of FIG. 3 (initial state). FIG. 25 is a graph showing the relationship between T1a and the second electric signal T2a. FIG. 25 shows the magnitude of the force acting on the force sensor 1c when metal fatigue occurs in the force sensor 1c in FIG. It is a graph which shows the relationship between the 1st electric signal T1b and the 2nd electric signal T2b output from the said force sensor 1c. The signs at the end of T1 and T2 are used to distinguish between the electric signal in the initial state (a suffix is added at the end) and the electric signal in a state where metal fatigue is accumulated (b is added at the suffix). is there. The first electric signals T1a and T1b are electric signals indicating the amount of change in the capacitance value of the first capacitance element C1, and the second electric signals T2a and T2b are the capacitance values of the second capacitance element C2. Is an electrical signal indicating the amount of change in

  As can be understood from FIG. 24, when focusing on the first electric signal T1 corresponding to the first capacitive element C1 provided in the first deformable body 31 in which the spring constant decreases (increases in sensitivity) is relatively large, In the state, the slope (sensitivity) of the straight line of the first electric signal T1a is 0.5. On the other hand, referring to FIG. 25, in a state where the metal fatigue is accumulated, the slope (sensitivity) of the straight line indicating the first electric signal T1b is 0.75. Therefore, the sensitivity is increased by 50%.

  On the other hand, if attention is paid to the second electric signal T2 corresponding to the second capacitive element C2 provided in the second deformable body 32 in which the decrease in the spring constant (increase in sensitivity) is relatively small, as understood from FIG. In the initial state, the slope (sensitivity) of the straight line indicating the second electric signal T2a corresponding to the second capacitive element C2 arranged in the second deformable body 32 is 2.0. On the other hand, as can be understood from FIG. 25, in a state where the metal fatigue is accumulated, the slope (sensitivity) of the straight line indicating the second electric signal T2b corresponding to the second capacitive element C2 is 2.4. Therefore, the increase in sensitivity is only 20%.

  It should be noted here that the first deformed body 31 and the second deformed body 32 differ in the degree of occurrence of metal fatigue. That is, in the initial state, the ratio (T1a / T2a) between the first electric signal T1a and the second electric signal T2a is 0.25, whereas in the state where the metal fatigue is accumulated, the first electric signal T1a / T2a is the first electric signal T1a. This means that the ratio (T1b / T2b) between the electric signal T1b and the second electric signal T2b has increased to 0.3125. Since the ratio T1 / T2 gradually increases from 0.25 to 0.3125 with the repetitive load, the failure of the force sensor 1c is diagnosed by focusing on the change in the ratio. It is done.

  Specifically, the first electric signal T1 and the second electric signal T2 are measured while measuring the force -Fy based on the amount of change in the capacitance value of the second capacitance element C2 arranged in the second deformable body 32. Of the first electric signal T1a and the ratio of the second electric signal T2a in the initial state are within a predetermined range, whereby the force sensor 1c functions normally. Is determined. Of course, the applied force -Fy may be measured based on the amount of change in the capacitance value of the first capacitance element C1.

<3-2. Diagnosis of strain gauge type force sensor>
In the strain gauge type force sensor 1s, a new failure diagnosis can be performed in the same manner. That is, although not shown, when the force -Fy in the negative direction of the Y-axis acts on the force sensor 1s, as described above, both the first strain gauge R1 and the second strain gauge R2 increase their electric resistance values. . Therefore, if the electric resistance value is plotted on the vertical axis and the applied force −Fy in the negative direction of the Y-axis is plotted on the horizontal axis, these relationships are represented in a graph as a straight line similar to FIGS. 24 and 25. However, also in this case, with the use of the force sensor 1s, that is, with the accumulation of metal fatigue in each of the deformable bodies 31, 32, the respective deformable bodies 31, 32 soften (the spring constant decreases). . Due to this softening, the displacement generated at the detection sites A and B of the deformable bodies 31 and 32 increases, and the stress acting on the strain gauge increases accordingly. Also in the present force sensor 1s, the metal fatigue is remarkably exhibited in the first deformable body 31 where relatively large stress is generated. Therefore, the change (decrease) of the spring constant is remarkable in the first deformable body 31. In the strain gauge type force sensor 1 s, the smaller the spring constant of the deformable body 30 is, the smaller the stress generated in the deformable body is. Therefore, the sensitivity increases as the spring constant decreases. That is, due to the decrease in the spring constant, the sensitivity of each of the elastic bodies 31 and 32 to the force -Fy increases.

  From the above, assuming that an electric signal indicating the amount of change in the electric resistance value of the first strain gauge is T1 and an electric signal indicating the amount of change in the electric resistance value of the second strain gauge R2 is T2, the first electric signal T1 and the The ratio (T1 / T2) of the two electric signals T2 is different between the initial state and the case where the metal fatigue is accumulated. By utilizing this, the failure diagnosis of the force sensor 1s is performed.

  Hereinafter, the principle for performing a failure diagnosis in the force sensor 1s will be described with reference to FIGS. FIG. 26 shows the magnitude of the force −Fy acting on the force sensor 1 s in the negative Y-axis direction when the metal sensor does not experience metal fatigue (initial state) in FIG. FIG. 27 is a graph showing a relationship between the output first electric signal T1a and the second electric signal T2a. FIG. 27 shows a case where the force sensor 1s in FIG. It is a graph which shows the magnitude | size of the force -Fy of the Y-axis negative direction which acts, and the 1st electric signal T1b and 2nd electric signal T2b output from the said force sensor 1s. The first electric signals T1a and T1b are electric signals indicating the amount of change in the electric resistance of the first strain gauge R1, and the second electric signals T2a and T2b are the electric signals indicating the change in the electric resistance of the second strain gauge R2. It is an electric signal indicating a quantity. Here, the signs at the end of T1 and T2 are used to distinguish between the electric signal in the initial state (a suffix is added at the end) and the electric signal in a state where metal fatigue is accumulated (b is added at the suffix). belongs to.

  As can be understood from FIG. 26, when focusing on the first electric signal T1 corresponding to the first strain gauge R1 provided in the first deformable body having a relatively large decrease in the spring constant (increase in sensitivity), the initial state , The slope (sensitivity) of the straight line of the first electric signal T1a is 2.0. On the other hand, referring to FIG. 27, in a state where the metal fatigue is accumulated, the slope (sensitivity) of the straight line indicating the first electric signal T1b is 2.8. Therefore, the sensitivity is increased by 40%.

  On the other hand, when attention is paid to the second electric signal T2 corresponding to the second strain gauge R2 provided in the second deformable body 32 in which the reduction (increase in sensitivity) of the spring constant is relatively small, as can be understood from FIG. In the initial state, the slope (sensitivity) of the straight line indicating the second electric signal T2a is 0.5. On the other hand, as understood from FIG. 27, in a state where the metal fatigue is accumulated, the slope (sensitivity) of the straight line indicating the second electric signal T2b corresponding to the second strain gauge R2 is 0.6. Therefore, the increase in sensitivity is only 20%.

  It should be noted here that the first deformed body 31 and the second deformed body 32 differ in the degree of occurrence of metal fatigue. That is, in the initial state, the ratio (T1a / T2a) between the first electric signal T1a and the second electric signal T2a is 4.0, whereas in the state where the metal fatigue is accumulated, the first electric signal T1a / T2a is the first electric signal T2a. This means that the ratio (T1b / T2b) between the electric signal T1b and the second electric signal T2b has increased to 4.667. Since the ratio T1 / T2 gradually increases from 4.0 to 4.667 with the application of a repetitive load, the failure diagnosis of the force sensor 1s is performed by focusing on the change in the ratio. It is done.

  Specifically, while measuring the force -Fy based on the amount of change in the electric resistance value of the first strain gauge R1 disposed on the first deformable body 31, the first electric signal T1 and the second electric signal T2 are measured. By evaluating whether or not the difference between the ratio and the ratio between the first electric signal T1a and the second electric signal T2a in the initial state is within a predetermined range, the force sensor 1s functions normally. Is determined. Of course, the applied force -Fy may be measured based on the amount of change in the electric resistance value of the second strain gauge R2.

<3-3. Failure diagnosis in other force sensors>
(3-3-1. In the case of the force sensor 101c shown in FIG. 11)
The above-described failure diagnosis can be adopted also in the failure diagnosis of the capacitance type force sensor 101c in FIG.

As an example, a method of diagnosing a failure using the clockwise moment −Mz (same moment as in FIG. 9) acting on the force receiving body 120 of the force sensor 101c will be described. First, electric signals corresponding to -Mz1 and -Mz2 in the above [Equation 1] are referred to as a first electric signal T1 and a second electric signal T2. That is, when the first electric signal T1 and the second electric signal T2 are newly written down, the following [Equation 13] is obtained.
[Equation 13]
T1 = -C11 + C12-C13 + C14
T2 = -C21 + C22-C23 + C24

  Also in the force sensor 101c shown in FIG. 11, a change occurs in the ratio between the first electric signal T1 and the second electric signal T2 as metal fatigue accumulates in the first deformable body 141 and the second deformable body 142. This is used to diagnose the failure of the force sensor. Therefore, also in the following description, the first and second electric signals in the initial state in which metal fatigue does not accumulate in the first deformation body 141 and the second deformation body 142 are denoted by T1a and T2a, respectively, and The first and second electric signals in a state where the metal fatigue is accumulated in the deformed body 141 and the second deformed body 142 are distinguished from each other as T1b and T2b, respectively.

  In an initial state where metal fatigue is not accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the moment -Mz acting on the force sensor 101c and the first and second electric signals T1a, T2a at this time. Is the same as the graph shown in FIG. Further, in a state where the metal fatigue is accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the moment -Mz acting on the force sensor and the first and second electric signals T1a, T2a at this time. Is the same as the graph shown in FIG.

  The principle and method for determining whether the force sensor 101c is functioning normally are described in 3-1. Is the same as That is, 3-1. By replacing the first electric signal T1 (T1a, T1b) and the second electric signal T2 (T2a, T2b) in [Equation 13], the principle and method of failure diagnosis of the force sensor 101c can be understood. Therefore, a detailed description of the principle and method is omitted here. In addition, even if the reverse moment + Mz acts, the failure diagnosis can be performed in the same manner.

Further, it is also possible to perform a failure diagnosis using the force Fx acting on the force receiving body 120 in the X-axis direction. In this case, the electric signals corresponding to Fx1 and Fx2 in [Equation 3] described above may be used as the first electric signal T1 and the second electric signal T2. That is, when the first electric signal T1 and the second electric signal T2 are newly written down, the following [Equation 14] is obtained.
[Equation 14]
T1 = -C11 + C12 + C13-C14
T2 = -C21 + C22 + C23-C24

  Again, in the following description, the first and second electric signals in the initial state where metal fatigue does not accumulate in the first deformable body 141 and the second deformable body 142 are T1a and T2a, respectively, and the first deformable body The first and second electric signals in a state where the metal fatigue is accumulated in the 141 and the second deformable body 142 are distinguished from each other as T1b and T2b, respectively.

  In an initial state in which metal fatigue is not accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fx acting on the force sensor 101c, the first and second electric signals T1a, T2a at this time, and , Is the same as the graph shown in FIG. Further, in a state where metal fatigue is accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fx acting on the force sensor 101c and the first and second electric signals T1a, T2a at this time. Is the same as the graph shown in FIG.

  The principle and method for determining whether the force sensor 101c is functioning normally are described in 3-1. Is the same as That is, 3-1. By reading the first electric signal T1 (T1a, T1b) and the second electric signal T2 (T2a, T2b) in [Equation 14], the principle and method of failure diagnosis of the force sensor 101c can be understood. Therefore, a detailed description of the principle and method is omitted here.

  Further, it is also possible to diagnose the failure of the force sensor 101c using the force Fy acting on the force receiving body 120 in the Y-axis direction. In this case, the electric signals corresponding to Fy1 and Fy2 in [Equation 4] described above may be the first electric signal T1 and the second electric signal T2. In the initial state where metal fatigue has not accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fy acting on the force sensor 101c, the first and second electric signals T1a, T2a at this time, and , Is the same as the graph shown in FIG. Further, in a state where metal fatigue is accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fy acting on the force sensor, and the first and second electric signals T1a, T2a at this time are determined. , Is the same as the graph shown in FIG.

  The principle and method for determining whether or not the force sensor 101c is functioning normally are the same as in the case of performing a failure diagnosis based on the force Fx, and thus a detailed description thereof is omitted here.

(3-3-2. Force sensor 101s shown in FIG. 12)
Next, the above-described failure diagnosis can be adopted also in the failure diagnosis of the strain gauge type force sensor 101s shown in FIG.

As an example, a method of diagnosing a failure using the clockwise moment −Mz (same moment as in FIG. 9) acting on the force receiving body 120 of the force sensor 101s will be described. First, electric signals corresponding to -Mz1 and -Mz2 in [Equation 2] described above are referred to as a first electric signal T1 and a second electric signal T2. That is, when the first electric signal T1 and the second electric signal T2 are newly written down, the following [Equation 15] is obtained.
[Equation 15]
T1 = -R11 + R12-R13 + R14
T2 = -R21 + R22-R23 + R24

  Also in the force sensor 101s shown in FIG. 12, the ratio between the first electric signal T1 and the second electric signal T2 changes as the metal fatigue accumulates in the first deformable body 141 and the second deformable body 142. This is used to diagnose the failure of the force sensor. Therefore, also in the following description, the first and second electric signals in the initial state in which metal fatigue does not accumulate in the first deformation body 141 and the second deformation body 142 are denoted by T1a and T2a, respectively, and The first and second electric signals in a state where the metal fatigue is accumulated in the deformed body 141 and the second deformed body 142 are distinguished from each other as T1b and T2b, respectively.

  In an initial state where metal fatigue is not accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the moment -Mz acting on the force sensor 101s and the first and second electric signals T1a, T2a at this time. Is the same as the graph shown in FIG. Further, in a state where metal fatigue is accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the moment −Mz acting on the force sensor 101s and the first and second electric signals T1a, The relationship with T2a is the same as the graph shown in FIG.

  The principle and method for determining whether or not the force sensor 101s is functioning normally are described in 3-2. Is the same as That is, 3-2. By replacing the first electric signal T1 (T1a, T1b) and the second electric signal T2 (T2a, T2b) in [Equation 15], the principle and method of failure diagnosis of the force sensor 101s can be understood. Therefore, a detailed description of the principle and method is omitted here. Of course, the failure diagnosis can be performed in the same manner even when the counterclockwise moment + Mz acts.

Further, it is also possible to perform a failure diagnosis using the force Fx acting on the force receiving body 120 in the X-axis direction. In this case, the electric signals corresponding to Fx1 and Fx2 in [Equation 5] described above may be used as the first electric signal T1 and the second electric signal T2. That is, when the first electric signal T1 and the second electric signal T2 are newly written down, the following [Equation 16] is obtained.
[Equation 16]
T1 = -R11 + R12 + R13-R14
T2 = -R21 + R22 + R23-R24

  Again, in the following description, the first and second electric signals in the initial state where metal fatigue does not accumulate in the first deformable body 141 and the second deformable body 142 are T1a and T2a, respectively, and the first deformable body The first and second electric signals in a state where the metal fatigue is accumulated in the 141 and the second deformable body 142 are distinguished from each other as T1b and T2b, respectively.

  In the initial state where metal fatigue is not accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fx acting on the force sensor 101s, the first and second electric signals T1a, T2a at this time, and , Is the same as the graph shown in FIG. Further, in a state where metal fatigue is accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fx acting on the force sensor 101s and the first and second electric signals T1a, T2a at this time. Is the same as the graph shown in FIG.

  The principle and method for determining whether or not the force sensor 101s is functioning normally are described in 3-2. Is the same as That is, 3-2. By replacing the first electric signal T1 (T1a, T1b) and the second electric signal T2 (T2a, T2b) in [Equation 16], the principle and method of failure diagnosis of the force sensor according to the present embodiment are understood. You. Therefore, a detailed description of the principle and method is omitted here.

  Further, it is also possible to perform a failure diagnosis using the force Fy acting on the force receiving body 120 in the Y-axis direction. In this case, the electric signals corresponding to Fy1 and Fy2 in [Equation 6] described above may be the first electric signal T1 and the second electric signal T2. In the initial state where metal fatigue is not accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fy acting on the force sensor 101s, the first and second electric signals T1a, T2a at this time, and , Is the same as the graph shown in FIG. Further, in a state where metal fatigue is accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fy acting on the force sensor 101s and the first and second electric signals T1a, T2a at this time. Is the same as the graph shown in FIG.

  The principle and method for determining whether or not the force sensor 101s is functioning normally are the same as in the case of performing a failure diagnosis based on the force Fx, and thus a detailed description thereof is omitted here.

(3-3-3. In the case of a force sensor using the basic structures 101a, 101b, 101b 'shown in FIGS. 13 to 15)
Next, a failure diagnosis in a capacitance type force sensor using the basic structure 101a shown in FIG. 13 will be described. Although this force sensor is not shown, eight portions (first to first to fourth detection portions A1 to A4 and 2-1) of the force sensor which are located on the V axis and the W axis are included. It is assumed that capacitive elements C11 to C24 are arranged in all of the second to fourth detection sites B1 to B4). It is assumed that the distances between the electrodes constituting the capacitance elements C11 to C24 are all the same, and the effective facing areas are all the same.

  The principle and method of failure diagnosis in such a force sensor are described in 3-3-1. This is substantially the same as the case of the force sensor 101c of the capacitance type shown in FIG. However, the 2-1 to 2-4 capacitive elements C21 to C24 are arranged on the thin portions 142t1 to 142t4 of the second deformable body 142. FIG. 24 is a graph showing the relationship between the applied force (Fx, Fy) or moment (Mz) and the first electric signal T1 (T1a, T1b) and the second electric signal T2 (T2a, T2b). 25 and the second electric signals T2a and T2b shown in FIG. However, their inclination ratios are the same.

  Accordingly, in the initial state, the ratio (T1a / T2a) between the first electric signal T1a and the second electric signal T2a is 0.25, and the first electric signal T1b and the first electric signal T1b are in the state where the metal fatigue is accumulated. The ratio (T1b / T2b) to the two electric signals T2b is 0.3125.

  Next, a failure diagnosis in a capacitance type force sensor using the basic structures 101b and 101b 'shown in FIGS. 14 and 15 will be described. Although not shown in these force sensors, eight parts (first to first to fourth detection parts A1 to A4 and second to fourth detection parts) located on the V axis and the W axis among the respective force sensors are not shown. It is assumed that the capacitive elements C11 to C24 are arranged in all of the -1 to 2-4 detection sites B1 to B4). Further, it is assumed that the distances between the electrodes constituting the respective capacitance elements C11 to C24 are all the same, and the effective facing areas are all the same.

  As described above, these force sensors are also similar to the force sensors using the basic structure 101a shown in FIG. 13 in that the second to second to fourth capacitance elements C21 to C24 are arranged. Since the thin portions 142t1 to 142t4 are provided only in the deformable body 142, the ratio (T1a / T2a) between the first electric signal T1a and the second electric signal T2a in the initial state and the metal fatigue are accumulated. The ratio (T1b / T2b) between the first electric signal T1b and the second electric signal T2b in the state has the same value as that of the force sensor using the basic structure 101a shown in FIG. In other words, the capacitance type force sensor using the basic structures 101b and 101b ′ shown in FIGS. 14 and 15 has the same characteristics as the capacitance type force sensor using the basic structure 101a. are doing. Therefore, even in these force sensors, the principle and method of failure diagnosis are described in 3-3-1. This is substantially the same as the case of the force sensor 101c shown in FIG.

  Next, failure diagnosis in a strain gauge type force sensor using the basic structure 101a shown in FIG. 13 will be described. In this force sensor, although not shown, eight portions (first to first to fourth detection portions A1 to A4 and second to fourth portions) located on the V axis and the W axis are included in the force sensor. It is assumed that strain gauges R11 to R24 are arranged in all of the first to second to fourth detection sites B1 to B4). Further, all of the strain gauges R11 to R24 have the same characteristics.

  The principle and method of failure diagnosis in such a force sensor are described in 3-3-2. This is substantially the same as the case of the force sensor 101s shown in FIG. However, the 2-1 to 2-4 strain gauges R21 to R24 are arranged on the thin portions 142t1 to 142t4 of the second deformable body 142. Therefore, a graph showing the relationship between the applied force (Fx, Fy) or moment (Mz) and the first electric signal (T1a, T1b) and the second electric signal T2 (T2a, T2b) is shown in FIG. 26 and FIG. Both the second electric signals T2a and T2b shown in FIG. 27 have a larger slope than the slope. However, their inclination ratios are the same. That is, in the initial state, the ratio (T1a / T2a) between the first electric signal T1a and the second electric signal T2a is 4.0, and the first electric signal T1b and the second electric signal T2a are accumulated in a state where the metal fatigue is accumulated. The ratio to the signal T2b (T1b / T2b) is 4.667.

  Next, failure diagnosis of a strain gauge type force sensor using the basic structures 101b and 101b 'shown in FIGS. 14 and 15 will be described. Although not shown in these force sensors, eight parts (first to first to fourth detection parts A1 to A4 and second to fourth detection parts) located on the V axis and the W axis among the respective force sensors are not shown. It is assumed that strain gauges R11 to R24 are arranged in all of the -1 to 2-4 detection sites B1 to B4). Further, each of the strain gauges R11 to R24 has the same characteristics.

  As described above, these force sensors also have the second to the second-4 strain gauges R11 to R24, similarly to the force sensor using the basic structure 101a shown in FIG. Since the thin portions 142t1 to 142t4 are provided only in the deformable body 142, the ratio (T1a / T2a) between the first electric signal T1a and the second electric signal T2a in the initial state and the metal fatigue are accumulated. The ratio (T1b / T2b) between the first electric signal T1b and the second electric signal T2b in the state has the same value as that of the force sensor using the basic structure 101a shown in FIG. In other words, the strain gauge type force sensor using the basic structures 101b and 101b ′ shown in FIGS. 14 and 15 has the same characteristics as the strain gauge type force sensor using the basic structure 101a. I have. Therefore, even in these force sensors, the principle and method of failure diagnosis are described in 3-3-2. This is substantially the same as the case of the force sensor 101s shown in FIG.

<<<< §4. Further modified example of detection site >>>
Next, FIG. 28 is a schematic side view showing a modification of the detection portion of the basic structure in each of the above embodiments. As shown in FIG. 28, the detection portion E according to the present modification includes a first connection portion 71 and a second connection portion 72 arranged so as to be relatively movable in one axial direction (Y-axis direction in FIG. 28). It is located between them. The detection portion E is made of a material having elasticity (for example, metal) and has a uniform thickness, and has a circular arc shape smoothly curved so as to expand in the negative direction of the X-axis (the right side in FIG. 29). ing. As shown in FIG. 29, when the imaginary axis L parallel to the X axis is taken into consideration so as to pass through the site located on the X axis negative side (right side), the detection site E is viewed from the Z axis direction. It is symmetric about the virtual axis.

  Next, the operation of the detection site E will be described with reference to FIG. FIG. 29A is a schematic diagram showing the detection site E when a compressive force in the Y-axis direction acts on the detection site E shown in FIG. 28, and FIG. 29B is a schematic view showing the detection site E shown in FIG. FIG. 5 is a schematic diagram showing the detection site E when a tensile force in the Y-axis direction acts on the site E. As will be described later, a detection element (capacitance element or strain gauge) is arranged at a position R on the negative side of the X-axis, among the parts where the detection part E intersects the virtual axis L. Therefore, here, the displacement of the position R or the stress generated at the position R will be described in detail. In the initial state, it is assumed that no stress is generated on the surface of the detection portion E. In FIG. 29, the thick black arrows indicate the direction of the force acting along the Y-axis direction, and the thick white arrows arranged in parallel with the X-axis indicate the most The direction of the displacement generated at the position R on the negative side of the X axis is shown, and thin arrows indicate the stress generated at the position R (“→ ←” indicates a compressive stress, and “← →” indicates a tensile stress).

  First, as shown in FIG. 29A, when the first connection portion 71 is relatively moved along the Y-axis direction so as to approach the second connection portion 72, the detection portion E moves in the Y-axis direction. Compressed. As a result, the position R is displaced in the negative direction of the X axis. Further, at this time, since the radius of curvature near the position R becomes smaller, a tensile stress is generated at the position R along the Y-axis direction. On the other hand, as shown in FIG. 29B, when the first connection portion 71 is relatively moved along the Y-axis direction so as to be separated from the second connection portion 72, the detection portion E is moved in the Y-axis direction. Stretched. As a result, the position R is displaced in the positive X-axis direction.

  Further, the stress generated at the position R when a force acts on the detection site E will be discussed. As shown in FIG. 29A, when a compressive force acts between the first connection portion 71 and the second connection portion 72, the radius of curvature near the position R decreases, so that the position R is moved to the position R in the Y-axis direction. Along with tensile stress. On the other hand, as shown in FIG. 29 (b), when a tensile force acts between the first connection portion 71 and the second connection portion 72, the radius of curvature near the position R increases, so that the position R has a Y-axis. A compressive stress occurs along the direction. As a result, the direction of the force acting on the detection site E (compression or tension) and the direction of the stress generated at the position R (compression or tension) are opposite to each other. The direction (compression or tension) of the stress generated at the position R ′ on the positive side of the X-axis among the portions where the detection site E intersects the virtual axis L depends on the deformation shown in FIGS. 29 (a) and 29 (b). As understood from the embodiment, the direction of the force (compression or tension) acting on the detection site E is the same.

  When such a detection site is adopted in the basic structure 1 shown in FIG. 1, the first deformable body 31 is replaced with a first movable portion side connection portion 31m and a first fixed portion side connection portion 31f. The first detection site E1 is arranged as the first detection site E1, and the above-described detection site E is inserted between the second movable portion side connection portion 32m and the second fixed portion side connection portion 32f instead of the second deformable body 32. What is necessary is just to arrange | position as 2 detection parts E2. However, the second detection site E2 is configured to have a larger radius of curvature than the first detection site E1. Thus, the spring constant of the second detection part E2 is set smaller than the spring constant of the first detection part E1.

  Alternatively, when such a detection site is employed in the basic structure 101 having the annular deformable bodies 141 and 142 shown in FIG. 8, the first to first to fourth detection sites A1 to A4 and the 2-1 The above-described detection sites E may be arranged at positions corresponding to the second to fourth detection sites B1 to B4, respectively. That is, gaps are provided along the circumferential direction at eight positions corresponding to the 1-1 to 1-4 detection sites A1 to A4 and the 2-1 to 2-4 detection sites B1 to B4. The detection site E shown in FIG. However, the second detection site E2, which is the four detection sites E disposed at the 2-1 to 2-4 detection sites B1 to B4, is disposed at the 1-1 to 1-4 detection sites A1 to A4. It is configured to have a larger radius of curvature than the first detection site E1, which is the four detection sites E to be measured. Thus, the spring constant of the second detection part E2 is set smaller than the spring constant of the first detection part E1. Note that the four detection sites E of the first detection site E1 may have the same configuration, and the four detection sites E of the second detection site E2 may have the same configuration.

  A specific arrangement example will be described with reference to FIGS. FIG. 30 is a schematic top view showing an example of a deformed body having the detection site shown in FIG. FIG. 31A is a schematic top view showing another example of the deformed body having the detection site shown in FIG. 28, and FIG. 31B is a sectional view taken along line bb of FIG. It is. Since the detection site may be provided in a form common to the first deformable body 141 and the second deformable body 142, the first deformable body 141 is represented in FIGS. Only one is shown.

  In the first deformable body 141 shown in FIG. 30, a region including a position overlapping with the V axis and the W axis when viewed from the Z axis direction is replaced with a detection site E1 shown in FIG. Here, each detection site E1 is formed in such a manner that a circle providing an arc of the detection site E1 exists parallel to the XY plane. Each detection site E1 is arranged so as to protrude radially outward.

  When a force or moment acts on the first deformable body 141 having such a detection part E1, the detection part E1 receives a compressive force or a tensile force in the circumferential direction of the first deformable body. Therefore, as described above, a portion of the detection portion E1 overlapping the V axis and the W axis is displaced along the radial direction of the first deformable body 141 (along the V axis direction or the W axis direction). Further, a compressive stress or a tensile stress is generated at the site.

  On the other hand, the first deformed body 141 shown in FIG. 31A has a region including a position overlapping with the V axis and the W axis when viewed from the Z axis direction, as in the first deformed body 141 shown in FIG. Although it is replaced with the detection site E1 shown, the arrangement is different from that in FIG. That is, as shown in FIG. 31B, in the first modified body 141 of FIG. 31A, the detection portions E1 arranged in the first and third quadrants provide arcs of these detection portions E1. Are formed in such a manner that the circles present in parallel to the WZ plane, and the detection portions E1 arranged in the second quadrant and the fourth quadrant have the circles providing the arcs of these detection portions E1 in the VZ plane. It is formed in such a manner that it exists in parallel with.

  When a force or moment acts on the first deformable body 141 having such a detection part E1, the detection part E1 receives a compressive force or a tensile force in the circumferential direction of the first deformable body. Therefore, as described above, a portion of the detection portion E1 overlapping the V axis and the W axis is displaced along the Z axis direction (along the V axis direction or the W axis direction). Further, a compressive stress or a tensile stress is generated at the site.

  FIG. 32 is a schematic diagram showing the detection site E in FIG. 28 where the capacitance element C is arranged. For example, as shown in FIG. 32, the capacitive element C has a displacement electrode Em disposed at a position R via a displacement substrate Im (insulator), and a fixed substrate If (insulated) at a position opposed to the displacement electrode Em. Through the body) and by disposing a fixed electrode Ef that does not move in the XYZ three-dimensional coordinate system. The detection part E having the capacitance element C can be adopted in a force sensor using the basic structure 1 shown in FIG. 1 or a force sensor using the annular basic structure 101 shown in FIG. The position R is a position of the detection site E where the displacement (the compression force and the tensile force) acting on the detection site E is greatest in the X-axis direction. Therefore, if the capacitive element C is configured at the position R, the force or moment acting with the highest sensitivity can be measured.

  When a compressive force acts on the detection site E shown in FIG. 32, the position R moves in the negative direction of the X-axis as described above (see FIG. 29A). For this reason, the distance between the displacement electrode Em and the fixed electrode Ef decreases, and the capacitance value of the capacitance element C increases. On the other hand, when a tensile force acts on the detection portion E shown in FIG. 32, the position R moves in the positive direction of the X-axis as described above (see FIG. 29B). For this reason, the distance between the displacement electrode Em and the fixed electrode Ef increases, and the capacitance value of the capacitance element C decreases. After all, each detection site of the force sensors 1c and 101c shown in FIGS. 3 and 11 and the force sensor using the basic structure 1w and 101w shown in FIGS. 5 and 20 is replaced with a detection site E shown in FIG. Thus, even if a new force sensor is configured, the new force sensor exhibits the same behavior (output characteristic) as when a force or moment acts on each force sensor before replacement. Will be.

  As shown in FIG. 32, if the fixed substrate 73 is arranged on the same plane as the fixed portion 110, the fixed electrodes E (four) opposed to the four displacement electrodes Em of the first deformed body 141 and the second deformed electrode This is advantageous because a total of eight fixed electrodes (four fixed electrodes) opposed to the four displacement electrodes Em of the body can be constituted by a single substrate (fixed substrate 73).

  FIG. 33 is a schematic diagram showing the detection site E in FIG. 28 where the strain gauge R is arranged. The strain gauge may be arranged at the position R as an example. Such a detection site E can be used in the basic structure 1 shown in FIG. 1 or in the annular basic structure 101 shown in FIG. The position R is a position where the largest stress acts on the detection site E due to the force (compression force and tension force) acting on the detection site E. Therefore, if the strain gauge R is disposed at the position R, the force or moment acting with the highest sensitivity can be measured.

  When a compressive force acts on the detection portion E shown in FIG. 33, a tensile stress acts on the position R as described above (see FIG. 29A). Therefore, the electric resistance value of the strain gauge R increases. On the other hand, when a tensile force acts on the detection portion E shown in FIG. 33, a compressive stress acts on the position R as described above. (See FIG. 29 (b)). For this reason, the electric resistance value of the strain gauge R decreases. After all, each detection site of the force sensors 1s and 101s shown in FIGS. 4 and 12 and the force sensor using the basic structure 1w and 101w shown in FIGS. 5 and 20 is replaced with a detection site E shown in FIG. Even if a new force sensor is constructed, this new force sensor exhibits the same behavior (output characteristic) as when a force or moment acts on each force sensor before replacement. Will be.

<<<< §5. Device to keep the effective facing area between the electrodes constant in the capacitance type force sensor >>>>>
In addition, in the force sensor of the capacitance type, even when the relative position of the displacement electrode with respect to the fixed electrode changes as a result of the force in each axial direction or the moment around each axis acting, a pair of the capacitive elements constitutes a capacitive element. It is also conceivable to set one area of the fixed electrode and the displacement electrode constituting each capacitor to be larger than the other area so that the effective facing area of the electrodes does not change. This is the case where the contour of an electrode having a smaller area (eg, a displacement electrode) is projected on the surface of an electrode having a larger area (eg, a fixed electrode) in the normal direction of the electrode to form an orthographic projection image. In this state, the projected image of the electrode having the smaller area is completely included in the surface of the electrode having the larger area. If this state is maintained, the effective area of the capacitive element formed by both electrodes becomes equal to the area of the smaller electrode, and is always constant. That is, the accuracy of force detection can be improved.

  Of the embodiments described so far, the force sensor 1c shown in FIG. 3, the force sensor 101s shown in FIG. 11, and the structure shown in FIG. The area of the electrode is configured to be larger than the area of the displacement electrode.

DESCRIPTION OF SYMBOLS 1 Basic structure 1c Capacitance type force sensor 1s Strain gauge type force sensor 1w Basic structure 10 Fixed part 20 Movable part 30 Deformed body 31 First deformed body 31e First elastic body 31f First fixed part side connection part 31m First movable portion side connection portion 32 Second deformable body 32e Second elastic body 32f Second fixed portion side connection portion 32m Second movable portion side connection portion 40 Detection circuit 61d First displacement portion 61e1, 61e2 A pair of first deformation Part 61f, 61m Connection part 62d Second displacement part 62e1, 62e2 A pair of second deformation parts 62f, 62m Connection part 71 First connection part 72 Second connection part 73 Fixed substrate 101 Basic structure 101a Basic structure 101b Basic structure 101c Electrostatic Capacitive type force sensor 101s Strain gauge type force sensor 101w Basic structure 110 Fixed part 120 Movable part 131 Connected body 131l Connected body 1 2 Connected body 132a, 132b, 132c, 132d Connected body 133 Connected body 134, 134a, 134b Connected body 135 Connected body 135l Connected body 136, 136a, 136b Connected body 137 Connected body 138, 138a, 138b Connected body 140 Deformed body 141 1st deformed body 142 2nd deformed body 142t1, 142t2, 142t3, 142t4 Thin portion 142b, 142b1, 142b2, 142b3, 142b4 Deformed body 150 Detection circuit

Claims (2)

A force sensor for detecting a moment about the Z-axis in an XYZ three-dimensional coordinate system, comprising: a fixed body fixed on an XY plane and centered on an origin when viewed from a positive direction of the Z-axis;
An annular force receiving member disposed concentrically with the fixed body when viewed from the positive direction of the Z axis, and relatively moved with respect to the fixed body by the action of a moment about the Z axis;
An elastically deformable body having one end supported by the fixed body and the other end supported by the force-receiving body;
A displacement electrode disposed on the elastically deformable body, and a capacitive element having a counter electrode facing the displacement electrode;
A detection circuit that outputs an electric signal indicating a moment about the Z-axis applied to the force-receiving element based on a change in the capacitance value of the capacitance element;
With
As the elastic deformation body,
A first and a second elastically deformable body symmetrically arranged with respect to the X axis;
A first arc-shaped deformable body having one end and the other end, a first connecting body connecting the one end of the first arc-shaped deformable body to the fixed body, A second connector for connecting the other end of the first arc-shaped deformed member to the force receiving member,
A second arc-shaped deforming body having one end and the other end, a third connecting body connecting the one end of the second arc-shaped deforming body to the fixed body, A fourth connecting member that connects the other end of the second arc-shaped deformed member to the force receiving member,
The first arc-shaped deformed body has a smaller thickness than the first and second connected bodies, and the second arc-shaped deformed body has a smaller thickness than the third and fourth connected bodies. And
A force sensor , wherein a connection body that connects the fixed body and the force receiving body is provided between the second connection body and the fourth connection body . A third elastic deformation body symmetrically arranged with respect to the Y axis and the first elastic deformation body;
A third arc-shaped deforming body having one end and the other end, a fifth connecting body connecting the one end of the third arc-shaped deforming body to the fixed body, A sixth connecting body that connects the other end of the third arc-shaped deformed body to the force receiving body,
The force sensor according to claim 1 , wherein the third arc-shaped deformed body has a smaller thickness than the fifth and sixth connected bodies.

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