JP2020012657A - Torque sensor - Google Patents

Abstract

To provide a torque sensor which can increase the accuracy of detection.SOLUTION: A torque sensor 40 includes: a first structure 41; a second structure 42; a third structure 43 between the first structure and the second structure; at least two sensor parts 44 and 45 between the first structure and the second structure; a plurality of first holes 61 in the first structure 41 for positioning a first equipment part; and a plurality of second holes 62 in the second structure 42 for positioning a second equipment part.SELECTED DRAWING: Figure 4

Description

  An embodiment of the present invention relates to a torque sensor applied to, for example, a robot arm or the like.

  The torque sensor has a first structure to which a torque is applied, a second structure to which the torque is output, and a plurality of strain generating portions as beams connecting the first structure and the second structure. In addition, a plurality of strain gauges as sensor elements are arranged in these strain generating portions. A bridge circuit is configured by these strain gauges (see, for example, Patent Documents 1, 2, and 3).

  2. Description of the Related Art In a torque converter for measuring a torque generated in an output section of an automobile engine or the like, a technique for reducing the influence of bending stress other than torque has been developed (for example, see Patent Document 4).

JP 2013-097735 A JP-A-2005-049209 JP 2017-172983 A JP 2010-169586 A

For example, a disc-shaped torque sensor has a first structure, a second structure, and a third structure between the first structure and the second structure, and the first structure and the second structure. And a strain-generating body as a strain sensor and a strain gauge.
When the first structure is fixed to, for example, a base of a robot arm, and the second structure is fixed to, for example, an arm of a robot arm, when the torque sensor is used, in addition to the torque, the transfer weight and load of the robot arm are also measured. And the bending moment accompanying the operation acceleration and the reaction force load are applied.

When attaching the torque sensor to the robot arm, it is necessary to align the axis of the torque sensor with, for example, the axis of the arm or the base of the robot arm.
Assuming that the shape of the first structure of the torque sensor is, for example, a cylinder, the shape of the base of the robot arm is a cylinder, and when fitting the cylinder into the cylinder, fitting the outer diameter of the cylinder to the inner diameter of the cylinder , The axes are matched. However, in this case, although the axes coincide, it is unclear exactly where the cylinder and cylinder are in contact. That is, since the outer diameter of the cylinder and the inner diameter of the cylinder are not perfect circles, it is expected that the outer surface of the cylinder and the inner surface of the cylinder will come into contact at several places at random.

  As described above, when the first structure of the torque sensor and the base or arm of the robot arm come into contact at several places at random, when a bending moment other than torque or a translational force is applied to the torque sensor, the first The structure and the second structure are deformed asymmetrically, and the strain sensor is deformed asymmetrically with the deformation, and an output is output from the sensor.

  When a bending moment or a load (X-axis direction Fx, Y-axis direction Fy, Z-axis direction Fz) other than torque is applied to the torque sensor, that is, a translational force is applied, a plurality of strain sensors provided in the torque sensor respond to displacement. Distortion occurs. Usually, the bridge circuit of the torque sensor is configured to output a voltage with respect to a force in the torque direction and not to output a voltage with respect to a force in a direction other than the torque. However, when the first structure or the second structure is asymmetrically deformed, asymmetric distortion is generated in a plurality of distortion sensors provided in the torque sensor. Due to this other-axis interference, a sensor output is generated, and the detection accuracy of the torque sensor is reduced.

  Embodiments of the present invention provide a torque sensor capable of improving detection accuracy.

  The torque sensor according to the present embodiment includes a first structure, a second structure, a third structure provided between the first structure and the second structure, and a first structure. At least two sensor portions provided between the second structure, a plurality of first holes provided in the first structure for positioning a first mounting portion, and And a plurality of second holes for positioning the second mounting portion.

FIG. 2 is a perspective view showing an example of a robot arm to which the first embodiment is applied. FIG. 2 is a plan view showing an example of a torque sensor applied to the first embodiment. FIG. 2 is a plan view showing an example of a mounting structure of the torque sensor according to the first embodiment. FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3. Sectional drawing which extracts and shows the part shown by arrow A of FIG. FIG. 9 is a perspective view showing an example of a half screw bolt, showing a mounting structure of a torque sensor according to a second embodiment. FIG. 9 is a perspective view of a part of the torque sensor mounting structure according to the second embodiment, showing a part of a hole for positioning. FIG. 9 is a perspective view of a partially cut-away view showing an assembly state of the torque sensor according to the second embodiment, showing an assembled state. FIG. 9 is a sectional view showing a first modification of the first embodiment and the second embodiment. FIG. 14 is a perspective view of a second modification of the second embodiment, partially cut away showing an assembled state.

Hereinafter, embodiments will be described with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals.
First, a robot arm 30 and a torque sensor 40 to which the present embodiment is applied will be described with reference to FIGS.
FIG. 1 shows an example of an articulated robot, that is, a robot arm 30. The robot arm 30 includes, for example, a base 31, a first arm 32, a second arm 33, a third arm 34, a fourth arm 35, a first drive unit 36, a second drive unit 37 as a drive source, and a third drive unit. 38, and a fourth drive section 39. However, the configuration of the robot arm 30 is not limited to this, and can be modified.

  The first arm 32 is rotatable with respect to the base 31 by a first driving unit 36 provided at the first joint J1. The second arm 33 is rotatable with respect to the first arm 32 by a second driving unit 37 provided at the second joint J2. The third arm 34 is rotatable with respect to the second arm 33 by a third drive unit 38 provided at the third joint J3. The fourth arm 35 is rotatably provided with respect to the third arm 34 by a fourth drive unit 39 provided at the fourth joint J4. Hands and various tools (not shown) are attached to the fourth arm 35.

The first drive unit 36 to the fourth drive unit 39 include, for example, a motor, a speed reducer, and a torque sensor described below.
FIG. 2 shows an example of a disk-shaped torque sensor 40 applied to the present embodiment. The torque sensor 40 includes a first structure 41, a second structure 42, a plurality of third structures 43, a first strain sensor 44 and a second strain sensor 45 as a sensor unit, and the like.

  The first structure 41 and the second structure 42 are formed in a ring shape, and the diameter of the second structure 42 is smaller than the diameter of the first structure 41. The second structure 42 is arranged concentrically with the first structure 41, and the first structure 41 and the second structure 42 are connected by a third structure 43 as a plurality of radially arranged beams. Have been. The plurality of third structures 43 transmit torque between the first structure 41 and the second structure 42. The second structure 42 has a hollow portion 42a, and, for example, a wiring (not shown) is passed through the hollow portion 42a.

  The first structure 41, the second structure 42, and the plurality of third structures 43 are made of metal, for example, stainless steel. It is also possible to use materials other than metals. The first structure 41, the second structure 42, and the plurality of third structures 43 have, for example, the same thickness. The mechanical strength of the torque sensor 40 is set by the thickness, width, and length of the third structure 43.

  Between the first structure 41 and the second structure 42, a first strain sensor 44 and a second strain sensor 45 are provided. Specifically, one end of a strain body 44a forming the first strain sensor 44 and one end of a strain body 45a forming the second strain sensor 45 are joined to the first structure 41, and the strain body 44a, The other end of 45a is joined to the second structure 42. The thickness of the strain body 44a, 45a is smaller than the thickness of the first structure 41, the second structure 42, and the plurality of third structures 43.

  A plurality of unillustrated strain gauges as sensor elements are provided on the surfaces of the strain bodies 44a and 45a, respectively. A first bridge circuit is configured by the sensor element provided on the strain body 44a, and a second bridge circuit is configured by the sensor element provided on the strain body 45a. That is, the torque sensor 40 includes two bridge circuits.

  Further, the first strain sensor 44 and the second strain sensor 45 are arranged at symmetrical positions with respect to the center of the first structure 41 and the second structure 42 (the center of action of torque). In other words, the first strain sensor 44 and the second strain sensor 45 are arranged on the diameter of the first and second annular structures 41 and 42.

  The first strain sensor 44 (strain body 44a) is connected to the flexible board 46, and the second strain sensor 45 (strain body 45a) is connected to the flexible board 47. The flexible boards 46 and 47 are connected to a printed board (not shown) covered by a cover 48. An operational amplifier for amplifying the output voltages of the two bridge circuits is disposed on the printed circuit board. The circuit configuration is not the essence of the present embodiment, and the description is omitted.

(1st Embodiment)
3 and 4 show the first embodiment. The torque sensor 40 is provided in, for example, the first drive unit 36 of the robot arm 30. However, the torque sensor 40 can be provided in, for example, the second drive unit 37 to the fourth drive unit 39 of the robot arm 30.

  3 and 4, the first structure 41 of the torque sensor 40 is fixed to, for example, the first arm 32 as a first attachment portion, and the second structure 42 is 2 It is fixed to a base 31 as an attachment part. However, it is also possible to fix the first structure 41 of the torque sensor 40 to the base 31 as the second mounting portion via the first drive section 36 and fix the second structure 42 to, for example, the first arm 32. It is possible.

  The first structure 41 and the first arm 32 of the torque sensor 40 are positioned by a plurality of pins 61 as a first positioning member, and an output shaft 36b-2 of the second structure 42 and the first driving unit 36, which will be described later, is , Are positioned by a plurality of pins 62 as second positioning members. Hereinafter, “positioning” is also referred to as “centering”.

  When the number of the pins 61 is, for example, three, the three pins 61 are arranged at positions of, for example, 0 °, 135 °, and 225 ° on the surface of the torque sensor 40. However, the present invention is not limited to this, and as shown in FIG. 3, when the number of pins 61 is, for example, two, the two pins 61 may be arranged at positions of 0 ° and 180 °.

  The plurality of pins 62 are the same as the pins 61. When the number of the pins 62 is three, the three pins 62 are arranged at positions of, for example, 0 °, 135 °, and 225 ° on the surface of the torque sensor 40. You. When the number of the pins 62 is three, the three pins 62 are arranged at positions of 0 ° and 180 ° as shown in FIG.

The positions of the pin 61 and the pin 62 do not necessarily have to be arranged at the same position, but may be arranged at different positions (angles).
As shown in FIGS. 4 and 5, one end of the pin 61 has, for example, a screw, and one end of the pin 61 is screwed to the first structure 41 of the torque sensor 40. The other end of the pin 61 is inserted into a plurality of first holes 32 a for positioning provided in the first arm 32. The diameter of the first hole 32a is equal to the diameter of the other end of the pin 61. When the pin 61 is inserted into the first hole 32a, the first arm 32 is connected to the first structure 41 of the torque sensor 40. Positioned with respect to.

  The other end of the pin 61 may be pressed into the first hole 32a. Further, in the case of the gap fitting in which the pin 61 is fitted into the first hole 32a so as to have a gap between the pin 61 and the first hole 32a, the contact between the other end of the pin 61 and the first hole 32a is reduced. , It is possible to further reduce other axis interference.

  The pin 62 has a screw at one end similarly to the pin 61. One end of the pin 62 is screwed to the second structure 42 of the torque sensor 40. The other end of the pin 62 is inserted into a plurality of positioning second holes 36b-4 provided on the output shaft 36b-2. The diameter of the second hole 36b-4 is equal to the diameter of the other end of the pin 62. When the pin 62 is inserted into the second hole 36b-4, the output shaft 36b-2 is It is positioned with respect to the two structures 42.

  Similarly to the pin 61, the other end of the pin 62 may be pressed into the second hole 36b-4. Further, in the case of the gap fitting in which the pin 62 is fitted in the second hole 36b-4 so as to have a gap between the pin 62 and the second hole 36b-4, the other end of the pin 62 and the second hole 36b-4 are Is reduced, so that other-axis interference can be further reduced.

  As described above, when the first structure 41 and the first arm 32 of the torque sensor 40 are positioned and the second structure 42 and the output shaft 36b-2 are positioned, the first structure 41 and the first The arm 32 is fixed, and the second structure 42 and the output shaft 36b-2 are fixed.

That is, as shown in FIGS. 3 and 4, a plurality of bolts 51 are inserted into the first arm 32, and these bolts 51 are screwed to the surface of the first structure 41. For this reason, a part of the back surface of the first arm 32 comes into contact with the surface of the first structure 41.
In this state, as shown in FIGS. 4 and 5, the inner surface (hereinafter, simply referred to as a side surface) 32 b of the first arm 32 is formed on the outer peripheral surface of the torque sensor 40, that is, the outer peripheral surface of the first structure 41 ( A gap GP having a predetermined distance is set between the gap GP and the side surface 41a.

As shown in FIGS. 3 and 4, the first structure 41 of the torque sensor 40 is fixed to the first arm 32 by a plurality of bolts 51. That is, the front surface of the first structure 41 is fixed to the back surface of the first arm 32.
The second structure 42 of the torque sensor 40 is connected to the output shaft 36b-2 of the speed reducer 36b by a plurality of bolts 52. That is, the back surface of the second structure 42 is fixed to the surface of the output shaft 36b-2.

  The first driving unit 36 includes, for example, a motor 36a and a speed reducer 36b. The reduction gear 36b includes, for example, a case 36b-1, an output shaft 36b-2, a bearing 36b-3, and a plurality of gears (not shown). The output shaft 36b-2 is connected to the shaft 36a-1 of the motor 36a via a plurality of gears (not shown), and is provided rotatably with respect to the case 36b-1 by bearings 36b-3. The motor 36a is provided on a case 36b-1 of the speed reducer 36b, and the case 36b-1 is fixed to, for example, the base 31 as a second mounting portion.

As described above, after the first structure 41 and the first arm 32 are fixed and the second structure 42 and the output shaft 36b-2 are fixed, the plurality of pins 61 and the pins 62 may be left. Good, but you can remove it.
In the above configuration, when the speed reducer 36b is driven by the motor 36a, a force in the torque (Mz) direction is applied to the torque sensor 40. The first structure 41 of the torque sensor 40 is displaced in the torque (Mz) direction with respect to the second structure 42. When the first structure 41 is displaced with respect to the second structure 42, the torque sensor 40 outputs electric signals from the first strain sensor 44 and the second strain sensor 45, and can detect torque.

  On the other hand, the first structure 41 and the first arm 32 are centered, the second structure 42 and the output shaft 36b-2 are also centered, and the side surface 41a of the first structure 41 of the torque sensor 40 and the first arm 32 A gap GP is provided between the first structural body 41 and the side surface 32b of the first arm 32 and the side surface 32b of the first arm 32 is not in contact. Therefore, when a bending moment or a translational force in a direction other than the torque (Mx, My) is generated in the first arm 32 by the operation of the first arm 32 to the fourth arm 35, the bending moment or the translational force becomes the first arm 32. It does not act directly on the side surface 41a of the structure 41. Therefore, the first structure 41 can be deformed in a well-balanced manner with respect to the second structure 42, and the strain body 44a of the first strain sensor 44 and the strain body 45a of the second strain sensor 45 are symmetric. Deformation. Therefore, it is possible to suppress the output of the detection signal for the bending moment and the translational force in the directions other than the torque (Mx, My), and it is possible to improve the detection accuracy of the torque.

(Effect of First Embodiment)
According to the first embodiment, the first structure 41 and the first arm 32 of the torque sensor 40 are positioned by the pin 61, and are located between the side surface 41a of the first structure 41 and the side surface 32b of the first arm 32. Is provided with a gap GP. That is, the side surface 41a of the first structure 41 and the side surface 32b of the first arm 32 are not in contact with each other. Further, the second structure 42 and the output shaft 36b-2 are positioned by the pins 62, and the center of the output shaft 36b-2 is aligned with the center of the second structure 42. Therefore, when a bending moment or a translational force is applied to the torque sensor 40, the output of the detection signal can be suppressed. Therefore, other-axis interference can be reduced, and the accuracy of torque detection can be improved.

(2nd Embodiment)
6A and 6B show a second embodiment. In the first embodiment, the first structure 41 and the first arm 32 of the torque sensor 40 are positioned by the pins 61, and the second structure 42 and the output shaft 36b-2 are positioned by the pins 62.

In the second embodiment, the first structure 41 and the first arm 32 of the torque sensor 40, and the second structure 42 and the output shaft 36b-2 are positioned by using half-screw bolts instead of the pins 61 and 62. Is performed.
As shown in FIG. 6A, the half screw bolt 63 has a centering portion 63a and a screw portion 63b. The diameter D1 of the centering portion 63a is larger than the diameter D2 of the screw portion 63b.

FIG. 6B shows an example of positioning between the second structure 42 of the torque sensor 40 and the output shaft 36b-2. However, the positioning between the first structure 41 and the first arm 32 can be performed similarly.
As shown in FIG. 6B, the centering of the half screw bolt 63 is performed in the positioning hole 42b of the second structure 42 of the torque sensor 40 and the positioning hole 36b-4 provided in the output shaft 36b-2. The diameter of the centering portion P1 corresponding to the portion 63a is substantially equal to the diameter D1 of the centering portion 63a of the half screw bolt 63, and the screw portion P2 is substantially equal to the diameter D2 of the screw portion 63b of the half screw bolt 63.

  As shown in FIG. 6C, in a state where the half screw bolt 63 is inserted into the hole 42b and the second hole 36b-4, the screw portion 63b of the half screw bolt 63 is screwed into the screw portion P2 of the second hole 36b-4. The centering portion 63a is inserted into the centering portion P1 of the hole 42b and the second hole 36b-4. Therefore, the second structure 42 of the torque sensor 40 and the output shaft 36b-2 are centered.

  The centering of the second structure 42 and the output shaft 36b-2 is performed by the centering portion 63a of the half screw bolt 63. For this reason, even if there is a gap between the screw portion 63b of the half screw bolt 63 and the screw portion P2 of the second hole 36b-4, the second structure 42 and the output shaft are tightened by fastening the half screw bolt 63. The centering state of 36b-2 can be maintained.

  In the case of a clearance fit having a gap between the centering part 63a of the half screw bolt 63 and the centering part P1 of the second hole 36b-4, the centering part 63a of the half screw bolt 63 and the second hole 36b-4 Since contact with the centering portion P1 is reduced, interference with other axes can be further reduced.

The centering of the first structure 41 of the torque sensor 40 and the first arm 32 is similarly performed using the half screw bolt 63. Thereby, a gap GP is provided between the side surface 41a of the first structure 41 and the side surface 32b of the first arm 32.
The arrangement of the half screw bolts 63 for positioning is the same as the arrangement of the pins 61 and 62 in the first embodiment.

The half screw bolt 63 may be left as it is after centering, or may be removed.
Specifically, the torque sensor 40, the first arm 32, and the output shaft 36b-2 may be fixed only by the positioning half screw bolts 63, and the bolts 51 and the bolts 52 need not be fastened.

The torque sensor 40, the first arm 32, and the output shaft 36b-2 are fixed by the half screw bolt 63, and the first arm 32 and the output shaft 36b-2 are fixed to the torque sensor 40 by the bolts 51 and 52. The half screw bolt 63 may be left.
Alternatively, the torque sensor 40, the first arm 32, and the output shaft 36b-2 are fixed by the half screw bolt 63, and the first arm 32 and the output shaft 36b-2 are fixed to the torque sensor 40 by the bolts 51 and 52. After that, the half screw bolt 63 may be removed.

  Alternatively, the torque sensor 40, the first arm 32, and the output shaft 36b-2 are fixed by the half screw bolt 63, and the first arm 32 and the output shaft 36b-2 are fixed to the torque sensor 40 by the bolts 51 and 52. After that, the half screw bolt 63 may be removed, and a normal fastening bolt may be attached instead of the half screw bolt 63.

(Effect of Second Embodiment)
According to the second embodiment, the first structure 41 of the torque sensor 40 and the first arm 32 are positioned using the half screw bolt 63, so that the side surface of the first structure 41 and the first arm 32 are positioned. A gap GP can be provided between the side surface and the center of the second structure 42 and the center of the output shaft 36 b-2 using the half screw bolt 63. Therefore, similarly to the first embodiment, when a bending moment or a translational force is applied to the torque sensor 40, the first structure 41 can be deformed in a well-balanced manner with respect to the second structure 42. Therefore, the torque sensor 40 can reduce the interference between other axes, and can improve the accuracy of detecting the torque.

(First Modification)
FIG. 7 shows a first modification of the first embodiment and the second embodiment.
The first modified example uses a positioning shaft instead of the pins 61 and 62 of the first embodiment and the half screw bolt 63 of the second embodiment, and uses the first structure 41 and the first arm of the torque sensor 40. 32, and the second structure 42 and the output shaft 36b-2 are positioned.

As shown in FIG. 7, a plurality of first holes 32a provided in the first arm 32 and a plurality of positioning holes 41b provided in the first structure 41 of the torque sensor 40 have, for example, columnar shafts. 64 are inserted respectively.
The plurality of positioning holes 36b-4 provided in the output shaft 36b-2 and the plurality of positioning holes 42b provided in the second structure 42 of the torque sensor 40 have, for example, a cylindrical shape. The shafts 65 are inserted respectively.

In this way, the first structure 41 and the first arm 32 of the torque sensor 40 are positioned by the plurality of shafts 64, and the second structure 42 and the output shaft 36b-2 are positioned by the plurality of shafts 65. .
After fastening the bolts 51 and 52, the shafts 64 and 65 are removed, for example ,. However, it is also possible to keep it.

According to the first modification, it is possible to obtain the same effects as those of the first embodiment and the second embodiment. In addition, since the positioning can be performed using the shaft 64 and the shaft 65 having a simple configuration, the assembling work can be simplified.
(Second Modification)
FIG. 8 shows a second modification. FIG. 8 is a modification of FIG. 6C.

As shown in FIG. 8, the cylinder 70 is inserted into the centering portion P1 of the hole 42b and the second hole 36b-4. The cylinder 70 is made of, for example, metal, but may be made of resin.
In a state where the half screw bolt 63 is inserted into the inside of the tube 70, the screw portion 63b of the half screw bolt 63 is screwed into the screw portion P2 of the second hole 36b-4, and the centering portion 63a is arranged in the tube 70. Is done. Therefore, the second structure 42 of the torque sensor 40 and the output shaft 36 b-2 are centered by the cylinder 70 and the half screw bolt 63.

The centering portion 63a of the half screw bolt 63 and the cylinder 70 may be a gap fit having a gap GP.
According to the second modification, the same effect as that of the second embodiment can be obtained.
In addition, the present invention is not limited to the above embodiments as they are, and can be embodied by modifying the constituent elements in an implementation stage without departing from the scope of the invention. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Further, components of different embodiments may be appropriately combined.

  40 torque sensor, 41 first structure, 42 second structure, 43 third structure, 44 first strain sensor, 45 second strain sensor, 32 first arm (first mounting part) ), 31 base (second mounting portion), 41a side surface, 32b side surface, 32a first hole, 36b-4 second hole, 61 pin (first positioning member) 62 pin (second Positioning member), 63: half screw bolt, 64, 65: shaft, 70: cylinder.

Claims (8)

A first structure;
A second structure;
A third structure provided between the first structure and the second structure;
At least two sensor units provided between the first structure and the second structure;
A plurality of first holes provided in the first structure for positioning a first mounting portion;
A plurality of second holes provided in the second structure for positioning a second mounting portion;
A torque sensor comprising:   The torque sensor according to claim 1, further comprising a plurality of first positioning members inserted into the first hole for positioning the first mounting portion.   The torque sensor according to claim 2, further comprising a plurality of second positioning members inserted into the second hole for positioning the second mounting portion.   The torque sensor according to claim 3, wherein the first positioning member and the second positioning member are pins.   The torque sensor according to claim 3, wherein the first positioning member and the second positioning member are half-thread bolts.   The torque sensor according to claim 3, wherein the first positioning member and the second positioning member are shafts. The first positioning member and the second positioning member, a cylinder inserted into the first hole or the second hole,
4. The torque sensor according to claim 3, wherein the torque sensor is a half screw bolt inserted into the cylinder.   The torque according to any one of claims 4 to 7, wherein the first positioning member and the second positioning member are clearance fits having a clearance between the first hole and the second hole. Sensor.

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