JP2008107300A - Acceleration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acceleration sensor capable of detecting accelerations in the directions of the three axes of an X-axis, a Y-axis, and a Z-axis with high precision, respectively. <P>SOLUTION: The acceleration sensor 1 is formed by having a frame-shaped beam portion 4 arranged being floated above an XY substrate surface of a base 2, a beam-portion support fixing portion for supporting the beam portion 4 via support portions 5a, 5b like a fixed beam by linkage to the base 2, weight portions 7 arranged being floated above the XY substrate surface of the base 2, and link portions 8 for supporting the weight portions 7, such as a cantilever beam by linkage to the beam portion 4. The weight portions 7 are structured so as to be displaceable in the directions of the three axes of the X-axis, Y-axis, and Z-axis by the deflection of the frame-shaped beam portion 4. The beam portion 4 is provided with an X-axis direction acceleration detection portion for detecting the X-axis direction acceleration, the Y-axis direction acceleration detection portion for detecting the Y-axis direction acceleration, and a Z-axis direction acceleration detection portion for detecting a Z-axis direction acceleration. Moreover, the beam portion 4 is provided with slits for improving the sensitivity of acceleration detection. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an acceleration sensor capable of detecting accelerations in three axial directions, ie, an X-axis direction, a Y-axis direction, and a Z-axis direction, which are orthogonal to each other.

FIG. 15 shows an example of an acceleration sensor in a schematic perspective view (see, for example, Patent Document 1). The acceleration sensor 40 includes a frame portion 41, a columnar weight body 42 disposed at the center of the frame portion 41, and both sides of the weight body 42 in the X-axis direction along the X-axis direction. The X-axis direction beam portions 43a and 43b that are extended toward the frame portion 41 and the Y-axis direction from both sides of the weight body 42 are extended toward the frame portion 41 along the Y-axis direction. Y-axis beam portions 44a and 44b, four auxiliary weight bodies 45a to 45d connected to the weight body 42, and resistance elements R _{X1 to} R- _X formed on the X-axis beam portions 43a and 43b. _X4 , R _{Z1 to} R _Z4 and resistance elements R _{Y1 to} R _Y4 formed in the Y-axis direction beam portions 44a and 44b.

  In the configuration of the acceleration sensor 40 shown in FIG. 15, the central axes of the X-axis direction beam portions 43 a and 43 b are arranged on the same straight line extending along the X-axis direction through the central axis of the cylindrical weight body 42. The central axes of the Y-axis direction beam portions 44a and 44b are arranged on the same straight line extending along the Y-axis direction through the central axis of the weight body 42. These X-axis direction beam portions 43a and 43b and Y-axis direction beam portions 44a and 44b are each configured to be able to bend and deform.

The resistance elements R _X1 and R _X2 are arranged in the X-axis direction beam portion 43a along the X-axis direction, and the resistance elements R _X3 and R _X4 are arranged in the X-axis direction beam portion 43b along the X-axis direction. Yes. The resistance elements R _Y1 and R _Y2 are arranged in the Y axis direction beam portion 44a along the Y axis direction, and the resistance elements R _Y3 and R _Y4 are arranged in the Y axis direction beam portion 44b along the Y axis direction. Yes. The resistance elements R _Z1 and R _Z2 are arranged in the X-axis direction beam portion 43a along the X-axis direction, and the resistance elements R _Z3 and R _Z4 are arranged in the X-axis direction beam portion 43b along the X-axis direction. Yes. These resistance elements R _{X1 to} R _X4 , R _{Y1 to} R _Y4 , and R _{Z1 to} R _Z4 are respectively caused by stress changes in the beam portions 43a, 43b, 44a, and 44b due to bending deformation of the beam portions 43a, 43b, 44a, and 44b. The electrical resistance value changes.

Four resistance elements R _{X1 to} R _X4 form a bridge circuit as shown in FIG. 16A, and four resistance elements R _{Y1 to} R _Y4 form a bridge circuit as shown in FIG. In addition, the four resistance elements R _{Z1 to} R _Z4 are connected to the beam portions 43a, 43b, 44a, 44b and the frame portion 41 to form a bridge circuit as shown in FIG. Is provided. 16 (a) to 16 (c) indicates a voltage power supply input section connected to an external voltage power supply, and reference numerals P _X1 , P _X2 , P _Y1 , P _Y2 , P _Z1. , P _Z2 indicate voltage detection units, respectively.

  Each of the weight body 42 and the auxiliary weight bodies 45a to 45d is in a floating state, and can be displaced by bending deformation of the beam portions 43a, 43b, 44a, and 44b. For example, when a force in the X-axis direction due to acceleration in the X-axis direction acts on the weight body 42 and the auxiliary weight bodies 45a to 45d, the weight body 42 and the auxiliary weight bodies 45a to 45d are moved by the force to the X-axis. Displaces in the direction. Similarly, when a force in the Y-axis direction due to acceleration in the Y-axis direction acts on the weight body 42 and the auxiliary weight bodies 45a to 45d, the weight body 42 and the auxiliary weight bodies 45a to 45d are caused by the force. Displacement is shaken in the Y-axis direction. Similarly, when a force in the Z-axis direction due to acceleration in the Z-axis direction acts on the weight body 42 and the auxiliary weight bodies 45a to 45d, the weight body 42 and the auxiliary weight bodies 45a to 45d are caused by the force. Displacement is shaken in the Z-axis direction. The beams 43a, 43b, 44a, and 44b are bent and deformed by the displacement of the weight body 42 and the auxiliary weight bodies 45a to 45d.

In the acceleration sensor 40, the resistance elements R _{X1 to} R _X4 , R _{Y1 to} R _Y4 , R are generated by the stress generation of the beam portions 43a, 43b, 44a, 44b due to the bending deformation of the beam portions 43a, 43b, 44a, 44b as described above. the resistance value of _Z1 to R _Z4 is changed. Due to the change in the resistance value of the resistance element, the balance of the resistance values of the four resistance elements of the bridge circuits in FIGS. 16A to 16C is lost, and the X axis direction, the Y axis axis, and the Z axis direction. The magnitude of acceleration can be detected.

For example, when acceleration in the X-axis direction is generated, a difference is generated between the voltages output from the voltage detection units P _X1 and P _X2 of the bridge circuit in FIG. The magnitude of acceleration in the X-axis direction can be detected using this voltage difference. Further, when acceleration in the Y-axis direction is generated, there is a difference between the voltages output from the voltage detection units P _Y1 and P _Y2 of the bridge circuit in FIG. The magnitude of acceleration in the Y-axis direction can be detected using this voltage difference. Furthermore, when acceleration in the Z-axis direction is generated, a difference is generated between the voltages output from the voltage detection units P _Z1 and P _Z2 of the bridge circuit in FIG. The magnitude of acceleration in the Z-axis direction can be detected using this voltage difference.

JP 2002-296293 A

  However, in the configuration of the acceleration sensor 40 shown in FIG. 15, linear beam portions 43 a, 43 b, 44 a, 44 b are arranged on four sides of the weight body 42, and the weight body 42 is connected to the frame portion 41. is doing. For this reason, when the frame 41 is distorted by thermal stress, the beams 43a, 43b, 44a, 44b are distorted along with the distortion of the frame 41, and the beams 43a, 43b, 44a, 44b are distorted. Compressive stress and tensile stress occur.

That is, since the resistance elements R _{X1 to} R _X4 , R _{Y1 to} R _Y4 , and R _{Z1 to} R _Z4 for detecting acceleration are respectively provided in the beam portions 43a, 43b, 44a, and 44b, the acceleration is increased. In spite of not occurring, the resistance elements R _{X1 to} R _X4 , R _{Y1 to} R _Y4 , R _Z1 are generated by the stress generation of the beam portions 43a, 43b, 44a, 44b due to the distortion caused by the thermal stress of the frame portion 41. electrical resistance of the to R _Z4 is changed. As a result, the voltage at the time of acceleration may be output from the bridge circuit shown in FIGS. 16A to 16C even though no acceleration occurs.

The acceleration sensor 40 has acceleration detection resistance elements R _{X1 to} R _X4 , R _{Y1 to} R _Y4 , R on beam portions 43 a, 43 b, 44 a, and 44 b that are formed to extend in four directions of the weight body 42. a configuration in which the _Z1 to R _Z4, arrangement positions of the resistance element is dispersed. For example, when the beam portions 43a, 43b, 44a, and 44b are made of silicon, phosphorus (P) and boron (B) are doped in the resistive element arrangement positions in the beam portions 43a, 43b, 44a, and 44b. Thus, the resistance elements R _{X1 to} R _X4 , R _{Y1 to} R _Y4 , and R _{Z1 to} R _Z4 that are piezoresistors are formed.

  In this case, if the resistance element arrangement positions are dispersed, it is difficult to dope phosphorus and boron uniformly to each resistance element arrangement position, and the doping concentration at each resistance element arrangement position varies. For this reason, it is difficult to balance the resistance values of the four resistance elements of each bridge circuit shown in FIGS. 16A to 16C, thereby causing a problem of preventing improvement in acceleration detection accuracy.

  The present invention has been made to solve the above-described problems, and the object thereof is not easily affected by thermal stress or the like, and is arranged in three axes of the X-axis direction, the Y-axis direction, and the Z-axis direction with one element. An object of the present invention is to provide an acceleration sensor capable of detecting each acceleration with high accuracy.

In order to achieve the above object, the present invention solves the above problems with the following configuration. That is, this invention
The base,
A frame-shaped beam portion arranged in a floating state on the surface of the base;
The beam portion is attached to the base via support portions that are formed to extend outward on both sides of the beam portion along the X-axis direction of the X-axis, the Y-axis, and the Z-axis that are orthogonal to each other from the beam portion. A beam support and fixing portion that supports the beam,
A connecting portion that is formed to extend outward along the Y-axis direction from both sides in the Y-axis direction of the beam portion in a state of floating on the surface of the base;
A weight portion connected to the extending tip of each connecting portion;
Have
The weight portion is configured to be displaceable in three axial directions of the X-axis direction, the Y-axis direction, and the Z-axis direction by deformation of the frame-shaped beam portion,
In the beam part,
An X-axis direction acceleration detection unit for detecting an acceleration in the X-axis direction based on the bending deformation of the beam portion caused by the displacement of the weight portion in the X-axis direction;
A Y-axis direction acceleration detection unit for detecting an acceleration in the Y-axis direction based on a bending deformation of the beam part due to a displacement in the Y-axis direction of the weight part;
A Z-axis direction acceleration detection unit for detecting an acceleration in the Z-axis direction based on the bending deformation of the beam portion caused by the Z-axis direction displacement of the weight part;
Is provided,
Further, the frame-shaped beam portion is characterized in that a slit for improving sensitivity is formed at positions symmetrical to each other with respect to the X axis and the Y axis at the center of the beam portion.

  According to this invention, the frame-shaped beam portion is supported by the base in the form of a cantilever beam via the support portions that are formed to extend outward on both sides of the beam portion along the X-axis direction. The configuration. For this reason, for example, when the base is distorted by thermal stress, the distortion in the Y-axis direction (for example, the longitudinal direction) is absorbed by the bending deformation of the support portion. In addition, the distortion in the X-axis direction (for example, the short direction) is small in absolute displacement due to the distortion, and the beam part region separated from the beam part region connected to the support part and the connecting part responds to the distortion in the X-axis direction. It is deformed and the distortion is absorbed. For this reason, it can prevent that distortion arises in the connection site | part and its adjacent area | region with a support part in a beam part, and the connection site | part and its adjacent area | region with a connection part in a beam part.

  For example, when the base is distorted due to thermal stress or the like, an X for detecting acceleration based on the distortion of the beam in the above-described beam area where no distortion occurs due to the distortion of the base. By forming the axial direction acceleration detection unit, the Y-axis direction acceleration detection unit, and the Z-axis direction acceleration detection unit, a situation of erroneous detection of acceleration due to distortion due to thermal stress of the base (that is, no acceleration has occurred) Despite this, a false detection situation in which acceleration is detected by the X-axis direction acceleration detection unit, the Y-axis direction acceleration detection unit, and the Z-axis direction acceleration detection unit due to distortion due to thermal stress of the base) Can be suppressed.

  In addition, the present invention has a simple structure in which the frame-shaped beam portion is supported by the base in the form of a cantilever beam, and the weight portion is supported in a cantilever shape by the beam portion, thereby reducing the size. Easy to promote.

  Further, according to the present invention, the weight portion is connected to the frame-like beam portion in a cantilever shape. For this reason, the displacement of the weight portion due to the acceleration is increased, whereby the bending deformation of the beam portion due to the displacement of the weight portion is increased, and the sensitivity of acceleration detection can be increased.

  Furthermore, in this invention, the slit for sensitivity improvement is formed in the beam part. For this reason, the substantial beam width of the beam portion in the slit forming portion is narrowed, and thereby the bending deformation of the beam portion due to the generation of acceleration is further increased, so that the sensitivity of acceleration detection can be further enhanced. As described above, since the sensitivity of acceleration detection can be increased simply by forming a slit in the beam portion, it is not necessary to increase the size of the acceleration sensor in order to increase the sensitivity of acceleration detection, and the variation in sensitivity of acceleration detection is suppressed. be able to.

  Furthermore, in the present invention, the sensitivity improving slit is provided at a position symmetrical to each other with respect to the X axis and the Y axis at the center of the beam portion. The problem that the bending deformation of the beam portion becomes complicated can be prevented.

  Furthermore, the durability of a beam part can be improved by providing the structure where the slit for a sensitivity improvement is each provided in the both sides of the connection part connection site | part of a beam part. In other words, both sides of the connecting portion connecting portion of the beam portion are portions where stress due to distortion of the beam portion due to displacement of the weight portion is concentrated. By forming a slit in the part, stress concentration in the part can be relaxed. For this reason, it is possible to suppress deterioration in both side portions of the connecting portion connecting portion of the beam portion due to the stress concentration, and it is possible to improve the durability of the beam portion.

  When there are portions where the conductive paths are wired side by side with each other in the beam part, the slits for improving the sensitivity are provided between the conductive paths wired side by side so that they are wired side by side. Since a gap is provided between the conductive paths, the insulation between the conductive paths can be enhanced.

  Furthermore, the central axes of the support portions that are formed extending in the X-axis direction from both sides of the beam portion in the X-axis direction are arranged on the same straight line, and from both sides of the beam portion in the Y-axis direction, respectively in the Y-axis direction. The central axes of the connecting portions that are formed to extend in the same manner are arranged on the same straight line, and the beam portion has a symmetrical shape with respect to the X-direction center line passing through the central axis of the support portion, and the connecting portions By providing a configuration that is also symmetrical with respect to the Y-direction center line passing through the central axis of the beam, it is possible to simplify the bending deformation of the beam portion due to the occurrence of acceleration, and use the stress change due to the bending deformation of the beam portion. This can contribute to improving the accuracy of acceleration detection.

  Furthermore, by providing a structure in which a reinforcing portion that is formed to extend in a direction connecting the support portions on both sides of the beam portion is arranged in the frame space of the frame-shaped beam portion, the rigidity of the beam portion is increased by the reinforcing portion. For example, the bending deformation of the beam part due to distortion of the base or the fixing part can be suppressed to a small level.

  Furthermore, each of the Z-axis direction acceleration detection unit, the Y-axis direction acceleration detection unit, and the X-axis direction acceleration detection unit provided in the beam part changes in electric resistance value due to a stress change of the beam part due to deformation of the beam part. By having a configuration configured to have a piezoresistive portion, it is possible to easily and accurately detect the change in the electric resistance value of the piezoresistive portion, in an X axis direction, a Y axis direction, and a Z axis direction. The acceleration of each can be detected.

  Embodiments according to the present invention will be described below with reference to the drawings.

  1A is a schematic perspective view showing an embodiment of an acceleration sensor according to the present invention, and FIG. 1B is a schematic plan view of the acceleration sensor of FIG. The figure is shown with the electrode pad indicated by reference numeral 18 in FIG. 2A shows a schematic cross-sectional view of the aa portion of FIG. 1B, and FIG. 2B shows a schematic of the bb portion of FIG. 1B. A schematic cross-sectional view is shown, and FIG. 2C shows a schematic cross-sectional view of a portion cc of FIG. 1B. Further, FIG. 3A shows a schematic cross-sectional view of the AA portion of FIG. 1B, and FIG. 3B shows a schematic of the BB portion of FIG. 1B. A schematic cross-sectional view is shown, and FIG. 3C is a schematic cross-sectional view of the CC portion of FIG. 1B.

  The acceleration sensor 1 according to this embodiment is capable of detecting accelerations in three axial directions, ie, an X axis, a Y axis, and a Z axis, which are orthogonal to each other. The acceleration sensor 1 has a base 2. The base 2 has an XY substrate surface 3 parallel to an XY plane including the X axis and the Y axis, and a frame-like beam portion 4 is disposed above the XY substrate surface 3 in a floating state. Yes. The frame-shaped beam portion 4 has a substantially rectangular XY plane shape, and the support portions 5 (5a, 5b) extend outwardly along the X-axis direction from both sides of the beam portion 4 in the X-axis direction. Is formed.

  These support portions 5a and 5b are in a state of floating with respect to the base 2, and the extending tip portions of the support portions 5a and 5b are the longitudinal lengths of the elastic portions 25 formed by beams (stress reducing beams) 26. It is connected to the center of the direction. The connecting portions of the support portions 5a and 5b to the beam portion 4 are formed in a tapered shape whose diameter increases toward the beam portion 4 side, and the support portions 5a and 5b are connected to the frame-shaped beam portion 4. The width of the extending side is formed wider than the width of the extending tip side from the beam part 4 (side connected to the elastic part 25).

  Further, the beam 26 forming the elastic portion 25 (25a, 25b) extends in a direction (in this example, the orthogonal Y-axis direction) intersecting the extension forming direction (X-axis direction) of the support portion 5 (5a, 5b). The formed distal end side is fixed to the fixing portion 6. The fixing part 6 has a frame-like form surrounding a beam part 4 and a formation area of a weight part 7 (7a, 7b), which will be described later, with a space therebetween, and the fixing part 6 is fixed to the base 2. .

  In this embodiment, the beam portion 4 is fixed to the fixing portion 6 via the support portion 5 (5a, 5b) and the elastic portion 25. In other words, the beam portion 4 is supported and fixed in a doubly supported beam shape on the base 2 via the support portions 5 a and 5 b and the elastic portion 25. That is, in this embodiment, the beam support / fixing portion is configured by the support portion 5 (5a, 5b), the elastic portion 25, and the fixing portion 6.

  Further, in the frame space of the frame-shaped beam portion 4, reinforcing portions 20 that are formed to extend in a direction connecting the support portions 5 a and 5 b on both sides of the beam portion 4 are disposed, and both end sides of the reinforcing portion 20 are framed, respectively. Connected to the beam-shaped beam portion 4. The reinforcing part 20 includes a part M (see FIG. 1B) of the beam part 4 to which the support part 5a is connected and a part N of the beam part 4 to which the support part 5b is connected (see FIG. 1B). And both ends of the reinforcing portion 20 are respectively connected to the inner edge of the beam portion 4. In this embodiment, the width of the reinforcing portion 20 in the Y-axis direction is formed to be equal to the width of the support portions 5a and 5b on the connection side to the beam portion 4.

  The weight portions 7 a and 7 b are arranged and arranged in the Y-axis direction with the beam portion 4 interposed therebetween, and are arranged in a state of floating above the XY substrate surface 3 of the base 2. Each of the weight portions 7a and 7b is connected to the beam portion 4 by connecting portions 8 (8a and 8b) extending outward from the both sides of the beam portion 4 in the Y-axis direction. Has been. The connecting portion 8 (8a, 8b) is in a floating state with respect to the base 2, and the weight portions 7a, 7b are moved in the X-axis direction, the Y-axis direction, and the Z-axis direction by the bending deformation of the beam portion 4. The structure is displaceable in the axial direction.

  In this embodiment example, the central axes along the X-axis direction of the support portions 5a and 5b and the reinforcing portion 20 are arranged on the same straight line, and the central axes along the Y-axis direction of the connection portions 8a and 8b. Are arranged on the same straight line. The beam portion 4 has a symmetrical shape with respect to the X-direction central axis passing through the central axes of the support portions 5a and 5b, and a symmetrical shape with respect to the Y-direction central axis passing through the central axes of the connecting portions 8a and 8b. It has become.

Further, in the frame-shaped beam portion 4, the support portions 5a, Y-axis direction extending portion 4a from the supporting position is extended in the Y-axis direction by 5b, an area surrounded by a dotted line Y ₄ of 4b (FIGS. 4 (a) Reference) is formed such that the width on the extension distal end side is narrower than the width on the extension proximal end side. More specifically, each of the Y-axis direction extension portions 4a and 4b is formed in a straight shape in which the width of the beam portion 4 is wide from the base end side to the vicinity of the center portion in the extension direction in the Y-axis direction. In the vicinity of the central portion in the extending direction, the beam width becomes narrower toward the extending tip side, and the beam portion 4 has a straight shape having a narrow width from the tapered tip to the extending tip portion in the Y-axis direction. Is formed.

In this embodiment, in the beam portion 4, the connecting portion connecting portion, that is, the connecting portion side band-like beam portion extending from the connecting portions 8 a and 8 b to the region of the beam portion 4 with the width of the connecting portion 8 in the Y-axis direction. Z-axis direction of the thickness of the part 15 (15a, 15b) (see area surrounded by a dotted line Z ₁₅ in FIG. 4 (b)), have the same thickness as the Z-axis direction of the thickness of the connecting portion 8. Further, the support portion side belt-like beam portion portion 16 (16a, 16b) extending in the X-axis direction from the support portions 5a, 5b to the region of the beam portion 4 with a width on the base end side of the support portions 5a, 5b, respectively (FIG. 4). Z-axis direction of the thickness of the reference) a region surrounded by the dotted line Z ₁₆ in (b) has a same thickness as the Z-axis direction of the thickness of the support portion 5.

  In this embodiment example, the thickness in the Z-axis direction of the connecting portion side belt-like beam portion 15 (15a, 15b) and the support portion side belt-like beam portion 16 (16a, 16b) in the beam portion 4 is, for example, about 400 μm. On the other hand, the thickness in the Z-axis direction of the other part of the beam part 4 is about 5 to 10 μm, for example, and the thickness in the Z-axis direction of the other part of the beam part 4 is the beam part. 4 is thinner than the thickness in the Z-axis direction of the connecting portion side band-shaped beam portion 15 (15a, 15b) and the support portion side band-shaped beam portion 16 (16a, 16b).

  In addition, in the beam part 4, the connecting part side belt-like beam part part 15 (15a, 15b) is not made thick, and the connecting part side belt part 15 (15a, 15b) is the support part side belt part 16. The thickness other than (16a, 16b) may be the same as the thickness in the Z-axis direction. Further, the thickness of the connecting portions 8a and 8b may be the same as the thickness in the Z-axis direction of the portion other than the support portion side band-like beam portion portion 16 (16a and 16b). As described above, when the thickness of the connecting portions 8a and 8b and the thickness of the connecting portion side belt-like beam portion 15 (15a and 15b) are thinly formed, for example, about 5 to 10 μm, FIG. 3) is a cross-sectional view taken along the line CC of FIG. 3 (d).

  In this embodiment, the thickness of the reinforcing portion 20 in the Z-axis direction and the thickness of the beam 26 in the Z-axis direction are also the same as those of the support portions 5a and 5b and the support portion side belt-like beam portion portion 16 in the beam portion 4. It is thick.

  Further, in this embodiment, the thickness of the weight portion 7 in the Z-axis direction is substantially the same as the thickness of the support portion 5 and the connecting portion 8 in the Z-axis direction, for example, about 400 μm. Further, the center of gravity of the weight portion 7 (7a, 7b) is, for example, the position of a point W7 shown in FIG. 3B, and the fulcrum of the beam portion 4 that supports the weight portion 7 (7a, 7b) is, for example, FIG. It is the position of the point W4 shown in (b), and the position of the center of gravity of the weight part 7 and the fulcrum position of the beam part 4 that supports the weight part 7 (7a, 7b) are the height position (in the Z-axis direction). Position) is off.

  In this embodiment, as shown in the enlarged views of FIGS. 4A and 4B, the beam portion 4 has a slit 17 for improving sensitivity, which is a connecting portion side band-like beam. It is provided on each side of each part 15 (15a, 15b). That is, in this embodiment example, the position and shape of each sensitivity improving slit 17 are symmetrical with respect to the X-direction central axis passing through the central axis of the support portions 5a and 5b in the beam portion 4, and The Y-direction central axis passing through the central axes of the connecting portions 8a and 8b is also symmetric. 1, 5, and 7 to 13 show the beam portion 4, but the illustration of the slit 17 for improving sensitivity is omitted in these drawings.

In this embodiment, the beam part 4, the support part 5 (5a, 5b), the fixing part 6, the weight part 7 (7a, 7b) and the connection part 8 (8a, 8b) described above are SOI (Silicon-On-On). Insulator) is formed by processing a substrate (that is, a multilayer substrate in which the Si layer 10, the SiO ² layer 11, and the Si layer 12 are sequentially laminated) using a micromachining technique.

In this embodiment, a piezoresistive part for detecting acceleration by processing the following part of the beam part 4 made of Si is provided. That is, as shown in the schematic enlarged view of FIG. 5, in the beam portion 4, the piezoresistive portions R _X1 and R _X2 are arranged on both sides of the band width of the connecting portion side band-shaped beam portion portion 15 a. In addition, piezoresistive portions R _X3 and R _X4 are disposed on both sides of the band width of the connecting portion side band-shaped beam portion 15b. These four piezoresistive portions R _X1 , R _X2 , R _X3 , R _X4 constitute an X-axis direction acceleration detection unit for detecting acceleration in the X-axis direction.

Further, in the beam portion 4, piezoresistive portions R _Y2 and R _Y3 are arranged near the extending tip side of the Y-axis direction extending portion 4a, and the piezoresistive portion R _{Y1 is positioned} near the extending tip side of the Y-axis direction extending portion 4b. , R _Y4 are arranged respectively. These four piezoresistive portions R _Y1 , R _Y2 , R _Y3 , R _Y4 constitute a Y-axis direction acceleration detection unit for detecting acceleration in the Y-axis direction.

Further, piezoresistive portions R _Z2 and R _Z3 are formed on both ends of the support-side belt-like beam portion 16a, which is closer to the extension base end side of the Y-axis direction extension portion 4a in the beam portion 4, and extends in the Y-axis direction. Piezoresistive portions R _Z1 and R _Z4 are formed on both ends of the support-side belt-like beam portion 16b, which is closer to the extended base end side of the portion 4b. These four piezoresistive portions R _Z1 , R _Z2 , R _Z3 , R _Z4 constitute a Z-axis direction acceleration detection unit for detecting acceleration in the Z-axis direction. The piezoresistive portions R _Z1 and R _Z3 have a shape that extends along the X-axis direction, and the piezoresistive portions R _Z2 and R _{Z4 intersect with} the direction in which the piezoresistive portions R _Z1 and R _Z3 extend. The shape is formed to extend along the axial direction.

The beam portion 4, the support portion 5 (5a, 5b), the reinforcing portion 20, the elastic portion 25, and the fixed portion 6 are respectively provided with piezoresistive portions R _X1 , R _X2 , R as shown in FIG. A wiring pattern for configuring a bridge circuit by _X3 and R _X4 and a wiring for configuring a bridge circuit by piezoresistive portions R _Y1 , R _Y2 , R _Y3 , and R _Y4 as shown in FIG. A pattern and a wiring pattern for forming a bridge circuit with piezoresistive portions R _Z1 , R _Z2 , R _Z3 , R _Z4 as shown in FIG. 6C are formed.

  In this embodiment, when the acceleration is not generated, the resistance values of the four piezoresistors constituting each bridge circuit of FIGS. 6A to 6C are in an equilibrium state. A piezoresistive portion is formed.

  For example, FIG. 7A schematically shows one wiring example of the wiring pattern. In this example, as shown in the schematic cross-sectional view of FIG. 7B, for example, a wiring pattern Ls formed by doping the Si layer 12 of the SOI substrate 13 with boron, phosphorus or the like, and the SOI substrate 13 A bridge circuit composed of a piezoresistive portion is constituted by a wiring pattern Lm made of metal such as aluminum formed on the surface by using a film forming technique such as vapor deposition or sputtering. In FIG. 7A, the wiring pattern Ls is represented by a solid line, and the wiring pattern Lm is represented by a broken line.

  In the example of FIG. 7A, the following unique wiring patterns Ls and Lm are formed using the characteristics of the wiring pattern Ls and the wiring pattern Lm. That is, as shown in FIG. 7B, an oxide film 21 is inevitably formed on the surface of the Si layer 12 of the SOI substrate 13 after the wiring pattern Ls is formed. A cross wiring is formed between the wiring pattern Ls and the wiring pattern Lm while ensuring insulation between the wiring pattern Ls and the wiring pattern Lm.

  Further, a part of the oxide film 21 where the wiring pattern Ls is formed is removed to form a hole 22, and a conductor material of the constituent material of the wiring pattern Lm enters the hole 22 to form the wiring pattern Ls. As a result, the wiring pattern Ls and the wiring pattern Lm are electrically connected.

  In this embodiment, as described above, the support portions 5a and 5b, the connecting portion side beam portions 15a and 15b and the support portion side beam portions 16a and 16b in the beam portion 4, and the reinforcing portion 20 are provided. The elastic portion 25 has a thickness of about 400 μm, for example. On the other hand, the parts of the beam part 4 other than the connecting part side belt-like part 15a, 15b and the support part side belt-like part 16a, 16b have a thickness of about 5 to 10 μm, for example. If a metal wiring pattern Lm is formed on the surface of such a thin portion of the beam portion 4, the thin portion of the beam portion 4 may be warped by the internal stress of the wiring pattern Lm. In contrast, the wiring pattern Ls is formed by doping the Si layer constituting the beam portion 4 with an impurity such as boron or phosphorus, and the beam portion 4 is thin due to the formation of the wiring pattern Ls. Almost no deformation such as warping of the portion occurs. For this reason, it is avoided to form the metal wiring pattern Lm in the thin part of the beam part 4, and the wiring pattern Ls is formed in the thin part of the beam part 4.

  That is, in the example of FIG. 7A, the wiring pattern Ls and the wiring pattern Lm can be cross-wired and the electrical connection between the wiring pattern Ls and the wiring pattern Lm is easy. The wiring configuration of the wiring pattern Ls and the wiring pattern Lm is designed in consideration of the simplification of the wiring configuration of the wiring pattern, considering that the thickness of the beam portion 4 is partially different.

In this wiring example, one end sides of the piezoresistive portions R _X1 and R _X2 disposed on both sides of the band width of the connecting portion side beam portion 15a are electrically connected by the wiring pattern Ls, and the voltage detecting portion P _X1 is formed. As shown in FIG. 1A, a plurality of electrode pads 18 for external connection are formed on the surface of the fixed portion 6. The voltage detection unit P _X1 is electrically connected to external connection electrode pads 18 (V _X1 ) individually corresponding to the voltage detection unit P _X1 by wiring patterns Ls and Lm. Similarly, one end sides of the piezoresistive portions R _X3 and R _X4 arranged on both sides of the band width of the connecting portion side band-shaped beam portion 15b are electrically connected to each other by the wiring pattern Ls so that the voltage detecting portion P _X2 is connected. The voltage detection unit P _X2 is electrically connected to the external connection electrode pad 18 (V _X2 ) individually corresponding to the voltage detection unit P _X2 by the wiring patterns Ls and Lm.

In addition, the other end sides of the piezoresistive portions R _X2 and R _X4 are electrically connected to an external connection electrode pad 18 (V _VS ) for connection to an external voltage power source Vs by wiring patterns Ls and Lm, respectively. It is connected. Further, the other end sides of the piezoresistive portions R _X1 and R _X3 are electrically connected to an external connection electrode pad 18 (GND) for connection to an external ground GND by wiring patterns Ls and Lm, respectively. ing.

Furthermore, the one end sides of the piezoresistive portions R _Y2 and R _Y3 arranged near the extending tip side of the Y-axis direction extending portion 4a are electrically connected by the wiring patterns Ls and Lm, and the voltage detecting portion P _Y1 Is formed. The voltage detection unit P _Y1 is the wiring pattern Lm, are electrically connected to the electrode pads 18 for external connection corresponding individually to the voltage detection unit P _Y1 (V _Y1).

Similarly, one end sides of the piezoresistive portions R _Y1 and R _Y4 arranged near the extending tip side of the Y-axis direction extending portion 4b are electrically connected to each other by the wiring patterns Ls and Lm so that the voltage detecting portion P is connected. _Y2 is formed. The voltage detection unit P _Y2 is the wiring pattern Lm, are electrically connected to the electrode pads 18 for external connection corresponding individually to the voltage detection unit P _Y2 (V _Y2).

The other end sides of the piezoresistive portions R _Y2 and R _Y4 are electrically connected to an external connection electrode pad 18 (V _VS ) for connection to an external voltage power source Vs by wiring patterns Ls and Lm, respectively. It is connected. Further, the other end sides of the piezoresistive portions R _Y1 and R _Y3 are electrically connected to an external connection electrode pad 18 (GND) for connection to an external ground GND by wiring patterns Ls and Lm, respectively. ing.

Furthermore, one end sides of the piezoresistive portions R _Z2 and R _Z3 on both ends of the support portion side beam portion 16a are electrically connected by the wiring pattern Ls to form a voltage detection portion P _Z1 . The voltage detection unit P _Z1 is by a wiring pattern Lm, it is electrically connected to the electrode pads 18 for external connection corresponding individually to the voltage detection unit P _Z1 (V _Z1). Similarly, one end sides of the piezoresistive portions R _Z1 and R _Z4 on both ends of the support portion side beam portion 16b are electrically connected by the wiring pattern Ls to form a voltage detection portion P _Z2 . . The voltage detection unit P _Z2 is the wiring pattern L, and is electrically connected to the electrode pads 18 for external connection corresponding individually to the voltage detection unit P _Z2 (V _Z2).

Further, the other end sides of the piezoresistive portions R _Z2 and R _Z1 are electrically connected to an external connection electrode pad 18 (V _VS ) for connection to an external voltage power source Vs by wiring patterns Ls and Lm, respectively. It is connected. Further, the other end sides of the piezoresistive portions R _Z3 and R _Z4 are electrically connected to an external connection electrode pad 18 (GND) for connection to an external ground GND by wiring patterns Ls and Lm, respectively. ing.

  In the example of FIG. 7A, the beam portion 4 is provided for the piezoresistive portion as described above for constituting an X-axis direction acceleration detection portion, a Y-axis direction acceleration detection portion, and a Z-axis direction acceleration detection portion. A wiring pattern which is a conduction path is provided, and a dummy pattern (dummy conduction path) 24 is provided. The dummy pattern 24 is provided in order to improve the symmetry with respect to the central axis in the Y direction of the wiring pattern in the beam portion regions on both sides of the connecting portion side band-like beam portion portion 15 (15a, 15b). Thereby, the bending deformation of the beam part 4 at the time of acceleration generation which will be described later becomes a more preferable state for acceleration detection, and the accuracy of acceleration detection can be improved.

  In the example of FIG. 7A, the wiring patterns Ls which are conductive paths are wired side by side at intervals in the beam region on both sides of the connecting portion side belt-like beam portion 15 (15a, 15b). Yes. Between the wiring patterns Ls wired side by side, a slit 17 for improving sensitivity is disposed. Thereby, the insulation between the wiring patterns wired side by side can be improved.

  The acceleration sensor 1 of this embodiment is configured as described above, and can detect acceleration as described below. For example, when acceleration in the X-axis direction occurs, a force in the X-axis direction resulting from the acceleration acts on the weight portion 7 (7a, 7b). Due to the acting force in the X-axis direction on the weight part 7, the weight part 7 (7a, 7b) is, for example, from the reference state shown by the dotted line in the model diagram of FIG. As shown in the schematic cross-sectional view of FIG. 8B, the deflection is displaced in the X-axis direction. Due to the displacement of the weight portion 7 in the X-axis direction, the beam portion 4 is bent and deformed via the connecting portion 8, and as a result, the following stress is generated in the beam portion 4.

For example, when the weight portion 7 is displaced as shown by the solid line in FIG. 8A or FIG. 8B due to the generation of acceleration in the X-axis direction, the model diagram of FIG. as shown in, tensile stress is on the left side a _L of the connecting portion side strip beam portion site 15a is also compressive stress on the right side a _R of the connecting portion side strip beam portion site 15a is further connected side strip tensile stress on the left B _L of the beam portion site 15b is, furthermore, compressive stress on the right B _R of the connecting portion side strip beam portion sites 15b, respectively, occurs. Further, both sides C _U of the support part side band beam portions site 16a, the C _D, respectively, compressive stress is generated on both sides D _U, D _D of the supporting portion side band beam portion sites 16b, respectively, tensile stress Will occur.

In this way, each portion A _L , A _R , B _L , B _R , C _U , C _D , D _U , D _{D of} the beam portion 4 where stress is generated due to the acceleration of the weight portion 7 in the X-axis direction. Are provided with piezoresistive portions R _X2 , R _X1 , R _X3 , R _X4 , R _Z2 , R _Z3 , R _Z1 and R _Z4 , respectively. The electric resistance values of the piezoresistive portions R _X2 , R _X1 , R _X3 , R _X4 , R _Z2 , R _Z3 , R _Z1 , and R _Z4 change due to the generation of stress due to the acceleration in the X-axis direction.

Table 1 shows the stress of the beam 4 and the piezoresistive resistance generated at the portions where the piezoresistive portions R _{X1 to} R _X4 , R _{Y1 to} R _Y4 , and R _{Z1 to} R _Z4 are disposed when acceleration in the X direction occurs. The resistance value changes of the parts R _{X1 to} R _X4 , R _{Y1 to} R _Y4 , and R _{Z1 to} R _Z4 are shown, respectively. In Table 1 and Tables 2 and 3 described later, where the stress is indicated by minus (−), it indicates that compressive stress is generated, and where the stress is indicated by plus (+), it is tensile. It shows that stress is generated. Further, the symbols + and − of the resistance value change indicate the direction of the resistance value change, respectively. In the following description, the stress of the beam portion 4 generated in the arrangement portion of each piezoresistive portion and the change in resistance value of each piezoresistive portion will be described in detail based on Tables 1 to 3.

In the bridge circuit (X-axis bridge) of FIG. 6A, acceleration in the X-axis direction is generated, and the weight portion 7 and the beam portion 4 operate as shown in FIGS. 8A and 8B. Sometimes, the piezoresistive portions R _X1 and R _X4 exhibit a change in resistance value based on, for example, compressive stress (−) (a change in resistance value in the − direction), and the piezoresistive portions R _X2 and R _X3 include, for example, tensile stress. A change in resistance value based on (+) (a change in resistance value in the + direction) is shown. Therefore, the balance state of the resistance value of the bridge circuit of FIG. 6A is lost, the output of the bridge circuit of FIG. 6A is changed, and FIG. The fluctuation range of the output of the bridge circuit of a) changes. Thereby, the magnitude of acceleration in the X-axis direction can be detected based on the output of the bridge circuit of FIG.

When acceleration in the X-axis direction is generated as shown in FIGS. 8A and 8B, the bridge circuit (Z-axis bridge) shown in FIG. 6C is configured as shown in Table 1. The piezoresistive portions R _Z2 and R _Z3 indicate a change in resistance value based on, for example, compressive stress (−), and the piezoresistive portions R _Z1 and R _Z4 indicate, for example, a change in resistance value based on tensile stress (+). Show. At this time, the piezoresistive portion R _Z2 and the piezoresistive portion R _Z3 have resistance values that change in opposite directions because the extending directions of the piezoresistive portions are orthogonal to each other (as shown in Table 1). The resistance portion R _Z2 changes in resistance value in the (−) direction, and the piezo resistance portion R _Z3 changes in resistance value in the (+) direction). Also, the piezoresistive portion R _Z1 and the piezoresistive portion R _Z4 have the same relationship, the piezoresistive portion R _Z1 changes in resistance value in the (−) direction, and the piezoresistive portion R _Z4 changes in resistance value in the (+) direction. It becomes. That is, the piezoresistive portions R _Z1 and R _Z2 are (−), and the piezoresistive portions R _Z3 and R _Z4 are (+), indicating resistance value changes in opposite directions. For this reason, the resistance value changes of the piezoresistive portions R _Z2 , R _Z3 , R _Z1 , R _Z4 are canceled each other, and there is no significant change in the output of the bridge circuit of FIG.

Further, the beam portion (the Y-axis direction extending portions 4a and 4b) provided with the piezoresistive portions R _Y1 , R _Y2 , R _Y3 , and R _Y4 constituting the bridge circuit (Y-axis bridge) of FIG. In the vicinity of the extension tip portion, the generated stress is small, and the piezoresistive portions R _{Y1 to} R _Y4 are arranged symmetrically with respect to the X axis and Y axis at the center of the beam portion 4. Therefore, as shown in Table 1, the change in resistance value of the piezoresistive portions R _Y2 and R _Y3 is (−), and the change in resistance value of the piezoresistive portions R _Y1 and R _Y4 is (+). Further, the resistance values of the piezoresistive portions R _Y2 and R _Y3 and the piezoresistive portions R _Y1 and R _Y4 change to the same extent. For this reason, the potentials of the electric resistance portions P _Y1 and P _Y2 do not change. For this reason, when the acceleration in the X-axis direction is generated, the balanced state of the resistance value of the bridge circuit of FIG. 6B is maintained, and the output of the bridge circuit of FIG. 6B hardly changes.

  When acceleration in the Y-axis direction occurs, force in the Y-axis direction resulting from the acceleration acts on the weight portion 7 (7a, 7b). In this embodiment, the height position of the gravity center position W7 of the weight portion 7 and the fulcrum position W4 of the beam portion 4 that supports the weight portion 7 are shifted. When force in the Y-axis direction acts on the portion 7 (7a, 7b), the weight portions 7a, 7b are shown in, for example, FIG. 9A from the reference state indicated by the dotted line in the model diagram of FIG. As shown in the solid line and the schematic sectional view of FIG. 9B, one side of the weights 7a and 7b (the weight 7a in the examples of FIGS. 9A and 9B) is the base 2 Displacement in the Y-axis direction while approaching. Further, the other side (the weight portion 7b in the examples of FIGS. 9A and 9B) is displaced in the Y-axis direction while being lifted with respect to the base 2. As a result, the connecting portion 8 and the beam portion 4 are bent and deformed, and the following stress is generated in the beam portion 4.

For example, when the weight portion 7 is displaced as shown in FIGS. 9A and 9B, the distance (Ly) in the Z direction between the surface of the beam 4 and the gravity center position of the weight 7 and the inertial force. Due to the moment M (M = ma · Ly) formed by the product of (ma), a uniform moment acts on the Y-axis direction extension portion 4a in the beam portion 4. Then, as shown in the model diagram of FIG. 9 (c), the upper region E _U tensile stress figures of the Y-axis direction extending portion 4a is also lower region E in the Y-axis direction extending portion 4a _A compressive stress is generated in each _D. Further, Y-axis direction extending portion 4b upper region F _U tensile stress in figure is, on the lower area F _D of the Y-axis direction extending portion 4b compressive stress, respectively, occurs.

Each piezoresistive portions R _Y1 to R _Y4, respectively, each of the portions E _U of the beam portion 4 which stress due to the acceleration in the Y-axis direction as described above occurs, the end of E _D, F _U, F _D Therefore, each of the piezoresistive portions R _{Y1 to} R _Y4 changes its electric resistance value due to the stress caused by the acceleration in the Y-axis direction.

Table A 2, when the acceleration in the Y-direction occurs, piezoresistive portion R _Y1 to R _Y4 and piezoresistive portion R _Z1 to R stress and the piezoresistive portions of the beam portion 4 caused arranged partial of _Z4 R _Y1 Changes in the resistance values of R _Y4 and R _{Z1 to} R _Z4 are shown.

In the bridge circuit of FIG. 6B, when the acceleration in the Y-axis direction occurs, as shown in Table 2, the piezoresistive portions R _Y1 and R _Y2 have resistances based on, for example, tensile stress (+). In addition, the piezoresistive portions R _Y3 and R _Y4 exhibit a change in resistance value (−) based on, for example, compressive stress (−), so that the resistance of the bridge circuit in FIG. The balance state of values collapses, the output of the bridge circuit of FIG. 6B changes, and the fluctuation range of the output of the bridge circuit of FIG. 6B changes according to the magnitude of acceleration in the Y-axis direction. Thus, the magnitude of acceleration in the Y-axis direction can be detected based on the output of the bridge circuit of FIG.

In this embodiment, the piezoresistive portions R _Z2 and R _Z3 are provided on the extension base end side of the Y-axis direction extension portion 4a, and the piezoresistance portion R is provided on the extension base end side of the Y-axis direction extension portion 4b. _Z1 and _RZ4 are respectively disposed. The electric resistance values of the piezoresistive portions R _Z2 , R _Z3 , R _Z1 , and R _Z4 also change due to the stress generated in the beam portion 4 due to the acceleration in the Y-axis direction. However, the piezoresistive portions R _Z2 and R _Z1 are, for example, resistance value changes based on tensile stress (+), and the piezoresistive portions R _Z3 , R _Z4 are, for example, resistance value changes based on compressive stress (−). In addition, since the piezoresistive portions R _Z1 and R _Z3 and the piezoresistive portions R _Z2 and R _Z4 extend in directions orthogonal to each other, the increase and decrease of the resistance value change with respect to the stress are almost opposite.

As a result, the resistance values of the piezoresistive portion R _Z2 and the piezoresistive portion R _Z4 change in the positive and negative directions from the reference resistance value in the absence of acceleration. For example, as shown in Table 2, the piezoresistive portion R _Z2 is (+) and the piezoresistive portion R _Z4 is (−). Further, the change in the resistance value of the piezoresistive portion R _Z1 and the piezoresistive portion R _Z3 changes in the positive and negative directions from the reference resistance value in the absence of acceleration. For example, as shown in Table 2, the piezoresistive portion R _Z3 is (+) and the piezoresistive portion R _Z1 is (−). For this reason, the resistance value changes of the piezoresistors R _Z2 , R _Z4 , R _Z1 , R _Z3 are canceled each other, and there is no significant change in the output of the bridge circuit of FIG.

Further, the piezoresistive portions R _{X1 to} R _X4 constituting the bridge circuit of FIG. _6A are arranged in a portion where there is almost no stress change when acceleration in the Y-axis direction is generated. For this reason, there is almost no change in the electric resistance value of each of the piezoresistive portions R _{X1 to} R _X4 , and there is no great change in the output of the bridge circuit of FIG. As described above, when the acceleration in the Y-axis direction is generated, the outputs of the bridge circuits in FIGS. 6A and 6C hardly change, and therefore based on the output of the bridge circuit in FIG. It is possible to accurately detect acceleration in the Y-axis direction.

  When acceleration in the Z-axis direction occurs, a force in the Z-axis direction resulting from the acceleration acts on the weight portion 7 (7a, 7b). Due to the acting force in the Z-axis direction on the weight part 7, the weight part 7 (7a, 7b) is shown in, for example, FIG. 10A from the reference state indicated by the dotted line in the model diagram of FIG. As shown in the solid line and the schematic cross-sectional view of FIG. 10B, the weight portion 7 (7a, 7b) is displaced in the Z-axis direction. As a result, the connecting portion 8 and the beam portion 4 are bent and deformed, and the following stress is generated in the beam portion 4.

For example, when the weight part 7 is displaced as shown in FIGS. 10A and 10B, the center of gravity and the Y direction of the beam part 4 are shown in the model diagram of FIG. 10C. Bending distance M (M = ma · Lz), which is the product of the distance (Lz) and the inertial force, is generated, so that the extension base end side (support) of the Y-axis direction extension parts 4a and 4b that are farthest from the center of gravity position. The maximum bending moment M is shown at each side of the part-side belt-like beam portions 16a and 16b. Then, the beam portion 4, the support portion-side band-shaped beam portions site 16a, respectively on both sides C _U of 16b, C _D, D _U, the D _D, respectively, a tensile stress is generated.

Table 3 shows the stress of the beam portion 4 generated in the piezoresistive portions R _{Y1 to} R _Y4 and the piezoresistive portions R _{Z1 to} R _Z4 when the acceleration in the Y direction occurs, and the piezoresistive portions R _Y1 to R _Y1 to Changes in the electric resistance values of R _Y4 and R _{Z1 to} R _Z4 are shown. As shown in Table 3, tensile stress (+) is generated in all the portions where the beam portions 4 of the piezoresistive portions R _{Z1 to} R _Z4 are disposed.

The piezoresistive portions R _Z1 , R _Z3 , have a shape extending along the X-axis direction, and the piezoresistive portions R _Z2 , R _Z4 are orthogonal to the extending direction of the piezoresistive portions R _Z1 , R _Z3 , The shape is elongated along the Y-axis direction. From this, when tensile stress (+) is generated in the beam portion 4, as shown in Table 3, the electrical resistance values of the piezoresistive portions R _Z2 and R _Z4 extended in the Y direction and the piezoresistive extended in the X direction. The electric resistance values of the parts R _Z3 and R _Z1 change in the opposite direction. For example, the piezoresistive portions R _Z2 and R _Z4 extended in the Y direction are (+), and the piezoresistive portions R _Z3 and R _Z1 extended in the X direction are (−).

  For these reasons, when acceleration in the Z-axis direction occurs, the balance state of the resistance values of the bridge circuit in FIG. 6C is disrupted, and the output of the bridge circuit in FIG. 6C changes. Since the fluctuation range of the output of the bridge circuit in FIG. 6C changes according to the magnitude of the acceleration in the Z-axis direction, the magnitude of the acceleration in the Z-axis direction is based on the output of the bridge circuit in FIG. Can be detected.

It should be noted that in the beam portion provided with the piezoresistive portions R _{X1 to} R _X4 constituting the bridge circuit of FIG. 6A, almost no stress due to the acceleration in the Z-axis direction is generated. For this reason, the balanced state of the resistance value of the bridge circuit of FIG. 6A is maintained, and there is almost no change in the output of the bridge circuit of FIG. Further, each beam portion portion (the portion closer to the extending tip side of the Y-axis direction extending portions 4a and 4b) provided with the piezoresistive portions R _{Y1 to} R _Y4 constituting the bridge circuit of FIG. In both cases, the same tensile stress (+) is generated. For this reason, the electrical resistance values of the piezoresistive portions R _{Y1 to} R _Y4 all change in the (+) direction. As a result, when acceleration in the Z-axis direction is generated, the balanced state of the resistance value of the bridge circuit of FIG. 6B is maintained, and the output of the bridge circuit of FIG. 6B hardly changes.

  As described above, the acceleration sensor 1 according to this embodiment can separately detect accelerations in the three axial directions of the X-axis direction, the Y-axis direction, and the Z-axis direction.

In this embodiment, in the beam portion 4, the piezoresistive portions R _{X1 to} R _X for detecting acceleration in the X-axis direction are provided on both sides of the connecting portion side band-like beam portion portions (connecting portion connecting portions) 15 a and 15 b. A slit 17 for improving sensitivity is provided in the vicinity of _X4 ). For this reason, the sensitivity of acceleration detection in the X-axis direction can be further increased, and the durability of the beam portion 4 can be increased. This has been confirmed by the experiment (simulation) of the present inventors. The simulation is the same as the acceleration sensor 1 of the embodiment except that the acceleration sensor 1 of the embodiment having a slit 17 for improving sensitivity (here, referred to as type B for convenience) and the slit 17 for improving sensitivity is not provided. In each of the configured acceleration sensors (herein referred to as type A for convenience), the connecting portion side band-shaped beam portion 15 (15a) when acceleration is generated in each of the X-axis direction, the Y-axis direction, and the Z-axis direction. 15b), the maximum stress value in the beam region on both sides of the beam, and the output voltage of the bridge circuit in FIGS. 6A to 6C related to the sensitivity of acceleration detection were examined. The experimental results relating to the stress are shown in Table 4, and the experimental results relating to the sensitivity are shown in Table 5, respectively. In this experiment, the acceleration in the X-axis direction, the Y-axis direction, and the Z-axis direction was 9.8 m / s ^2, and the power supply voltage Vs to the bridge circuit was 1V. The unit of numerical values in Table 4 is Pa, and the unit of numerical values in Table 5 is mV.

As shown in Table 5, when the acceleration in the Y-axis direction occurs, the voltage value output from the bridge circuit in FIG. 6B, and in FIG. 6C when the acceleration in the Z-axis direction occurs. Although there is no significant difference between the type A and the type B in the voltage value output from the bridge circuit (that is, the slit 17 for improving the sensitivity as in this embodiment is provided with the X-axis direction acceleration detection unit). In the case of the configuration provided in the vicinity of the piezoresistive portions R _{X1 to} R _X4, the effect of providing the slit 17 for improving the sensitivity is small for each acceleration detection in the Y-axis direction and the Z-axis direction), When the acceleration in the X-axis direction is generated, the voltage value output from the bridge circuit in FIG. 6A (that is, the sensitivity for detecting the acceleration in the X-axis direction) is approximately 16% for Type B than for Type A. Has also improved.

  Further, as shown in Table 4, when the acceleration in the Z-axis direction is generated, the maximum stress value of the beam part region on both sides of the connecting part side band-like beam part part 15 (15a, 15b) is reduced by 25%. . That is, the stress concentration is relaxed.

As shown in such experimental results, the sensitivity detection sensitivity can be improved by providing the sensitivity improving slit 17 and the stress concentration of the beam portion 4 can be reduced. In this embodiment, since the sensitivity improving slit 17 is provided in the vicinity of the piezoresistive portions R _{X1 to} R _X4 for detecting the acceleration in the X-axis direction, the effect of improving the sensitivity in detecting the acceleration in the X-axis direction. However, by providing the slits 17 for improving sensitivity in the vicinity of the piezoresistive portions R _{Y1 to} R _Y4 for detecting the acceleration in the Y-axis direction, the effect of improving the sensitivity for detecting the acceleration in the Y-axis direction is obtained. In addition, by providing a slit 17 for improving the sensitivity in the vicinity of the piezoresistive portions R _{Z1 to} R _Z4 for detecting the acceleration in the Z-axis direction, the effect of improving the sensitivity of the acceleration detection in the Z-axis direction can be obtained. Obtainable.

In the acceleration sensor 1 according to this embodiment, the bending moment M when the acceleration in the Y-axis direction is generated depends on the distance Ly in the Z-axis direction between the center of gravity of the weight portion 7 and the beam surface of the beam portion 4. Further, the bending moment M when the acceleration in the Z-axis direction is generated depends on the distance Lz in the Y-axis direction between the center of gravity of the weight portion 7 and the beam surface of the beam portion 4. If the height of the element of the acceleration sensor 1 is reduced, Ly becomes smaller, and thus the sensitivity of Y-axis direction acceleration detection tends to decrease. On the other hand, in this embodiment, each piezoresistive portion R _{Y1 to} R _{Y Since Y4} is formed near the extension tip side of the Y-axis direction extension parts 4a and 4b and the beam width of the formation part is narrowed, a decrease in acceleration detection sensitivity in the Y-axis direction can be suppressed.

On the other hand, even if the height of the acceleration sensor 1 is reduced, the detection of acceleration in the Z-axis direction has no effect other than the decrease in mass. Further, the acceleration in the Z-axis direction generates a large bending moment M on the extension base end side (on both sides of the support-side belt-like beam part part 16) of the Y-axis direction extension parts 4a and 4b of the beam 4. For this reason, the sensitivity fall of the Z-axis direction acceleration detection can be suppressed by disposing the piezoresistive portions R _{Z1 to} R _Z4 at the respective portions. In addition, if the weight part 7 is lengthened in the Y direction, Lz becomes long and the sensitivity in the Z-axis direction can be increased. Therefore, by increasing the weight part 7 in the Y-direction, the sensitivity in the Z-axis direction is increased in the Y-axis direction. It can be adjusted to a value equivalent to the sensitivity. Thereby, the acceleration sensor 1 of this embodiment can match the sensitivity of the acceleration detection in the Y-axis direction and the Z-axis direction even when the element is lowered, and the X-axis direction, the Y-axis direction, and the Z-axis direction. It is possible to reduce the height while maintaining the necessary sensitivity for acceleration detection in the three axial directions.

  In this embodiment, the beam portion 4 is supported by the support portion 5 (5a, 5b) in the form of a doubly supported beam, and the weight portion 7 (7a, 7b) is connected to the connecting portion 8 (8a, 5b). 8b) is supported by the beam portion 4 in a cantilever shape. For this reason, the distance between the part of the fixed part 6 to which the support part 5a is connected and the part of the fixed part 6 to which the support part 5b is connected can be formed short. Thereby, even if the base 2 and the fixed part 6 are distorted due to a change in ambient temperature, the absolute displacement due to the distortion between the fixed parts caused by the distortion of the base 2 and the fixed part 6 is small.

  Further, the beam portion 4 has a frame shape, and the frame-shaped beam portion 4 is supported by the fixing portion 6 in a doubly supported beam shape by the support portions 5 (5a, 5b). When a stress in the X-axis direction is generated due to the distortion of the beam portion, the corner region of the beam portion 4 is deformed and the stress can be released. Furthermore, when a stress in the Y-axis direction is generated due to distortion of the base 2 or the fixed portion 6, the support portion 5 (5a, 5b) can be deformed to release the stress. For this reason, in this embodiment, the bending deformation of the beam portion 4 due to the distortion of the base 2 and the fixed portion 6 can be alleviated, and the problem due to the ambient temperature variation (for example, FIG. The temperature drift problem that the output voltage value of each bridge circuit of a) to (c) fluctuates can be suppressed to a small level.

  In this embodiment, piezoresistive portions for detecting acceleration are collectively arranged on the beam portion 4 disposed in the region between the weight portions 7a and 7b. For this reason, it becomes possible to manufacture all the piezoresistive portions almost as designed, and it becomes easy to suppress variations in the output of the bridge circuit shown in FIGS. 6A to 6C. That is, Si constituting the beam portion 4 is doped with boron (B) or phosphorus (P) to produce a piezoresistive portion, and the piezoresistive portions are integrated so that each piezoresistive portion is integrated. Thus, it is possible to easily make the boron and phosphorus dope concentrations uniform. For this reason, it becomes easy to take the balance state of the resistance value of each bridge circuit, and the accuracy of acceleration detection can be improved.

  Further, in this embodiment example, all the piezoresistive portions are arranged in a concentrated manner, so that the routing route of the wiring pattern for constituting each bridge circuit of FIGS. 6A to 6C is simplified. Can do. Further, by forming a circuit by providing a cross wiring having the wiring pattern Ls and the wiring pattern Lm, the routing route of the wiring pattern can be further simplified.

  Further, in this embodiment example, the connecting portion side belt-like beam portion 15 (15a, 15b) and the support portion side belt-like beam portion 16 (16a, 16b) in the beam portion 4 are more than the other portions of the beam portion 4. The thickness in the Z-axis direction is increased. Due to the difference in thickness, the stress at the boundary portion between the connecting portion side belt-like beam portion 15 (15a, 15b) or the support portion side belt-like beam portion 16 (16a, 16b) and the other portion of the beam portion 4 is caused. The strength of is clear. In this embodiment, since the acceleration is detected by using the stress change of the beam portion 4, by clarifying the strength of the stress as described above, the X-axis direction, the Y-axis direction, and the Z-axis direction are detected. It becomes possible to detect each of the accelerations in the three axis directions more clearly separated.

  Furthermore, in this embodiment, the rigidity of the beam portion 4 can be increased by providing the reinforcing portion 20 in the frame of the beam portion 4. For example, the beam portion caused by distortion of the base 2 or the fixing portion 6. 4 can be suppressed to be small. Thereby, the erroneous detection of the acceleration resulting from the distortion of the base 2 and the fixing | fixed part 6, for example by a thermal stress can be prevented.

  Furthermore, in this embodiment, the support portions 5 (5a, 5b) are connected to the fixing portion 6 via the elastic portions 25 (25a, 25b) by the beams 26, respectively. 6 is elastically deformed according to the strain in the X-axis direction, and by this elastic deformation, the stress applied from the fixed portion 6 to the support portion 5 due to the strain of the fixed portion 6 can be reduced. As described above, in this embodiment, for example, the distortion of the beam portion 4 due to the distortion of the base 2 or the fixing portion 6 due to thermal fluctuation or the like can be suppressed to a small level. The temperature drift of the output of the configured bridge circuit can be suppressed, and thereby the reliability for acceleration detection can be improved.

  In addition, this invention is not limited to this embodiment, Various embodiments can be taken. For example, in this embodiment example, the sensitivity improving slits 17 are provided on both sides of the connecting portion side belt-like beam portion 15 (15a, 15b), which is the connecting portion connecting portion connecting portion. If the slits 17 are provided at positions symmetrical to each other with respect to the X axis and the Y axis at the center of the beam part 4, for example, considering the rigidity of the beam part 4, the wiring route of the wiring pattern, and the like. In order to improve the sensitivity of acceleration detection, it may be provided in a beam portion other than both sides of the connecting portion side beam portion 15 (15a, 15b), or the connecting portion side beam portion 15 (15a, 15b). May be provided on both sides of the beam and also on other beam portions. As described above, the position and number of the slits 17 for improving sensitivity are appropriately set.

  Further, in this embodiment example, the dummy pattern 24 is provided in the beam portion 4, but the symmetry of the wiring pattern (conduction path) in the beam portion region on both sides of the connecting portion connecting portion is the bending of the beam portion 4. The dummy pattern 24 may be omitted when the influence on the deformation is assumed to be small.

  Furthermore, in this embodiment, the support portion 5 is supported and fixed to the fixing portion 6 via the elastic portion 25. For example, as shown in the plan view of FIG. The sensor 1 may be formed.

  Furthermore, in this embodiment example, the width of the reinforcing portion 20 is equal to the width of the support portion 5 (5a, 5b) on the connection side to the beam portion 4, but the width of the reinforcing portion 20 is equal to the width of the support portion 5. It may be thicker or narrower than the width of (5a, 5b). Further, the thickness of the reinforcing portion 20 in the Z-axis direction may be the same as the thickness of the support portion 5 (5a, 5b) or may be thinner than the thickness of the support portion 5 (5a, 5b). . As described above, the width and thickness of the reinforcing portion 20 may be appropriately designed in consideration of the rigidity of the beam portion 4 itself. Moreover, as shown in FIG. 12, the reinforcement part 20 can also be abbreviate | omitted.

  Further, in this embodiment example, the beam portion 4 has the connecting portion side belt-like beam portion portion 15 (15a, 15b) and the support portion side belt-like beam portion portion 16 (16a, 16b) in the Z-axis direction more than other portions. Although the thickness is increased, the beam portion 4 may have a configuration in which the thickness in the Z-axis direction is the same or substantially equal throughout.

  Further, in this embodiment example, the frame-shaped beam portion 4 has a quadrangular shape, but may be circular, elliptical, polygonal, or rectangular. It is not limited to. The frame-shaped beam portion 4 has a symmetrical shape with respect to the central axis in the X-axis direction and a symmetrical shape with respect to the central axis in the Y-axis direction. The shape may be asymmetric with respect to the central axis in the X axis direction, or may be asymmetric with respect to the central axis in the Y axis direction.

  Furthermore, in this embodiment, the support portions 5a and 5b are formed such that the connecting side with the beam portion 4 is thicker than the fixed portion 6 side. However, the support portions 5a and 5b may have a uniform thickness. The thickness of the support portions 5a and 5b is set as appropriate. However, the thickness of the support portions 5a and 5b is preferably thinner as long as the rigidity can be maintained.

  Further, in this embodiment, one connecting portion 8 is formed to extend from both sides of the beam portion 4 in the Y-axis direction. However, as shown in FIG. A plurality of connecting portions 8 may be formed to extend while being spaced apart from each other. In addition, in FIG. 13, illustration of the slit 17 for a sensitivity improvement is abbreviate | omitted.

  Further, in this embodiment example, the piezoresistive portion for detecting acceleration is arranged as shown in FIG. 5, but the arrangement position of the piezoresistive portion is the acceleration in the X axis direction and the Y axis. As long as the acceleration in the direction and the acceleration in the Z-axis direction can be detected using the change in stress caused by the bending deformation of the beam portion 4, the position is not limited to the arrangement position in FIG. It is good. Also, the wiring example of the wiring pattern that configures the bridge circuit by connecting the piezoresistive portions may be set as appropriate, and is not limited to the example of FIG. 7, for example, wiring without cross wiring It is good also as a pattern.

Further, for example, the Z-axis direction acceleration detection unit is provided on one side of the two piezoresistive portions formed in different portions where there is no change in stress when the acceleration is generated, and on each support portion side beam portion 16a, 16b. It may be configured to have a total of four piezoresistive portions, each of which is formed with piezoresistive portions (for example, piezoresistive portions R _Z1 and R _Z3 ). The adjacent piezoresistors are electrically connected to form two voltage detectors, and the acceleration in the Z-axis direction is detected based on the difference between the voltages output from the two voltage detectors. By configuring the bridge circuit for this purpose, it is possible to form a Z-axis direction acceleration detector that can detect the acceleration in the Z-axis direction. Note that the separate portions that do not change in stress when acceleration occurs are, for example, appropriate portions of the reinforcing portion 20, the support-side-side belt-like beam portion portion 16, and the support portions 5 a and 5 b, and are arranged at this portion. The electric resistance value of the piezoresistive portion hardly changes with respect to acceleration.

Further, in this embodiment, the piezoresistive portions R _X1 and R _X2 are connected to form the voltage detecting portion P _X1 , and the piezoresistive portions R _X3 and R _X4 are connected to form the voltage detecting portion P _X2 . However, the voltage detecting unit P _X1 may be formed by connecting the piezoresistive units R _X2 and R _X4 , and the voltage detecting unit P _X2 may be formed by connecting the piezoresistive units R _X1 and R _X3. . In this embodiment, the piezoresistors R _Y2 and R _Y3 are connected to form a voltage detector P _Y1 , and the piezoresistors R _Y1 and R _Y4 are connected to form a voltage detector P _Y2 . However, the piezoresistive portions R _Y3 and R _Y1 may be connected to form the voltage detecting portion P _Y1 , and the piezoresistive portions R _Y2 and R _Y4 may be connected to form the voltage detecting portion P _Y2. . Further, in this embodiment, the piezoresistive portions R _Z2 and R _Z3 are connected to form the voltage detecting portion P _Z1 , and the piezoresistive portions R _Z1 and R _Z4 are connected to form the voltage detecting portion P _Z2 . However, the piezoresistive portions R _Z2 and R _Z1 may be connected to form the voltage detecting portion P _Z1 , and the piezoresistive portions R _Z3 and R _Z4 may be connected to form the voltage detecting portion P _Z2. .

Furthermore, in order to make the sensitivity of acceleration detection in the three-axis directions of the X axis, the Y axis, and the Z axis uniform, a resistance portion in which the electrical resistance value does not change due to the acceleration can be formed in the bridge circuit. For example, when the sensitivity of the Z-axis is larger than that of the X-axis and the Y-axis, as shown in FIG. 14, the sensitivity adjustment piezoresistors Rz, Rz, Rz ′, Rz ′ for adjusting the electrical resistance value of the bridge circuit. _May be provided in series with each of the piezoresistive portions R _Z1 , R _Z2 , R _Z3 , R _Z4 for detecting the Z-axis direction acceleration. Note that the piezoresistive portions Rz, Rz, Rz ′, and Rz ′ for sensitivity adjustment are formed in separate portions where there is no change in stress when acceleration occurs.

In this way, the resistance value change of each side of the bridge circuit is compared with the case where only one piezoresistive portion R _Z1 , R _Z2 , R _Z3 , R _Z4 is provided on each side of the bridge circuit. , Get smaller. As a result, the output fluctuation range of the bridge circuit with respect to the magnitude of acceleration in the Z-axis direction can be made equal to the output fluctuation width of the bridge circuit with respect to the magnitude of acceleration in the X-axis direction and the Y-axis direction.

  Furthermore, in this embodiment, the X-axis direction acceleration detection unit, the Y-axis direction acceleration detection unit, and the Z-axis direction acceleration detection unit that detect acceleration are each configured to include a piezoresistive unit. Alternatively, the displacement of the weight portion 7 may be detected using electrostatic capacity to detect the acceleration in the X-axis direction, the acceleration in the Y-axis direction, and the acceleration in the Z-axis direction.

  Further, in this embodiment example, the fixing portion 6 has a frame shape that surrounds the formation region of the beam portion 4 and the weight portion 7 with a gap therebetween, but the fixing portion 6 includes the support portion 5a. , 5b may be in a form that can be fixed to the base 2 in a doubly-supported beam shape, and may not be a frame shape.

  Furthermore, in this embodiment, the beam part 4, the support part 5, the fixed part 6, the weight part 7, and the connecting part 8 are configured by the SOI substrate, but they may not be configured by the SOI substrate.

It is a figure for demonstrating one embodiment of the acceleration sensor which concerns on this invention. It is sectional drawing of each of the aa part, bb part, and cc part of the acceleration sensor shown by FIG. It is sectional drawing of each of the AA part of the acceleration sensor shown by FIG. 1, BB part, and CC part. It is a figure for demonstrating the structure of the beam part which comprises the acceleration sensor shown by FIG. It is a figure for demonstrating an example of the arrangement | positioning position of the piezoresistive part provided in the beam part which comprises the acceleration sensor shown by FIG. FIG. 2 is a circuit diagram for explaining a bridge circuit constituting each acceleration detection unit in the X-axis direction, the Y-axis direction, and the Z-axis direction of the acceleration sensor of FIG. 1. FIG. 7 is a schematic diagram for explaining one wiring example of a wiring pattern for connecting a plurality of piezoresistive portions provided in a beam portion to configure the bridge circuit shown in FIG. 6. FIG. 2 is a schematic explanatory diagram for explaining an operation example of a weight portion and a beam portion when acceleration in the X-axis direction is generated in the acceleration sensor of FIG. 1. FIG. 6 is a schematic explanatory diagram for explaining an operation example of a weight portion and a beam portion when acceleration in the Y-axis direction is generated in the acceleration sensor of FIG. 1. FIG. 3 is a schematic explanatory diagram for explaining an operation example of a weight portion and a beam portion when acceleration in the Z-axis direction is generated in the acceleration sensor of FIG. 1. It is explanatory drawing for demonstrating the other embodiment example of the acceleration sensor of this invention. It is explanatory drawing for demonstrating another example of another embodiment of the acceleration sensor of this invention. Furthermore, it is explanatory drawing for demonstrating another example of another embodiment of the acceleration sensor of this invention. Furthermore, it is a circuit block diagram for demonstrating another example of another embodiment of the acceleration sensor of this invention. It is a typical perspective view showing a prior art example of an acceleration sensor. FIG. 16 is a circuit diagram for describing a bridge circuit for detecting acceleration in each of the X-axis direction, the Y-axis direction, and the Z-axis direction in the acceleration sensor shown in FIG. 15.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Acceleration sensor 2 Base 4 Beam part 4a, 4b Y-axis direction expansion | extension site | part 5,5a, 5b Support part 6 Fixing part 7,7a, 7b Weight part 8,8a, 8b Connection part 15 Connection part side belt-like beam part 16 Support side belt-like beam part 17 Slit for improving sensitivity 20 Reinforcing part 25 Elastic part 26 Stress reducing beam

Claims (7)

The base,
A frame-shaped beam portion arranged in a floating state on the surface of the base;
The beam portion is attached to the base via support portions that are formed to extend outward on both sides of the beam portion along the X-axis direction of the X-axis, the Y-axis, and the Z-axis that are orthogonal to each other from the beam portion. A beam support and fixing portion that supports the beam,
A connecting portion that is formed to extend outward along the Y-axis direction from both sides in the Y-axis direction of the beam portion in a state of floating on the surface of the base;
A weight portion connected to the extending tip of each connecting portion;
Have
The weight portion is configured to be displaceable in three axial directions of the X-axis direction, the Y-axis direction, and the Z-axis direction by deformation of the frame-shaped beam portion,
In the beam part,
An X-axis direction acceleration detection unit for detecting an acceleration in the X-axis direction based on the bending deformation of the beam part caused by the displacement of the weight part in the X-axis direction;
A Y-axis direction acceleration detection unit for detecting an acceleration in the Y-axis direction based on a bending deformation of the beam part caused by a displacement in the Y-axis direction of the weight part;
A Z-axis direction acceleration detection unit for detecting an acceleration in the Z-axis direction based on the bending deformation of the beam part caused by the Z-axis direction displacement of the weight part;
Is provided,
Further, the frame-shaped beam portion has an acceleration slit formed at a position symmetrical to each other with respect to the X-axis and the Y-axis at the center of the beam portion. Sensor.   2. The acceleration sensor according to claim 1, wherein the sensitivity improving slits are provided on both sides of the connecting portion connecting portion of the beam portion where each connecting portion is connected. The central axis of each support part that is extended in the X-axis direction from both sides of the beam part in the X-axis direction is arranged on the same straight line, and extends in the Y-axis direction from both sides of the beam part in the Y-axis direction. The central axes of the formed connecting portions are arranged on the same straight line, and the beam portion has a symmetrical shape with respect to the X-direction center line passing through the central axis of the support portion, and the center of the connecting portion. The configuration is symmetrical with respect to the Y-direction center line passing through the axis,
A plurality of sensitivity improvement slits are provided in the beam portion, and the formation position and shape of each sensitivity improvement slit are symmetric with respect to the X direction central axis in the beam portion, and the Y direction central axis. 3. The acceleration sensor according to claim 1, wherein the acceleration sensor is symmetrical with respect to the acceleration sensor.   The beam portion is provided with a plurality of conduction paths for the detection units of the X-axis direction acceleration detection unit, the Y-axis direction acceleration detection unit, and the Z-axis direction acceleration detection unit, and the connection portions are connected to each other. A dummy conducting path is provided for the wiring form of the conducting path in the beam part region on both sides of the connecting part connecting part of the beam part to be symmetric with respect to the central axis in the Y direction of the beam part. The acceleration sensor according to claim 3.   The beam part is provided with a plurality of conduction paths, and the beam part has a part where the conduction paths are wired side by side with a space between them, and the slits for improving sensitivity are wired side by side. The acceleration sensor according to any one of claims 1 to 4, wherein the acceleration sensor is provided between the conduction paths.   In the frame space of the frame-shaped beam portion, reinforcing portions that are formed to extend in the direction connecting the support portions on both sides of the beam portion are arranged, and both ends of the reinforcement portion are connected to the frame-shaped beam portions, respectively. The acceleration sensor according to any one of claims 1 to 5, wherein   The Z-axis direction acceleration detection unit, the Y-axis direction acceleration detection unit, and the X-axis direction acceleration detection unit provided in the beam part each have a piezoresistor whose electrical resistance value changes due to a stress change of the beam part due to the deformation of the beam part. The acceleration sensor according to claim 1, wherein the acceleration sensor is configured to include a portion.

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