JP2015219204A - Angular velocity sensor and sensor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an angular velocity sensor that can more optimally oscillate a piezoelectric material.SOLUTION: An angular velocity sensor 101 has a piezoelectric material 3, and the piezoelectric material 3 has: a drive unit 9; a first drive arm 11A that extends from the drive unit 9 toward one side of a y-axis direction; a first coupling arm 13A and a second coupling arm 13B that mutually extend from the drive unit 9 to a reverse side in an x-axis direction orthogonal to the y-axis direction; and a first detection arm 15A that is coupled to a tip of the first coupling arm 13A, and extends to one side of the y-axis direction. Further, the first coupling arm 13A and the second coupling arm 13B are configured such that a tip side is a side to be supported, and the drive unit 9 is capable of oscillation in the y-axis direction. Furthermore, the angular sensor 101 has an excitation circuit 103 that applies a voltage to the first drive arm 11A to excitedly oscillate the first drive arm 11A in a z-axis direction orthogonal to the y-axis direction and x-axis direction, and a detection circuit 105 that detects an electric signal to be generated by oscillation of the first detection arm 15A in the x-axis direction.

Description

  The present invention relates to an angular velocity sensor and a sensor element that can be suitably used for the angular velocity sensor.

  A so-called piezoelectric vibration type sensor is known as an angular velocity sensor. In this sensor, an alternating voltage is applied to the piezoelectric body to excite the piezoelectric body. When the excited piezoelectric body is rotated, a Coriolis force is generated in a direction orthogonal to the excitation direction with a magnitude corresponding to the rotational speed (angular velocity), and the piezoelectric body also vibrates due to the Coriolis force. The angular velocity of the piezoelectric body can be detected by detecting an electric signal generated in accordance with the deformation of the piezoelectric body due to the Coriolis force. Various proposals have been made regarding the shape of the piezoelectric body of the angular velocity sensor, the mode of vibration of the piezoelectric body, and the like.

  For example, Patent Document 1 discloses a base, a pair of detection arms extending from the base to both sides in the Y-axis direction (mechanical axis), and a pair of connecting arms extending from the base to both sides in the X-axis direction (electrical axis). A piezoelectric body having two pairs of drive arms extending on both sides in the Y-axis direction from the tips of a pair of connecting arms is disclosed. A voltage is applied to the two pairs of drive arms positioned on both sides in the X-axis direction with respect to the pair of detection arms so as to vibrate in opposite directions in the Z-axis direction (optical axis). In this state, when the piezoelectric body is rotated around the X axis, the two pairs of driving arms vibrate so as to be displaced to the opposite sides in the Y axis direction by Coriolis force. As a result, the pair of detection arms vibrate around the Z axis like a pendulum around the base. An electric signal generated by this vibration is detected, and consequently an angular velocity is detected.

JP 2011-174914 A

  The shape of the piezoelectric body of Patent Document 1 causes various inconveniences. For example, since two pairs of drive arms are provided on both sides of the detection arm, there are vibration nodes of the pair of drive arms on each side of the detection arm. Therefore, vibrations with slightly shifted frequencies are generated on both sides of the detection arm, and there is a possibility that the beat will occur. That is, there is a possibility that the start-up time becomes long. Further, for example, the piezoelectric body is supported by a base portion located at the center thereof in order to increase the displacement of the two drive arms. That is, the piezoelectric body is supported at one point. Therefore, the influence of the joining error between the base and the circuit board on which the sensor element is mounted has a great influence on the inclination of the piezoelectric body with respect to the circuit board. As a result, the angular velocity may not be accurately detected with reference to the circuit board coordinate system.

  Therefore, it is desired that at least one of such problems is solved. For example, it is desired to provide an angular velocity sensor and a sensor element capable of more suitable excitation.

  An angular velocity sensor according to an aspect of the present invention includes a drive unit, a first drive arm extending from the drive unit to one side in the extending direction, and extending from the drive unit to opposite sides in a width direction orthogonal to the extending direction. A first connecting arm, a second connecting arm, and a first detecting arm connected to a tip of the first connecting arm and extending to one side or the other side in the extending direction; The second connecting arm is a side on which a tip side is supported, and the driving unit applies a voltage to the first driving arm by applying a voltage to the piezoelectric body that can swing in the extending direction. And a detection circuit for detecting an electric signal generated by vibration of the first detection arm in the width direction.

  Preferably, the piezoelectric body is connected to a second drive arm extending from the drive unit to the opposite side of the first drive arm, and a tip of the second connection arm, and is in the same direction as the first detection arm. A second detection arm that extends, and a third detection arm that is connected to the tip of the first connection arm and extends to the opposite side of the first detection arm; and a tip of the second connection arm that is connected to the second detection arm; A fourth detection arm that extends to the opposite side of the arm, no other drive arm and no detection arm, and the excitation circuit includes the first drive arm and the second drive arm in the thickness direction. The first drive arm and the second drive arm are impressed by applying voltage to the first drive arm and the second drive arm so as to bend together to the same side, and the detection circuit adds the electrical signals generated in the first to fourth detection arms. The electrical signals generated in the first to fourth detection arms are detected by the first detection arm and the front arm. The second detection arm is bent to the opposite side in the width direction, the third detection arm and the fourth detection arm are bent to the opposite side in the width direction, and the first detection arm and the third detection arm are the When turning in the opposite direction in the width direction, the same sign is added.

  Preferably, the first connection arm is a position where the first detection arm extends from a connection position between the first connection arm and the drive unit and a position where the first detection arm is supported. And a side arm connected to the first detection arm.

  Preferably, the width of the first drive arm is larger than the thickness of the first drive arm and the width of the first detection arm.

  Preferably, the first driving arm is formed with a groove that penetrates or is recessed in the thickness direction and extends in the extending direction, and the inner wall surface of the groove and the inner wall surface of the first driving arm. An excitation electrode connected to the excitation circuit is provided on the rear surface of the substrate.

  A sensor element according to an aspect of the present invention includes a drive unit, a first drive arm extending from the drive unit to one side in the extending direction, and extending from the drive unit to opposite sides in a width direction orthogonal to the extending direction. A piezoelectric body having a first detection arm and a second connection arm, a first detection arm connected to a tip of the first connection arm, and extending to one side or the other side in the extending direction; and the first drive. A plurality of excitation electrodes arranged to be able to apply a voltage to the first drive arm to excite the arm in a thickness direction orthogonal to the extending direction and the width direction, and vibration of the first detection arm in the width direction. And a plurality of detection electrodes arranged so as to be able to detect a generated electric signal.

  According to said structure, a more suitable excitation is possible.

The perspective view which shows the structure of the sensor element which concerns on embodiment of this invention. 2A is a cross-sectional view taken along line IIa-IIa in FIG. 1, and FIG. 2B is a cross-sectional view taken along line IIb-IIb in FIG. FIGS. 3A and 3B are diagrams for explaining potentials and the like in the drive arm and the detection arm. FIGS. 4A and 4B are schematic diagrams for explaining excitation of a pair of drive arms, and FIGS. 4C and 4D are vibrations of the pair of drive arms due to Coriolis force. FIG. 4E and FIG. 4F are schematic diagrams for explaining vibrations of a pair of detection arms. The schematic diagram explaining the effect | action of the shape of the connection arm of the sensor element of FIG. The typical perspective view which shows an example of the wiring of the sensor element of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following drawings are schematic. Therefore, details may be omitted, and the dimensional ratio and the like do not always match those of the actual one.

  Further, for convenience of explanation, each figure is attached with an orthogonal coordinate system xyz. The orthogonal coordinate system xyz is defined based on the shape of the sensor element (piezoelectric body). That is, the x-axis, y-axis, and z-axis do not necessarily indicate the electrical axis, mechanical axis, and optical axis of the crystal.

  The same or similar configurations may be referred to by adding different numbers and alphabets to the same name, such as “first driving arm 11A” and “second driving arm 11B”. In some cases, it is simply referred to as “driving arm 11”, and these may not be distinguished.

  FIG. 1 is a perspective view showing a configuration of a sensor element 1 according to an embodiment of the present invention.

  The sensor element 1 constitutes an angular velocity sensor 101 that detects an angular velocity around the x axis, for example. The angular velocity sensor 101 is of a piezoelectric vibration type, and the sensor element 1 is configured to be excited in the z-axis direction and generate a Coriolis force in the y-axis direction. Specifically, it is as follows.

  The sensor element 1 includes a piezoelectric body 3, a first excitation electrode 5A and a second excitation electrode 5B (shown by hatching in FIG. 1) for applying a voltage to the piezoelectric body 3, and an electrical signal generated in the piezoelectric body 3. A first detection electrode 7A and a second detection electrode 7B (shown by hatching in FIG. 1) are provided for extraction.

The entire piezoelectric body 3 is integrally formed. The piezoelectric body 3 may be a single crystal or a polycrystal. In addition, the material of the piezoelectric body 3 may be appropriately selected, for example, quartz (SiO ₂ ), LiTaO ₃ , LiNbO ₃ , or PZT.

  In the piezoelectric body 3, the electrical axis or the polarization axis (hereinafter, only the polarization axis may be referred to representatively) is set to coincide with the x axis. The polarization axis may be inclined with respect to the x axis within a predetermined range (for example, within 15 °). Further, in the case where the piezoelectric body 3 is a single crystal, the mechanical axis and the optical axis may be appropriate directions. For example, the mechanical axis is the y-axis direction and the optical axis is the z-axis direction.

  For example, the piezoelectric body 3 is generally formed with a constant thickness (z-axis direction) as a whole. For example, the piezoelectric body 3 is generally formed in a line-symmetric shape with respect to a center line (not shown) extending in the y-axis direction and formed in a line-symmetric shape with respect to a center line (not shown) extending in the x-axis direction. Has been.

  The piezoelectric body 3 includes a drive unit 9, a first drive arm 11A and a second drive arm 11B extending from the drive unit 9 on both sides in the y-axis direction, and a first connection arm 13A extending from the drive unit 9 on both sides in the x-axis direction. And the second connecting arm 13B, the first detecting arm 15A to the fourth detecting arm 15D extending from the front end side of the pair of connecting arms 13 to both sides in the y-axis direction, and the base side of the detecting arm 15 (one pair of connecting arms The first protrusion 17A and the second protrusion 17B protrude outward in the x-axis direction from the tip end of the arm 13).

  The drive arm 11 is a portion that is excited by application of a voltage (electric field). The detection arm 15 is a part that generates an electrical signal corresponding to the angular velocity. The drive unit 9 and the connection arm 13 are parts for connecting the drive arm 11 and the detection arm 15. The protrusion 17 is a part that contributes to the support of the drive unit 9, the drive arm 11, the connecting arm 13, and the detection arm 15. The shape of each part is as follows, for example.

  For example, the drive unit 9 has a substantially rectangular parallelepiped shape. The dimensional ratio in the triaxial direction of the drive unit 9 may be set as appropriate.

  The pair of drive arms 11 are provided, for example, at positions and shapes that are line-symmetric with respect to a center line (not shown) that extends in the x-axis direction through the center of the drive unit 9. Each drive arm is, for example, generally rectangular parallelepiped long in the y-axis direction. Each drive arm 11 is formed with, for example, one or more (a plurality of) through grooves 11g that penetrate in the z-axis direction and extend in the y-axis direction. From another viewpoint, each drive arm 11 has a plurality of divided arms 11d. The drive arm 11 may have a tip whose width is increased (made a hammer shape).

  The drive arm 11 is excited to bend in the z-axis direction. On the other hand, the natural frequency of the drive arm 11 in the z-axis direction is defined by the length (y-axis direction) and the thickness (z-axis direction) of the drive arm 11. Therefore, the length and thickness of the drive arm 11 are appropriately set according to the frequency to be excited. On the other hand, the width (x-axis direction) of the drive arm 11 may be set as appropriate. In the present embodiment, the width of the drive arm 11 is larger than the thickness of the drive arm 11 and the width of the detection arm 15 (x-axis direction). For example, the width of the drive arm 11 is at least three times the thickness of the drive arm 11 and the width of the detection arm 15.

  The pair of connecting arms 13 are provided, for example, in positions and shapes that are line-symmetric with respect to a center line (not shown) that extends in the y-axis direction through the center of the drive unit 9. Each connecting arm 13 has, for example, a shape that branches into three in the y-axis direction. Specifically, for example, each connecting arm 13 includes a connecting base portion 13a protruding from the drive unit 9, a central arm 13b extending from the connecting base portion 13a, and a connecting base portion on the positive side and the negative side of the central arm 13b in the y-axis direction. And two side arms 13c extending from 13a.

  For example, the connecting base portion 13a protrudes in the x-axis direction on a center line (not shown) that extends in the x-axis direction through the center of the drive unit 9. The central arm 13b extends in the x-axis direction on the above-mentioned center line, and the tip thereof is connected to the bases of the two detection arms 15 (the connecting portion of the two detection arms 15). The side arm 13c is located, for example, on the positive side or the negative side in the y-axis direction with respect to the above-mentioned center line, and with respect to one detection arm 15, the central arm 13b and the two detection arms 15 Are connected at a position closer to the distal end side of the one detection arm 15 than the connection position. For example, the side arm 13c extends from the coupling base 13a in the y-axis direction and then extends in the x-axis direction (extends in an L shape).

  The four detection arms 15 are provided, for example, in positions and shapes that are symmetrical with respect to a center line (not shown) that extends in the x-axis direction through the center of the drive unit 9 and passes through the center of the drive unit 9 y They are provided at positions and shapes that are line-symmetric with respect to a center line (not shown) extending in the axial direction. Each detection arm 15 is, for example, generally rectangular parallelepiped long in the y-axis direction. In addition, on the positive and negative surfaces of each detection arm 15 in the z-axis direction, for example, one or more (a plurality in the present embodiment) bottomed grooves 15g extending in the y-axis direction are formed. Note that the detection arm 15 may have a tip whose width is increased (made a hammer shape).

  As will be described later, the detection arm 15 vibrates in the x-axis direction with an amplitude corresponding to the angular velocity around the x-axis of the piezoelectric body 3. The natural frequency in the x-axis direction of the detection arm 15 may be set as appropriate. However, it is preferable that it is approximately the same as the natural frequency of the drive arm 11 in the z-axis direction. Therefore, for example, the length and width of the detection arm 15 are approximately the same as the length and thickness of the drive arm 11. Although the thickness of the detection arm 15 may be set as appropriate, for example, it is the same as the thickness of the drive arm 11.

  The pair of protrusions 17 are provided, for example, at positions and shapes that are line-symmetric with respect to a center line (not shown) that extends in the y-axis direction through the center of the drive unit 9. For example, each protrusion 17 has a substantially rectangular parallelepiped shape.

  The pair of protrusions 17 is supported by a mounting base (not shown) (for example, a circuit board) on which the sensor element 1 is mounted. Thereby, the drive part 9, the drive arm 11, the connection arm 13, and the detection arm 15 are supported by the mounting substrate. In addition, the connecting arm 13 has a support side on the tip side, and the drive unit 9 and the drive arm 11 can swing in the y-axis direction.

  Specifically, for example, a pair of fixing portions 19 are fixed to the tip surfaces of the pair of protrusions 17. The fixing portion 19 may be formed integrally with the protruding portion 17 as a part of the piezoelectric body 3, or may be formed separately from the piezoelectric body 3 and bonded to the protruding portion 17. For example, a pad is formed on the positive side or the negative side of the fixing unit 19 in the z-axis direction, and the pad is fixed by bonding the pad to a pad of a mounting base (not shown) via a conductive bump. The part 19 is fixed to the mounting substrate, and the sensor element 1 is electrically connected to the mounting substrate. The pair of fixing portions 19 are preferably formed to extend to the positive side and the negative side in the y-axis direction, and are preferably fixed to the mounting base at the tip side (four corner sides of the piezoelectric body 3). In this case, it is easy to mount the piezoelectric body 3 parallel to the mounting base.

  Depending on the definition, the protrusion 17 can be regarded as a part of the connecting arm 13 and the detection arm 15 can be regarded as extending from the side surface on the distal end side of the connecting arm 13, but in this embodiment, the connecting arm 13 is connected. It is assumed that the tip of the arm 13 is connected to the side surface of the detection arm 15.

  2A is a cross-sectional view taken along line IIa-IIa in FIG. In FIG. 2A, a cross section of a part of the first drive arm 11A is shown, but the cross section of the other part of the first drive arm 11A and the cross section of the second drive arm 11B are the same.

  The excitation electrode 5 is a layered electrode formed on the surface of the drive arm 11. The excitation electrode 5 is provided on each of the plurality of divided arms 11 d of the drive arm 11. That is, the excitation electrode 5 is provided not only on the outer surface of the drive arm 11 in the x-axis direction but also on the inner wall surfaces of the plurality of through grooves 11g.

  More specifically, the first excitation electrode 5A includes, in each divided arm 11d, a positive region in the z-axis direction of the negative surface in the x-axis direction and a positive surface in the x-axis direction. Each of them is provided in the negative region in the z-axis direction. In each divided arm 11d, the second excitation electrode 5B includes a negative region in the z-axis direction of the negative surface in the x-axis direction and a z-axis direction of the positive surface in the x-axis direction. Each is provided in the positive region. The first excitation electrode 5A and the second excitation electrode 5B extend in the y-axis direction with an appropriate interval so as not to short-circuit each other.

  In each drive arm 11, the plurality of first excitation electrodes 5A are set to the same potential, for example. For example, in each drive arm 11, the plurality of first excitation electrodes 5 </ b> A are connected to each other by wiring on the piezoelectric body 3. Similarly, in each drive arm 11, the plurality of second excitation electrodes 5B are set to the same potential, for example. For example, in each driving arm 11, the plurality of second excitation electrodes 5 </ b> B are connected to each other by wiring on the piezoelectric body 3.

  The “first” and “second” and “A” and “B” of the excitation electrode 5 are attached based on the orthogonal coordinate system xyz. That is, when the first drive arm 11A is viewed from the root side to the tip side, and when the second drive arm 11B is viewed from the tip side to the root side, the first excitation electrode 5A and the second excitation electrode 5B. The first excitation electrode 5 </ b> A and the second excitation electrode 5 </ b> B are defined so that the vertical and horizontal arrangements are the same between the drive arms 11 (see FIG. 1). The relationship between the potential of the excitation electrode 5 of the first drive arm 11A and the potential of the excitation electrode 5 of the second drive arm 11B will be described later.

  FIG. 2B is a cross-sectional view taken along the line IIb-IIb in FIG. In FIG. 2B, the cross section of the second detection arm 15B is shown, but the cross sections of the other detection arms 15 are the same.

  The detection electrode 7 is a layered electrode formed on the surface of the detection arm 15. The first detection electrode 7A is provided on each of the detection arms 15 on the positive and negative surfaces in the z-axis direction. The positive and negative surfaces in the z-axis direction here include the inner wall surface and the bottom surface of the bottomed groove 15g. The second detection electrodes 7B are provided on the positive and negative surfaces of the detection arm 15 in the x-axis direction.

  The two first detection electrodes 7 </ b> A and the two second detection electrodes 7 </ b> B are provided so as to substantially cover each surface of the detection arm 15, for example. However, at least one of the first detection electrode 7A and the second detection electrode 7B (the first detection electrode 7A in the present embodiment) is formed narrower than each surface so as not to short-circuit each other.

  In each detection arm 15, the plurality of first detection electrodes 7 </ b> A are connected to each other by, for example, wiring on the piezoelectric body 3. Similarly, in each detection arm 15, the plurality of second detection electrodes 7B are connected to each other by, for example, wiring on the piezoelectric body 3 or the like.

  The “first” and “second” and “A” and “B” of the detection electrode 7 are attached based on the orthogonal coordinate system xyz, and are not attached based on the positive / negative of the electric signal. Therefore, for example, as will be described later, in the present embodiment, the first detection electrode 7A of the first detection arm 15A and the first detection electrode 7A of the second detection arm 15B generate electrical signals having the same positive and negative. It is not supposed to be connected to each other.

  The excitation electrode 5, the detection electrode 7, the wiring connected to these, and the like are made of an appropriate metal such as Cu or Al, for example.

  In addition to the sensor element 1 described above, the angular velocity sensor 101 includes an excitation circuit 103 (FIG. 2A) that applies a voltage to the excitation electrode 5 and a detection circuit 105 that detects an electrical signal from the detection electrode 7. 2 (b)).

  The excitation circuit 103 includes, for example, an oscillation circuit and an amplifier, and applies an AC voltage having a predetermined frequency between the first excitation electrode 5A and the second excitation electrode 5B. The frequency may be determined in advance in the angular velocity sensor 101 or may be specified from an external device or the like.

  The detection circuit 105 includes, for example, an amplifier and a detection circuit, detects a potential difference between the first detection electrode 7A and the second detection electrode 7B, and outputs an electric signal corresponding to the detection result to an external device or the like. Output to. More specifically, for example, the potential difference is detected as an AC voltage, and the detection circuit 105 outputs a signal corresponding to the detected amplitude of the AC voltage. Based on this amplitude, the angular velocity around the x-axis is specified. The detection circuit 105 outputs a signal corresponding to the phase difference between the voltage applied to the excitation circuit 103 and the detected electrical signal. Based on this phase difference, the direction of rotation around the x-axis is specified.

  The excitation circuit 103 and the detection circuit 105 constitute a control circuit as a whole. The control circuit is constituted by, for example, a chip IC, and is mounted on a mounting base (not shown) on which the sensor element 1 is mounted.

(Description of operation)
FIG. 3A is a diagram for explaining the potential and deformation in the drive arm 11 and is a schematic diagram corresponding to FIG.

  When a positive potential is applied to the first excitation electrode 5A and a negative potential (or reference potential) is applied to the second excitation electrode 5B, z is indicated in the vicinity of the side surface of each divided arm 11d as indicated by an arrow. An electric field is generated with the axial direction as the direction of the electric field. The direction of the electric field is opposite on both sides of each divided arm 11d in the x-axis direction. On the other hand, the polarization axis coincides with the x-axis direction. Therefore, the drive arm 11 is bent to one side in the z-axis direction. When the voltages applied to the first excitation electrode 5A and the second excitation electrode 5B are reversed, the first excitation electrode 5A and the second excitation electrode 5B bend to the other side in the z-axis direction.

  Here, a plurality of through grooves 11g are formed in the drive arm 11, and the excitation electrodes 5 are provided on both sides in the x-axis direction of the plurality of divided arms 11d. Therefore, as compared with the case where the excitation electrode 5 is provided only on the outer surface of the drive arm 11 in the x-axis direction, the area as a whole is large. As a result, the drive arm 11 can be bent by effectively forming an electric field on the drive arm 11.

  FIG. 3B is a diagram for explaining deformation and potential in the detection arm 15 and is a schematic diagram corresponding to FIG.

  When the detection arm 15 is bent to one side in the x-axis direction, an electric field having the direction of the electric field in the x-axis direction is generated as indicated by an arrow. The direction of the electric field is opposite on both sides of the detection arm 15 in the x-axis direction. The voltage due to this electric field is output to the first detection electrode 7A and the second detection electrode 7B. Further, when the detection arm 15 is bent to the opposite side in the x-axis direction, the direction of the electric field is reversed. Therefore, when the detection arm 15 vibrates in the z-axis direction, an alternating voltage is output to the first detection electrode 7A and the second detection electrode 7B.

  Here, a plurality of bottomed grooves 15g are formed in the detection arm 15, and the first detection electrode 7A is also formed on the inner wall surface of the bottomed groove 15g. Therefore, the first detection electrode 7A and the second detection electrode 7B face each other in the direction of the electric field, and an electric signal is efficiently extracted. Further, the provision of the bottomed groove 15g increases the area of the first detection electrode 7A, and an electric signal can be efficiently extracted also by this.

  FIG. 4A to FIG. 4F are schematic views for explaining the vibration of the piezoelectric body 3 as a whole.

  As shown in FIGS. 4A and 4B, the first drive arm 11A and the second drive arm 11B are excited so as to bend together on the same side in the z-axis direction.

  That is, the first excitation electrode 5A of the first drive arm 11A and the first excitation electrode 5A of the second drive arm 11B are set to the same potential by being connected to each other by the wiring provided in the piezoelectric body 3, etc. In addition, the second excitation electrode 5B of the first drive arm 11A and the second excitation electrode 5B of the second drive arm 11B are set to the same potential by being connected to each other by a wiring provided on the piezoelectric body 3, etc. An AC voltage is applied between the first excitation electrode 5A and the second excitation electrode 5B.

  When the piezoelectric body 3 is rotated around the x axis in the state where the drive arm 11 is excited in the z-axis direction as described above, as shown in FIGS. 4 (c) and 4 (d), the drive arm 11 receives Coriolis force so as to vibrate in the y-axis direction. Since the pair of drive arms 11 are excited so as to bend together on the same side in the z-axis direction, they receive Coriolis forces on the same side in the y-axis direction. Therefore, the pair of drive arms 11 and the drive unit 9 vibrate so as to be displaced in the y-axis direction.

  At this time, the pair of connecting arms 13 receives a force in the y-axis direction from the drive unit 9 and vibrates in the y-axis direction. The pair of connecting arms 13 receives a force in the y-axis direction on the drive unit 9 side, while the movement in the y-axis direction is restricted on the detection arm 15 side by the pair of protrusions 17. Therefore, a moment around the z axis is applied. The directions of the moments (clockwise or counterclockwise about the z axis) are opposite to each other between the pair of connecting arms 13.

  As shown in FIGS. 4E and 4F, the moment around the z-axis of the pair of connecting arms 13 is transmitted to the pair of detection arms 15. As a result, the pair of detection arms 15 swings around the z-axis with the base side (connection side with the connection arm 13) as the fixed axis side. As a result, the pair of detection arms 15 vibrate so as to bend in the x-axis direction.

  Specifically, the first detection arm 15A and the second detection arm 15B vibrate so as to bend toward the opposite sides in the x-axis direction. The third detection arm 15C and the fourth detection arm 15D vibrate so as to bend toward the opposite sides in the x-axis direction. The first detection arm 15A and the third detection arm 15C vibrate so as to bend toward the opposite sides in the x-axis direction.

  Therefore, for example, in order to add the electric signals generated in the four detection arms 15 with the same sign, the second detection of the first detection electrode 7A of the first detection arm 15A and the second detection of the second detection arm 15B. The electrode 7B, the second detection electrode 7B of the third detection arm 15C, and the first detection electrode 7A of the fourth detection arm 15D are connected to each other, and the second detection electrode 7B of the first detection arm 15A, the second detection electrode 15B of the second detection arm 15B. The first detection electrode 7A, the first detection electrode 7A of the third detection arm 15C, and the second detection electrode 7B of the fourth detection arm 15D are connected to each other.

  FIGS. 5A and 5B are schematic plan views for explaining the action of the side arm 13c. FIG. 5A shows a neutral state where the piezoelectric body 3 is not deformed, and FIG. 5B shows a state where the drive unit 9 is displaced to the positive side in the y-axis direction.

  In this schematic diagram, the drive part 9 and various connection parts are handled as a point for convenience. Point P1 is a connection position between the first protrusion 17A and the first detection arm 15A (base of the first detection arm 15A), and point P2 is a side arm on the positive side in the y-axis direction of the first connection arm 13A. 13c is a connection position between the first detection arm 15A.

  As shown in FIG. 5 (a), the side arm 13c on the positive side in the y-axis direction of the first connecting arm 13A is connected to the connecting position between the first connecting arm 13A and the drive unit 9, and the first detecting arm 15A. The first detection arm 15A is connected to the first detection arm 15A at a position (point P2) on the side where the first detection arm 15A extends (positive side in the y-axis direction) from the root position (point P1).

Since the point P2 is located on the side where the first detection arm 15A extends from the connection position between the first connection arm 13A and the drive unit 9, the point P2 includes the connection base portion 13a and the side arm 13c of the first connection arm 13A. As a whole, the portion is inclined toward the extending side of the first detection arm 15A with respect to the x-axis direction. Further, the length _{L 3} is longer than the distance _{L 0} between the drive unit 9 and the point P1.

Therefore, when the drive unit 9 moves to the side where the first detection arm 15A extends, as shown in FIG. 5 (b), the side arm 13c moves the first detection arm 15A outward (at the positive side in the x-axis direction) at the point P2. A force F ₁ is generated. Point P2, because than the supporting position of the first detection arm 15A (point P1) are located on the side of extension of the first detection arm 15A, the force F ₁ is a first detection arm clockwise about the point P1 A moment to rotate 15A is generated.

  Conversely, although not particularly illustrated, when the drive unit 9 moves to the negative side in the y-axis direction, the side arm 13c rotates the first detection arm 15A counterclockwise around the point P1 by the reverse action. A moment to be generated is generated.

  With the above operation, the first detection arm 15A can be effectively swung.

Further, since the distance L 1 between the point P 1 and the point P 2 is shorter than the distance L ₀ between the drive unit 9 and the point P ₁ , it is effective at the point P 2 by an action similar to the second type lever principle. The force F ₁ can be applied to That is, the point P1 is a fulcrum, the point P2 is an action point, the connection position between the first detection arm 15A and the drive unit 9 is a power point, and the force in the y-axis direction applied to the power point is F ₀ , F ₁ = (L ₀ / L ₁ ) × F ₀ .

  Although the side arm 13c on the positive side in the y-axis direction of the first connecting arm 13A has been described, the other side arm 13c has the same function.

(Example of wiring)
In the above description of the operation, the connection relationship between the plurality of excitation electrodes 5 and the plurality of detection electrodes 7 is mentioned. An example of wiring that realizes this connection relationship is shown in FIG.

  FIG. 6 is a perspective view of the sensor element 1. However, this drawing schematically shows the sensor element 1 so that the wiring is easily visible. For example, the shape of the piezoelectric body 3 is shown in a simplified manner.

  In this example, the first wiring 21 </ b> A and the second wiring 21 </ b> B whose one ends are located on the first protrusion 17 </ b> A are for applying a voltage to the plurality of excitation electrodes 5. The first wiring 21A is connected to the first excitation electrode 5A of the first drive arm 11A and the second drive arm 11B. The second wiring 21B is connected to the second excitation electrode 5B of the first drive arm 11A and the second drive arm 11B.

  In this example, the third wiring 21 </ b> C and the fourth wiring 21 </ b> D, one end of which is positioned on the second protrusion 17 </ b> B, are for taking out electrical signals from the plurality of detection electrodes 7. The third wiring 21C includes the first detection electrode 7A of the first detection arm 15A, the second detection electrode 7B of the second detection arm 15B, the second detection electrode 7B of the third detection arm 15C, and the fourth detection arm 15D. It is connected to the first detection electrode 7A. The fourth wiring 21D includes the second detection electrode 7B of the first detection arm 15A, the first detection electrode 7A of the second detection arm 15B, the first detection electrode 7A of the third detection arm 15C, and the fourth detection arm 15D. It is connected to the second detection electrode 7B.

  The wirings 21 are appropriately disposed on the four surfaces of the drive unit 9 and the four surfaces of the root side portion and the tip side portion of the various arm portions so as not to cross each other, and are appropriately branched or merged.

  Note that the wiring shown in FIG. 6 is merely an example, and the connection relationship of the electrodes mentioned in the description of the operation may be realized by other various patterns. For example, the wirings 21 may be provided so as to cross each other three-dimensionally via an insulator.

  As described above, in this embodiment, the angular velocity sensor 101 includes the piezoelectric body 3, and the piezoelectric body 3 extends from the driving unit 9 and the driving unit 9 to one side in the y-axis direction (extending direction). Connected to the arm 11A, the first connecting arm 13A and the second connecting arm 13B extending in the opposite direction in the x-axis direction (width direction) orthogonal to the y-axis direction from the drive unit 9, and the tip of the first connecting arm 13A. The first detection arm 15A extends to one side in the y-axis direction. Further, the first connecting arm 13A and the second connecting arm 13B are the sides on which the tip ends are supported, and the drive unit 9 can swing in the y-axis direction. Further, the angular velocity sensor 101 applies a voltage to the first driving arm 11A to excite the first driving arm 11A in the y-axis direction and the z-axis direction (thickness direction) orthogonal to the x-axis direction, and x And a detection circuit 105 that detects an electrical signal generated by vibration of the first detection arm 15A in the axial direction.

  From another viewpoint, in the present embodiment, the sensor element 1 includes the piezoelectric body 3, and the piezoelectric body 3 extends from the driving section 9 and the driving section 9 to one side in the y-axis direction. The first connecting arm 13A and the second connecting arm 13B extending from the drive unit 9 to the opposite sides in the x-axis direction orthogonal to the y-axis direction, and one end in the y-axis direction are connected to the tip of the first connecting arm 13A. It has the 1st detection arm 15A extended to the side. In addition, the sensor element 1 includes an excitation electrode 5 disposed so that a voltage for exciting the first drive arm 11A in the y-axis direction and the z-axis direction orthogonal to the x-axis direction can be applied to the first drive arm 11A, and the x-axis And a detection electrode 7 disposed so as to be able to detect an electric signal generated by vibration of the first detection arm 15A in the direction.

  Accordingly, the driving arm 9 and the driving arm are not driven on the base side of the pair of connecting arms 13 supported on both ends, instead of exciting the driving arms on both ends of the pair of connecting arms extending from the detection arm to both sides. 11 can be excited. As a result, for example, it is expected that the occurrence of twisting can be reduced by reducing the torsion occurring at the portion where the detection arm 15 and the connecting arm 13 are connected (the tip side of the connecting arm 13). Further, for example, since the piezoelectric body 3 can be mounted on the mounting substrate at two or more positions relatively distant from each other, it is easy to attach the piezoelectric body 3 to the mounting substrate with high accuracy.

  In the present embodiment, the piezoelectric body 3 is connected to the second drive arm 11B extending from the drive unit 9 to the opposite side of the first drive arm 11A and the tip of the second connection arm 13B, and the first detection arm 15A. The second detection arm 15B extending in the same direction as the first detection arm 15B is connected to the tip of the first connection arm 13A and connected to the third detection arm 15C extending to the opposite side of the first detection arm 15A and the second connection arm 13B. And a fourth detection arm 15D extending to the opposite side of the second detection arm 15B, and does not have other drive arms and detection arms. The excitation circuit 103 applies voltage to the first drive arm 11A and the second drive arm 11B so that the first drive arm 11A and the second drive arm 11B bend together to the same side in the z-axis direction, and excites them. The detection circuit 105 detects an electrical signal obtained by adding electrical signals generated in the first detection arm 15A to the fourth detection arm 15D. The electrical signals generated in the first detection arm 15A to the fourth detection arm 15D are such that the first detection arm 15A and the second detection arm 15B bend to the opposite sides in the x-axis direction, and the third detection arm 15C and the fourth detection arm 15D. When the first detection arm 15A and the third detection arm 15C bend opposite to each other in the x-axis direction, the same positive and negative signs are added to each other.

  Accordingly, a plurality of drive arms 11 and a plurality of detection arms 15 are arranged without leaving the base side and the tip side of the pair of connecting arms. As a result, a Coriolis force corresponding to the angular velocity is efficiently generated, and an electric signal corresponding to the angular velocity is efficiently extracted. As a result, the angular velocity sensor 101 is expected to be small and highly sensitive. Moreover, since the arrangement of the drive arm 11 and the detection arm 15 is symmetrical with respect to the drive unit 9, the piezoelectric body 3 can be vibrated with good balance.

  Further, in the present embodiment, the first connection arm 13A has a first detection than the connection position between the first connection arm 13A and the drive unit 9 and the position (P1) where the first detection arm 15A is supported. A side arm 13c connected to the first detection arm 15A is provided at a position (P2) on the side where the arm 15A extends.

  Therefore, as described with reference to FIG. 5, the y-axis direction Coriolis force received by the drive unit 9 is applied to the position (P2) away from the rotation axis (P1) of the detection arm 15 in the x-axis direction. It is expected that the detection arm 15 can be effectively vibrated in the x-axis direction, and the lever principle can be used.

  In the present embodiment, the width (x-axis direction) of the first drive arm 11A is larger than the thickness (z-axis direction) of the first drive arm 11A and the width (x-axis direction) of the first detection arm 15A.

  Therefore, the sensitivity of the angular velocity 101 can be improved by relatively increasing the mass of the first drive arm 11A. As a result, for example, the drive arm 11 can be shortened to reduce the size of the sensor element 1. As already described, in the embodiment in which the drive arm 11 is excited in the z-axis direction as in this embodiment, the natural frequency of the drive arm 11 is the length (y-axis direction) and thickness of the drive arm 11. Since the width of the drive arm 11 can be set as appropriate, such a width of the drive arm 11 can be set. That is, in the present embodiment, taking advantage of the feature that the drive arm 11 is excited in the z-axis direction, the mass of the drive arm 11 is increased to improve sensitivity.

  In the present embodiment, the first driving arm 11A is formed with a through groove 11g that penetrates in the z-axis direction and extends in the y-axis direction. The first drive arm 11A is connected to the excitation circuit 103 on the inner wall surface of the through-groove 11g and the back surface of the inner wall surface (the outer surface of the first drive arm 11A or the inner wall surface of the adjacent through-groove 11g). An excitation electrode 5 is provided.

  Therefore, as already described, the area of the excitation electrode 5 can be made relatively large with respect to the volume of the drive arm 11, and the drive arm 11 can be excited effectively. In particular, as described above, when the width of the drive arm 11 is relatively large, the excitation electrode 5 is formed in accordance with an increase in the volume of the drive arm 11 by forming a large number of through grooves 11g in the width direction. Thus, it is possible to achieve both improvement in sensitivity by increasing the area and increasing the mass and improvement in sensitivity by increasing the area of the excitation electrode 5.

  The present invention is not limited to the above embodiment, and may be implemented in various aspects.

  The number of drive arms is not limited to two. For example, one of the two drive arms in the embodiment may be omitted and the number of drive arms may be one. The number of detection arms is not limited to four. For example, any of the four detection arms in the embodiment may be omitted, and the number of detection arms may be one, two, or three. A combination of the number of drive arms and detection arms and the extending direction (positive side or negative side in the y-axis direction) may be set as appropriate. For example, only the drive arm and the detection arm that extend to one side in the y-axis direction may be provided to reduce the size of the piezoelectric body in the y-axis direction.

  A plurality of drive arms may be provided at a position where one drive arm is provided in the embodiment. For example, two drive arms extending in parallel to each other on the positive side in the y-axis direction from the drive unit and arranged in the x-axis direction may be provided. The same applies to the detection arm. For example, two detection arms that extend in parallel to each other on the positive side in the y-axis direction from the front end side of one connecting arm and are arranged in the x-axis direction may be provided. In this case, the width of each detection arm can be reduced while increasing the mass of the plurality of detection arms as a whole. Since the width of the detection arm defines the natural frequency in the x-axis direction together with the length of the detection arm, it is expected that the detection arm can be shortened while obtaining the effect of improving the sensitivity by increasing the mass.

  However, a combination of two drive arms and four detection arms is preferable from the viewpoint of sensitivity and balance. The plurality of drive arms and the plurality of detection arms are symmetrical with respect to a line extending in the y-axis direction through the center (for example, the center of gravity) of the drive unit and / or a line extending in the x-axis direction through the center of the drive unit. It is preferable that the number is even so as to be arranged.

  A groove (through groove 11g) extending in the extending direction of the driving arm may not be provided. Moreover, when a groove is provided, the groove may be a concave groove (a bottomed groove). In this case, concave grooves may be formed on both surfaces in the z-axis direction, and excitation electrodes may be provided on the inner surfaces of the respective concave grooves, or deep concave grooves may be formed on one surface in the z-axis direction, and excitation electrodes may be formed on the inner surfaces thereof. May be provided.

  A groove (bottomed groove 15g) extending in the extending direction of the detection arm may not be provided. Further, when a groove is provided, the groove may be a through groove.

  The connecting arms are not limited to those having a central arm and side arms. For example, the connecting arm may have a simple shape extending linearly with the same cross section (for example, a rectangle) in a direction orthogonal to the drive arm and the detection arm. In another aspect, the side arms may not be provided. Conversely, side arms may be provided and the central arm may be omitted. Further, in the case where the central arm and the side arm are provided, the connecting base portion that binds the central arm and the side arm may be omitted. The side arm is not limited to an L-shape. For example, the side arms may extend linearly obliquely with respect to the x-axis direction or may be curved.

  The piezoelectric body may not have the protrusion (17). For example, at the point P1 (the base of the detection arm) of the embodiment, the surface facing the z-axis direction of the piezoelectric body and the mounting substrate may be fixed to each other via bumps or spring terminals. Even in this case, in the connecting arm, the driving portion can be swingable in the extending direction with the distal end side (detection arm side) as the support side.

  DESCRIPTION OF SYMBOLS 1 ... Sensor element, 3 ... Piezoelectric body, 9 ... Drive part, 11A ... 1st drive arm, 13A ... 1st connection arm, 13B ... 2nd connection arm, 15A ... 1st detection arm, 101 ... Angular velocity sensor, 103 ... Excitation circuit, 105... Detection circuit.

Claims (6)

A drive unit, a first drive arm extending from the drive unit to one side in the extending direction, a first connecting arm and a second connecting arm extending from the driving unit to opposite sides in a width direction orthogonal to the extending direction, and , Having a first detection arm connected to the distal end of the first connection arm and extending to one side or the other side in the extending direction, and the first connection arm and the second connection arm are supported on the distal end side. A piezoelectric body that is swingable in the extending direction; and
An excitation circuit for applying a voltage to the first drive arm to excite the first drive arm in a thickness direction perpendicular to the extending direction and the width direction;
A detection circuit for detecting an electrical signal generated by vibration of the first detection arm in the width direction;
An angular velocity sensor having The piezoelectric body is
A second drive arm extending from the drive unit to the opposite side of the first drive arm;
A second detection arm connected to the tip of the second connection arm and extending in the same direction as the first detection arm;
A third detection arm connected to the tip of the first connection arm and extending to the opposite side of the first detection arm;
A fourth detection arm connected to the tip of the second connection arm and extending to the opposite side of the second detection arm, and having no other drive arm and detection arm;
The excitation circuit excites them by applying a voltage to the first drive arm and the second drive arm so that the first drive arm and the second drive arm bend together to the same side in the thickness direction,
The detection circuit detects an electrical signal obtained by adding electrical signals generated in the first to fourth detection arms, and the electrical signals generated in the first to fourth detection arms are the first detection arm and the second detection arm. The detection arm bends to the opposite side in the width direction, the third detection arm and the fourth detection arm bend to the opposite side in the width direction, and the first detection arm and the third detection arm are in the width direction. The angular velocity sensor according to claim 1, wherein positive and negative signs are added together when turning to opposite sides. The first connecting arm is located at a position where the first detection arm extends from a position where the first detection arm and the drive unit are connected and a position where the first detection arm is supported. The angular velocity sensor according to claim 1, further comprising a side arm connected to the first detection arm. The angular velocity sensor according to claim 1, wherein a width of the first drive arm is larger than a thickness of the first drive arm and a width of the first detection arm. The first drive arm is formed with a groove penetrating or recessed in the thickness direction and extending in the extending direction,
The excitation electrode connected to the said excitation circuit is provided in the inner wall surface of the said groove | channel of the said 1st drive arm, and the surface by the side of the back surface of the said inner wall surface. Angular velocity sensor. A drive unit, a first drive arm extending from the drive unit to one side in the extending direction, a first connecting arm and a second connecting arm extending from the driving unit to opposite sides in a width direction orthogonal to the extending direction, and A piezoelectric body having a first detection arm connected to the tip of the first connection arm and extending to one side or the other side in the extending direction;
A plurality of excitation electrodes arranged such that a voltage for exciting the first drive arm in the thickness direction perpendicular to the extending direction and the width direction can be applied to the first drive arm;
A plurality of detection electrodes arranged to detect an electrical signal generated by vibration of the first detection arm in the width direction;
A sensor element.

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