JP2008232704A - Inertia force sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inertia force sensor having heightened detection sensitivity. <P>SOLUTION: This sensor is equipped with a detection element 1 having an acceleration detection part and an angular velocity detection part. The detection element 1 has two orthogonal arms wherein first arms 8 are connected to second arms 10 approximately in the orthogonal direction, and has a constitution described as follows: one end of each of two first arms 8 is supported by a support part 12; the other end of each of the two first arms 8 is connected to a frame body part 4; a weight part 2 is fixed to the tip part of the second arm 10; the frame body part 4 is connected to a fixing part 7 by a fixing arm 11; each thickness of the first arms 8 and the fixing arm 11 is formed extremely more thinly than the thickness of the second arm 10 or the weight part 2; and the first arms 8 and the fixing arm 11 are arranged mutually in the orthogonal direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to sensors used in various electronic devices such as attitude control and navigation of moving bodies such as aircraft, automobiles, robots, ships, and vehicles.

  Hereinafter, an acceleration sensor which is one of conventional inertial force sensors will be described.

  FIG. 9 is a plan view of a detection element of a conventional acceleration sensor, FIG. 10 is an AA sectional view of the detection element, and FIG. 11 is a BB sectional view of the detection element.

  9 to 11, the conventional acceleration sensor includes a detection element 51 that detects acceleration, and a processing circuit (not shown) that detects an acceleration by performing an arithmetic process on an acceleration signal output from the detection element 51. ing. The detection element 51 includes a support portion 54 that supports the weight portion 52 and a fixing portion 58 that is connected to the support portion 54 via a flexible portion 56. It is mounted on the mounting board.

  The flexible portion 56 has an arm shape, and the flexible portion 56 is arranged in a cross shape with the support portion 54 as the center, and the pair of flexible portions 56 and the support portion 54 are arranged on the same straight line. I try to do it.

  A strain resistance element 58 is provided in the flexible portion 56, and a change in resistance value of the strain resistance element 58 is output as an acceleration signal based on a change in the state of the flexible portion 56 that is bent due to the movement of the weight portion 52. ing.

  Next, detection of acceleration will be described.

  When the flexible portion 56 formed of a cross-shaped arm is arranged in the X axis direction and the Y axis direction on the X axis, the Y axis, and the Z axis orthogonal to each other, for example, when acceleration occurs in the X axis direction, the weight portion 52 Of the two flexible portions 56 arranged in the X-axis direction, one of the flexible portions 56 bends in the positive direction of the Z-axis. The other flexible portion 56 bends in the negative direction of the Z-axis (the bend portion 52 is bent as the weight 52 tries to rotate in the Z-axis direction around the support portion 54). Then, the two strain resistance elements 58 provided in the two flexible portions 56 also bend in the positive and negative directions of the Z axis according to the flexure of the flexible portion 56, so that the resistance value of the strain resistance element 58 changes. This resistance value change is output as an acceleration signal to detect acceleration.

  Such an acceleration sensor is used in a posture control device, a navigation device, or the like of a moving body such as a vehicle corresponding to a detection axis to be detected.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
Japanese Patent Laid-Open No. 10-48243

  In the above configuration, since the arm-shaped flexible portion 56 is arranged in a cross shape with the support portion 54 as the center, the weight portion 52 is formed by the flexible portion 56 arranged in the axial direction in which acceleration occurs. Movement is restricted. Of the two flexible portions 56 arranged in the X-axis direction, one of the flexible portions 56 bends in the positive direction of the Z-axis, and the other flexible portion 56 has a negative direction of the Z-axis. Deflection occurs.

  At this time, in FIG. 9, when acceleration occurs in the X-axis direction, the weight portion 52 tries to move in the X-axis direction. However, the movement of the weight portion 52 is caused by the flexible portion 56 arranged in the X-axis direction. Be regulated. Due to this restriction, the weight portion 52 tends to rotate in the Z-axis direction around the support portion 54, so that the flexible portion 56 bends, but the amount of the bend is small and the resistance value change of the strain resistance element 58 is also small. However, the detection sensitivity is low.

  The present invention solves the above-described problems, and an object thereof is to provide an inertial force sensor with increased detection sensitivity.

  In order to achieve the above object, in particular, the present invention provides a detecting element having a weight portion connected via a first connecting portion, and a frame body portion in which the weight portion is disposed inward, and the weight portion facing the weight portion. And the counter electrode disposed on the opposing surface of each of the weight part and the counter substrate. In the acceleration detection unit, the counter electrode disposed on the opposing surface of the weight part and the counter substrate. Detecting a change in capacitance between and detecting an acceleration, providing a fixing part that connects the frame body part via a second connecting part, and mounting on the mounting board at the fixing part; and The first connecting part and the second connecting part are arranged in a direction orthogonal to each other, and the thickness of the first connecting part and the thickness of the second connecting part are made thinner than the thickness of the weight part.

  With the above configuration, for example, when the first connecting portion is arranged in the X-axis direction and the second connecting portion is arranged in the Y-axis direction on the X-axis, Y-axis, and Z-axis that are orthogonal to each other, acceleration occurs in the Y-axis direction. Since the weight portion tends to rotate around the X axis with the first connecting portion as the central axis, the capacitance between the weight portion and the counter electrode of the counter substrate changes. The weight portion rotates around the X axis because the thickness of the first connecting portion is thinner than the thickness of the weight portion, so that the center of gravity position of the weight portion in the Z-axis direction is shifted from the center of gravity position of the first connecting portion. This is due to the fact that the center of gravity tries to rotate around the first connecting portion and the first connecting portion twists. Since the twist of the first connecting portion easily occurs when acceleration occurs, the capacitance between the counter electrodes is likely to change, and the detection sensitivity can be improved.

  Further, when acceleration occurs in the X-axis direction, the weight portion tends to rotate around the Y-axis with the second connection portion arranged in the direction orthogonal to the first connection portion as the central axis. The capacitance between the counter electrodes changes. The weight portion rotates about the Y axis because the thickness of the second connecting portion is thinner than the thickness of the weight portion, so that the gravity center position of the weight portion in the Z-axis direction is shifted from the gravity center position of the second connecting portion. This is due to the fact that the center of gravity tries to rotate around the second connecting portion and the second connecting portion is twisted. Since the twist of the second connecting portion is easily generated when acceleration occurs, the capacitance between the counter electrodes is easily changed, and the detection sensitivity can be improved.

  In particular, when detecting the acceleration in the X-axis direction and the Y-axis direction, the acceleration in the Y-axis direction is detected by the weight portion rotating around the X-axis with the first connecting portion as the central axis. Is detected by rotating the weight portion around the Y axis with the second connecting portion as the central axis, and each can be detected independently, and a reduction in detection can be suppressed.

(Embodiment 1)
1 is an exploded perspective view of a detection element of a composite sensor according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB in FIG.

  In FIG. 1, the composite sensor according to the first embodiment of the present invention includes a detection element 1 having an acceleration detection unit and an angular velocity detection unit. The detection element 1 includes a weight part 2 via a first connection part. The frame body part 4 is connected to the frame body part 4 via the second connection part and the frame body part 4 having a frame shape that is connected and disposed inward, the counter substrate 6 that is opposed to the weight part 2, and is disposed inward. And a frame-shaped fixing portion 7 for fixing to the mounting substrate.

  Specifically, it has two orthogonal arms in which the first arm 8 is connected to the second arm 10 in a substantially orthogonal direction, and one end of each of the two first arms 8 is supported by the support portion 12. The other end of the arm 8 is connected to the frame body portion 4. The second arm 10 is bent in a U shape until it faces the second arm 10 itself, and the weight portion 2 is connected to the tip of the bent second arm 10. The first arm 8 and the support portion 12 are arranged on substantially the same straight line, and the first arm 8 and the second arm 10 are arranged symmetrically with respect to the center of the detection element 1.

  Moreover, the frame part 4 is connected with the fixed part 7 by the fixed arm 11, the 1st arm 8 corresponds to a 1st connection part, and the fixed arm 11 corresponds to a 2nd connection part. The thicknesses of the first arm 8 and the fixed arm 11 are much thinner than the thicknesses of the second arm 10 and the weight portion 2, and the first arm 8 and the fixed arm 11 are arranged orthogonal to each other. Yes.

  Further, the counter substrate 6 is disposed so as to face the weight portion 2, and the first to fourth counter electrodes 14, 16, 18, and 20 are disposed on the respective facing surfaces of the weight portion 2 and the counter substrate 6. ing. Furthermore, a drive electrode 22 that drives and vibrates the weight portion 2 and a detection electrode 24 that detects the drive of the weight portion 2 are arranged on one of the two second arms 10 that face each other, and the other two second arms 10 that face each other. The first sensing electrode 26 and the second sensing electrode 28 for sensing the distortion of the second arm 10 are arranged. Among these electrodes, at least the drive electrode 22, the detection electrode 24, the first sensing electrode 26, and the second sensing electrode 28 are composed of an upper electrode and a lower electrode with a piezoelectric layer interposed therebetween.

  Signal lines (not shown) are framed from the first to fourth counter electrodes 14, 16, 18, 20, the drive electrode 22, the detection electrode 24, and the first and second detection electrodes 26, 28. It is pulled out to the portion 4 and is electrically connected to the wiring pattern of the mounting substrate through wire bonding or the like at the end of the signal line.

  Next, the angular velocity detection unit and the acceleration detection unit will be described.

  First, the angular velocity detection unit will be described. As shown in FIG. 4, when the first arm 8 of the detection element 1 is arranged in the X-axis direction and the second arm 10 is arranged in the Y-axis direction on the X axis, the Y axis, and the Z axis orthogonal to each other, When an AC voltage having a resonance frequency is applied to the drive electrode 22, the second arm 10 is driven to vibrate starting from the second arm 10 on which the drive electrode 22 is disposed, and accordingly, the weight portion 2 is also opposed to the second arm 10. Drive vibration occurs in the drive vibration direction indicated by the solid arrow and the dotted arrow. Further, all of the four second arms 10 and the four weight portions 2 are synchronously driven and vibrated in a direction opposite to the second arm 10 (drive signal direction). The driving vibration direction in the detection element 1 is the X-axis direction.

  At this time, for example, when an angular velocity is generated around the left of the Z-axis, in synchronization with the drive vibration of the weight portion 2, a direction perpendicular to the drive vibration direction with respect to the weight portion 2 (solid arrow and dotted arrow) Since the Coriolis force is generated in the Coriolis direction (Y-axis direction) described above, distortion caused by the angular velocity around the left of the Z-axis can be generated in the second arm 10. That is, a voltage is output from the first and second sensing electrodes 26 and 28 due to a change in the state of the second arm 10 that is bent due to the Coriolis force (a strain generated in the second arm 10). Based on this, the angular velocity is detected.

  Next, the acceleration detection unit will be described.

  First, acceleration in the X-axis direction will be described. As shown in FIGS. 1 and 5, when the counter substrate 6 is arranged on the XY plane in the X axis, the Y axis, and the Z axis orthogonal to each other, if no acceleration occurs, the counter substrate 6 and the weight portion 2 The opposing distance (H1) of the first opposing electrode 14 on the opposing surface and the opposing distance (H2) of the second opposing electrode 16 on the opposing surface of the opposing substrate 6 and the weight portion 2 are equal. The facing distance of the counter electrode 18 and the facing distance of the fourth counter electrode 20 are also equal.

  At this time, for example, when acceleration occurs in the X-axis direction, as shown in FIGS. 1 and 6, the weight portion 2 rotates around the Y-axis with the second arm 10 arranged in the Y-axis direction as the central axis. try to. As a result, the opposing distance (H1) of the opposing surface of the opposing substrate 6 and the weight portion 2 between the first opposing electrodes 14 becomes small, and the opposing distance of the second opposing electrode 16 on the opposing surface of the opposing substrate 6 and the weight portion 2 ( H2) increases. The same applies to the facing distance of the third counter electrode 18 and the facing distance of the fourth counter electrode 20.

  Next, the acceleration in the Y-axis direction will be described. As shown in FIGS. 1 and 7, when the counter substrate 6 is arranged on the XY plane in the X axis, the Y axis, and the Z axis orthogonal to each other, if no acceleration is generated, the counter substrate 6 and the weight portion 2 The opposing distance (H1) of the first opposing electrode 14 on the opposing surface and the opposing distance (H2) of the third opposing electrode 18 on the opposing surface of the opposing substrate 6 and the weight portion 2 are equal, although not shown. The opposing distance of the counter electrode 16 and the opposing distance of the fourth counter electrode 20 are also equal.

  At this time, when acceleration occurs in the Y-axis direction, as shown in FIGS. 1 and 8, the weight portion 2 is centered on the first arm 8 of the first connecting portion arranged in the X-axis direction. For example, the counter distance between the third and fourth counter electrodes 18 and 20 increases, and the counter distance between the first and second counter electrodes 14 and 16 decreases.

  That is, since the capacitance between the electrodes changes, acceleration in the X-axis direction or Y-axis direction is detected based on the change in capacitance.

  With the above configuration, the acceleration detection unit detects the capacitances of the first to fourth counter electrodes 14, 16, 18, and 20 disposed on the opposing surfaces of the weight unit 2 and the counter substrate 6, and thereby accelerates the acceleration. By detecting and detecting the change in the state of the flexible part caused by the Coriolis force by the first and second sensing electrodes 26 and 28 and detecting the acceleration and the angular velocity by one detection element 1. Therefore, the mounting area can be reduced and the size can be reduced.

  In addition, in the X axis, the Y axis, and the Z axis that are orthogonal to each other, for example, when the first connecting portion is arranged in the X axis direction and the second connecting portion is arranged in the Y axis direction, when acceleration occurs in the Y axis direction, Since the weight portion 2 tends to rotate around the X axis with the first connecting portion as the central axis, the capacitance between the weight portion 2 and the counter electrode of the counter substrate 6 changes. The weight part 2 rotates around the X axis because the thickness of the first connecting part is thinner than the weight part 2, so that the center of gravity position of the weight part and the center of gravity of the first connecting part in the Z-axis direction are shifted, This is because the center of gravity of the weight portion 2 tries to rotate around the first connecting portion and the first connecting portion is twisted. Since the twist of the first connecting portion easily occurs when acceleration occurs, the capacitance between the counter electrodes is likely to change, and the detection sensitivity can be improved.

  Furthermore, when acceleration occurs in the X-axis direction, the weight portion 2 tends to rotate around the Y-axis with the second connection portion arranged in a direction orthogonal to the first connection portion as the central axis, and thus faces the weight portion 2. The capacitance between the counter electrodes of the substrate 6 changes. Similarly to the above, the weight portion 2 rotates around the Y axis because the thickness of the second connecting portion is thinner than the thickness of the weight portion 2, so that the gravity center position of the weight portion 2 in the Z-axis direction and the second connecting portion This is due to the fact that the center of gravity of the weight part 2 is displaced and the center of gravity of the weight part 2 tries to rotate around the second connection part and the second connection part is twisted. Since the twist of the second connecting portion is easily generated when acceleration occurs, the capacitance between the counter electrodes is easily changed, and the detection sensitivity can be improved.

  In particular, when detecting the acceleration in the X-axis direction and the Y-axis direction, the acceleration in the Y-axis direction is detected by the weight portion 2 rotating around the X-axis with the first connecting portion as the central axis. The acceleration is detected when the weight portion 2 rotates around the Y axis with the second connecting portion as the central axis, and each can be detected independently, so that a decrease in detection can be suppressed.

  Since the inertial force sensor according to the present invention can improve the detection sensitivity, it can be applied to various electronic devices.

The disassembled perspective view of the detection element of the composite sensor in the 1st Embodiment of this invention AA sectional view of FIG. BB sectional view of FIG. Operation state diagram of the detection element during angular velocity detection AA cross-sectional view when the counter substrate is placed Operation state diagram of the detection element when detecting acceleration in the X-axis direction BB cross section when counter substrate is placed Operation state diagram of the detection element when detecting acceleration in the Y-axis direction Plan view of conventional detector AA sectional view of FIG. BB sectional view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Detection element 2 Weight part 4 Frame body part 6 Opposite substrate 7 Fixed part 8 1st arm 10 2nd arm 11 Fixed arm 12 Support part 14 1st counter electrode 16 2nd counter electrode 18 3rd counter electrode 20 4th counter electrode 22 driving electrode 24 sensing electrode 26 first sensing electrode 28 second sensing electrode

Claims (5)

A detection element having an acceleration detection unit;
The detection element connects a weight part via a first connection part, a frame body part in which the weight part is disposed inward, a counter substrate facing the weight part, the weight part and the counter substrate Counter electrodes arranged on each counter surface of the counter substrate, and the acceleration detecting unit detects an acceleration by detecting a change in capacitance between the counter electrode disposed on each counter surface of the weight part and the counter substrate. Detected
A fixing portion that connects the frame body portion via a second connecting portion is provided and mounted on a mounting board by the fixing portion, and the first connecting portion and the second connecting portion are arranged in directions orthogonal to each other. And an inertial force sensor in which the thickness of the first connecting portion and the thickness of the second connecting portion are made thinner than the thickness of the weight portion. The inertial force sensor according to claim 1, wherein the fixing portion has a frame shape in which the frame portion is inward. The inertial force sensor according to claim 1, wherein the detection element has a symmetrical shape. An angular velocity detection unit is provided in the detection element,
The detection element includes two orthogonal arms formed by connecting the first arm to the second arm in the orthogonal direction, and a support portion supporting the two first arms, and the first arm is the first arm. The connecting portion is connected to the tip of the second arm, and the weight portion is connected to the tip portion of the second arm. In the angular velocity detecting portion, the weight portion is driven to vibrate to detect a change in the state of the detecting element due to the Coriolis force. The inertial force sensor according to claim 1, wherein the angular velocity is detected. The inertial force sensor according to claim 4, wherein the second arm is bent until it is opposed, and an angular velocity is detected by detecting a state change of the second arm.

Images