JP2009250956A - Inertial force sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor improved in detection accuracy by suppressing misdetections, in the detection of acceleration. <P>SOLUTION: A detection element 1 includes a first detecting element 1a, and a second detecting element 1b and a third detecting element 1c, opposed to one another across the first detecting element 1a which surround the element 1a, and the detecting elements including first to fourth counter electrodes 14a, 16a, 18a, 20a disposed thereon with shifting so as not to be partially opposed to each other in the X-axial direction and having a square X-axial sectional shape and an irregular Y-axial sectional shape. An acceleration detection part detects acceleration, based on the capacitance change between the first and the second detecting elements 1a and 1b and a capacitance change of the counter electrodes of the first and the third detecting elements 1a and 1c. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to an inertial force sensor that detects acceleration used in various electronic devices such as attitude control and navigation of a moving body such as an aircraft, an automobile, a robot, a ship, and a vehicle.

  Hereinafter, a conventional sensor will be described.

  15 is a cross-sectional view of a conventional sensor, and FIG. 16 is a cross-sectional view taken along the line AA of FIG.

  15 and 16, the conventional sensor includes a cylindrical housing 40, a columnar weight 41 disposed in the housing 40, and 4 disposed on an opposing surface of the weight 41 and the housing 40. And a pair of counter electrodes 42. A recess 43 is provided on the bottom surface of the housing 40, and the boss 44 of the weight 41 is inserted into the recess 43 to support the weight 41.

  In the above configuration, when the weight 41 is displaced by acceleration, the interval between the counter electrodes 42 is changed, and the corresponding capacitance is changed. This change in capacitance makes it possible to detect acceleration. Such a sensor for detecting acceleration is used in a posture control device or a navigation device of a moving body such as a vehicle in correspondence with 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.
JP 2002-55117 A

  In the above configuration, since the counter electrode 42 is disposed only on the facing surface of the housing 40 and the weight 41, there is a problem that the capacitance generated by the counter electrode 42 is small and the detection sensitivity is low.

  An object of the present invention is to solve the above problems and provide an inertial force sensor with increased detection sensitivity.

  In order to achieve the above-described object, the present invention particularly provides a counter electrode and first and third detection electrodes arranged on one of the first and second detection elements in the X, Y, and Z axes orthogonal to each other. As the counter electrode disposed on either one of the elements for use, an X counter electrode having a X-axis cross section in a square shape and a Y-axis cross section in a concavo-convex shape is disposed so as not to be partially opposed in the X-axis direction. The acceleration in the X-axis direction is detected by detecting a capacitance change based on a change in the facing area of the counter electrode in the X-axis direction, and the acceleration in the Z-axis direction is determined by the Z of the counter electrode. In this configuration, the acceleration is detected by detecting a change in capacitance based on a change in the facing distance in the axial direction.

  With the above configuration, the acceleration in the Z-axis direction is such that the opposing distance in the Z-axis direction of the counter electrode arranged in the first and second detection elements and the Z-axis direction of the counter electrode arranged in the first and third detection elements. The acceleration is detected by detecting a change in capacitance based on a change from the facing distance at.

  When the first, second, and third detection elements are arranged on the XY plane in the X axis, Y axis, and Z axis that are orthogonal to each other, if acceleration occurs in the Z axis direction, for example, the first and second detection elements The opposing distance in the Z-axis direction of the counter electrode arranged in the element increases and the capacitance decreases. At the same time, the opposing distance in the Z-axis direction of the opposing electrodes arranged in the first and third detection elements is reduced and the capacitance is increased. Or the reverse phenomenon occurs.

  That is, there are two capacitance changes: a capacitance change between the counter electrodes arranged in the first and second detection elements, and a capacitance change between the counter electrodes arranged in the first and third detection elements. Since acceleration is detected based on this, the sensitivity of capacitance change is increased, and the detection sensitivity can be improved.

  In particular, as the counter electrode, an X counter electrode having an X-axis cross section in a rectangular shape and a Y-axis cross section in a concavo-convex shape is provided. Therefore, when detecting acceleration based on two capacitance changes, detection accuracy is improved. It can be improved. The capacitance change between the counter electrodes arranged in the first and second detection elements and the capacitance change between the counter electrodes arranged in the first and third detection elements are in inverse proportion to each other, It varies exponentially with the distance between the counter electrodes. The capacitance change increases as the distance between the counter electrodes decreases or as the distance between the counter electrodes increases.

  As a result, for example, when two capacitance changes are differentially detected, the differentially detected output signal changes in a curve with respect to the input acceleration, which may result in error detection. The counter electrode has a rectangular X-axis cross section and a concave / convex Y-axis cross section, so that the output signal can be linear with respect to the input acceleration, and error detection is suppressed, so that highly accurate detection is possible. It becomes possible.

  The acceleration in the X-axis direction is arranged in the capacitance change based on the change in the facing area in the X-axis direction of the counter electrode arranged in the first and second detection elements, and in the first and third detection elements. The acceleration is detected by detecting a change in capacitance based on a change in the facing area of the counter electrode in the X-axis direction. As this counter electrode, in the X-axis direction, the X-electrode is arranged so as not to be partly opposed, and is provided with an X-counter electrode having a rectangular X-axis cross section and a Y-axis cross-section. Is generated in the X-axis direction, for example, the portions that are shifted so as not to face each other face each other, and the facing area increases and the capacitance increases. Or the reverse phenomenon occurs.

  That is, the acceleration is calculated based on two capacitance changes: a capacitance change between the opposing electrodes of the first and second detection elements and a capacitance change between the opposing electrodes of the first and third detection elements. Since it detects, the sensitivity of a capacitance change becomes large and a detection sensitivity can be improved.

  In particular, as the counter electrode, in the X axis direction, the X counter electrode is arranged so as not to be opposed to each other, and the X counter electrode having a rectangular X-axis cross section and a Y-axis cross section is provided. When acceleration occurs in the X-axis direction, the change in capacitance based on the change in the facing area in the X-axis direction has a proportional relationship and changes linearly.

  As a result, two capacitance changes, that is, a capacitance change between the counter electrodes arranged in the first and second detection elements and a capacitance change between the counter electrodes arranged in the first and third detection elements. When the signal is detected, the detected output signal can be made linear with respect to the input acceleration, and error detection is suppressed, and detection with very high accuracy becomes possible.

  Therefore, not only can the detection sensitivity be increased, but also acceleration in both the Z-axis direction and the X-axis direction can be detected with high accuracy.

(Embodiment 1)
1 is an exploded perspective view of a detection element of a 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 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 first detection element 1a, a second detection element 1b, and a third detection element 1c.

  The first detection element 1a 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 the two first arms 8 is supported by the support portion 12. The other end of each of the first arms 8 is connected to the frame-shaped first fixing portion 4, and two orthogonal arms are arranged inside the frame-shaped first fixing portion 4.

  The second arm 10 is bent in a U shape until it faces the second arm 10 itself, and the weight 3 is connected to the tip of the bent second arm 10. The first fixing portion 4 having a frame shape is connected to the second fixing portion 6 by a fixing arm 7, and the first fixing portion 4 is disposed inside the second fixing portion 6. 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.

  The first arm 8 is arranged in the X axis direction on the X axis, the Y axis, and the Z axis orthogonal to each other, and the first fixing portion 4 is provided with a first elastic portion 9 that is elastically deformed only in the X axis direction. The fixed arm 7 is disposed in the Y-axis direction, and the second fixed portion 6 is provided with a second elastic portion 11 that is elastically deformed only in the Y-axis direction, and is mounted on the mounting substrate by the second fixed portion 6. The first elastic portion 9 is formed by forming a slit 13 in a part of the first fixing portion 4 orthogonal to the first arm 8 in the Y-axis direction, and the second elastic portion 11 includes the second arm 10. A slit 13 is formed in a part of the second fixing portion 6 orthogonal to the X axis direction.

  The second detection element 1b is formed so as to face the surface side of the weight portion 3, and the first to fourth counter electrodes 14, 16, 18, and 20 are arranged on the respective facing surfaces. The first counter electrode to the fourth counter electrodes 14, 16, 18, and 20 arranged in the second detection element 1b are arranged so as to be shifted so as not to face each other in the X-axis direction. The first X to fourth X counter electrodes 14a, 16a, 18a, and 20a having a rectangular shape and a Y-axis cross section are provided, and are arranged so as to be partially offset from each other in the Y axis direction. The first Y counter electrode to the fourth Y counter electrodes 14b, 16b, 18b, and 20b having a rectangular Y-axis cross section and an X-axis cross section having an uneven shape are provided.

  The third detection element 1c is formed so as to be opposed to the back surface side of the weight part 3, and the fifth to eighth counter electrodes 17, 19, 21, and 23 are disposed on the respective opposing surfaces. The fifth counter electrode to the eighth counter electrode 17, 19, 21, and 23 arranged in the third detection element 1c are arranged so as to be shifted so as not to face each other in the X-axis direction, and the X-axis cross section. Are arranged in a square shape, and the fifth to eighth X counter electrodes 17a, 19a, 21a, and 23a having a Y-axis cross-sectional shape are provided. Further, in the Y-axis direction, they are arranged so as not to be opposed to each other, and the fifth to eighth Y-facing electrodes 17b, 19b, and 21b have a Y-axis cross section having a rectangular shape and an X-axis cross section having an uneven shape. , 23b. These concavo-convex shapes may be formed by arranging metal conductors having shapes as shown in FIGS. 4 (a) to 4 (d), for example. In addition, the opposing surfaces themselves of the second detection element 1b and the third detection element 1c may be formed in a concavo-convex shape along the metal conductor, or a concavo-convex electrode may be formed by combining them.

  In the first detection element 1a, the second detection element 1b, and the third detection element 1c, the two second arms 10 facing each other have a drive electrode 22 that drives and vibrates the weight 3 and the drive thereof. The first sensing electrode 26 and the second sensing electrode 28 for sensing the distortion of the second arm 10 are arranged on the other two second arms 10 facing each other. . 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. And these 1st counter electrode-4th counter electrode 14, 16, 18, 20, 5th counter electrode-8th counter electrode 17, 19, 21, 23, drive electrode 22, detection electrode 24, 1st, 2nd A signal line (not shown) is drawn from the sensing electrodes 26, 28 to the fixed arm 7, 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. 5, 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 3 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 3 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 in the counterclockwise direction of the Z axis, a direction (solid line arrow and dotted line arrow) perpendicular to the drive vibration direction with respect to the weight part 3 is synchronized with the drive vibration of the weight part 3. Since the Coriolis force is generated in the Coriolis direction (Y-axis direction) described above, distortion caused by the counterclockwise angular velocity 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 Z-axis direction will be described. As shown in FIGS. 1 and 6, the first detection element 1a, the second detection element 1b, and the third detection element 1c are 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 opposing distance (X1) of the first opposing electrode 14 disposed on the opposing surface of the first detecting element 1a and the second detecting element 1b, the first detecting element 1a and the second The opposing distance (X2) of the second opposing electrode 16 disposed on the opposing surface of the detection element 1b has a predetermined same interval. The counter distance (X1) of the fifth counter electrode 17 and the counter distance (X2) of the sixth counter electrode 19 are the same. Although not shown, the counter distance of the third counter electrode 18 and the counter distance of the fourth counter electrode 20 The facing distance is the same, and the facing distance of the seventh counter electrode 21 and the facing distance of the eighth counter electrode 23 are also the same.

  At this time, for example, when acceleration occurs in the Z-axis direction, the first arm 8 and the second arm 10 are moved in the Z-axis direction as shown in FIGS. Bend. As a result, the facing distance (X1) of the first counter electrode 14 and the facing distance (X2) of the second counter electrode 16 change. That is, between the first capacitance signal due to the capacitance change of the first counter electrode 14 of the first and second detection elements 1a and 1b and the second counter electrode 16 of the first and second detection elements 1a and 1b. The second capacitance signal due to the capacitance change changes. If the first capacitance signal increases, the second capacitance signal decreases, and acceleration can be detected based on these differential detection signals.

  FIG. 8 is a characteristic diagram showing a change in capacitance with respect to a change in the facing distance (X1) of the first counter electrode 14 and the facing distance (X2) of the second counter electrode 16, and FIG. 9 shows an output with respect to the input acceleration. FIG. 10 is an enlarged view of a part A in FIG. As shown in FIG. 9, the first capacitance signal with respect to the change in the facing distance (X1) of the first counter electrode 14 is shown as a characteristic wave A, and the second capacitance with respect to the change in the facing distance (X2) of the second counter electrode 16. The signal is shown as a characteristic wave B, and acceleration is detected based on the combined characteristic wave C. According to FIG. 9, the direction and magnitude of the acceleration are detected based on the magnitude of the output voltage with respect to the reference value.

  Here, as shown in FIG. 10, since the differential detection signal has an S-shaped curved shape in the portion A of FIG. 9, the differential detection signal is approximated to a straight line. In FIG. 10, when an acceleration A is applied as an input acceleration to a differential detection signal (solid line), a voltage A is output as an output voltage. In the acceleration detection processing circuit, this is a differential approximation that approximates a straight line. Since the acceleration B that intersects the signal (dotted line) is calculated, an error is detected.

  Therefore, in order to suppress error detection, the differential detection signal (solid line) is approximated by a straight line, and is calculated based on the differential detection signal (dotted line) approximated by a straight line. When an input acceleration A is applied to a linearly-approximate differential detection signal (dotted line), a voltage B is output as an output voltage. Therefore, no error is detected as the acceleration B is input.

  For example, the above-described configuration may be used as means for linearly approximating the differential detection signal. That is, the first X counter electrode to the fourth X counter electrodes 14a, 16a, 18a, 20a and the first Y counter electrode to the fourth Y counter electrodes 14b, 16b arranged on the opposing surfaces of the second detection element 1b and the third detection element 1c. , 18b, 20b, the fifth X counter electrode to the eighth X counter electrode 17a, 19a, 21a, 23a, and the fifth Y counter electrode to the eighth Y counter electrode 17b, 19b, 21b, 23b may be formed in an uneven shape. A metal conductor having a shape as shown in FIGS. 4A to 4D may be formed and arranged by etching using photolithography. In addition, the opposing surfaces themselves of the second detection element 1b and the third detection element 1c may be formed in a concavo-convex shape along the metal conductor, or a concavo-convex electrode may be formed by combining them. . As a result, the amount of change in capacitance with respect to the distance between the facing electrodes can be freely controlled, so that the first to fourth counter electrodes 14, 16, 18,. 20, The shape of the fifth counter electrode to the eighth counter electrode 17, 19, 21, 23 may be a shape that can obtain a desired amount of change in capacitance.

  Next, the acceleration in the X-axis direction will be described. As shown in FIGS. 1 and 11, when the first detection element 1a, the second detection element 1b, and the third detection element 1c are 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 opposing distance (X1) of the first opposing electrode 14 disposed on the opposing surface of the first detecting element 1a and the second detecting element 1b, the first detecting element 1a and the second The opposing distance (X2) of the second opposing electrode 16 disposed on the opposing surface of the detection element 1b has a predetermined same interval. The counter distance (X1) of the fifth counter electrode 17 and the counter distance (X2) of the sixth counter electrode 19 are the same. Although not shown, the counter distance of the third counter electrode 18 and the counter distance of the fourth counter electrode 20 The facing distance is the same, and the facing distance of the seventh counter electrode 21 and the facing distance of the eighth counter electrode 23 are also the same.

  At this time, for example, when acceleration occurs in the X-axis direction, as shown in FIGS. 1 and 12, the weight portion 3 tends to be displaced by (W) in the X-axis direction, and the first elastic member 9 moves in the X-axis direction. It is displaced to. As a result, the opposing areas of the first counter electrode 14, the second counter electrode 16, the fifth counter electrode 17, and the sixth counter electrode 19 change. That is, the capacitance change of the first counter electrode 14 and the second counter electrode 16 of the first and second detection elements 1a and 1b, and the fifth counter electrode 17 of the first and third detection elements 1a and 1c, The acceleration can be detected based on the capacitance change of the sixth counter electrode 19.

  In particular, in the X-axis direction, the X-axis cross section is arranged so as not to be opposed to each other, and the X-axis cross section is rectangular and the Y-axis cross section is uneven. Therefore, when acceleration occurs in the X-axis direction, The capacitance change based on the change in the facing area in the direction is a proportional relationship and changes linearly. As a result, the detected output signal is linear with respect to the input acceleration, and the error output is suppressed, so that detection with very high accuracy is possible.

  Next, the acceleration in the Y-axis direction will be described. As shown in FIGS. 1 and 13, the first detection element 1a, the second detection element 1b, and the third detection element 1c are arranged on the XY plane in the X axis, the Y axis, and the Z axis that are orthogonal to each other. If no acceleration occurs, the opposing distance (X1) of the first opposing electrode 14 disposed on the opposing surface of the first detecting element 1a and the second detecting element 1b, the first detecting element 1a and the second The opposing distance (X2) of the third opposing electrode 18 arranged on the opposing surface of the detection element 1b has a predetermined same interval. The counter distance (X1) of the fifth counter electrode 17 and the counter distance (X2) of the seventh counter electrode 21 are the same. Although not shown, the counter distance of the second counter electrode 16 and the counter distance of the fourth counter electrode 20 are not shown. The facing distance is the same, and the facing distance of the sixth counter electrode 19 and the facing distance of the eighth counter electrode 23 are also the same.

  At this time, for example, when acceleration occurs in the Y-axis direction, as shown in FIGS. 1 and 14, the weight portion 3 tends to be displaced by (W) in the X-axis direction, and the second elastic member 11 moves in the Y-axis direction. It is displaced to. As a result, the opposing areas of the first counter electrode 14, the third counter electrode 18, the fifth counter electrode 17, and the seventh counter electrode 21 change. That is, the capacitance changes of the first counter electrode 14 and the third counter electrode 18 of the first and second detection elements 1a and 1b, and the fifth counter electrode 17 of the first and third detection elements 1a and 1c, The acceleration can be detected based on the capacitance change of the seventh counter electrode 21.

  In particular, in the Y-axis direction, the Y-axis cross section is arranged so as not to be opposed to each other, and the Y-axis cross section is rectangular and the X-axis cross section is uneven. Therefore, when acceleration occurs in the Y-axis direction, the Y axis The capacitance change based on the change in the facing area in the direction is a proportional relationship and changes linearly. As a result, the detected output signal is linear with respect to the input acceleration, and the error output is suppressed, so that detection with very high accuracy is possible.

  With the above configuration, the acceleration in the Z-axis direction is arranged in the opposing distance in the Z-axis direction of the counter electrode arranged in the first and second detection elements 1a and 1b and in the first and third detection elements 1a and 1c. The acceleration can be detected by detecting the capacitance change based on the change of the counter electrode with the counter distance in the Z-axis direction. When the first, second, and third detection elements 1a, 1b, and 1c are arranged on the XY plane in the X, Y, and Z axes orthogonal to each other, if acceleration occurs in the Z axis direction, for example, the first The opposing distance in the Z-axis direction of the opposing electrodes arranged in the second detection elements 1a and 1b is increased, and the capacitance is reduced. At the same time, the opposing distance in the Z-axis direction of the opposing electrodes arranged on the first and third detection elements 1a and 1c is reduced, and the capacitance is increased. Or the reverse phenomenon occurs.

  That is, 2 of the capacitance change between the counter electrodes arranged in the first and second detection elements 1a and 1b and the capacitance change between the counter electrodes arranged in the first and third detection elements 1a and 1c. Since the acceleration is detected based on one capacitance change, the sensitivity of the capacitance change is increased and the detection sensitivity can be improved.

  First X counter electrode to fourth X counter electrode 14a, 16a, 18a, 20a, first Y counter electrode to fourth Y counter electrode 14b, 16b, 18b, 20b, fifth X counter electrode to eighth X counter electrode 17a, 19a, 21a, 23a The first Y counter electrode to the fourth Y counter electrode 17b, 19b, 21b, and 23b may be formed in an uneven shape.

  In particular, as the counter electrode, the first X counter electrode to the fourth X counter electrodes 14a, 16a, 18a, 20a and the fifth X counter electrode to the eighth X counter electrode 17a having a rectangular X-axis cross section and a Y-axis cross section having an uneven shape, Since 19a, 21a, and 23a are provided, detection accuracy can be improved when detecting acceleration based on two capacitance changes. The capacitance change between the counter electrodes arranged in the first and second detection elements 1a and 1b and the capacitance change between the counter electrodes arranged in the first and third detection elements 1a and 1c are inversely proportional to each other. The relationship varies exponentially with respect to the distance between the counter electrodes. The capacitance change increases as the distance between the counter electrodes decreases or as the distance between the counter electrodes increases.

  As a result, for example, when two capacitance changes are differentially detected, the differentially detected output signal changes in a curve with respect to the input acceleration, which may result in error detection. 1X counter electrode to 4X X counter electrode 14a, 16a, 18a, 20a and 5X X to 8X counter electrode 17a, 19a, 21a, 23a are formed by making the X-axis cross section rectangular and the Y-axis cross section uneven. Since the output signal can be linear with respect to the input acceleration, error detection is suppressed and detection with very high accuracy is possible.

  For the first Y counter electrode to the fourth Y counter electrode 14b, 16b, 18b, 20b and the fifth Y counter electrode to the eighth Y counter electrode 17b, 19b, 21b, 23b, the Y-axis cross section is rectangular and the X-axis cross section is uneven. Since the shape is adopted, the same effect can be obtained, and detection with higher accuracy becomes possible.

  Further, the acceleration in the X-axis direction includes the opposing area in the X-axis direction of the counter electrodes of the first and second detection elements 1a and 1b and the X-axis direction of the counter electrodes of the first and third detection elements 1a and 1c. The acceleration is detected by detecting a change in capacitance based on a change from the facing area at. As this counter electrode, in the X-axis direction, the first X counter electrode to the fourth X counter electrode 14a, which are arranged so as not to be partially opposed to each other and have a rectangular X-axis cross section and a Y-axis cross section as an uneven shape, 16a, 18a, 20a and the fifth X to eighth X counter electrodes 17a, 19a, 21a, 23a are provided, so when acceleration occurs in the X-axis direction, for example, a portion that is shifted so as not to oppose Are opposed to each other, the facing area is increased, and the capacitance is increased. Or the reverse phenomenon occurs.

  That is, two electrostatic capacitances, that is, a capacitance change between the opposing electrodes of the first and second detection elements 1a and 1b and a capacitance change between the opposing electrodes of the first and third detection elements 1a and 1c. Since the acceleration is detected based on the change, the sensitivity of the capacitance change is increased and the detection sensitivity can be improved.

  In particular, as the counter electrode, in the X-axis direction, the X-axis direction is arranged so as not to be opposed to each other, the X-axis cross section is rectangular, and the Y-axis cross section is uneven. 16a, 18a, 20a and the fifth to eighth X counter electrodes 17a, 19a, 21a, 23a are provided, so that when acceleration is generated in the X-axis direction, the static based on the change in the facing area in the X-axis direction is provided. The capacitance change is a proportional relationship and changes linearly.

  As a result, two capacitance changes, that is, a capacitance change between the counter electrodes arranged in the first and second detection elements and a capacitance change between the counter electrodes arranged in the first and third detection elements. Is detected, the detected output signal can be linear with respect to the input acceleration, and detection with very high accuracy is possible.

  It should be noted that the acceleration in the Y-axis direction includes the opposing area in the Y-axis direction of the counter electrodes of the first and second detection elements 1a and 1b and the Y-axis direction of the counter electrodes of the first and third detection elements 1a and 1c. The acceleration is detected by detecting a change in capacitance based on a change from the facing area at. As this counter electrode, in the Y-axis direction, the first Y counter electrode to the fourth Y counter electrode 14b, which are arranged so as to be partially offset so as not to face each other and have a rectangular Y-axis cross section and an uneven X-axis cross section, 16b, 18b, 20b and the first Y counter electrode to the fourth Y counter electrode 17b, 19b, 21b, 23b are provided, and when acceleration occurs in the Y-axis direction, for example, a portion that is shifted so as not to oppose Are opposed to each other, the facing area is increased, and the capacitance is increased. Or the reverse phenomenon occurs. That is, as with detection in the X-axis direction, detection with very high accuracy is possible in detection in the Y-axis direction.

  Therefore, in the embodiment of the present invention, not only the detection sensitivity is increased, but also three accelerations in the Z-axis direction, the X-axis direction, and the Y-axis direction can be detected with high accuracy.

  Further, in the embodiment of the present invention, the acceleration detection unit causes the first counter electrode to the fourth counter electrodes 14, 16, 18, 20 and the fifth counter electrode to the eighth counter electrodes 17, 19, 21, and 23 to be electrostatic. A change in capacitance is detected to detect acceleration, and an angular velocity detector detects a change in the state of the flexible portion that is bent due to the Coriolis force by the first and second sensing electrodes 26, 28. Thus, the acceleration and angular velocity can be detected, thereby reducing the mounting area and reducing the size. At this time, since the distal end portion of the second arm is the weight portion 3 and the counter electrode is disposed on the weight portion 3, the inertial force is increased and the detection sensitivity is improved.

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 inertial force sensor in the 1st Embodiment of this invention AA sectional view of FIG. BB sectional view of FIG. Cross section of counter electrode used in this inertial force sensor 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 Z-axis direction Characteristic diagram showing capacitance change with changes in distance between counter electrodes Characteristic diagram showing change of output voltage with respect to input acceleration Enlarged view of part A in FIG. 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 Sectional view of a conventional sensing element AA sectional view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Detection element 1a 1st detection element 1b 2nd detection element 1c 3rd detection element 3 Weight part 4 1st fixing | fixed part 6 2nd fixing | fixed part 7 Fixed arm 8 1st arm 9 1st elastic part 10 2nd arm DESCRIPTION OF SYMBOLS 11 2nd elastic part 12 Support part 13 Slit 14 1st counter electrode 14a 1X counter electrode 14b 1st Y counter electrode 16 2nd counter electrode 16a 2X counter electrode 16b 2nd Y counter electrode 17 5th counter electrode 17a 5X counter electrode 17b 5Y counter electrode 18 3rd counter electrode 18a 3X counter electrode 18b 3Y counter electrode 19 6th counter electrode 19a 6X counter electrode 19b 6Y counter electrode 20 4th counter electrode 20a 4X counter electrode 20b 4Y counter electrode 21 7th counter electrode 21a 7X counter electrode 21b 7X counter electrode 22 Drive electrode 23 8th counter electrode 23a 8X counter Electrode 23b first 8Y counter electrode 24 sensing electrode 26 first sensing electrode 28 second sensing electrode

Claims (7)

A detection element having an acceleration detection unit;
The detection element includes a first detection element and a second detection element and a third detection element facing each other across the first detection element. The first, second, and third detection elements A counter electrode is arranged on each counter surface of the detection element,
In the X axis, Y axis, and Z axis orthogonal to each other,
A part of the counter electrode arranged in one of the first and second detection elements and the counter electrode arranged in either the first or third detection element are opposed in the X-axis direction. And an X counter electrode having an X-axis cross section in a square shape and a Y-axis cross section in a concavo-convex shape.
The acceleration in the X-axis direction is detected by detecting a change in capacitance based on a change in the facing area of the counter electrode in the X-axis direction,
The acceleration in the Z-axis direction is an inertial force sensor that detects an acceleration by detecting a change in capacitance based on a change in the facing distance of the counter electrode in the Z-axis direction. A part of the counter electrode arranged in one of the first and second detection elements and the counter electrode arranged in one of the first and third detection elements are opposed in the Y-axis direction. And a Y counter electrode having a Y-axis cross section having a rectangular shape and an X-axis cross section having an uneven shape,
The inertial force sensor according to claim 1, wherein the acceleration in the Y-axis direction is detected by detecting a change in capacitance based on a change in a facing area of the counter electrode in the Y-axis direction. The acceleration in the Z-axis direction is determined by the first capacitance signal due to the capacitance change between the counter electrodes of the first and second detection elements and the electrostatic capacitance between the counter electrodes of the first and third detection elements. The counter electrode is detected based on a differential detection signal with a second capacitance signal due to a capacitance change, and the shape of the counter electrode is linearly approximated to the differential detection signal between the first capacitance signal and the second capacitance signal. The inertial force sensor according to claim 1, wherein the inertial force sensor has an uneven shape. 2. The inertial force sensor according to claim 1, wherein only the opposing electrode surface disposed on the opposing surface of the second and third detection elements has an uneven shape. The inertial force sensor according to claim 1, wherein only the opposing surfaces of the second and third detection elements are uneven. The detection element has an angular velocity detection unit,
The first detection element includes an orthogonal arm formed by connecting a first arm and a second arm in an orthogonal direction, and a support portion that supports one end of the first arm,
In the X, Y, and Z axes orthogonal to each other, the first arm is disposed in the X-axis direction, the second arm is disposed in the Y-axis direction, and the angular velocity detection unit is configured to move the second arm in the X-axis direction. The inertial force sensor according to claim 1, wherein the angular velocity is detected based on a state change of the detection element caused by the angular velocity. The inertial force sensor according to claim 6, wherein a tip portion of the second arm is a weight portion, and the counter electrode is disposed on the weight portion.

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