JP2010197061A - Inertia force detecting element - Google Patents

Abstract

An object of the present invention is to improve the sensitivity and accuracy of detecting inertial force.
A first arm 2 and a second arm 3 that are flexible, support the weight 7 and have a predetermined thickness, are formed in the same plane, and are symmetrical in the thickness direction. A frame body 6 that holds the weight portion 7 via the first arm 2 and the second arm 3, a first drive electrode 8, a second drive electrode 9 that drives the weight portion 7, and the weight portion. , And the first arm 2 and the second arm 3 in a direction perpendicular to the plane on which the first arm 2 and the second arm 3 are formed. The weight part 7 has a portion thinner than the thickness of the weight part 7, and the weight part 7 is symmetrical in a direction perpendicular to the plane on which the first arm 2 and the second arm 3 are formed.
[Selection] Figure 2

Description

  The present invention relates to an inertial force detection element capable of detecting angular velocities used in various electronic devices such as attitude control and navigation of moving bodies such as aircraft, automobiles, robots, ships and vehicles.

  As the inertial force detection element, an angular velocity detection element, an acceleration detection element, a detection element capable of detecting both angular velocity and acceleration, and the like are known.

  Among such technologies, a mass part having a mass sufficient to detect inertial force, a fixing part for holding and fixing the mass part, and a connection for connecting the fixing part and the mass part The connection part is flexible, and the inertial force is detected using deformation of the connection part due to the action of inertial force or the change of the position of the mass part in the inertial force detection element. What to do is known.

  As for the principle of detecting the inertia force, for example, regarding the detection of acceleration, the inertial force acts in the direction opposite to the direction of the acceleration applied by the acceleration, and the change of the position of the mass part in the inertial force detection element or the connecting part This can be done by detecting the bending of the. Regarding the detection of angular velocity, the mass part is driven and vibrated, and Coriolis force is generated in the direction perpendicular to both the rotational axis direction of the angular velocity and the driving vibration direction of the mass part. It can be performed by detecting the change in the position of the mass part and the bending of the connecting part.

  An inertial force detection element capable of detecting accelerations in a plurality of axes and angular velocities around a plurality of axes is also known (for example, Patent Document 1).

On the other hand, with respect to detection of acceleration and angular velocity, high sensitivity has been required for inertial force detection elements. In order to increase the sensitivity, there is a method of increasing the mass and making the connecting portion flexible. Specifically, the structure which makes the thickness of a connection part thinner than the thickness of a mass part is known (for example, patent document 2).
JP 2008-046058 A JP-A-8-160067

  However, in the conventional inertial force detection element, the mass part and the connecting part have the same thickness, or even if the mass part is thicker, the center of gravity of the mass part is away from the connecting part. It was a configuration such as. In the former configuration, the detection sensitivity cannot be increased, and in the latter configuration, the deformation of the connecting portion becomes complicated or the angular velocity is detected when the mass portion receives an inertial force. Therefore, there is a possibility that the behavior of the mass part when the mass part is driven and vibrated may move in a direction other than the direction in which the drive or vibration is applied, which causes a decrease in inertial force detection accuracy. It was a cause.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems and aims to improve the sensitivity and accuracy of detecting inertial force.

  In order to achieve the above object, the present invention has the following configuration.

  The invention according to claim 1 includes a mass part, a connecting part that has flexibility, supports the mass part, has a predetermined thickness, is formed in the same plane, and is symmetrical in the thickness direction, A fixing unit that holds the mass unit via a coupling unit; a driving unit that drives the mass unit; and a detection unit that detects an inertial force acting on the mass unit. It has a portion that is thinner than the thickness of the mass part in the direction perpendicular to the plane on which the connection part is formed, and the mass part is symmetric in the direction perpendicular to the plane on which the connection part is formed. Yes.

  With this structure, the center of gravity of the mass portion is positioned at the center of the connecting portion in the thickness direction, so that the inertial force, the external impact, or the driving direction of the mass portion itself is connected. Even when acting in the plane direction in which the part is formed, the mass part moves only in this plane direction, so that the detection accuracy can be improved. Moreover, since the location thinner than a mass part is provided in the connection part, it has the effect that a sensitivity improves.

  According to a second aspect of the present invention, the fixed portion is symmetrical in a direction perpendicular to the planar direction in which the connecting portion is formed, and is thicker than the connecting portion.

  With this configuration, the invention according to claim 2 is characterized in that the strength of the fixing portion is improved in the thickness direction of the connecting portion, and the mass portion, the connecting portion, and the fixing portion are all symmetrical in the thickness direction. The behavior of the part and the deformation of the connecting part are not biased in the thickness direction, so that the detection accuracy can be further improved.

  The present invention provides a mass part, a connecting part that has flexibility, supports the mass part, has a predetermined thickness, is formed in the same plane, and is symmetrical in the thickness direction, and the connecting part A fixing unit that holds the mass unit; a drive unit that drives the mass unit; and a detection unit that detects an inertial force acting on the mass unit, wherein the coupling unit is formed with the coupling unit. The portion having a thickness smaller than the thickness of the mass portion in a direction perpendicular to the flat surface, the mass portion being symmetrical in a direction perpendicular to the plane in which the connecting portion is formed. It has the effect that the sensitivity and precision which detect can be improved.

(Embodiment 1)
Hereinafter, the first and second aspects of the present invention will be described using the first embodiment.

  1 is a plan view of an inertial force detection element according to Embodiment 1 of the present invention, FIG. 2 is a front view of the detection element, FIG. 3 is an exploded perspective view of the detection element, and FIG. 4 is Embodiment 1 of the present invention. It is a perspective view of the 1st detection element piece in.

  The inertial force sensor according to Embodiment 1 of the present invention includes an inertial force detection element 1 having a function of detecting an angular velocity. As shown in FIG. 3, the inertial force detection element 1 is formed by laminating a first detection element piece 1a and a second detection element piece 1b. The inertial force detection element 1 has a symmetrical shape with respect to the thickness direction, and the first detection element piece 1a and the second detection element piece 1b are symmetrical with respect to the thickness direction.

  In this inertial force detection element 1, two first arms 2 and two second arms 3 are connected to one of the two first arms 2. The second arm 3 is connected to the first arm 2 in a substantially perpendicular direction. One end of the two first arms 2 is supported by the third arm 4, and the other end of the two first arms 2 is connected to a frame body 6 (fixed portion) having a shape with a slit 5.

  The second arm 3 extends from the first arm 2 in a right angle direction, and further extends in a right angle direction, that is, a direction parallel to the first arm 2, and thereafter, is connected to the right arm direction, that is, the first arm 2. The bent portion 7 is bent in a U shape so as to extend in a direction parallel to the extending direction of the second arm 3, and the weight portion 7 (mass portion) is connected to the tip of the bent second arm 3. ing. The thickness of the 1st arm 2 shall be thinner than the weight part 7, and it becomes easier to bend.

  The first arm 2 and the third arm 4 are arranged on substantially the same straight line, and the first arm 2 and the second arm 3 are arranged symmetrically with respect to the center of the inertial force detection element 1. The first arm 2 and the second arm 3 constitute a connecting portion.

  When the first arm 2 is arranged in the X-axis direction and the second arm 3 is arranged in the Y-axis direction on the X-axis, Y-axis, and Z-axis orthogonal to each other, the second arms facing each other on the positive side of the Y-axis 3 is arranged with a first drive electrode 8 (drive unit) for driving and vibrating the weight portion 7 on the positive side of the Y axis, and one of the second arms 3 facing each other on the negative side of the Y axis is A second drive electrode 9 (drive unit) that drives and vibrates the weight unit 7 on the negative side of the Y-axis is disposed. In addition, each of the second arms 3 is provided with a sensing electrode 10 (detection unit) that senses the distortion of the second arm 3. The first and second drive electrodes 8, 9 and the sensing electrode 10 are formed of an upper electrode and a lower electrode with a piezoelectric layer interposed. The first arm 2 and the second arm 3 are arranged in a plane parallel to the XY plane. As shown in FIG. 4, the first detection element piece 1a includes a first arm piece 2a, a second arm piece 3a, a third arm piece 4a, a slit 5, a frame piece 6a, and a weight piece 7a. ing. The first arm piece 2a, the second arm piece 3a, the third arm piece 4a, the frame piece 6a, and the weight piece 7a, together with corresponding components in the second detection element piece 1b, respectively, A two-arm 3, a third arm 4, a frame body 6 and a weight portion 7 are configured. The first detection element piece 1a and the second detection element piece 1b are attached in the direction in which the surface on which the first drive electrode 8, the second drive electrode 9, and the sensing electrode 10 are formed in FIG. It is said. In this case, the first drive electrode 8, the second drive electrode 9, and the sensing electrode 10 are formed inside the inertial force detection element 1. The first drive electrode 8, the second drive electrode 9, and the sensing electrode 10 do not need to be formed on both the first detection element piece 1a and the second detection element piece 1b, but only on one of them. In this embodiment, it is formed only on the first detection element piece 1a. Further, the first drive electrode 8, the second drive electrode 9, and the sensing electrode 10 may be formed at positions appearing on the surface instead of being formed inside the inertial force detection element 1. For example, you may form in the surface on the opposite side to the surface in which these electrodes are formed in FIG.

  Next, detection of angular velocity will be described.

  FIG. 5 is a driving vibration state diagram of the inertial force detection element 1.

  When the first arm 2 is arranged in the X-axis direction and the second arm 3 is arranged in the Y-axis direction on the X, Y, and Z axes orthogonal to each other, the first and second drive electrodes 8 and 9 resonate. An AC voltage having a frequency is applied to drive and vibrate the second arm 3 starting from the second arm 3 on which the first and second drive electrodes 8 and 9 are arranged. Are driven and vibrated in the opposite direction (the driving vibration direction indicated by the solid arrow and the dotted arrow). All of the four second arms 3 and the four weight portions 7 are synchronously driven and vibrated in the opposing direction of the second arm 3 (drive vibration direction). The drive vibration direction in the inertial force detection element 1 is the X-axis direction. It has become.

  At this time, in the present invention, for example, the AC voltage applied to the first drive electrode 8 and the AC voltage applied to the second drive electrode 9 are applied in opposite phases to each other, and the second on the positive side of the Y axis is applied. The driving vibration state of the arm 3 and the driving vibration state of the second arm 3 on the negative side of the Y-axis are made to be just opposite. That is, when the distance between the second arm 3 on the positive side of the Y-axis is narrowed, the distance between the second arm 3 on the negative side of the Y-axis is increased.

  As a result, in the inertial force detection element 1 described above, the two second arms 3 arranged on the positive side of the X axis vibrate in opposite directions, and the two second arms 3 arranged on the negative side of the X axis. Vibrate in opposite directions, and the second arm 3 arranged on the positive side of the Y axis and the second arm 3 arranged on the negative side of the Y axis also vibrate in the opposite directions.

  A specific angular velocity detection will be described.

  In the inertial force detection element 1 as described above, for example, when an angular velocity is generated in the clockwise direction about the Z axis, the inertial force detection element 1 is driven with respect to the weight part 7 as shown in FIG. Since the Coriolis force is generated in a direction orthogonal to the vibration direction (Coriolis direction indicated by a solid arrow and a dotted arrow), it is possible to generate a distortion due to the clockwise angular velocity of the Z axis in the second arm 3. . The Coriolis direction of the inertial force detection element 1 is the Y-axis direction. When the Coriolis force is generated, each sensing electrode 10 disposed on the second arm 3 senses the distortion of the second arm 3, and the polarity of the sensing electrode 10 determines the direction in which the Coriolis force is generated. For example, two sensing electrodes 10 disposed on each of the second arms 3 are provided to sense the difference between the inner and outer strains of the second arm 3 to determine the direction of Coriolis force generation. Good. Since the strain elongation rate inside the second arm 3 is different from the strain elongation rate outside, the difference in strain can be sensed. Similarly, when the counterclockwise angular velocity of the Z axis is generated, the distortion of the second arm 3 may be sensed.

  Further, when the angular velocity is generated clockwise around the Y axis, the direction (indicated by the solid line) is perpendicular to the driving vibration direction with respect to the weight portion 7 as shown in FIG. 7 in synchronization with the driving vibration of the weight portion 7. Since the Coriolis force is generated in the Coriolis direction indicated by a dotted arrow), the second arm 3 can be distorted due to the clockwise angular velocity of the Y axis. The Coriolis direction of the inertial force detection element 1 is the Z-axis direction. When the Coriolis force is generated, each sensing electrode 10 disposed on the second arm 3 senses the distortion of the second arm 3, and the polarity of the sensing electrode 10 determines the direction in which the Coriolis force is generated. For example, the generation direction of the Coriolis force may be determined by sensing the difference between the positive Z-axis distortion and the negative Z-axis distortion of the second arm 3. Since the elongation rate of strain on the positive side of the Z axis of the second arm 3 is different from that of strain on the negative side of the Z axis, a difference in strain can be sensed. Similarly, when the counterclockwise angular velocity of the Y axis is generated, the distortion of the second arm 3 may be sensed.

  With the above configuration, when the first arm 2 is arranged in the X-axis direction and the second arm 3 is arranged in the Y-axis direction with respect to the X-axis, Y-axis, and Z-axis orthogonal to each other, If drive vibration is performed in the axial direction, distortion caused by the angular velocity around the Z axis can be generated in the second arm 3, and if this distortion is sensed, the angular velocity around the Z axis can be detected. Further, distortion caused by the angular velocity around the Y axis can be generated in the second arm 3, and if this distortion is sensed, the angular velocity around the Y axis can also be detected.

  In particular, in the inertial force detection element 1, the second arm 3 is vibrated in the X-axis direction to sense the distortion of the second arm 3 due to the angular velocity. Is generated as vibration in the Y-axis direction or vibration in the Z-axis direction due to the angular velocity. Accordingly, vibration in the X-axis direction and vibration in the Y-axis direction or Z-axis direction due to the angular velocity are generated in the second arm 3, and at this time, the vibration frequency in the X-axis direction of the second arm 3 and the Y-axis direction are generated. The vibration frequency in the direction and the vibration frequency in the Z-axis direction are the resonance frequency in the X-axis direction, the resonance frequency in the Y-axis direction, and the resonance frequency in the Z-axis direction, respectively. When the distortion of the second arm 3 is sensed, it is sensed based on the vibration frequency of the second arm 3 in the X-axis direction, so the resonance frequency of the second arm 3 in the X-axis direction and the Y-axis direction or the Z-axis direction. The sensitivity can be improved if the frequency difference between the resonance frequencies is smaller.

  In addition, you may form an acceleration detection part in the inertial force detection element 1 of the inertial force sensor of this invention.

  In the inertial force detection element 1, the acceleration detection unit senses the distortion of the first arm 2 caused by the acceleration in the first arm 2 formed thinner than the second arm 3, and detects the acceleration. do it.

  With the above configuration, it is possible to retain the function as an acceleration sensor while retaining the function as an angular velocity sensor.

  Further, the acceleration detection unit may be formed as follows.

  A counter substrate facing the weight portion 7 is disposed and a counter electrode is disposed on each of the facing surfaces of the weight portion 7 and the counter substrate so that the thickness of the first arm 2 is smaller than that of the second arm 3, resulting from acceleration. The acceleration may be detected by sensing the capacitance change between the counter electrodes.

  In the inertial force detection element 1 of the present embodiment, the weight portion 7 is symmetric with respect to the plane in the XY direction on which the first arm 2 and the second arm 3 are formed, so that the center of gravity of the weight portion 7 is also the first arm. 2 and the second arm 3 exist in the plane of the XY direction in which they are formed. Therefore, when the weight portion 7 is driven and vibrated in the XY plane direction to detect the angular velocity, the weight portion 7 is not driven and the center of gravity is not moved in the Z-axis direction due to the vibration itself. Since the vibration in the XY plane direction leaking to the outside due to vibration can be reduced or eliminated, the deterioration of the inertial force detection accuracy due to the reflection of the leaking vibration to the inertial force detection element 1 is reduced. Or it can be prevented.

  Further, since the frame body 6 is symmetrical with respect to the plane in the XY direction on which the first arm 2 and the second arm 3 are formed and is thicker than the first arm 2 and the second arm 3, the strength in the Z-axis direction is different. It becomes solid without directivity and has a structure that is difficult to be deformed by driving of the weight portion 7, vibration, inertial force, or external force, and the inertial force detection accuracy can be improved.

(Embodiment 2)
8 to 10 are diagrams for explaining the second embodiment of the present invention. FIG. 8 is a plan view of the inertial force detection element in the second embodiment of the present invention. FIG. 9 is a plan view of the inertial force detection element. FIG. 10 is an exploded perspective view of the inertial force detection element.

  As shown in FIG. 10, the inertial force detection element in the second embodiment is obtained by bonding a third detection element piece 1c, a fourth detection element piece 1d, and a fifth detection element piece 1e. The third detection element piece 1c is obtained by making the thickness of the first detection element piece 1a in the first embodiment constant, and the fourth detection element piece 1d and the fifth detection element piece 1e are the same as those in the first embodiment. The first arm piece 2a, the second arm piece 3a and the weight piece 7a of the first detection element piece 1a in FIG. The inertial force detection element 1 is symmetrical in the thickness direction. Also in this case, since the weight portion 7 is symmetric with respect to the plane in the XY direction on which the first arm 2 and the second arm 3 are formed, the center of gravity of the weight portion 7 is also determined by the first arm 2 and the second arm 3. It exists in the plane of the formed XY direction. Therefore, when the weight portion 7 is driven and vibrated in the XY plane direction to detect the angular velocity, the weight portion 7 does not move in the Z-axis direction by this driving and vibration itself, and the angular velocity is detected with high accuracy. It can be carried out.

(Embodiment 3)
11 to 13 are diagrams for explaining the third embodiment of the present invention. FIG. 11 is a plan view of the inertial force detection element in the third embodiment of the present invention. FIG. 12 is a plan view of the inertial force detection element. FIG. 13 is an exploded perspective view of the inertial force detection element.

  As shown in FIG. 13, the inertial force detection element 1 in the third embodiment is obtained by attaching a sixth detection element piece 1f to the first detection element piece 1a in the first embodiment. The sixth detection element piece 1f is similar in shape to the fourth detection element piece 1d in the second embodiment, but is different in thickness. The thickness of the sixth detection element piece 1f is set so that the weight portion 7 is symmetrical with respect to the plane in the XY direction where the first arm 2 and the second arm 3 are formed. Thereby, the gravity center of the weight part 7 exists in the plane of the XY direction in which the 1st arm 2 and the 2nd arm 3 were formed. Therefore, when the weight portion 7 is driven and vibrated in the XY plane direction to detect the angular velocity, the weight portion 7 does not move in the Z-axis direction by this driving and vibration itself, and the angular velocity is detected with high accuracy. It can be carried out.

  The inertial force detection element according to the present invention has an excellent effect that the sensitivity and accuracy of detecting the inertial force can be improved.

The top view of the inertial force detection element in Embodiment 1 of this invention Front view of the detector Exploded perspective view of the detection element The perspective view of the 1st detection element piece in Embodiment 1 of this invention Driving vibration state diagram of the inertial force detection element Strain vibration state diagram of the inertial force detection element due to angular velocity around the Z axis Strain vibration state diagram of the inertial force detection element due to angular velocity around the Y axis The top view of the inertial force detection element in Embodiment 2 of this invention Plan sectional view of the inertial force detection element Exploded perspective view of the inertial force detection element Plan view of inertial force detection element according to Embodiment 3 of the present invention Plan sectional view of the inertial force detection element Exploded perspective view of the inertial force detection element

DESCRIPTION OF SYMBOLS 1 Inertial force detection element 1a 1st detection element piece 1b 2nd detection element piece 1c 3rd detection element piece 1d 4th detection element piece 1e 5th detection element piece 1f 6th detection element piece 2 1st Arm (connection part)
2a 1st arm piece 3 2nd arm (connection part)
3a 2nd arm piece 4 3rd arm 4a 3rd arm piece 5 Slit 6 Frame (fixed part)
6a Frame piece 7 Weight part (mass part)
7a Weight piece 8 First drive electrode 9 Second drive electrode 10 Sensing electrode

Claims (2)

Part by mass;
A connecting portion that has flexibility, supports the mass portion, has a predetermined thickness, is formed in the same plane, and is symmetric in the thickness direction;
A fixing part for holding the mass part via the connecting part;
A drive unit for driving the mass unit;
A detection unit for detecting an inertial force acting on the mass unit,
The connecting part has a portion thinner than the thickness of the mass part in a direction perpendicular to the plane on which the connecting part is formed;
An inertial force detection element in which the mass portion is symmetric in a direction perpendicular to a plane in which the coupling portion is formed. The inertial force detection element according to claim 1, wherein the fixed portion is symmetric in a direction perpendicular to a planar direction in which the connecting portion is formed and is thicker than the connecting portion.

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