JPH10160481A - Angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the detection accuracy of an angular velocity sensor by forming a through hole at the center of a vibrating body, positioning a spherically shaped weight with the through hole and fixing it to the vibrating body. SOLUTION: The sensor part is constituted of a vibrating body 21, a piezoelectric element 22 and a weight 27. The piezoelectric element 22 is attached to the upper face of the vibrating body 21. An electrode 23, and a detection electrode and a feedback electrode are set on the lower face, and the upper face of the piezoelectric element 22. The spherical weight 27 is positioned and fixed on a circumference of a through hole 21a on the lower face of the vibrating body 21. The through hole 21a is formed in such size that the weight 27 does not come into touch with the piezoelectric element 22 when fixed to the vibrating body 21. The through hole 21a is preferably circular. A cylindrical supporting member 26 is fixed to the node part of bending vibration of the sensor part. When a angular velocity acts to the sensor, the weight 27 moves because of a Coriolis force, thereby deforming the sensor part. Electric charges are consequently generated at the detection electrode. A direction and an intensity of the angular velocity can be detected from the amount of electric charges.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piezoelectric vibration type angular velocity sensor.

[0002]

2. Description of the Related Art Angular velocity sensors capable of attitude control and position control have been developed for miniaturization and high performance for the purpose of preventing camera shake of a video camera and for use in car navigation. Although there are various types of angular velocity sensors, a piezoelectric vibration type angular velocity sensor is advantageous in terms of size and cost, and a tuning fork type, a sound piece type (quadrangular prism), a cylindrical type, a triangular prism type, and the like have been commercialized.

FIG. 1 is a structural diagram for explaining a sound piece type piezoelectric vibration angular velocity sensor. The principle of the piezoelectric vibration type angular velocity sensor is that when a rotational angular velocity (ω0) is applied around the center axis (Z axis) of a vibrating vibrator, the original vibration direction (X axis)
On the other hand, it utilizes a mechanical phenomenon that generates a Coriolis force (Fc) proportional to the rotational angular velocity in the perpendicular direction (Y-axis). Vibration is applied to the X-axis using a piezoelectric ceramic for driving, and detection provided on the Y-axis. The Coriolis force is detected as a voltage by the piezoelectric ceramic for use. The Coriolis force is generally obtained by the following equation. Fc = 2m × v × ω0 m is mass, v
Is the velocity and ω0 is the angular velocity.

If the vibration frequency is the same, the displacement of the Y-axis increases as the amplitude of the X-axis increases, and the resonance-type vibration increases the amplitude of the X-axis and increases the detection efficiency of the Y-axis in order to increase the detection voltage (sensitivity). An angular velocity sensor is advantageous. The resonating type vibration angular velocity sensor is a resonance type and can have high sensitivity, but it is difficult to adjust the vibration frequency accurately without breaking the vibration posture of the driving side and the detection side, and the vibration characteristics of the driving side and the detection side Remarkable changes in characteristics due to discrepancies or deviations, and high mechanical quality factors (Q
There are also many problems such as a low response speed due to m).

A sensor capable of detecting two-axis angular velocity with one angular velocity sensor has been desired. To meet this demand, a piezoelectric element is attached to the surface of a vibrating body and the piezoelectric element is deformed by the angular velocity. Sensors have been developed that measure the amount of changing charge to detect angular velocity. FIG. 2 is an exploded perspective view of the angular velocity sensor as viewed obliquely from above. FIG. 3 is an exploded perspective view of the same angular velocity sensor viewed obliquely from below.
A piezoelectric element 2 having an electrode 6 on the lower surface and a detection electrode 5 serving as four excitation electrodes on the upper surface is attached to the upper surface of the vibrating body 1. A piezoelectric element 3 having an electrode 7 on the upper surface and a feedback electrode 8 on the lower surface is attached to the lower surface of the vibrator 1. A weight 9 is attached to the lower surface of the return electrode 8 to form a sensor unit. In the sensor section, the bending vibration node section 4 is fixed by a cylindrical support member 10.

Since the electrode 6 and the vibrating body 1 are electrically connected and bonded to each other, when an alternating current is applied to the vibrating body 1 and the detection electrode 5 which also serves as an excitation electrode, the piezoelectric element 2 vibrates and the vibrating body 1 is brought together. Vibrate. The detection electrodes 5 also serving as four excitation electrodes are provided inside the inner diameter of the cylindrical support member 10. As shown in the figure, the cylindrical support member 10 is fixed at two places with an L-shaped wire 11, and the other end of the wire 11 is fixed to a substrate.

When an angular velocity acts on the angular velocity sensor, the weight 9 moves due to Coriolis force, thereby deforming the sensor section and generating charges on the detection electrode. The direction and intensity of the angular velocity can be detected based on the amount of charges generated on the four detection electrodes 5.

[0008]

Generally, an angular velocity sensor is manufactured so as to detect an angular velocity around a predetermined axis. Here, the predetermined axis is called a detection axis. An angular velocity sensor having two orthogonal detection axes is called a two-axis angular velocity sensor. In the case of a two-axis angular velocity sensor, the user attaches it to the object to be measured arbitrarily, so that there is preferably no difference in detection sensitivity between the two axes. However, there is a difference in the detection sensitivity of the two axes due to a processing error or an assembly error of each member. The detection sensitivity difference of two axes was reduced by changing the capacitance value and resistance value of the internal circuit. However, when the detection sensitivity difference of two axes was large, noise was amplified when the detection output around the axis with low detection sensitivity was amplified. It is amplified and it is difficult to extract an accurate detection signal. Also, the number of types of components for amplifying the detection output around the axis with low detection sensitivity increases, and the manufacturing and management costs increase. The present invention is intended to solve the problem by devising the shapes of the weight body and the vibrating body.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the conventional angular velocity sensor, and provides a small and lightweight angular velocity sensor having a small difference in detection sensitivity between two axes.

[0010] A plate-shaped vibrator, a piezoelectric element on which at least an excitation electrode and a detection electrode are formed and attached to one or both surfaces of the vibrator, a weight, and a support member for supporting the node portion The weight body is formed in a spherical shape. A through hole is provided at the center of the vibrating body, and the weight body is positioned by the through hole and fixed to the vibrating body. Thus, the center of the vibrating body and the center axis of the weight body can be easily aligned, and the difference in detection sensitivity between the two axes is eliminated.

A cylindrical portion is provided at the center of the vibrating body, and the weight is positioned by the cylindrical portion and fixed to the vibrating body. By changing the inner or outer diameter or the height of the cylindrical portion, the amount of deformation of the sensor portion changes. The maximum sensitivity can be obtained by obtaining the condition of the maximum deformation amount.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the drawings. FIG. 4 is a top view of the first embodiment of the present invention. FIG. 5 is a front sectional view of the first embodiment of the present invention. The disc-shaped vibrating body 21 is provided with a through hole 21 a centered on a central axis passing through the on-plane center 29 of the vibrating body 21. Vibrator 21
An electrode 23 is provided on the lower surface, and a detection electrode 24 also serving as four excitation electrodes is provided on the upper surface.
The disk-shaped piezoelectric element 22 provided with 5 is attached with an epoxy-based adhesive. Furthermore, the piezoelectric element 22 is arranged and attached such that the on-plane center 29 of the vibrating body 21 and the on-plane center of the piezoelectric element 22 match.

On the lower surface of the vibrating body 21, a weight 27 formed in a spherical shape is positioned and fixed on the circumference of the through hole 21a. Here, when the weight 27 is fixed to the vibrating body 21, the through hole 21 a
Are formed in such a size that they do not contact each other. If it is not formed in this way, for example, the weight 2
In the case of attaching the piezoelectric element 22 after fixing 7,
The piezoelectric element 22 is lifted from the vibrating body 21 by the weight body 27, and the thickness of the adhesive layer becomes thick and non-uniform, which adversely affects the characteristics. Or piezoelectric element 2
This is because the piezoelectric element 22 may be damaged when the piezoelectric element 2 is bonded to the vibration body 21. The through hole 21a is preferably circular, but may be formed as a polygon close to a circle if the center of gravity of the weight body 27 is located on a central axis passing through the on-plane center 29. The vibrator 21 used was an elinvar material that was a constant elastic material. The weight body 27 was made of stainless steel (SUS440C). The piezoelectric element 22 is made of PZT which is a piezoelectric ceramic.
The electrode was formed of an Ag-Cr alloy by vapor deposition.
The vibration body 21 and the weight body 27 are fixed by welding, but may be fixed by a method such as adhesion.

The vibrating body 21, the piezoelectric element 22, and the weight 27 constitute a sensor unit. The cylindrical support member 26 is adhesively fixed to a bending vibration node 28 of the angular velocity sensor. As the cylindrical support member 26, an elinvar material which is a constant elastic material was used. Note that the cylindrical support member 26 may be formed integrally with the vibrator 21. The material of the member is not limited to these as long as it satisfies the function as the angular velocity sensor.

With the center 29 on the plane of the vibrating body 21 as the origin, the X axis, the Y axis orthogonal to the X axis,
Set the Z axis orthogonal to the X and Y axes. The detection electrodes 24 also serving as the four excitation electrodes are formed on the X and Y axes and symmetrically with respect to the X and Y axes. Substantially cross-shaped return electrode 2
5 is also formed substantially symmetrically with respect to the X and Y axes. Electrode 2
Since the vibrating body 3 and the vibrating body 21 are electrically connected and bonded to each other, the vibrating body 21 and the detecting electrodes 24 serving as four excitation electrodes are also provided.
When an alternating current is applied, the piezoelectric element 22 vibrates in the Z-axis direction together with the vibrating body 21 by expanding and contracting in the radial direction. The detection electrode 24 supported by the cylindrical support member 26 and also serving as the four excitation electrodes is provided near the inner diameter of the cylindrical support member 26.

When an angular velocity acts on the angular velocity sensor, the weight 27 moves due to Coriolis force, so that the sensor section is deformed and charges are generated on the detection electrode 24. Four detection electrodes 24
The direction and intensity of the angular velocity can be detected based on the amount of electric charge generated at the time.

FIG. 6 is a top view of the second embodiment of the present invention. FIG. 7 is a front sectional view of the second embodiment of the present invention. This is an example using two piezoelectric elements. Disk-shaped vibrator 3
1 is provided with a cylindrical portion 31 a centered on a central axis passing through the on-plane center 42 of the vibrating body 31. A chamfered portion 31b is provided in the opening of the cylindrical portion 31a. Vibrator 3
On the upper surface of 1, a disk-shaped piezoelectric element 32 provided with an electrode 33 on the lower surface, four detection electrodes 34 on the upper surface, and a feedback electrode 35 having a substantially cross shape is adhered by an epoxy-based adhesive. . Furthermore, it is arranged and adhered so that the on-plane center 42 of the vibrating body 31 and the on-plane center of the piezoelectric element 32 coincide.

A donut-shaped piezoelectric element 38 having an electrode 36 on the upper surface and an excitation electrode 37 on the lower surface is attached to the lower surface of the vibrating body 31 with an epoxy-based adhesive.
Further, the piezoelectric element 38 is positioned by the cylindrical portion 31a of the vibrating body 31 so that the on-plane center 42 of the vibrating body 31 and the on-plane center of the piezoelectric element 38 coincide. The spherical weight body 39 is provided with the chamfered portion 3 provided on the cylindrical portion 31a.
1b and is fixed. Cylindrical part 31a
Is provided, and the inner or outer diameter or height of the cylindrical portion 31a is changed,
The maximum sensitivity can be obtained by obtaining a condition that maximizes the amount of deformation of the sensor unit. Further, in the second embodiment, the cylindrical portion 31a also functions as a positioning guide for the piezoelectric element 38. The weight body 39 is in contact only with the cylindrical portion 31a. This is because if it comes into contact with another part, the positioning of the weight body cannot be accurately performed. The vibrating body 31 used was an elinvar material that was a constant elastic material. The weight body 39 was made of stainless steel (SUS440C). Piezoelectric elements 32, 38
Is made of PZT, which is a piezoelectric ceramic, and the electrodes are formed of an Ag-Cr alloy by vapor deposition. The cylindrical portion 31a and the weight body 39 are fixed by welding, but may be fixed by a method such as adhesion.

The sensor section is constituted by the vibrating body 31, the piezoelectric elements 32 and 38, and the weight body 39. Cylindrical support member 40
Is the bending vibration node 4 of the angular velocity sensor.
1 is fixedly adhered. For the cylindrical support member 40, an elinvar material which is a constant elastic material was used. The cylindrical support member 4
0 may be formed integrally with the vibrator 31. The material of the member is not limited to these as long as it satisfies the function as the angular velocity sensor.

With the center 42 on the plane of the vibrating body 31 as the origin, the X axis, the Y axis orthogonal to the X axis,
Set the Z axis orthogonal to the X and Y axes. Four detection electrodes 3
Reference numeral 4 is formed on the X and Y axes and symmetrically with respect to the X and Y axes. The substantially cross-shaped feedback electrode 35 is also formed substantially symmetrically with respect to the X and Y axes. Since the electrode 36 and the vibrating body 31 are electrically connected and adhered to each other, when an alternating current is applied to the vibrating body 31 and the excitation electrode 37, the piezoelectric element 38 expands and contracts in the radial direction, so that the piezoelectric element 38 and the vibrating body 31 are joined together. Vibrates in the Z-axis direction. It is supported by a cylindrical support member 40, and the four detection electrodes 24 are provided near the inner diameter of the cylindrical support member 40.

When an angular velocity acts on the angular velocity sensor, the weight 39 moves due to Coriolis force, thereby deforming the sensor section and generating charges on the detection electrode. The direction and intensity of the angular velocity can be detected based on the amount of charge generated in the four detection electrodes 34.

FIG. 8 is a top view of the third embodiment of the present invention. FIG. 9 is a front sectional view of a third embodiment of the present invention. In the disk-shaped vibrating body 51, grooves 51a, 51b concentrically U-shaped around the on-plane center 52 of the vibrating body 51,
The circular concave portion 51c is provided on the same surface side as the circular concave portion 51c. The cylindrical portion 51d is formed by the groove 51a and the concave portion 51c. The grooves 51a, 51b, 51c and the concave portion 51c are formed by etching, but any processing method can be used as long as a similar shape can be obtained. An electrode 53 is provided on the lower surface on the upper surface of the vibrating body 51, and a detection electrode 54 serving also as four excitation electrodes is provided on the upper surface.
And a disk-shaped piezoelectric element 56 provided with a substantially cross-shaped return electrode 55 is attached with an epoxy-based adhesive.
Furthermore, it is arranged and adhered so that the on-plane center 52 of the vibrating body 51 and the on-plane center of the piezoelectric element 56 coincide.

On the lower surface of the vibrating body 51, a spherical weight body 57 is positioned and fixed on the circumference of the cylindrical portion 51d. The weight body 57 is in contact only with the cylindrical portion 51d. This is because if it comes into contact with the flat portion of the concave portion 51c, the positioning of the weight body cannot be accurately performed. The vibrator 51 used was an elinvar material that was a constant elastic material. The weight body 57 was made of stainless steel (SUS440C). The piezoelectric element 56 was made of PZT, which is a piezoelectric ceramic, and the electrodes were formed of an Ag-Cr alloy by vapor deposition. Vibrator 51
The weight 57 is fixed by welding, but may be fixed by a method such as adhesion.

The vibrating body 51, the piezoelectric element 56 and the weight body 57 constitute a sensor section. Here, the groove 51b is formed near the node portion 58 of the bending vibration of the sensor portion. The cylindrical support member 59 is bonded and fixed to the groove 51b so as to support the bending vibration node portion 58 of the sensor portion. As the cylindrical support member 59, an elinvar material which is a constant elastic material was used. The material of the member is not limited to these as long as it satisfies the function as the angular velocity sensor.

The method of detecting the angular velocity is the same as in the first embodiment, and will not be described. In the third embodiment, since the vibrating body is a plate-shaped member, and there is no projection such as the cylindrical portion 31a from the main surface, the plate thickness can be uniformly and accurately processed by a method such as wrapping. Therefore, the excitation frequency becomes more stable,
It is preferable to increase the detection accuracy.

[0026]

According to the present invention, the following effects can be obtained by employing the above-described structure. The detection sensitivity of 12 axes becomes equal. 2 The influence of noise is reduced, and the detection accuracy is increased. 3. The number of circuit components (resistance, capacitor) can be reduced,
Manufacturing costs are reduced. 4 The sensitivity is increased by providing the cylindrical part. (5) Since the positioning of the weight body can be easily performed with high accuracy, the number of steps can be reduced, the cost can be reduced, and the detection accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a structural diagram for explaining a sound piece type piezoelectric vibration angular velocity sensor.

FIG. 2 is an exploded perspective view of a conventional example of an angular velocity sensor according to the present invention as viewed obliquely from above.

FIG. 3 is an exploded perspective view of a conventional example of an angular velocity sensor according to the present invention as viewed obliquely from below.

FIG. 4 is a top view of the first embodiment of the angular velocity sensor according to the present invention.

FIG. 5 is a front sectional view of the first embodiment of the angular velocity sensor according to the present invention.

FIG. 6 is a top view of an angular velocity sensor according to a second embodiment of the present invention.

FIG. 7 is a front sectional view of a second embodiment of the angular velocity sensor according to the present invention.

FIG. 8 is a top view of a third embodiment of the angular velocity sensor according to the present invention.

FIG. 9 is a front sectional view of an angular velocity sensor according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vibration body 2 Piezoelectric element 3 Piezoelectric element 4 Node part 5 Detection electrode 6 also serving as excitation electrode 6 Electrode 7 Electrode 8 Return electrode 9 Weight body 10 Cylindrical support member 11 Wire 21 Vibration body 21a Through hole 22 Piezoelectric element 23 Electrode 24 Excitation Detection electrode 25 also serving as electrode 25 Return electrode 26 Cylindrical support member 27 Weight body 28 Node part 29 Center on surface 31 Vibration body 31a Cylindrical part 31b Chamfered part 32 Piezoelectric element 33 Electrode 34 Detection electrode 35 Feedback electrode 36 Electrode 37 Excitation electrode 38 Piezoelectric element 39 Weight body 40 Cylindrical support member 41 Node part 42 Center on plane 51 Vibration body 51a Groove 51b Groove 51c Concave part 51d Cylindrical part 52 Center on plane 53 Electrode 54 Detection electrode 55 also serving as excitation electrode 55 Feedback electrode 56 Piezoelectric element 57 Weight body 58 Node part 59 Cylindrical support member

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Minoru Hatakeyama 4107 Miyota, Miyoshida-cho, Kitasaku-gun, Nagano Prefecture 5 Inside Miyota Co., Ltd. (72) Inventor Kazutoyo Ichikawa 4107 Miyoshida, Miyoshida-cho, Kitasaku-gun, Nagano prefecture Inside Miyota Co., Ltd. (72) Inventor Hiroaki Terao 4107 Miyoshida, Miyoshida-cho, Kitasaku-gun, Nagano Pref. Inside Miyota Co., Ltd. (72) Inventor Masato Handa 4107 Miyoshida, Miyoda-cho, Kitasaku-gun, Nagano Pref.

Claims (3)

[Claims] 1. A plate-shaped vibrating body, a piezoelectric element on which at least an excitation electrode and a detecting electrode are formed and attached to one or both sides of the vibrating body, a weight body, and a supporting member for supporting a node portion An angular velocity sensor comprising: the weight body having a spherical shape; 2. The angular velocity sensor according to claim 1, wherein a through hole is provided at the center of the vibrating body, and the weight is positioned by the through hole and fixed to the vibrating body. 3. The angular velocity sensor according to claim 1, wherein a cylindrical portion is provided at the center of the vibrator, and the weight is positioned by the cylindrical portion and fixed to the vibrator.