JPH10160480A - Angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of the mechanical quality coefficient by forming a groove in the vicinity of a node part of bending vibration of a vibrating body, and supporting the groove with a supporting member. SOLUTION: The sensor part 20 is constituted of a vibrating body 21, a piezoelectric element 23 and a weight 28. The piezoelectric element 23 is attached to the upper face of the vibrating body 21, and a detection electrode 24, a feedback electrode 25 are set on the upper face of the piezoelectric element 23. An electrode 27 is set on the lower face of the piezoelectric element 23. The weight 28 having a center axis agreeing with a Z axis is attached to the lower face of the vibrating body 21. A U-shaped groove 21a is formed in the vicinity of a node part 26 of the vibrating body 21, which is supported by a cylindrical supporting member 29. The vibration state is stabilized more as the groove 21a is closer to the node part 26. When an angular velocity acts to the sensor, the weight 28 moves because of a Coriolis force, thereby deforming the sensor part 20. Electric charges are generated at the detection electrode 24. A direction and a size of the angular velocity are detected from the amount of the 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 a direction perpendicular to the axis (Y axis). The Coriolis force is detected as a voltage by the piezoelectric ceramics. The Coriolis force is generally obtained by the following equation. Fc = 2m × v × ω0 m is mass, v is velocity, and ω0 is 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).

[0005] It has been desired that one angular velocity sensor can detect angular velocities around two axes. (Hereinafter, an angular velocity sensor capable of detecting angular velocities around two axes is referred to as a two-axis angular velocity sensor.) In response to this demand, a piezoelectric element (hereinafter, a material exhibiting a piezoelectric effect is collectively referred to as a piezoelectric element on the surface of a vibrating body) A sensor has been developed that detects the angular velocity by measuring the amount of electric charge that changes when the piezoelectric element is deformed by the angular velocity after attaching the piezoelectric element. 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. On the upper surface of the vibrating body 1,
The piezoelectric element 2 having the electrode 6 on the lower surface and the detection electrode 5 serving also as four excitation electrodes on the upper surface is attached. Vibrator 1
The piezoelectric element 3 having the electrode 7 on the upper surface and the feedback electrode 8 on the lower surface is attached to the lower surface of the piezoelectric element 3. 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 electric charges on the four detection electrodes 5. Four detection electrodes 5
The direction and intensity of the angular velocity can be detected based on the amount of electric charge generated at the time.

An origin is set at the center of the plane including the vibrating body 1,
X axis on the same plane, Y axis orthogonal to the X axis on the same plane, X
Set the Z axis perpendicular to the axis and the Y axis. Although there are many types of vibration modes, the vibration modes used as the angular velocity sensor include a vibration mode in the Z-axis direction (vertical direction) in which the weight body 9 vibrates in the vertical direction as shown in FIGS. 7, a vibration mode in the X and Y axis directions (lateral direction) in which the weight body 9 swings in the horizontal direction is used.

FIG. 4 is a cross-sectional view showing a vibration mode in the Z-axis direction, showing a state in which the vibration mode swings in the Z-axis plus direction. FIG. 5 is a cross-sectional view showing the vibration mode in the Z-axis direction, and shows a state in which the vibration mode swings in the Z-axis minus direction. The resonance frequency in the vibration mode in the Z-axis direction is called the resonance frequency in the Z-axis direction. The vibration mode in the Z-axis direction is used as a drive (excitation) mode. The node part 4 exists inside the vibrating body 1 as shown in the figure. In this conventional example, the node portion 4 is connected to a cylindrical support member 10.
Indirectly support in.

FIG. 6 is a cross-sectional view showing a vibration mode in the X-axis direction, showing a state in which the vibration mode swings in the X-axis plus direction. FIG. 7 is a cross-sectional view showing a vibration mode in the X-axis direction, and shows a state of swinging in the X-axis minus direction. Since the same applies to the Y axis, only the X axis direction is shown. The resonance frequency in the vibration mode in the X and Y axis directions is called the resonance frequency of the weight body. The vibration mode in the X and Y axis directions is used as a detection mode. Generally, in a resonance type angular velocity sensor, the detection sensitivity increases when the resonance frequencies of the drive mode and the detection mode are close.

[0011]

In the case of a resonance type angular velocity sensor, in order to increase the detection sensitivity, as described above, the resonance frequency of the drive (excitation) mode and the detection mode, for example, the laser beam is applied to the weight body. It is advisable to use the method of irradiating and trimming to get closer. As a premise, the mechanical quality factor (Qm)
Needs to be set to some high level. If the mechanical quality factor (Qm) is too high, there is a problem that the response speed becomes slow. However, if the mechanical quality factor (Qm) is high to some extent, the vibration mode is stabilized and the detection sensitivity is increased. Conversely, if the mechanical quality factor (Qm) is low, the strength of resonance will be low not only in the drive mode but also in the detection mode, and it will not be possible to give sufficient deformation to the piezoelectric element. Therefore, the amount of charges generated from the detection electrode is reduced, and the detection sensitivity is reduced. In the conventional example,
Since the cylindrical support member 10 indirectly supports the node portion of the sensor unit via the piezoelectric element 3, the cylindrical support member 10 is also periodically deformed when excited. Therefore, the mechanical quality factor (Qm) is lower than before supporting. In addition, when the assembly error is large, a portion further deviating from the node portion is supported, and the mechanical quality factor (Qm) is significantly reduced. Further, in order to increase the detection accuracy, it is necessary to stabilize the vibration mode.

[0012]

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 high detection sensitivity and detection accuracy.

A plate-shaped vibrator, a piezoelectric element having at least an excitation electrode and a detection electrode formed thereon and attached to one or both surfaces of the vibrator, a weight, and a support member for supporting the node portion In the angular velocity sensor having the groove, a groove is formed in the vicinity of the node of the bending vibration of the vibrating body, and the support member supports the groove. With such a configuration, the supporting member can directly support the node portion almost directly, stabilizing the vibration mode, and suppressing a decrease in the mechanical quality factor (Qm). Thereby, both the detection sensitivity and the detection accuracy are improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the drawings. FIG. 8 is a top view of the first embodiment of the present invention. FIG. 9 is a front sectional view of the first embodiment of the present invention. An XYZ three-dimensional orthogonal coordinate system is set as shown in FIGS. An origin 22 is set at the center of the plane including the vibrating body 21 and X
The axis, the Y axis orthogonal to the X axis on the same plane, the X axis, and the Z axis orthogonal to the Y axis are set. A disc-shaped piezoelectric element 23 is attached to the upper surface of the vibrating body 21 so that the center on the surface and the origin 22 coincide. On the upper surface of the piezoelectric element 23, four fan-shaped detection electrodes 24 also serving as excitation electrodes and a substantially cross-shaped feedback electrode 25 are provided inside from near the node portion 26. The detection electrode 24 also serving as the four excitation electrodes is X
It is arranged on the axis and the Y axis, and is formed line-symmetrically with respect to the X and Y axes. The cross-shaped return electrode 25 is also X
It is formed substantially symmetrically with respect to the axis and the Y axis. Piezoelectric element 2
On the lower surface of 3, an electrode 2 having a circular shape slightly larger than the outer shape of the detection electrode 24 also serving as four excitation electrodes centered on the origin 22.
7 are provided.

A weight 28 is attached to the lower surface of the vibrating body 21, and the center axis of the weight 28 coincides with the Z axis. Here, the weight body 28 is formed in a shape in which two cylinders are overlapped with their central axes aligned. In the first embodiment, the shape in which the weight is formed by combining the cylinder with the weight is used, but the shape is not limited as long as the weight is formed so as to have the center of gravity on the central axis. However, for easy and accurate processing, a cylinder or a combination of cylinders is preferable. The fixing method may be welding or the like. Vibrator 21 and piezoelectric element 23
And the weight body 28 constitute the sensor section 20. Vibrator 2
1 is provided with a U-shaped groove 21 a near the node portion 26. Depending on the shape of the sensor unit 20, the node unit 2
6 are different from each other, so that the shape of the
The shape of 1a is determined. The cylindrical support member 29 has the groove 21
a. Although the adhesive is used for fixing the cylindrical support member 29, welding or the like may be used. The adhesive may be filled in the groove 21a. Here, for example, when an elastic adhesive is used, vibration leakage can be reduced. The groove 21a is used to connect the node portion 26 to the cylindrical support member 29.
Is most preferably formed at a position where it can be directly supported. Actually, due to processing errors and assembly errors, the node section 26
Is slightly changed, and it is difficult for the cylindrical support member 29 to directly support the node portion 26. However, as the groove 21a is closer to the node portion, the vibration leaking to the cylindrical support member 29 is reduced, and the vibration mode is changed. Becomes stable.

The vibrating body 21 uses an elinvar material as a constant elastic material, and the piezoelectric element 23 uses PZT. The vibrating body 21 and the piezoelectric element 23 were bonded using an epoxy adhesive.
Electrodes were formed on the plane of the piezoelectric element 23 by a thin film of an alloy such as Ag-Cr or Ni-Cr by vapor deposition. The electrodes may be formed by a method such as sputtering or screen printing. The weight body 28 and the cylindrical support member 29 are made of an elinvar material. The material is not limited to this as long as it satisfies a predetermined function.

Since the electrode 27 and the vibrating body 21 are electrically connected and adhered to each other, when an alternating current is applied to the vibrating body 21 and the detection electrode 24 serving also as four excitation electrodes, the piezoelectric element 23
Is Z together with the vibrating body 21 by expanding and contracting in the radial direction.
Vibrates in the axial direction. The detection electrode 24 supported by the cylindrical support member 29 and also serving as the four excitation electrodes is provided from the vicinity of the inner diameter of the cylindrical support member 29 to the inside.

When an angular velocity acts on the angular velocity sensor, the weight body 28 moves by Coriolis force, thereby deforming the sensor section 20 and generating charges on the detection electrodes 24 which also serve as four excitation electrodes. The direction and magnitude of the angular velocity can be detected based on the amount of charge generated on the detection electrode 24 also serving as the four excitation electrodes.

FIG. 10 is a top view of the second embodiment of the present invention. FIG. 11 is a front sectional view of the second embodiment of the present invention.
In the first embodiment, one piezoelectric element is used, whereas in the second embodiment, a sensor unit is configured by using two piezoelectric elements.

An XYZ three-dimensional orthogonal coordinate system is set as shown in FIGS. An origin 42 is determined at the center of the plane including the vibrating body 41, and an X axis is set on the plane, a Y axis orthogonal to the X axis on the plane, and a Z axis orthogonal to the X axis and the Y axis. A disk-shaped piezoelectric element 43 is attached to the upper surface of the vibrating body 41 such that the center on the surface and the origin 42 coincide. On the upper surface of the piezoelectric element 43, four fan-shaped detection electrodes 44 and a substantially cross-shaped feedback electrode 45 are provided from the vicinity of the node portion 46 to the inside. The four detection electrodes 44 are X axis, Y
It is formed on the axis and symmetrically with respect to the X axis and the Y axis. The substantially cross-shaped feedback electrode 25 is also formed substantially symmetrically with respect to the X axis and the Y axis. On the lower surface of the piezoelectric element 43, an electrode 47 having a circular shape slightly larger than the outer shape of the four detection electrodes 44 is provided around the origin 42.

On the lower surface of the vibrating body 41, a donut-shaped piezoelectric element 48 having a disk shape smaller in diameter than the inner diameter of a cylindrical support member 52 to be described later and having a through hole at the center is provided on the lower surface. It is affixed so as to coincide with the center and the origin 42. On the upper surface of the piezoelectric element 48, an electrode 49 having an annular shape centered on the center on the surface is provided. The lower surface of the piezoelectric element 48 is provided with an excitation electrode 50 having an annular shape centered on the center on the surface. Further, the vibrating body 4
A weight body 51 is attached to the lower surface of 1, and the central axis of the weight body 51 coincides with the Z axis. Here, the weight body 51 is formed in a shape in which the center axes of the two cylinders 51a and 51b are aligned and overlapped. The through hole of the piezoelectric element 48 is formed to be larger than the diameter of the column 51a. Also in the second embodiment, a shape obtained by combining a cylinder with a weight body was used, but as described in the first embodiment, any shape may be used as long as it is formed to have a center of gravity on its central axis. . The fixing method may be welding or the like. Vibrating body 41 and piezoelectric element 43,
The sensor unit 40 is composed of the weight 48 and the weight 51. The vibrating body 41 has a U-shaped groove 41 near the node portion 46.
a is provided. Since the position of the node portion 46 differs depending on the shape of the sensor portion 40, the shape of the groove 41a is determined by the shape of the sensor portion 40. The cylindrical support member 52 supports the groove 41a. The supporting method used an adhesive,
It may be welding. Further, the adhesive may be filled in the groove 41a. Here, for example, when an elastic adhesive is used, vibration leakage can be reduced. Groove 41a
It is most preferable to form the node portion 46 at a position where the cylindrical support member 52 can directly support the node portion 46. Actually, the position of the node portion 46 is slightly changed due to a processing error and an assembly error, and it is difficult for the cylindrical support member 52 to directly support the node portion 46. However, the closer the groove 41a is to the node portion, the more the cylindrical portion becomes. The vibration leaking to the support member 52 is reduced, and the vibration state is stabilized.

The vibrating body 41 uses an elinvar material as a constant elastic material, and the piezoelectric elements 43 and 48 use PZT. The vibrating body 41 and the piezoelectric elements 43 and 48 were bonded using an epoxy-based adhesive. Electrodes were formed on the flat surfaces of the piezoelectric elements 43 and 48 by vapor deposition using a thin film of an alloy such as Ag-Cr or Ni-Cr. The electrodes may be formed by a method such as sputtering or screen printing. The weight body 51 and the cylindrical support member 52 are made of an elinvar material. The material is not limited to this as long as it satisfies a predetermined function.

Since the electrode 49 and the vibrating body 41 are electrically connected and adhered to each other, when an alternating current is applied to the vibrating body 41 and the excitation electrode 50, the piezoelectric element 48 expands and contracts in the radial direction, thereby causing the vibrating body 41 to expand and contract. Vibrates in the Z-axis direction together with. It is supported by a cylindrical support member 52, and the four detection electrodes 44 are provided from near the inner diameter of the cylindrical support member 52 to the inside.

When an angular velocity acts on the angular velocity sensor, the weight 51 moves by Coriolis force, so that the sensor section 40 is deformed and electric charges are generated on the four detection electrodes 44. The direction and magnitude of the angular velocity can be detected based on the amount of charge generated on the four detection electrodes 44.

[0025]

According to the present invention, the following effects can be obtained by employing the above-described structure. (1) By providing a groove in the vibrating body and supporting the groove, the supporting member can directly support the node portion almost stably, and the vibration state is stabilized. (2) A decrease in the mechanical quality factor (Qm) can be suppressed. 3 Both detection sensitivity and detection accuracy are 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 sectional view showing a vibration mode in the Z-axis direction of a conventional example of the angular velocity sensor according to the present invention.

FIG. 5 is a sectional view showing a vibration mode in the Z-axis direction of a conventional example of the angular velocity sensor according to the present invention.

FIG. 6 is a sectional view showing a vibration mode in the X and Y axis directions of a conventional example of the angular velocity sensor according to the present invention.

FIG. 7 is a cross-sectional view showing a vibration mode in the X and Y axis directions of a conventional example of the angular velocity sensor according to the present invention.

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

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

FIG. 10 is a top view of an angular velocity sensor according to a second embodiment of the present invention.

FIG. 11 is a front sectional view of a second embodiment of the angular velocity sensor according to 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 serving also as excitation electrode 6 Electrode 7 Electrode 8 Return electrode 9 Weight body 10 Cylindrical support member 11 Wire 20 Sensor part 21 Vibration body 21a Groove 22 Origin 23 Piezoelectric element 24 Detection electrode also serving as excitation electrode 25 Return electrode 26 Node part 27 Electrode 28 Weight body 29 Cylindrical support member 40 Sensor part 41 Vibration body 41a Groove 42 Origin 43 Piezoelectric element 44 Detection electrode 45 Feedback electrode 46 Node part 47 Electrode 48 Piezoelectric Element 49 Electrode 50 Excitation electrode 51 Weight 51a Column 51b Column 52 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) Keiya Okada, Inventor 4107, Miyoshida, Miyoshida-cho, Kitasaku-gun, Nagano Prefecture 5 Inside Miyota Co., Ltd. (72) Inventor Masato Handa, 4107 Miyoshida, Miyoda-machi, Kitasaku-gun, Nagano Prefecture, Japan 5 Inside

Claims (1)

[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 The angular velocity sensor according to claim 1, wherein a groove is formed near a node portion of the bending vibration of the vibrating body, and the support member supports the groove.