JPH10260044A - Piezoelectric vibration gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric vibration gyro of simple construction and manufacture, and small size and high accuracy, by forming partial electrodes for driving and for detecting on the respective apex positions of a specified isosceles triangle arranged in secific constitution. SOLUTION: The territory surrounded with first-third partial electrodes 11, 12, 13 is only polarized in the thickness direction of a piezoelectric rectangular plate 10. In this way, when the territory surrounded with the partial electrodes 11-13 is only polarized, the piezoelectric characteristics of the polarized territory and the not polarized territory are different from each other, and hence a confined energy condition becomes favorable. When drive voltage is impressed between the second and third partial electrodes 12, 13, vibration in the X-direction is excited. When the piezoelectric rectangular plate 10 is rotated around the Z-axis under this condition, vibration due to Coriolis force is generated in the Y-direction, and hence potential diference is generated between the second and third partial electrodes 12, 13. By detecting the potential difference, intensity of the vibration due to the Coriolis force, consequently, rotary angular velocity can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric vibratory gyroscope utilizing ultrasonic vibration of a piezoelectric vibrator, among gyroscopes used for a camera navigation system and a camera-body type VTR camera. The present invention relates to a piezoelectric vibrating gyroscope that uses an energy trapping vibration mode as a vibration mode of a vibrator, has a simple structure, is easily supported, and has excellent vibration resistance and shock resistance.

[0002]

2. Description of the Related Art A piezoelectric vibrating gyroscope (hereinafter simply referred to as a piezoelectric vibrating gyroscope) is a state in which a piezoelectric vibrator is excited in a certain direction, and the piezoelectric vibrator is driven in an axis perpendicular to the vibration direction. When it rotates around the, it detects the Coriolis force generated in the direction of its excitation and in the direction perpendicular to the rotation axis.
It detects rotational angular velocity and has various applications. Recently, for example, navigation systems for automobiles,
It is used for a camera shake correction mechanism of a VTR camera.

As a piezoelectric vibrating gyroscope, a piezoelectric vibrating gyroscope utilizing an energy trapping vibration mode using a piezoelectric vibrator vibrating in an energy trapping vibration mode in which the energy of the vibration is concentrated in the vicinity of the drive electrode is disclosed in, for example, Japanese Patent Application Laid-Open Publication No. Sho. 62-162915 (hereinafter referred to as prior art 1). The piezoelectric vibratory gyroscope using this energy trapping vibration mode is that the vibration energy is concentrated on the local part of the piezoelectric vibrator, so the support of the piezoelectric vibrator is easy and easy, and the separated lead wire is unnecessary. There are advantages.

In prior art 1, in order to confine vibration energy locally, the thickness of the vibrator is locally increased, the portion is polarized in the thickness direction, and a driving electrode is provided on the opposite end surface of the thick local portion. A device provided with a detection electrode on a side surface is disclosed. As another example, there is disclosed one in which a drive electrode and a detection electrode are provided on one surface of a piezoelectric rectangular plate, and interdigital electrodes are provided between the drive electrodes as detection electrodes.

[0005]

In the piezoelectric vibrating gyroscope using the energy trapping vibration mode disclosed in the prior art 1, the thickness of the piezoelectric rectangular plate must be locally increased or the interdigital electrodes are formed. Manufacturing difficulties. In addition, since the pair of drive electrodes and the pair of detection electrodes are provided near each other, the drive electric field applied from the drive electrodes to the piezoelectric rectangular plate is affected by the detection electrodes, and the direction of the drive electric field changes to improve accuracy. The disadvantage is that it cannot be performed.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a piezoelectric vibrating gyroscope that is small in size, simple in structure and manufacturing, and utilizes a high-precision energy trapping vibration mode.

[0007]

According to the present invention, a vertical bisector of the apex angle is formed on at least one principal surface of a piezoelectric rectangular plate having a polarization axis component in a thickness direction by any one of the piezoelectric rectangular plates. A piezoelectric vibrating gyroscope is obtained in which three driving and detecting partial electrodes are formed at the vertices of an isosceles triangle including an equilateral triangle disposed so as to be parallel to one of the sides. .

According to the present invention, in the piezoelectric vibrating gyroscope, a vertex of the apex angle is set at each vertex of an isosceles triangle including an equilateral triangle in which the perpendicular bisector of the apex angle is arranged in parallel with a long side of the piezoelectric rectangular plate. A piezoelectric vibrating gyroscope is characterized in that an external connection electrode is drawn out substantially symmetrically with respect to a center line in the longitudinal direction of the main surface of the piezoelectric rectangular plate in the vicinity of an end portion closer to each of the partial electrodes at the position. can get.

Further, according to the present invention, in the piezoelectric vibrating gyroscope, in the piezoelectric vibrating gyroscope, a vertical bisector of the apex angle is defined by an apex angle of an isosceles triangle including an equilateral triangle arranged in parallel with a short side of the piezoelectric rectangular plate. From the partial electrode at the position, toward the both ends, and from the partial electrode at the base angle, toward the near end, the external connection electrodes are substantially symmetric with respect to the vertical bisector. A piezoelectric vibrating gyroscope characterized by being drawn out is obtained.

According to the present invention, there is provided a piezoelectric vibrating gyroscope in which, in any one of the piezoelectric vibrating gyroscopes, only the both ends in the long side direction of the piezoelectric rectangular plate are supported and fixed.

Further, according to the present invention, in any one of the piezoelectric vibrating gyroscopes, only the region including the three partial electrodes of the piezoelectric rectangular plate and surrounded by these partial electrodes is polarized in the thickness direction. Thus, a piezoelectric vibrating gyroscope is obtained.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing a configuration of a piezoelectric vibrator of an energy trap type piezoelectric vibrating gyroscope according to a first embodiment of the present invention. As shown in FIG. 1, the piezoelectric vibrator 1 uses, for example, a piezoelectric rectangular plate 10 made of a piezoelectric ceramics plate such as PZT or barium titanate and having only a central portion polarized in the thickness direction. This piezoelectric rectangular plate 10
On the main surface of the central portion, the electrodes of the same size in the form of strips are placed at positions symmetrical with respect to the perpendicular bisector of at least one vertex of an equilateral triangle. ,
And third partial electrodes 11, 12, and 13 are formed. At this time, the vertical bisector is configured to be parallel to any one side of the piezoelectric rectangular plate 10.

The first, second, and third partial electrodes 1
First, second, and third extraction electrode portions 14, 15, 16 for leading out to the outside are connected to 1, 12, and 13, respectively. At this time, the piezoelectric rectangular plate 10 includes three first to third partial electrodes 11, as shown by broken lines in FIG.
Only the region surrounded by 12 and 13 is polarized in the thickness direction of the piezoelectric rectangular plate 10. As described above, when only the region surrounded by the first to third partial electrodes 11, 12, and 13 is polarized, the piezoelectric characteristics of the polarized region and the non-polarized region change, so that energy confinement is prevented. The condition improves.

The first to third partial electrodes 1
1, 12, 13 and the first to third extraction electrode portions 14,
15 and 16 are preferably made of silver paste or gold sputter. Of course, other conductive films can be used. Note that, in FIG. 1, diagonal lines indicate a partial electrode and an extraction electrode portion.

As shown in FIG. 1, three-dimensional coordinates are defined with the thickness direction being the Z axis, the front direction of the first electrode being the X axis, and the direction orthogonal to these being the Y axis. The first partial electrode 11 and the second
When a drive voltage (alternating current) is applied between the first electrode and the third partial electrodes 12 and 13, vibration in the X direction is excited. When the piezoelectric rectangular plate 10 rotates around the Z axis in this state, a vibration is generated in the Y direction due to the Coriolis force.
Then, a potential difference occurs between the third partial electrodes 12 and 13. By detecting this potential difference, it is possible to detect the magnitude of the vibration due to the Coriolis force, and hence the rotational angular velocity.

Since the energy of the vibration is confined in the central portion of the piezoelectric rectangular plate and does not reach the periphery, it is easy to support the peripheral portion of the piezoelectric rectangular plate 10.

FIG. 2 is a block diagram showing a circuit configuration connected to the piezoelectric vibrator 1 of FIG. Referring to FIG. 2, the second and third partial electrodes 12 and 13 of the piezoelectric vibrator 1 include:
First and second current detection circuits 18 and 19 are connected respectively. A differential amplifier circuit 22 is connected to the output sides of the first and second current detection circuits 18 and 19, and outputs a sensor output of a piezoelectric vibrating gyroscope via a synchronous detection circuit 23 and a rectification circuit 24.

On the other hand, the first and second current detection circuits 18,
Reference numeral 19 is connected to an oscillation circuit 25 for satisfying the self-excited oscillation condition.
To form a self-excited oscillation circuit. An AC voltage having a frequency substantially equal to the resonance frequency of the thickness shear vibration of the piezoelectric vibrator 1 is applied to the first partial electrode 11 by the self-excited oscillation circuit.

FIG. 3 is a diagram showing an example of the configuration of a current detection circuit having a virtual grounding function used in a piezoelectric vibrating gyroscope utilizing the energy confinement vibration mode of FIG. The non-inverting input terminal of the operational amplifier 27 is grounded to the reference voltage.
A resistor is connected from the output terminal of the operational amplifier 27 to the inverting input terminal, and the inverting input terminal is always kept at the reference potential by the virtual ground function of the operational amplifier 27. When a current flows into this inverting input terminal, it is converted into a voltage by a resistor. Therefore, the first and second current detection circuits 1 shown in FIG.
8, 19 are functionally with almost zero input impedance.
This is a circuit that can obtain an output voltage proportional to the input current.

FIG. 4 is a plan view showing a structure of a piezoelectric vibrating gyroscope according to a second embodiment of the present invention. As shown in FIG. 4, a vertical bisector of the apex angle is disposed substantially at the center of one surface of the piezoelectric rectangular plate 30 made of piezoelectric ceramics so as to be parallel to the long side of the piezoelectric rectangular plate 30. First, second, and third partial electrodes 31, 32, and 3333 are formed at the positions of the vertices of the equilateral triangle.
The first, second, and second are located near the ends closer to
The third external connection electrodes 34, 35, and 36 are drawn out substantially symmetrically with respect to the center line in the length direction of the main surface of the piezoelectric rectangular plate 30. As described above, the first partial electrode 3
1, a driving voltage is applied to the second and third partial electrodes 32,
By making the detection electrode 33 also serve as a ground electrode,
A piezoelectric vibrating gyroscope can be configured. When the partial electrodes 31, 32, and 33 are arranged as shown in FIG. Due to the symmetry, the amplitude and the phase of the voltage generated on the detection electrode by the excitation vibration become equal when the piezoelectric vibrating gyroscope itself is stationary. Reference numerals 37a and 37b indicate end portions of a support member that supports both ends of the piezoelectric rectangular plate 30.

FIG. 5 is a plan view showing the structure of a piezoelectric vibrating gyroscope according to a third embodiment of the present invention. As shown in FIG. 5, a vertical bisector of the apex angle is arranged at a substantially central portion of one surface of a piezoelectric rectangular plate 30 made of piezoelectric ceramics so as to be parallel to a short side of the piezoelectric rectangular plate. At the position of each vertex of the equilateral triangle, the first, second, and third partial electrodes 41,
The first and second external connection electrodes 42 and 43 are formed from the partial electrode 41 at the apex angle to the vicinity of both ends and from the partial electrode at the base angle to the near end, respectively. 44 and 45, second and third external connection electrodes 47,
46 are drawn out substantially symmetrically with respect to the center line in the length direction of the main surface of the piezoelectric rectangular plate 30. As described above, a driving voltage is applied to the first partial electrode 41, and the second and third partial electrodes 42 and 43 are detection electrodes which also serve as ground electrodes, whereby a piezoelectric vibrating gyroscope can be formed. I can do it.

When the respective partial electrodes are arranged as shown in FIG. 5, the excitation vibration direction is perpendicular to the length direction of the piezoelectric rectangular plate 30, and the second and the second detection electrodes as two detection electrodes respond to the excitation vibration. Since the third partial electrodes 42 and 43 are geometrically symmetric, the amplitude and the phase of the voltage generated at the detection electrode by the excitation vibration become equal when the piezoelectric vibrating gyroscope itself is stationary.

FIG. 6 is a perspective view showing a support structure of a piezoelectric vibrating gyroscope according to an embodiment of the present invention. As shown in FIG. 6, when the structure of the piezoelectric vibrating gyroscope is the structure as shown in FIGS. 4 and 5, the piezoelectric vibrating gyroscope has support members at both ends of the piezoelectric rectangular plate 30 as shown in FIG. On the step portions 37d, 37d provided at both ends of the 37, it is possible to provide a gap 37e between the bottom portion 37c of the support portion and the central portion of the piezoelectric ceramic rectangular plate 30 to support.

When the shape of the piezoelectric rectangular plate 30 is as shown in FIGS. 4 and 5, the vibration energy is reflected at the end face in the width direction and is not a pure energy confinement vibration. By properly selecting the electrode and the dimensions of the electrode, practically usable characteristics can be obtained.

As described above, in the piezoelectric vibrating gyroscope according to the present invention, as described above, the rotation axis to be detected is the axis in the thickness direction of the piezoelectric rectangular plate 10 or 30, and for example, the rollover of the automobile is detected. In the intended application,
It is necessary to match the thickness direction of the piezoelectric rectangular plate 10 or 30 with the traveling direction of the vehicle. In such an application, when the structure shown in FIGS. 4 and 5 is used, the width direction is the height of the device. Therefore, there is an advantage that a low-profile piezoelectric vibrating gyroscope can be obtained.

In the above description, an example will be described in which a piezoelectric ceramic is used as the piezoelectric rectangular plate and only the region surrounded by the drive and detection partial electrodes is polarized to improve the energy confinement conditions. However, a piezoelectric single crystal may be used as the piezoelectric body, and instead of performing partial polarization,
It is also possible to improve the energy confinement conditions by a method of locally varying the thickness only in the region surrounded by the driving and detecting partial electrodes.

Further, in the embodiment of the present invention,
A rectangular plate has been described as the shape of the piezoelectric body, but this is a typical example of the structure that is easiest to make when considering manufacturing. However, if a piezoelectric body having a line-symmetrical shape is used and the excitation vibration axis is configured to match the line of symmetry, the same effect as that obtained by using the piezoelectric rectangular plate 10 can be obtained.

[0029]

As described above, according to the present invention,
It is possible to provide a piezoelectric vibrating gyroscope that is small in size, simple in structure and manufacturing, and utilizes a high-precision energy trapping vibration mode.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of a piezoelectric vibrator of a piezoelectric vibrating gyroscope according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of a gyro using the piezoelectric vibrator of FIG.

FIG. 3 is a circuit diagram illustrating an example of a current detection circuit used in the circuit of FIG. 2;

FIG. 4 is a plan view showing a structure of a piezoelectric vibrator according to a second embodiment of the present invention.

FIG. 5 is a plan view showing a structure of a piezoelectric vibrator according to a third embodiment of the present invention.

FIG. 6 is a perspective view showing a support structure of the piezoelectric vibrating gyroscope according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric vibrator 10, 30 Piezoelectric rectangular plate 11, 31, 41 First partial electrode 12, 32, 42 Second partial electrode 13, 33, 43 Third partial electrode 14, 34, 44, 45 First Extraction electrode part 15, 35, 47 Second extraction electrode part 16, 36, 46 Third extraction electrode part 18 First current detection circuit 19 Second current detection circuit 22 Differential circuit 23 Synchronous detection circuit 24 Rectifier circuit Reference Signs List 25 oscillation circuit 26 drive circuit 27 operational amplifier 30a long side 30b short side 37 support member 37a, 37b end 37c bottom 37d step 37e gap

Claims (5)

[Claims] 1. A vertical bisector of an apex angle is formed on at least one main surface of a piezoelectric rectangular plate having a polarization axis component in a thickness direction so as to be parallel to any one side of the piezoelectric rectangular plate. A piezoelectric vibrating gyroscope, wherein three partial electrodes for driving and detecting are formed at positions of respective vertices of an isosceles triangle including an arranged regular triangle. 2. The piezoelectric vibrating gyroscope according to claim 1, wherein a vertical bisector of the apex angle is located at each vertex position of an isosceles triangle including an equilateral triangle arranged in parallel with a long side of the piezoelectric rectangular plate. A piezoelectric vibrating gyroscope, wherein an external connection electrode is drawn out substantially symmetrically with respect to a center line in a longitudinal direction of a main surface of the piezoelectric rectangular plate in the vicinity of an end nearer to each of the partial electrodes. 3. The piezoelectric vibrating gyroscope according to claim 1, wherein a vertical bisector of said apex angle is located at a vertex angle of an isosceles triangle including an equilateral triangle arranged in parallel with a short side of said piezoelectric rectangular plate. The external connection electrodes were drawn out substantially symmetrically with respect to the vertical bisector, from the partial electrode toward the vicinity of both ends, and from the partial electrode at the base angle to the vicinity of the end closer to each. A piezoelectric vibrating gyroscope characterized by the above. 4. The piezoelectric vibratory gyroscope according to claim 1, wherein only the both ends in the long side direction of the piezoelectric rectangular plate are supported and fixed. 5. The piezoelectric vibrating gyroscope according to claim 1, wherein only a region including the three partial electrodes of the piezoelectric rectangular plate and being surrounded by these partial electrodes has a thickness. A piezoelectric vibrating gyroscope characterized by being polarized in a direction.