JPH10260046A - Piezoelectric vibration gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric vibration gyro which is small, simple and easy to be manufactured and uses accurate energy-containment vibration mode. SOLUTION: The piezoelectric vibration gyro has first, second, third electrodes 11, 12, 13 for driving or detection on almost center part of at least one main side of its piezoelectric plate 10 which has polarization axis component in the thickness direction, and uses parallel electric field excitation type of energy-containment thickness slide vibration. Only vibration region 2 which contains first, second, third electrodes 11, 12, 13 and generates energy- containment vibration is polarized into almost circle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibratory gyroscope utilizing ultrasonic vibration of a piezoelectric vibrator, among gyroscopes used for a camera navigation system or a camera-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. Is rotated, the Corioliser which is generated in the direction perpendicular to the excitation direction and the rotation axis is detected, and the rotational angular velocity is detected. The piezoelectric vibrating gyroscope has various applications, but has recently been used in, for example, an automobile navigation system or 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).

In a piezoelectric vibrating gyroscope using the energy trapping vibration mode, since the vibration energy is concentrated on a local portion of the piezoelectric vibrator, the support of the piezoelectric vibrator is easy and easy, and it is not necessary to use a separated lead wire. There is an advantage that it becomes.

In prior art 1, in order to confine vibration energy in a local area, the thickness of the vibrator is locally increased, the area is polarized in the thickness direction, and a driving electrode is provided on the opposite end face of the thick local area. It discloses that a detection electrode is provided on the side surface. Further, as another example, there is also disclosed an arrangement in which a drive electrode and a detection electrode are provided on one surface of a piezoelectric plate, and interdigital electrodes are provided between the drive electrodes as detection electrodes.

[0006]

In the piezoelectric vibrating gyroscope using the energy trapping vibration mode disclosed in the prior art 1, the thickness of the piezoelectric plate must be locally increased or interdigital electrodes must be formed. Manufacturing difficulties.

Further, since the pair of driving electrodes and the pair of detecting electrodes are provided near each other, the driving electric field applied from the driving electrodes to the piezoelectric plate is affected by the detecting electrodes, and the direction of the driving electric field changes, so that the accuracy is reduced. Is not obtained.

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

[0009]

According to the present invention, a parallel electric field comprising a plurality of electrodes for driving or detecting is formed on at least one principal surface of a piezoelectric plate having a polarization axis component in a thickness direction. In a vibration gyro utilizing the excitation type energy confinement thickness shear vibration, a vibration gyro in which only the vibration region including the electrode where the energy confinement vibration occurs is polarized in a substantially circular shape can be obtained. Here, in the present invention,
The term “substantially circular” includes not only a true circle, but also a shape obtained by cutting a part of a circle along a diameter direction, an ellipse, and a track shape.

[0010]

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

FIGS. 1A and 1B are diagrams showing a configuration of a piezoelectric vibrator of an energy trap type piezoelectric vibrating gyroscope according to a first embodiment of the present invention, wherein FIG. 1A is a plan view and FIG. . As shown in FIGS. 1A and 1B, the piezoelectric vibrator 1 is made of, for example, a piezoelectric ceramic plate such as PZT or barium titanate, and has a central portion having a polarization axis component in a thickness direction. 10 is used. This piezoelectric plate 10
On the main surface of the central portion, three first to third electrodes having strip-like electrodes of the same size are positioned at respective vertices of an equilateral triangle so as to be line-symmetric with respect to a vertical bisector. 3 electrodes 11,
12 and 13 are formed. These first, second, and third electrodes 11, 12, and 13 are provided with first, second, and third terminal portions 14, 15, and 16 for leading out to the outside.
Each is connected. In FIG. 1, the electrodes and the terminals are collectively indicated by thin oblique lines. At this time, the piezoelectric plate 1
In FIG. 1, only a circular region surrounded by three first, second, and third electrodes 11, 12, and 13 is polarized in the thickness direction of the piezoelectric plate 10 as indicated by a broken line 2 in FIG. . Thus, the first, second, and third electrodes 11, 12, 1
When only the circular region surrounded by 3 is polarized, the piezoelectric characteristics of the polarized region and the non-polarized region change, so that the state of energy confinement is improved.

Further, when a vibrating gyroscope is constructed, it is required that the vibration characteristics in two directions orthogonal to each other in the plane of the piezoelectric plate 10 are equalized. , The symmetry in all directions is ensured, and the characteristics of the vibrating gyroscope can be improved. The first to third electrodes 11 to 13 and the first to third terminal portions 14 to 16 are preferably made of silver paste or gold sputtering. Of course, other conductive films can be employed. Further, the first to third terminal portions 14 to 16 for leading out to the outside may not be provided on the piezoelectric vibrator 1 but may be lead wires.

The operation of the piezoelectric vibrator 1 of the piezoelectric vibrating gyroscope shown in FIG. 1 is as follows. As shown in FIG. 1, three-dimensional coordinates are defined in which the thickness direction is the Z axis, the front direction of the first electrode 11 is the X axis, and the direction orthogonal to these is the Y axis. Here, the first electrode 11 and the second and third electrodes 12 and 13
When a driving voltage (alternating current) is applied between the two, vibration in the X direction is excited. When the piezoelectric plate 10 rotates around the Z axis in this state, a vibration due to Coriolis force occurs in the Y direction,
As a result, an electromotive force is generated between the second and third electrodes 12 and 13. By detecting the electromotive force, 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 center of the piezoelectric plate 10 and does not reach the periphery, it is easy to support the peripheral portion of the piezoelectric 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 electrodes 12 and 13 of the piezoelectric vibrator 1 are provided with current detection circuits 18 and 19 (hereinafter, for convenience of explanation, the first and second electrodes, respectively).
And a second current detection circuit) are connected to each other. A differential amplifier circuit 22 is connected to the output sides of the first and second current detection circuits, and a piezoelectric vibration gyro sensor is connected via a synchronous detection circuit (simply synchronous detection in the figure) 23 and a rectifier circuit 24. Output. On the other hand, the first and second current detection circuits are provided with an oscillation circuit 2 for satisfying the self-excited oscillation condition.
5 and are connected to the first electrode 11 via the X vibration drive circuit 26 to form a self-excited oscillation circuit. With this 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 becomes
Is applied to the electrodes 11.

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 R is connected from the output terminal of the operational amplifier 27 to the inverting input terminal. It is always kept at the reference potential. When a current flows into this inverting terminal, it is converted into a voltage by a resistor. Therefore, the current detection circuits 18 and 19 shown in FIG. 3 are functionally circuits having almost zero input impedance and capable of obtaining an output voltage proportional to the input current.

Next, the driving principle of the piezoelectric vibrator according to the first embodiment of the present invention will be described more specifically with reference to the drawings.

FIGS. 4A and 4B are views showing the basic structure of the piezoelectric vibrator 1 'of the parallel electric field excitation type thickness-shear energy trapping type piezoelectric vibrating gyroscope shown in FIG.
(A) is a plan view and (b) is a side view showing only an electrode portion excluding a terminal portion. Referring to FIGS. 4A and 4B, the piezoelectric vibrator 1 'is spaced apart in the X-axis direction on the same plane at the center of the piezoelectric plate 10 polarized in the thickness direction (Z-axis direction). Opposing strip electrodes D1 and D2
Are formed. Symbols T1 and T2 indicate terminal portions connected to the electrodes D1 and D2, respectively. When a voltage is applied between the terminal portions T1 and T2, the opposite electrode D
1 and D2, an electric field is applied in a direction (X-axis direction) substantially parallel to the surface of the piezoelectric plate 10 in a region (inter-electrode region) of the piezoelectric plate 10; Axial direction)
Interaction with polarization causes strain in the X direction in the X direction. Here, if the dimensions of the electrodes D1 and D2 are appropriately designed in accordance with the characteristics of the piezoelectric plate 10,
Thickness shear vibration can be excited in this portion. The vibration is attenuated around the inter-electrode region and confined without propagating. That is, the energy trap type piezoelectric vibrator 1 ′ can be configured. This vibration is a thickness shear vibration caused by an electric field parallel to the surface of the piezoelectric plate 10, and is therefore called a parallel electric field excitation type thickness shear vibration. The thickness shear vibration is a vibration in which the direction of displacement is parallel to the plate surface and the direction of wave propagation is in the thickness direction of the plate. In order to illustrate the state of this vibration, FIG. 5 shows a displacement distribution in the thickness direction (Z-axis direction) when resonance occurs at a half wavelength.

The piezoelectric vibrator 1 shown in FIG. 1 utilizes the basic structure shown in FIGS. That is, the first electrode 11 is a D1 electrode, and the second electrode 12 and the third electrode 13 are D2 electrodes. The D2 electrode is divided into two to form a detection electrode, constitutes a second 12 electrode and a third electrode 13, and is connected to current detection circuits 18 and 19 each having a virtual ground function. Thus, the second electrode 12 and the third electrode 13 are virtually maintained at the reference potential, and thus can be regarded as a ground terminal in terms of potential. Therefore, when a drive voltage for excitation having a frequency substantially equal to the resonance frequency of the thickness-shear vibration mode of the piezoelectric plate is applied to the first electrode 11 of FIG. , And the third electrodes 11, 12,
In the circular region including and surrounded by these, the thickness shear vibration of the first electrode 11 in the energy confinement vibration mode in the direction of the arrow (X direction) is generated.

In this state, when the piezoelectric plate 10 is rotated around an axis perpendicular to the main surface, the action of the Coriolis force causes the thickness shear vibration in a direction perpendicular to the direction of the excited thickness shear vibration. Occurs. The thickness-shear vibration generated by the Coriolisa causes the first electrode 11 and the third electrode 1 to move between the first electrode 11 and the second electrode 12 and between the first electrode 11 and the third electrode 1.
3 changes, and as a result, the first
And the current value flowing into the second current detection circuits 18 and 19 changes. Since the second electrode 12 and the third electrode 13 are arranged symmetrically with respect to the direction of the excited thickness shear vibration, the currents changed by the Coriolis force have the same amplitude and a phase difference of 180 degrees from each other. Current. Accordingly, the output voltages of the first and second current detection circuits (current detection circuits 18 and 19) also have the same amplitude, and have voltages 180 degrees out of phase with each other. By performing synchronous detection of the voltage at a predetermined timing, an output voltage proportional to the applied rotational angular velocity can be obtained.

On the other hand, the first and second current detection circuits are provided with an oscillation circuit 25 and a drive circuit 26 for satisfying the self-excited oscillation condition.
To the electrode 11 to form a self-excited oscillation loop. Thus, the vibrator can be efficiently driven by automatically tracking the resonance frequency of the vibrator, so that a gyro with high sensitivity can be obtained.

As shown in FIG. 6, the displacement distribution of the energy-confined thickness shear vibration is symmetric with respect to the X direction, and is symmetric with respect to the Y direction when rotated about the Z axis. Therefore, by making the polarization region circular, the symmetry is improved, and the influence of the reflected wave or the like on the vibration gyro characteristic is canceled.

Although the above description has been made with respect to the three-electrode configuration, the electrode configuration of the piezoelectric vibrator is shown in FIG. 7 as a second embodiment of the present invention in which four electrodes E, F, G, and H are used. 3 shows an example of the electrode configuration. Referring to FIG.
The electrode configuration of the four electrodes 31 to 34 of E, F, G, and H is symmetrical with respect to one straight line in the plane of the piezoelectric plate 10, for example, the facing direction of the E electrode 31 and the G electrode 33, or F electrode 3
The same effect as the piezoelectric vibrator 1 shown in FIG. 1 can be obtained by configuring the piezoelectric vibrator 1 symmetrically with respect to the direction in which the piezoelectric vibrator 2 and the H electrode 34 face each other and exciting the excitation vibration along this straight line.

[0024]

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. 1A is a plan view and FIG. 1B is a cross-sectional view illustrating a configuration of a piezoelectric vibrator 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;

4A and 4B are diagrams showing a basic structure of a vibrator employed in the piezoelectric vibrator of FIG. 1, wherein FIG. 4A is a plan view and FIG. 4B is a side view.

FIG. 5 is a diagram showing a displacement distribution in a thickness direction in thickness shear vibration of the oscillator having the basic structure of FIG. 4;

FIG. 6 is a diagram showing a displacement distribution of thickness shear vibration.

FIG. 7 is a perspective view illustrating a configuration example of an electrode of a piezoelectric vibrator according to a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Piezoelectric vibrator 10 Piezoelectric plate 11 1st electrode 12 2nd electrode 13 3rd electrode 14 1st terminal part 15 2nd terminal part 16 3rd terminal part 18 and 19 Current detection circuit (1st and 2nd) 2nd current detection circuit) 22 differential circuit 23 synchronous detection circuit 24 rectifier circuit 25 oscillation circuit 26 drive circuit 27 operational amplifier 30 piezoelectric vibrator 31, 32, 33, 34 E, F, G, and H electrodes

Claims (1)

[Claims] 1. A parallel electric field excitation type energy confinement thickness shear vibration comprising a plurality of driving or detecting electrodes formed on at least one principal surface of a piezoelectric plate having a polarization axis component in a thickness direction. In a vibrating gyro,
A vibrating gyroscope wherein only a vibrating region including the plurality of electrodes and in which an energy trapping vibration occurs is polarized in a substantially circular shape.