JP3640003B2 - Piezoelectric vibration gyro using energy confinement vibration mode - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vibration gyro using ultrasonic vibration of a piezoelectric vibrator among gyroscopes used for camera shake correction of an automobile navigation system or a camera-integrated VTR camera, and in particular, energy as a vibration mode of the piezoelectric vibrator. The present invention relates to a piezoelectric vibration gyro that uses a confined vibration mode, has a simple structure and is easy to support, and has excellent vibration resistance and shock resistance.
[0002]
[Prior art]
A piezoelectric vibratory gyroscope is a gyroscope that uses a mechanical phenomenon that when a rotational angular velocity is applied to a vibrating object, a Coriolis force is generated in a direction perpendicular to the vibration direction.
[0003]
In general, in a composite vibration system configured to excite vibrations in two different directions orthogonal to each other, when one of the vibrations is excited and the vibrator is rotated, the direction perpendicular to this vibration is caused by the action of the Coriolis force described above. A force acts on the other, and the other vibration is excited. Since the magnitude of this vibration is proportional to the amplitude of the vibration on the input side and the rotational angular velocity, if the vibration amplitude on the input side is constant, the magnitude of the applied rotational angular velocity can be obtained from the magnitude of the output voltage. it can.
[0004]
FIG. 6 is a perspective view showing the structure of a conventional piezoelectric vibration gyro. Referring to FIG. 6, piezoelectric ceramic thin plates 52 and 53 are bonded to substantially the center of adjacent surfaces of a metal prism 51 having a square cross-sectional shape. Each of these piezoelectric ceramic thin plates 52 and 53 has electrodes formed on both surfaces and is polarized in the thickness direction.
[0005]
It is known that the metal prism 51 having a square cross section has two bending vibration modes orthogonal to each other, and the resonance frequencies of the two bending vibration modes are substantially equal when the material characteristics are uniform. . Accordingly, when a voltage having a frequency substantially equal to the resonance frequency of the bending vibration of the metal prism is applied to the piezoelectric ceramic thin plate 52, the piezoelectric ceramic 52 is bent and vibrated in a direction (y-axis direction) where the surface on which the piezoelectric ceramic 52 is bonded becomes uneven. In this state, when the metal prism 51 is rotated around an axis parallel to the length direction (z axis), the metal prism 51 has a direction in which the surface where the piezoelectric ceramic thin plate 53 is joined becomes uneven due to the action of the Coriolis force. Bending vibration is also generated (in the x-axis direction), and a voltage is generated in the piezoelectric ceramic thin plate 53 by the piezoelectric effect. The magnitude of this voltage is proportional to the magnitude of vibration excited by the piezoelectric ceramic thin plate 52 and the magnitude of the applied rotational angular velocity. Therefore, if the magnitude of the excitation voltage applied to the piezoelectric ceramic thin plate 52 is constant, the voltage generated in the piezoelectric ceramic thin plate 53 is a voltage proportional to the rotational angular velocity of the metal prism 51.
[0006]
On the other hand, an energy confinement vibration type filter as shown in the plan view of FIG. 7A, the cross-sectional view of FIG. 7B, and the side view of FIG. Yes. This energy confinement vibration is a vibration mode in which the energy of the vibration is concentrated near the drive electrode. There are many such as longitudinal vibration and sliding vibration in the thickness direction of the piezoelectric plate, and longitudinal vibration and sliding vibration in the width direction of the piezoelectric rectangular plate. There are vibration modes.
[0007]
Referring to FIGS. 7A and 7B, since the energy of the energy confinement vibration is concentrated in the vicinity of the drive electrode, for example, as shown in FIG. In the 10.7 MHz ceramic filter for FM radio in which the drive electrodes 62, 63, and 64 are formed in a region having a diameter of 1.5 mm in the substantially central portion using a 2 mm piezoelectric plate 61, as shown in FIG. If the hollow portions 66 are formed on both surfaces having a diameter of about 3 mm centering on 62, 63 and 64, even if the other portions are fixed with the resin 65, the vibrator characteristics are hardly affected. That is, it is possible to obtain a piezoelectric vibrator or a filter using the piezoelectric vibrator that is free to form lead terminals and is not affected by the support.
[0008]
[Problems to be solved by the invention]
Since the conventional piezoelectric vibration gyro shown in FIG. 6 uses a bending vibration mode of a metal prism, the vibrator must be supported and fixed at the position of the vibration node. In addition, in the conventional piezoelectric vibration gyro, it is necessary to connect the drive / detection circuit and the electrodes of the vibrator with lead wires, and it is difficult to suppress variations in characteristics due to variations in the connection state. Furthermore, since a vibrator supported by a holder is assembled on a substrate on which a drive / detection circuit is configured, it is difficult to construct a small and thin piezoelectric vibration gyro.
[0009]
On the other hand, if the piezoelectric vibrator shown in FIG. 7 can be used, it is considered that the problem of being small and thin as described above can be solved.
[0010]
Therefore, the technical problem of the present invention is that the conventional piezoelectric vibration gyro described above is eliminated, the structure is simple, and the input / output terminals can be connected without using lead wires. An object of the present invention is to provide a small and thin piezoelectric vibration gyro in which a detection circuit is configured on a substrate having a vibration gyro.
[0011]
[Means for Solving the Problems]
According to the present invention, the first, second, and third electrodes are provided at the positions of the vertices constituting approximately an isosceles triangle at approximately the center of one main surface of the piezoelectric plate having a polarization axis in the thickness direction. Forming the first electrode at the apex angle position, the second and third electrodes at the base angle position, and the second and third electrodes having the first and second virtual ground functions, respectively. When connected to a second current detection circuit, an excitation drive voltage is applied to the first electrode, and the piezoelectric plate is rotated about an axis orthogonal to the main surface, the first and second electrodes A piezoelectric vibration gyro using an energy confinement vibration mode characterized in that a difference generated between the outputs of the current detection circuit is detected.
[0012]
According to the present invention, in the piezoelectric vibration gyro using the energy confinement vibration mode, piezoelectric ceramic is used as the piezoelectric plate, and only the vicinity of the region where the first to third electrodes are formed is arranged in the thickness direction. The piezoelectric vibration gyro using the energy confinement vibration mode according to claim 1 is obtained.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0014]
FIG. 1 is a perspective view showing a structure of a piezoelectric vibrator of an energy confinement piezoelectric vibration gyro according to an embodiment of the present invention. As shown in FIG. 1, the piezoelectric vibrator 1 has a first electrode at the position of each apex that constitutes an isosceles triangle at substantially the center of one principal surface of a piezoelectric plate 10 having a polarization axis in the thickness direction. 11, a second electrode 12, and a third electrode 13 are formed.
[0015]
FIG. 2 is a block diagram showing a circuit configuration connected to the piezoelectric vibrator 1 of FIG. Referring to FIG. 2, in the piezoelectric vibrator 1, an AC power supply 21 is connected to the first electrode 11, and current detection circuits 18 and 19 are connected to the second and third electrodes 12 and 13, respectively. Yes. A differential amplifier circuit 22 is connected to the output side of the current detection circuits 18 and 19 and becomes a sensor output of the piezoelectric vibration gyro via the detection circuit 23.
[0016]
FIG. 3 is a diagram illustrating a configuration example of a current detection circuit having a virtual ground function used in the piezoelectric vibration gyro using the energy confinement vibration mode of FIG. The current detection circuits 18 and 19 shown in FIG. 3 are circuits that have an input impedance substantially zero and can obtain an output voltage proportional to the input current.
[0017]
Next, the driving principle of the piezoelectric vibrator according to the embodiment of the present invention will be described more specifically with reference to the drawings.
[0018]
FIGS. 4A and 4B are a plan view and a cross-sectional view showing only the electrode portion, respectively, showing the basic structure of the parallel electric field excitation type thickness-slip energy confinement oscillator shown in FIGS. 4A and 4B, partial electrodes 14 and 15 facing in the x-axis direction are formed on the same surface of the central portion of the piezoelectric plate 10 polarized in the thickness direction (z-axis direction). Has been. Since an electric field in a direction substantially parallel to the plane of the plate (x-axis direction) is applied to the portion sandwiched between the partial electrodes 14 and 15, due to the interaction with the polarization in the thickness direction perpendicular to the electric field. If the dimensions of the partial electrodes 14 and 15 are appropriately designed in accordance with the characteristics of the piezoelectric material to be used, a parallel electric field excitation type thickness shear energy confinement vibrator can be formed in this part. The thickness shear vibration is vibration in which the displacement direction is parallel to the plate surface and the wave propagation direction is in the thickness direction of the plate. As shown in FIG. 5, when resonating at half wavelength, a displacement distribution in the thickness direction (z) is shown.
[0019]
Returning to FIG. 1, the first electrode 11 is arranged at the apex angle position, the second electrode 12 and the third electrode 13 are arranged at the base angle position, and the second electrode 12 and the third electrode 13 are arranged. Are connected to current detection circuits 18 and 19 each having a virtual ground function. Since the second electrode 12 and the third electrode 13 are connected to the virtual ground circuit, they can be regarded as ground terminals in terms of potential.
[0020]
Therefore, when a driving voltage for excitation having a frequency substantially equal to the resonance frequency of the thickness-shear mode of the piezoelectric plate 10 is applied to the first electrode 11, the first electrode 11 is surrounded by the first, second, and third electrodes 11, 12, and 13. In this region, the sliding vibration of the energy confinement vibration mode in the direction of the straight line connecting the center of the straight line connecting the center of the first electrode 11 and the center of the second and third electrodes 12 and 13 occurs. In this state, when the piezoelectric plate 10 is rotated around an axis orthogonal to the main surface, thickness shear vibration in a direction perpendicular to the direction of excited thickness shear vibration is generated by the action of the Coriolis force. The thickness shear vibration generated by the Coriolis force changes the impedance between the first electrode 11 and the second electrode 12 and between the first electrode 11 and the third electrode 13, and as a result, the current detection circuit 18. And the value of the current flowing into 19 changes. As described above, since the second electrode 12 and the second electrode 13 are arranged symmetrically with respect to the direction of the excited thickness shear vibration, the currents that change due to the Coriolis force have the same amplitude, The voltages are 180 degrees out of phase with each other.
[0021]
Accordingly, the output voltages of the current detection circuits 18 and 19 have the same amplitude and are 180 degrees out of phase with each other. The voltage difference between these output voltages is detected, and this voltage is synchronously detected at a predetermined timing. Thus, an output voltage proportional to the applied rotational angular velocity can be obtained.
[0022]
Therefore, in the present invention, an important point is to excite clean energy confinement vibration without unnecessary vibration in a region where each electrode pair is opposed, particularly when piezoelectric ceramic is used as the piezoelectric plate 10. This object can be achieved by polarizing only the vicinity of the region where the first to third electrodes 11, 12, 13 are formed in the thickness direction.
[0023]
【The invention's effect】
As described above, according to the present invention, the structure is simple, the input / output terminals can be connected without using lead wires, and there is almost no influence on the gyro characteristics due to support and fixing. A small piezoelectric vibration gyro that can be firmly supported and has excellent vibration resistance and shock resistance is obtained.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a piezoelectric vibrator of an energy confining vibration gyro according to an embodiment of the present invention.
2 is a block diagram showing a circuit configuration connected to the piezoelectric vibrator of FIG. 1;
3 is a circuit diagram showing an example of a current detection circuit having a virtual ground function used in the energy confinement type vibration gyro shown in FIG. 2;
4 is a diagram showing a basic configuration for explaining a driving principle of a parallel electric field excitation type thickness-slip mode energy confinement vibrator used in the piezoelectric vibration gyro shown in FIGS. 1 and 2. FIG.
5 is a diagram showing a displacement distribution of the thickness-slip mode energy confinement oscillator of FIG. 4; FIG.
FIG. 6 is a perspective view showing an example of a conventional piezoelectric vibration gyro.
7A and 7B are structural views of a conventional energy confinement vibrator, where FIG. 7A is a plan view and FIG.
8 is a side view showing a support structure of the energy confinement vibrator of FIG. 7;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piezoelectric vibrators 10 and 61 Piezoelectric plate 11 1st electrode 12 2nd electrode 13 3rd electrode 14 and 15 Partial electrodes 18 and 19 Current detection circuit 21 AC power supply 22 Differential amplification circuit 23 Detection circuit 51 Metal prism 52 , 53 Piezoelectric ceramic thin plates 54, 55 Lead terminals 62, 63, 64 Drive electrode 65 Resin 66 Cavity

Claims (2)

A first electrode, a second electrode, and a third electrode are formed at positions of apexes forming approximately an isosceles triangle at a substantially central portion of one main surface of the piezoelectric plate having a polarization axis in the thickness direction, and the first electrode is formed. The first and second current detection circuits each having a first ground electrode, the second and third electrodes disposed at a bottom angle, and the second and third electrodes having a virtual ground function, respectively. Connected to the first electrode, an excitation drive voltage is applied to the first electrode, and when the piezoelectric plate is rotated about an axis orthogonal to the main surface, the output between the first and second current detection circuits is A piezoelectric vibration gyro using an energy confinement vibration mode characterized by detecting a difference that occurs. 2. The piezoelectric vibration gyro using the energy confinement vibration mode according to claim 1, wherein piezoelectric ceramic is used as the piezoelectric plate, and only the vicinity of the region where the first to third electrodes are formed is polarized in the thickness direction. Piezoelectric vibration gyro using the energy confinement vibration mode.

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