JP3640004B2 - 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 a navigation system of a vehicle or a camera body type VTR camera, and in particular, energy confinement as a vibration mode of the piezoelectric vibrator. The present invention relates to a piezoelectric vibration gyro that uses a vibration mode, has a simple structure, 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 be able to excite vibrations in two different directions orthogonal to each other, when the vibrator is rotated in a state in which one of the vibrations is excited, 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, the magnitude of the applied rotational angular velocity should be determined from the magnitude of the output voltage when the vibration amplitude on the input side is constant. Can do.
[0004]
FIG. 5 is a perspective view showing an example of the structure of a conventional piezoelectric vibration gyro. Referring to FIG. 5, piezoelectric ceramic thin plates 52 and 53 are joined 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. Yes. Accordingly, when a voltage having a frequency substantially equal to the resonance frequency of the bending vibration of the metal prism 51 is applied to the piezoelectric ceramic thin plate 52, the piezoelectric ceramic thin plate 52 bends and vibrates in the direction in which the surface where the piezoelectric ceramic 52 is joined becomes uneven (y-axis direction). . In this state, when the metal prism 51 is rotated around the axis parallel to the length direction (z-axis), the metal prism 51 is in a direction in which the surface where the piezoelectric ceramic thin plate 53 is joined becomes uneven by 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 the 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. 6A, the cross-sectional view of FIG. 6B, and the side view of FIG. Yes. This energy confinement vibration is a vibration mode in which the vibration energy is concentrated in the vicinity of the drive electrode. There are many vibration modes such as longitudinal vibration and sliding vibration in the thickness direction of the piezoelectric plate, and longitudinal vibration and sliding vibration of the piezoelectric rectangular plate. There is.
[0007]
Referring to FIGS. 6A and 6B, the energy confinement vibration has a thickness of 6 mm × 6 mm, for example, as shown in the figure because the energy of the vibration is concentrated in the vicinity of the drive electrode. As shown in FIG. 7, in a 10.7 MHz ceramic filter for FM radio, in which drive electrodes 62 and 63 and a counter electrode 64 are formed in a region having a diameter of 1.5 mm at a substantially central portion using a 0.2 mm piezoelectric plate 61. In addition, if the cavity portions 66 are formed on both sides of a region having a diameter of about 3 mm with the drive electrodes 62 and 63 and the counter electrode 64 as the center, even if the other portions are fixed with the resin 65, the vibrator characteristics are hardly affected. Don't give. 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]
In the conventional piezoelectric vibration gyro shown in FIG. 5, since the bending vibration mode of the metal prism 51 is used, 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 placed on a substrate on which a drive / detection circuit is configured, it is difficult to form a piezoelectric vibration gyro of a thin shape.
[0009]
On the other hand, if the piezoelectric vibrator shown in FIG. 6 can be used, it is considered that the problem of small size and thin size can be solved as described above.
[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 arranged at the positions of the vertices constituting the substantially isosceles triangle at the substantially central portion of one main surface of the piezoelectric plate having the 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, grounding the first electrode, and connecting the second electrode and the third electrode to each other. A voltage generated in the second and third electrodes by the action of the Coriolis force generated when a driving voltage for excitation is applied via a resistor and the front piezoelectric plate is rotated about an axis orthogonal to the main surface. A piezoelectric vibration gyro using an energy confinement vibration mode characterized in that it is configured to detect the difference between the two is obtained.
[0012]
According to the invention, in the piezoelectric vibration gyro using the energy confinement vibration, 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. A 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 piezoelectric vibrator structure 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 vertex constituting an approximately isosceles triangle at substantially the center of one main surface of the 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 including and connected to the piezoelectric vibrator 1 of FIG. Referring to FIG. 2, in the piezoelectric vibrator 1, the first electrode 11 is grounded, and an AC power source 22 is connected to the second and third electrodes 12 and 13 via resistors 20 and 21, respectively. The second and third electrodes 12 and 13 are also connected to the input terminals of the differential amplifier circuit 23, respectively.
[0016]
The output terminal of the differential amplifier circuit 23 becomes the sensor output of the piezoelectric vibration gyro via the detection circuit 24.
[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. FIGS. 3A and 3B are a plan view and a cross-sectional view showing only the electrode part, respectively, showing the basic structure of the parallel electric field excitation type thickness shear energy confinement vibrator shown in FIGS. FIG. 4 is a diagram showing a vibration displacement distribution of the piezoelectric vibrator shown in FIGS.
[0018]
Referring to FIGS. 3A and 3B, 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. This thickness shear vibration is vibration in which the direction of displacement is parallel to the plate surface and the wave propagation direction is in the thickness direction of the plate.
[0019]
Referring to FIG. 4, the piezoelectric vibrator shows a displacement distribution in the thickness direction (z-axis direction) when resonating at a half wavelength.
[0020]
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 positions, the first electrode 11 is grounded, and the second electrode 11 is grounded. The electrode 12 and the third electrode 13 are connected to an AC power source 22 via resistors 20 and 21, respectively. When an excitation driving voltage having a frequency substantially equal to the resonance frequency of the thickness-slip mode of the piezoelectric plate is applied to the second electrode 12 and the third electrode 13 from the AC power source via the resistors 20 and 21, respectively, In the region surrounded by the second, third, and third electrodes 11, 12, and 13, the sliding vibration of the energy confinement vibration mode in the direction connecting the center of the first electrode 11 and the center of the second electrode 12 and the first The sliding vibration of the energy confinement vibration mode in the direction connecting the center of the electrode 11 and the center of the third electrode 13 is generated, and these vibrations are combined to be combined with the center of the first electrode 11 and the second and third electrodes. The sliding vibration of the energy confinement vibration mode in the direction of the straight line connecting the midpoints of the straight lines connecting the centers of 12 and 13 occurs. In this state, when the piezoelectric plate 10 is rotated about an axis orthogonal to the main surface, thickness shear vibration in a direction perpendicular to the excited thickness shear vibration direction is generated by the action of Coriolis force. . Due to the thickness shear vibration generated by the Coriolis force, the impedance between the first electrode 11 and the second electrode 12 and between the first electrode 11 and the third electrode 13 changes, and as a result, the second electrode The terminal voltages of the electrode 12 and the third electrode 13 change. This change in impedance is proportional to the applied angular velocity when the excitation voltage is constant.
[0021]
Therefore, the difference between the terminal voltages of the second electrode 12 and the third electrode 13 is detected by the differential amplifier circuit 23, and this voltage is detected synchronously at a predetermined timing, so that it is proportional to the applied rotational angular velocity. Output voltage can be obtained.
[0022]
Therefore, in the embodiment of 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 can be achieved by polarizing only the vicinity of the region where the first to third electrodes 11, 12 and 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 fixation. A small piezoelectric vibration gyro that can be firmly supported and has excellent vibration resistance and shock resistance characteristics can be provided.
[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 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.
4 is a diagram showing a displacement distribution of the thickness-slip mode energy confinement vibrator of FIG. 3; FIG.
FIG. 5 is a perspective view showing an example of a conventional piezoelectric vibration gyro.
FIGS. 6A and 6B are structural views of a conventional energy confinement vibrator, where FIG. 6A is a plan view and FIG. 6B is a cross-sectional view.
7 is a side view showing a support structure of the energy confinement vibrator of FIG. 6. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piezoelectric vibrators 10 and 61 Piezoelectric plate 11 1st electrode 12 2nd electrode 13 3rd electrode 15 Partial electrode 20 and 21 Resistance 22 AC power supply 23 Differential amplifier circuit 24 Detection circuit 51 Metal prism 53 Piezoelectric ceramic thin plate 62 63 Driving electrode 64 Counter electrode 65 Resin 66 Cavity

Claims (2)

First, second, and third electrodes are formed at the positions of vertices constituting a substantially isosceles triangle at a substantially central portion of one main surface of a piezoelectric plate having a polarization axis in the thickness direction, and the first electrode Are arranged at the apex angle, the second and third electrodes are arranged at the base angle, the first electrode is grounded, and the second and third electrodes are excited via resistors, respectively. And detecting a difference in voltage generated in the second and third electrodes by the action of Coriolis force generated when the piezoelectric plate is rotated about an axis orthogonal to the principal surface. A piezoelectric vibration gyro using an energy confinement vibration mode characterized in that it is configured as follows. 2. The piezoelectric vibration gyro using the energy confinement vibration mode according to claim 1, wherein a piezoelectric ceramic is used as the piezoelectric plate, and only the vicinity of the region where the first to third electrodes are formed extends in the thickness direction of the piezoelectric ceramic. Piezoelectric vibration gyro using energy confinement vibration mode characterized by polarization.

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