JP3685224B2 - 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 more particularly to energy confinement as a vibration mode of the piezoelectric vibrator. The present invention relates to a piezoelectric vibration gyro that uses vibration mode, has a simple structure and is easily supported, 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 and rotational angular velocity of the input side, it is possible to obtain the magnitude of the applied rotational angular velocity from the magnitude of the output voltage when the input side vibration amplitude is constant. it can.
[0004]
FIG. 4 is a perspective view showing the structure of a conventional piezoelectric vibration gyro. As shown in FIG. 4, the piezoelectric vibration gyro 100 has a rectangular column vibrator formed by bonding piezoelectric ceramic thin plates 102 and 103 to substantially the center of adjacent surfaces of a metal prism 101 having a square cross-sectional shape. Each of these piezoelectric ceramic thin plates 102 and 103 has electrodes formed on both surfaces thereof and is polarized in the thickness direction, and lead terminals 104 and 105 for lead-out are formed on one surface.
[0005]
It is known that the metal prism 101 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. . Therefore, when a voltage having a frequency substantially equal to the resonance frequency of the bending vibration of the metal prism 101 is applied to the piezoelectric ceramic thin plate 102, the piezoelectric ceramic thin plate 102 bends and vibrates in a direction (y-axis direction) where the surface where the piezoelectric ceramic thin plate 102 is joined becomes uneven. In this state, when the metal prism 101 is rotated around an axis (z axis) parallel to the length direction, the metal prism 101 is in a direction in which the surface where the piezoelectric ceramic thin plate 103 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 103 due to the piezoelectric effect. The magnitude of this voltage is proportional to the magnitude of vibration excited by the piezoelectric ceramic thin plate 102 and the magnitude of the applied rotational angular velocity (Ω).
[0006]
Therefore, if the magnitude of the excitation voltage applied to the piezoelectric ceramic thin plate 102 is constant, the voltage generated in the piezoelectric ceramic thin plate 103 becomes a voltage proportional to the rotational angular velocity (Ω) of the metal prism 101.
[0007]
Further, as a piezoelectric vibrator widely used in an intermediate frequency filter of FM radio or television, a piezoelectric vibration that performs energy confinement vibration as shown in the plan view of FIG. 5A and the cross-sectional view of FIG. The child is known. Here, the energy confinement vibration is a vibration mode in which vibration energy is concentrated in the vicinity of the drive electrode, and the longitudinal vibration and slip vibration in the thickness direction of the piezoelectric plate 10 and the longitudinal vibration and slip in the width direction of the piezoelectric rectangular plate. There are many vibration modes such as vibration. FIG. 6 is a side view of a filter using the piezoelectric vibrator shown in FIGS. 5 (a) and 5 (b).
[0008]
Referring to FIGS. 5 (a) and 5 (b), the energy confinement vibration is such that the vibration energy is concentrated in the vicinity of the drive electrode. For example, in FIG. 5, a 6 mm × 6 mm piezoelectric film having a thickness of 0.2 mm is used. In the case where the 10.7 MHz ceramic filter for FM radio in which the drive electrodes 51, 52, and 53 are formed in a region having a diameter of 1.5 mm in the substantially central portion using the plate 10, as shown in FIG. If the cavity portions 54 are formed on both surfaces of a region having a diameter of about 3 mm with the drive electrodes 51, 52 and 53 as the center, even if the other portions are fixed by the resin layer 55, 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.
[0009]
[Problems to be solved by the invention]
Since the above-described conventional piezoelectric vibration gyro uses the bending vibration mode of a metal prism, the support and fixing of the prism oscillator must be performed 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 prismatic vibrator supported by a holder is mounted on a substrate on which a drive and detection circuit is configured, it is difficult to construct a small and thin piezoelectric vibration gyro.
[0010]
Therefore, if the ceramic filter piezoelectric vibrator shown in FIGS. 5A and 5B can be applied to a piezoelectric vibratory gyro, the disadvantage of the gyroscope using the prismatic vibrator of FIG. 4 can be solved. Conceivable.
[0011]
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 the detection circuit can be configured on the same substrate on which the piezoelectric vibration gyro is formed.
[0012]
[Means for Solving the Problems]
According to the present invention, the first electrode pair opposed to the substantially central portion of one surface of the piezoelectric plate having the polarization axis in the thickness direction at a predetermined interval, and the first electrode pair are rotated by approximately 90 degrees. A second electrode pair that is opposed to the first electrode pair, and is opposed to the region on the other surface of the piezoelectric plate where the first and second electrode pairs are formed. in direction approximately 45 degrees to form a third pair of electrodes facing each other, said during the third electrode pair and applying a voltage for excitation, the piezoelectric plate an axis substantially perpendicular to the one surface A piezoelectric vibration gyro using an energy confinement vibration mode is obtained, which is configured to detect a voltage of a difference between output voltages generated between the first and second electrode pairs when rotated around. It is done.
[0013]
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 electrode pairs are formed is measured in the thickness direction. A piezoelectric vibration gyro using an energy confinement vibration mode characterized by polarization is obtained.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0015]
FIG. 1 is a perspective view showing a structure of a piezoelectric vibration gyro 1 (hereinafter simply referred to as a piezoelectric vibration gyro 1) using an energy confinement mode according to an embodiment of the present invention. As shown in FIG. 1, a first electrode pair 11a, 11b opposed to a substantially central portion of one main surface of a piezoelectric plate 10 having a polarization axis in the thickness direction at a predetermined interval, A second electrode pair 12a, 12b is formed opposite to a position obtained by rotating the electrode pair 11a, 11b by 90 degrees, and the first and second electrode pairs 11a, 11b on the other surface of the piezoelectric plate 10 and The third electrode pair 13a, 13b facing the direction opposite to the first electrode pair 11a, 11b and the direction of 45 degrees as shown by the broken line in the figure at a position facing the region where 12a, 12b is formed. Is formed.
[0016]
Here, as will be described in detail later, when an excitation AC voltage having a frequency substantially equal to the resonance frequency of the thickness-slip mode of the piezoelectric plate 10 is applied between the third electrode pairs 13a and 13b, as described in detail later, In the region where the three electrode pairs 13a and 13b are opposed, the sliding vibration of the energy confinement vibration mode in the direction in which these electrode pairs are opposed to each other 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 direction of the excited thickness shear vibration mode is generated by the action of the Coriolis force. Due to the thickness-shear vibration generated by this Coriolis force, a voltage is generated between the first electrode pair 11a and 11b and between the second electrode pair 12a and 12b, but is generated at the first electrode pair 11a and 11b. Since the voltage and the voltage generated in the second electrode pair 12a and 12b are shifted in direction by ± 45 degrees with respect to the direction of the thickness shear vibration in which each electrode pair is excited, the amplitudes are equal. , The voltages are 180 degrees out of phase with each other.
[0017]
Therefore, by detecting the voltage difference between the voltages generated between these electrode pairs and synchronously detecting this voltage at a predetermined timing, an output voltage proportional to the applied rotational angular velocity can be obtained.
[0018]
Here, 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. In this case, this object can be achieved by polarizing only the vicinity of the region where the first to third electrode pairs are formed in the thickness direction.
[0019]
Furthermore, the operation principle of the piezoelectric vibrator of the piezoelectric gyro using the energy confinement mode used in the embodiment of the present invention will be described in detail with reference to FIGS.
[0020]
2A and 2B are a plan view and a cross-sectional view of a piezoelectric vibrator having a structure obtained by further simplifying the piezoelectric vibrator of the piezoelectric vibration gyro shown in FIG. This is called an excitation-type thickness-slip energy confinement oscillator. FIG. 3 is a diagram showing the displacement in the thickness direction of the piezoelectric vibrator shown in FIGS. 2 (a) and 2 (b). Referring to FIGS. 2A and 2B, partial electrodes 14a and 14b are disposed on the same surface of the central portion of the piezoelectric plate 10 polarized in the thickness direction (z-axis) so as to face each other in the x-axis direction. Is formed. Since an electric field in a direction substantially parallel to one surface of the piezoelectric plate 10 is applied to the portion sandwiched between the partial electrodes 14a and 14b, the partial electric field is caused by the interaction with the polarization in the thickness direction perpendicular to the electric field. When the dimensions of the electrodes 14a and 14b 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 portion. Further, since the drive and detection circuit of the piezoelectric vibration gyro can be configured on the same substrate on which the vibrator is formed, a small and thin piezoelectric vibration gyro can be obtained.
[0021]
FIG. 3 shows the displacement distribution in the thickness direction when the piezoelectric vibrators of FIGS. 2A and 2B are resonating at half wavelength. The x-axis, y-axis, and z-axis are shown in FIG. ) Corresponding to the x-axis, y-axis, and z-axis directions. The above-mentioned thickness shear vibration is vibration in which the displacement is parallel to the plate surface and the wave propagation direction is in the thickness direction of the plate.
[0022]
【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 structure of a piezoelectric vibration gyro using an energy confinement mode according to an embodiment of the present invention.
FIGS. 2A and 2B are diagrams for explaining the operation principle of a parallel electric field excitation type thickness-slip mode energy confinement vibrator used in the piezoelectric vibration gyro of FIG. 1; FIG. 2A is a plan view, and FIG. is there.
FIG. 3 is a displacement distribution of the thickness-slip mode energy confinement vibrator of FIG. 2;
FIG. 4 is a perspective view for explaining a conventional piezoelectric vibration gyro.
FIGS. 5A and 5B are diagrams showing an example of a conventional energy confinement vibrator, where FIG. 5A is a plan view and FIG. 5B is a cross-sectional view.
6 is a support structure diagram of the energy confinement vibrator of FIG. 5; FIG.
[Explanation of symbols]
1,100 Piezoelectric vibrating gyroscope 10 Piezoelectric plates 11a, 11b First electrode pair 12a, 12b Second electrode pair 13a, 13b Third electrode pair 14a, 14b Partial electrodes 51, 52, 53 Drive electrode 55 Resin layer 101 Metal Square pillars 102, 103 Piezoelectric ceramic thin plates 104, 105 Lead terminals

Claims (2)

A first electrode pair opposed to a substantially central portion of one surface of the piezoelectric plate having a polarization axis in the thickness direction with a predetermined interval, and a first electrode pair opposed to a position obtained by rotating the first electrode pair by approximately 90 degrees. 2 at a position facing the region where the first and second electrode pairs are formed on the other surface of the piezoelectric plate, approximately 45 degrees from the facing direction of the first electrode pair. in the direction to form a third pair of electrodes facing each other, when the voltage for excitation is applied between the third electrode pair, and rotates the piezoelectric plate about an axis substantially perpendicular to the one surface A piezoelectric vibration gyro using an energy confinement vibration mode configured to detect a voltage difference between output voltages generated between the first and second electrode pairs.   2. The piezoelectric vibration gyro using the energy confinement vibration mode according to claim 1, wherein piezoelectric ceramics are used as the piezoelectric plate, and only the vicinity of the region where the first to third electrode pairs are formed is polarized in the thickness direction. Piezoelectric vibration gyro using energy confinement vibration mode characterized by

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