JP3690448B2 - Piezoelectric vibrator for piezoelectric vibration gyro - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric vibrator for a vibration gyro that uses ultrasonic vibration belonging to a gyroscope used mainly in an automobile navigation system or a camera shake correction mechanism of a camera-integrated VTR camera. The present invention relates to a piezoelectric vibrator for a vibration gyro using electric field excitation type energy confinement thickness shear vibration.
[0002]
[Prior art]
Conventionally, this type of piezoelectric vibrating gyroscope is known to belong to a gyroscope that utilizes a mechanical phenomenon in which when a rotating angular velocity is applied to a vibrating object, a Coriolis force is generated in a direction perpendicular to the vibrating direction. ing.
[0003]
In general, in a piezoelectric vibration gyro, in a composite vibration system configured to be able to excite vibrations in two different directions orthogonal to the piezoelectric vibrator, when the piezoelectric vibrator is rotated with one vibration excited, the action of the Coriolis force is exerted. Thus, a force acts in a direction perpendicular to the vibration direction, 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, the magnitude of the applied rotational angular velocity should be determined based on the output voltage when the input side vibration amplitude is constant. Can do.
[0004]
FIG. 8 is a perspective view showing a basic configuration of a conventional piezoelectric vibrator for a piezoelectric vibration gyro. In this piezoelectric vibrator, piezoelectric ceramic thin plates 52 and 53 are bonded to substantially the center of two adjacent surfaces of a metal prism 51 having a square cross section. Each of these piezoelectric ceramic thin plates 52 and 53 has electrodes formed on both surfaces and is polarized in the thickness direction. In addition, lead wires 54 and 55 for lead-out are connected to the piezoelectric ceramic thin plates 52 and 53, respectively.
[0005]
In this piezoelectric vibrator, 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. It is known.
[0006]
Therefore, for example, when a voltage having a frequency approximately 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 in the Ω direction around the axis (z axis) parallel to the length direction, the surface of the metal prism 51 joined to the piezoelectric ceramic thin plate 53 by the action of the Coriolis force becomes uneven. The piezoelectric ceramic thin plate 53 generates an output voltage by bending vibration in the direction (x-axis direction).
[0007]
Since the magnitude of the output 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, if the magnitude of the excitation voltage applied to the piezoelectric ceramic thin plate 52 is constant. The output voltage generated in the piezoelectric ceramic thin plate 53 becomes a voltage proportional to the rotational angular velocity of the metal prism 51. When a piezoelectric vibration gyro is configured, such a piezoelectric vibrator is combined with an electric circuit having a drive / detection function.
[0008]
[Problems to be solved by the invention]
In the case of the piezoelectric vibrator for the piezoelectric vibration gyro described above, since the bending vibration mode of the metal prism is used, when the piezoelectric vibration gyro is configured, the piezoelectric vibrator must be supported and fixed at the position of the vibration node. Therefore, there is a problem that it takes time to assemble.
[0009]
In addition, when configuring a piezoelectric vibration gyro, it is necessary to connect the electrical circuit having a drive / detection function and the electrode of the piezoelectric vibrator with a lead wire. However, variations in the gyro characteristics due to variations in the connection state at this time are required. There is also a problem that it is difficult to suppress.
[0010]
Furthermore, when a piezoelectric vibration gyro is configured, a piezoelectric vibrator is mounted on a substrate having an electric circuit having a drive / detection function and supported by a holder for assembly. There is also a problem that it is difficult to construct a vibrating gyroscope.
[0011]
The present invention has been made to solve such problems, and its technical problem is that it has a simple structure that can be connected to an input / output terminal without using a lead wire, and is small and thin. A high-performance piezoelectric vibrator for a piezoelectric vibration gyro is provided.
[0012]
[Means for Solving the Problems]
According to the present invention, a plurality of electrodes including at least one drive and an even number of detection electrodes extending from the outside toward the vicinity of the central portion on at least one main surface of the piezoelectric plate having a polarization axis component in the thickness direction are provided. A parallel electric field excitation type energy confinement thickness-shear vibration is formed, and the even number of detection electrodes are arranged symmetrically with respect to the direction of the excitation vibration caused by the application of the drive voltage to the drive electrode. In the piezoelectric vibration gyro, the piezoelectric plate is formed around a flat portion having a symmetrical shape with respect to the direction of excitation vibration in a local portion surrounded by ends of a plurality of electrodes in the vicinity of the central portion of the main surface. A piezoelectric vibrator for a piezoelectric vibration gyro having a hollow portion is obtained.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the piezoelectric vibrator for piezoelectric vibration gyro of the present invention will be described in detail with reference to the drawings.
[0014]
FIG. 1 is a perspective view showing a basic configuration of a piezoelectric vibrator 1 for a piezoelectric vibration gyro according to an embodiment of the present invention. This piezoelectric vibrator 1 uses parallel electric field excitation type energy confinement thickness-shear vibration described later, and is applied to one main surface of a rectangular (rectangular) piezoelectric plate 10 having a polarization axis component in the thickness direction from the outside. A plurality (three in this case) of electrodes 11, 12, 13 including driving and detection extending toward the vicinity of the central portion are formed, and two (even) of these electrodes 11, 12, 13 are formed. The detection electrodes 12 and 13 are arranged at positions symmetrical with respect to the direction of excitation vibration generated by applying a drive voltage to the drive electrode 11.
[0015]
In the piezoelectric vibrator 1, the driving electrode 11 and the detection electrodes 12 and 13 are formed on the piezoelectric plate 10 at the positions of the apexes that form an isosceles triangle approximately in the vicinity of the center of the main surface. A rectangular flat portion having a shape symmetric with respect to the direction of the excitation vibration generated by the application of the drive voltage to the drive electrode 11 at the local portion surrounded by the ends of the electrodes 11, 12, 13 in the vicinity of the central portion of the main surface 10b and the rectangular hollow part 10a formed in the circumference | surroundings, and the edge part of the electrodes 11, 12, and 13 has extended in the hollow part 10a.
[0016]
That is, in this piezoelectric vibrator 1, the region surrounded by the opposing drive electrode 11 and detection electrodes 12 and 13 is symmetric with respect to the direction of the excitation vibration generated by the application of the drive voltage to the drive electrode 11. By leaving the flat portion 10b having a shape and forming a recess 10a around it, the two detection electrodes 12, 13 and the recess 10a and the flat portion 10b are symmetrical with respect to the direction of the excitation vibration. Since it has a shape (a shape that is line-symmetric with respect to the same axis as the symmetry axis of the two detection electrodes 12 and 13), the resonance frequency of the thickness vibration in the region surrounded by the electrodes 11, 12, and 13 is reduced. Since it is different from the propagation characteristics in the region of the electrode, the energy confinement state (concentration) is improved as a result.
[0017]
Generally, in a piezoelectric vibrator for a vibrating gyroscope, it is necessary to arrange a plurality of detection electrodes symmetrically with respect to the direction of excitation vibration. This is because the piezoelectric vibrator is symmetrical in shape and characteristically. This is because it is assumed to be uniform. In the case of the piezoelectric vibrator 1 as well, the shape of the piezoelectric vibrator 1 is changed in order to arrange the detection electrodes 12 and 13 symmetrically with respect to the direction of the excitation vibration. It needs to be symmetric.
[0018]
The energy confinement phenomenon that occurs in the piezoelectric vibrator 1 is due to the difference in the end-point propagation characteristics with respect to the elastic wave of interest. Incidentally, in the case of a general piezoelectric vibrator, a frequency difference occurs between the electrode part and the non-electrode part due to the mass addition effect of the electrode part or the electrode short-circuit effect in vertical electric field excitation, so that energy confinement at the electrode part is possible It becomes.
[0019]
By the way, when piezoelectric ceramic is used as the material of the piezoelectric plate 10, if only the region used for driving and detection is polarized, it becomes possible to cause an end change in propagation characteristics due to the presence or absence of polarization. The energy confinement state can be improved.
[0020]
However, since the piezoelectric ceramic material is a sintered polycrystalline body, the internal characteristics of the material are non-uniform compared to a single crystal body, the temperature characteristics vary greatly due to changes in the ambient temperature, and the rate of change There are drawbacks in various aspects such as large variations.
[0021]
In contrast, LiNbO ₃ and LiTaO ₃ known as piezoelectric single crystals have been obtained with stable temperature characteristics by selecting the cutting orientation, and are widely used in surface wave devices, It is impossible to create regions with different propagation characteristics by polarization processing.
[0022]
In the case of the piezoelectric vibrator 1 here, a detailed structure in which a recess 10 a is formed around the flat portion 10 b in a local portion surrounded by the ends of the electrodes 11, 12, 13 in the vicinity of the central portion of the main surface of the piezoelectric plate 10. Since it is improved, it is also effective to use a piezoelectric single crystal, and the material is not particularly limited. In any case, if such a piezoelectric vibrator 1 is mounted on a substrate having an electric circuit having a driving and detecting function, the piezoelectric vibration having a simple structure and easy support and excellent vibration resistance and shock resistance. A gyro is obtained.
[0023]
FIG. 2 is a block diagram showing a configuration according to an example of an electric circuit when the piezoelectric vibrator 1 shown in FIG. 1 is applied to a piezoelectric vibration gyro. In this electric circuit, the drive electrode 11 in the piezoelectric vibrator 1 is grounded, and the AC electrodes 22 are connected to the detection electrodes 12 and 13 via resistors 20 and 21, respectively. The output sides of the detection electrodes 12 and 13 are connected to the input terminals of the differential amplifier circuit 23, respectively. The output side of the differential amplifier circuit 23 is connected to the output terminal (sensor output of the piezoelectric vibration gyro and the sensor output) via the detection circuit 24. Connected).
[0024]
That is, here, in the piezoelectric vibrator 1, the driving electrode 11 is arranged at the apex angle position, the detection electrodes 12 and 13 are arranged at the base angle positions, and the driving electrode 11 is grounded. An AC power source 22 is connected to the detection electrodes 12 and 13 via resistors 20 and 21, respectively.
[0025]
In the case of this piezoelectric vibration gyro, when an excitation drive voltage having a frequency substantially equal to the resonance frequency of the thickness-slip mode of the piezoelectric plate 10 is applied from the AC power source 22 to the detection electrodes 12 and 13 via the resistors 20 and 21, respectively. , Energy confining slip vibration in a direction connecting the center of the drive electrode 11 and the center of the detection electrode 12 to a region surrounded by the electrodes 11, 12, and 13, and the center of the drive electrode 11 and the center of the detection electrode 13. Energy confining slip vibration in the direction connecting the two, and these vibrations are combined and energy in the direction of the straight line connecting the midpoint of the straight line connecting the center of the drive electrode 11 and the centers of the detection electrodes 12 and 13. Confinement sliding vibration occurs.
[0026]
In this state, as shown in FIG. 1, when the piezoelectric plate 10 is rotated around an axis orthogonal to the principal surface, the thickness in a direction perpendicular to the direction of the thickness-shear vibration excited by the action of the Coriolis force. Sliding vibration occurs. The impedance between the drive electrode 11 and the detection electrode 12 and between the drive electrode 11 and the detection electrode 13 is changed by the thickness shear vibration generated by the Coriolis force, and as a result, the detection electrodes 12 and 13 are changed. The terminal voltage changes.
[0027]
Since this change in impedance is proportional to the applied rotational angular velocity when the excitation voltage is constant, the difference between the terminal voltages of the detection electrodes 12 and 13 is detected by the differential amplifier circuit 23, and this voltage is detected by the detection circuit 24. By performing synchronous detection at a predetermined timing, an output voltage proportional to the applied rotational angular velocity can be obtained.
[0028]
FIG. 3 is a block diagram showing a configuration according to another example of an electric circuit when the piezoelectric vibrator 1 shown in FIG. 1 is applied to a piezoelectric vibration gyro. In this electric circuit, the drive electrode 11 in the piezoelectric vibrator 1 is grounded via a resistor 34 and an AC power supply 22, and the detection electrodes 12 and 13 have current detection circuits 35 and 36 each having a virtual ground function. It is connected. The output sides of the current detection circuits 35 and 36 are respectively connected to the input side of the differential amplifier circuit 37, and the output side of the differential amplifier circuit 37 is connected to the detection circuit 38. Here, the output of the detection circuit 38 becomes the sensor output of the piezoelectric vibration gyro.
[0029]
In the case of this piezoelectric vibration gyro, similarly to the case described above, an excitation drive voltage having a frequency substantially equal to the resonance frequency of the thickness-slip mode of the piezoelectric plate 10 is applied to the drive electrode 11 from the AC power source 22 via the resistor 34. When applied, energy trapping sliding vibration occurs in the direction of a straight line connecting the midpoints of the straight lines connecting the center of the drive electrode 11 and the centers of the detection electrodes 12 and 13.
[0030]
In this state, as shown in FIG. 1, when the piezoelectric plate 10 is rotated around an axis orthogonal to the principal surface, the thickness in a direction perpendicular to the direction of the thickness-shear vibration excited by the action of the Coriolis force. Since the slip vibration is generated, the current flowing from the detection electrodes 12 and 13 to the current detection circuits 35 and 36 having the virtual ground function is changed by the thickness slip vibration generated by the Coriolis force, and the current detection circuits 35 and 36 are generated. The differential amplifier circuit 37 detects the voltage difference between the output voltages, and this voltage is synchronously detected at a predetermined timing by the detection circuit 38, whereby an output voltage proportional to the applied rotational angular velocity can be obtained.
[0031]
FIG. 4 shows a basic configuration of a piezoelectric vibrator having a simplified structure for explaining the parallel electric field excitation type energy confinement thickness-shear vibration employed in the piezoelectric vibrator 1 shown in FIG. The figure (a) relates to the plan view, and the figure (b) relates to the side view from one direction.
[0032]
In this piezoelectric vibrator, strip-shaped portions facing each other at a predetermined interval in the x-axis direction on the same surface of the central portion of the rectangular piezoelectric plate 100 having a polarization axis component in the thickness direction (z-axis direction). Electrodes 101 and 102 are formed. Since an electric field is applied to the portion sandwiched between the partial electrodes 101 and 102 in a direction substantially parallel to the plate surface (x-axis direction), the electrode is affected by the interaction with the polarization in the thickness direction perpendicular to the electric field. In the inter-region, distortion occurs in the x direction.
[0033]
Therefore, if the dimensions of the partial electrodes 101 and 102 are appropriately designed in accordance with the characteristics of the piezoelectric plate using the thickness, the thickness shear vibration can be excited in the distorted portion. The vibration is damped around the interelectrode region and confined without propagating, and as a result, an energy confined oscillator can be formed. This thickness shear vibration is a vibration in which the displacement direction is parallel to the plate surface and the wave propagation direction is in the plate thickness direction, but here it is caused by an electric field parallel to the plate surface of the piezoelectric plate. It can be regarded as sliding vibration.
[0034]
FIG. 5 shows a displacement distribution in the thickness direction (z-axis direction) when the piezoelectric plate 100 shown in FIG. 4 resonates at half wavelength. Here, it can be seen that the displacement of the piezoelectric plate 100 exhibits excellent symmetry.
[0035]
FIG. 6 is a perspective view showing a basic configuration of a piezoelectric vibrator 1 ′ for a piezoelectric vibration gyro according to another embodiment of the present invention.
[0036]
The basic configuration of the piezoelectric vibrator 1 is the same as that shown in FIG. 1, but the flat portion 10 b left in the vicinity of the central portion of the main surface of the piezoelectric plate 10 and the hollow portion 10 a around it. The shape is trapezoid. In the piezoelectric vibrator 1 as well, as in the case shown in FIG. 1, the two detection electrodes 12 and 13 are positioned symmetrically with respect to the direction of the excitation vibration generated by the application of the drive voltage to the drive electrode 11. The recesses 10a and the flat portions 10b are symmetrical with respect to the direction of excitation vibration (a shape symmetrical with respect to the same axis as the symmetry axis of the two detection electrodes). The filling state (concentration) is improved.
[0037]
FIG. 7 is a perspective view showing a basic configuration of a piezoelectric vibrator 1 ′ for a piezoelectric vibration gyro according to another embodiment of the present invention.
[0038]
In the case of the piezoelectric vibrator 1, the end portions of the electrodes 11, 12, and 13 extend into the recessed portion 10 a in the case shown in FIGS. 1 and 6, but here, the ends of the electrodes 11, 12, and 13 are extended. The part does not enter the recessed part 10a, but extends along the periphery thereof. In the piezoelectric vibrator 1 as well, as in the case shown in FIGS. 1 and 6, the two detection electrodes 12 and 13 are driven in the direction of the excitation vibration caused by the application of the drive voltage to the drive electrode 11. Since the recesses 10a and the flat portions 10b are arranged in symmetrical positions, the shapes of the recesses 10a and the flat portions 10b are symmetrical with respect to the direction of excitation vibration (a shape symmetrical with respect to the same axis as the symmetry axis of the two detection electrodes) , Energy confinement (concentration) becomes better.
[0039]
【The invention's effect】
As described above, according to the piezoelectric vibrator for a piezoelectric vibration gyro of the present invention, it has a simple structure that can be connected to an input / output terminal without using a lead wire, and is small and thin with high performance. As a result, it is possible to provide a strong support with little influence on the gyro characteristics due to support and fixing, and as a result, a high-performance piezoelectric vibration gyro with excellent vibration resistance and shock resistance can be obtained. Be able to.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a basic configuration of a piezoelectric vibrator for a piezoelectric vibration gyro according to an embodiment of the present invention.
2 is a block diagram showing a configuration according to an example of an electric circuit when the piezoelectric vibrator shown in FIG. 1 is applied to a piezoelectric vibration gyro;
FIG. 3 is a block diagram showing a configuration according to another example of an electric circuit when the piezoelectric vibrator shown in FIG. 1 is applied to a piezoelectric vibration gyro;
FIG. 4 shows a basic configuration of a piezoelectric vibrator having a simplified structure for explaining parallel electric field excitation type energy confinement thickness-shear vibration employed in the piezoelectric vibrator shown in FIG. ) Relates to the plan view, and (b) relates to the side view from one direction.
FIG. 5 shows a displacement distribution in the thickness direction (z-axis direction) when the piezoelectric plate shown in FIG. 4 resonates at half wavelength.
FIG. 6 is a perspective view showing a basic configuration of a piezoelectric vibrator for a piezoelectric vibration gyro according to another embodiment of the present invention.
FIG. 7 is a perspective view showing a basic configuration of a piezoelectric vibrator for a piezoelectric vibration gyro according to another embodiment of the present invention.
FIG. 8 is a perspective view showing a basic configuration of a conventional piezoelectric vibrator for a piezoelectric vibration gyro.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piezoelectric vibrator | oscillator 10,100 Piezoelectric plate 10a Depression part 10b Flat part 11 Drive electrode 12,13 Detection electrode 101,102 Partial electrode 20,21,34 Resistor 22 AC power supply 23,37 Differential amplification circuit 24,38 Detection circuits 35, 36 Current detection circuit 51 Metal prisms 52, 53 Piezoelectric ceramic thin plates 54, 55 Lead terminals

Claims (1)

A plurality of electrodes including at least one drive and an even number of detections extending from the outside toward the vicinity of the central portion are formed on at least one main surface of the piezoelectric plate having a polarization axis component in the thickness direction, In the piezoelectric vibration gyro using the parallel electric field excitation type energy confinement thickness shear vibration in which the even number of detection electrodes are arranged at positions symmetrical to the direction of the excitation vibration generated by applying the drive voltage to the drive electrode, The piezoelectric plate is formed in a local portion surrounded by the ends of the plurality of electrodes in the vicinity of the central portion on the main surface, and a flat portion having a symmetrical shape with respect to the direction of the excitation vibration, and around the flat portion. A piezoelectric vibrator for a piezoelectric vibration gyro characterized by having a recess.

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