JPH1183496A - Piezoelectric vibrator and piezoelectric-vibrative angular velocity meter using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric vibrator which has good sensing efficiency for the rotational angular velocity and can be mass-produced at a low cost. SOLUTION: The piezoelectric vibrator 100 is composed of a piezoelectric body in the form of a quadrangular prism so as to sense the rotational angular velocity round the longitudinal axis. In this piezoelectric vibrator 100, a polarization process dominated by the polarized component in the thickness direction is applied to one of the sides across the thickness (oversurface) in a plane perpendicular to the longitudinal axis of the piezoelectric body while a polarization process deominated by polarization in the width direction is applied to the other side (undersurface), and electrodes 101-106 are formed on two side faces opposing across the thickness (oversurface and undersurface) among the four side faces parallel with the longitudinal axis of the piezoelectric body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to navigation systems for aircraft, ships, automobiles, etc., and attitude control of these systems.
Alternatively, the present invention relates to a piezoelectric vibrator used for a piezoelectric vibrating gyro used for detecting a camera shake or vibration of a still camera or a video camera.

[0002]

2. Description of the Related Art A piezoelectric vibrating gyro measures a vibrator in a vibrating state when an angular velocity associated with a rotational motion is given.
This is an angular velocity meter that utilizes the phenomenon that Coriolis force is generated in the form of the cross product of the vibration direction and angular velocity, and the Coriolis force generates vibration in a direction perpendicular to the vibration direction of the vibrator.
The Coriolis force is expressed by the following equation (1).

[0003]

Fc = 2m · (v × Ω) (1) where Fc: Coriolis force, m: mass of vibrator, v: vibration speed of vibrator Ω: rotational angular speed

As a vibration angular velocity meter, two types of piezoelectric vibration angular velocity meters of a GE type and a Watson type utilizing a piezoelectric positive (direct) effect and a piezoelectric inverse effect have been well known.

As shown in FIG. 12, a GE type piezoelectric vibration angular velocity meter has a piezoelectric ceramic plate 51 adhered to a rod-shaped vibrator 50 made of metal (for example, a constant elastic body such as an elinvar). The metal oscillator 5
0 is excited, and the Coriolis force generated in a direction perpendicular to the excitation direction with the rotation of the vibrator 50 is detected. The vibration mode of the vibrator 50 is an unconstrained fundamental mode lateral vibration, and the vibrator 50 is usually used by fixing the vibrator 50 to a base at a node of the vibration.

As shown in FIG. 13, a Watson-type piezoelectric vibration gyro has four piezoelectric ceramic bimorphs 5.
5 and 56 are superposed two by two so as to be orthogonal to each other to form a tuning fork. The entirety of the tuning fork is excited by the driving piezoelectric bimorph 55, and the Coriolis force generated by the rotation is detected by the detection bimorph 56.

[0007]

When a metal is used as a vibrator as in a GE type piezoelectric vibrating gyro, it is necessary to join a piezoelectric element (piezoelectric ceramic or the like) to the vibrator. When the vibrator has a bimorph structure as in the piezoelectric vibration gyro described above, it is necessary to join the piezoelectric ceramics together. Therefore, when the vibrator is excited, the adhesive also vibrates together to reduce the detection efficiency, and the change in the adhesive due to the temperature changes the vibration state and causes a change in the angular velocity detection sensitivity. Furthermore, in the type having these joining steps, it is necessary to join the piezoelectric elements one by one for each vibrator, and not only the joining step becomes a hindrance factor in considering the production efficiency at the time of mass production, This is also a major factor in causing variations in the characteristics of the individual vibrators.

In particular, GE type piezoelectric vibrating gyros which have a simple structure and are suitable for miniaturization have recently been developed, for example, those using a triangular prism metal vibrator and those using cylindrical piezoelectric ceramics as vibrators. However, in the case of using a triangular prism-shaped metal vibrator and bonding a piezoelectric element to the side surface thereof, in addition to the above-mentioned problems, the manufacturing process at the time of mass production of the vibrator is further complicated, When using a piezoelectric ceramic vibrator, it is necessary to form electrodes on the cylindrical side using a roll-type printing machine, etc., and then separately perform polarization processing. In this case, the production efficiency at the time is deteriorated, and both have a problem in manufacturing a vibrator at low cost. In particular, those formed with electrodes on cylindrical piezoelectric ceramics have a small range in which the polarization process can be performed after the electrodes are formed,
As a result, there is a disadvantage that the detection efficiency is deteriorated.

According to the present invention, there is provided a piezoelectric vibrator which improves mass production and characteristics of the conventional vibrator for a piezoelectric vibrating gyro as described above, has good rotational angular velocity detection efficiency, and can be mass-produced at low cost. It is an object to provide a vibrator.

[0010]

In order to achieve the above object, the present invention relates to a piezoelectric vibrator which is constituted by a quadrangular prism-shaped piezoelectric body and detects a rotational angular velocity about a longitudinal axis. A polarization process in which the polarization component in the thickness direction is dominant is performed on one side in the thickness direction in a plane perpendicular to the direction axis, and a polarization process in which the polarization in the width direction is dominant is performed on the other side. Electrodes are formed on two opposing side surfaces in the thickness direction of the four side surfaces parallel to the longitudinal axis of the piezoelectric body to form a piezoelectric vibrator.

As this electrode, a pair of drive signal input electrodes extending parallel to the longitudinal axis and symmetrical in the width direction are separated from the two opposing side surfaces on the side where polarization in the width direction is dominant. And forming a drive reference electrode extending in the center in the width direction in parallel with the longitudinal axis between the pair of drive signal input electrodes, and among the two opposing side surfaces,
A pair of Coriolis signal detection and feedback electrodes extending parallel to the longitudinal axis and symmetric in the width direction are formed on the side surface on the side where polarization in the thickness direction is dominant, and these pair of Coriolis signal detection electrodes In some cases, a reference electrode is formed between the electrodes for feedback and extends in the center in the width direction in parallel with the longitudinal axis.

As another electrode example, a pair of drive reference electrodes extending parallel to the longitudinal axis and symmetrical in the width direction are separated from the two opposing side surfaces on the side where polarization in the width direction is dominant. And forming a drive signal input electrode extending in the center in the width direction in parallel with the longitudinal axis between the pair of drive reference electrodes, and in the two opposing side surfaces, the polarization in the thickness direction is dominant. A pair of Coriolis signal detection and feedback electrodes extending parallel to the longitudinal axis and symmetric in the width direction are formed on the side surface on the side, and a pair of Coriolis signal detection and feedback electrodes are formed in the width direction between the pair of Coriolis signal detection and feedback electrodes. In some cases, a reference electrode is formed extending in the center parallel to the longitudinal axis.

[0013] As such a polarization treatment of the vibrator, the polarization in the thickness direction is shifted from the center electrode of the three electrodes formed on the side surface on the side where polarization in the width direction is dominant. In the region where polarization in the width direction is dominant and in the region where polarization in the width direction is dominant, the polarization spreads in a fan shape toward the three electrodes formed on the side surface of Some of the three electrodes are provided with polarization extending in the width direction from the center electrode to the left and right electrodes.

Further, as another polarization treatment, the left and right electrodes of the three electrodes formed on the side surface on which the polarization in the width direction is dominant are formed on the side surface on the side on which the polarization in the thickness direction is dominant. In the region where the polarization spreading in the thickness direction and spreading in the direction of a fan toward the three electrodes, and the polarization in the width direction is dominant,
Some of the three electrodes formed on the side surface where the polarization in the width direction is dominant have polarizations extending in the width direction from the left and right electrodes to the center electrode.

When a piezoelectric vibrating gyro is constructed using the piezoelectric vibrator having the above structure, a driving AC signal is applied to a driving signal input electrode to cause the piezoelectric vibrator to flexurally vibrate in the thickness direction. Some include an excitation drive circuit and a Coriolis signal detection circuit that detects a difference between output signals from a pair of Coriolis signal detection and feedback electrodes to detect a Coriolis signal.

On the other hand, a pair of drive signal input electrodes extending parallel to the longitudinal axis and symmetrical in the width direction are formed on the side of the two opposing side surfaces on the side where polarization in the thickness direction is dominant. A drive reference electrode is formed between the pair of drive signal input electrodes so as to extend in the center in the width direction in parallel with the longitudinal axis, and a side surface of the two opposed side surfaces on which the polarization in the width direction is dominant. A pair of Coriolis signal detection and feedback electrodes extending parallel to the longitudinal axis and symmetrical in the width direction are separated from each other, and the center in the width direction is longitudinally formed between the pair of Coriolis signal detection and feedback electrodes. A piezoelectric vibrator can also be formed by forming a reference electrode extending parallel to the direction axis.

When a piezoelectric vibrating gyro is constructed using such a piezoelectric vibrator, an excitation drive circuit for applying a drive AC signal to a drive signal input electrode to flexurally vibrate the piezoelectric vibrator in the width direction is provided. And a Coriolis signal detection circuit that detects a difference between output signals from a pair of Coriolis signal detection and feedback electrodes to detect a Coriolis signal.

A drive signal input electrode and a feedback reference electrode extend parallel to the longitudinal axis and are spaced apart in the width direction on the side surface of the two opposing side surfaces on the side where polarization in the width direction is dominant. A pair of Coriolis extending parallel to the longitudinal axis and symmetrical in the width direction are formed on the side of the two opposing side surfaces on which the polarization in the thickness direction is dominant. It is also possible to form a piezoelectric vibration by forming the signal detection electrodes apart and forming a Coriolis detection reference electrode extending in the center in the width direction parallel to the longitudinal axis between the pair of Coriolis signal detection electrodes. .

When a piezoelectric vibrating gyro is constructed using such a piezoelectric vibrator, a driving AC signal is applied to a driving signal input electrode and a feedback reference electrode to bend the piezoelectric vibrator in the thickness direction. An excitation drive circuit that vibrates and a Coriolis signal detection circuit that detects a difference between output signals from a pair of Coriolis signal detection electrodes to detect a Coriolis signal are used.

Further, a pair of Coriolis signal detection electrodes extending parallel to the longitudinal axis and symmetric in the width direction are formed on the side surface of the two opposing side surfaces on the side where the polarization in the width direction is dominant, Further, a Coriolis detection reference electrode extending in the center in the width direction in parallel with the longitudinal axis is formed between the pair of Coriolis signal detection electrodes, and of the two opposing side surfaces, the polarization direction in the thickness direction is the dominant side. A piezoelectric vibrator may be formed by forming a drive signal input electrode / feedback reference electrode and a feedback electrode / drive reference electrode on the side surface so as to extend in parallel with the longitudinal axis and be spaced apart in the width direction.

When a piezoelectric vibrating gyro is constructed using such a piezoelectric vibrator, a driving AC signal is applied to the driving signal input electrode and the feedback reference electrode to cause the piezoelectric vibrator to flexurally vibrate in the width direction. An excitation drive circuit for
A Coriolis signal detection circuit for detecting a Coriolis signal by detecting a difference between output signals from a pair of Coriolis signal detection electrodes is used.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. As described above, the vibrator of the present invention uses both electro-mechanical energy conversion and mechanical-electrical energy conversion by the piezoelectric effect, and applies an AC charge to excite primary bending resonance vibration. The Coriolis force F generated in proportion to the vibration velocity v of the vibrator and the applied angular velocity Ω is evaluated by measuring the charge generated by the primary bending resonance vibration excited by the Coriolis force F. Therefore, first, the basic operation principle will be described below.

FIG. 5 is a view showing the principle of operation as a piezoelectric vibrating gyroscope according to a preferred embodiment of the present invention, and all are cross-sectional views of the vibrator viewed from the longitudinal direction. In this vibrator, polarization is made in the thickness direction, and three electrodes are provided on the upper surface. Here, as shown in FIG. 5 (a), considering only the electric field in the direction between the electrodes, the polarization direction is orthogonal to the direction of the electric field, and the expected piezoelectric effect is only shear deformation around the axis of the vibrator. Therefore, bending deformation of the vibrator cannot be expected. However, it was confirmed that lateral bending vibration was actually generated in the vibrator by applying an AC electric field of opposite phase to the left and right electrodes using the middle electrode as a reference electrode.

FIG. 5B illustrates the principle of lateral bending vibration. When a negative voltage is applied to the left electrode and a positive voltage is applied to the right electrode using the middle electrode as the reference electrode among the three electrodes on the upper surface, an electric field is generated inside the piezoelectric body as shown in the figure. Occurs around. At this time, elongation in the polarization direction occurs at a portion on the right side of the center, and contraction in the polarization direction occurs on a left portion. Therefore, as a whole, the cross section of the vibrator is such that the right portion extends in the polarization direction and the left portion contracts in the polarization direction. As a result, with respect to the longitudinal direction of the vibrator, the vibrator contracts on the right side and expands on the left side, and the vibrator bends at its front and rear ends toward the right with respect to the center.

Therefore, an alternating voltage of opposite phase is applied to the left and right electrodes, and the resonance frequency f of the primary bending vibration in the lateral direction of the vibrator.
When input as 0, primary bending resonance vibration in the lateral direction of the piezoelectric vibrator is excited. This applies not only to the above-described electromechanical energy conversion (piezoelectric effect) but also to the generation of electric charge by mechanical-electric energy conversion (positive piezoelectric effect). In other words, when the vibrator bends toward the right side, elongation occurs on the left side of the cross section and contraction occurs on the right side in the longitudinal direction of the vibrator, so that shrinkage occurs on the left side in the polarization direction. Then elongation occurs on the right side. For this reason, when the middle one of the three electrodes on the upper surface of the vibrator is used as the reference electrode, the electric field is generated asymmetrically as shown in the figure, a negative charge is generated in the left electrode, and a negative charge is generated in the right electrode. A positive charge is generated at the electrode. Therefore, when the vibrator is bending and vibrating in the lateral direction, alternating charges of opposite phases are generated in the left and right electrodes.

When the vibrator is configured as described above, compared with a normal configuration in which the electrodes are arranged along the polarization direction as shown in FIG. It has been experimentally confirmed that the driving efficiency is excellent and the detection efficiency is also excellent when the amplitude of vibration is detected. Also, this method is effective only for driving and detecting horizontal vibration, and for vertical vibration,
Since both driving and detection are inactive, only lateral vibration can be handled independently.

Here, a piezoelectric vibrator according to a first embodiment of the present invention is shown in FIGS. 1, 2 and 3A, and a signal constituting a piezoelectric vibration angular velocity meter using this piezoelectric vibrator. The processing circuit is shown in FIG. This piezoelectric vibrator 10
0 indicates a region where the polarization component is dominant in the width direction (lower region), as indicated by an arrow in FIG. 1 and FIG.
And a quadrangular prism-shaped piezoelectric body that has been subjected to polarization processing so as to have a region in which the polarization component is dominant in the thickness direction (upper region), and two opposing surfaces (upper and lower surfaces in the figure)
Each has three electrodes, three in total. The surface on which the drive is performed (the lower surface in the figure) has three electrodes of drive signal input electrodes 104 and 106 and the drive reference electrode 105, and the opposite surface (the upper surface in the figure) has Coriolis. Signal detection and feedback electrodes 101 and 10
3 and a reference electrode 102.

In this vibrator, the drive vibration which is bending vibration in the longitudinal direction is excited by the drive electrode side portion where the polarization in the width direction is dominant, and the portion on the detection electrode side where the polarization in the thickness direction is dominant. Is used to detect Coriolis vibration, which is bending vibration in the lateral direction. Thus, the present vibrator can detect Coriolis force more efficiently than the conventional method.

As shown in FIG. 4, the electrodes 101 and 103 for Coriolis signal detection and feedback are connected to the-(minus) input terminals of the operational amplifiers 1a and 1b, respectively. The negative input terminal is connected to the output terminal of each operational amplifier via a feedback resistor, and the positive output terminal of each operational amplifier is connected to a reference potential. That is, the Coriolis signal detection and feedback electrode 1
01 and 103 are virtually grounded, and this configuration constitutes a known current-voltage converter 1. In this embodiment, the oscillation of the operational amplifier is prevented by connecting a capacitor in parallel with the feedback resistor.

Here, an in-phase AC voltage is applied to the drive signal input electrodes 104 and 106 from the signal generation circuit 6 for generating a drive signal for exciting and vibrating the vibrator, and the primary bending vibration of the vibrator in the longitudinal direction is applied. By inputting at the resonance frequency f0, the vibrator can be excited in the bending resonance vibration in the vertical direction. Accordingly, in-phase AC charges (currents) are generated in the Coriolis signal detection / feedback electrodes 101 and 103 on the opposite surface by the piezoelectric positive effect. This is a positive piezoelectric effect due to the component in the width direction of the polarization oblique to the thickness direction. Therefore, the in-phase excitation voltage accompanying the excitation is output from the current-voltage converter.

These two current-to-voltage converters are connected to a summing circuit 2 for taking their sum and a differential circuit 20 for taking their difference. The summing circuit is connected to a phase shifter 3 for shifting its output phase, and the output of the phase shifter 3 is connected to a comparator 4 for comparing with a specified voltage, and the comparator 4 outputs a monitor signal from the output. Monitor signal generation circuit 5 to generate
The oscillator is driven by self-excitation by positively feeding back the monitor signal to the signal generating circuit 6.

The comparator 4 is composed of, for example, an open collector type comparator 4a. The output of the phase shifter 3 is connected to the-input terminal of the comparator, and the specified voltage is input to the + input terminal. A resistor 5a is connected to an output terminal of the comparator 4a. The other end of the resistor 5a is connected in series with a resistor 5b having a resistance value approximately one digit larger than that of the resistor 5a, and the other end of the resistor 5b is pulled up. Further, a capacitor 5c having an appropriate capacity is connected in parallel with the resistor 5b. The portion composed of the resistors 5a and 5b and the capacitor 5c is the monitor signal generation circuit 5.

The comparator 4 becomes LOW when the output of the phase shifter is higher than the specified voltage, and becomes HIGH when the output is lower than the specified voltage. However, the output of the phase shifter 3 determines the HIGH level due to the effect of the capacitor 5c. The higher the voltage, the lower the voltage. Then, the monitor signal generation circuit 5
Again, due to the effect of the capacitor, a smoothed monitor signal is output to integrate the output of the comparator. For this reason, the level of the monitor signal becomes smaller as the output of the phase shifter becomes larger than the specified voltage. This monitor signal is input to the signal generation circuit 6a.

The monitor signal is switched at the resonance frequency of the vibrator by the signal generating circuit 6a, a rectangular wave is generated from the monitor signal, and the rectangular wave is integrated by the integrating circuit 6b to generate a triangular wave. Also in this case, the level of the triangular wave becomes smaller as the output of the phase shifter becomes larger than the specified voltage. Then, this triangular wave is connected to the drive signal input electrodes 104 and 106 of the vibrator, the phase shift amount of the phase shifter 3 is optimally set, and the phase shift of the triangular wave is made the same as the signal from the signal generation circuit 6. Then, the vibrator is self-excitedly driven in the lateral direction.

In this case, even if there is a variation in the driving efficiency between the transducers, the operation is performed so as to keep the output of the phase shifter 3 constant. In the case of high efficiency, the output of the phase shifter becomes constant by reducing the level of the driving triangular wave, and the variation can be absorbed. By using the AC signal as the feedback signal, the vibrator can be self-excited.

As other examples, 101 and 103
The phase and amplitude of the excitation signal from the
By controlling the amplitude and phase of the drive voltage to 4, 106, the primary bending vibration in the lateral direction can be driven stably by self-excited driving (the primary bending resonance vibration is generated only in the intended direction. Can be controlled so that a component in a direction perpendicular to the direction (direction in which Coriolis force is received) is not generated.) A drive circuit configuration is also conceivable but not shown here.

This primary bending vibration gives the motion indicated by v in FIG. At this time, a rotational motion occurs around the longitudinal axis of the piezoelectric vibrator, and as shown in FIG. 1, when an angular velocity Ω is given, the piezoelectric vibrator has a shape as shown by F in FIG. Force will act. This force is a Coriolis force, and is given by the above-described equation (1). Therefore, by measuring the Coriolis force F, it is possible to evaluate each angular velocity Ω of the rotational motion given around the longitudinal direction of the vibrator.

As can be said from the above equation (1), the Coriolis force F applied to the piezoelectric vibrator is determined according to the magnitude and direction of the vibration speed of the vibrator represented by v. In the case of the present vibrator, the direction of v becomes the same direction at both ends of the vibrator and the opposite direction at the center part because of the primary bending motion. Accordingly, the direction of the Coriolis force F also reflects the direction, takes the same direction at both ends of the vibrator and the opposite direction at the center, and fluctuates at the frequency f0 in conjunction with v. Therefore, the piezoelectric vibrator is excited by the Coriolis force F so as to excite the primary bending vibration at the frequency f0 even in the plane perpendicular to v. Furthermore, in the present embodiment, the bending vibration due to the Coriolis force F is also reduced in the v-direction by designing the resonance frequency of the bending vibration of the piezoelectric vibrator in the v-direction and the bending vibration in the F-direction perpendicular thereto to be equal. In the same manner as described above, the resonance vibration is excited.

Therefore, evaluating the magnitude of the primary flexural resonance vibration due to the Coriolis force F evaluates the given angular velocity Ω. To evaluate the magnitude of the bending vibration, the piezoelectric effect of the piezoelectric vibrator is used. That is, the magnitude of the Coriolis force F is determined by measuring the stress-induced charge generated by the bending vibration of the vibrator.

The detection of the charge generated by the Coriolis force Fc is as follows.
This is performed according to the principle shown in FIG. Since the bending vibration due to the Coriolis force occurs in a lateral direction that is perpendicular to the direction of the bending vibration due to the driving, an alternating-phase AC voltage is generated in the two Coriolis signal detection and feedback electrodes 101 and 103. Become. Since these are Coriolis signals of the same magnitude and opposite phases, by taking the difference between the signals from the electrodes 101 and 103, all Coriolis signals having the opposite phases can be extracted and have the same phase. The excitation signal of the drive excitation can be canceled. Conversely, by taking the sum of the signals from the electrodes 101 and 103,
It is possible to cancel all Coriolis signals having the opposite phase, and extract only the excitation signal of the drive excitation having the same phase.

In practice, by taking the difference between the outputs of the current-to-voltage converters by means of the differential circuit 20, only the Coriolis AC current signal of the opposite phase is taken out,
By performing synchronous detection using 0, an AC current signal corresponding to the rotational angular velocity is converted into a DC voltage signal. At this time, the synchronous detection timing is set to the same phase as the Coriolis signal by the phase circuit 60. Further, by amplifying a low-level DC voltage signal by the amplifier 40 and cutting out noise of unnecessary frequencies by the filter 50, a signal having a good S / N ratio can be taken out, and the accuracy of detecting angular velocity can be improved. Can be.

In this embodiment, by using the electrodes 104 and 106 as reference electrodes and the electrode 105 as a drive signal input electrode, the vibrator can also be excited in a longitudinal bending resonance vibration. In this case, detection of the Coriolis signal and extraction of the excitation signal are exactly the same.

In this embodiment, the roles of the three electrodes 104, 105, and 106 for driving and the three electrodes 101, 102, and 103 for detecting and feeding back a Coriolis signal can be used. In this case, the driving becomes bending vibration in the horizontal direction, and the Coriolis vibration becomes bending vibration in the vertical direction. As a result, the present vibrator can perform highly efficient driving in drive excitation as compared with the conventional method.

As shown in FIG. 3A, the polarization in this embodiment is a polarization (thickness direction polarization) that spreads from the lower central electrode 105 toward the three upper electrodes 101, 102, and 103 in a fan shape. Polarization (localization in the width direction) from the lower center electrode 105 to the lower left and right electrodes 104 and 106.

The piezoelectric vibrator 100 having such a polarization
Will be described with reference to FIG. First, the electrodes 101, 102, and 103 are continuously arranged in this order on the upper surface of a flat piezoelectric body having the same thickness as the vibrator 100 by screen printing using silver paste, vapor deposition, plating, or the like, in this order. And at the same time, on the lower surface, an electrode 10
4, 105, 106 are formed in a similar manner and in this order, continuously as shown. Then, all the electrodes 105, 102, 1 on the upper surface side are separated from the respective electrodes 105 at the center on the lower surface side.
03 to the lower central electrode 105.
From the polarization spreading in a fan shape upward from each,
At the same time, the lower center electrode 105 and the lower left electrode 10
A high voltage is applied to each of the electrodes 4 and 106 to perform polarization extending left and right from the lower central electrode 105 as shown in the figure. Thereafter, by cutting and separating the plate-shaped piezoelectric body along the broken line in the figure, a piezoelectric vibrator 100 having polarization as shown in FIG. 3A is obtained.

FIG. 3B shows a piezoelectric vibrator 200 according to a second embodiment of the present invention. This piezoelectric vibrator 200 also has three electrodes 201, 202, 203 on the upper surface and three electrodes 204, 205, 20 on the lower surface.
6, which are polarized as shown by arrows in the figure. As described above, also in this piezoelectric vibrator 200, the polarization in the thickness direction is dominant on the upper side, and the polarization in the width direction is dominant on the lower side. An gyro can be configured.

The piezoelectric vibrator 200 differs from the piezoelectric vibrator 100 of the first embodiment only in the polarization direction, and this polarization method will be described with reference to FIG. Also in this case, first, screen printing using silver paste, vapor deposition, or the like is performed on the upper surface of the flat piezoelectric body having the same thickness as the vibrator 200.
The electrodes 201, 202, and 203 are formed in this order by plating or the like as shown in the figure, and simultaneously, the electrodes 204, 205, and 206 are formed on the lower surface in the same manner and in this order as shown in the figure. Formed continuously. Then, a high voltage is applied from the lower left and right electrodes 204 and 206 to all the upper electrodes 201, 202 and 203, and polarization is spread from the lower left and right electrodes 204 and 206 in a fan shape upward, respectively. At the same time, a high voltage is applied from the lower left and right electrodes 204 and 206 to the lower central electrode 205, and polarization is performed from the lower left and right electrodes 204 and 206 toward the central electrode 205 as shown in the figure. Thereafter, by cutting and separating the plate-shaped piezoelectric body along the broken line in the figure, a piezoelectric vibrator 200 having polarization as shown in FIG. 3B is obtained.

The vibrator used in the third embodiment of the present invention is shown in FIGS. 8 and FIG.
The direction of polarization in the inside is indicated by an arrow, and the vibrator 300
Is a quadrangular prism-shaped piezoelectric body that has been subjected to polarization processing so that it has a region where polarization is dominant in the width direction (lower surface region) and a region where polarization is dominant in the thickness direction (upper surface region). Have. Two electrodes 304 and 305 extending in the longitudinal direction are formed on the lower surface (the surface of the region where the polarization in the width direction is dominant) of the piezoelectric body, and a drive signal input / feedback reference electrode 304 and a feedback reference electrode 304 are provided. And a driving reference electrode 305. The upper surface of the piezoelectric body (three electrodes 301, 302, 303 extending in the longitudinal direction are formed on the surface of the region where polarization in the thickness direction is dominant), and the Coriolis signal detection electrodes 301, 303 and the Coriolis detection reference And an electrode 303.

This vibrator also excites the driving vibration, which is bending vibration in the vertical direction, by the portion on the driving electrode side where the polarization in the width direction is dominant, and the portion on the detection electrode side where the polarization in the thickness direction is dominant. Is used to detect Coriolis vibration, which is bending vibration in the lateral direction. .

In the vibrator 300 having such a configuration,
Drive signal input electrode and feedback reference electrode 304
Input to the vibrator 300 at the resonance frequency f0 of the primary bending vibration in the longitudinal direction.
Can be excited in the longitudinal direction at a primary resonance frequency. At this time, in-phase AC charges are generated on the feedback electrode / drive reference electrode 305 due to the positive piezoelectric effect. By using this AC signal as a feedback signal, the vibrator 300 can be self-excited. The reference electrodes are all used in a virtual ground state.

This primary bending vibration gives a motion indicated by v in FIG. At this time, the piezoelectric vibrator 3
Rotational motion about the longitudinal axis of 00 occurs, FIG.
As shown in FIG. 8, when the angular velocity Ω is given, a Coriolis force as shown by F in FIG. 8 acts on the piezoelectric vibrator. By measuring the Coriolis force F, it is possible to evaluate each angular velocity Ω of the rotational motion given around the longitudinal direction of the vibrator.

That is, as described in the first embodiment, the evaluation of the magnitude of the primary bending resonance vibration caused by the Coriolis force F evaluates the given angular velocity Ω. To evaluate the magnitude of the bending vibration, the piezoelectric effect of the piezoelectric vibrator is used. That is, the magnitude of the Coriolis force F is determined by measuring the stress-induced charge generated by the bending vibration of the vibrator.

The detection of the charge generated by the Coriolis force Fc is as follows.
This is performed according to the principle shown in FIG. Since the bending vibration due to the Coriolis force occurs in a lateral direction which is a direction perpendicular to the direction of the bending vibration due to the driving, an alternating-phase AC voltage is generated in the two Coriolis signal detecting and feedback electrodes 301 and 303. Become. Since these are Coriolis signals of the same magnitude and opposite phases, by taking the difference between the signals from the electrodes 301 and 303, all Coriolis signals having the opposite phases can be taken out and have the same phase. The excitation signal of the drive excitation can be canceled. Conversely, by taking the sum of the signals from the electrodes 301 and 303,
It is possible to cancel all Coriolis signals having the opposite phase, and extract only the excitation signal of the drive excitation having the same phase.

By combining the piezoelectric vibrator 300 having such a configuration with an excitation driving circuit and a Coriolis signal detecting circuit as shown in FIG. 4, a piezoelectric vibration angular velocity meter can be constructed. The description is omitted because it is similar. However, in this case, the excitation drive circuit applies a drive AC signal to the drive signal input electrode and feedback reference electrode 304 to cause the piezoelectric vibrator 300 to bend and vibrate in the vertical direction (thickness direction). A pair of left and right Coriolis signal detecting electrodes 30 generated by Coriolis force applied when the vibrator 300 is rotated about a longitudinal axis.
The difference between the output signals from the signals 1,303 is detected by a Coriolis signal detection circuit.

In the present embodiment, the Coriolis signal detecting electrodes 301 and 303 can be used as feedback electrodes. In this case, since the feedback signal is output as an AC signal having the same phase between the electrodes 301 and 303, a signal obtained by summing the both becomes a feedback signal, and a signal obtained by operating the signal becomes a Coriolis signal.

Two electrodes for driving (a drive signal input electrode / feedback reference electrode 304 and a feedback electrode / drive reference electrode 305) and three electrodes for detecting a Coriolis signal (coriolis signal detection electrodes). Electrodes 301 and 303 and Coriolis detection reference electrode 30
The role of 3) can be switched and used. In this case, the driving becomes bending vibration in the horizontal direction, and the vibration generated by the Coriolis force becomes bending vibration in the vertical direction.

The piezoelectric vibrator 300 according to the third embodiment
In FIG. 10, the polarization as shown by the arrows in FIG. 10 is performed. The manufacture of the piezoelectric vibrator 300 having such polarization will be described with reference to FIG. First, the vibrator 300
The electrodes 301, 302, and 303 are formed on the upper surface of a flat piezoelectric body having the same thickness as that shown in FIG. , The lower surface has electrodes 304 and 3
05 are formed in a similar manner and in this order, as shown in FIG. Then, the electrodes 304 and 30 on the lower surface side
5, a high voltage is applied from the lower surface to all the electrodes 301, 302, and 303 to perform polarization processing extending from the lower surface to the upper surface in the thickness direction.
A high voltage is applied to each of the electrode groups 304 and 305 on the left side from the electrodes 04 and 305 to perform a polarization process that extends to the left in the width direction on the lower surface side as illustrated. Thereafter, by cutting and separating the plate-shaped piezoelectric body along the broken line in the figure, a piezoelectric vibrator 300 having polarization as shown in FIG. 10 is obtained.

In the embodiment described above, when a hard PZT ceramic is used as the piezoelectric body and a sawtooth wave is input as a drive signal, a sine wave is detected as a feedback signal, and the bending resonance vibration is excited. confirmed. Furthermore, when a rotational motion was performed around the longitudinal direction of the vibrator to give a constant angular velocity, an output corresponding to the magnitude of the angular velocity was obtained as a Coriolis signal.

Since the electrodes are present only on the upper and lower surfaces of the vibrator, the plate-like piezoelectric body is subjected to a polarization treatment at the time of manufacture.
After forming the electrodes, mass production can be performed by cutting into a predetermined vibrator shape. Therefore, it is not necessary to form an electrode or perform a polarization process on each of the vibrators, and a large number of vibrators can be produced simultaneously by batch processing. Further, in the present embodiment, the joining process of the piezoelectric body crys, which is advantageous not only for simplifying the manufacturing process and reducing the cost, but also for deteriorating the performance of the vibrator due to the presence of the adhesive layer and for individual variations. Can be minimized.

[0060]

As described above, according to the present invention,
A quadrangular piezoelectric body is subjected to a polarization process in which the polarization component in the thickness direction is dominant on one side in the thickness direction in a plane perpendicular to the longitudinal axis, and the polarization in the width direction is dominant on the other side. Since the target polarization processing is performed, electrodes are formed on two opposing side faces facing in the thickness direction of the four side faces parallel to the longitudinal axis of the piezoelectric body, so that the piezoelectric vibrator is configured.
Since electrodes can be formed on the piezoelectric body by screen printing with silver paste, vapor deposition, plating, etc., there is no adhesive part on the surface of the vibrator, and therefore, variations in individual characteristics of the vibrator adversely affect inspection accuracy. Also, there is very little possibility that the detection accuracy is adversely affected by a change in the temperature of the adhesive or the piezoelectric body. Further, since the vibrator is a single piezoelectric body having a square pole shape and the electrode surfaces only need to be provided on the upper and lower surfaces, a small-sized vibrator can be mass-produced with good reproducibility at low cost.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a piezoelectric vibrator according to a first embodiment of the present invention.

FIG. 2 is a three-view drawing showing an electrode arrangement of the vibrator according to the first embodiment.

FIG. 3 is a side view showing a polarization direction of the piezoelectric vibrator according to the first and second embodiments of the present invention.

FIG. 4 is an electric circuit diagram showing an example of the configuration of a piezoelectric vibration gyro using the vibrator according to the first embodiment.

FIG. 5 is a side view illustrating the excitation principle of the piezoelectric vibrator according to the present invention.

FIG. 6 is a side view for explaining the manufacturing process of the resonator according to the first embodiment.

FIG. 7 is a side view for explaining a manufacturing process of the resonator according to the second embodiment.

FIG. 8 is a perspective view showing a piezoelectric vibrator according to a third embodiment of the present invention.

FIG. 9 is a three-view drawing showing an electrode arrangement of a vibrator according to a third embodiment.

FIG. 10 is a side view showing a polarization direction of a piezoelectric vibrator according to a third embodiment.

FIG. 11 is a side view for explaining the manufacturing process of the resonator according to the third embodiment.

FIG. 12 is a conceptual diagram of a conventional vibration angular velocity meter.

FIG. 13 is a conceptual diagram of a conventional vibration angular velocity meter.

[Explanation of symbols]

REFERENCE SIGNS LIST 20 differential circuit 30 synchronous detection circuit 40 amplifier 50 filter 60 phase shift circuit 100 piezoelectric vibrator 101, 103 Coriolis signal detection and feedback electrode 102 reference electrode 104, 106 drive signal input electrode 105 drive reference electrode

Claims (12)

[Claims] 1. A piezoelectric vibrator made of a quadrangular prism-shaped piezoelectric body for detecting a rotational angular velocity about a longitudinal axis, wherein one side in a thickness direction in a plane perpendicular to the longitudinal axis of the piezoelectric body. A polarization process in which the polarization component in the thickness direction is dominant is performed, and a polarization process in which the polarization in the width direction is dominant is performed on the other side, and four side surfaces of the piezoelectric body parallel to the longitudinal axis. A piezoelectric vibrator, wherein electrodes are formed on two opposing side surfaces opposing each other in the thickness direction. 2. A pair of drive signal input electrodes extending parallel to the longitudinal axis and symmetrical in the width direction are separated from the two opposing side surfaces on the side where the polarization in the width direction is dominant. A driving reference electrode is formed and extends in the center in the width direction in parallel with the longitudinal axis between the pair of driving signal input electrodes. Of the two opposing side surfaces, the polarization in the thickness direction is formed. On the side surface on the dominant side, a pair of Coriolis signal detection and feedback electrodes that extend in parallel with the longitudinal axis and are symmetrical in the width direction are formed apart, and the pair of Coriolis signal detection and feedback electrodes are separated from each other. The piezoelectric vibrator according to claim 1, wherein a reference electrode extending in the width direction center and extending in parallel with the longitudinal axis is formed therebetween. 3. A pair of drive reference electrodes extending parallel to the longitudinal axis and symmetrical in the width direction are spaced apart from each other on the side of the two opposing side surfaces on which the polarization in the width direction is dominant. And a drive signal input electrode is formed between the pair of drive reference electrodes and extends in the center in the width direction in parallel with the longitudinal axis. Of the two opposed side surfaces, the polarization in the thickness direction is dominant. A pair of Coriolis signal detection and feedback electrodes extending parallel to the longitudinal axis and symmetric in the width direction are formed on the side of the target side, and are separated from each other, and between the pair of Coriolis signal detection and feedback electrodes. 2. The piezoelectric vibrator according to claim 1, wherein a reference electrode extending in the center in the width direction in parallel with the longitudinal axis is formed. 4. In a region where polarization in the width direction is dominant, a central electrode among the three electrodes formed on a side surface on a side where the polarization in the width direction is dominant is arranged in the thickness direction. In the region where the polarization in the width direction is dominant, and in the region where the polarization in the width direction is dominant, the polarization in the width direction is dominant. The piezoelectric vibrator according to claim 2, further comprising: a polarization extending in a width direction from a central electrode of the three electrodes formed on the side surface on the right side to the left and right electrodes. 5. 5. The region in which the polarization in the width direction is dominant, the polarization in the thickness direction from the left and right electrodes of the three electrodes formed on the side surface on the side in which the polarization in the width direction is dominant. And the polarization extending in the thickness direction in a fan shape toward the three electrodes formed on the side of the dominant side, and in the region where the width-direction polarization is dominant, the width-direction polarization is dominant 4. The piezoelectric vibrator according to claim 2, wherein the piezoelectric vibrator has a polarization extending in a width direction from the left and right electrodes of the three electrodes formed on the side surface to the center electrode. 5. 6. A piezoelectric vibrator according to claim 2, wherein: an excitation drive circuit that applies a drive AC signal to a drive signal input electrode to cause the piezoelectric vibrator to flexurally vibrate in a thickness direction. A piezoelectric vibration angular velocity meter comprising: a Coriolis signal detection circuit that detects a difference between output signals from the pair of Coriolis signal detection and feedback electrodes and detects a Coriolis signal. 7. A pair of drive signal input electrodes extending parallel to the longitudinal axis and symmetric in the width direction are provided on a side surface of the two opposing side surfaces on which the polarization in the thickness direction is dominant. A drive reference electrode is formed so as to be spaced apart from the pair of drive signal input electrodes and extends in the center in the width direction in parallel with the longitudinal axis. Of the two opposing side surfaces, the polarization in the width direction is formed. On the side surface on the dominant side, a pair of Coriolis signal detection and feedback electrodes that extend in parallel with the longitudinal axis and are symmetrical in the width direction are formed apart, and the pair of Coriolis signal detection and feedback electrodes are separated from each other. The piezoelectric vibrator according to claim 1, wherein a reference electrode extending in the width direction center and extending in parallel with the longitudinal axis is formed therebetween. 8. A piezoelectric vibrator according to claim 7, an excitation drive circuit for applying a drive AC signal to the drive signal input electrode to bend and vibrate the piezoelectric vibrator in a width direction, and the pair of Coriolis A piezoelectric vibration angular velocity meter comprising: a Coriolis signal detection circuit that detects a difference between output signals from signal detection and feedback electrodes to detect a Coriolis signal. 9. A drive signal input electrode and feedback electrode that extends parallel to the longitudinal axis and is separated in the width direction on a side surface of the two opposing side surfaces on which the polarization in the width direction is dominant. A reference electrode and a feedback electrode / drive reference electrode are formed, and of the two opposing side surfaces, the side surface on the side where the polarization in the thickness direction is dominant extends parallel to the longitudinal axis and in the width direction. A pair of symmetric Coriolis signal detection electrodes are formed apart from each other, and a Coriolis detection reference electrode extending in the center in the width direction parallel to the longitudinal axis is formed between the pair of Coriolis signal detection electrodes. The piezoelectric vibrator according to claim 1, wherein: 10. A piezoelectric vibrator according to claim 9, and an excitation drive circuit for applying a drive AC signal to a drive signal input electrode and a feedback reference electrode to cause the piezoelectric vibrator to flexurally vibrate in a thickness direction. And a Coriolis signal detection circuit for detecting a difference between output signals from the pair of Coriolis signal detection electrodes to detect a Coriolis signal. 11. A pair of Coriolis signal detection electrodes extending parallel to the longitudinal axis and symmetric in the width direction are separated from the two opposing side surfaces on the side where the polarization in the width direction is dominant. A Coriolis detection reference electrode is formed and extends in the center in the width direction in parallel with the longitudinal axis between the pair of Coriolis signal detection electrodes, and the polarization in the thickness direction of the two opposing side surfaces is formed. On the side of the dominant side, a drive signal input electrode / feedback reference electrode and a feedback electrode / drive reference electrode extending in parallel with the longitudinal axis and spaced apart in the width direction. The piezoelectric vibrator according to claim 1, wherein: 12. A piezoelectric vibrator according to claim 11, an excitation drive circuit for applying a drive AC signal to a drive signal input electrode and a feedback reference electrode to cause the piezoelectric vibrator to flexurally vibrate in the width direction. And a Coriolis signal detection circuit for detecting a difference between output signals from the pair of Coriolis signal detection electrodes to detect a Coriolis signal.