JP3398853B2 - Energy Confinement Type Piezoelectric Vibratory Gyroscope - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gyroscope for detecting a rotational angular velocity, and more particularly to a piezoelectric vibrating gyroscope utilizing an energy trapping vibration mode of a piezoelectric vibrator.

[0002]

2. Description of the Related Art A piezoelectric vibrating gyroscope (hereinafter referred to as a piezoelectric vibrating gyro for the sake of simplicity) is a state in which a piezoelectric vibrator is excited in a certain direction and then the piezoelectric vibrator vibrates in a direction perpendicular to the exciting direction. It detects the Coriolis force generated in the direction of excitation and the direction perpendicular to the rotation axis when it is rotated around the axis of, and detects the angular velocity of rotation. Recently, there are various applications. Are being used for such as a navigation system and a camera shake correction mechanism of a VTR camera.

As a piezoelectric vibrating gyro, for example, a piezoelectric vibrating gyro utilizing an energy trapping vibration mode using a piezoelectric vibrator that vibrates in an energy trapping vibration mode in which vibration energy is concentrated in the vicinity of a drive electrode is disclosed in, for example, Japanese Patent Laid-Open No. 2004-242242 62-162915 and JP-A-5-3225.
No. 80 is proposed.

In the piezoelectric vibrating gyro using the energy trapping vibration mode, since the vibration energy is concentrated on the local portion of the piezoelectric vibrator, it is easy and easy to support the piezoelectric vibrator, and a free lead wire is unnecessary. There are advantages.

In Japanese Patent Laid-Open No. 62-162915, in order to confine vibration energy locally, the thickness of the vibrator is locally thickened, and that portion is polarized in the thickness direction, and drive electrodes are provided on the opposite end faces of the thick local area. It is disclosed that a detection electrode is provided on the opposite side surface. Further, as another example, a drive electrode and a detection electrode are provided on one surface of a piezoelectric plate, and an interdigital electrode is provided between the drive electrodes as a detection electrode.

Japanese Unexamined Patent Publication (Kokai) No. 5-322580 discloses that a partial region of a piezoelectric plate is polarized in the thickness direction, and 2 is formed on the main surface of the polarized region.
Disclosed is a piezoelectric vibrating gyro in which a pair of counter electrodes are provided with their facing directions at right angles, one counter electrode serving as a drive electrode, and the other counter electrode serving as a detection electrode.

[0007]

Problems to be Solved by the Invention JP-A-62-1629
The piezoelectric vibrating gyro utilizing the energy trapping vibration mode disclosed in No. 15 has manufacturing difficulties such that the thickness of the piezoelectric plate must be locally increased or the interdigital electrodes must be formed. Further, since the pair of drive electrodes and the pair of detection electrodes are provided in the vicinity of each other, the drive electric field applied from the drive electrodes into the piezoelectric plate is affected by the detection electrodes, and the drive electric field direction changes to obtain accuracy. There is a defect that it does not exist.

The piezoelectric vibrating gyro using the energy trapping vibration mode disclosed in JP-A-5-322580 has a simple structure and is easy to manufacture, but a pair of drive electrodes and a pair of detection electrodes are provided in the vicinity of each other. Because
The drive electric field applied from the drive electrode to the piezoelectric plate is affected by the detection electrode, the direction of the drive electric field is changed, and it is difficult to obtain an accurate detection output.

Therefore, it is an object of the present invention to provide a piezoelectric vibrating gyro which uses a small-sized, simple structure and manufacturing, and highly accurate energy trapping vibration mode.

According to the present invention, by sharing the output electrode with a part of the drive electrode in a limited area of the main surface of the piezoelectric plate,
An object of the present invention is to provide a piezoelectric vibrating gyro using an energy trapping vibration mode in which an output electrode does not adversely affect a driving electric field.

[0011]

SUMMARY OF THE INVENTION The present invention is a piezoelectric vibrating gyroscope that is excited in one direction along the plane of a piezoelectric plate and detects the vibration due to the Coriolis force generated by the rotation of the piezoelectric plate to detect the angular velocity of rotation. In the main surface of the portion having polarization in the thickness direction of the piezoelectric plate, and in one of two positions spaced apart from each other by a predetermined distance in the excitation direction, one of the positions is strip-shaped in a direction perpendicular to the excitation direction. A strip-shaped second electrode is provided which is provided with the first electrode and extends at the other position at a distance from each other in a direction substantially perpendicular to the excitation direction.
And a third electrode, and the second electrode and the third electrode have strip-shaped small protrusions extending in the excitation direction at the opposing adjacent ends thereof. The length of the facing side is increased, and a drive voltage for excitation is applied between the first electrode and the second and third electrodes to cause the second electrode
And an electromotive force corresponding to the vibration due to the Coriolis force generated in the third electric field is detected, and the energy trapping mode of the thickness shear vibration generated between the first electrode and the second and third electrodes is detected. It is an energy trap type piezoelectric vibrating gyroscope characterized by being used.

According to one aspect of the present invention, the strip-shaped small protrusions of the second and third electrodes extend in a direction approaching the first electrode, and the first electrode is It is preferable that both ends have convex portions extending in a direction approaching the second and third electrodes.

In the piezoelectric vibrating gyroscope of the present invention, the second and third electrodes are respectively connected to first and second current detection circuits having a virtual ground function,
A drive voltage for excitation is applied to the first electrode,
And the detection output is obtained from the difference voltage generated between the outputs of the second current detection circuit.

The piezoelectric vibrating gyroscope of the present invention is, as a drive and detection circuit, connected between the outputs of the first and second current detection circuits to detect a difference between the output voltages of the both current detection circuits. Drive circuit, a synchronous detection circuit connected to the output of the differential circuit, a rectification circuit connected to the output of the synchronous detection circuit, and a self-excited drive connected between the outputs of the first and second current detection circuits. It is preferable to include an oscillating circuit for oscillating a signal of a driving frequency, and a driving circuit connected to the output of the oscillating circuit and applying an AC voltage of the self-exciting driving frequency to the first electrode.

As the piezoelectric plate, piezoelectric ceramics are used, and only the regions between the first to third electrodes of the piezoelectric ceramics and in the vicinity thereof are polarized in the thickness direction.

A piezoelectric crystal plate having a polarization axis in the thickness direction may be used as the piezoelectric plate.

[0017]

FIG. 1 is a perspective view showing the configuration of a vibrator of an energy-entrapment type vibrating gyroscope according to an embodiment of the present invention. As shown in FIG. 1, the piezoelectric vibrator
For example, the piezoelectric plate 10 having a polarization axis in the thickness direction at the central portion, which is made of a piezoelectric ceramic plate such as PZT or barium titanate, is used. A strip-shaped first electrode 11 is provided on the main surface of the central portion of the piezoelectric plate 10. A second electrode 12 and a third electrode 13 are formed apart from each other in parallel with the first electrode 11 at a position separated from the first electrode 11 by a predetermined distance.

The second and third electrodes have strip-shaped small projections 12a and 13a extending in the direction of approaching the first electrode 11 at their opposing adjacent ends.
This increases the length of the opposing sides of the second and third electrodes. Corresponding to this, the first electrode is
At both ends thereof, convex portions 11a and 11b extending in a direction approaching the second and third electrodes are provided. These protrusions 11a and 11b are for compensating for the irregularity of the distance between the first electrode and the second and third electrodes due to the presence of the small protrusions 12a and 13a. Therefore, these convex portions 11a and 11b are not necessarily required and need not be formed.

Strip-shaped small protrusions 12a and 13a
Since the purpose is to increase the length of the opposing sides of the second and third electrodes, the extending directions may be the opposite directions, that is, the directions away from the first electrode. In this case,
The convex portions 11a and 11b of the first electrode are completely unnecessary. The strip-shaped small protrusions 12a and 13a may extend in both directions away from and approaching the first electrode.

Terminals 14, 15 and 16 for connecting the electrodes 11, 12 and 13 to the outside are connected to the electrodes 11, 12 and 13, respectively. It should be noted that these electrodes and terminals may be made of silver paste or gold sputter. Of course, other conductive films can be adopted. The lead wire may be used without providing the terminal portion for leading to the outside on the vibrator.

As shown in the figure, three-dimensional coordinates are determined with the Z direction as the thickness direction, the X axis as the facing direction of the electrodes, and the Y axis as the direction orthogonal to these.

When a driving voltage (AC) is applied between the first electrode 11 and the second and third electrodes, vibration in the X direction is excited. In this state, when the piezoelectric plate 10 rotates around the Z axis, vibration due to the Coriolis force is generated in the Y direction, which causes electromotive force between the second and third electrodes. By detecting this electromotive force, the magnitude of vibration due to the Coriolis force, and thus the rotational angular velocity, can be detected.

Since the vibration energy is confined in the central part of the piezoelectric plate and does not reach the periphery, it is easy to support the peripheral part of the piezoelectric plate.

FIG. 2 is a block diagram showing a circuit configuration connected to the piezoelectric vibrator 1 of FIG. Referring to FIG.
In the second and third electrodes 12 and 13 of the piezoelectric vibrator 1,
The current detection circuits 18 and 19 are respectively connected. A differential amplifier circuit 22 is provided on the output side of the current detection circuits 18 and 19.
Are connected, and the detection output of the piezoelectric vibration gyro is obtained via the synchronous detection circuit 23 and the rectification circuit 24. On the other hand, the current detection circuits 18 and 19 are connected to the oscillation circuit 25 for satisfying the self-excited oscillation condition, and are connected to the first electrode 11 via the drive circuit 26 for giving the X-direction vibration. It constitutes an oscillator circuit. By this self-excited oscillation circuit, an AC voltage having a frequency substantially equal to the resonance frequency of the thickness shear vibration of the piezoelectric vibrator is applied to the electrode 11.

FIG. 3 is a diagram showing a configuration example of the current detection circuits 18 and 19 of FIG. 2, which has a function of virtually grounding the second and third electrodes 12 and 13. In this circuit, the non-inverting input terminal (+) of the operational amplifier 31 is grounded to the reference voltage, and the resistor R is connected from the output terminal of the operational amplifier 31 to the inverting input terminal. The inverting input terminal (-) is always kept at the ground reference potential by the virtual ground function of the operational amplifier. When a current flows into this inverting terminal, it is converted into a voltage by the resistor R. That is, V
An output of out = -iR is obtained. That is, this current detection circuit functionally has an input impedance of almost 0,
It is a circuit that can obtain an output voltage proportional to the input current.

This current detection circuit is replaced with the current detection circuit 1 shown in FIG.
Used for 8 and 19. At that time, the inverting input terminal (−) is connected to the second and third electrodes 12 and 13. As a result, the driving voltage is applied to the first electrode 11 and the second and third electrodes 11.
Between the electrodes 12 and 13 of the
And the electromotive force between the third electrodes 12 and 13 can be detected as a potential difference between the outputs of the current detection circuits 18 and 19.

At this time, since the opposing sides of the second electrode and the third electrode are long due to the existence of the small protrusions 12a and 13a, detection is performed as compared with the case without these small protrusions. Large output can be obtained.

Next, the driving principle of the piezoelectric vibrator according to the above-described embodiment of the present invention will be specifically described with reference to the drawings.

FIGS. 4A and 4B show FIGS.
FIG. 3 is a plan view showing a basic structure of the energy trap type vibrator shown in FIG. 4 and a sectional view showing only an electrode portion.
Referring to FIGS. 4A and 4B, X is formed on the same plane of the central portion of the piezoelectric plate 10 polarized in the thickness direction (Z-axis direction).
Slit-shaped electrodes D1 and D2 are formed facing each other with a gap in the axial direction. Note that T1 and T2 are terminal portions. When a voltage is applied between the terminals T1 and T2, an electric field in a direction substantially parallel to the plane of the plate (X direction) is applied to the region (inter-electrode region) of the piezoelectric plate 10 between the opposing electrodes D1 and D2. Therefore, the interaction between the electric field and the polarization in the thickness direction (Z-axis direction) orthogonal to the electric field causes strain in the inter-electrode region in the X direction. Electrode D1,
If the dimension of D2 is designed according to the characteristics of the piezoelectric plate 10 and the applied voltage is an AC voltage having a frequency matching the resonance frequency of the inter-electrode region, thickness shear vibration can be excited in the inter-electrode region. The vibration is attenuated around the inter-electrode region and is trapped without propagating. That is, an energy trap oscillator can be configured. Also, this vibration is
Since it is a thickness shear vibration caused by an electric field parallel to the surface of the piezoelectric plate, it is called a parallel electric field excitation type thickness shear vibration. The thickness shear vibration is vibration in which the displacement direction of the piezoelectric plate is parallel to the plate surface and the wave propagation direction is in the plate thickness direction. In order to illustrate the state of this vibration, FIG. 5 shows a displacement distribution in the thickness direction (Z-axis direction) when resonating at a half wavelength.

The vibrator of FIGS. 1 and 2 utilizes the above basic structure. That is, the first electrode 11 is D
The second electrode 12 and the third electrode 13 which are one electrode and are opposed thereto are the D2 electrode. The D2 electrode is divided into two to form a detection electrode to form a second electrode 12 and a third electrode 13, which are connected to current detection circuits 18 and 19 having a virtual ground function, respectively. As a result, the second electrode 12 and the third electrode 13 are virtually maintained at the reference potential, and thus can be regarded as potential ground terminals. Therefore, when a drive voltage for excitation having a frequency substantially equal to the resonance frequency of the thickness shear vibration mode of the piezoelectric plate is applied to the first electrode 11, the first, second, and In the area (inter-electrode area) surrounded by the third electrodes 11, 12 and 13, the center of the first electrode 11 and the second and third electrodes 12 and 1 are formed.
Direction of the line connecting the midpoints of the lines connecting the centers of 3 (X direction)
Thickness shear vibration of the energy trapping vibration mode of is generated.

In this state, when the piezoelectric plate 10 is rotated around an axis orthogonal to its main surface, due to the action of the Coriolis force, the direction (Y) perpendicular to the direction of the thickness shear vibration being excited. Direction) thickness-shear vibration occurs. Due to the thickness shear vibration generated by this Coriolis force, the first
Between the electrode 11 and the second electrode 12 of the first electrode 1
The impedance between 1 and the third electrode 13 changes,
As a result, the current value flowing into the current detection circuits 18 and 19 changes. Second electrode 12 and third electrode 1
As described above, since 3 is arranged symmetrically with respect to the direction of the thickness-shear vibration being excited (X direction), the current that changes due to the vibration due to the Coriolis force flowing into the current detection circuits 18 and 19 is , Have the same amplitude, 180
The currents have different degrees of phase. Therefore, the current detection circuit 1
The output voltages of 8 and 19 are also 180 degrees out of phase with each other, and the difference between these output voltages is calculated by the differential circuit 2
2 to detect as a differential voltage, the synchronous detection circuit 23 synchronously detects this voltage at a predetermined timing, and the rectifier circuit 24 rectifies it to obtain a DC output voltage proportional to the applied rotational angular velocity as a detection output. Can be done.

On the other hand, the current detection circuits 18 and 19 are connected to the electrode 11 via the oscillation circuit 25 and the drive circuit 26 for satisfying the self-excited oscillation condition and form a self-excited oscillation loop. As a result, the resonance frequency of the vibrator is automatically detected and the vibrator can be efficiently driven, so that a highly sensitive gyro can be obtained.

FIG. 6 shows another circuit configuration.
Electrode 11 is grounded and resistance R is placed between the second and third electrodes.
A voltage dividing circuit composed of a series circuit of 1 and R2 is connected, and the oscillation driving circuit 27 is controlled by the divided voltage. This oscillation drive circuit is grounded, so that a drive voltage is applied between the first electrode 11 and the second and third electrodes. The oscillation drive circuit 27 comprises the oscillation circuit 25 and the drive circuit 26 shown in FIG. Both ends of the voltage dividing circuit are connected to the differential amplifier circuit 22. The differential amplifier circuit 22, the detection circuit 23, and the rectifier circuit 24 are the same as those in FIG.

Here, the piezoelectric plate used in the present invention having "polarization in the thickness direction" is not limited to being polarized only in the thickness direction, but also includes one having a polarization component in the thickness direction. Let's assume. Of course, the larger the polarization component in the thickness direction, the better. Therefore, the one polarized in the thickness direction is the most advantageous.

When piezoelectric ceramics is used as the piezoelectric plate 10, polarization treatment is required as is well known, but the polarization region may be the entire piezoelectric plate or only the region for confining vibration. May be.

As the piezoelectric plate 10, a piezoelectric crystal plate (for example, crystal, LiNbO3, LiTO3, etc.) can be used. In that case, in order to have a polarization axis in the thickness direction, Z
A cut plate is most preferred, but a rotating Y-cut plate can also be used.

[0037]

According to the present invention, driving is performed using only a pair of slit-shaped electrodes arranged in parallel on the main surface of a piezoelectric plate, and one of the pair of electrodes is divided into two. Since the driving electric field is not adversely affected by the presence of the detection electrode, the Y vibration can be detected while maintaining the electric field for exciting the X vibration, and the vibration gyro with high precision and high sensitivity can be detected. Can be obtained. Further, since the energy-entrapped vibration is used, a highly reliable gyro can be obtained.

Further, small protrusions are formed at opposite ends of the detection electrodes in a direction perpendicular to the extending direction of the pair of parallel electrodes,
Since the opposing sides of the detection electrodes are long, the detection output can be increased.

Further, there is no need to locally change the thickness of the piezoelectric plate or to form a complicated electrode structure, and as a vibrator, a pair of parallel electrodes (however, one is The structure and the manufacturing are simple, since it is only necessary to form 2).

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a circuit configuration of a gyro using a piezoelectric vibrator.

3 is a circuit diagram showing an example of a current detection circuit used in the circuit of FIG.

4A and 4B are views showing a basic structure of a vibrator adopted in the piezoelectric vibrator of FIGS. 1 and 2, in which FIG. 4A is a plan view and FIG. 4B is a side view excluding a terminal portion of an electrode.

5 is a diagram showing a displacement distribution in a thickness direction in a thickness shear vibration of a vibrator having the basic structure of FIG.

FIG. 6 is a block diagram showing another circuit configuration of a gyro using a piezoelectric vibrator.

[Explanation of symbols]

1 Piezoelectric vibrator 10 Piezoelectric plate 11 First electrode 12 Second electrode 13 Third electrode 11a, 11b convex part 12a Slit-shaped small protrusion 13a Slit-shaped small protrusion 14, 15, 16 Terminal part 18 Current detection circuit 19 Current detection circuit 22 Differential circuit 23 Synchronous detection circuit 24 Rectifier circuit 25 oscillator circuits 26 Drive circuit 27 Oscillation drive circuit 31 operational amplifier

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-10-148525 (JP, A) JP-A-10-148527 (JP, A) JP-A-10-68625 (JP, A) JP-A-10- 47967 (JP, A) JP-A-5-322580 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01C 19/56 G01P 9/04

Claims (6)

(57) [Claims] 1. Exciting in one direction along a plane of a piezoelectric plate,
In a piezoelectric vibrating gyroscope for detecting a rotation angular velocity by detecting a vibration due to Coriolis force generated by the rotation of the piezoelectric plate, the piezoelectric plate has a substantially central portion on a main surface of a portion having polarization in a thickness direction of the piezoelectric plate. Of the two positions separated from each other by a predetermined distance in the excitation direction, a strip-shaped first electrode is provided at one position in the direction perpendicular to the excitation direction and at the other position in the direction substantially perpendicular to the excitation direction. Forming strip-shaped second and third electrodes extending at a distance from each other, and the second electrode and the third electrode are strip-shaped small protrusions extending in the excitation direction at the ends adjacent to each other. And increasing the length of the opposing sides of the second and third electrodes, applying a drive voltage for excitation between the first electrode and the second and third electrodes, and The colloid generated on the second and third electrodes An electromotive force corresponding to the vibration due to the re-force is detected, and the energy trapping mode of the thickness shear vibration generated between the first electrode and the second and third electrodes is used. Confined piezoelectric vibrating gyroscope. 2. The piezoelectric vibrating gyroscope according to claim 1, wherein the strip-shaped small protrusions of the second and third electrodes extend in a direction approaching the first electrode, and the first electrode The piezoelectric vibrating gyroscope, characterized in that it has, at both ends thereof, convex portions extending in a direction approaching the second and third electrodes. 3. The piezoelectric vibrating gyroscope according to claim 1, wherein the second and third electrodes are connected to first and second current detection circuits having a virtual ground function, respectively. A piezoelectric vibrating gyroscope characterized in that a driving voltage for excitation is applied to one electrode and a detection output is obtained from a difference voltage generated between outputs of the first and second current detection circuits. 4. The piezoelectric vibrating gyroscope according to claim 3, further comprising a differential circuit connected between outputs of the first and second current detection circuits for detecting a difference between output voltages of the both current detection circuits. A synchronous detection circuit connected to the output of the differential circuit, and a rectification circuit connected to the output of the synchronous detection circuit,
An oscillation circuit connected between the outputs of the first and second current detection circuits for oscillating a signal of a self-excitation driving frequency;
A piezoelectric vibrating gyroscope, comprising: a drive circuit connected to an output of the oscillation circuit and applying an AC voltage of the self-excitation driving frequency to the first electrode. 5. The piezoelectric vibrating gyroscope according to claim 1, wherein a piezoelectric ceramic is used as the piezoelectric plate, and only a region between the first to third electrodes of the piezoelectric ceramic and a region in the vicinity thereof. A piezoelectric vibrating gyroscope characterized by being polarized in the thickness direction. 6. The piezoelectric vibrating gyroscope according to any one of claims 1 to 4, wherein a piezoelectric crystal plate having a polarization axis in a thickness direction is used as the piezoelectric plate.