JP3356012B2 - Vibrating gyro - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibrating gyroscope, and more particularly to a vibrating gyroscope for detecting an angular velocity for performing, for example, camera shake correction, a car navigation system, and vehicle attitude control.

[0002]

2. Description of the Related Art FIG. 9 is a perspective view showing an example of a conventional vibrating gyroscope. This vibrating gyroscope 1 includes two quadrangular prism-shaped piezoelectric bodies 2. These piezoelectric bodies 2 are stacked via the intermediate electrode 3 to form a bimorph vibrator. An electrode 4 is formed on the entire surface of one surface of one of the stacked piezoelectric bodies 2. Two split electrodes 5a and 5b extending in the longitudinal direction are formed on the surface of the other piezoelectric body 2 that is stacked. The two piezoelectric bodies 2 are polarized in opposite directions between the intermediate electrode 3 and the electrode 4 and between the intermediate electrode 3 and the divided electrodes 5a and 5b.

In the vibrating gyroscope 1, as shown in FIG. 10, an oscillation circuit 6 is connected between the electrode 4 and the intermediate electrodes 5a and 5b. Oscillation circuit 6 includes, for example, an amplification circuit and a phase correction circuit, and the output signal of electrode 4 is amplified and the phase is corrected. The drive signal thus obtained is applied to the divided electrodes 5a and 5b, and the bimorph vibrator bends and vibrates in a direction orthogonal to the surface on which the electrode 4 is formed and the surface on which the divided electrodes 5a and 5b are formed.

Further, the divided electrodes 5a and 5b are connected to a detection circuit 7. The detection circuit 7 includes, for example, a differential circuit, a synchronous detection circuit, a smoothing circuit, an amplification circuit, and the like. During non-rotation, the bimorph vibrator bends and vibrates in a direction perpendicular to the surfaces on which the divided electrodes 5a and 5b are formed.
The same signal is output from the divided electrodes 5a and 5b, with no difference in the bending state of the piezoelectric body 2 at the portions where the piezoelectric elements 2a and 5b are formed. When the bimorph vibrator rotates about its axis, the direction of vibration of the bimorph vibrator changes due to Coriolis force. For this reason, a difference occurs in the bending state of the piezoelectric body 2 in a portion where the divided electrodes 5a and 5b are formed, and thus a difference occurs in signals output from the divided electrodes 5a and 5b. The difference between the output signals corresponds to a change in the vibration direction of the bimorph vibrator, and the change in the vibration direction of the bimorph vibrator corresponds to the magnitude of the Coriolis force. Therefore, the difference between the output signals of the divided electrodes 5a and 5b is calculated,
By performing detection, smoothing, and amplification, a DC signal corresponding to the rotational angular velocity can be obtained.

[0005] Further, an energy trap type vibrator,
There is also a vibration gyro that detects a rotational angular velocity by detecting a Coriolis force acting on these vibrations using a vibrator using surface acoustic waves.

[0006]

Generally, a Coriolis force Fc generated when a material point having a single vibration rotates.
Is represented by the following equation. Fc = −2 mvΩ where m is mass, v is vibration velocity, and Ω is angular velocity. In a conventional vibrating gyroscope as shown in FIG. 9, displacement of a vibrator due to Coriolis force is detected by electric charges generated on a detection electrode. However, when the size of the vibrator is reduced, the mass m and the vibration velocity v in the above equation are reduced, and the detection sensitivity of the Coriolis force is reduced.
It becomes difficult to accurately detect the rotational angular velocity.

In an energy confinement type vibrating gyroscope or a vibrating gyroscope using a surface acoustic wave, the amplitude is very small and the vibration speed is very small. Therefore, the Coriolis force acting on the vibration wave is very small, and it is difficult to detect the rotational angular velocity from the change in the vibration.

Therefore, a main object of the present invention is to provide a vibrating gyroscope that can be downsized and that can detect a rotational angular velocity with high sensitivity.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a bimorph vibrator in which a plurality of columnar piezoelectric members are stacked, a primary electrode formed on both sides of the bimorph vibrator for exciting bending vibration to the bimorph vibrator. And two pairs of secondary electrodes formed on opposing portions of the bimorph vibrator on both sides of the bimorph vibrator, and two energy confining resonators are formed by the two pairs of secondary electrodes and the piezoelectric body. And a vibrating gyroscope in which the energy trap type resonator is arranged symmetrically with respect to the center line in the width direction of the bimorph vibrator. Further, the present invention provides a bimorph vibrator in which a plurality of columnar piezoelectric bodies are stacked, a primary electrode formed on both sides of the bimorph vibrator to excite bending vibration in the bimorph vibrator; One of the two includes two pairs of comb-shaped electrodes formed side by side in the width direction of the bimorph vibrator, and the two pairs of comb-shaped electrodes and the piezoelectric material form two surface acoustic wave resonators, This is a vibrating gyroscope in which the resonator is arranged symmetrically with respect to the center line in the width direction of the bimorph vibrator.

[0010] By causing the bimorph vibrator to bend and vibrate, Coriolis force is applied to the vibrating body when a rotational angular velocity is applied. Due to this Coriolis force, the direction of vibration of the bimorph vibrator is changed, and opposite stress is applied to a portion where two energy trapping type resonators are formed or a portion where two comb electrodes are formed. Therefore, a difference occurs in the resonance characteristics of the two energy trap type resonators, or a difference occurs in the resonance characteristics of the two surface acoustic wave resonators. Accordingly, a difference occurs between the output signals of the two energy trap type resonators or the output signals of the two surface acoustic wave resonators in accordance with the change in the vibration direction of the bimorph resonator. From the difference between these output signals, a signal corresponding to the rotational angular velocity can be obtained.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0012]

1 is a perspective view showing an example of a vibrating gyroscope according to the present invention, FIG. 2 is a sectional view taken along line II-II in FIG. 1, and FIG. 3 is a line III-III in FIG. FIG. The vibrating gyroscope 10 includes a bimorph vibrator 12. The bimorph oscillator 12 has two 4
It includes prismatic piezoelectric bodies 14 and 16. These piezoelectric bodies 1
4 and 16 are laminated via the intermediate electrode 18. The primary electrode 20 is placed on both surfaces of the bimorph vibrator 12, that is, on the surfaces of the piezoelectric bodies 14 and 16 so as to face the intermediate electrode 18.
a, 20b are formed.

On one surface of the bimorph vibrator 12, there are two portions where the primary electrode 20a is not formed at the center in the longitudinal direction. Except for these portions, the primary electrode 20 a is formed on the entire surface of one surface of the bimorph vibrator 12. Then, for example, in a portion where the primary electrode 20a is not formed, a circular secondary electrode 22a,
24a are formed. These secondary electrodes 22a, 24a
Are arranged symmetrically with respect to a center line extending in the longitudinal direction of one surface of the bimorph vibrator 12.

Further, on the other surface of the bimorph vibrator 12, a primary electrode 20b
Are not formed. Except for these parts, the primary electrode 20b is connected to the bimorph oscillator 12
Is formed on the entire surface of the other surface of the substrate. And the primary electrode 20b
Are formed, for example, in a circular secondary electrode 2
2b and 24b are formed. These secondary electrodes 22b,
Reference numeral 24b is arranged symmetrically with respect to a center line extending in the longitudinal direction of the other surface of the bimorph vibrator 12.

Therefore, the secondary electrodes 22a and 22b formed on both surfaces of the bimorph vibrator 12 are formed at positions facing each other. Similarly, the secondary electrodes 24a and 24b formed on both surfaces of the bimorph vibrator 12 are formed at positions facing each other. Further, the intermediate electrode 1 is provided between the two piezoelectric bodies 14 and 16.
8 is a portion facing the secondary electrodes 22a and 22b and 2
It is formed on the entire surface except for the portion facing the next electrodes 24a and 24b.

The two piezoelectric members 14 and 16 are polarized in directions opposite to each other. For example, when the piezoelectric body 14 is polarized from the intermediate electrode 18 side toward one primary electrode 20a, the piezoelectric body 16 is polarized from the intermediate electrode 18 side to the other primary electrode 2a.
Polarized toward the 0b side. However, between the secondary electrodes 22a and 22b and between the secondary electrodes 24a and 24b, the two piezoelectric bodies 14 and 16 are polarized in the same direction. In order to perform such polarization, the piezoelectric bodies 14 and 16 polarized in opposite directions are stacked, and then the secondary electrodes 22a and 22a are stacked.
b and between the secondary electrodes 24a and 24b. The piezoelectric bodies 14 and 16 and the secondary electrodes 22a and 22b form an energy trap type resonator. Similarly, an energy trap type resonator is formed by the piezoelectric bodies 14 and 16 and the secondary electrodes 24a and 24b. Therefore, the vibration gyro 10
In this configuration, two energy trap type resonators are arranged at the center of the bimorph resonator in the width direction.

In order to use this vibrating gyroscope 10,
A circuit as shown in FIG. 4 is used. The intermediate electrode 18
Connected to reference potential. Also, the primary electrodes 20a, 20b
Are connected to the first drive circuit 30. In the first driving circuit 30, a driving signal for causing the bimorph vibrator 12 to bend and vibrate is generated. This drive signal is applied to one primary electrode 20a and to the other primary electrode 20b via an inversion circuit 32. Therefore, 2
The drive signals of opposite phases are given to one primary electrode 20a, 20b. Since the two piezoelectric members 14 and 16 are polarized in directions opposite to each other, the bimorph vibrator 12 is oriented in a direction orthogonal to the surface on which the primary electrode 20a and the surface on which the primary electrode 20b is formed by supplying drive signals having opposite phases. Bending vibration.

Further, a second drive circuit 34 is connected to the secondary electrodes 22a and 24a. From the second drive circuit 34, a drive signal for exciting the two energy trap type resonators is provided. Further, the secondary electrodes 22b,
24b is connected to the detection circuit 40. The detection circuit 40 includes a differential circuit 42 and outputs a difference between output signals of the secondary electrodes 22b and 24b. The differential circuit 42 is connected to a rectifier circuit 44, and an output signal of the rectifier circuit 44 is supplied to a first smoothing circuit 46.
Is smoothed. The DC component of the output signal of the first smoothing circuit 46 is removed by a DC component removal circuit 48, and the output signal is detected by a synchronous detection circuit 50 in synchronization with the signal of the inversion circuit 32. The output signal of the synchronous detection circuit 50 is supplied to a second smoothing circuit 52.
, And is amplified by the amplifier circuit 54.

The second driving circuit 34 causes the secondary electrode 2
Energy trapping vibration is excited in the energy trapping type resonator formed by the piezoelectric members 14 and 16 and the energy trapping type resonator formed by the secondary electrodes 24a and 24b and the piezoelectric members 14 and 16. You. This energy confinement vibration is a vibration generated only between the secondary electrodes 22a and 22b and between the secondary electrodes 24a and 24b, and has a higher frequency than the bending vibration of the bimorph vibrator 12.

When the bimorph vibrator 12 bends and vibrates, the portion where the energy trap type resonator is formed also bends, and its resonance transmission characteristic changes according to the bending state. Therefore, as shown in FIGS. 5A and 5B, the vibration waveform of the bimorph vibrator is superimposed on the vibration waveform of the energy trap type resonator, and an amplitude-modulated signal is output. At the time of non-rotation, the bending states of the two energy trapping type resonators are the same, so that a signal having the same waveform is input to the differential circuit 42. Therefore, FIG.
As shown in (c), no signal is output from the differential circuit 42, and it can be seen that the rotational angular velocity is not applied.

When the bimorph vibrator 12 rotates about its axis, Coriolis force acts in a direction orthogonal to the direction of the bending vibration. This Coriolis force causes the bimorph oscillator 12
Is displaced, and the direction of the bending vibration of the bimorph vibrator 12 changes. At this time, since the vibration speed of the energy trap type resonator is very low, Coriolis force hardly occurs with respect to the vibration of the energy trap type resonator. Due to the displacement of the bimorph vibrator 12, stress is applied to the two energy trap type resonators, the resonance transfer characteristics thereof change, and the waveforms of the output signals of the secondary electrodes 24a and 24b change. The stresses applied to the two energy trapping type resonators are in opposite directions, and the waveform changes of the signals output from the secondary electrodes 24a and 24b are also opposite. As a result, FIG.
As shown in (a) and (b), a difference in amplitude occurs between the output signals of the two energy trap type resonators. Therefore, as shown in FIG.
A signal having an amplitude corresponding to the difference between the amplitudes of the two input signals is output. Further, as shown in FIG. 6D, in the rectifier circuit 44, for example, only the positive portion of the output signal of the differential circuit 42 is output.

As shown in FIG. 6 (e), the output signal of the rectifier circuit 44 has a high frequency component removed by a first smoothing circuit 46. Further, as shown in FIG. 6F, a signal corresponding to a change in the bending vibration of the bimorph vibrator 12 is obtained by removing the DC component in the DC component removing circuit 48. This signal is output to the inversion circuit 3 by the synchronous detection circuit 50.
The signal is detected in synchronization with the signal No. 2 and only the positive portion of the signal is output, for example, as shown in FIG. Therefore, if this signal is smoothed by the second smoothing circuit 52 and further amplified by the amplifier circuit 54, a DC signal corresponding to the Coriolis force can be obtained.

Further, as shown in FIG. 7, the rotational angular velocity can be detected from the change in the resonance frequency characteristic of the energy trap type resonator. In this case, the primary electrodes 20a,
The first oscillation circuit 60 is connected between 20b. First
The oscillation circuit 60 includes an amplification circuit 62 and a phase correction circuit 64, and outputs an output signal from the primary electrode 20b to the amplification circuit 62.
Is input to The signal amplified by the amplifier circuit 62 is phase-corrected by the phase correction circuit 64, and is input to the primary electrode 20a as a drive signal. Thereby, the bimorph vibrator 12 bends and vibrates in a direction orthogonal to the primary electrode 20a forming surface and the primary electrode 20b forming surface.

Further, a second oscillation circuit 66 is connected between the secondary electrodes 22a and 22b, and the secondary electrodes 24a and 24b
A third oscillation circuit 68 is connected between them. By these oscillation circuits 66 and 68, energy confinement vibration is excited in the two energy confinement type resonators. Further, the secondary electrodes 22a and 24a are connected to the detection circuit 70. The detection circuit 70 includes a frequency difference detection circuit 72.
The frequency difference detection circuit 72 is a circuit that outputs a voltage corresponding to the frequency difference between two input signals. The output signal of the frequency difference detection circuit 72 is detected by the synchronous detection circuit 74 in synchronization with the output signal of the primary electrode 20b. The signal detected by the synchronous detection circuit 74 is smoothed by the smoothing circuit 76 and further amplified by the amplifier circuit 78.

A vibrating gyroscope 10 using such a circuit
In the case of (2), the output signal of the energy trap type resonator is a signal whose frequency is modulated in accordance with the bending vibration of the bimorph vibrator 12. That is, the signal has a high frequency portion and a low frequency portion alternately appearing in response to the bending vibration of the bimorph vibrator 12. At the time of non-rotation, 2
Since the two energy confining resonators are in the same bending state, signals having the same frequency characteristics are output from the secondary electrodes 22a and 24a. Therefore, no signal is output from the frequency difference detection circuit 72.

When the bimorph vibrator 12 rotates about its axis, the direction of the bending vibration changes due to the Coriolis force, and opposite stresses are applied to the two energy trap type resonators. Thereby, the resonance frequency characteristic of the energy trap type resonator changes, and the frequency of the two output signals changes. At this time, since the stresses applied to the two energy trap type resonators are in opposite directions, the frequency changes of the output signals are also reversed, and a frequency difference occurs between these output signals. Therefore, the frequency difference detection circuit 7 of the detection circuit 70
From 2, a voltage corresponding to the frequency difference between the output signals of the secondary electrodes 22a and 24a is output. This frequency difference detection circuit 7
2 is detected in the synchronous detection circuit 74 in synchronization with the output signal of the primary electrode 20b. The detected signal is smoothed by the smoothing circuit 76 and further amplified by the amplifier circuit 78 to obtain a DC signal corresponding to the Coriolis force.

Further, as shown in FIG. 8, a vibrating gyroscope using a surface acoustic wave may be used. This vibrating gyro 1
0, the bimorph vibrator 12 composed of the piezoelectric bodies 14, 16 and the intermediate electrode 18 and the primary electrodes 20a, 20b
Two comb-shaped electrodes 80a and 80b are formed. These comb electrodes 80a and 80b are connected to the bimorph vibrator 1
In the central part in the longitudinal direction of the bimorph vibrator 12
Are formed side by side in the width direction. The comb-shaped electrode 80a is formed by a common electrode 82a and input / output electrodes 84a and 86a. Then, the piezoelectric body 14 is polarized between the common electrode 82a and the input / output electrode 84a, and the piezoelectric body 14 is polarized between the common electrode 82a and the input / output electrode 86a. Similarly,
The comb-shaped electrode 80b includes a common electrode 82b and an input / output electrode 84.
b, 86b. The piezoelectric body 14 is polarized between the common electrode 82b and the input / output electrode 84b, and the piezoelectric body 14 is placed between the common electrode 82b and the input / output electrode 86b.
Is polarized. These interdigital electrodes 80a and the piezoelectric body 14
Thus, a surface acoustic wave resonator is formed, and the comb-shaped electrode 80b and the piezoelectric body 14 form a surface acoustic wave resonator. In addition,
The intermediate electrode 18 is formed on the entire surface of one side of the piezoelectric bodies 14 and 16 between the piezoelectric bodies 14 and 16. Also,
The primary electrode 20 b is formed on the entire surface of another one side of the piezoelectric body 16.

In order to use the vibrating gyroscope 10,
An oscillation circuit 60 including an amplification circuit 62 and a phase correction circuit 64 is connected between the primary electrodes 20a and 20b. The oscillation circuit 60 excites the bending vibration of the bimorph vibrator 12. Further, the common electrodes 82a and 82b of the comb electrodes 80a and 80b are connected to a reference potential. Then, a drive circuit 90 is connected to the input / output electrodes 84a and 84b, and a surface acoustic wave is excited by the drive signal.
The excited surface acoustic wave propagates through the piezoelectric body 14 and is converted into an electric signal by the input / output electrodes 86a and 86b. And
The signals output from the input / output electrodes 86a and 86b are input to the detection circuit 40.

The detection is performed by detecting a change in the output signal due to a change in the resonance transfer characteristic of the surface acoustic wave resonator in the same manner as in FIGS. FIG.
In FIG. 6 and FIG. 6, the output signal of the energy trap type resonator is processed by the detection circuit 40. However, here, the output signal of the surface acoustic wave resonator is processed by the detection circuit 40, so that the rotation applied to the vibration gyro 10 is controlled. An angular velocity is detected.

As described above, the vibration gyro 10 of the present invention
Instead of using the piezoelectric characteristics of a piezoelectric element to detect the rotational angular velocity as in conventional vibrating gyros, the rotational angular velocity must be detected using the resonance characteristics of an energy trap type resonator or surface acoustic wave resonator. Can be. Since the resonance characteristics of these resonators are greatly affected by the stress caused by the change in the vibration direction of the bimorph vibrator 12, even if the generated Coriolis force is small, the rotational angular velocity can be detected with extremely high sensitivity. . Therefore, the bimorph oscillator 1
Even if 2 is downsized, the rotational angular velocity can be detected with high sensitivity.

[0031]

According to the present invention, since the rotational angular velocity can be detected by using the resonance characteristics of the energy trap type resonator and the surface acoustic wave resonator, even if the generated Coriolis force is small, it can be very small. The rotational angular velocity can be detected with high sensitivity. In addition, since the rotational angular velocity detection sensitivity is high, the size of the vibrating gyroscope can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a vibrating gyroscope according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a sectional view taken along line III-III in FIG. 1;

FIG. 4 is a block diagram showing a circuit for using the vibrating gyroscope shown in FIG. 1;

5 is a graph showing a signal waveform of each circuit when the circuit shown in FIG. 4 is not rotating.

6 is a graph showing a signal waveform of each circuit when the circuit shown in FIG. 4 rotates.

FIG. 7 is a block diagram showing another circuit for using the vibration gyro shown in FIG. 1;

FIG. 8 is a perspective view of a vibrating gyroscope using a surface acoustic wave and a block diagram showing a circuit for using the same.

FIG. 9 is a perspective view showing an example of a conventional vibrating gyroscope.

FIG. 10 is a block diagram showing a circuit for using the conventional vibrating gyroscope shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Vibration gyroscope 12 Bimorph vibrator 14 Piezoelectric body 16 Piezoelectric body 18 Intermediate electrode 20a, 20b Primary electrode 22a, 22b, 24a, 24b Secondary electrode 80a, 80b Comb-shaped electrode 82a, 82b Common electrode 84a, 84b, 86a, 86b I / O electrode

Continued on the front page (72) Inventor Akira Kumanda 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Co., Ltd. Inside Murata Manufacturing Co., Ltd. (72) Inventor Yoshio Kawaai 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto In Murata Manufacturing Co., Ltd. (72) Inventor Jiro Miyazaki 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Incorporated Murata Manufacturing Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) G01C 19 / 56 G01P 9/04

Claims (2)

(57) [Claims] 1. A bimorph vibrator in which a plurality of columnar piezoelectric bodies are stacked, a primary electrode formed on both sides of the bimorph vibrator to excite bending vibration in the bimorph vibrator, and the bimorph vibrator A pair of secondary electrodes formed at opposing portions of the bimorph vibrator on the both surfaces of the two electrodes, wherein the two pairs of secondary electrodes and the piezoelectric body form two energy trapping resonators, A vibrating gyroscope in which an energy trap type resonator is arranged symmetrically with respect to a center line in a width direction of the bimorph vibrator. 2. A bimorph vibrator in which a plurality of columnar piezoelectric bodies are stacked, a primary electrode formed on both surfaces of the bimorph vibrator for exciting bending vibration to the bimorph vibrator, and the bimorph vibrator And two pairs of comb-shaped electrodes formed side by side in the width direction of the bimorph vibrator on one of the two surfaces, and two surface acoustic wave resonators are formed by the two pairs of comb-shaped electrodes and the piezoelectric body. A vibrating gyroscope, wherein the surface acoustic wave resonator is arranged symmetrically with respect to a center line in a width direction of the bimorph vibrator.