JP3356013B2 - 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. The vibrating gyroscope 1 includes a tuning fork type vibrating body 2. In this vibrating gyroscope 1, a vibrating body 2 is formed by a driving plate 2a and a detecting plate 2b arranged so that their surfaces are orthogonal to each other. The driving piezoelectric element 3 is formed on the driving plate 2a, and the detecting piezoelectric element 4 is formed on the detecting plate 2b. A driving circuit is connected between the two driving piezoelectric elements 3, an output signal of one driving piezoelectric element 3 is used for feedback, and a driving signal is given to the other driving piezoelectric element 3. Thus, the vibrating body 2 vibrates so as to open and close.

Further, the detecting piezoelectric element 4 is connected to a detecting circuit. The detection circuit includes, for example, a differential circuit, a synchronous detection circuit, a smoothing circuit, an amplification circuit, and the like. At the time of non-rotation, since the detection plate 2b moves in the width direction, the detection plate 2b
Does not bend. Therefore, the output signal of the detecting piezoelectric element 4 becomes 0, which indicates that the rotational angular velocity is not applied. When a rotational angular velocity is applied about the axis of the vibrating body 2, bending vibration occurs in a direction perpendicular to the surface of the detection plate 2b, that is, in a thickness direction of the detection plate 2b due to Coriolis force.
At this time, since the two detection plates 2b are bent in opposite directions, there is a difference between the charges generated in the two detection piezoelectric elements 4. Therefore, by taking the difference between the output signals of the two detecting piezoelectric elements 4 and performing synchronous detection, smoothing, and amplification,
A DC signal corresponding to the Coriolis force can be obtained.

[0004] In addition, energy trap type vibrators,
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.

[0005]

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 vibrating body due to Coriolis force is detected by electric charges generated in a detecting piezoelectric element. However, if the vibrating body is reduced in size, the mass m and the vibration velocity v in the above equation become smaller, so that the detection sensitivity of the Coriolis force is reduced and it becomes difficult to accurately detect the rotational angular velocity.

[0006] Further, 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 also 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.

SUMMARY OF THE INVENTION Accordingly, 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.

[0008]

According to the present invention, there is provided a vibrating body made of a piezoelectric body formed by connecting one end of two arms to form a tuning fork and a base of the two arms for exciting the vibrating body to open and close. Primary electrodes formed opposite to both surfaces of the vibrating body, and two primary electrodes formed opposite to both surfaces of each arm.
A second electrode including a secondary electrode and a portion sandwiched between the secondary electrodes of the arm.
This is a vibrating gyroscope in which an energy trap type resonator is formed by a next electrode. In such a vibrating gyroscope, one secondary electrode can be formed on both surfaces of each arm. Further, in each arm, two secondary electrodes can be formed on one surface, and one secondary electrode facing the secondary electrode on one surface can be formed on the other surface. Also, the present invention provides a vibrating body composed of a piezoelectric body in which one ends of two arms are connected to form a tuning fork.
A comb-shaped electrode including a primary electrode formed at the base of the two arms to oppose both surfaces of the vibrating body to excite the vibrating body to open and close, and a comb-shaped electrode formed on the surface of each arm; This is a vibrating gyroscope in which a surface acoustic wave resonator is formed by electrodes and arms.

By causing the tuning fork type vibrator to open and close, Coriolis force is applied to the vibrator when a rotational angular velocity is applied. Due to this Coriolis force, the vibration direction of the vibrating body changes, and reverse stress is applied to the portion where the two energy trapping type resonators are formed or the portion where the 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 change occurs in the output signal of the two energy trap type resonators or the output signal of the two surface acoustic wave resonators according to the change in the vibration direction of the tuning fork type vibrator. From the difference between these output signals, a signal corresponding to the rotational angular velocity can be obtained.

The above objects, 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.

[0011]

FIG. 1 is a perspective view of one example of a vibrating gyroscope according to the present invention as viewed from one side, and FIG. 2 is a perspective view as viewed from the other side. The vibrating gyroscope 10 includes a vibrating body 12 formed of a piezoelectric material such as a piezoelectric ceramic or a single crystal. The vibrating body 12 is formed in a tuning fork shape in which one ends of two arms 12a and 12b are connected. This vibrating body 12
Polarized in its thickness direction.

At the base of the two arms 12a and 12b, primary electrodes 14a and 14b are formed on both surfaces of the vibrating body 12. These primary electrodes 14a and 14b are formed so as to face each other. On one surface of one arm 12a, two secondary electrodes 16a and 16b are formed so as to be arranged in the longitudinal direction. Further, one secondary electrode 16c is formed on the other surface of the arm 12a so as to face the secondary electrodes 16a and 16b.
These secondary electrodes 16a, 16b, 16c and the arms 12a sandwiched therebetween form an energy trap type resonator. Similarly, two secondary electrodes 18a and 18b are formed on one surface of the other arm 12b so as to be arranged in the longitudinal direction. Further, one secondary electrode 18c is formed on the other surface of the arm 12b so as to face the secondary electrodes 18a and 18b.
These secondary electrodes 18a, 18b, 18c and the arm 12b sandwiched therebetween form an energy trap type resonator.

In order to use this vibrating gyroscope 10,
A circuit as shown in FIG. 3 is used. Primary electrode 14b,
The secondary electrodes 16c and 18c are connected to a reference potential. Further, the primary electrode 14a is connected to the first drive circuit 20. In the first drive circuit 20, a drive signal for exciting the vibration body 12 to generate vibration is generated. When this drive signal is applied to the primary electrode 14a, the primary electrode 14a,
The portion of the vibrating body 12 sandwiched between 14b expands and contracts, and the two arms 12a and 12b vibrate to open and close.

Further, a second drive circuit 22 is connected to the secondary electrodes 16a and 18a. From the second drive circuit 22, a drive signal for exciting the two energy trap type resonators is provided. Further, the secondary electrodes 16b,
18b is connected to the detection circuit 30. The detection circuit 30 includes a differential circuit 32, and outputs a difference between output signals of the secondary electrodes 16b and 18b. The differential circuit 32 is connected to a rectifier circuit 34, and an output signal of the rectifier circuit 34 is supplied to a first smoothing circuit 36.
Is smoothed. The DC component of the output signal of the first smoothing circuit 36 is removed by a DC component removing circuit 38, and the output signal is detected by a synchronous detection circuit 40 in synchronization with the signal of the first drive circuit 20. The output signal of the synchronous detection circuit 40 is smoothed by the second smoothing circuit 42 and amplified by the amplifier circuit 44.

The second driving circuit 22 causes the secondary electrode 1
Energy confined resonator formed by 6a, 16b, 16c and arm 12a and secondary electrodes 18a, 18
Energy-trapping vibration is excited in the energy-trapping resonator formed by the b, 18c and the arm 12b. This energy trapping vibration is caused by the secondary electrode 16a,
16b, 16c and the secondary electrodes 18a, 18b, 1
This vibration is generated only during the period 8c, and has a higher frequency than the opening and closing vibration of the vibrating body 12.

When the vibrating body 12 opens and closes, the portion where the energy trap type resonator is formed also bends,
The resonance transmission characteristic changes according to the bending state. Therefore, as shown in FIGS. 4A and 4B, the vibration waveform of the vibrating body 12 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 state of the two energy trap type resonators is the same, so that a signal having the same waveform is input to the differential circuit 32. Therefore, as shown in FIG.
No signal is output from the differential circuit 32, and it can be seen that the rotational angular velocity is not applied.

When rotating about the axis of the vibrating body 12,
Coriolis force acts in a direction orthogonal to the direction of the opening and closing vibration of the arms 12a and 12b. This Coriolis force causes the arm 1
2a and 12b are displaced, and the directions of bending vibration of the arms 12a and 12b change. 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 arms 12a and 12b, stress is applied to the two energy trapping type resonators, the resonance transfer characteristics thereof change, and the waveforms of the output signals of the secondary electrodes 16b and 18b change. The arms 12a and 12b vibrate in opposite directions so as to open and close with each other.
Coriolis forces acting on a and 12b are reversed. Therefore, the stresses applied to the two energy trap type resonators are in opposite directions, and the waveform changes of the signals output from the secondary electrodes 16b and 18b are also opposite. As a result, FIG.
As shown in (b), an amplitude difference occurs between the output signals of the two energy trap type resonators. Therefore, as shown in FIG. 5C, a signal having an amplitude corresponding to the difference between the amplitudes of the two input signals is output from the differential circuit 32. Further, as shown in FIG. 5D, in the rectifier circuit 34, for example, only the positive portion of the output signal of the differential circuit 32 is output.

As shown in FIG. 5 (e), the output signal of the rectifier circuit 34 has a high frequency component removed by a first smoothing circuit 36. Further, as shown in FIG. 5F, a signal corresponding to a change in the bending vibration of the arms 12a and 12b is obtained by removing the DC component in the DC component removing circuit 38. This signal is detected by the synchronous detection circuit 40 in synchronization with the signal of the first drive circuit 20, and for example, only the positive portion of the signal is output as shown in FIG. Therefore, if this signal is smoothed by the second smoothing circuit 42 and further amplified by the amplifier circuit 44, a DC signal corresponding to the Coriolis force can be obtained.

Further, as shown in FIG. 6, the rotational angular velocity can be detected from the change of the resonance frequency characteristic of the energy trap type resonator. In the vibrating gyroscope 10 used here, one secondary electrode 46a, 46b is formed on the opposing surface of the arm 12a. Also, one secondary electrode 48 is provided on each of the facing surfaces of the arms 12b.
a, 48b are formed. And, as shown in FIG.
A first oscillation circuit 50 is connected between the primary electrodes 14a and 14b. Then, the output signal from the primary electrode 14b is fed back to the oscillation circuit 50, and the signal obtained by the oscillation circuit 50 is input to the primary electrode 14a as a drive signal. Thereby, the vibrating body 12 vibrates so that the arms 12a and 12b open and close.

Further, a second oscillation circuit 52 is connected between the secondary electrodes 46a and 46b, and the secondary electrodes 48a and 48b
A third oscillation circuit 54 is connected between them. These oscillation circuits 52 and 54 excite energy confinement vibrations in the two energy confinement type resonators. Further, the secondary electrodes 46a and 48a are connected to the detection circuit 60. The detection circuit 60 includes a frequency difference detection circuit 62.
The frequency difference detection circuit 62 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 62 is detected by the synchronous detection circuit 64 in synchronization with the output signal of the first oscillation circuit 50. The signal detected by the synchronous detection circuit 64 is smoothed by the smoothing circuit 66 and further amplified by the amplifier circuit 68.

A vibrating gyroscope 10 using such a circuit
In the case of (1), the output signal of the energy trap type resonator is a signal whose frequency is modulated in accordance with the bending vibration of the vibrating body 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 arms 12a and 12b. At the time of non-rotation, the bending state of the two energy trap type resonators is the same,
Signals having the same frequency characteristics are output from the next electrodes 46a and 48a. Therefore, the frequency difference detection circuit 62
Does not output a signal.

When rotating about the axis of the vibrating body 12,
The direction of the bending vibration of the arms 12a and 12b is changed by 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, a voltage corresponding to the frequency difference between the output signals of the secondary electrodes 46a and 48a is output from the frequency difference detection circuit 62 of the detection circuit 60. The output signal of the frequency difference detection circuit 62 is detected by the synchronous detection circuit 64 in synchronization with the output signal of the first oscillation circuit 50. The detected signal is smoothed by a smoothing circuit 66 and further amplified by an amplifier circuit 68 to obtain a DC signal corresponding to the Coriolis force.

Further, as shown in FIG. 8, a vibration gyro using a surface acoustic wave may be used. This vibrating gyro 1
0, primary electrodes 14a and 14b are formed on a tuning-fork type vibrating body 12 formed of a piezoelectric body.
Two comb-shaped electrodes 70a and 70b are formed on a and 12b. The comb-shaped electrode 70a is formed by a common electrode 72a and input / output electrodes 74a and 76a. Then, the arm 12a formed of a piezoelectric material is polarized between the common electrode 72a and the input / output electrode 74a, and the arm 12a is polarized between the common electrode 72a and the input / output electrode 76a. Similarly, the comb-shaped electrode 70b is formed by the common electrode 72b and the input / output electrodes 74b and 76b. Then, the common electrode 72
The arm 12b formed of a piezoelectric material is polarized between the input electrode b and the input / output electrode 74b, and the arm 12b is polarized between the common electrode 72b and the input / output electrode 76b. A surface acoustic wave resonator is formed by the comb-shaped electrode 70a and the arm 12a, and a surface acoustic wave resonator is formed by the comb-shaped electrode 70b and the arm 12b.

In order to use the vibrating gyroscope 10,
An oscillation circuit 50 is connected between the primary electrodes 14a and 14b. The oscillation circuit 50 excites the vibration of the vibrating body 12. Further, the common electrodes 72a and 72b of the comb electrodes 70a and 70b are connected to a reference potential. The drive circuit 80 is connected to the input / output electrodes 74a and 74b, and the surface acoustic waves are excited by the drive signals.
The excited surface acoustic waves propagate through the arms 12a and 12b, and are converted into electric signals at the input / output electrodes 76a and 76b. Then, signals output from the input / output electrodes 76a and 76b are input to the detection circuit 30.

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. 5 and FIG. 5, the output signal of the energy trap type resonator is processed by the detection circuit 30. Here, the output signal of the surface acoustic wave resonator is processed by the detection circuit 30 so that the rotation applied to the vibrating gyroscope 10 is controlled. An angular velocity is detected.

In the vibrating gyroscope 10 using the surface acoustic wave resonator, separate oscillation circuits are connected to the two surface acoustic wave resonators, and the arms 12a, 1 by Coriolis force.
The fact that a difference in the oscillation frequency between the two surface acoustic wave resonators due to a change in the waveguide length of the surface acoustic wave resonator due to the deformation of 2b may be used. In this case, for example, by taking the beat of the output signals of the two surface acoustic wave resonators, it can be used instead of taking the differential output.

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 vibrating body 12, even if the generated Coriolis force is small, the rotational angular velocity can be detected with extremely high sensitivity. Therefore, even if the vibrating body 12 is downsized, the rotational angular velocity can be detected with high sensitivity.

[0028]

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 of a vibrating gyroscope according to the present invention as viewed from one surface side.

FIG. 2 is a perspective view of the vibrating gyroscope shown in FIG. 1 as viewed from the other surface side.

FIG. 3 is a block diagram showing a circuit for using the vibrating gyroscope shown in FIG. 1;

4 is a graph showing signal waveforms of each circuit when the circuit shown in FIG. 3 is not rotating.

5 is a graph showing a signal waveform of each circuit when the circuit shown in FIG. 3 rotates.

FIG. 6 is a perspective view showing another example of the vibrating gyroscope according to the present invention.

FIG. 7 is a block diagram showing a circuit for using the vibrating gyroscope shown in FIG. 6;

FIG. 8 is a plan 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.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Vibrating gyroscope 12 Vibrating body 12a, 12b Arm 14a, 14b Primary electrode 16a, 16b, 16c Secondary electrode 18a, 18b, 18c Secondary electrode 46a, 46b, 48a, 48b Secondary electrode 70a, 70b Comb-shaped electrode 72a, 72b common electrode 74a, 74b, 76a, 76b input / output electrode

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Kumanda 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Inside Murata Manufacturing Co., Ltd. (72) Inventor Yoshio Kawai 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto No. 10 In Murata Manufacturing Co., Ltd. (72) Inventor Jiro Miyazaki 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Pref. In Murata Manufacturing Co., Ltd. (58) Field surveyed (Int.Cl. ⁷ , DB name) G01C 19/56 G01P 9/04

Claims (4)

(57) [Claims] 1. A vibrating body comprising a piezoelectric body formed by connecting one ends of two arms into a tuning fork shape, and opposing both sides of the vibrating body at bases of the two arms to excite opening and closing vibrations in the vibrating body. And a secondary electrode formed opposite to both sides of each of the arms. Energy is confined by the portion of the arm sandwiched between the secondary electrodes and the secondary electrode. A vibrating gyroscope with a shaped resonator. 2. The vibrating gyroscope according to claim 1, wherein one of said secondary electrodes is formed on both sides of each of said arms. 3. In each of the arms, two of the secondary electrodes are formed on one surface thereof, and one of the secondary electrodes facing the secondary electrode of the one surface is formed on the other surface. The vibrating gyroscope according to claim 1. 4. A vibrating body made of a piezoelectric body formed into a tuning fork by connecting one ends of two arms, and opposing both sides of the vibrating body at bases of the two arms to excite the vibrating body to open and close vibrations. A vibrating gyroscope, comprising: a primary electrode formed as described above; and a comb-shaped electrode formed on a surface of each of the arms, wherein a surface acoustic wave resonator is formed by the comb-shaped electrode and the arm.