JP2010054405A - Oscillator for angular velocity detector and angular velocity detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems of conventional angular velocity detectors using oscillator, in which the amplitude factor cannot be raised, which disturbs improvement in SNR of the angular velocity detector, since a signal for steadily oscillating the oscillator is connected to a detection electrode through a parasitic capacity on the oscillator to superimpose an unnecessary component to a detection signal, while in a method for canceling the unnecessary component by providing a correction electrode in the vicinity of a fork part of an oscillation leg of the oscillator to thereby provide a new parasitic capacity between the correction electrode and the detection electrode, and injecting a correction signal of the reverse phase to the unnecessary component therethrough, the correction quantity reduces in an oscillator designed to have a detection leg for detecting the angular velocity separately from the steadily oscillating drive leg since the distance of the fork part of the drive leg from the detection electrode increases, and the parasitic capacity thus reduces. <P>SOLUTION: The correction electrode is provided in the vicinity of the detection leg of a base part, whereby the parasitic capacity between the correction electrode and the detection electrode is increased to increase the correction quantity, so that the unnecessary component is sufficiently canceled. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a vibrator for an angular velocity detection device and an angular velocity detection device.

The angular velocity detection device is mounted on an in-vehicle car navigation system for the purpose of detecting the traveling direction. It is also mounted on still cameras or video cameras for detecting camera shake, and is expected to be applied as an input device for portable information terminals and portable game devices.

The vibration type angular velocity detection device detects a change in vibration caused by Coriolis force when an angular velocity is applied to a vibrator that constantly vibrates.

As the vibrator, a piezoelectric body or a piezoelectric vibrator added to a metallic vibrator (body) is used. The displacement of the leg of the vibrator is converted into an electric charge by the piezoelectric body or the piezoelectric film, so that the electric charge is collected through the electrode, and the displacement of the leg of the vibrator is reduced by current-voltage conversion or charge-voltage conversion. I can read.

Patent Document 1 discloses an angular velocity detection device having a drive electrode that is constantly oscillated at the time of angular velocity detection and a detection electrode for detecting a vibration change when the angular velocity is applied.

When the vibration of the vibrator changes due to the application of the angular velocity, the charge induced in the detection electrode changes. This change in charge is information having the same frequency as the drive frequency of the vibrator. A proportional DC output voltage signal can be obtained. This is the basic principle of the vibration type angular velocity detection device.

Note that the signal before synchronous detection is alternating current, but the signal amplitude becomes small here because it is direct current after synchronous detection.

The detection circuit amplifies a weak signal using a plurality of amplifiers. In order to improve the SNR of the angular velocity detection device, it is effective to give a large gain to the amplifier in the detection circuit as close to the signal source as possible. If an amplification circuit that is far from the signal source is to be greatly amplified, noise superimposed by another circuit between the signal source and the signal source is also amplified together, increasing the noise.

The problem here is the amount of charge induced in the detection electrode when stationary.

There are two factors that cause charge to be induced in the detection electrode at rest. One is leakage vibration due to manufacturing errors of the vibrator, and the other is capacitive coupling between the drive electrode and the detection electrode. Hereinafter, noise due to leakage vibration is referred to as a mechanical leakage signal, noise due to capacitive coupling is referred to as an electrical leakage signal, and the sum of these is simply referred to as a leakage signal.

If the leak signal is large, the gain cannot be increased. Therefore, it is necessary to reduce the amplitude of the leak signal in order to improve the SNR.

It is known that an electric leakage signal can be canceled to some extent by providing two detection electrodes with a leg interposed therebetween and taking a difference between signals extracted from each. However, since the signal amplitude before taking the difference is large, the gain before taking the difference is limited. Further, since the coupling capacitances between the drive electrodes and the respective detection electrodes are not necessarily equal, the difference remains without being canceled out.

Patent Document 1 describes a technique for suppressing a leak signal. What is described in Patent Document 1 focuses on the electric leakage signal and cancels it by applying a signal having a phase opposite to that of the electric leakage signal.

Specifically, a correction electrode is provided on a base of the vibrator below the drive leg and a correction signal is injected using a parasitic capacitance between the correction electrode and the detection electrode. The signal to be injected is used by inverting the phase of the driving voltage for driving the vibrator.

In Patent Document 1, an example of a biped tuning fork type vibrator is described. In this type of vibrator, both the drive electrode and the detection electrode are provided on the same leg.

On the other hand, as described in Patent Document 2, there is also an angular velocity detection device that uses a tripod or more tuning fork type vibrator. In this apparatus, a leg for detection is provided independently from two legs for driving, and the three legs are connected at the base. In such a vibrator, the drive electrode is provided on the drive leg and the detection electrode is provided on the detection leg.

Japanese Patent No. 3399150 (FIG. 8) Japanese Patent No. 4068370 (FIGS. 1 and 2)

In this way, a vibrator with independent legs for detection can be designed to suppress leakage vibration to a low level, so that a mechanical leakage signal can be reduced. Further, since the drive electrode and the detection electrode are separated from each other, the coupling capacitance is reduced, and the electric leakage signal can be reduced.

For such a vibrator, in order to further reduce the electric leakage signal, when a correction electrode is provided at the base below the drive leg as in Patent Document 1, the distance between the correction electrode and the detection electrode However, since the coupling capacitance is small, there is a problem that the adjustable range is narrowed.

The present invention has been made to solve the above-described problems caused by the prior art, and an object of the present invention is to provide an angular velocity detection device having a small influence of a leak signal and a high SNR.

In order to solve the above-described problems, in the vibrator for an angular velocity detection device according to the present invention, at least two drive legs that constantly vibrate, a detection leg that generates vibration when angular velocity is applied, the drive leg, and the detection A base for connecting a leg; a drive electrode provided on the drive leg for exciting the drive leg; a detection electrode provided on the detection customer for detecting the vibration of the detection leg; and the detection In the vibrator for an angular velocity detecting device including a correction electrode for applying a correction signal to the electrode, the correction electrode is provided near a connection portion of the detection leg in the base portion.

According to this configuration, the correction electrode can be provided near the detection electrode, and the parasitic capacitance can be increased, so that effective leakage signal cancellation can be achieved.

The detection electrode includes a first detection electrode and a second detection electrode,
The correction electrode may be provided between the first detection electrode and the second detection electrode in the base. According to this configuration, the correction signal can be efficiently injected into both the first detection electrode and the second detection electrode.

The distance between the correction electrode and the first detection electrode can be made different from the distance between the correction electrode and the second detection electrode. According to this configuration, the correction amount to the first detection electrode and the second detection electrode can be optimized with the correction signal from one correction electrode.

An angular velocity detection device according to the present invention includes the vibrator, an oscillation circuit for exciting the drive leg, a detection circuit for detecting vibration of the detection leg, and a correction for correcting a signal of the detection circuit. A correction signal generation circuit for generating a signal, wherein the oscillation circuit includes a displacement detection circuit for detecting vibration of the drive leg, and the correction signal generation circuit is based on an output signal of the displacement detection circuit. Then, a correction signal having the same frequency as the oscillation frequency of the vibrator is generated. According to this configuration, it is not necessary to prepare a dedicated oscillator for generating the correction signal, and the circuit scale can be reduced.
In addition, a correction signal with less distortion can be generated as compared with the case based on the output of the oscillation circuit, and noise can be reduced.

The correction signal generation circuit may include a phase shift circuit that adjusts the phase and an amplitude adjustment circuit that adjusts the amplitude. According to this configuration, when there is a phase difference between the electric leakage and the correction signal due to the phase delay of the amplifier in the oscillation circuit, or when the amplitude is excessive or insufficient, this can be corrected. . As a result, the leakage signal amplitude can be effectively reduced and the noise can be reduced.

The oscillation circuit includes an amplitude detection circuit that detects an output signal amplitude of the displacement detection circuit in the oscillation circuit, and a variable gain circuit that adjusts the gain of the output signal based on the output of the amplitude detection circuit, An automatic gain control function for making the amplitude of the vibrator constant can be configured.

ADVANTAGE OF THE INVENTION According to this invention, the vibrator | oscillator for vibration type angular velocity detection apparatuses and vibration type angular velocity detection apparatus with high SNR can be provided.

Hereinafter, an optimal embodiment of the present invention will be described with reference to FIGS.

(First embodiment)
FIG. 1 is a diagram showing a first embodiment of a vibrator for an angular velocity detection device of the present invention. The vibrator 1 includes two drive legs 2 that constantly vibrate when angular velocity is detected, a detection leg 3 that vibrates when a Coriolis force is applied to the vibrator 1, and a base that connects the drive leg 2 and the detection leg 3. 4. The drive leg 2, the detection leg 3, and the base 4 are formed of a piezoelectric body. The drive leg 2 includes a first drive electrode 5a and a second drive electrode 5b, and the detection leg 3 includes a detection electrode pair including a first detection electrode 6a and a second detection electrode 6b. 6 is provided. Further, the vibrator 1 includes a correction electrode 7 between the first detection electrode 6 a and the second detection electrode 6 b in the base 4. Since the structure of a vibrator with a tripod or more is well known, only the above description will be given. A control circuit shown in FIG. 3 is connected to each electrode. This control circuit will be described later.

In the vibrator 1, the drive leg 2 vibrates in the in-plane direction and the detection leg 3 is stationary at the steady state. When an angular velocity is applied to the vibrator 1, an out-of-plane vibration component is generated in the drive leg 2 due to the Coriolis force, and thereby the detection leg 3 vibrates. By detecting this vibration by the detection electrode pair 6, the applied angular velocity is detected.

The correction electrode 7 is provided at a position close to both the first detection electrode 6a and the second detection electrode 6b. According to this configuration, the correction signal can be efficiently injected into the first detection electrode 6a and the second detection electrode 6b.

On the base 4, the first detection electrode 6a is closer to the first drive electrode 5a than the second detection electrode 6b. Accordingly, the signal of the first drive electrode 5a is more strongly coupled to the first detection electrode 6a having a short distance. On the other hand, the second detection electrode 6b having a long distance is relatively weakly coupled. For this reason, a difference occurs between the amplitude of the electric leakage signal applied to the first detection electrode 6a and the amplitude of the electric leakage signal applied to the second detection electrode 6b.

In order to correct this difference, the distance between the correction electrode 7 and the first detection electrode 6a is made different from the distance between the correction electrode 7 and the second detection electrode 6b. That is, the adjustment amount can be adjusted by making the distance between the correction electrode 7 and the first detection electrode 6a (A1 in FIG. 1) closer than the distance between the correction electrode 7 and the second detection electrode 6b (A2 in the figure). Can be balanced.

In this way, by changing the distance between the correction electrode 7 with respect to the first detection electrode 6a and the second detection electrode 6b, the coupling capacitance between the electrodes is changed, so that the optimum for each detection electrode. A correction signal can be injected. As a result, the leakage signal amplitude can be optimally suppressed for each of the first detection electrode 6a and the second detection electrode 6b, and an angular velocity detection device having a high SNR can be realized.

(Second Embodiment)
FIG. 2 is a diagram showing a second embodiment of the vibrator for an angular velocity detection device of the present invention. The vibrator 21 includes two drive legs 22 that constantly vibrate when angular velocity is detected, two detection legs 23a and 23b that vibrate when a Coriolis force is applied to the vibrator 21, the drive legs 22 and the detection legs. And a base 24 for connecting the legs 23a and 23b. The first detection leg 23a includes a first detection electrode 26a and a second detection electrode 26b, and the second detection leg 23b includes a third detection electrode 26c and a fourth detection electrode 26d. Is provided. Further, the vibrator 21 includes a first correction electrode 27a between the first detection electrode 26a and the second detection electrode 26b in the base 24, and the third detection electrode 26c and the fourth detection electrode 26b. A second correction electrode 27b is provided between the detection electrode 26d.

In the vibrator 21, the drive leg 22 vibrates in the in-plane direction and the detection leg 23 is stationary at the steady state. When an angular velocity is applied to the vibrator 21, an out-of-plane vibration component is generated in the drive leg 22 due to the Coriolis force, thereby vibrating the detection legs 23a and 23b. By detecting this vibration by the detection electrode pair 26, the angular velocity is detected.

According to this configuration, the correction electrode 27 can be provided at a position close to both the first detection electrode 26a and the second detection electrode 26b. Therefore, the correction signal can be efficiently injected into the first detection electrode 26a and the second detection electrode 26b.

Further, in the vibrator having a plurality of detection legs as in the present embodiment, the correction characteristics are improved by providing correction electrodes for the respective detection legs. That is, the correction range can be expanded compared to the case where there is one correction electrode.

FIG. 3 is a block diagram illustrating a configuration of a control circuit that controls the vibrators 1 and 21 according to the first and second embodiments. The control circuit includes an oscillation circuit 51 that oscillates the vibrators 1 and 21 steadily, a detection circuit 52 that processes an angular velocity detection signal of the vibrators 1 and 21, and corrections that are applied to the correction electrodes 7 and 27. And a correction signal generation circuit 53 for generating a signal.

The oscillation circuit 51 is configured to cause a sine wave oscillation based on the displacement detection circuit 55 that detects the displacement of the vibration leg of the vibrator, the amplitude detection circuit 57 that detects the amplitude thereof, and the output of the amplitude detection circuit 57. And a variable gain circuit 56 for changing the gain.

The detection circuit 52 includes a displacement detection circuit 60 for detecting the displacement of the detection leg for each of the detection electrodes 6 and 26, and a differential amplifier circuit for taking the difference between the outputs of these displacement detection circuits 60. 61, a synchronous detection circuit 62 for synchronously detecting the differentially amplified signal and converting the angular velocity signal into a direct current, an amplifier circuit 63 for amplifying the signal to a desired level, and an AC component removed A low-pass filter (LPF) 64.

Here, the operation of the detection circuit 52 will be briefly described.

When a Coriolis force is applied to the vibrators 1 and 21, the output of the displacement detection circuit 60 appears as a signal having the same frequency as the drive frequency, the amplitude of which changes. The greater the applied angular velocity, the greater this amplitude change.

However, the aforementioned electric leakage signal is superimposed on the output of the displacement detection circuit 60. Therefore, the differential amplifier circuit 61 takes the difference between the output of the displacement detection circuit 60 on the first detection electrode side and the output of the displacement detection circuit 60 on the second detection electrode side, and cancels out the electric leakage signal to some extent. To do.

Since the output of the angular velocity detection device is preferably a DC voltage proportional to the angular velocity, the signal of the displacement detection circuit 60 is synchronously detected by the synchronous detection circuit 62. As a detection clock at this time, a signal is extracted from the oscillation circuit 53 and used after adjusting the phase.

The synchronously detected signal has angular velocity information converted to direct current, but the drive frequency component is also superimposed as noise. Therefore, the driving frequency component is removed by passing through the LPF 64 to obtain a desired signal.

In addition, an amplifier circuit 63 is used to amplify the angular velocity information to a desired level.

The above is the description of the operation of the detection circuit 52. In the present invention, a correction circuit 53 is further provided.

In the correction circuit 53, the signal of the driving frequency is taken out from the displacement detection circuit 55 of the oscillation circuit 51, the phase and amplitude are adjusted by the phase shift circuit 58 and the amplitude adjustment circuit 59, a correction signal is generated, and the correction on the vibrator is performed. Apply to electrode. The adjustment of the phase and amplitude in the phase shift circuit 58 and the amplitude adjustment circuit 59 is performed by measuring the waveform of the leak signal of the first detection electrode 6a and the second detection electrode 6b and shifting the leak signal. Adjustment is performed so that optimum correction is performed according to the phase and amplitude (leakage signals of the detection electrodes 6a and 6b are reduced). Further, this adjustment is performed once at the time of manufacturing the angular velocity detecting device, and thereafter, correction is always performed during the operation of the angular velocity detecting device.

The correction signal applied to the correction electrode 7 is input to the displacement detection circuit 60 in the detection circuit 52 through the parasitic capacitance between the correction electrode 7 and the detection electrodes 6a and 6b. Thereby, the output amplitude by the electric leakage signal of the displacement detection circuit 60 can be canceled.

Further, as shown in FIG. 1, a difference is intentionally made between the parasitic capacitance between the correction electrode 7 and the first detection electrode 6a and the parasitic capacitance between the correction electrode 7 and the second detection electrode 6b. By providing, a correction signal suitable for each of the detection electrodes 6a and 6b can be injected.

By reducing the signal amplitude in this way, the gain of the displacement detection circuit 60 can be increased, and the SNR of the angular velocity detection device can be improved.

It is a top view which shows the 1st Example of the vibrator | oscillator for angular velocity detection apparatuses of this invention. It is a top view which shows the 2nd Example of the vibrator | oscillator for angular velocity detection apparatuses of this invention. It is a block diagram which shows the Example of the control circuit of the angular velocity detection apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vibrator 2 Drive leg 3 Detection leg 4 Base part 5a 1st drive electrode 5b 2nd drive electrode 6 Detection electrode pair 6a 1st detection electrode 6b 2nd detection electrode 7 Correction electrode

21 vibrator 22 drive leg 23a first detection leg 23b second detection leg 24 base 26a first detection electrode 26b second detection electrode 26c third detection electrode 26d fourth detection electrode 27a first correction electrode 27b Second correction electrode

51 Oscillation circuit 52 Detection circuit 53 Correction signal generation circuit 55 Displacement detection circuit 56 Variable gain circuit 57 Amplitude detection circuit 58 Phase shift circuit 59 Amplitude adjustment circuit 60 Displacement detection circuit 61 Differential amplifier circuit 62 Synchronous detection circuit 63 Amplifier circuit 64 LPF

Claims (6)

At least two drive legs that constantly vibrate, a detection leg that generates vibration when an angular velocity is applied, a base that connects the drive leg and the detection leg, and a drive leg that excites the drive leg. An angular velocity detecting device vibrator comprising: a drive electrode; a detection electrode provided to the detection customer for detecting the vibration of the detection leg; and a correction electrode for applying a correction signal to the detection electrode. 3. The vibrator for an angular velocity detecting device according to claim 1, wherein the correction electrode is provided in the vicinity of a connection portion of the detection leg in the base portion. The detection electrode includes a first detection electrode and a second detection electrode,
2. The vibrator for an angular velocity detecting device according to claim 1, wherein the correction electrode is provided between the first detection electrode and the second detection electrode in the base. 3. 3. The vibrator for an angular velocity detecting device according to claim 2, wherein a distance between the correction electrode and the first detection electrode is different from a distance between the correction electrode and the second detection electrode. The vibrator according to claim 1 or 2, and an oscillation circuit for exciting the drive leg,
A detection circuit for detecting vibration of the detection leg; and a correction signal generation circuit for generating a correction signal for correcting a signal of the detection circuit, wherein the oscillation circuit detects vibration of the drive leg. An angular velocity detection device, wherein the correction signal generation circuit generates a correction signal having the same frequency as the oscillation frequency of the vibrator based on an output signal of the displacement detection circuit. The angular velocity detection device according to claim 4, wherein the correction signal generation circuit includes a phase shift circuit for adjusting a phase and an amplitude adjustment circuit for adjusting an amplitude. The oscillation circuit includes an amplitude detection circuit that detects an output signal amplitude of the displacement detection circuit in the oscillation circuit, and a variable gain circuit that adjusts the gain of the output signal based on the output of the amplitude detection circuit, The angular velocity detection device according to claim 4, wherein an automatic gain control function for making the amplitude of the vibrator constant is configured.

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