JP2000329559A - Angular speed sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make obtainable a low noise angular speed direction output by detecting a vibration due to Coriolis force orthogonal to the direction of drive oscillation through a detecting coil and canceling a null voltage due to leakage vibration of an oscillator by taking the difference from a driving signal. SOLUTION: In an oscillation gyro sensor, the resonance frequency of an oscillator 1 in the driving direction must be brought close to the resonance frequency in the direction for detecting Coriolis force in order to enhance detection accuracy. When they are brought close to each other, a mechanical leakage coupling takes place in each vibratory direction to result in a vibration in the direction shown by an arrow DA. In this regard, a null voltage is detected by a detecting coil 5 even when an angular acceleration is not applied and thereby the null voltage must be separated from an output produced by Coriolis force. Since the null voltage signal of the coil 5 has same phase as the driving signal, the null voltage can be brought to zero apparently by taking the difference between the output from the coil 5 and the driving signal through a differential circuit 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity sensor for detecting a magnitude of an angular velocity by detecting a Coriolis force acting in a direction orthogonal to a vibration direction of the object when an angular velocity is applied to a vibrating object. .

[0002]

2. Description of the Related Art An angular velocity sensor is widely used as an autonomous navigation sensor for a car navigation system and a camera shake prevention sensor for a video movie. Above all, a piezoelectric gyro using a piezoelectric body for driving a vibrator and detecting Coriolis force is widely used as a small and inexpensive angular velocity sensor. The configuration of such an angular velocity sensor is described in, for example, a document “Basics of Piezoelectric Gyro Sensor Technology”, Electronic Ceramics, October 1991, pp. 195-143.
27-35.

FIG. 8 is a schematic block diagram showing the configuration of the first prior art angular velocity sensor described above.
In FIG. 8, the piezoelectric gyro is shown in a plan view.

In the piezoelectric gyro shown in FIG. 8, a vibrator 1 having a rectangular cross section is provided with a predetermined self-oscillation circuit 30 using a driving piezoelectric element 20 and a feedback piezoelectric element 21 in the x-axis direction. Excitation vibration is performed. When an angular velocity Ω about the z-axis is applied under such vibration, vibration is excited in the y-axis direction orthogonal to the self-excited vibration, and the vibration in the y-axis direction causes the detection piezoelectric bodies 22 and 23 to vibrate. Voltage is generated.

[0005] These voltages are passed through a differential circuit 31, a synchronous detection circuit 32, and a smoothing circuit 33 to output a DC voltage output proportional to the angular velocity Ω.

In the case of such a piezoelectric gyro, the voltage generated in the detecting piezoelectric members 22 and 23 by the Coriolis force coincides in phase with the drive signal of the self-excited oscillation circuit 30. By detecting the phase of the signal, only the signal due to the Coriolis force can be extracted.

However, if mechanical leakage coupling occurs between the vibration of the vibrator 1 in the x-axis direction and the vibration in the y-axis direction, the vibrator 1 is kept in the x-direction even when the angular velocity is not applied. Vibration in the axial direction also causes vibration in the y-axis direction. The voltage generated by such vibration is output from the detecting piezoelectric members 22 and 23 as a null voltage.

When the summation of the detecting piezoelectric members 22 and 23 is performed, the null voltage can be apparently reduced to zero, but the voltage signal due to the Coriolis force when the angular velocity is applied is canceled out, and the detection becomes impossible. .

Therefore, when a null voltage is generated,
Feedback piezoelectric element 21 and detection piezoelectric element 22 or 23
The output from the feedback piezoelectric element 21 and the detection piezoelectric element 22
Alternatively, by taking the difference from the output from 23, the null voltage can be apparently reduced to zero. In this way, it is common practice to detect only the signal due to the Coriolis force by detecting the phase of the voltage signal due to the Coriolis force with the drive signal.

A piezoelectric gyro according to a second conventional example shown in FIG. 9 is for solving the problem of the null voltage described above, and is described in the document "Small gyro and its application", Journal of the Japan Society of Mechanical Engineers, November No. 1993, pp. 14-17. In the piezoelectric gyro shown in FIG. 9, the vibrator 1 having a triangular cross section has a predetermined self-excited oscillation in the x-axis direction by a self-excited oscillation circuit 30 using driving piezoelectric bodies 24 and 25 and a feedback piezoelectric body 21. Perform vibration.

Then, when an angular velocity Ω about the z-axis is applied under such vibration, the vibration is excited in the y-axis direction orthogonal to the self-excited vibration. Here, the vibrations in the y-axis direction are transmitted to the driving piezoelectric bodies 24 and 25 which also serve as the detecting piezoelectric bodies.
The voltage generated by the differential circuit 31 and the synchronous detection circuit 3
2. By passing through the smoothing circuit 33, it is converted into a DC voltage output proportional to the angular velocity Ω and output.

In this case, a voltage is generated in the driving piezoelectric members 24 and 25 which also serve as detecting piezoelectric members by vibration in the x-axis direction even when no angular velocity is applied. However, since these voltages have the same phase, this voltage can be apparently reduced to zero by taking a differential. In addition, when the angular velocity is applied, voltages due to the Coriolis force are generated in opposite phases in the driving piezoelectric bodies 24 and 25 which also serve as the detecting piezoelectric bodies. By canceling out the null voltage and detecting the phase with the drive signal, only the voltage due to the Coriolis force can be extracted.

[0013]

Such a conventional piezoelectric gyro has a circuit configuration for obtaining a differential output from a piezoelectric body. However, the voltage output from the piezoelectric body has a large noise. A piezoelectric body is manufactured by subjecting a polycrystal in which fine crystals are randomly arranged to a polarization treatment so that the direction of spontaneous polarization of each crystal is oriented in one direction on average.

When strain is applied to the piezoelectric body, the direction of the spontaneously polarized fine crystal changes and the polarization state as a whole changes, so that the strain can be extracted from the external electrode as a voltage. Since the voltage detected from the piezoelectric body is caused by the rotation or deformation of the fine crystal inside the piezoelectric body, the output noise of the piezoelectric body is considered to increase.

For example, PZT (1 × 9 m
m, 0.2 mm in thickness), and consider a configuration in which this piezoelectric body is attached to a vibrator made of an Elinvar alloy, which is a highly elastic metal having a resonance frequency of 24 kHz, to resonate and vibrate.
When a distortion is applied so that the output from the piezoelectric body becomes 1.8 V, the noise becomes 14 μV / √Hz.

This is because normal amplifier noise is 1 nV / √
Since the frequency is about Hz, it is about four digits larger.

The output noise from the piezoelectric body increases as the amplitude of the piezoelectric body increases, and if the amplitude of the vibrator is increased in order to increase the angular velocity detection sensitivity, the output noise from the piezoelectric body also increases. It has become.

In the conventional piezoelectric gyro, even if the null voltage is canceled by taking the differential of the output signal from the piezoelectric body, even if the null voltage can be canceled as long as the signal from the piezoelectric body having a large noise is used. Noise components remain. Therefore, S
However, there has been a problem that the / N ratio becomes small and the angular velocity cannot be detected with high resolution.

The present invention has been made in view of such a problem, and detects Coriolis force with low noise.
It is an object to provide an angular velocity sensor having high resolution.

[0020]

According to a first aspect of the present invention, there is provided an angular velocity sensor comprising: a vibrator; at least one permanent magnet provided near a free end of the vibrator; Drive means for exciting the vibrator in the drive direction, feedback detection means for detecting the excited state, and a vibration direction orthogonal to the vibration direction for detecting vibration in a direction perpendicular to the vibration direction of the vibrator excited by the drive means At least one detecting coil arranged in the direction, a differential circuit for obtaining a difference between a null voltage generated in the detecting coil and a drive signal, and an output signal of the differential circuit based on a signal from the detecting means for feedback. And a synchronous detection circuit for detecting

According to a second aspect of the present invention, there is provided an angular velocity sensor comprising: a vibrator; at least two permanent magnets provided near a free end of the vibrator; driving means for exciting the vibrator in a driving direction;
Feedback detection means for detecting the excitation state, and at least two detection coils for detecting vibration in a direction orthogonal to the vibration direction of the vibrator excited by the drive means, the detection coil, The detection coil is arranged so that the vibration direction of the vibrator excited by the driving means and the coil surface have an angle of less than 90 ° and the surface of the coil is orthogonal to the magnetization direction of the permanent magnet. A differential circuit for canceling the voltage generated by the vibration in the driving direction of the vibrator by taking the differential of the voltage generated in another detection coil, and a signal from the feedback detection means, and the output signal of the differential circuit. And a synchronous detection circuit for detecting

According to a third aspect of the present invention, there is provided an angular velocity sensor having a columnar vibrator having a polygonal cross section, at least two permanent magnets provided near a free end of the vibrator, and exciting the vibrator in a driving direction. A driving means, a feedback detecting means for detecting an excitation state, and at least two detection coils for detecting vibration in a direction orthogonal to a vibration direction of the vibrator excited by the driving means; The detection coil is arranged so as to have a coil surface perpendicular to the magnetization direction of the permanent magnet, and the voltage generated by the vibration in the driving direction of the vibrator is applied to the detection coil by the voltage differential generated by another detection coil. And a synchronous detection circuit for detecting an output signal of the differential circuit with a signal from the feedback detection means.

The angular velocity sensor according to the fourth aspect is the third aspect.
In addition to the configuration of the angular velocity sensor described, the polygonal shape is an odd number having three or more vertices.

According to a fifth aspect of the present invention, there is provided an angular velocity sensor according to the first aspect.
In addition to the configuration of the angular velocity sensor described above, the vibrator provided with at least one permanent magnet near the free end is a magnetic material magnetized in a direction orthogonal to the vibration direction of the vibrator excited by the driving means. is there.

According to the sixth aspect of the present invention, there is provided an angular velocity sensor according to the first aspect.
In addition to the configuration of the angular velocity sensor according to any one of (5) to (5), the driving unit that excites the vibrator includes a piezoelectric body.

The angular velocity sensor according to the seventh aspect is the first aspect.
In addition to the configuration of the angular velocity sensor according to any one of the first to fifth aspects, the driving unit that excites the vibrator includes a coil.

The angular velocity sensor according to the eighth aspect is the first aspect.
In addition to the configuration of the angular velocity sensor according to any one of the first to sixth aspects, the feedback detecting means for detecting the excitation state includes a piezoelectric body.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below in detail with reference to FIGS.

[First Embodiment] FIG. 1 is a perspective view of an angular velocity sensor according to a first embodiment of the present invention, and FIG. 2 is a plan view and a block diagram thereof. 1 and 2, the angular velocity sensor unit 10 includes a vibrator 1, a driving piezoelectric body 2, a feedback piezoelectric body 3, a permanent magnet 4, and a detection coil 5.

As the vibrator 1, a constant elastic metal (for example, EL / 3 made of Sumitomo Special Metals) can be used so that the vibration characteristics do not change with changes in the ambient temperature. It is also possible to use a constant elastic metal such as another Elinvar alloy. As the piezoelectric bodies 2 and 3, PZT (Pb (Z
Although (r, Ti) O ₃ was used, it is also possible to use piezoelectric ceramics such as BaTiO ₃ .

When a piezoelectric body is used as the vibrator 1, it is possible to adopt a configuration in which electrodes are provided instead of the piezoelectric bodies 3 and 4. As the permanent magnet 4, a rare earth magnet (for example, NEOMAX made by Sumitomo Special Metals) can be used. For example, a permanent magnet other than the samarium cobalt (SmCo) magnet or the rare earth magnet can be used.

As the detection coil 5, for example, a copper wire having a wire diameter of 20 μm and 100 turns wound in a circle having a diameter of 5 mm can be used. The material, wire diameter, coil shape and number of turns are as follows. What is necessary is just to select suitably according to detection sensitivity, cost, etc.

In this embodiment, the center of the detection coil 5 is hollow, but the sensitivity of the detection coil 5 can be improved by providing a core made of a highly permeable material such as Sendust or Permalloy.

In this embodiment, the detection coil 5
Although the magnetic pole of the permanent magnet 4 on the surface opposite to the above is an N pole, it may be an S pole. The distance between the detection coil 5 and the permanent magnet 4 can be, for example, 0.1 mm, but may be in the range of about 0.05 to 3 mm.

In this embodiment, a permanent magnet having a square pole shape is used, but other shapes such as a columnar shape and a polygonal column shape may be used.

In the present embodiment, the vibrator 1 is excited by the driving piezoelectric body 2 in the x direction. The feedback piezoelectric element 3 outputs a feedback signal for driving at a resonance frequency of the vibrator by the control circuit.

When an angular velocity Ω about the z-axis is applied, a Coriolis force proportional to the angular velocity Ω is generated in the y direction.
The vibrator 1 also vibrates in the y direction.

Since the vibrator 1 is provided with the permanent magnet 4, the magnetic flux passing through the coil changes in the detecting coil 5, and the time change of the magnetic flux changes the electromotive force of electromagnetic induction. The angular velocity Ω is detected.

In the case of the present embodiment, the Coriolis force is detected by the detection coil 5 in the same phase or in the opposite phase as the feedback piezoelectric body 3, so that synchronous detection is performed by the output signal of the feedback piezoelectric body 3. , Angular velocity can be detected.

Since the permanent magnet 4 is excited in the x direction, strictly speaking, the magnetic flux passing through the detection coil 5 may be changed by the vibration in the x direction. However, when compared to the change in magnetic flux due to vibration in the y direction, it is very small and negligible.

In the vibration gyro sensor, the resonance frequency in the driving direction of the vibrator and the resonance frequency in the detection direction for detecting the Coriolis force need to be close to each other in order to increase the detection sensitivity. However, as these resonance frequencies approach, mechanical leakage coupling in each vibration direction occurs,
For example, even when driving vibration occurs in the x-axis direction, the vibration direction is a vibration in a direction having a certain angle with respect to the x-axis, and the vibration is in a direction indicated by an arrow DA in FIG.

In this case, an output called a null voltage is detected from the detection coil 5 even when no angular velocity is applied. Therefore, it is necessary to separate the null voltage and the output due to the Coriolis force. In the present embodiment, a method and configuration for canceling the null voltage and detecting only the output by the Coriolis force will be described.

FIG. 3 shows waveforms at various parts of the detection circuit of the angular velocity sensor shown in FIGS. 1 and 2.
3A shows an output waveform during non-rotation, and FIG. 3B shows an output waveform during rotation.

In the case of the vibrator 1 oscillating in the direction of the arrow DA in FIG. 2, the drive signal during non-rotation, the feedback piezoelectric signal,
The null voltage signals of the detection coil 5 are respectively shown in FIG.
(1), (2) and (3).

In the present embodiment, the null voltage signal of the detection coil 5 has the same phase as the drive signal, so that the output of the detection coil 5 and the drive signal are differentiated by a differential circuit. As shown in (4) of FIG. 3A, the null voltage can be apparently reduced to zero.

At this time, in order to match the output level of the detection coil 5 and the output level of the drive signal, both or one of the detection coil 5 and the drive signal is passed through the gain adjustment circuit and passed through the differential circuit. What is necessary is just to adjust so that the subsequent output becomes zero.

In this embodiment, the detection coil 5
The polarity of the magnet 4 and the winding direction of the detection coil are matched in consideration of the vibration direction due to the leakage coupling of the vibrator so that the phase of the drive signal coincides with the phase of the drive signal. However, when the phase of the detection coil 5 and the phase of the drive signal are opposite to each other, a configuration may be adopted in which a circuit for taking a summation is provided instead of the differential circuit 31.

Next, when the angular velocity sensor 10 rotates, as shown in (3) of FIG. 3B, the output due to the Coriolis force has a 90 ° phase shift from the null voltage of the detecting coil. Occurs in position. Therefore, (4) in FIG.
As shown in (2), only the output due to the Coriolis force is detected as the output from the differential circuit.

Since the phase coincides with the phase of the piezoelectric signal for feedback, the output of the differential circuit is synchronously detected with the output of the piezoelectric material for feedback and then smoothed, thereby obtaining (5) in FIG. As shown in (6) and (6), only signals due to Coriolis force can be extracted.

Here, when the signal noise of the detection coil 5 was measured, it was 8 nV / √Hz. This noise was three orders of magnitude or more smaller than the noise of a piezoelectric body used for detection by a conventional piezoelectric gyro. Further, the noise of the drive signal is equivalent to the amplifier noise, and is 1 nV / √H.
z, as in the present embodiment, the detection coil 5
If the above signal is differentiated by the driving signal, a very small noise detection signal can be obtained.

When the noise of the detection signal of the conventional piezoelectric gyro was measured, it was 2 mV. However, in the gyro sensor of this embodiment, it was 0.8 μV, and the noise of the detection signal of this embodiment was small by three digits or more.

As described above, in the present embodiment, compared with the case where the piezoelectric signal is differentially determined by the drive signal as in the related art,
Since a very small noise detection signal can be obtained, an angular velocity sensor having high resolution can be realized.

In other words, in the present embodiment, a signal with low noise can be obtained by differentially detecting a detection signal from a coil with low noise with a drive signal having low noise. At this time, since the phase of the feedback signal and the signal component generated by the Coriolis force match,
By performing synchronous detection with the feedback signal, a signal component generated by Coriolis force can be separated. At this time, since the signal from the piezoelectric body for feedback is used only for extracting a signal (gate signal) for synchronous detection, even a signal with relatively large noise from the piezoelectric body is used. The influence of noise on the output of the angle sensor is small.

In this embodiment, a cantilevered vibrator is used as the vibrator 1, but a vibrator of a tuning fork type, an H type, or the like can be used. Further, in this embodiment, the vibrator having the magnet attached to the free end is used. However, as the vibrator, a magnetic material having a magnetization direction in a direction orthogonal to the driving vibration direction can be used. In this embodiment,
Although the piezoelectric body is used as the driving means, a method in which a magnet and a driving coil are provided on the side of the vibrator on the driving vibration side and the vibrator is excited by electromagnetic induction is also possible.

[Second Embodiment] FIG. 4 is a schematic block diagram showing a configuration of an angular velocity sensor according to a second embodiment of the present invention.

In FIG. 4, the vibration gyro sensor section is shown in a plan view. Referring to FIG. 4, the angular velocity sensor unit 10 includes a vibrator 1, a driving piezoelectric body 2, a feedback piezoelectric body 3, a permanent magnet 4, and detection coils 5a and 5b.

In the second embodiment, the detection coil 5
Is the same as the configuration of the angular velocity sensor of the first embodiment except that two are provided symmetrically with respect to the x-axis with the vibrator 1 interposed therebetween. Therefore, the same parts are denoted by the same reference numerals, and the description thereof will be repeated. Absent.

In the second embodiment, the detection coils 5a and 5a
The winding direction of the detection coil and the polarity of the magnet 4 are matched in consideration of the vibration direction due to the leakage coupling of the vibrator so that the phases of the three signals b and the drive signal match.

In the second embodiment, since the sum of the signals of the detection coils 5a and 5b is obtained by the summing circuit 34, the null voltage output from the detection coil is doubled.

When the angular velocity sensor 10 rotates, the output due to the Coriolis force is generated in the detection coils 5a and 5b at positions shifted from the null voltage phase by 90 °, respectively. By taking the action, it is possible to extract only the output due to the Coriolis force. Further, since there are two detection coils, the angular velocity can be detected at twice the size. Since the method of synchronous detection and the signal noise of the detection coil are the same as in the first embodiment, description thereof will not be repeated.

In this embodiment, the detection coils 5a and 5a
When the signal b is in the opposite phase, the differential is obtained at the summing circuit 34. When the signal is in phase with the drive signal, the differential is obtained at the differential circuit 31. Should be summed up at the differential circuit 31.

In this embodiment, a cantilevered vibrator is used as the vibrator 1, but a vibrator of a tuning fork type, an H type, or the like may be used.

In the second embodiment, a vibrator having a magnet attached to the free end is used. However, as the vibrator, a magnetic material having a magnetization direction in a direction perpendicular to the driving vibration direction can be used. .

In the second embodiment, a piezoelectric body is used as the driving means. However, a method is used in which a magnet and a driving coil are provided on the side of the vibrator on the driving vibration side, and the vibrator is excited by electromagnetic induction. Can also.

[Third Embodiment] FIG. 5 is a schematic block diagram showing a configuration of an angular velocity sensor according to a third embodiment of the present invention.

In FIG. 5, the vibrating gyro part is shown in a plan view. Referring to FIG. 5, the angular velocity sensor unit 10 includes a vibrator 1, a driving piezoelectric body 2, a feedback piezoelectric body 3,
It comprises a permanent magnet 4 and detection coils 5c and 5d.

In the third embodiment, the cross section of the vibrator is triangular, and two detecting coils are provided symmetrically with respect to the x-axis, which is the driving vibration direction, at an angle of less than 90 ° and x-axis. Is the same as the configuration of the angular velocity sensor of the first embodiment, and therefore the same portions are denoted by the same reference characters and description thereof will not be repeated.

In the third embodiment, the vibrator 1 is excited by the driving piezoelectric body 2 in the x direction. The feedback piezoelectric body 3 is provided on the same side surface of the vibrator as the drive piezoelectric body is provided, and outputs a feedback signal for driving the vibrator 1 at the resonance frequency by the self-excited oscillation circuit 30. That is, the feedback piezoelectric element 3 is provided on a plane orthogonal to the direction in which the vibrator 1 is driven.

When an angular velocity Ω about the z-axis is applied, a Coriolis force proportional to the angular velocity Ω is generated in the y direction.
The vibrator 1 also vibrates in the y direction. Since the vibrator 1 is provided with the permanent magnet 4, the detection coil 5
In c and 5d, the magnetic flux passing through the coil changes, and the time change of the magnetic flux changes the electromotive force of electromagnetic induction, and the angular velocity Ω is detected.

In the case of the third embodiment, the Coriolis force is detected by the detection coil 5 in the same phase or in the opposite phase as the feedback piezoelectric element 3, so that synchronous detection is performed by the output signal of the feedback piezoelectric element 3. , Angular velocity can be detected.

In the third embodiment, a method for detecting only the output based on the Coriolis force will be described below.

FIG. 6 is a timing chart showing waveforms at various parts of the angular velocity sensor shown in FIG.
FIG. 6A shows the waveforms at the time of non-rotation, and FIG.

In the case of the vibrator 1 which is driving and vibrating, the driving signal during non-rotation, the piezoelectric signal for feedback, and the null voltage signal of the detecting coils 5a and 5b are respectively represented by (1) in FIG. (2), (3) and (4). In the present embodiment, the null voltage signal of the detection coil 5c has the same phase as the null voltage signal of the detection coil 5d, so that the differential circuit makes the differential between the output of the detection coil 5c and the detection coil 5d. , The null voltage can be apparently reduced to zero as shown in (5) of FIG.

At this time, the detection coils 5c and 5d
The detection coils 5c and 5c
It suffices to pass both or one of d through a gain adjustment circuit and adjust the output after passing through the differential circuit to zero.

In the third embodiment, the detection coil 5
The winding direction of the detection coil and the polarity of the magnet 4 are matched so that the phases of the signals c and 5d match. However, when the phases of the detection coils 5c and 5d are opposite to each other, a configuration may be adopted in which a summing circuit is used instead of the differential circuit 31.

Next, when the angular velocity sensor 10 is rotated, as shown in (3) and (4) of FIG. 6B, the output due to the Coriolis force becomes the null voltage of the detection coils 5c and 5d, It occurs at positions advanced and delayed by 90 ° phase, respectively.

Therefore, as shown in (5) of FIG. 6 (b), as for the output from the differential circuit, only the output due to the Coriolis force is detected. The phase of the feedback piezoelectric element 3
Therefore, the output of the differential circuit is synchronously detected with the output of the piezoelectric element for feedback 3 and then smoothed, as shown in (6) of FIG. Only signals by force can be extracted.

As shown in the third embodiment, by taking the differential between the outputs from the detection coil with low noise,
The detection signal of the Coriolis force has low noise, and an angular velocity sensor having high resolution can be obtained.

Further, in the present embodiment, since the driving piezoelectric body 2 is provided on the surface orthogonal to the driving vibration direction, not only the driving efficiency is high but also the driving vibration is hardly disturbed. effective.

In this embodiment, a cantilevered vibrator is used as the vibrator 1, but a vibrator of a tuning fork type, an H type, or the like may be used. Further, in the present embodiment, the piezoelectric body is used as the driving means, but it is also possible to adopt a method in which a magnet and a driving coil are provided on the side of the vibrator on the driving vibration side, and the vibrator is excited by electromagnetic induction. It is.

In FIG. 5, the cross-sectional shape of the vibrator is triangular. In general, if the vibrator has a polygonal cross-sectional shape having an odd number of three or more vertices, it is orthogonal to the driving direction. It is easy to provide a detecting means for feedback, for example, a piezoelectric body on the surface.

[Fourth Embodiment] FIG. 7 is a schematic block diagram showing a configuration of an angular velocity sensor according to a fourth embodiment of the present invention.

In FIG. 7, the angular velocity sensor unit 10
This is shown by a plan view. Referring to FIG. 7, the angular velocity sensor unit 10 includes a vibrator 1, driving piezoelectric bodies 2a and 2b, a feedback piezoelectric body 3, a permanent magnet 4, and detection coils 5c and 5c.
d.

The fourth embodiment is basically the same as the third embodiment except that the cross section of the vibrator is triangular and two driving piezoelectric members are provided on the side surfaces. Therefore, the same portions are denoted by the same reference characters and description thereof will not be repeated.

Therefore, also in the fourth embodiment, the angle between the surfaces on which the permanent magnets are provided may be less than 90 degrees.

In the fourth embodiment, the driving piezoelectric body 2
Since two a and two b are provided, one on each side,
When the direction of the drive vibration deviates from the x-axis direction, by adjusting the magnitude and balance of the drive voltage supplied to the driving piezoelectric bodies 2a and 2b, the drive vibration direction can be made to coincide with the x-axis direction. The deviation of the driving vibration direction from the x-axis direction can be adjusted by feeding back the outputs of the detection coils 5c and 5d.

As described above, the direction of the driving vibration can be adjusted by the magnitude and balance of the driving voltage from the driving piezoelectric bodies 2a and 2b. Therefore, even when the balance of the vibrator is poor, the driving vibration can be easily performed. The direction can be adjusted, and an angular velocity sensor with high detection sensitivity can be obtained.

Also, in FIG. 7, the cross-sectional shape of the vibrator is triangular, but in general, if the vibrator has a polygonal cross-sectional shape having an odd number of three or more vertices, it is orthogonal to the driving direction. It is easy to provide a detecting means for feedback, for example, a piezoelectric body on the surface.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0090]

As described above, in the angular velocity sensor according to the present invention, the vibration caused by the Coriolis force orthogonal to the driving vibration direction is detected by the detecting coil. This can be offset by taking the differential with The detection signal of the coil is noise that is smaller than the signal by the conventional piezoelectric body by three digits or more, and the noise of the drive signal is also small, so that a low-noise angular velocity detection output can be obtained. Therefore, an angular velocity sensor with high resolution can be obtained.

Further, two detection coils are provided, and the coil surfaces of these detection coils have a predetermined angle with the driving vibration direction and have the surface of the coil so as to be orthogonal to the magnetization direction of the permanent magnet. In such a case, the null voltage can be canceled by taking the difference between the signals of the two detection coils, so that a low-noise angular velocity detection output can be obtained, and a high resolution can be obtained. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration of an angular velocity sensor according to Embodiment 1 of the present invention.

FIG. 2 is a schematic block diagram illustrating a configuration of an angular velocity sensor according to Embodiment 1 of the present invention.

FIGS. 3A and 3B are timing charts showing detection waveforms of the angular velocity sensor according to the first embodiment of the present invention. FIG. 3A shows a waveform at the time of non-rotation, and FIG. 3B shows a waveform at the time of rotation.

FIG. 4 is a schematic block diagram illustrating a configuration of an angular velocity sensor according to Embodiment 2 of the present invention.

FIG. 5 is a schematic block diagram illustrating a configuration of an angular velocity sensor according to Embodiment 3 of the present invention.

6A and 6B are timing charts showing detection waveforms of the angular velocity sensor according to Embodiment 3 of the present invention. FIG. 6A shows a waveform at the time of non-rotation, and FIG. 6B shows a waveform at the time of rotation.

FIG. 7 is a schematic block diagram illustrating a configuration of an angular velocity sensor according to Embodiment 4 of the present invention.

FIG. 8 is a schematic block diagram showing a configuration of a first conventional angular velocity sensor.

FIG. 9 is a schematic block diagram showing a configuration of a second conventional angular velocity sensor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 vibrator 2 driving piezoelectric element 3 feedback piezoelectric element 4 permanent magnet 5, 5 a to 5 d detecting coil 30 self-excited oscillation circuit 31 differential circuit 32 synchronous detection circuit 33 smoothing circuit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tomohisa Koda 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside (72) Inventor Toru Kira 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka F term (reference) 2F105 AA02 AA08 BB03 BB14 CC04 CC05 CC06 CD01 CD06 CD11

Claims (8)

[Claims] 1. An angular velocity sensor, comprising: a vibrator; at least one permanent magnet provided near a free end of the vibrator; driving means for driving the vibrator in a driving direction; And at least one detection device arranged in a direction perpendicular to the vibration direction for detecting vibration in a direction perpendicular to the vibration direction of the vibrator excited by the driving means. And a differential circuit that takes a difference between a null voltage and a drive signal generated in the detection coil, and a synchronous detection circuit that detects an output signal of the differential circuit with a signal from the feedback detection unit. An angular velocity sensor comprising: 2. An angular velocity sensor, comprising: a vibrator; at least two permanent magnets provided near a free end of the vibrator; driving means for driving the vibrator in a driving direction; Feedback detecting means for detecting the vibration, and at least two detection coils for detecting vibration in a direction orthogonal to the vibration direction of the vibrator excited by the driving means, wherein the detection coil is The vibration direction of the vibrator excited by the driving means and the coil surface have an angle of less than 90 °, and are arranged so as to have the surface of the coil so as to be orthogonal to the magnetization direction of the permanent magnet. A differential circuit for canceling the voltage generated by the vibration in the driving direction of the vibrator in the detection coil by taking the differential of the voltage generated in another detection coil; and Degree in, further comprising an angular velocity sensor and a synchronous detection circuit for detecting an output signal of the differential circuit. 3. An angular velocity sensor, comprising: a columnar vibrator having a polygonal cross section; at least two permanent magnets provided near a free end of the vibrator; and exciting the vibrator in a driving direction. Driving means, feedback detecting means for detecting the excitation state, at least two detection coils for detecting vibration in a direction orthogonal to the vibration direction of the vibrator excited by the driving means, The detection coil is disposed so as to have a coil surface orthogonal to the magnetization direction of the permanent magnet, and a voltage generated by the vibration of the vibrator in the drive direction is applied to the detection coil by another voltage. A differential circuit that takes a differential of a voltage generated in the detection coil and cancels out, and a signal from the feedback detection unit, and further includes a synchronous detection circuit that detects an output signal of the differential circuit. Speed sensor. 4. The angle sensor according to claim 3, wherein the polygon shape has an odd number of three or more vertices. 5. The vibrator provided with at least one permanent magnet near the free end is a magnetic material magnetized in a direction orthogonal to a vibration direction of the vibrator excited by the driving means. The angular velocity sensor according to claim 1. 6. The driving means for exciting the vibrator,
The angular velocity sensor according to any one of claims 1 to 5, further comprising a piezoelectric body. 7. The driving means for exciting the vibrator,
The angular velocity sensor according to claim 1, further comprising a coil. 8. The angular velocity sensor according to claim 1, wherein said feedback detecting means for detecting said excitation state includes a piezoelectric body.