JPH08201068A - Angular velocity sensor - Google Patents

Abstract

PURPOSE: To obtain an angular speed sensor for detecting the angular speeds on two axes. CONSTITUTION: An exciting electrode 4 is disposed in the center on the upper surface of a oscillation substrate disc 2 and two pairs of detection electrodes 6, 7, intersecting at the center of a disc 1, are disposed point symmetrically thereto at the outer circumferential part of the exciting electrode 4. A piezoelectric disc element 3, provided with electrodes facing at least the electrodes 6, 7, is pasted to the lower surface of the oscillation substrate disc 2. The oscillation substrate 2 is provided, in the center on the lower surface thereof, with a feedback electrode 10. A weight 16 is supported at the sensor part pasted with the piezoelectric element disc 1 provided, on the upper surface thereof, with electrodes facing at least the feedback electrode 10.

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.

[0002]

2. Description of the Related Art An angular velocity sensor capable of attitude control and position control has been developed to have a smaller size and higher performance for the purpose of preventing camera shake of a video camera and being used for car navigation. Although there are various angular velocity sensors, the piezoelectric vibration type angular velocity sensor is advantageous in terms of size and cost, and tuning fork type, tuning piece type (square column), columnar type, triangular prism type and the like have been commercialized.

FIG. 1 is a structural diagram for explaining a sound piece type piezoelectric vibration angular velocity sensor. The principle of the piezoelectric vibration type angular velocity sensor is that when the rotation angular velocity (ω0) is applied around the center axis (Z axis) of the vibrating vibrator, the original vibration direction (X axis)
On the other hand, it utilizes a mechanical phenomenon in which a Coriolis force (Fc) proportional to the rotational angular velocity is generated in the direction perpendicular to the axis (Y axis), and vibration is applied to the X axis by using a driving piezoelectric ceramic, and detection provided on the Y axis. The piezoelectric ceramics for use detects Coriolis force as a voltage. Coriolis force is generally obtained by the following equation. Fc = 2m × v × ω0 m is mass, v is velocity, and ω0 is angular velocity.

If the vibration frequency is the same, the larger the X-axis amplitude is, the larger the Y-axis displacement is, and the higher the detection voltage (sensitivity) is, the larger the X-axis amplitude is and the higher the Y-axis detection efficiency is, the resonance type vibration. An angular velocity sensor is advantageous. The speech piece type vibration angular velocity sensor is a resonance type and can have high sensitivity, but it is difficult to accurately adjust the resonance frequency without disturbing the vibration posture of the drive side and the detection side, and the resonance characteristics of the drive side and the detection side. Characteristic change and high mechanical quality factor (Q
Due to m), there are many problems such as slow response speed. As an angular velocity sensor that solves the above-mentioned problem, not a separate structure of a driving side and a detecting side but a single side (body) for driving and detecting makes it possible to perform driving and detection by the same resonance system. A product has been developed that constitutes an angular velocity sensor and overcomes the problems of mismatch and deviation in resonance characteristics.

FIG. 2 is a structural diagram of an equilateral triangular sound piece type vibration angular velocity sensor. The resonance frequency fΔ of the equilateral triangular tone piece oscillator having one side a and the length l can be obtained by the equation 1.

[0006]

## EQU1 ## m is a constant, E is Young's modulus, and ρ is density. The oscillator was made of a constant elastic metal material (elinvar material), and piezoelectric ceramics were attached to the center of each side with an epoxy adhesive. The node points were obtained by simulation by the finite element method, and ideal support was performed at the ridge line portion corresponding to the complete node point in the Y-axis mode. Also, in consideration of the negative thermoelastic coefficient of the piezoelectric ceramics to be combined, the aging treatment using the precipitation effect of the elinvar material is applied, and in combination with the positive elastic coefficient, the frequency temperature characteristic is a good characteristic of ± 1 ppm / ° C or less. The detection voltage of the vibrator itself is several hundred mV, which is a very high sensitivity (high output), which is far higher than that of the conventional non-resonant vibration angular velocity sensor. (Journal of the Institute of Electronics, Information and Communication Engineers, 1 / '93,
Piezoelectric vibration gyroscope, Takeshi Nakamura)

[0007]

The frequency temperature characteristic is good, and the high-sensitivity angular velocity sensor is useful as an angular velocity sensor for camera shake prevention of a camera-integrated video camera.
There is a drawback that only one sensor can detect the angular velocity of one axis, and two sensors are required to detect the angular velocity of two axes, which inevitably increases the number of assembly steps and the number of assembly parts. If it has two axes, the cost will be doubled even if it is simply viewed.

[0008]

SUMMARY OF THE INVENTION The present invention is to solve the problems of the conventional angular velocity sensor, has a small size,
An inexpensive angular velocity sensor with high sensitivity is provided.

Piezoelectric elements having electrodes on both sides are attached to both sides of the vibration substrate. The piezoelectric element attached to the upper surface is provided with an excitation electrode in the central portion on the upper surface and four detection electrodes (two pairs of detection electrodes orthogonal to each other at the center of the disk-shaped vibrating substrate) on the outer periphery thereof. At least an electrode facing the excitation electrode and the detection electrode is provided on the lower surface (surface attached to the vibration substrate), and the piezoelectric element is polarized so that positive charges are generated in the excitation electrode when the excitation electrode side extends. The detection electrode is arranged inside the vibration node of the diaphragm, the extraction electrode is extended from the excitation electrode and each detection electrode to the vibration node, and each electrode is connected to the circuit on the vibration node.

In the piezoelectric element to be attached to the lower surface, at least the electrode facing the lower electrode is provided on the surface (upper surface) to be attached to the vibrating substrate, and the return electrode is provided at the central portion on the lower surface. A weight body is provided in the sensor unit having the above-described configuration. The vibration node portion of the sensor is fixed to the opening of the cylindrical member.

When alternating current is applied to the excitation electrode and the counter electrode of the piezoelectric element, the piezoelectric element vibrates, and the vibrating substrate attached thereto also vibrates. Electric charges are generated in the detection electrode due to the distortion of the piezoelectric element. Since the opposite detection electrodes are connected with their polarization directions reversed, the generated charges are canceled in the excited state. When angular velocity acts on the sensor in a vibrating state, Coriolis force is generated in the sensor section and the distortion of the sensor section changes.
A charge is generated on the detection electrode. Since the sensor unit is provided with the weight body, the mass m becomes large and the Coriolis force generated becomes large.

[0012]

3 is a side sectional view of an angular velocity sensor according to a first embodiment of the present invention, FIG. 4 is a top view and FIG. 5 is a bottom view. FIG. 6 is a side sectional view of the angular velocity sensor of the second embodiment of the present invention, and FIG. 7 is a bottom view. The reference numerals are the same in FIGS. 3, 4, and 5. FIG. 8 is a circuit diagram for exciting the angular velocity sensor of the present invention.

First, the first embodiment will be described. A piezoelectric element such as a piezoelectric ceramic (PZT) disk 1
An excitation electrode 4 having an extraction electrode 4a and four detection electrodes 6, 7, 8 and 9 are formed on the upper surface of the. Each detection electrode has extraction electrodes 6a, 7a, 8a, 9a. The four electrodes are symmetrically and concentrically formed on the X axis and the Y axis as shown. (In the present embodiment, it is concentric, but it does not have to be concentric but may be point-symmetric.)
Are formed with a diameter facing the outer circumference of the detection electrodes 6, 7, 8 and 9. The forming method may be vacuum vapor deposition, sputtering, etc., and the electrode film thickness in this embodiment is 4500 angstroms.

After the electrodes are formed, the piezoelectric ceramics are polarized. There are two types of polarization: the electrodes 4, 6, 8 are positive and the electrodes 5 are negative, and the electrodes 7, 9 are negative and the electrodes 5 are positive. Do it in two steps. Detection electrodes 6 and 7
The detection electrodes 8 and 9 are connected on a sensor (a connection pattern is formed on the piezoelectric ceramics) or by a detection circuit to form a pair of X-axis and Y-axis angular velocity detection electrodes. Due to the above-mentioned polarization, opposite charges are generated in the pair of detection electrodes. Therefore, in the state in which the Coriolis force does not act (the state in which the angular velocity does not act), the mutually generated charges cancel each other out. The return electrode 10 is provided on the upper surface of the piezoelectric ceramic (PZT) disk 3.
An electrode 11 is formed so as to be opposed to, and a return electrode 10 is formed in the center on the lower surface. For polarization, electrode 10 is electrode 4
Do the same direction as. In this embodiment, the excitation electrode and the return electrode are set to +, but both electrodes may be -polarized. Piezoelectric ceramics has an outer diameter of 20 mm and a thickness of 0.1 m
m, the excitation electrode and the return electrode have a diameter of 9 mm, the detection electrode has an inner diameter portion of 10 mm and an outer diameter portion of 12 mm. The weight body has a diameter of 3 mm and a length of 3 mm.

The vibrating substrate 2 is a metal plate having a small thermal expansion coefficient at room temperature and a thickness of 0.1 mm (for example, Super-Inva).
r "Handbook of Steel Materials" edited by The Japan Institute of Metals and Japan Iron and Steel Institute), and piezoelectric ceramics 1 and 3 are attached on both sides as shown in the figure. Although the adhesive is not shown, for example, LID1316 (UV anaerobic adhesive) manufactured by Loctite Co., Ltd. may be applied to the piezoelectric ceramic side, and Primer 7649 (reaction accelerator) manufactured by Loctite Co. may be applied to the metal plate side for adhesion.
It cures when exposed to UV light after adhesion. Similarly, the weight body 16
Is also glued.

Since the electrode 5 and the vibrating substrate 2 are electrically connected and bonded to each other, when an alternating current is applied to the vibrating substrate 2 and the exciting electrode 4, the piezoelectric ceramic 1 vibrates and the vibrating substrate 2 vibrates together. When supported by a cylindrical support member, the vibration node is shown in FIG.
In the vicinity of the dotted line 13 (when the outer diameter of the vibration substrate 2 is D, 0.5
There is a small generated stress in the 4 to 0.70D part)
Therefore, it is supported by the opening (preferably a knife edge) of the cylindrical support member 12. FIG. 12 is a graph showing the relationship between the cylindrical support diameter and the stress generated in the support portion. Although the stress generated by the vibrating substrate, the piezoelectric element, and the electrodes changes, a small generated stress appears in the vicinity of 0.54 to 0.70D. The vibration used in this embodiment is the radial vibration of the piezoelectric ceramics, and when it is supported, it becomes so-called bending vibration. The diameter of the supporting portion is 10.8 to 14.0 m
m. By supporting near the vibration node, vibration leakage can be reduced. The detection electrode is provided inside the cylindrical support. It should be noted that the sensor unit may be supported either upside or downside.

The angular velocity sensor is connected to the feedback circuit shown in FIG. The feedback electrode 10 is connected to the amplifier 14. Amplifier 1
The output of 4 is input to the phase correction circuit 15, and the phase correction circuit 1
The output of 5 is connected to the excitation electrode 4. The signal obtained at the feedback electrode 10 is amplified by the amplifier 14 and has a phase of 1
It becomes a rectangular wave inverted by 80 degrees. Square wave is phase correction circuit 1
At 5, the phase is delayed by 90 degrees. Further, the piezoelectric element of the angular velocity sensor delays the phase by 90 degrees and is extracted as a signal from the feedback electrode 10. (The weight body is omitted in the figure)

When the angular velocity acts on the angular velocity sensor, Coriolis force is generated in the weight body, and the piezoelectric element of the angular velocity sensor is deformed due to the Coriolis force. The voltage obtained at the detection electrodes 6, 7, 8 and 9 changes, and the angular velocity acting on the X axis and the Y axis can be detected.

Next, a second embodiment will be described with reference to FIGS. 6 and 7. The second embodiment is different from the first embodiment in that the electrodes 5 and 11 are full-scale electrodes and that the detection electrodes 6 ',
7 ', 8', 9'is also provided around the return electrode. In FIG. 6, electrodes 6'and 7'are upper electrodes 6 and 7
Are arranged opposite to each other and the polarization is reversed. The same applies to the detection electrodes 8'and 9 '. FIG. 11 is a connection diagram of the detection electrodes, but the detection sensitivity is doubled by providing and connecting the detection electrodes on both sides.

Next, the theory by which the angular velocity can be detected in the present invention will be described. FIG. 9 is a side sectional view of a state in which the angular velocity ω acts around the Y axis. When the weight body moves due to the Coriolis force, the sensor section is deformed and the detection electrodes 6, 6 ′,
Positive and negative charges are generated in 7 and 7'as shown in the figure. That is, the electrode 6 is pulled positive and the electrode 6'is
Is compressed, but the polarization is reversed, so that positive is generated, and similarly, negative is generated in the electrodes 7 and 7 '.

FIG. 10 is a block diagram of a circuit for detecting the angular velocity from the generated charges. It is a circuit block diagram for detecting the Coriolis force proportional to the rotational angular velocity in the X-axis direction and the Y-axis direction. However, since the same signal processing is performed for both the X-axis and the Y-axis, the case where the Coriolis force is generated in the X-axis direction is taken as an example. I will explain (Y
When the angular velocity of rotation acts around the axis). Detection electrode 6,
Reference numerals 7, 8 and 9 are connected to an impedance conversion circuit, and the output of the impedance conversion circuit is connected to an addition circuit (not necessary when a pair of detection electrodes are connected on the angular velocity sensor).

A drive signal is applied through the amplifier circuit 14 and the phase correction circuit 15 to excite the sensor section. Detection electrode 6,
Since 7 is polarized in the opposite direction, the output drive signal is 180 degrees out of phase. (Fig. 11
In the case of the wiring, the terminals 6 and 6'and the terminals 7 and 7'can be considered in the same manner.) When rotation is applied in this state, the charge generated by the Coriolis force proportional to the rotation angular velocity is a driving signal as a voltage. Superimpose on. At this time, since the detected voltages that are opposed to each other due to the Coriolis force have the same phase, a difference occurs in the voltage outputs like the output voltages 17 and 18. When added by the adder circuit 19, the drive signals are canceled and only the voltage 20 generated by the Coriolis force can be taken out. The voltage generated by this Coriolis force is half-wave rectified by the synchronous detection circuit 21, and an output voltage 22 is obtained. This output voltage is smoothed by the DC amplification circuit 23, and the output voltage 24 proportional to the rotational angular velocity is obtained.

[0023]

EFFECTS OF THE INVENTION The present invention having the above-mentioned structure has the following effects. 1 One sensor can measure angular velocities on two axes. 2 A combination of a disk-shaped flat plate and a cylinder, which is easy to process and assemble. 3 Since the sensor part is supported by the cylinder, it can be firmly supported, and the reliability of the angular velocity sensor is high. 4 By attaching a weight body, the action of Coriolis force increases and detection becomes easier. Polarization of the five pairs of detection electrodes is performed twice and the polarization directions are reversed, so that the connection structure and the detection circuit can be simplified (the addition circuit can be omitted).

[Brief description of drawings]

FIG. 1 is a structural diagram for explaining a sound piece type piezoelectric vibration angular velocity sensor.

FIG. 2 is a structural diagram of an equilateral triangular sound piece type vibration angular velocity sensor.

FIG. 3 is a side sectional view of the angular velocity sensor according to the first embodiment of the present invention.

FIG. 4 is a top view of the angular velocity sensor of the first embodiment of the present invention.

FIG. 5 is a bottom view of the angular velocity sensor of the first embodiment of the present invention.

FIG. 6 is a side sectional view of an angular velocity sensor according to a second embodiment of the present invention.

FIG. 7 is a bottom view of the angular velocity sensor according to the second embodiment of the present invention.

FIG. 8 is a circuit diagram for exciting the angular velocity sensor of the present invention.

FIG. 9 is a state diagram for explaining the theory of the present invention.

FIG. 10 is a block diagram of an angular velocity detection circuit.

FIG. 11 is a connection diagram of detection electrodes.

FIG. 12 is a graph showing the relationship between the cylindrical support position and the generated stress.

[Explanation of symbols]

 1 Ceramic Disc 2 Metal Plate 3 Ceramic Disc 4 Excitation Electrode 4a Extraction Electrode 5 Electrode 6, 6'Detection Electrode 7, 7'Detection Electrode 6a Extraction Electrode 7a Extraction Electrode 8a Extraction Electrode 9a Extraction Electrode 8,8 'Detection Electrode 9 , 9 ′ detection electrode 10 feedback electrode 11 electrode 12 support member 13 vibration node 14 amplifier 15 phase correction circuit 16 weight body 17 output voltage waveform 18 output voltage waveform 19 addition circuit 20 voltage waveform 21 synchronous detection circuit 22 output voltage waveform 23 DC amplification circuit 24 Output voltage waveform

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomio Namiki 4107, Miyota, Miyota-cho, Kitasaku-gun, Kitano, Nagano 5 Miyota Co., Ltd. (72) Riyasu Shigeta 4107, 5107 Miyota, Kitadaku-cho, Kitasaku-gun, Nagano Prefecture In Miyota Co., Ltd. (72) Minor Hatakeyama Minoru Hatakeyama 4107, Miyota, Miyota-cho, Kitasaku-gun, Nagano 5 In Miyota Co., Ltd. (72) Inventor, Kazuhiro Okada 4-73, Sugaya, Ageo City, Saitama Prefecture

Claims (4)

[Claims] 1. An excitation electrode is provided on the upper surface of a disk-shaped vibrating substrate at the center of the upper surface, and two pairs of detection electrodes, which are orthogonal to each other at the center of the disk, are provided on the outer peripheral portion of the excitation electrode with respect to the center of the disk. A disk-shaped piezoelectric element provided with point symmetry and at least an electrode facing the electrode is attached to the lower surface, a return electrode is provided in the center of the lower surface of the vibration substrate, and at least the return electrode is provided on the upper surface. An angular velocity sensor characterized in that a weight body is provided at a central portion of a sensor portion to which a disk-shaped piezoelectric element provided with opposing electrodes is attached. 2. An excitation electrode is provided on the upper surface of a disk-shaped vibrating substrate at the center of the upper surface, and two pairs of detection electrodes, which are orthogonal to each other at the center of the disk, are provided on the outer peripheral portion of the excitation electrode with respect to the center of the disk. A disk-shaped piezoelectric element having a point symmetry and at least an electrode facing the electrode is attached to the lower surface, and a return electrode is provided on the lower surface of the vibrating substrate in the center of the lower surface. A pair of detection electrodes which are orthogonal to each other at the center of the disk and are provided point-symmetrically with respect to the center of the disk, and a disk-shaped piezoelectric element provided with at least the feedback electrode and an electrode facing the two pairs of detection electrodes on the upper surface. An angular velocity sensor characterized in that a weight body is provided on the attached sensor portion. 3. The angular velocity sensor according to claim 1 or 2, wherein the piezoelectric elements of the pair of detection electrode portions are connected with the polarization directions reversed. 4. The angular velocity sensor according to claim 1, wherein the sensor portion is supported by a cylinder.