JPH08201067A - Angular speed sensor - Google Patents

Abstract

PURPOSE: To reduce the size while enhancing the sensitivity by pasting piezoelectric elements, provided with electrodes, to the opposite sides of an oscillation substrate, disposing a detection electrode also serving as an exciting electrode (feedback electrode) on the upper surface and an electrode facing the exciting electrode on the lower surface, and disposing a weight at the sensor part. CONSTITUTION: Detection electrodes 6-9 having lead-out electrodes 6a-9a, also serving as exciting electrodes, are formed on the upper surface of a piezoelectric ceramic disc 1 having the lower surface formed with an electrode having diameter larger than that of the outer circumferential circle of the detection electrodes 6-9. A connection electrode 4 is formed between the electrode on the lower surface and the upper surface of the piezoelectric ceramic disc 1. Since the electrode on the lower surface is connected electrically with the oscillation substrate and bonded thereto, the disc 1 oscillates upon application of an AC voltage between the substrate 2 and the electrodes 6-9 thus causing oscillation of the substrate 2. When the angular speed sensor senses an angular speed, Coriolis force is generated in the weight at the sensor section and the piezoelectric element in the angular speed sensor is deformed. Consequently, the voltages at the electrodes 6-9 are varied and the angular speed can be detected on the X-axis and Y-axis.

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]

[Equation 1] 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. In addition, in consideration of the negative thermoelastic coefficient of the piezoelectric ceramics to be combined, the aging treatment utilizing the precipitation effect of the elinvar material is performed, and the elastic coefficient is combined with the positive elastic coefficient.
The frequency-temperature characteristic is ± 1 ppm / ° C or less, and the detection voltage of the oscillator itself is several hundred mV, which is an order of magnitude higher sensitivity (high output) than conventional non-resonant vibration angular velocity sensors. It was (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 a detection electrode also serving as an excitation electrode (or a return electrode) on the upper surface and at least an electrode facing the detection electrode on the lower surface (the surface attached to the vibrating substrate). The detection electrode is arranged inside the vibration node of the vibration substrate (inner diameter portion), the extraction electrode is extended from the detection electrode to the vibration node, and the electrode and the circuit are connected on the vibration node.

The piezoelectric element attached to the lower surface is provided with an electrode facing at least the excitation electrode (or the return electrode) formed on the lower surface on the surface (upper surface) attached to the vibrating substrate, and the lower surface has the excitation electrode at the center. (Or return electrode) is provided. A weight body is provided in the sensor unit having the above-described configuration. The vibration node part of the sensor part 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. When an angular velocity acts on the sensor in a vibrating state, a Coriolis force is generated in the sensor unit and the strain of the sensor unit changes, so that a charge is generated in the detection electrode by the Coriolis force. Since the sensor unit is provided with the weight body, the mass m becomes large and the Coriolis force generated becomes large.

[0012]

FIG. 3 is an exploded perspective view of an angular velocity sensor according to an embodiment of the present invention. FIG. 4 is an exploded perspective view seen from the side opposite to FIG.

On the upper surface of a disk 1 made of a piezoelectric element such as piezoelectric ceramics (PZT), an extraction electrode 6a is provided.
Four detection electrodes 6, 7, 8 having 7a, 8a, 9a,
9 is formed. The four electrodes are symmetrical on the X axis and the Y axis as shown. The electrode 11 faces the outer circumference circle of the detection electrodes 6, 7, 8 and 9 on the lower surface with respect to the center of the vibrating substrate (in the present embodiment, it is concentric, but it does not have to be concentric but point-symmetrical). The diameter is equal to or larger than the diameter. Electrode 11
A connection electrode 4 continuing from the top is formed. The electrodes are formed by vacuum vapor deposition, sputtering or the like.

After the electrodes are formed, the piezoelectric ceramics are polarized, but the four detection electrodes 6, 7, 8, 9 are positive and the electrodes 11 are
To minus.

The vibrating substrate 2 is a metal plate having a small coefficient of thermal expansion at room temperature, and the piezoelectric ceramics 1 and
3 is attached.

Since the electrode 11 and the vibrating substrate 2 are electrically connected and adhered to each other, the vibrating substrate 2 and the detecting electrodes 6, 7, 8 and 9 (6, 7, 8 and 9 are connected) also serving as the exciting electrodes. When an alternating current is applied, the piezoelectric ceramic 1 vibrates and the vibrating substrate 2 also vibrates. When the vibration node is supported by the cylindrical support member, the vibration node appears in the vicinity of the dotted line 13 in FIG. 3 (when the outer diameter of the vibration substrate 2 is D, there is a small generated stress portion at 0.54 to 0.70 D). The support member 12 is supported at the opening (preferably a knife edge). FIG. 8 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. By supporting near the vibration node, vibration leakage can be reduced. The detection electrodes 6, 7, 8 and 9 are provided inside the cylindrical support. It should be noted that the sensor unit may be supported either upside or downside. Detection electrodes 6, 7,
Although the electrodes 8 and 9 also serve as excitation electrodes and the electrode 10 serves as a feedback electrode, the detection electrode can also serve as a feedback electrode. In that case, the electrode 10 serves as an excitation electrode.

When the vibration node portion is supported in a cylindrical shape and the support member is fixed to the substrate, vibration leakage occurs due to a positional shift between the sensor portion and the support member, variations in the sensor portion and the support member, and the like. In this embodiment, the wires 14 and 1 are provided at two positions of the cylindrical support member.
The wire is fixed at 4 '(butted and laser-welded), and the other end of the wire is fixed to the substrate. FIG. 5 shows another structure for fixing the cylindrical support member and the wire. In this structure, the two wires a and b are arranged in parallel, and the cylindrical support member 12 is supported in such a manner as to sandwich the cylindrical support member 12. The part marked with X in the figure is fixed by laser welding or the like.

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. Since the sensor portion composed of the vibration substrate 2 and the piezoelectric elements 1 and 3 is not easily deformed when it is supported in a cylindrical shape, a plurality of slits 28 are provided in the vibration substrate 2 in this embodiment to facilitate deformation. FIG. 6 is a plan view showing the shape of the slit 28. Small and large slits 28 are provided in point symmetry with respect to the center point of the vibration substrate. If concavities (grooves) are provided instead of the slits 28, the concentric circles can be formed, so that the influence of the directionality of the sensor can be eliminated.

Next, FIG. 7 which is a sectional view of the second embodiment.
Will be described with reference to. The second embodiment is different from the first embodiment in that the weight body is arranged on the side opposite to the supporting member, and the cylindrical supporting member can be shortened. The weight 1 is mounted on the circuit board 15.
A hole 15a for accommodating 6 is formed, and the structure is such that the sensor as a whole can be made thin and compact.

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. As the weight moves due to the Coriolis force, the sensor section is deformed and positive and negative charges are generated on the detection electrodes 6 and 7 as shown in the figure.

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 the impedance conversion circuit, and the output of the impedance conversion circuit is connected to the differential amplifier circuit.

A drive signal is applied through the amplifier circuit 25 and the phase correction circuit 26 to excite the sensor section. Detection electrode 6,
Since 7 are polarized in the same direction, the output drive signals have the same phase. When rotation is applied in this state, electric charges generated by the Coriolis force proportional to the rotational angular velocity are superimposed on the drive signal as a voltage. 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 subtracted by the differential amplifier 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 passed through the filter 27 to obtain the output voltage 22. 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 cylindrical support member portion of the sensor portion is suspended and fixed by a wire, leakage vibration is damped, and the reliability of the angular velocity sensor is high. (4) Since the vibrating substrate is provided with slits, the sensor portion is easily deformed, the amount of electric charges generated in the piezoelectric element is increased, and each speed is easily detected. 5 By attaching a weight body, the action of the Coriolis force increases and detection becomes easier. 6. The electrode structure is simplified because it also serves as the detection electrode and the excitation electrode or the detection electrode and the return electrode. 7 By providing the weight body on the circuit side, it is possible to reduce the thickness.

[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 an exploded perspective view of the angular velocity sensor of the first embodiment of the present invention.

FIG. 4 is an exploded perspective view of the angular velocity sensor of the first embodiment of the present invention.

FIG. 5 is a perspective view showing a fixing structure of a cylindrical support member and a wire.

FIG. 6 is a plan view showing a slit shape.

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

FIG. 8 is a graph showing the relationship between the cylindrical support diameter and the stress generated in the support portion.

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.

[Explanation of symbols]

 1 Ceramic Disc 2 Metal Plate 3 Ceramic Disc 4 Electrode 5 Electrode 6 Detection Electrode 7 Detection Electrode 6a Extraction Electrode 7a Extraction Electrode 8a Extraction Electrode 9a Extraction Electrode 8 Detection Electrode 9 Detection Electrode 10 Electrode 11 Electrode 12 Support Member 13 Vibration Node 14 Wire 14 'Wire a Wire b Wire 15 Circuit board 15a Storage hole 16 Weight 17 Output voltage waveform 18 Output voltage waveform 19 Differential amplification circuit 20 Voltage waveform 21 Synchronous detection circuit 22 Output voltage waveform 23 DC amplification circuit 24 Output voltage waveform 25 Amplification circuit 26 Phase correction circuit 27 Filter 28 Slit

 ─────────────────────────────────────────────────── ─── 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 (7)

[Claims] 1. A disc-shaped piezoelectric element having a detection electrode also serving as an excitation electrode provided on the upper surface of a disc-shaped vibrating substrate, and a disc-shaped piezoelectric element provided with an electrode facing at least the electrode is attached to the lower surface of the disc-shaped vibrating substrate. A feedback electrode is provided in the center of the lower surface of the vibration substrate, and a weight body is provided in the center of the sensor section to which a disc-shaped piezoelectric element having at least an electrode facing the return electrode is attached on the upper surface. An angular velocity sensor characterized by. 2. A plurality of slits are provided inside a vibration node of a disk-shaped vibration substrate that cylindrically supports the vibration node portion,
On the upper surface of the disk-shaped vibrating substrate, a detection electrode that also serves as an excitation electrode is provided on the upper surface, and on the lower surface, a disk-shaped piezoelectric element provided with an electrode facing at least the electrode is attached, and on the lower surface of the vibrating substrate, An angular velocity sensor, characterized in that a feedback electrode is provided in the central portion of the lower surface, and a weight is provided in the central portion of a sensor portion to which is attached a disk-shaped piezoelectric element having at least an electrode facing the return electrode on the upper surface. 3. A disc-shaped piezoelectric element having a detection electrode also serving as a return electrode provided on the upper surface of the disc-shaped vibrating substrate, and a disc-shaped piezoelectric element provided with an electrode facing at least the electrode is attached to the lower surface of the disc-shaped vibrating substrate. A vibration body is provided on the lower surface of the vibration substrate at the center of the lower surface, and a weight body is provided at the center of the sensor section to which is attached a disk-shaped piezoelectric element having at least an electrode facing the excitation electrode on the upper surface. An angular velocity sensor characterized by. 4. A plurality of slits are provided inside a vibration node of a disk-shaped vibration substrate that cylindrically supports the vibration node portion,
On the upper surface of the disk-shaped vibrating substrate, a detection electrode also serving as a return electrode is provided on the upper surface, and on the lower surface, a disk-shaped piezoelectric element having an electrode facing at least the electrode is attached, and on the lower surface of the vibrating substrate, An angular velocity sensor, characterized in that an excitation electrode is provided in a central portion of a lower surface, and a weight body is provided in a central portion of a sensor portion to which a disc-shaped piezoelectric element having at least an electrode facing the excitation electrode is attached on an upper surface. 5. The angular velocity sensor according to claim 1, wherein the sensor portion is supported by a cylinder. 6. The angular velocity sensor according to claim 2, 4 or 5, wherein the cylindrical support member is suspended and fixed by two wires. 7. The angular velocity sensor according to claim 7, wherein a cylindrical support member is provided on one surface of the sensor portion, and a weight body is provided on the opposite surface.