JP2508384B2 - Angular velocity sensor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity sensor, and more particularly to an angular velocity sensor used, for example, for detecting a camera shake of a video camera or controlling the attitude of a vehicle.

(Prior Art) FIG. 9A is a perspective view showing an example of a conventional angular velocity sensor which is the background of the present invention, and FIG. 9B is a sectional view thereof.
The angular velocity sensor 1 includes a vibrating body 2. The vibrating body 2 is made of a material such as elinvar which causes mechanical vibration, and is formed in, for example, a triangular prism shape.

Piezoelectric elements 3a and 3b are provided on the three side surfaces of the vibrating body 2, respectively.
And 3c are formed. The piezoelectric elements 3a, 3b, 3c are, for example, piezoelectric ceramics with electrodes formed on both sides.
One of the electrodes of the piezoelectric elements 3a, 3b, 3c is bonded to the vibrating body 2 with, for example, an adhesive. The vibrating body 2 is supported by the supporting member near the node point.

In this angular velocity sensor 1, for example, an oscillation circuit output source is connected between the piezoelectric elements 3a and 3b and the piezoelectric element 3c. The oscillator 2 flexurally vibrates in the direction orthogonal to the main surface of the piezoelectric element 3c by a signal from the oscillation circuit output source. And
By measuring the difference between the output voltages of the piezoelectric elements 3a and 3b,
The rotational angular velocity applied to the angular velocity sensor 1 is measured.

(Problems to be Solved by the Invention) However, in such a conventional angular velocity sensor,
Since it is necessary to bond the piezoelectric element to the central portion of the side surface of the vibrating body, its processing is difficult. Further, since the vibrating body and the piezoelectric element have different coefficients of thermal expansion, variations in the bonded portion occur due to changes in the ambient temperature, and variations in the characteristics tend to occur. In addition, manufacturing costs are high because processing is difficult,
Furthermore, it has been difficult to miniaturize the angular velocity sensor.

Therefore, a main object of the present invention is to provide an angular velocity sensor which can be easily manufactured, has less variation in characteristics, and can be miniaturized.

(Means for Solving the Problem) The present invention relates to a vibrating body formed of a polygonal prism-shaped piezoelectric ceramic having a through hole penetrating in the axial direction thereof, and an internal electrode formed on an inner peripheral surface of the vibrating body, The vibrating body includes an external electrode formed on the outer peripheral surface of the vibrating body, and the vibrating body is an angular velocity sensor polarized in the direction from the inner peripheral surface to the outer peripheral surface.

(Function) Applying a signal between a plurality of external electrodes or between an internal electrode and an external electrode by applying polarization from the inner peripheral surface to the outer peripheral surface of the piezoelectric ceramic in the shape of a polygonal column having through holes formed therein. Causes the vibrating body itself to flex and vibrate.

(Effect of the invention) According to the present invention, vapor deposition, sputtering,
The electrodes can be formed by a silver paste sintering method, plating, or the like. Further, since the vibrating body itself undergoes bending vibration, it is not necessary to bond the piezoelectric element to the vibrating body. Therefore, the processing of the angular velocity sensor is simple, and the angular velocity sensor can be manufactured at a lower cost than the conventional one. Furthermore, since it is not necessary to bond the piezoelectric element to the vibrating body, there is no variation in the bonded portion due to changes in the ambient temperature, and variation in characteristics is reduced. Further, by forming the through-hole, the resonance frequency becomes smaller and the sensitivity becomes better than that of the vibrating body in which the through-hole is not formed. If the sensitivity is the same, the vibrating body can be downsized, and thus the angular velocity sensor can be downsized.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

(Embodiment) FIG. 1A is a perspective view showing an embodiment of the present invention.
FIG. 1B is a cross-sectional view taken along line IB-IB of FIG. 1A. The angular velocity sensor 10 includes a vibrating body 12. The vibrating body 12 is made of piezoelectric ceramic and is formed, for example, in a regular triangular prism shape. A regular triangular prismatic through hole 14 is formed in the vibrating body 12 in the axial direction. Further, the vibrating body 12 is radially polarized from the inner peripheral surface toward the outer peripheral surface. The vibrating body 12 is supported near its node point.

An internal electrode 16 is formed on the entire inner peripheral surface of the vibrating body 12. Further, external electrodes 18a, 18b and 18c are formed in the center of the three side surfaces of the vibrating body 12, respectively. The internal electrodes 16 and the external electrodes 18a to 18c are made of silver, for example, and are formed by a silver paste sintering method, plating, vapor deposition, sputtering, or the like.

To manufacture the angular velocity sensor 10, the vibrating body 12 having the through holes 14 formed therein is prepared. As shown in FIG. 2, the internal electrode 16 and the outer peripheral surface electrode 20 are formed on the entire inner peripheral surface and the entire outer peripheral surface of the vibrating body 12 by a silver paste sintering method, plating, vapor deposition, sputtering or the like. To be done.
Then, by applying an electric field between the inner electrode 16 and the outer peripheral surface electrode 20, as shown by the arrow, the vibrating body 12 is radially polarized from the inner peripheral surface toward the outer peripheral surface.

Next, the external electrodes 18a, 18b, 18c are formed by removing unnecessary portions of the outer peripheral surface electrode 20.

To use the angular velocity sensor 10, for example, an angular velocity detection circuit as shown in FIG. 3 is used. That is, the resistors 22 and 24 are connected to the two external electrodes 18a and 18b.
An oscillation circuit output source 26 is connected between these resistors 22 and 24 and the other external electrode 18c. This oscillator output source 26
The vibrating body 12 flexurally vibrates in the direction orthogonal to the main surface of the external electrode 18c by the signal from the.

Further, another resistance 28, 30 is provided on each of the two external electrodes 18a, 18b.
Is connected. These resistors 28 and 30 are connected to the differential amplifier circuit 32.
Connected to the input side of. Further, the output side of the differential amplifier circuit 32 is connected to the synchronous detection circuit 34, and the synchronous detection circuit 34 is connected to the ripple filter 36.

When the vibrating body 12 is flexurally vibrated by a signal from the oscillation circuit output source 26, when the vibrating body 12 rotates about the axis of the vibrating body 12, Coriolis force is generated in a direction orthogonal to the vibrating direction according to the rotational angular velocity. work. As a result, the vibration direction of the vibrating body 12 is deviated from the vibration direction when there is no rotation. for that reason,
A difference in output voltage occurs between the two external electrodes 18a and 18b, and an output is obtained from the differential amplifier circuit 32.

The output obtained from the differential amplifier circuit 32 is synchronously detected by the synchronous detection circuit 34 and further passed through the ripple filter 36 to obtain a DC output. Therefore, the rotational angular velocity applied to the angular velocity sensor 10 can be measured by measuring this DC output.

In this angular velocity sensor 10, since the vibrating body 12 is formed of piezoelectric ceramic, it is not necessary to bond a piezoelectric element to the side surface of the vibrating body as in the conventional one. Therefore, the internal electrode 16 and the external electrodes 18a to 1a are attached to the piezoelectric ceramic vibrating body 12.
8c may be formed. These electrodes can be easily formed by a silver paste sintering method, plating, vapor deposition, sputtering or the like.

Moreover, the external electrodes 18a to 18c can be formed by removing unnecessary portions of the outer peripheral surface electrode 20. The outer peripheral surface electrode 20 can be used to polarize the vibrating body 12. That is, in this angular velocity sensor 10, the outer electrodes 18a to 18c can be formed by using the outer peripheral surface electrode 20 for polarizing the vibrating body 12. Therefore,
The angular velocity sensor 10 can be manufactured more easily than the conventional angular velocity sensor, and can be manufactured at low cost.

Further, since no adhesive is used in the angular velocity sensor 10, the characteristic change due to the difference in thermal expansion coefficient between the piezoelectric element and the vibrating body due to the change in ambient temperature does not occur unlike the conventional angular velocity sensor. Further, a through hole is formed in the vibrating body 12 having a triangular prism shape.
By forming 14, the resonance frequency can be made smaller and the sensitivity thereof can be made higher than that of a vibrating body of the same shape in which no through hole is formed. Further, if the sensitivity is the same, the vibrating body 12 can be made smaller than that having no through hole.

In the above-mentioned embodiment, the external electrodes 18a, 18b and the external electrode 1
Although the oscillator circuit output source 26 is connected between the internal electrode 16 and the external electrode 16c, the oscillator circuit output source 26 may be connected between the internal electrode 16 and the external electrode 16c as shown in FIG. Further, as shown in FIG. 5, an oscillation circuit output source 26 may be connected between the internal electrode 16 and the two external electrodes 18a, 18b. In order to obtain the circuit configurations as in these embodiments, the internal electrodes 16 can be formed by extending from the end face of the vibrating body 12 to the side face as shown in FIG.

The shape of the through hole 14 is not limited to the triangular prism shape, but may be another shape such as a cylindrical shape as shown in FIG. 7. Further, the shape of the vibrating body 12 is not limited to the triangular prism shape, but may be another polygonal shape such as a hexagonal prism shape as shown in FIG.

[Brief description of drawings]

FIG. 1A is a perspective view showing an embodiment of the present invention, and FIG.
The figure is a sectional view taken along line IB-IB in FIG. 1A. FIG. 2 is a perspective view showing a process of manufacturing the angular velocity sensor shown in FIGS. 1A and 1B. FIG. 3 is a circuit diagram showing an example of an angular velocity detection circuit using the angular velocity sensor shown in FIGS. 1A and 1B. FIG. 4 is a circuit diagram showing another example of the angular velocity detection circuit shown in FIG. FIG. 5 is a circuit diagram showing still another example of the angular velocity detection circuit shown in FIG. FIG. 6 is a perspective view showing another example of the angular velocity sensor shown in FIGS. 1A and 1B. FIG. 7 is a perspective view showing still another example of the angular velocity sensor shown in FIGS. 1A and 1B. FIG. 8 is a perspective view showing another example of the angular velocity sensor shown in FIGS. 1A and 1B. FIG. 9A is a perspective view showing an example of a conventional angular velocity sensor which is the background of the present invention, and FIG. 9B is a sectional view thereof. In the figure, 10 is an angular velocity sensor, 12 is a vibrating body, 14 is a through hole, 16 is an internal electrode, and 18a, 18b and 18c are external electrodes.

Claims (1)

(57) [Claims] 1. A vibrating body formed of a polygonal columnar piezoelectric ceramic having a through hole penetrating in the axial direction thereof, an internal electrode formed on an inner peripheral surface of the vibrating body, and an outer peripheral surface of the vibrating body. An angular velocity sensor, comprising: an external electrode, wherein the vibrating body is polarized in a direction from an inner peripheral surface to an outer peripheral surface thereof.