JPH06273438A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To obtain an acceleration sensor which can detect an acceleration in a plurality of directions. CONSTITUTION:An acceleration sensor 10 includes a quandrangular prism-shaped vibration body 12. Piezoelectric elements 14a, 14b for drive are installed on one end side in the length direction, and other piezoelectric elements 14c, 14d for drive are insatlled on the other end side. Piezoelectric elements 16a, 16b, 16c, 16d for detection are installed on four sides. The piezoelectric elements 14a, 14b for drive and the piezoelectric elements 16a to 16d for detection are polarized from the outside toward the side of the vibration body 12. The piezoelectric elements 14c, 14d for drive are polarized from the side of the vibration body 12 toward the outside. Driving signals of the same phase are applied to the piezoelectric elements 14a to 14d for drive, and the vibration body 12 is length-vibrated. At this time, the vibration body 12 is vibrated in such a way that its expansion and its contraction are reversed on both sides in the length direction. The difference in an output voltage between the opposite piezoelectric elements 16a, 16b for detection and the difference in an output voltage between the piezoelectric elements 16c, 16d for detection are measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor,
Particularly, for example, it relates to an acceleration sensor used for camera shake detection and a three-dimensional mouse.

[0002]

2. Description of the Related Art FIG. 11 is an illustrative view showing an example of a conventional acceleration sensor. The acceleration sensor 1 includes a plate body 2. One end of the plate body 2 is fixed, and the weight 3 is attached to the other end. Further, piezoelectric elements 4 are formed on both sides of the plate body 2.

When acceleration is applied in a direction orthogonal to the surface of the plate 2 of the acceleration sensor 1, the plate 2 is bent as shown in FIG. As a result, a voltage corresponding to the bending is generated in the piezoelectric element 4. By measuring this voltage, the acceleration can be detected.

[0004]

However, such an acceleration sensor can detect only the acceleration in the direction orthogonal to the plane of the plate body. Therefore, in order to detect accelerations in a plurality of directions, it is necessary to arrange a plurality of acceleration sensors so that the plate bodies have different directions.

Therefore, a main object of the present invention is to provide an acceleration sensor capable of detecting accelerations in a plurality of directions.

[0006]

The present invention includes a columnar vibrating body and a plurality of piezoelectric elements formed on a side surface of the vibrating body and arranged at a plurality of circumferential positions of the vibrating body. Is an acceleration sensor in which a vibration signal is applied to the vibrating body so that the vibrating body vibrates in such a manner that the extension and contraction are opposite on both sides of the central portion in the longitudinal direction. Also,
The present invention includes a columnar vibrating body formed of a piezoelectric material and a plurality of electrodes formed on a side surface of the vibrating body and arranged at a plurality of circumferential positions of the vibrating body, and applying a drive signal to the electrodes. By doing so, the acceleration sensor is configured to vibrate in such a manner that the vibrating body extends and contracts in opposite directions on both sides of the center portion in the longitudinal direction.

[0007]

By applying a drive signal to the piezoelectric element or electrode formed on the side surface of the vibrating body, the vibrating body can be vibrated in the longitudinal direction, and inertia is imparted to the vibrating body. In this state, when acceleration is applied in a direction orthogonal to the central axis of the vibrating body, the vibrating body is bent. A voltage is generated in the piezoelectric element according to the bending of the vibrating body. Since the piezoelectric element is formed at a plurality of positions in the circumferential direction of the vibrating body, a voltage corresponding to the acceleration component in the direction orthogonal to the piezoelectric element surface is generated in each piezoelectric element.

[0008]

According to the present invention, since a voltage is generated in each piezoelectric element corresponding to the acceleration component in the direction orthogonal to the piezoelectric element surface, the acceleration in all directions orthogonal to the central axis of the vibrating body is obtained. Can be detected.

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.

[0010]

1 is a plan view showing an embodiment of the present invention. The acceleration sensor 10 includes a vibrating body 12. Vibrating body 1
The material 2 is generally made of a material that causes mechanical vibration, such as elinvar, iron-nickel alloy, quartz, glass, crystal, and ceramic. The vibrating body 12 is formed in, for example, a regular quadrangular prism shape.

As shown in FIG.
As shown in, the driving piezoelectric elements 14a and 14b are formed on the opposite side surfaces of the vibrating body 12. In addition, the vibrating body 12
On the other end side in the length direction of the drive piezoelectric elements 14a, 14
On the side surface where b is formed, another driving piezoelectric element 14c, 1
4d is formed. Further, the driving piezoelectric elements 14a, 1
On the surface on which 4b is formed, the detection piezoelectric elements 16a, 16
b is formed. These detecting piezoelectric elements 16a, 16
b is formed on one end side of the vibrating body 12 adjacent to the driving piezoelectric elements 14a and 14b. Further, as shown in FIG. 3, on the side surface of the vibrating body 12 where the detecting piezoelectric elements 16a and 16b are not formed, another detecting piezoelectric elements 16c and 1c are provided.
6d is formed. These detecting piezoelectric elements 16c, 1
6d is formed on one end side in the length direction of the vibrating body 12.

The driving piezoelectric element 14a includes a piezoelectric plate 18a made of, for example, a piezoelectric ceramic. Electrodes 20a and 22a are formed on both surfaces of the piezoelectric plate 18a. Then, the one electrode 22a is bonded to the side surface of the vibrating body 12. Similarly, the driving piezoelectric elements 14b, 14c, 14d include piezoelectric plates 18b, 18c, 18d, and the electrodes 20 are provided on both surfaces of the piezoelectric plates 18b, 18c, 18d, respectively.
b, 22b, electrodes 20c, 22c and electrodes 20d, 2
2d is formed. Then, those driving piezoelectric elements 1
One electrode 22b, 22c, 2 of 4b, 14c, 14d
2d is bonded to the side surface of the vibrating body 12. In the driving piezoelectric elements 14a and 14b on one end side of the vibrating body 12, the piezoelectric plate 1
8a and 18b are polarized from the outside toward the vibrating body 12 side. Further, in the driving piezoelectric elements 14c and 14d on the other end side of the vibrating body 12, the piezoelectric plates 18c and 18d are the vibrating body 1
It is polarized from the 2 side toward the outside.

Further, the detecting piezoelectric elements 16a, 16b, 1
6c, 16d are piezoelectric plates 24a, 24b, 24c, 24
Including d. These piezoelectric plates 24a, 24b, 24c, 2
Electrodes 26a, 28a and electrode 2 are provided on both sides of 4d, respectively.
6b, 28b, electrodes 26c, 28c and electrodes 26d,
28d is formed. Then, one of the electrodes 28a of the detecting piezoelectric elements 16a, 16b, 16c, 16d,
28b, 28c, 28d are bonded to the side surface of the vibrating body 12. These detecting piezoelectric elements 16a, 16b, 16
c, 16d, the piezoelectric plates 24a, 24b, 24c, 24
For example, d is polarized from the outside toward the vibrating body 12 side.

In this acceleration sensor 10, for example, one end of a vibrating body 12 is supported, and a weight 3 is attached to the other end of the vibrating body 12.
0 is attached. Therefore, in this embodiment, the vibrating body 12 has a cantilever structure. This acceleration sensor 10
When using, as shown in FIG. 4, the driving piezoelectric element 1
The oscillator circuit 32 is connected to 4a to 14d. The oscillation circuit 32 applies signals of the same phase to the driving piezoelectric elements 14a to 14d. Driving piezoelectric elements 14a, 14
b are formed so as to face each other, and the driving piezoelectric element 1
Since 4c and 14d are also formed so as to face each other, the vibrating body 12 vibrates in the longitudinal direction. In addition, the driving piezoelectric elements 14a and 14b and the driving piezoelectric elements 14c and 14d
Since they are polarized in the opposite directions, they are displaced in opposite directions by the drive signals of the same phase. Therefore, as shown by the solid arrow in FIG. 1, when one side of the vibrating body 12 extends around the center of the vibrating body 12, the other side contracts. When one side of the vibrating body 12 contracts, the other side of the vibrating body 12 expands, as indicated by the dashed-dotted line arrow in FIG. 1. In this way, the vibrating body 12 vibrates in its length direction. Therefore, the displacement of both sides of the vibrating body 12 is absorbed, and both ends of the vibrating body 12 are not displaced, so that there is little vibration leakage to the supporting portion. Therefore, stable vibration can be obtained.

The vibration of the vibrating body 12 gives inertia to the vibrating body 12. In this state, for example, when acceleration is applied in a direction orthogonal to the planes of the detection piezoelectric elements 16a and 16b, the vibrating body 12 bends in a direction orthogonal to the planes of the detection piezoelectric elements 16a and 16b, as shown in FIG. Mu. The bending of the vibrating body 12 hinders the vibration of the vibrating body 12 and changes the resonance characteristic. Acceleration can be detected by measuring the change in the resonance characteristic. In order to measure the acceleration in this way, the piezoelectric element for detection 1
The voltage generated in 6a and 16b may be measured. Also,
For the acceleration in the direction orthogonal to the surfaces of the detection piezoelectric elements 16c and 16d, the voltage generated in the detection piezoelectric elements 16c and 16d may be measured.

In order to detect the acceleration, as shown in FIG. 6, the detecting piezoelectric elements 16a and 16b are connected to the differential circuit 34, and the other detecting piezoelectric elements 16c and 16d are connected to the differential circuit 36. It These detecting piezoelectric elements 16a to 1
Since 6d is polarized from the outside toward the vibrating body 12, the voltage of the same phase and the same magnitude is generated when acceleration is not applied to the acceleration sensor 10. Therefore, the outputs of the differential circuits 34 and 36 become zero. Further, when acceleration is applied to the acceleration sensor 10 and the vibrating body 12 bends,
Voltages of opposite phases are generated in the opposing piezoelectric elements. Therefore, a large output signal can be obtained from the differential circuit 34 by measuring the difference between the output voltages of the opposing detection piezoelectric elements 16a and 16b. Therefore, the acceleration in the direction orthogonal to the surfaces of the driving piezoelectric elements 16a and 16b can be detected with high sensitivity. Similarly, the detection piezoelectric element 16
By causing the differential circuit 36 to output the difference between the output voltages of c and 16d, the acceleration in the direction orthogonal to the surfaces of these piezoelectric elements 16c and 16d can be detected with high sensitivity.

Further, when an acceleration that is not orthogonal to the planes of the driving piezoelectric elements 16a to 16d is applied to the acceleration sensor 10, the vibrating body 12 bends in the direction in which the acceleration is applied. Then, a voltage corresponding to the bending of the vibrating body 12 is generated in the detecting piezoelectric elements 16a to 16d. That is, the voltage generated in the detection piezoelectric elements 16a to 16d is the same as the detection piezoelectric element 1
This corresponds to the acceleration component in the direction orthogonal to the planes 6a to 16d. Therefore, the accelerations in all directions orthogonal to the central axis of the vibrating body 12 can be detected from the output signals of the differential circuits 34 and 36.

The detecting piezoelectric elements 16a to 16d are not always necessary, and the driving piezoelectric elements 14a to 14d may also be used for detecting. In that case, as shown in FIGS. 7, 8 and 9, the driving piezoelectric elements 14a, 14b.
The driving piezoelectric elements 14c and 14d are formed on different facing side surfaces of the vibrating body 12. Then, the driving piezoelectric element 1
4a and 14b are formed on one end side of the vibrating body 12, and the driving piezoelectric elements 14c and 14d are formed on the other end side of the vibrating body 12. Also in the acceleration sensor 10, the driving piezoelectric elements 14a and 14b and the driving piezoelectric elements 14c and 14d are polarized in opposite directions. Then, as shown in FIG. 10, a resistor 38 is connected to the driving piezoelectric elements 14a to 14d.
The oscillation circuit 32 is connected via a, 38b, 38c, and 38d. The vibrating body 12 vibrates in the lengthwise direction by the signal from the oscillation circuit 32. Then, by applying signals of the same phase to the driving piezoelectric elements 14a to 14d, vibration occurs in which the expansion and the contraction are opposite on both sides in the length direction of the vibrating body 12.

The driving piezoelectric elements 14a and 14b are connected to the input ends of the differential circuit 34, and the driving piezoelectric elements 14c and 14b are connected.
d is connected to the input terminal of the differential circuit 36. When acceleration is applied to the acceleration sensor 10 and the vibrating body 12 is bent,
A voltage is generated in each of the piezoelectric elements 14a to 14d. By measuring the difference between these voltages by the differential circuits 34 and 36, the acceleration applied to the acceleration sensor 10 can be detected. At this time, the drive signals applied to the piezoelectric elements 14a to 14d are canceled by the differential circuits 34 and 36. Therefore, only the signal corresponding to the acceleration is output from the output terminals of the differential circuits 34 and 36.

In the above embodiment, the vibrating body 12
May have a cantilever structure instead of a cantilever structure. In this case, for example, the vibrating body 12 is supported by the frame or the like. In this way, even if the vibrating body 12 has a double-supported beam structure, both ends of the vibrating body 12 do not displace, so that there is little vibration leakage. Therefore, an acceleration sensor having good characteristics can be obtained. Furthermore, in an acceleration sensor having a doubly supported beam structure, weights may be formed at both ends of the vibrating body 12.
With this configuration, when the vibrating body 12 is bent, the bending of the vibrating body 12 can be increased by the mass of the weight.
A highly sensitive acceleration sensor can be obtained.

In each of the above embodiments, the driving piezoelectric element 14 is used.
Although a and 14b and the driving piezoelectric elements 14c and 14d are polarized in opposite directions, all the driving piezoelectric elements 14a to 14d may be polarized in the same direction. That is, the driving piezoelectric element 1
4a to 14d may be polarized from the outside toward the vibrating body 12 or may be polarized from the vibrating body 12 side toward the outside. In such a case, the driving piezoelectric elements 14a, 1
Drive signal applied to 4b and drive piezoelectric elements 14c, 1
The drive signals applied to 4d have opposite phases to each other.
Even in this case, the vibrating body 12 can be vibrated so that the expansion and the contraction are opposite on both sides in the longitudinal direction of the vibrating body 12.

The vibrating body 12 may be formed in another polygonal column shape such as a hexagonal column shape or an octagonal column shape.
It may be formed in a cylindrical shape. Even with such a columnar shape, the acceleration can be detected by forming the driving piezoelectric element on the opposite side surfaces and forming the piezoelectric elements used for detection at a plurality of positions in the circumferential direction of the vibrating body. Further, the vibrating body may be formed of piezoelectric ceramic. In this case, electrodes are formed at the same positions as those in the above-mentioned respective embodiments. The vibrator 12 can be vibrated by applying a drive signal to these electrodes. Further, the acceleration can be detected by measuring the output voltage from the electrode. When the vibrating body is formed of piezoelectric ceramic, the shape of the electrode is not limited to the flat plate shape, and may be, for example, a comb-shaped electrode.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along one of opposite side surfaces of the acceleration sensor shown in FIG.

FIG. 3 is a cross-sectional view of the acceleration sensor shown in FIG. 1 taken along the other opposing side surface.

FIG. 4 is a circuit diagram showing a drive circuit for vibrating the acceleration sensor shown in FIG.

5 is an illustrative view showing a state where acceleration is applied to the acceleration sensor shown in FIG. 1. FIG.

6 is a circuit diagram showing a detection circuit for measuring an output voltage of the acceleration sensor shown in FIG.

FIG. 7 is a plan view showing another embodiment of the present invention.

FIG. 8 is a cross-sectional view of the acceleration sensor shown in FIG.

9 is a cross-sectional view of the acceleration sensor shown in FIG. 7, taken along the other opposing side surface.

10 is a circuit diagram showing a drive circuit and a detection circuit of the acceleration sensor shown in FIG.

FIG. 11 is an illustrative view showing one example of a conventional acceleration sensor.

FIG. 12 is an illustrative view showing a state when acceleration is applied to the conventional acceleration sensor shown in FIG. 11.

[Explanation of symbols]

 Reference Signs List 10 acceleration sensor 12 vibrating body 14a driving piezoelectric element 14b driving piezoelectric element 14c driving piezoelectric element 14d driving piezoelectric element 16a detecting piezoelectric element 16b detecting piezoelectric element 16c detecting piezoelectric element 16d detecting piezoelectric element

Claims (2)

[Claims] 1. A columnar vibrating body, and a plurality of piezoelectric elements formed on a side surface of the vibrating body and arranged at a plurality of circumferential positions of the vibrating body, wherein a drive signal is applied to the piezoelectric element. Thus, the acceleration sensor is configured to vibrate in such a manner that the vibrating body extends and contracts in opposite directions on both sides of the central portion in the longitudinal direction. 2. A columnar vibrating body formed of a piezoelectric material, and a plurality of electrodes formed on a side surface of the vibrating body and arranged at a plurality of positions in a circumferential direction of the vibrating body. An acceleration sensor, wherein a vibration is applied to the vibrating body on both sides of a central portion in the lengthwise direction so that the vibrating body extends and contracts in the opposite direction.