JP3129022B2 - Acceleration sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

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

When acceleration is applied in a direction perpendicular 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 only detect acceleration in a direction perpendicular to the plane of the plate. Therefore, in order to detect accelerations in a plurality of directions, it is necessary to arrange a plurality of acceleration sensors in different directions of the plate.

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

[0006]

SUMMARY OF THE INVENTION The present invention includes a columnar vibrator and a plurality of piezoelectric elements formed on a side surface of the vibrator and arranged at a plurality of positions in a circumferential direction of the vibrator. The acceleration sensor is configured to vibrate the vibrator by applying a drive signal to the vibrator so that the vibrator extends and contracts on both sides of the center in the longitudinal direction. Also,
The present invention includes a columnar vibrator formed of a piezoelectric material, and a plurality of electrodes formed on a side surface of the vibrator and arranged at a plurality of positions in a circumferential direction of the vibrator, and applying a drive signal to the electrodes. By doing so, the acceleration sensor is configured to vibrate for a length such that the vibrating body extends and contracts in opposite directions on both sides of the center in the longitudinal direction.

[0007]

By applying a drive signal to a piezoelectric element or an electrode formed on the side surface of the vibrating body, the vibrating body can be vibrated in the longitudinal direction, and inertia is given 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 bends. A voltage is generated in the piezoelectric element according to the bending of the vibrator. Since the piezoelectric elements are formed at a plurality of positions in the circumferential direction of the vibrating body, a voltage corresponding to an acceleration component in a direction orthogonal to the piezoelectric element surface is generated in each piezoelectric element.

[0008]

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

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

[0010]

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

FIG. 2 shows one end of the vibrating body 12 in the longitudinal direction.
As shown in FIG. 5, driving piezoelectric elements 14a and 14b are formed on the opposing side surfaces of the vibrating body 12. Further, the vibrating body 12
Driving piezoelectric elements 14a, 14
The other driving piezoelectric elements 14c, 1
4d is formed. Further, the driving piezoelectric elements 14a, 1
4b is formed on the surface on which the detection piezoelectric elements 16a, 16
b is formed. These detection 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 of the vibrating body 12 where the detecting piezoelectric elements 16a and 16b are not formed, another detecting piezoelectric element 16c and 1
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, piezoelectric ceramic. Electrodes 20a and 22a are formed on both surfaces of the piezoelectric plate 18a. Then, one electrode 22 a is adhered to the side surface of the vibrating body 12. Similarly, the driving piezoelectric elements 14b, 14c, and 14d include piezoelectric plates 18b, 18c, and 18d.
b, 22b, electrodes 20c, 22c and electrodes 20d, 2
2d is formed. Then, the driving piezoelectric elements 1
4b, 14c, 14d, one of the electrodes 22b, 22c, 2
2 d 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. In the driving piezoelectric elements 14c and 14d on the other end side of the vibrating body 12, the piezoelectric plates 18c and 18d
Polarized from two sides outward.

The detecting piezoelectric elements 16a, 16b, 1
6c, 16d are piezoelectric plates 24a, 24b, 24c, 24
d. These piezoelectric plates 24a, 24b, 24c, 2
The electrodes 26a and 28a and the electrode 2
6b, 28b, electrodes 26c, 28c and electrode 26d,
28d are formed. Then, one electrode 28a of each of these detecting piezoelectric elements 16a, 16b, 16c, 16d is formed.
28b, 28c, 28d are adhered 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
d is polarized, for example, 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 the other end of the vibrating body 12 has a weight 3
0 is attached. Therefore, in this embodiment, the vibrating body 12 has a cantilever structure. This acceleration sensor 10
Is used, as shown in FIG.
The oscillation circuit 32 is connected to 4a to 14d. The oscillating 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 the members 4c and 14d are also formed to face each other, the vibrating body 12 vibrates in the length direction. Also, the driving piezoelectric elements 14a and 14b and the driving piezoelectric elements 14c and 14d
Are displaced in directions opposite to each other by the drive signal having 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 is contracted, the other side is extended, as indicated by the one-dot chain line arrow in FIG. 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 support portion. Therefore, stable vibration can be obtained.

When the vibrating body 12 vibrates, inertia is given to the vibrating body 12. In this state, when acceleration is applied, for example, in a direction perpendicular to the surfaces of the detecting piezoelectric elements 16a, 16b, the vibrating body 12 bends in a direction perpendicular to the surfaces of the detecting piezoelectric elements 16a, 16b, as shown in FIG. No. When the vibrating body 12 bends, the vibration of the vibrating body 12 is hindered, and the resonance characteristics change. By measuring the change in the resonance characteristics, the acceleration can be detected. In order to measure the acceleration in this manner, the detection piezoelectric element 1
What is necessary is just to measure the voltage generated in 6a, 16b. Also,
As for the acceleration in the direction perpendicular to the surfaces of the detecting piezoelectric elements 16c and 16d, the voltage generated in the detecting 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 a differential circuit 34, and the other detecting piezoelectric elements 16c and 16d are connected to a differential circuit 36. You. These detecting piezoelectric elements 16a-1
6d is polarized from the outside toward the vibrating body 12, so that when acceleration is not applied to the acceleration sensor 10, voltages of the same phase and the same magnitude are generated. Therefore, the outputs of the differential circuits 34 and 36 become 0. When acceleration is applied to the acceleration sensor 10 and the vibrating body 12 bends,
Opposite phase voltages 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 detecting piezoelectric elements 16a and 16b. Therefore, acceleration in a direction perpendicular to the surfaces of the driving piezoelectric elements 16a and 16b can be detected with high sensitivity. Similarly, the detecting piezoelectric element 16
By causing the differential circuit 36 to output the difference between the output voltages c and 16d, it is possible to detect the acceleration in a direction orthogonal to the surfaces of the piezoelectric elements 16c and 16d with high sensitivity.

Further, when an acceleration that is not orthogonal to the surfaces 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 detecting piezoelectric elements 16a to 16d is
This corresponds to an acceleration component in a direction orthogonal to the planes 6a to 16d. Therefore, accelerations in all directions perpendicular to the central axis of the vibrating body 12 can be detected from the output signals of the differential circuits 34 and 36.

Note that the detecting piezoelectric elements 16a to 16d are not always necessary, and the driving piezoelectric elements 14a to 14d may be used for detection. In this 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 opposing side surfaces of the vibrating body 12. And 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 this acceleration sensor 10, the driving piezoelectric elements 14a and 14b and the driving piezoelectric elements 14c and 14d are polarized in directions opposite to each other. Then, as shown in FIG. 10, the driving piezoelectric elements 14a to 14d
The oscillation circuit 32 is connected via a, 38b, 38c, 38d. Due to the signal from the oscillation circuit 32, the vibrating body 12 vibrates in its length direction. Then, by applying signals of the same phase to the driving piezoelectric elements 14a to 14d, vibrations in which the expansion and contraction are reversed on both sides in the longitudinal direction of the vibrating body 12 are generated.

The driving piezoelectric elements 14a and 14b are connected to the input terminals of the differential circuit 34, and are connected to the driving piezoelectric elements 14c and 14b.
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 bends,
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-described embodiment, the vibrating body 12
May be a double-supported beam structure instead of a cantilevered beam structure. In this case, for example, the vibrating body 12 is supported by a frame or the like. As described above, even if the vibrating body 12 has a doubly supported structure, both ends of the vibrating body 12 are not displaced, so that there is little vibration leakage. Therefore, an acceleration sensor having good characteristics can be obtained. Further, in an acceleration sensor having a doubly supported 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 weight of the weight,
A highly sensitive acceleration sensor can be obtained.

In each of the above embodiments, the driving piezoelectric element 14
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 vibration body 12, or may be polarized from the vibration body 12 side toward the outside. In such a case, the driving piezoelectric elements 14a, 1
4b and the driving piezoelectric elements 14c, 1
The drive signal applied to 4d has a phase opposite to that of the drive signal.
Even in this case, the vibrating body 12 can be vibrated such that the expansion and contraction are opposite on both sides in the length direction of the vibrating body 12.

The shape of the vibrating body 12 may be a polygonal prism, such as a hexagonal prism or an octagonal prism.
It may be formed in a columnar shape. Even in such a columnar shape, the acceleration can be detected by forming the driving piezoelectric elements on the opposing 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 in the above-described embodiments. Then, by applying a drive signal to these electrodes, the vibrating body 12 can be vibrated. Also, acceleration can be detected by measuring the output voltage from the electrodes. When the vibrating body is formed of piezoelectric ceramic, the shape of the electrode is not limited to a flat plate, and may be, for example, a comb-shaped electrode.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view of the acceleration sensor shown in FIG.

FIG. 3 is a cross-sectional view of the acceleration sensor shown in FIG. 1 cut along another opposite side surface.

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

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.

FIG. 9 is a cross-sectional view of the acceleration sensor shown in FIG.

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]

 DESCRIPTION OF SYMBOLS 10 Acceleration sensor 12 Vibrating body 14a Driving piezoelectric element 14b Driving piezoelectric element 14c Driving piezoelectric element 14d Driving piezoelectric element 16a Detection piezoelectric element 16b Detection piezoelectric element 16c Detection piezoelectric element 16d Detection piezoelectric element

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-49-88573 (JP, A) JP-A-4-282459 (JP, A) JP-A-59-10855 (JP, A) JP-A-61-1985 178667 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01P 15/08-15/10

Claims (2)

(57) [Claims] 1. A piezoelectric device, comprising: a columnar vibrator; and a plurality of piezoelectric elements formed on side surfaces of the vibrator and arranged at a plurality of positions in a circumferential direction of the vibrator, and applying a drive signal to the piezoelectric element. The acceleration sensor according to claim 1, wherein the vibrating body vibrates for a length such that extension and contraction of the vibrating body are opposite to each other on both sides of a central portion in the longitudinal direction. 2. A driving method comprising: a column-shaped 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 signal is applied to cause the vibrating body to vibrate in a length direction such that extension and contraction of the vibrating body are opposite to each other on both sides of a central portion in a length direction.