JPH08327653A - Acceleration sensor - Google Patents

Abstract

PURPOSE: To obtain an acceleration sensor which can detect the acceleration in two directions rotating about two axes. CONSTITUTION: The acceleration sensor 10 comprises an oscillator 12 provided, in the center thereof, with a square planar weight 14. The weight 14 has four sides coupled, at the central part thereof, with the central part of four oscillation plates 20a-20d of a frame body 18 through four elongated coupling parts 16a-16d. Supporting parts 22a-22d, at four corners of the frame body 18, are inserted into a board 24 and soldered to electrodes provided on the major surface of the board 24. The four oscillation plates 20a-20d of the frame body 18 are bonded with sixteen piezoelectric elements 26a1-26a4, 26b1-26b4, 26c1-26c4, and 26d1-26d4.

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 that can be applied to a vibration isolation system such as a camera shake prevention device of a video camera that detects acceleration generated by external vibration and appropriately suppresses vibration.

[0002]

2. Description of the Related Art Acceleration sensors of various types have been put into practical use. Among them, a vibration type acceleration sensor having a vibrator in which a piezoelectric element made of ceramic is bonded to a diaphragm made of metal is It is widely used because it has characteristics that it can measure acceleration from low frequencies close to 0 Hz and has a simple structure.

In the conventional vibration type acceleration sensor, the vibrator has a cantilever structure and a weight is attached to the tip of the vibrator, or both ends of the vibrator are fixed and a weight is attached to the center of the vibrator. There is something. In these acceleration sensors, when acceleration is applied thereto, the vibrator including the piezoelectric element bends, and a signal corresponding to the acceleration is obtained from the piezoelectric element of the vibrator. Therefore, the acceleration is detected by measuring the signal obtained from the piezoelectric element.

[0004]

However, in the conventional vibration type acceleration sensor, since the vibrator is curved only in the direction orthogonal to the main surface of the diaphragm due to its structure, it is possible to detect the acceleration in only one direction. Can not.

On the other hand, in a camera-shake preventing device for a video camera, for example, two-direction accelerations that rotate about two axes, that is, an acceleration that rotates about a horizontal axis and an acceleration that rotates about a vertical axis orthogonal to the horizontal axis, are used. Need to detect.

Therefore, in the prior art, two acceleration sensors are used in a camera shake prevention device for a video camera.
It is necessary to arrange and use in the direction, and there are problems such as an increase in arrangement space and an increase in the number of parts.

Therefore, the main object of the present invention is to
An object of the present invention is to provide an acceleration sensor capable of detecting accelerations in two directions rotating about an axis.

[0008]

According to the present invention, there are provided a weight, two first coupling portions provided on a first shaft, and two first coupling portions provided on a second shaft orthogonal to the first shaft. A frame body that is coupled to the weight via the second coupling portion and is arranged around the weight, a first piezoelectric element provided near the second coupling portion in the frame body, and a first coupling in the frame body. And a second piezoelectric element provided in the vicinity of the section.

In the acceleration sensor according to the present invention, the first detecting means for detecting a signal corresponding to the acceleration rotating about the first axis is connected to the first piezoelectric element, and the second detecting means is connected to the second piezoelectric element. A second detecting means for detecting a signal corresponding to the acceleration rotating about the axis may be connected to the second piezoelectric element.

[0010]

When an acceleration that rotates about the first axis is applied to the acceleration sensor according to the present invention, the weight rotates about the two first coupling portions as the central axes. Therefore, the vicinity of the second coupling portion in the frame body is deformed together with the first piezoelectric element. Therefore, a signal corresponding to the acceleration that rotates about the first axis is generated in the first piezoelectric element. The signal corresponding to the acceleration that rotates about the first axis is detected by, for example, the above-described first detection unit.

Further, when an acceleration that rotates about the second axis is applied to the acceleration sensor according to the present invention, the weight rotates about the two second coupling portions as the central axes. Therefore, the vicinity of the first coupling portion in the frame body is deformed together with the second piezoelectric element. Therefore, a signal corresponding to the acceleration that rotates about the second axis is generated in the second piezoelectric element. The signal corresponding to the acceleration that rotates about the second axis is detected by, for example, the above-mentioned second detection means.

[0012]

According to the present invention, the first shaft and the second shaft
An acceleration sensor that can detect accelerations in two directions rotating about the axis of is obtained. Therefore, in the acceleration sensor according to the present invention, it is possible to configure, for example, an image stabilization device for a video camera without using two acceleration sensors.

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.

[0014]

1 is a perspective view showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an oscillator circuit, a first detecting circuit and a second detecting circuit used in the embodiment shown in FIG. Is. The acceleration sensor 10 includes a vibrator 12, and the vibrator 1
2 has a weight 14 in its center. The weight 14 is formed in a square plate shape having a length of 5 mm, a width of 5 mm, and a thickness of 0.2 mm, for example.

The central portions of the four sides of the weight 14 are coupled to the central portions of the four diaphragms 20a to 20d of, for example, the rectangular frame 18 via the four coupling portions 16a to 16d. In this case, the two coupling parts 16b and 16d
Are arranged on the first axis (horizontal axis X) that passes through the center of the weight 14 as the first coupling portion. Also, the two joints 1
6a and 16c are arranged as a second coupling portion on a second axis (vertical axis Y) that passes through the center of the weight 14 and is orthogonal to the first axis (horizontal axis). Thereby, the weight 14 is
It is arranged inside the frame body 18. In addition, the coupling portions 16a to 1
6d has a length of 1 mm and a width of 0.2 m, respectively.
m, and the thickness is 0.2 mm. Frame 1
For example, 8 has a square shape with one side of 7 mm on one side, a square shape with one side of 9 mm on the outer side, and has a thickness of 0.2 mm.

At the four corners of the frame 18, four support portions 22a are provided.
22d are formed to extend in a direction orthogonal to the main surfaces of the diaphragms 20a to 20d. In addition, the support portions 22a to 2
2d is, for example, 4 mm long and 0.5 m wide
m and the thickness is 0.2 mm. These support portions 22
The a to 22d are inserted into a board 24 such as a glass-epoxy printed board and soldered to electrodes on the main surface of the board 24. Thereby, the frame body 18 and the like are attached to the substrate 24.

The weight 14, the connecting portions 16a to 16d,
Frame 18 (vibration plates 20a to 20d) and supporting portion 22a
22d are integrally formed by, for example, etching and bending by photolithography a plate material having a thickness of 0.2 mm and made of a Fe—Ni alloy (42Ni). For this etching, for example, a polyvinyl alcohol-based resist or an etching solution containing ferric chloride is used.

On one vibration plate 20a of the frame 18, two piezoelectric elements 26a1 and 26a2 are adhered to one main surface at an interval in the longitudinal direction with an adhesive such as an epoxy resin, and the other main surface. Two piezoelectric elements 26a3
And 26a4 are adhered at intervals in the longitudinal direction with an adhesive such as an epoxy resin. Similarly, the diaphragm 2
The four piezoelectric elements 26b1 to 26b4 are bonded to both main surfaces of the diaphragm 0b, and the four piezoelectric elements 2 are attached to both main surfaces of the diaphragm 20c.
6c1 to 26c4 are bonded, and four piezoelectric elements 26d1 to 26d4 are bonded to both main surfaces of the diaphragm 20d. Each piezoelectric element includes, for example, a piezoelectric layer made of a ceramic containing lead zirconate titanate as a main component, and electrodes are formed by sintering Ag on both sides of the piezoelectric layer, and each electrode has a length of 2 mm. The width is 1 mm and the thickness is 0.2 mm. Further, the piezoelectric elements 26a1, 26a2, 26b1, 26b adhered to one main surface of the vibration plates 20a-20d.
The piezoelectric layers 2, 26c1, 26c2, 26d1, 26d2 are polarized from the outer side toward the inner side (diaphragm side). Further, the piezoelectric elements 26a3, 26a4, 26b3, 26b adhered to the other main surfaces of the vibration plates 20a to 20d.
The piezoelectric layers 4, 26c3, 26c4, 26d3, 26d4 are polarized from the inner side (diaphragm side) to the outer side (substrate side).

16 piezoelectric elements 26a1 to 26a4, 2
6b1-26b4, 26c1-26c4, 26d1-2
There are 16 resistors 28a1 to 28a on the outer electrode of 6d4.
a4, 28b1 to 28b4, 28c1 to 28c4, 28
One end of each of d1 to 28d4 is connected. An oscillating circuit 30 as a driving unit is connected between the other ends of the 16 resistors and the frame 18 (electrodes inside the 16 piezoelectric elements). The oscillation circuit 30 is for generating a drive signal for vibrating the frame body 18, and is composed of, for example, an amplifier circuit 32 and a phase correction circuit 34 which are connected in series. The amplifier circuit 32 is for amplifying the signals obtained from the electrodes inside the 16 piezoelectric elements. The phase correction circuit 34 is for correcting the phase of the drive signal obtained from the amplifier circuit 32 and applying the drive signal with the corrected phase to the electrodes outside the 16 piezoelectric elements.

The electrodes outside the piezoelectric elements 26a1 and 26c2 used as the first piezoelectric elements have the first
The first detection circuit 40 as a detection means of is connected.
The first detection circuit 40 is for detecting a signal corresponding to the acceleration that rotates about the first axis (horizontal axis X) from the first piezoelectric element, and is, for example, the first differential circuit. 42 and a first synchronous detection circuit 44.
The piezoelectric element 26 is connected to the two input terminals of the first differential circuit 42.
The electrodes outside a1 and 26c2 are connected to each other. The output terminal of the first differential circuit 42 is connected to the input terminal of the first synchronous detection circuit 44. First synchronous detection circuit 44
The output end of the amplifier circuit 32 is connected to the other input end of the. The first synchronous detection circuit 44 is for detecting the signal obtained from the first differential circuit 42 in synchronization with the drive signal output from the amplification circuit 32 of the oscillation circuit 30.

Further, a second detection circuit 50 as second detection means is connected to the electrodes outside the piezoelectric elements 26b1 and 26d2 used as the second piezoelectric element. The second detection circuit 50 is for detecting a signal corresponding to the acceleration that rotates about the second axis (vertical axis Y) from the second piezoelectric element, and is, for example, the second differential circuit. 52 and a second synchronous detection circuit 54. Electrodes on the outside of the piezoelectric elements 26b1 and 26d2 are connected to the two input ends of the second differential circuit 52, respectively. The output terminal of the second differential circuit 52 is connected to the input terminal of the second synchronous detection circuit 54. Second synchronous detection circuit 5
The output terminal of the amplifier circuit 32 is connected to the other input terminal of 4. The second synchronous detection circuit 54 is for detecting the signal obtained from the second differential circuit 52 in synchronization with the drive signal output from the amplification circuit 32 of the oscillation circuit 30.

In this embodiment, the output signal of the oscillation circuit 30 is 16 resistors 28a1 to 28a4 and 28b1 to 28.
16 piezoelectric elements 26a1 to 26a4, 26b1 through b4, 28c1 to 28c4, 28d1 to 28d4
26b4, 26c1 to 26c4, 26d1 to 26d4. Then, the signals obtained from the electrodes inside the 16 piezoelectric elements are fed back to the oscillation circuit 30 via the frame 18. As a result, the vibrator 12 vibrates by self-exciting drive. In this case, the eight piezoelectric elements 26a on the one main surface side of the vibration plates 20a to 20d
1,26a2,26b1,26b2,26c1,26c
When 2, 26d1 and 26d2 extend, the eight piezoelectric elements 26a on the other main surface side of the vibration plates 20a to 20d.
3,26a4,26b3,26b4,26c3,26c
4, 26d3, 26d4 contract, and as shown in FIG. 3, the central portions of the diaphragms 20a to 20d are deformed outward and the central portion of the weight 14 is deformed inward. On the contrary, the eight piezoelectric elements 26a on the one main surface side of the vibration plates 20a to 20d
1,26a2,26b1,26b2,26c1,26c
When 2, 26d1 and 26d2 are contracted, the eight piezoelectric elements 26a on the other main surface side of the vibration plates 20a to 20d.
3,26a4,26b3,26b4,26c3,26c
4, 26d3, 26d4 extend and the vibration plates 20a to 20d
The respective central portions of the weight 14 are deformed inward, and the central portion of the weight 14 is deformed outward. Due to such vibration, inertia is applied to the frame body 18.

Further, in this embodiment, when the acceleration that rotates about the first axis (horizontal axis X) is applied, the weight 14 rotates about the two coupling portions 16b and 16d as the central axes, and, for example, as shown in FIG. As shown in, the central portion of the diaphragm 20a and the central portion of the diaphragm 20c are deformed inward and outward, respectively. Therefore, the piezoelectric elements 26a1 and 26c2 are deformed in the opposite directions, and the piezoelectric elements 26a1 and 26c2 generate signals of opposite phases according to the magnitude of the acceleration.

In this embodiment, the first differential circuit 40 detects the difference between the signals generated in the piezoelectric elements 26a1 and 26c2. The output signal of the first differential circuit 40 is detected by the first synchronous detection circuit 42 in synchronization with the drive signal. Therefore, from the first synchronous detection circuit 42, a signal corresponding to the acceleration rotating about the first axis (horizontal axis X) is obtained.

Since the drive signals given to the piezoelectric elements 26a1 and 26c2 are the same, the drive signal components are canceled by the first differential circuit 40. Therefore, the drive signal component is not output from the first differential circuit 40 and the first synchronous detection circuit 42.

Further, in this embodiment, when the acceleration that rotates about the second axis (vertical axis Y) is applied, the weight 14 rotates about the two coupling portions 16a and 16c, and for example, as shown in FIG. As shown in, the central portion of the diaphragm 20b and the central portion of the diaphragm 20d are deformed outward and inward, respectively. Therefore, the piezoelectric elements 26b1 and 26d2 are deformed in the opposite directions, and the piezoelectric elements 26b1 and 26d2 generate signals having opposite phases according to the magnitude of the acceleration.

In this embodiment, the second differential circuit 50 detects the difference between the signals generated in the piezoelectric elements 26b1 and 26d2. The output signal of the second differential circuit 50 is detected by the second synchronous detection circuit 52 in synchronization with the drive signal. Therefore, the second synchronous detection circuit 52 obtains a signal corresponding to the acceleration rotating about the second axis (vertical axis Y).

Since the drive signals applied to the piezoelectric elements 26b1 and 26d2 are the same, the drive signal components are canceled by the second differential circuit 50. Therefore, the drive signal component is not output from the second differential circuit 50 and the second synchronous detection circuit 52.

Further, in this embodiment, when acceleration is applied in the thickness direction (direction of the axis Z), the weight 14 projects outward as shown in FIG.
Each central portion of d is deformed outward in phase. Therefore, the piezoelectric elements 26a1, 26b2, 26c1, 26d2 are transformed into the same phase, and the piezoelectric elements 26a1, 26b2, 26c1, 2
An in-phase signal is generated at 6d2. Therefore, the signals generated in the piezoelectric elements 26a1, 26b2, 26c1, 26d2 are the same as those in the first differential circuit 40 and the second differential circuit 5.
They are canceled by 0 and are not output from the first differential circuit 40 and the second differential circuit 50.

Therefore, in this embodiment, the rotation about the first axis (horizontal axis X) and the acceleration about the second axis (vertical axis Y) rotate about two axes. It is possible to detect acceleration in two directions.

Further, in this embodiment, since the weight 14, the connecting portions 16a to 16d and the frame 18 are formed of flat plates, the overall thickness is thin.

Further, in this embodiment, the weight 14, the connecting portions 16a to 16d, and the frame 18 can be formed with high precision by etching, so that mass productivity is good.

Further, in this embodiment, since the node points of the vibrator 12 are located at the four corners of the frame 18, the vibrator 12 can be easily supported with almost no vibration of the vibrator 12.

In the above-mentioned embodiment, the Fe-Ni alloy is used as the material for the weight 14 and the frame 18, but other materials such as constant elasticity steel and Invar may be used.

From the role of the weight 14, the weight 14 is, for example,
It may be formed thicker than other members such as 8. Further, the weight 14 is not limited to a square plate shape, but a rectangular plate shape, a disk shape,
It may be formed in another shape such as a block shape or a spherical shape.

The frame 18 is preferably made thin in consideration of sensitivity and is preferably made thick in consideration of strength. For example, the frame 18 has a thickness of 0.1 mm to 1 mm in consideration of both sensitivity and strength. It is desirable to be formed.
Further, the frame body 18 is not limited to the quadrangular shape in order to avoid the influence of degeneracy, and may be formed in other shapes such as a circular shape and an octagonal shape. Further, the frame body 18 has an acceleration in the direction of the first axis (horizontal axis X) and a second axis (vertical axis Y).
In order to avoid the influence of the acceleration in the direction of, the width (width of each of the vibration plates 20a to 20d) is preferably sufficiently wider than the thickness.

In order to attach the frame 18 to the substrate 24, instead of using the support portions 22a to 22d, a cushioning material such as synthetic resin or rubber is interposed between the frame 18 and the substrate 24, and The 18 and the cushioning material and the substrate 24 may be connected by, for example, screwing, soldering, silver brazing, adhesive, double-sided adhesive tape, or the like.

As the substrate 24, a ceramic substrate made of alumina or the like or a glass substrate can be used in addition to the glass-epoxy type printed substrate.

In order to bond the substrate 24 to other members, a buffer material such as synthetic resin or rubber is used for the substrate 24.
And other members, the substrate 24, the cushioning material, and the other members are, for example, screwed, soldered, silver brazed,
It may be joined with an adhesive, a double-sided adhesive tape, or the like.

Further, in the above-described embodiment, the vibration plates 20a-2
Although 0d flexurally vibrates, in the present invention, the diaphragm 20a.
20d may be vibrated in other modes, or the diaphragms 20a-20d may not be vibrated by removing the oscillator circuit and its associated resistors and piezoelectric elements.

Further, the polarization direction of the piezoelectric layer of the piezoelectric element may be changed according to the phases of the driving means, the first detecting means and the second detecting means. For example, the polarization directions of the piezoelectric plate layers of all the piezoelectric elements may be reversed from the above-mentioned embodiment.

Further, in order to obtain a signal corresponding to the acceleration rotating about the first axis (horizontal axis X), the difference between the signals generated in the two piezoelectric elements 26a1 and 26c2 is detected in the above-mentioned embodiment. However, the sum of the signals generated in the two piezoelectric elements 26a1 and 26c4 may be detected, for example. Similarly, in order to obtain a signal corresponding to the acceleration that rotates about the second axis (vertical axis Y),
In the embodiment described above, two piezoelectric elements 26b1 and 26d
The difference between the signals generated in 2 is detected.
The sum of the signals generated by the two piezoelectric elements 26b1 and 26d4 may be detected.

Further, in the above-described embodiment, four piezoelectric elements are formed on each of the vibrating plates 20a to 20d of the frame body 18, but one piezoelectric element is formed on each central portion of the vibrating plates 20a to 20d. May be formed. In this way, the frame 18
The number and the position of the piezoelectric elements formed in the above may be arbitrarily changed.

[Brief description of drawings]

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

FIG. 2 is a first oscillation circuit used in the embodiment shown in FIG.
3 is a block diagram showing the detection circuit and the second detection circuit of FIG.

FIG. 3 is an illustrative view showing a vibration state of a vibrator of the example shown in FIG.

FIG. 4 is an illustrative view showing a deformed state of a vibrator when an acceleration that rotates about a first axis (horizontal axis X) is applied in the embodiment shown in FIG.

FIG. 5 is an illustrative view showing a deformed state of the vibrator when an acceleration that rotates about a second axis (vertical axis Y) is applied in the embodiment shown in FIG. 1;

FIG. 6 is an illustrative view showing a deformed state when acceleration is applied in the thickness direction (direction of axis Z) in the embodiment shown in FIG. 1.

[Explanation of symbols]

 10 Accelerometer 12 Vibrator 14 Weight 16a-16d Coupling part 18 Frame 20a-20d Vibration plate 22a-22d Support part 24 Substrate 26a1-26a4 Piezoelectric element 26b1-26b4 Piezoelectric element 26c1-26c4 Piezoelectric element 26d1-26d4 Piezoelectric element 28a1- 28a4 resistance 28b1 to 28b4 resistance 28c1 to 28c4 resistance 28d1 to 28d4 resistance 30 oscillation circuit 32 amplification circuit 34 phase correction circuit 40 first detection circuit 42 first differential circuit 44 first synchronous detection circuit 50 second detection circuit 52 Second Differential Circuit 54 Second Synchronous Detection Circuit

Claims (2)

[Claims] 1. A weight, two first coupling portions provided on a first axis, and two second coupling portions provided on a second axis orthogonal to the first axis.
A frame body that is coupled to the weight via a coupling portion of the frame body and is disposed around the weight body; a first piezoelectric element provided in the frame body in the vicinity of the second coupling portion; An acceleration sensor, comprising: a second piezoelectric element provided near the first coupling portion. 2. A first detecting means connected to the first piezoelectric element, for detecting a signal corresponding to an acceleration rotating about the first axis, and connected to the second piezoelectric element. The acceleration sensor according to claim 1, further comprising: second detection means for detecting a signal corresponding to an acceleration that rotates about the second axis.