KR101608153B1 - Acceleration Sensor for Vector Hydrophone - Google Patents

Abstract

According to the present invention, provided is an acceleration sensor which comprises: a disk-shaped base; a first piezoelectric material attached to a first surface of the base; a first mass attached to the first piezoelectric material; a second piezoelectric material attached to a second surface corresponding to the opposite side of the first surface of the base; and a second mass attached to the second piezoelectric material. The center of the first piezoelectric material and the center of the second piezoelectric material are arranged to be matched. In addition, an aluminum tube receiving the acceleration sensor inside the tube is provided.

Description

Acceleration Sensor for Vector Hydrophone < RTI ID = 0.0 >

The present invention relates to an acceleration sensor for applying to a vector hydrophone, and more particularly, to an acceleration sensor using a piezoelectric single crystal.

The acceleration sensor processes the output signal to measure dynamic forces such as acceleration, vibration, and shock of the object. The acceleration sensor is used in various fields, for example, in a control system of a transportation means, a factory automation and a robot, and is also incorporated in a communication device. If the acceleration sensor is classified into the detection method, it can be classified into inertia type, gyro type, and silicon semiconductor type.

The inertial acceleration sensor includes an acceleration sensor using a piezoelectric material. An example of a piezoelectric material widely used at present is lead zirconate titanate (PZT) ceramics. The acceleration sensor using the PZT ceramics has been improved for a long time, but it is difficult to further improve the performance due to the limitation of the piezoelectric material itself.

To solve this problem, an alternative using a PMN-PT single crystal as a piezoelectric material has been proposed. PZT ceramics are made of irregular grains while PMN-PT monocrystals have a structure in which fine grains having a certain structure are regularly arranged. The PMN-PT single crystal exhibits excellent physical properties as compared with PZT ceramics, and therefore performance improvement can be achieved when used as a piezoelectric material in an acceleration sensor.

Specifically, the PMN-PT single crystal is a solid solution single crystal of magnesium niobate (PMN), which is a relaxor, and titanic acid lead (PT), which is a piezoelectric material. When a PMN-PT single crystal is used as a piezoelectric material in an acceleration sensor, the piezoelectric distortion is three times or more larger than that of a conventional piezoelectric material of PZT ceramics, the electromechanical coupling coefficient is large, .

On the other hand, a vector hydrophone is a water-borne surveying instrument and has an accelerometer composed of a piezoelectric material. In the vector hydrophone, the force of the sound wave is transmitted to the body constituting the base of the accelerometer, whereby the accelerometer senses the pressure, and the direction of the sound wave can be detected from the electrical signal.

U.S. Patent No. 7,066,026 B2 discloses an accelerometer using a PMN-PT single crystal and an acoustic vector sensor having the accelerometer. The accelerometer disclosed in the above-mentioned United States patent discloses a structure in which a piezoelectric material composed of a PMT-PT single crystal is disposed between a mass and a base, and a cast pattern (a protrusion and a recess) is formed between the piezoelectric material and the mass, castellated pattern to reduce the negative effect on the relaxor crystal.

On the other hand, the acoustical vector sensor disclosed in the U.S. patent includes three accelerometers disposed on the inner circumference of the cylindrical housing. Each of the piezoelectric materials included in each of the accelerometers is cut in a specific orientation so as to generate a maximum piezoelectric response in the first direction, In the second direction and the third direction, which are the first and second directions. Therefore, the three accelerometers provided in the acoustic vector sensor are installed inside the cylindrical housing so that the orientations of the respective piezoelectric materials are orthogonal to each other, and the direction of the sound wave can be determined from the different signals detected from the three accelerometers have.

The accelerometer disclosed in the U.S. patent shows superior performance to an accelerometer using a PZT piezoelectric material by using a PMN-PT single crystal as a piezoelectric material. However, when used in an acoustic vector sensor or the like, two or more accelerometers must be included, and it is not easy to install the accelerometer in the cylindrical housing of the acoustic vector sensor disclosed in the U.S. patent.

It is an object of the present invention to develop an improved shear-type acceleration sensor applied to a vector hydrophone.

Another object of the present invention is to provide an acceleration sensor using a PMN-PT single crystal.

It is another object of the present invention to provide an acceleration sensor capable of detecting an acceleration in at least one direction.

In order to achieve the above object, according to the present invention,

Disk shaped base;

A first piezoelectric member attached to a first surface of the base;

A first mass attached to the first piezoelectric body;

A second piezoelectric attached to a second surface opposite to the first surface of the base; And

And a second mass attached to the second piezoelectric body,

And the center of the first piezoelectric body and the center of the second piezoelectric body coincide with the center of the base.

According to an aspect of the present invention, the first piezoelectric body and the second piezoelectric body are attached to the base such that the direction in which the maximum piezoelectric response of the first piezoelectric body is obtained and the direction in which the maximum piezoelectric response of the second piezoelectric body is obtained is perpendicular to each other .

According to another feature of the invention, the base is formed with holes symmetrically disposed in the center of the base.

According to another aspect of the present invention, the holes are arranged so as not to interfere with the at least one first piezoelectric substance and the at least one second piezoelectric substance.

Further, according to the present invention, an aluminum tube accommodating the acceleration sensor is included.

According to another aspect of the present invention, the acceleration sensor is accommodated inside the hydrophone in combination with the tube.

The shear-type acceleration sensor according to the present invention can improve the sensing performance by using a PMN-PT single crystal as a piezoelectric material. Also, since it has a simple structure, it is easy to manufacture and easy to handle.

1 is an exploded perspective view of a shear-type acceleration sensor according to an embodiment of the present invention.
2 is an exploded perspective view of a portion of a tube having a shear-type acceleration sensor according to the present invention.
3 is a schematic cross-sectional view of a shear-type acceleration sensor according to the present invention.

1 is a schematic exploded perspective view of an acceleration sensor according to a preferred embodiment of the present invention. Referring to the drawings, an acceleration sensor according to the present invention includes a disk-shaped base 10; A first PMN-PT piezoelectric element 11 attached to the first surface 10a of the disk-shaped base 10; A first mass body 12 attached to the first PMN-PT piezoelectric body 11; At least one second PMN-PT piezoelectric body (13) attached to a second surface (10b) opposite to the first surface (10a) of the disc-shaped base (10); And a second mass body (14) attached to the at least one second PMT-PT piezoelectric body (13).

The disk-shaped base 10 is formed as a thin circular plate as shown in the figure, and it is preferable that at least one hole 10c is formed. In the example shown in the drawing, four holes 10c are formed symmetrically with respect to the center of the disk-shaped base 10. It is preferable that each of the four holes 10c is formed so as not to interfere with the first PMN-PT piezoelectric body 11 and the second PMN-PT piezoelectric body 12 attached to the disk- That is, it is preferable that the holes 10c are formed so as not to be blocked by the PMN-PT piezoelectric body 12. [ The holes 10c serve as through holes for the electric cables to be connected to the electrodes of the first PMN-PT piezoelectric body 11 and the second PMN-PT piezoelectric body 12, . The disk-shaped base 10 is preferably, for example, about 20 mm in diameter, about 2 mm in thickness, and about 4 g in weight. The disc-shaped base 10 may be made of a general SUS material.

The first PMN-PT piezoelectric substance 11 and the second PMN-PT piezoelectric substance 13 are formed of PMN-PT piezoelectric single crystal. The first PMN-PT piezoelectric body 11 and the first PMN-PT piezoelectric body 13 may be provided as one member, and the center of the base 10 and the centers of the PMN-PT piezoelectric bodies 11, Respectively. At this time, it is preferable that the holes formed in the base 10 and the PMN-PT piezoelectric elements 11 and 13 do not interfere with each other. Each of the PMN-PT piezoelectric elements preferably has a rectangular parallelepiped shape having a predetermined length (L1), a width (W1), and a thickness (T1), for example.

Each of the first PMN-PT piezoelectric element 11 and the second PMN-PT piezoelectric element 13 generates a maximum piezoelectric response in the first direction, while the second PMN-PT piezoelectric element 11 generates the maximum piezoelectric response in the first direction, Lt; RTI ID = 0.0 > a < / RTI > minimum piezoelectric response. Thus, if the first PMN-PT piezoelectric body 11 and the second PMN-PT piezoelectric body 13 all have the same shape and have the same orientation, the first PMN-PT piezoelectric body 11 and the second PMN- 13 are arranged at right angles to each other so that the direction in which the first PMN-PT piezoelectric element 11 generates the maximum piezoelectric response and the direction in which the second PMN-PT piezoelectric element 13 generates the maximum piezoelectric response are orthogonal to each other . For example, in the X-Y-Z coordinate system, the first PMN-PT piezoelectric element 11 has the maximum piezoelectric response in the Z direction, while minimizing the piezoelectric response in the X and Y directions. Further, the second PMN-PT piezoelectric substance 13 has the maximum piezoelectric response in the Y direction, while the piezoelectric response in the X and Z directions is the minimum. Typically, the maximum piezoelectric response is measured to be twice the minimum piezoelectric response, and this difference can be used to detect the direction of the sound waves.

The first mass body 12 is attached to the first PMN-PT piezoelectric body 11 so that the first PMN-PT piezoelectric body 11 is disposed between the base 10 and the first mass body 12. Similarly, the second mass body 14 is attached to the second PMN-PT piezoelectric body 13, so that the second PMN-PT piezoelectric body 13 is disposed between the base 10 and the second mass body 14. [ Each of the first mass body 12 and the second mass body 14 is preferably composed of a rectangular parallelepiped having a predetermined length L2, a width W2, and a thickness T2. The first mass body 12 and the second mass body 14 may be made of a general SUS material.

The bonding of the disk-shaped base 10, the first PMN-PT piezoelectric body 11, the first mass body 12, the first PMN-PT piezoelectric body 13 and the second mass body 14 can be performed using an adhesive .

Electrical connection to the piezoelectric body is achieved by coating conductive electrodes on both surfaces of the piezoelectric body. That is, both surfaces of the first PMN-PT piezoelectric body 11 in contact with the first mass body 12 and the disk-shaped base 10 are coated with electrodes, and similarly, the second PMN- Like base 14 and the disk-shaped base 10, respectively. A wire (not shown) is connected to the first mass body 12, the second mass body 14 and the disk-shaped base 10 using a silver paste, a + signal is received at each mass, Can be received in common from the base 10.

Figs. 2 and 3 show a schematic structure of the acceleration sensor shown in Fig. 1 as an exploded perspective view and a cross-sectional view.

2, the acceleration sensor 1 according to the present invention includes a first PMN-PT piezoelectric body 11 and a mass on a first surface of a disk-shaped base 10 as described with reference to FIG. 1 And a second PMN-PT piezoelectric substance and a mass on a second surface not shown in the drawing. The acceleration sensor 1 constructed as described above is inserted into the cylindrical aluminum tube 21. The inside diameter of the cylindrical aluminum tube 21 corresponds to the diameter of the disk-shaped base 10.

In the example shown in the figure, the acceleration sensor 1 is installed in an aluminum tube 21 in a tight fitting manner. However, in another example not shown in the drawing, the acceleration sensor 1 is disposed between the opposite ends of the two aluminum tubes 21, and the two aluminum tubes are joined in the same manner as the butt welding, Can be deployed.

Referring to FIG. 3, the base 10 of the acceleration sensor 1 is fixed to the inner surface of the cylindrical aluminum tube 21.

When a force is applied to the rigid aluminum tube 21 in the above configuration, the two piezoelectric bodies are pressed between the base 10 and the masses 12 and 14, thereby outputting different piezoelectric response signals. Therefore, the direction of the force can be detected by analyzing the different piezoelectric response signals.

1. Accelerometer 10. Base
11. First PMN-PT piezoelectric body 12. First mass body
13. Second PMN-PT piezoelectric body 14. Second mass body
21. Aluminum tubes

Claims (5)

Disk shaped base;
A first piezoelectric member attached to a first surface of the base;
A first mass attached to the first piezoelectric body;
A second piezoelectric attached to a second surface opposite to the first surface of the base; And
And a second mass attached to the second piezoelectric body,
The center of the first piezoelectric body and the center of the second piezoelectric body coincide with the center of the base,
Wherein the base is formed with holes symmetrically disposed in the center of the base. The method according to claim 1,
Wherein the first piezoelectric body and the second piezoelectric body are attached to the base such that the direction in which the maximum piezoelectric response of the first piezoelectric body is obtained and the direction in which the maximum piezoelectric response of the second piezoelectric body is obtained are orthogonal to each other. delete The method according to claim 1,
And the holes are arranged so as not to interfere with the first piezoelectric body and the second piezoelectric body. The method according to claim 1,
Wherein the acceleration sensor comprises an aluminum tube and has a structure accommodated in an aluminum tube.

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