JPH01166697A - Submarine piezoelectric transmission and reception wave sheet - Google Patents

Abstract

PURPOSE:To improve the wave receiving sensitivity by providing an electrode to both upper and lower faces and swelling the square ridge of a metallic case covering a piezoelectric board polarized in the broadwise direction outward. CONSTITUTION:The piezoelectric plate 1 is formed by laminating two piezoelectric plate layers 2a, 2b of rectangular shape polarized in the broadwise direction in a manner of opposite polarized directions and electrodes 3, 4 are formed to the front and rear side of the piezoelectric plate layers 2a, 2b. A nearly rectangular metallic coating 10 is provided to the outer circumference of the piezoelectric pate 1, the upper/lower inner faces are in contact with the front rear sides of the piezoelectric plate 1 to form air gap 11 with the circumferential ridge of the piezoelectric plate and an outward swollen part 12 is formed over the entire circumference to the square ridge above and below the air gap. When a pressure P2 is exerted from the circumferential ridge, a force component P4 is generated by the swollen part 12 in a direction pressing the piezoelectric plate 1 vertically and it is applied in the same direction of the pressure P1 in the broadwise direction due to an acoustic wave to be received. Thus, the wave receiving sensitivity is improved.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is applicable to submarine seismic probes, fish finders, etc.
This relates to an underwater piezoelectric wave transmitting/receiving sheet that emits sound waves or ultrasonic waves into the water toward a detected object, or receives reflected waves that are reflected back from the detected object.

<Prior art> Piezoelectric organic materials such as polyvinylidene fluoride, polyvinyl fluoride, polyvinylidene chloride, polyvinyl chloride, and nylon, or strong organic materials such as lead zirconate titanate and lead titanate in the organic materials of synthetic rubber and synthetic resin. A piezoelectric flexible sheet such as a piezoelectric organic ceramic composite made of a mixture of dielectric ceramic particles has an acoustic impedance close to that of water, and therefore can be used as a piezoelectric transducer to propagate through water. It is used to receive acoustic waves.

In addition to this, some piezoelectric ceramic plates are used as piezoelectric transducers.

Furthermore, piezoelectric flexible sheets and piezoelectric ceramic plates can also be used as transmitters that radiate sound waves or ultrasonic waves toward an object to be detected.

In this underwater piezoelectric wave transmitting/receiving sheet using a piezoelectric plate made of a piezoelectric flexible sheet, a piezoelectric Mi plate, etc., as shown in Fig. 4, electrodes are formed on the top and bottom, and the electrodes are polarized in the thickness direction. The outer periphery of a piezoelectric plate a made by laminating two piezoelectric plate layers A and B such that their polarization directions are opposite is covered with a metal coating d having a substantially rectangular cross section, and the periphery of the piezoelectric plate A and the metal coating are A structure was proposed in which gaps e and e were formed between the inner surface of d and the front and back surfaces were brought into contact with the metal-coated inner surface.

Incidentally, the piezoelectric plate a can also be composed of only one piezoelectric plate layer.

A piezoelectric wave receiving sheet having such a structure can be immersed in water and an alternating voltage applied to the electrodes of each piezoelectric plate (b) to oscillate sound waves or ultrasonic waves from the main surface of the metal covering (ld), or The reflected wave is captured from the main surface of the metal covering LD, and an output signal is extracted from between the electrodes to receive the acoustic wave propagating in the water.

<Problems to be Solved by the Invention> When the piezoelectric plate a having the above configuration is used as a delivery device, it detects acoustic waves under hydrostatic pressure, and the sensitivity thereof depends on each piezoelectric plate layer. It is determined by the piezoelectric constant gh. This piezoelectric constant gh is given by the following equation.

g h :g 3s+ 2 g sr where constant g. represents the sensitivity to the pressure p1 in the thickness direction (polarization direction), and the constant gm+ represents the sensitivity to the pressure p2 in the planar direction (direction perpendicular to the polarization axis).

By the way, it's fixed! Since l g 3+ is a negative value, g
If n < g3s and the influence of pressure p2 is strong, only low sensitivity can be obtained.

This is the same when used as a wave transmitter, and the piezoelectric constant d7 decreases due to water pressure from the surface direction.

Therefore, in the conventional configuration, gaps e, e are formed between both side surfaces of the piezoelectric plate a and the inner surface of the metal covering lWd,
Pressure p2 from the outer surface direction is applied to the gap e.

This pressure component is buffered by the flexure of the metal coating d around e, thereby relieving this pressure component.

However, since each corner edge of the metal sheath d is curved, this force causes a bulge on the top and bottom surfaces of the metal sheath d, and as shown in Fig. 4, an external pressure in the thickness direction (polarization direction) is generated. Generates p3. Since this pressure acts in the opposite direction to the effective pressure p+, it ends up reducing the pressure in the thickness direction (polarization direction).

For this reason, even in the conventional configuration, the apparent underwater wave receiving sensitivity was reduced due to the influence of the pressure p2.

The present invention provides an underwater piezoelectric wave transmitting/receiving sheet that can eliminate the outward swelling of the upper and lower surfaces of the metal covering rMd due to the pressure p2 in the plane direction (direction perpendicular to the polarization axis) and improve the wave receiving sensitivity. This is the purpose.

<Means for Solving the Problems> The present invention is characterized in that outward bulges are formed on the corner edges of the metal coating.

In the above configuration, when pressure p2 is applied from the periphery of the piezoelectric plate in the in-plane direction (direction perpendicular to the polarization axis), the upper and lower surfaces are caused to move inward due to the bulges formed at each corner edge of the metal coating. Trying to expand. Therefore, the pressure p2 generates an inward component force p4 in the thickness direction. Therefore, since this pressure p4 is in the same direction as the pressure p due to one reflected wave, it acts in a direction that improves the transfer sensitivity.

<Example> In FIGS. 1 to 3, l is a piezoelectric plate, made of synthetic rubber,
Lead zirconate titanate (P) is added to organic base materials such as synthetic resins.
b(Ti-ZrlO-), lead titanate (PbTi03
) is made of a piezoelectric flexible sheet made of a composite material mixed with piezoelectric ceramic powder, or a piezoelectric ceramic sintered body.

two rectangular piezoelectric plate layers 2a polarized in the thickness direction;
2b are stacked on each other so that their polarization directions are opposite to each other. The front and back surfaces of the piezoelectric plate layers 2a and 2b are provided with electrodes 3.
4 is formed.

The outer periphery of the piezoelectric plate 1 is coated with a substantially rectangular metal coating 10 with a gap 11 placed around the periphery of the piezoelectric plate 1. Also,
The upper and lower inner surfaces of the metal covering 7110 are in contact with the front and back surfaces of the piezoelectric plate l.

On the entire circumference of the upper and lower corner edges of this gap 11, acute-angled bulges 12 and 12 are formed in the figure, which are the essential parts of the present invention.

Therefore, in a piezoelectric wave transmitting/receiving sheet having such a configuration,
When pressure p2 is applied from the periphery, the force is in the thickness direction and is caused by the bulge 12.12 on the metal coating 10.
This produces a force that causes the top and bottom of the to expand inward. The pressure P4 (see Fig. 3) due to this component force is the pressure p4 at which the metal coating lO comes into pressure contact with the front and back surfaces of the piezoelectric plate l, and is in the same direction as the pressure pl in the thickness direction due to the acoustic wave to be received, and the pressure Reinforce. Therefore, the delivery sensitivity is improved. An output signal due to the pressure wave in the thickness direction is generated between the electrodes 3.4 in each piezoelectric plate layer 2a, 2b, and the sum of this output is taken out by a connection means (not shown).

When the underwater reception sensitivity of the above example was compared with the conventional one, an improvement of 3.6 dB was observed as shown in the following table.

In the embodiment described above, the shape of the bulging portion 12.12 may be various, such as an arcuate shape, as long as it bulges out from around the corner edge of the metal sheath 11i10.

Furthermore, although the piezoelectric plate 1 is constructed by laminating two piezoelectric plate layers 2a and 2b, it can be constructed by one or more piezoelectric plate layers.

<Effects of the Invention> As clarified by the above description, the present invention has a bulge of 1111 m12 at the corner edge of the metal coating 10 covering the piezoelectric plate 1.
．． 12, the swollen portion 12° 12 converts the force in the thickness direction due to the force from the surface direction into a force that swells the upper and lower parts of the metal coating 10 inward. This component force does not reduce the reception sensitivity, but on the contrary, it has an excellent effect of improving the sensitivity.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway perspective view of a piezoelectric wave receiving sheet according to an embodiment of the present invention, Fig. 2 is a partially cutaway plan view of the same, Fig. 3 is a cross-sectional side view of the same layer, and Fig. 4 is a longitudinal cross-section of a conventional configuration. FIG. 1: Piezoelectric plate 10: Metal coating 1: Gap 12.12; Swelling part No. 2 (2) Fig. 4

Claims (1)

[Claims] 1) The outer periphery of a piezoelectric plate on which electrodes are formed on the upper and lower sides and polarized in the thickness direction is covered with a metal coating having a substantially rectangular cross section, and the periphery of the piezoelectric plate and the inner surface of the metal coating are An underwater piezoelectric wave transmitting/receiving device characterized in that an air gap is formed between the piezoelectric plates and the front and back surfaces of the piezoelectric plate are brought into contact with the inner surface of the metal coating, and an outward bulge is formed on the corner edge of the metal coating. sheet. 2) The underwater piezoelectric wave transmitting/receiving sheet according to claim 1, wherein the piezoelectric plate is a piezoelectric flexible sheet. 3) The underwater piezoelectric wave transmitting/receiving sheet according to claim 1, wherein the piezoelectric plate is a piezoelectric ceramic plate.