JPS60180181A - Underwater use coaxial type piezoelectric cable - Google Patents

Abstract

PURPOSE:To improve an SN ratio by mutually off-setting charges generating in a piezoelectric outer layer and a piezoelectric inner layer by each electrical connection and preventing the effect of acoustic waves to be exerted on the piezoelectric inner layer by a sound-insulating layer when a piezoelectric cable is bent by external pressure. CONSTITUTION:When a piezoelectric inner layer 2 and a piezoelectric outer layer 8 concentrically formed through a sound-insulating layer 5 are wired so that a positive pole for the piezoelectric inner layer 2 is connected to a negative pole for the piezoelectric outer layer 8 and a negative pole for the piezoelectric inner layer 2 to a positive pole for the piezoelectric outer layer 8, output signals are lead out of both poles for the piezoelectric outer layer 8 and a piezoelectric cable is bent by external pressure, charges generated in the piezoelectric inner layer 2 and the piezoelectric outer layer 8 are denied mutually by each electrical connection. Accordingly, outputs corresponding to acoustic waves generated only in the piezoelectric outer layer 8 can be extracted while an effect due to external stress such as waving is removed to the minimum possible, and the S/N ratio of the outputs can be improved remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an underwater coaxial piezoelectric cable that is suitably used as a hydrophone for submarine seismic exploration and fish detection, and as an acoustic probe in the cleaning liquid of an ultrasonic cleaning device.

Ferroelectric ceramic particles such as lead zirconia titanate and lead titanate are incorporated into piezoelectric organic materials such as polyvinylidene fluoride, polyvinyl fluoride, polyvinylidene chloride, polyvinyl chloride, and nylon, or organic materials such as synthetic rubber and synthetic resin. Organic piezoelectric materials, such as piezoelectric organic ceramic composites, have characteristics in which their acoustic impedance approximates that of water, compared to general sintered piezoelectric ceramic materials. When used as a piezoelectric transducer, it has the advantage of efficiently receiving acoustic waves propagating in water and increasing sensitivity.

Therefore, as shown in FIG. 1, a coaxial piezoelectric cable is formed by arranging the organic piezoelectric layer a around the center conducting wire and arranging a conductive material C such as a conductive paint around the outer periphery of the piezoelectric material. However, there is a coaxial type piezoelectric cable which is immersed in water to extract an output signal from between the center conducting wire and the conductive material C to receive acoustic waves propagating in the water.

By the way, since the piezoelectric cable having the above structure is flexible, it bends due to pressure other than acoustic waves, such as flowing water, external stress, etc., and therefore bending stress acts on the piezoelectric layer a, causing an electric charge. This has the drawback that it becomes a noise signal that is added to the acoustic wave in a superimposed manner, reducing the S/N ratio.

The present invention aims to eliminate the drawbacks of the conventional structure, and includes an inner piezoelectric layer and an outer piezoelectric layer made of an organic piezoelectric material, which are provided concentrically with a sound insulating layer in between, and a positive electrode of the piezoelectric inner layer. The negative electrode of the piezoelectric outer layer and the negative electrode of the piezoelectric inner layer are respectively electrically connected to the positive electrode of the piezoelectric outer layer, and output signals are taken out from both poles of the piezoelectric outer layer. When the piezoelectric cable is bent by external pressure, the piezoelectric Electric charges generated in the outer layer and the inner piezoelectric layer are canceled out by their respective electrical connections, and the influence of acoustic waves is prevented from affecting the inner piezoelectric layer by a sound insulating layer, so that the output corresponding to the acoustic waves is transmitted from the outer piezoelectric layer. It is designed so that it can be taken out.

An embodiment of the invention will be described with reference to the accompanying drawings.

Reference numeral 2 denotes a piezoelectric inner layer made of piezoelectric rubber or the like, which is polarized so that its inner side is positive and its outer side is negative, and a central electric wire 1 passes through its center. An electrode 3 made of conductive paint or the like is formed around the piezoelectric inner layer 2, and an extraction electrode 114 is wound around the outer periphery of the electrode 3. Further, on the outside thereof, a sound insulating layer 5 made of foam material, cloth, paper, etc. is provided. Further, a conductive rubber 6 is provided around the sound insulating layer 5, and a lead-out electrode wire 7 is wound around the conductive rubber 6.

Reference numeral 8 denotes a piezoelectric outer layer made of piezoelectric rubber or the like, with the inner side polarized positively and the outer side negatively polarized, and an electrode 9 formed by applying a conductive paint is provided on the circumferential surface of the piezoelectric outer layer 8. A conductive braided fiber lO is applied to its outer periphery.

The coaxial piezoelectric cable formed by
The central electric wire 1 connected to the electrode side and the composite fiber 10 connected to the negative electrode of the piezoelectric outer layer 8 are electrically connected by a lead wire 11, the end thereof is used as an output terminal 12, and the piezoelectric inner layer 2
The electrode wire 4 connected to the negative electrode of the piezoelectric outer layer 8 and the electrode wire 4 connected to the positive electrode side of the piezoelectric outer layer 8 are connected by a lead wire 13,
The end thereof is used as an output terminal 14, and the output terminal 12.14
The output signal is extracted from between the two. Note that the output terminal 12 is on the ground side.

To explain the operation of the embodiment, when the piezoelectric cable is bent in a wave shape or the like, bending stress is applied to the piezoelectric inner layer 2 and the piezoelectric outer layer 8, and charges are generated in each of them. by the way,
The bending causes the piezoelectric inner layer 2. The amount of charge generated in the piezoelectric outer layer 8 is almost the same, and as described above, the amount of charge generated in the piezoelectric inner layer 2 is almost the same.
The positive electrode of the piezoelectric outer layer 8 and the negative electrode of the piezoelectric outer layer 8 are electrically connected by a lead wire 11, and the negative electrode of the piezoelectric inner layer 2 and the positive electrode of the piezoelectric outer layer 8 are electrically connected by a lead wire 13. Therefore, they cancel each other out, and as a result, no potential difference is generated between the output terminals 12 and 14 due to external stress such as the waveform. On the other hand, the influence of acoustic waves acts on the piezoelectric outer layer 8 from the entire outer circumference of the cable, but is buffered by the sound insulating layer 5 and does not act on the piezoelectric inner layer 2. For this reason, electric charges are generated only in the piezoelectric outer layer 8 due to the acoustic waves, and as a result, as described above, the generation of potential due to external stress such as waveforms is eliminated, and therefore the terminals 12 and 14 correspond to the acoustic waves. Only those electrical signals are extracted. Therefore, only acoustic waves can be received without being affected by the curvature.

In the embodiment, the piezoelectric inner layer 2. The polarization direction of the piezoelectric outer layer 8 can be arbitrarily selected, but in this case as well, the positive electrode of the piezoelectric inner layer 2 is connected to the negative electrode of the piezoelectric outer layer 8, and the negative electrode of the piezoelectric inner layer 2 is connected to the positive electrode of the piezoelectric outer layer 8, respectively. connection is required.

Moreover, the sound insulation effect can be improved by making the sound insulation layer 5 interposed between the piezoelectric inner layer 2 and the piezoelectric outer layer 8 multilayer and increasing its thickness.

As clarified by the above description, the present invention provides a piezoelectric inner layer 2 and a piezoelectric outer layer 8 that are concentrically provided with a sound insulating layer 5 in between.
are wired so that the positive electrode of the piezoelectric inner layer 2 is connected to the negative electrode of the piezoelectric outer layer 8, and the negative electrode of the piezoelectric inner layer 2 is connected to the positive electrode of the piezoelectric outer layer 8, and output signals are taken out from both poles of the piezoelectric outer layer 8. When the piezoelectric cable is bent due to external pressure, the electric charges generated in the piezoelectric inner layer 2 and the piezoelectric outer layer 8 are canceled by each electrical connection, so that the piezoelectric outer layer 8
It has excellent features such as being able to extract the output corresponding to the acoustic waves that occur only in effective.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a conventional device, Figs. 2 and 3 show an embodiment of the present invention, Fig. 2 is a perspective view, and Fig. 3 is a longitudinal sectional view. 1; Center electric wire 2; Piezoelectric inner layer 5; Sound insulation layer 8; Piezoelectric outer layer 12, 14. Output terminal younger brother 1 diagram

Claims (1)

[Claims] An inner piezoelectric layer and an outer piezoelectric layer made of an organic piezoelectric material are provided concentrically with a sound insulating layer in between, and the positive electrode of the piezoelectric inner layer is connected to the negative electrode of the piezoelectric outer layer, and the negative electrode of the piezoelectric inner layer is connected to the positive electrode of the piezoelectric outer layer, respectively. An underwater coaxial piezoelectric cable characterized in that it is electrically connected and output signals are taken out from both poles of the piezoelectric outer layer.