JP2747593B2 - Piezoelectric cable for towing and its heating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention has one end supported on the stern of an oceanographic research ship or the like,
The present invention relates to a towed piezoelectric cable that receives acoustic waves generated in water while being towed in a stream in the sea, and is suitably used for seafloor seismic exploration, fish finder, and the like.

<Prior Art> A towed piezoelectric cable x used for seafloor seismic exploration, fish detection, etc., is connected to a winch z disposed at the stern of a ship y as shown in FIG. 7 or FIG. As a result, it becomes freely retractable, is pulled out from the winch, and is towed in water.

The piezoelectric cable x includes one using a sintered piezoelectric ceramic material and one using a piezoelectric organic substance or a piezoelectric organic ceramic composite.

A conventional configuration using the latter piezoelectric organic material or piezoelectric organic ceramic composite will be described.

Ferroelectric ceramic particles such as lead zirconate titanate and lead titanate in a piezoelectric organic material such as polyvinylidene fluoride, polyvinyl fluoride, polyvinylidene chloride, polyvinyl chloride, and nylon, or an organic material such as synthetic rubber or synthetic resin. A piezoelectric organic substance or a piezoelectric organic ceramic composite obtained by mixing has a characteristic that its acoustic impedance is close to the acoustic impedance of water. Therefore, when this is used as a piezoelectric cable x, an acoustic wave propagating in water is generated. There is an advantage that the wave can be received efficiently and the sensitivity can be increased.

Therefore, as shown in FIG. 9, a piezoelectric layer h made of the piezoelectric material is arranged around an electrode core i, and an outer electrode j such as a conductive paint is arranged around the outer periphery of the piezoelectric layer h. A predetermined DC voltage is applied between the electrode core j and the outer electrode j to form a coaxial piezoelectric cable x in which the piezoelectric layer h is radially polarized. There is an apparatus which takes out an output signal from the apparatus and receives an acoustic wave propagating in the underwater.

On the other hand, in addition to using one such long structure, as shown in FIG. 8, a short cable unit u having the same structure as described above may be provided, and a plurality of such cable units may be vertically connected. Can be In the piezoelectric cable x, a phase difference is generated between a signal received from the cable unit u near the sound source o and a signal received from the cable unit u at a position separated from the cable unit u. Therefore, the direction of the sound can be detected using this phase difference. In this case, since the output from each cable unit u needs to be separately taken out through a conductor, a configuration that allows a large number of conductors to be taken out is required.

<Problems to be Solved by the Invention> In the conventional towing piezoelectric cable using the piezoelectric organic substance or the piezoelectric organic ceramic composite,
It is wound up by the winch z and pulled out when necessary.
For this reason, as shown in FIG. 10, the cable is curled and deformed into a wavy shape when used. Then, when the piezoelectric cable is towed, cavitation and turbulence easily occur around the cable, and an unnecessary signal called flow noise is generated.

An object of the present invention is to eliminate the disadvantages of the conventional configuration.

<Means for Solving the Problems> The towed piezoelectric cable according to the first invention of the present application is provided with a piezoelectric layer made of a piezoelectric organic substance or a piezoelectric organic ceramic composite on which electrodes are respectively provided inside and outside, and a stern. In a cable that can be wound around a winch disposed in the tow and is pulled out from the winch and towed in water, a core wire made of a shape memory alloy that is linearly stored in a shape is disposed in a cable, It is characterized in that it is heated when it is pulled out of the winch and is returned to a linear shape by the shape restoring action of the shape memory alloy.

A towed piezoelectric cable according to a second aspect of the present invention has the above-described configuration, and uses a holding tube body concentric with the cable as the shape memory alloy.

The heating method of the third invention is characterized in that electromagnetic heating is used as means for restoring the towed piezoelectric cable incorporating the shape memory alloy in the longitudinal direction.

<Operation> In the towed piezoelectric cable of the first and second inventions,
The shape memory alloy is stored in a linear shape in advance, and when the cable is heated while sending out the piezoelectric cable from the winch z, the memory is restored to the linear shape. Therefore, even if the piezoelectric cable is wound by the winch z, the piezoelectric cable does not curl, and the piezoelectric cable is sent straight out.

In some cases, the shape memory alloy may be stored in another desired shape depending on the application.

In the third invention, since the memory is restored by electromagnetic heating, the shape memory alloy can be heated intensively. Therefore, unlike the case where heat is transferred from the piezoelectric organic substance or the piezoelectric organic ceramic composite to the shape memory alloy sequentially as in the case of heating with a normal heater, the piezoelectric organic substance or the piezoelectric organic ceramic composite is overheated. There is no adverse effect such as a decrease in sensitivity.

<Embodiment> Figs. 1 and 2 relate to an embodiment in which a core wire 1 made of a shape memory alloy is applied to the center of a towed piezoelectric cable x.

Here, reference numeral 2 denotes a piezoelectric layer made of a piezoelectric organic material such as a piezoelectric rubber or a piezoelectric organic ceramic composite. Is provided with a protective coating layer 4.
At the center thereof, a core wire 1 made of a shape memory alloy penetrates. This core wire 1 can also serve as an inner electrode of the piezoelectric layer 2. Note that an inner electrode may be separately provided.

The piezoelectric layer 2 is made of an organic material exhibiting piezoelectricity itself such as polyvinylidene fluoride or the like, or a synthetic resin organic material containing lead titanate (PbTiO ₃ ) or lead zirconate titanate (PbTiO ₃ ).
It is formed from a piezoelectric composite obtained by mixing ferroelectric ceramic particles such as (Ti.Zr) O ₃ ).

In the piezoelectric cable x thus formed, the core wire 1 also serving as an electrode of the piezoelectric layer 2 and the outer electrode 3 are electrically connected by the conductive wires 6 and 6, and the ends thereof are used as the output terminals 7 and 7. ,
An output signal is taken out from between the output terminals 7,7.

The core wire 1 is not necessarily limited to the center of the cable, for example, being inserted around the plurality of piezoelectric layers 2.

This configuration is suitable for forming a long piezoelectric cable x.

Next, FIGS. 3 to 6 show an embodiment of a towed piezoelectric cable x provided with a holding tube.

Here, FIGS. 3 and 4 show that the outer electrode 12a is formed by applying a conductive paint on the peripheral surface of the annular piezoelectric layer 11a made of an annular piezoelectric organic material or a piezoelectric organic ceramic composite, and furthermore, a protective coating is provided on the outer periphery thereof. The piezoelectric layer 1 on the layer 13a
A holding tube body 10a made of a shape memory alloy is provided on the inner peripheral surface of 1a. The holding tube body 10a also serves as an inner electrode of the piezoelectric layer 11a.

In this configuration, an inner space 15 is provided at the center by a holding tube 10.
Is formed. Therefore, the above configuration is made to be short, and the end of each inner space 15 is shielded to form a cable unit u as a cavity. And the conducting wire 1 electrically connected to the holding tube body 10.
By inserting 6, the piezoelectric cable x that can confirm the direction of the sound wave source by the difference in the phase difference shown in FIG. 8 can be constructed.

Further, in the cable unit u, the specific gravity of the whole can be adjusted by the inner space 15. In this regard, in the past, the specific gravity was adjusted by injecting oil into the hose, but since it is based on the air layer, there is an advantage that the adjustment can be performed without adverse effects such as oil leakage.

In this embodiment, in the state of being wound by the winch z, the sheet is crushed into a flat shape. However, when the sheet is drawn out while being heated, it can be almost straightened.
Curling is prevented.

Incidentally, the piezoelectric cable x may be configured as it is by making the configuration of FIGS. 3 and 4 long.

FIG. 5 shows that the outer electrode 12b
And a holding tube 10b made of a shape memory alloy is disposed on the inner peripheral surface of the piezoelectric layer 11b in which the protective coating layer 13b is sequentially formed, and furthermore, the inside of the holding tube 10b is filled with a damping material 17. It is something to do.

In FIG. 6, the holding tube body 10c is provided outside the piezoelectric layer 11c to serve also as an outer electrode, and an electrode core 18 serving as an inner electrode is inserted through the center thereof.

In the configuration shown in FIGS. 3 to 6, the holding tube may be stored in a flat shape, and the flat piezoelectric cable x may be formed.

The shape wire of the core wire 1 and the holding tubes 10a to 10c made of the shape memory alloy needs to be heated. Therefore, as shown in FIG. 7, an electromagnetic heating furnace 20 having a structure similar to that of a microwave oven is provided further behind a winch z provided at the stern of the ship y, and guide rolls 21a and 21b are provided at the entrance and exit thereof. The piezoelectric cable x is made to travel in the outer electromagnetic heating furnace 20. Thus, unlike the heat transfer from the outer periphery, the core wire 1. The holding tube body 10 can be effectively heated, and can be returned to the memorized shape.

<Effects of the Invention> As is clear from the above description, the present invention provides a core wire 1 or a holding tube 10 made of a shape memory alloy in a piezoelectric cable x, and sets the memory shape to a straight line,
Since the shape is restored by heating when it is pulled out from the winch z, it is possible to prevent curling due to the winch z, maintain the proper shape, reduce the occurrence of flow noise, and significantly reduce the S / N ratio. Can be improved.

Furthermore, when the heating is performed by electromagnetic heating, excellent effects such as efficient heating of the core wire 1 or the holding tube 10 can be achieved without deterioration of characteristics due to polarization breakdown of the piezoelectric layer. There is.

[Brief description of the drawings]

FIG. 1 is a vertical side view of one embodiment of the first invention, FIG. 2 is a perspective view of the same, FIG. 3 is a vertical side view of the first embodiment of the second invention,
FIG. 4 is a perspective view of the same, FIG. 5 is a vertical side view of the second embodiment, FIG. 6 is a vertical side view of the third embodiment, FIG. The figure is a schematic side view of a piezoelectric cable x composed of a short cable unit u, FIG. 9 is a perspective view of a conventional structure, and FIG. 10 is a side view of the piezoelectric cable x showing a conventional defect. DESCRIPTION OF SYMBOLS 1 ... Core wire 2 ... Piezoelectric layer 3 ... Outer electrode 10a, 10b, 10c ... Holding tube body 11a, 11b, 11c ... Piezoelectric layer 12a, 12b, 12c ... Outer electrode 15 ... Inner space 20 ... ... Electromagnetic heating furnace x ... Piezoelectric cable, z ... Winch, u ... Cable unit

Claims (3)

(57) [Claims] A piezoelectric layer made of a piezoelectric organic substance or a piezoelectric organic ceramic composite on which electrodes are respectively disposed inside and outside, and can be freely wound around a winch disposed on the stern;
In a cable pulled out from the winch and towed in water, a core wire made of a shape memory alloy having a linear shape memory is arranged in a cable, and heated when being pulled out from the winch, and A towed piezoelectric cable, which is returned to a linear shape by a shape returning action of a memory alloy. 2. A piezoelectric layer comprising a piezoelectric organic substance or a piezoelectric organic ceramic composite on which electrodes are respectively disposed inside and outside, and can be wound around a winch disposed on the stern,
In a cable pulled out from the winch and towed in water, a holding tube made of a shape memory alloy linearly stored in a cable is disposed concentrically with the cable and pulled out from the winch. A piezoelectric cable for towing, wherein the cable is heated and then returned to a linear shape by the shape returning action of the shape memory alloy. 3. A towed piezoelectric cable according to claim 1, wherein the towed piezoelectric cable is heated by electromagnetic heating to restore the shape memory alloy to memory. Heating method.