JP2587952B2 - Piezo cable for towing - 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 piezoelectric cable for towing, which receives acoustic waves generated in water while being towed in a windsock shape in the sea, and is preferably used for seafloor seismic exploration, fish detection, and the like.

<Prior Art> As shown in FIG. 14, a towing piezoelectric cable x used for seafloor seismic exploration and fish shoaling is connected to a winch z arranged at the stern of a ship y, as shown in FIG. It is towed freely.

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

Piezoelectric cable x using the former sintered piezoelectric ceramic material
In FIG. 10, as shown in FIG. 10, piezoelectric receiving units b are arranged at appropriate intervals in a flexible tube a, and each piezoelectric receiving unit b is connected by a conducting wire c. The tube a is filled with oil d having acoustic characteristics similar to the acoustic impedance of water.

The structure of the piezoelectric receiving unit b is such that a pair of piezoelectric ceramic plates e, e made of a ferroelectric material such as lead zirconate titanate and lead titanate, whose polarization directions are reversed, are brought into contact with each other. Two plate pairs f are arranged in a direction orthogonal to the axial direction,
Each of the opposed electrodes is short-circuited by the conductive path g. At this time, for example, in the upper piezoelectric element plate pair f, the opposing electrodes are negative, and in the lower frame piezoelectric element plate pair f, the positive and negative directions are reversed. (The arrow in the figure indicates the direction of polarization.) Then, each piezoelectric element plate pair f, f
Are connected to each other, and the respective outer surface electrodes are connected to the conductor c so that signals can be taken out from the conductor c.

In such a configuration, besides acoustic waves, for example, bending stress due to, for example, tensile stress or swinging at the time of blowing is applied to the piezoelectric cable x, and these mechanical stresses give strain to the piezoelectric ceramic plates e, e. A charge or voltage is generated, which becomes a noise signal and is superimposed on the acoustic wave, thereby lowering the S / N ratio.

Thus, in the above configuration, noise is removed by the following principle.

That is, when a force is applied in a direction perpendicular to the axis,
As shown in FIG. 12, the upper and lower piezoelectric element plate pairs f are each subjected to a bending distortion in the same direction.
And the charge generated between the electrodes facing the piezoelectric element plate pair f of the lower frame have the same absolute value and different polarities, and therefore cancel each other out. It does not occur as output.

Strain caused by the tensile force in the axial direction is also eliminated according to the same principle.

On the other hand, when receiving an acoustic wave, since the acoustic wave is received from the entire circumference of the piezoelectric receiving unit b, the distortion directions of the upper and lower piezoelectric element plate pairs f and f are opposite as shown in FIG. In addition, charges of the same polarity are generated at the electrodes that are in contact with each other, and the electrodes do not erase each other. Therefore, an output signal can be effectively extracted from the conductor c.

By the way, when the piezoelectric cable x is towed, an unnecessary signal called flow noise is generated due to cavitation or turbulence generated around the cable. In such a conventional configuration, each piezoelectric receiving unit b has a relatively small size. There is a drawback that the flow noise cannot be sufficiently suppressed because they are arranged at a large interval.

Next, a conventional configuration using a piezoelectric composite material will be described.

Ferroelectric ceramic particles such as lead zirconate titanate and lead titanate in 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. The mixed piezoelectric composite material has a characteristic whose acoustic impedance approximates the acoustic impedance of water. Therefore, when this is used as the piezoelectric cable x, the acoustic wave propagating in water is efficiently received and the sensitivity is improved. This has the advantage that it can be increased.

Therefore, as shown in FIG. 13, a piezoelectric layer h made of the piezoelectric material is arranged around an electrode core i, and a conductive material 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 i and the conductive material j to form a coaxial piezoelectric cable x in which the piezoelectric layer h is polarized in the radial direction. There is an apparatus which takes out an output signal from the apparatus and receives an acoustic wave propagating in the underwater.

In such a configuration, the area of the stretched part and the area of the contracted part are almost equal to each other with respect to the bending force, and charges having different polarities are generated in the respective domains, and they cancel each other. Then, since the area of the depression and the area of the bulge are different, generation of noise from this direction is observed. In addition, noise does not occur even with respect to the tensile force in the axial direction, because noise does not cancel each other.

<Problems to be Solved by the Invention> As described above, all of the conventional piezoelectric cables x cannot eliminate all of them under the action of various forces in water, and generate noise, High S / N ratio could not be obtained.

An object of the present invention is to provide a towing piezoelectric cable x capable of preventing influences other than acoustic waves and eliminating the disadvantages of the conventional configuration.

<Means for Solving the Problems> As shown in FIG. 1, the present invention provides a piezoelectric element layer 5a, 5b which is polarized in the thickness direction so that the polarization directions are arranged in one direction. By disposing on the front and back surfaces of the connecting plate 4, the inner electrodes 7 a and 6 b of the two piezoelectric element layers 5 a and 5 b are short-circuited to each other to form the wave receiving element 3. A large number of the wave receiving elements 3 are fixed via the buffer area 9 by the elastic flexible core 2, and a potential difference generated between the outer electrodes 6a and 7b of the piezoelectric element layers 5a and 5b can be taken out. A connection (8a, 8b) is made to each wave receiving element, which is covered with a flexible tube 1 and filled with an insulating oil 10 therein.

The piezoelectric element layers 5a and 5b can be formed of a piezoelectric composite material or a sintered piezoelectric ceramic material.

<Operation> The operation of the wave receiving element 3 in the above configuration will be described with reference to FIGS.

In each wave receiving element 3, as shown in FIG. 3A, the acoustic wave uniformly acts on the outer peripheral surfaces of the piezoelectric element layers 5a and 5b. Therefore, as shown in FIG. 3B, the sum of the voltages generated from the two piezoelectric element layers 5a and 5b is taken out from the lead wires 8a and 8b connected to the outer surface electrodes 6a and 7b. Become.

Next, the principle of noise cancellation in such a configuration is as follows.

Now, as shown in FIG. 4A, when a tensile force acts from the shaft core 2 in the axial direction, if the rigidity of the conductive connecting plate 4 is strong,
As shown in the dynamic model diagram of FIG. 4C, the piezoelectric element layer 5a on the left side in the figure is pressed by the conductive connecting plate 4 on the right inner surface by the inertial force, contracts in the thickness direction, and the piezoelectric element layer on the right side in the figure. 5b is
The left inner surface is pulled by the conductive connecting plate 4 and expands in the thickness direction. For this reason, the polarity of the charges generated in the piezoelectric element layers 5a and 5b is reversed, and as shown in FIG.
a and 7b have the same polarity and do not generate a potential difference. When the conductive connecting plate has flexibility, each of the piezoelectric element layers 5a and 5b bends following the conductive connecting plate due to inertia, but the piezoelectric element layer 5a disposed inside the bending is The voltage element layer 5b that contracts in the radial direction and extends outward in the curved direction expands in the radial direction, and the polarity of the generated charges is also reversed, so that no potential difference occurs between the outer electrodes 6a and 7b.

When acting in the direction perpendicular to the axial direction (upward in the figure) as shown in FIG. 5A, the piezoelectric element layers 5a and 5b are caused by inertial force as shown in the dynamic model diagram of FIG. The upper half portion in the figure contracts in the radial direction, and the lower half portion in the figure expands in the radial direction by pulling its inner surface. For this reason, since the generated charges have different polarities in the upper and lower portions, the piezoelectric element layers 5a and 5b themselves are short-circuited as shown in FIG.

Next, when a force in the bending direction is applied, as shown in FIG. 6, a buffer area 9 is provided between each of the wave receiving elements 3, so that even if it is relatively inclined, the dynamic range is increased. There is no effect, and no distortion is generated in each of the piezoelectric element layers 5a and 5b, and thus no noise is generated.

According to the present invention, even if the piezoelectric cable x is pulled or bent due to undulation, towing, or the like, it is canceled based on the noise cancellation principle, and no noise is generated. On the other hand, an output signal can be effectively generated for an acoustic wave.

<Embodiment> FIG. 7 shows a piezoelectric cable x according to an embodiment of the present invention.

A shaft core 2 is inserted into the inside of a flexible tube 1 which is an outer cover of the piezoelectric cable x, and an end of the shaft core 2 is connected to a winch z arranged at the stern of the ship y and towed. Is done.

The shaft core 2 has plate-like piezoelectric element layers 15a, 15b polarized in the thickness direction on the front and back surfaces of a conductive connecting plate 14 made of a metal plate.
The wave receiving element 3, which is adhered so that its polarization direction is the same, is inserted into the center of the conductive connecting plate 4 to fix the center, thereby concentrically. Many are held in a shape. The piezoelectric element layers 15a and 15b are made of a piezoelectric composite material, and are formed by punching the material.

A flexible annular cushioning member 19 such as foamed rubber is interposed between the above-described wave receiving elements 3, and is densely continuous in the axial direction.
The cushioning member 19 has a role of maintaining the interval between the wave receiving elements 3 while allowing the relative tilt of each wave receiving element 3, but excluding this, the gap between the wave receiving elements 3, 3 is eliminated. The buffer area may be constituted by the oil 10 itself.

Lead wires 8a and 8b are connected to the outer surface electrodes of the respective piezoelectric element layers 15a and 15b of the wave receiving element 3, and the output voltage generated in the piezoelectric element layers 15a and 15b is provided to a control circuit mounted on the ship y. To connect to.

Further, in the flexible tube 1, the lead wires 8a, 8b,
An insulating oil 10 such as silicon oil is filled so that each electrode of the piezoelectric element layers 15a and 15b does not short-circuit.

In the above configuration, when an acoustic wave propagates from the periphery of the flexible tube 1, as shown in FIG.
A signal voltage is generated on the piezoelectric element layers 15a, 15b of the lead wires 8a,
Removed from between 8b.

On the other hand, when a force is generated in the axial direction or in a direction perpendicular to the axial direction, the force is canceled by the previously described noise canceling principle, as shown in FIGS. When a bending stress acts, the shaft core 2 bends as described above with reference to FIG. 6, but the wave receiving element 3 fixed to the shaft core 2 Since the relative tilt can be freely adjusted by the contraction action, no distortion is generated and no electric charge is generated.
Furthermore, since a large number of piezoelectric element plates are continuously arranged at short intervals in the length direction, flow noise during towing can be sufficiently suppressed.

Thus, the piezoelectric cable x does not output from the lead wires 8a and 8b by various forces other than the acoustic wave.

FIG. 8 shows another embodiment of the wave receiving element 3, in which piezoelectric powder is contained in synthetic rubber on the front and back surfaces of a conductive connecting plate 24 made of a conductive composite material in which metal powder is dispersed in synthetic rubber. It is configured by forming piezoelectric element layers 25a and 25b made of dispersed piezo rubber.

To explain the manufacturing process of the wave receiving element 3, first, a conductive composite material constituting the conductive connecting plate 24 is formed in an annular shape (FIG. 9A). Next, on both surfaces of the conductive composite material, a material obtained by dissolving synthetic rubber and PT powder by toluene as a solvent is applied by a printing technique or the like, and the piezoelectric element layer 25a,
25b is formed (FIG. 9B). After semi-sulfurizing this,
A material obtained by mixing metal powder such as synthetic rubber and silver in toluene is applied to the surfaces of the piezoelectric element layers 25a and 25b, and the outer electrodes 26a and 27b are formed. (Fig. 9c).

Since each of the constituent elements has a base material of synthetic rubber, it can be simultaneously vulcanized as described above, so that it is integrally formed and does not require a bonding step. In such a configuration, the connecting plate 24 also serves as an inner surface side electrode of the piezoelectric element layers 25a and 25b.

Further, in such a configuration, one sheet provided with a material layer corresponding to each of the above-mentioned components is formed in advance by bristling, and this is punched to obtain a sheet having the shape shown in FIG. You may.

In the above embodiment, the conductive connecting plate 24, the piezoelectric element layer 25
The base materials of the electrodes a and 25b and the electrodes 26a and 27b can be changed from synthetic rubber to synthetic resin material. Also in this case, it is possible to integrally form by heat molding or the like.

<Effects of the Invention> As has been clarified by the above description, the present invention can remove as much as possible the effects of various forces due to ripples, towing, etc. Output of
There are excellent effects such as a significant improvement in the S / N ratio.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing a wave receiving element 3 of the present invention, FIG. 2 is a front view thereof, and FIGS. 3 to 6 are explanatory views showing the operation of the present invention. 5 and 6 are side views of the wave receiving element 3 showing the action of pressure, FIGS. 3 to 5 are equivalent circuit diagrams, FIGS. 4 to 5 are dynamic model diagrams, and FIGS.
FIG. 7 is a longitudinal sectional side view of a piezoelectric cable x of one embodiment, and FIG.
The figure is a longitudinal side view showing the configuration of another wave receiving element 3, and FIG. 9 is an explanatory view showing a step of forming the wave receiving element 3. It is.
FIG. 10 is a longitudinal sectional side view of a part of a piezoelectric cable x having a conventional configuration, FIGS. 11 and 12 are side views of a piezoelectric receiving unit b showing the action of pressure, and FIGS. 13B is an equivalent circuit diagram thereof, and FIG. 13 is a perspective view of a part of another conventional configuration. FIG. 14 is an explanatory view showing a usage mode of the piezoelectric cable x. 1; flexible tube, 2; shaft core, 3; wave receiving element, 4, 14, 24; conductive connecting plate, 5a, 5b, 15a, 15b, 25a, 25b; piezoelectric element layer, 6a, 7b,
26a, 27b; outer electrode, 6b, 7a; inner electrode, 9; buffer layer, 8
a, 8b; Lead wire, 10; Insulating oil, 19; Buffer material

Claims (5)

(57) [Claims] A piezoelectric element layer polarized in the thickness direction is disposed on the front and back surfaces of a conductive connecting plate such that the polarization directions are arranged in one direction, so that the inner surface side electrodes of both piezoelectric element layers are arranged. A wave receiving element is formed by short-circuiting each other, and a large number of the wave receiving elements are fixed via a buffer area by a non-stretchable flexible shaft passing through the center of the wave receiving element. A wiring for extracting a potential difference generated between electrodes on the outer surface of each of the wave receiving elements, covering the wave receiving elements with a flexible tube, and filling the inside thereof with an insulating oil; Piezo cable. 2. A wave receiving element is constituted by attaching a piezoelectric element plate polarized in the thickness direction to the front and back surfaces of a metal connecting plate so that the polarization direction is arranged in one direction. The piezoelectric cable for towing according to claim 1, wherein: 3. A wave receiving element is formed by arranging a piezoelectric element layer made of a piezoelectric composite material polarized in a thickness direction on the front and back surfaces of a conductive composite material so that the polarization direction is arranged in one direction. Claim 1 characterized by the above-mentioned structure.
Item 2. Piezoelectric cable for towing. 4. The piezoelectric composite material according to claim 1, wherein the piezoelectric composite material is composed of piezo rubber in which piezoelectric powder is dispersed in synthetic rubber, and the conductive composite material is composed of synthetic rubber in which metal powder is dispersed. 4. The piezoelectric cable for towing according to claim 3. 5. The piezoelectric composite material according to claim 1, wherein the piezoelectric powder is dispersed in a synthetic resin material, and the conductive composite material is composed by dispersing a metal powder in the synthetic resin material. 4. The piezoelectric cable for towing according to claim 3.