JPS6362160B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an underwater transducer using an organic piezoelectric material made of a flexible polymeric piezoelectric material or a composite of a polymeric piezoelectric material and a fine powder of a piezoelectric ceramic material.

Conventionally, this type of transducer has been proposed by the inventors of the present invention to be used underwater, which is advantageous because it eliminates sound reflections caused by acoustic impedance density mismatch, and is easy to manufacture, transport, and assemble, and is light in weight. In order to obtain a transducer, a structure has been proposed in which electrodes are provided on the inner and outer surfaces of a piezoelectric body, and both end surfaces or the entire outer surface are covered with an acoustically transparent insulating material. However, if you want to increase the length for the purpose of lowering electrical impedance, since these are linear in shape, the length is 1/1/1 of the sound wave.
There was a limitation in which the improvement in sensitivity slowed down from around 4 wavelengths. This is because the sound pressure distribution is sinusoidal, so the rise in sound pressure difference slows down from around 1/4 wavelength. In addition, the directivity of the sensitivity was determined by the linear shape, which had the disadvantage of having little freedom.

In the present invention, desired electrical impedance and directivity can be obtained by bending a long piezoelectric material within a range having an appropriate length component shorter than 1/2 wavelength.

That is, the present invention creates a two-dimensional structure by bending a flexible organic piezoelectric material in one plane that includes the axis of the transducer, or further bends it in another plane that includes the axis. It is characterized by having a three-dimensional structure.

Next, examples of the present invention will be described. FIG. 1 shows a first embodiment of the present invention, in which a piezoelectric body 1 is configured in a triangular shape with a length W in the direction of the axis 4 and a length 1 in the perpendicular direction. Here, 2 is an internal conductor, 2' is its output terminal, 3 is a surrounding conductor, 3' is its output terminal, and a broken line 5 indicates an insulator covering the piezoelectric body 1. Next, the principle will be explained with reference to FIG. Now consider the case where a plane wave arrives from the direction of arrow 6, the position in the propagation direction of the sound wave (direction of arrow 6) is the coordinate x, the sound pressure is the coordinate p, and the sound pressure distribution at a certain point is Suppose we are in the state shown in Figure 2B. Figure 2A
θ ₁ and θ ₂ are the angles formed between the directions of the sides 7-1 and 7-2 of the constant electric body 1 and the arrow 6. 1' and 1'' are 7-1
and the side length of 7-2, R is the radius from the center conductor to the surrounding conductor. Here, if the unit length is x ₄ −x ₁ , the difference in sound pressure between them is Δp, which is shown by vector 8. The sound pressure component applied in the end face direction of side 7-1 becomes vector 9, ie, vector 8×cosθ ₁ , and the sound pressure component applied in the radial direction of the piezoelectric body becomes vector 10, ie, vector 8×sinθ ₁ . In addition, the sound pressure applied in the radial direction is the sound pressure component obtained by multiplying the sound pressure p ₁ , p ₂ , p ₃ , p ₄ by cosθ ₁ , as illustrated at the positions x ₁ , x ₂ , x ₃ , and x ₄ . 13 are continuously distributed. If the g constant in the longitudinal direction of the piezoelectric body is g ₃₁ and the g constant in the radial direction is g ₃₃ , then the output voltage obtained between terminals 2' and 3' is vector 9 x g ₃₁ x 1', vector 10×g ₃₃
×R, vector 11×g ₃₁ ×1″, vector 12×
g ₃₃ ×R and vector 13 at each position on 1′, 1″
It is determined by a parallel circuit of five equivalent circuits having a power supply of ×R. However, the change in sound pressure distributed on 1′, 1″ is assumed to be a low frequency that can be approximated by a straight line.

As explained above, it can be seen that the larger the dimensions of 1', 1'' and R, the better.It is also understood that the sensitivity in a specific direction can be improved by changing the propagation direction of the sound wave and the bending direction of the piezoelectric material. Although the above description has been made regarding the case of bending in a triangular shape, it is clear that various shapes are possible.

FIG. 3 shows the second embodiment, which is bent in a sinusoidal manner in a vertical plane including the axis 4. The sensitivity in the axial direction is improved by increasing the length W in the axial direction, and the change in the directivity pattern is made monotonous by bending it in a sinusoidal manner.

Figure 4 shows the third embodiment, which has a structure in which the second embodiment is folded and doubled.The sensitivity and directivity are the same, but the electrical impedance is halved, and the amplifier circuit connected to this is halved. conditions are favorable.

Figure 5 shows the fourth embodiment, and while the second embodiment is bent in the vertical plane, this example is bent in the horizontal plane; It is something that While the second embodiment had high sensitivity in the vertical plane, this example has high sensitivity in the horizontal plane.

FIG. 6 shows the fifth embodiment, in which the second embodiment and the fourth embodiment are integrated by an integrated piezoelectric body, so that the sensitivity is increased in the vertical and horizontal planes. This is what I did.

The above description has been made using a coaxial piezoelectric body as an example, but it goes without saying that the same effect can be achieved by using piezoelectric bodies of other shapes, and a combination thereof may also be used. Figure 7 shows an example of this.
In this embodiment, the ribbon piezoelectric body is formed into a triangular shape as in the first embodiment.

Furthermore, although the explanation has been made for the case where the length is a frequency sufficiently lower than 1/2 wavelength, if it is longer than 1/2 wavelength, it will not be effective in improving sensitivity, but it will be effective in reducing electrical impedance. Further, although the description has been made using a wave receiver as an example, the same effect can be obtained using a wave transmitter.

As explained above, in the present invention, by bending a long flexible piezoelectric body, electrical impedance is low, favorable sensitivity, and desired directivity can be easily realized.

[Brief explanation of drawings]

1 and 3 to 7 are diagrams showing embodiments of the present invention, and FIG. 2 is a diagram illustrating the principle of the present invention. 1... Piezoelectric body, 2... Center conductor, 3... Surrounding conductor,
2', 3'...terminal, 4...center line indicating axis, 5...insulator, 6...sound wave propagation direction, 7-1, 7-2...side,
1', 1''...Side length, 8, 9, 10, 11, 12, 1
3...Sound pressure vector, R...Radius, P...Sound pressure, x...Position, _θ1 , _θ2 ...Angle between the direction of the sound wave and the side.

Claims (1)

[Claims] 1. An underwater transducer characterized in that a flexible linear organic piezoelectric material is bent at multiple points so that the length between the bending points is 1/2 wavelength or less.