JPH0258839B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides a flexible polymeric piezoelectric material or a composite piezoelectric material sheet (hereinafter both sheets are simply referred to as a piezoelectric sheet) consisting of a fine powder of a polymeric material and a piezoelectric ceramic material. This article relates to a transducer using a transducer.

Conventionally, piezoelectric ceramic or magnetostrictive vibrators have been used in this type of transducer, but the acoustic impedance density of these vibrators is often different from that of water, etc. It easily reflects received sound and is heavy. In addition, processes such as sintering, polishing, and cutting are required to form the desired shape, and even after forming, piezoelectric magnetic shapes with high brittleness may crack due to impact and become unusable. There were unavoidable drawbacks due to its physical properties. For example, the ratio of the acoustic impedance density of a piezoelectric ceramic vibrator to that of water is 15 or more, and when the above-mentioned pendulum is used as a wave receiver, the reflectance of sound intensity is over 80%.

The purpose of the present invention is to eliminate sound reflection caused by acoustic impedance density mismatch between water and other media by using a piezoelectric sheet as a transducer of a transducer, and also to eliminate sound reflection caused by acoustic impedance density mismatch between the transducer and a medium such as water. By forming the piezoelectric sheet, the work of cutting the piezoelectric sheet and attaching the terminal to the electrode can be minimized compared to the method of laminating multiple piezoelectric sheets, and by folding the piezoelectric sheet into an odd number of bellows shapes, It can prevent short circuits between electrodes even without an insulating layer, and is easier to manufacture, assemble, and transport than conventional products.
Another object of the present invention is to provide an advantageous transducer that can reduce its weight.

In order to achieve such an object, the transducer of the present invention has electrodes on both sides, and is formed by winding a piezoelectric sheet folded an odd number of times in a bellows shape, and the end surface or the entire outer surface of the piezoelectric sheet has electrodes on both sides. It is characterized by being watertightly covered with an insulating material having an acoustic impedance density close to the acoustic impedance density.

Next, embodiments of the present invention will be described with reference to the drawings. Note that the piezoelectric sheet is capable of converting not only sound to electricity but also electricity to sound, and has so-called reversibility; however, the case of conversion from sound to electricity will be explained below.

FIG. 1 is a diagram for explaining the molding state of the first embodiment of the present invention, and A shows the piezoelectric sheet 1 before molding, which has electrodes 3, 4 and electric terminals 3', 4'. B shows a state in which it is folded three times into a bellows shape as an example of an odd number of times. C is a perspective view of the product folded into a bellows shape and then molded into a cylindrical shape. As is clear from the figure, if the number of bellows-like folds is set to an odd number, it is possible to prevent the electrodes on both sides of the piezoelectric sheet 1 from shorting when formed into a cylindrical shape.

FIG. 2 is a diagram for explaining the molding state of the second and third embodiments of the present invention, and A is a diagram in which one side of the piezoelectric sheet 1 has been processed so that the rear end surface of the molding is concave. This is a diagram showing a case where A is folded. By winding this into a cylindrical shape, a concave transducer like C can be made. Similarly, process as shown in D,
By folding this like E and winding it into a cylindrical shape, a convex transducer like E can be made. Furthermore, by performing the processing shown in FIG. 2, A and D on opposite sides, it is also possible to make a transducer with concave and convex end faces.

Figure 3 shows an insulating material 2 having an acoustic impedance density close to the acoustic impedance density of the medium using the cylindrical piezoelectric sheet shown in Figure 1.
This is a structural diagram showing how the second and third parts shown in Figure 2 are covered watertightly so that no bubbles or air layers remain.
A similar watertight structure is adopted for the embodiment.

Next, the principle of operation will be explained using a first embodiment. Acoustic impedance density of piezoelectric sheet [1.6
×10 ⁵ to 2.3 × 10 ⁵ (gr/cm ² s)] is very close to that of water and insulating materials [1.5 × 10 ⁵ (gr/cm ² s)]. Therefore, incoming sound enters and passes through the piezoelectric sheet with almost no reflection, making it possible to accurately measure sound pressure without disturbing the surrounding sound field.

Although a structure in which the entire outer surface is in contact with water has been described above, a structure may be used in which a part of the structure is acoustically blocked in order to receive sound waves from a specific direction. Also,
The rolled piezoelectric sheet does not need to be a single piece, and pieces arranged in parallel with their end faces aligned may be electrically connected in series or parallel, and the diameters of the cylindrical piezoelectric sheets also need to be the same. Instead, it may be composed of a plurality of cylindrical piezoelectric sheets having different diameters, each having an increased or decreased number of turns.

As described above, the present invention involves folding a piezoelectric sheet into a bellows shape an odd number of times, cutting it into a desired length and shape, and
An insulating material made by cutting and processing a piezoelectric sheet that is rolled and formed or pre-rolled to the desired length and shape and has an acoustic impedance density close to that of the medium in which at least a portion of its entire outer surface is used. It can be easily manufactured by covering it watertight with water, and its structure allows it to withstand external water pressure, is lighter in weight than conventional transducers, and is a low-loss underwater transmitter/receiver with less sound reflection. A wave device is obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the molding state of the first embodiment of the present invention, A is a diagram showing the state of the piezoelectric sheet, B is a diagram when it is molded into a bellows shape, and C is a diagram showing the shape of the piezoelectric sheet.
2 is a diagram for explaining the molding state of another embodiment of the present invention, A and D are perspective views of the piezoelectric sheet, and B and E are views of the piezoelectric sheet folded. , C
and F are side views when these are molded into concave and convex cylindrical shapes, and FIG. 3 shows the first embodiment of the present invention after molding, in which the outer surface of the cylindrical piezoelectric sheet is made of an insulating material. FIG. 3 is a structural diagram showing how it is covered. 1... Piezoelectric sheet, 2... Exterior insulator, 3, 4
...Electrode, 3', 4'...Electric terminal.

Claims (1)

[Claims] 1 A sheet of polymeric piezoelectric material having electrodes on both sides and folded an odd number of times in the shape of a bellows is wound and formed, and at least part or all of its outer surface has an acoustic impedance density close to that of the medium used. A transducer characterized in that the transducer is watertightly covered with an insulating material.