JPS6239879B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a low frequency transducer using a polymeric piezoelectric material.

Conventionally, low-frequency transducers have often used composite oscillators made of ceramic and metal masses with a cross-sectional area larger than the ceramic's cross-sectional area bonded to both sides, or by bolting the two masses together. There is.
The reason for this is to avoid increasing the size of the vibrator when attempting to lower the resonant frequency of the vibrator. In other words, if the vibration principle is expressed as a lumped constant, the resonance frequency ₀ is the equivalent mass of the vibrator.
If m is the equivalent stiffness and s is the equivalent stiffness, it is given by ₀ = 1/2π √, so the purpose was to reduce the stiffness of the ceramic part and attach large masses at both ends to make it smaller. However, due to the difficulty of manufacturing and assembling parts, there was a limit to miniaturization, which could be reduced to 1/5.

The present invention provides a small transducer by using a polymer piezoelectric material whose stiffness is 1/20 or less that of ceramic, and by proposing a structure in which the clamping structure between the masses has a stiffness commensurate with this. It is.

A feature of the present invention is a structure in which pressure is applied from the outside to a composite vibrator in which masses are attached to both ends or around the polymer piezoelectric material by rubber, resin, or liquid filled in the case.

Next, an embodiment of the present invention will be explained in comparison with a conventional one.

FIG. 1 is a sectional view showing a conventional transducer of this type. 1 is a cylindrical ceramic vibrator (hereinafter referred to as ceramic) 1-1 and 1-2 are electrodes, 2 is a mass, 3 is a tightening bolt for tightening both masses to the vibrator, 4 is an electric terminal, and 5 is a case. The reason why the ceramic wall thickness is made thin is as described above. The tightening bolt 3 is used to apply precompression to prevent the bond between the ceramics and between the ceramic and the mass from peeling off due to vibration displacement. Therefore, when vibrating, the bolt also vibrates along with the ceramic.

Next, the first embodiment of the present invention will be described with reference to the cross-sectional view shown in FIG. 2. 6 is a polymer piezoelectric material;
7 is the inner case, 8 is the rubber, 9 is the rubber holding frame,
10 is a screw, 11 is an external case made of a material such as FRP and has good acoustic transparency, 12 is air inside the internal case, and 13 is a liquid such as oil (or water). In such a structure, if the resonance frequency is ₀ , the stiffness (Young's modulus) of the polymer piezoelectric material is
is approximately 3×10 ¹⁰ dyne/cm ² , which is less than 1/20 of the stiffness of ceramic, which is approximately 65×10 ¹⁰ dyne/cm ² . Therefore, since ₀ is proportional to the square root of stiffness, considering the conventional external dimensions, it is almost 1/
It becomes 5. In other words, in order to obtain the predetermined value of ₀ , it is sufficient to use approximately 1/5 of the size.

Next, to explain the structure for preventing peeling during vibration of the connection between the polymer piezoelectric material 6 and between the polymer piezoelectric material 6 and the mass 2, rubber 8 is applied to the radiation surfaces of both mass, covered with the inner case 7, and then The outside is covered with an external case 11 filled with liquid 13. External case 11 and liquid 1
3 has a low stiffness unlike conventional tightening bolts, so it has little effect of increasing _{the 0} of the vibrator.

Next, the third embodiment showing a plan view of the second embodiment of the present invention.
To explain with reference to the drawings, a diagonally shaded sheet 6 is a polymeric piezoelectric sheet having electrodes 6-1 and 6-2 on both sides, and is spirally wound around a cylindrical core 14. At this time, an insulating film 16 is sandwiched between each layer to avoid short-circuiting of both electrodes. Glue a fan-shaped mass 2 on the outside in a cylindrical shape,
Furthermore, a rubber cylinder 15 having a small inner diameter is expanded and placed on the outside thereof. In this case, the force of tightening the mass 2 to the polymeric piezoelectric body 6 uses the contractile force of the rubber 15, and since the stiffness of the rubber is small, it does not have an effect of increasing the resonance frequency. With such a structure, a low-frequency resonant transmitter that expands and contracts uniformly in the radial direction can be obtained.

As explained above, the present invention has the advantage that a compact low-frequency transducer can be obtained by configuring the polymer piezoelectric material and the mass to be tightened with rubber or the like.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an example of a conventional transducer, Fig. 2 is a sectional view showing a first embodiment of the present invention, and Fig. 3 is a sectional view showing an example of a conventional transducer.
The figure is a plan view showing a second embodiment of the present invention. 1...ceramic oscillator, 2...mass, 3...
Tightening bolt, 4...terminal, 5...case, 6...
...Polymer piezoelectric material, 6-1, 6-2... Electrode, 7...
...Inner case, 8, 15...Rubber, 9...Retainer frame, 10...Screw, 11...Outer case, 12...
...Air, 13...Liquid, 14...Cylindrical core, 16
...Insulating film.

Claims (1)

[Claims] 1. A transducer characterized in that a composite vibrator made of a polymeric piezoelectric material and a mass is covered with a case filled with compressive rubber, resin, or liquid.