JP2794417B2 - Acoustic transducer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an acoustic transducer, and more particularly to an acoustic transducer such as an ultrasonic transducer using an annular vibrator.

(Prior art) Piezoelectric crystals using thickness vibration have been widely used as acoustic transducers for transmitting and receiving sound waves using seawater or the like as a propagation medium, but these have a sound wave frequency of around 40 KHz. However, there is a defect that the weight increases because the size becomes considerably large.

On the other hand, for the same purpose, an acoustic transducer using an annular vibrator is used as an ultrasonic transmitting / receiving element such as a hydrophone, but these are used, for example, inside and outside a barium titanate cylinder 1 as shown in FIG. Around the electrodes 2,
The outer periphery of the ring-shaped piezoelectric vibrator to which 2 is attached is covered with a rubber film, and in general, many are arranged and arranged in water.
In the example shown in FIG. 2B, the sound collected by an appropriate horn 4 is concentrated on the outer periphery of the ring-shaped vibrator 5 in the horn, and the azimuth at which the reception sensitivity is maximized is detected. It is available even if there is.

However, although the acoustic transducer using the annular vibrator as described above has the advantage of being lightweight because it is a thin crystal ring, it is omnidirectional in its radial direction, and it is necessary to provide directivity. If this is the case, as described above, it is necessary to devise a faced array or attach a horn, and the size is eventually increased.

(Object of the Invention) The present invention has been made in order to eliminate a defect of an acoustic transducer using a conventional ring-shaped vibrator as described above, and has a desired direction of the ring-shaped vibrator without increasing the size of the transducer. It is an object of the present invention to provide an acoustic transducer in which directivity is imparted to the sound transducer.

(Summary of the Invention) In order to achieve the above object, an acoustic transducer according to the present invention basically fills a part of an annular vibrator with a material having an acoustic impedance close to the acoustic impedance of a sound propagation medium so as to surround the part. In addition, the transmission and reception of the sound wave is substantially performed only at the relevant portion of the ring.

(Examples) Hereinafter, the present invention will be described in detail with reference to the results of experiments that led to the present invention and examples.

First, a commercially available barium titanate ring oscillator (resonance frequency
40KHz) is supported in the experimental apparatus shown in the figure showing the experimental results in FIG. 3, suspended and irradiated with 40KHz ultrasonic waves from a position about 100 mm away from the outer periphery thereof, and the periphery of the annular vibrator is radiated. The sensitivity characteristics were examined while changing the conditions of the medium.

As a result, when water is used as the propagation medium of the sound wave, the sensitivity is extremely poor, as expected, when the ring oscillator is completely submerged in water, and has a sensitivity peak when only a part of the ring oscillator is submerged. It has been found.

When the inner and outer peripheries of the ring oscillator are submerged, a very sharp peak is obtained when the inner and outer portions of the ring are submerged by 10% of the outer diameter. On the other hand, both sides of the ring are sealed with a waterproof thin film. 5-60% of the ring outer diameter when only the outer circumference is brought into contact with water
When the part was submerged, the maximum sensitivity was almost flat.

From the above experimental results, it is found that the inner and outer surfaces of the ring of the ring-shaped vibrator or the outer circumference of the ring are filled with a substance having an acoustic impedance close to the acoustic impedance of the sound propagation medium, and the ring-filled outer surface of the ring is filled with sound waves If so, a small and lightweight acoustic transducer having directivity on the surface side and high efficiency could be obtained.

1 (a), 1 (b) and 1 (c), 1 (d) are partially cutaway views showing different embodiments of the acoustic transducer according to the present invention, which are manufactured based on the above experimental results. is there.

That is, the ring-shaped piezoelectric vibrator 7 is housed in the housing 6 having one end open, and the right ends of the ring-shaped piezoelectric vibrator 7 are elastically fixed with the fixtures 9, 9,... Via the rubber blocks 8, 8,. The inner and outer circumferences corresponding to about 10% of the outer ring diameter of the ring-shaped piezoelectric vibrator 7
Filling the rubber 10 and exposing the flat surface of the silicon rubber 10 on the open surface of the housing (FIGS. 7A and 7B or rubber or plastic on both sides of the opening of the annular piezoelectric vibrator). A thin film 11 is adhered, and a silicone rubber 10 is attached to the outer peripheral portion of the ring corresponding to 5 to 60% of the ring outer diameter of the ring-shaped piezoelectric vibrator.
Is filled.

By doing so, it is possible to obtain an acoustic transducer suitable for transmitting and receiving sound using a material whose acoustic impedance is similar to that of silicon rubber, for example, water, a living body, or the like.

When using an acoustic transducer as described above, the exposed surface of the silicone rubber is pressed against the surface of a living body or the surface of a container filled with water. Needless to say, it is necessary to devise an appropriate oil film or the like in order to remove air that is significantly different from the above.

As described above, the present invention has been described with reference to the embodiment in which the sound wave propagation medium is water or a living body. However, the present invention is not limited to this, and the material to be filled around the annular vibrator depends on the sound wave propagation medium. It can be selected as appropriate, and the structure of the transducer may be modified as required according to the characteristics of each selected material.

Further, the annular vibrator to be used is not limited to the annular piezoelectric vibrator, and may be a magnetostrictive element in which a coil is formed around a nickel cylinder, for example.

(Effects of the Invention) Since the present invention is configured as described above, it has a remarkable effect in reducing the weight and sensitivity of microphones such as ultrasonic flaw detectors and ultrasonic diagnostic machines. In addition, it is effective in providing directivity to acoustic transducers such as hydrophones and sonars which have been widely used in the past, and in improving the sensitivity thereof.

[Brief description of the drawings]

FIGS. 1 (a), (b) and (c), (d) are partially cutaway views showing different embodiments of the acoustic transducer according to the present invention, respectively, and FIGS. 2 (a) and (b). 3) is a cross-sectional view showing the configuration of a conventional acoustic transducer using an annular vibrator, and FIG. 3 is a view showing the results of an experiment which led to the present invention. 5, 7: annular vibrator, 10: substance having an acoustic impedance close to the acoustic impedance of the sound wave propagation medium.

Claims (2)

(57) [Claims] 1. A part of the outer periphery of a ring constituting an annular vibrator is filled with a material having an acoustic impedance equal to or close to the acoustic impedance of a sound wave propagation medium, so that substantially only a part of the ring is substantially removed. An acoustic transducer characterized by transmitting and receiving acoustic energy through the acoustic transducer. 2. The acoustic transducer according to claim 1, wherein a portion of the inner and outer circumferences of said ring is filled with a material having an acoustic impedance equal to or close to the acoustic impedance of the sound wave propagation medium.