JPH0389797

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DESCRIPTION JPH0389797
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
tunable transducer, and more particularly to a tunable transducer which is used at its resonance
frequency in an underwater electroacoustic transducer and whose resonance frequency is
externally adjusted. [Background Art] Conventionally, as a transducer of this type, a mechanical
resonance transducer using a respiratory vibration mode of a cylindrical vibrator, or water X as
an external medium inside the cylindrical vibrator is used to There is a water column resonant
transducer which utilizes the resonance of a water column which flows in and is separated by a
cylindrical vibrator. As shown in FIG. 2 (a>), the machine resonance type transducer alternately
laminates the cylindrical vibrators 35a to 35c and the buffer members 34a to 34d, and supports
both ends by the lids 31a and 31b and the shaft 32, The inside of the transducer is covered with
a sheath as an air chamber. In the cylindrical vibrator, as shown in FIG. 2 (b), WThs 36a and 36b
are provided on the inner and outer surfaces of the cylindrical piezoelectric material 37, and the
resonance frequency fm by the respiratory vibration mode, ie, the acoustic velocity of the
piezoelectric material is C Then, when an average diameter is 2a and an electrical signal of a
frequency calculated by f m = c / 2πa is applied, mechanical resonance of the cylindrical
vibrator can obtain a highly efficient acoustic output. Further, as shown in FIGS. 3 (a) and 3 (b),
the water column resonant transducer has a structure in which the inner and outer surfaces and
the end face of the cylindrical vibrator 42 are covered with a sheath 40, and an external medium
flows into the cylindrical vibrator. In addition to the mechanical resonance frequency fm, such a
transducer has an acoustic resonance frequency fa due to the water column inside the cylindrical
oscillator. This water column resonance frequency fa is defined by the sound velocity of the
medium inside the cylindrical vibrator, the diameter of the inner circumferential surface of Co as
2 ai, the axial length of the inner circumferential surface as g, and the length as f with the
correction coefficient by the diameter ratio It is calculated by a = Co / 2 (ffl + 2αa i), and driving
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with an electrical signal of this frequency can produce an acoustic output with high efficiency as
well as mechanical resonance. [Problems to be Solved by the Invention] In the above-described
conventional mechanical resonant transducer, the resonant frequency is determined by the speed
of sound and the size of the piezoelectric material of the cylindrical vibrator, and the water
column resonant transducer has a cylindrical resonant frequency. Because the dimensions of the
transducer are determined by the dimensions of the vibrator, the transducer designed and
assembled can not adjust the resonance frequency later, and has a disadvantage that the efficient
frequency band is fixed near the resonance point. The object of the present invention is to
eliminate the above-mentioned drawbacks and to provide a tunable transducer in which the
resonant frequency can be adjusted externally. The tuned transducer according to the present
invention is formed by a plurality of cylindrical vibrators in which upper and lower ends are fixed
by alternately laminating layers inside a cylindrical closed vessel via a buffer material. In the
water column resonance transducer having an acoustic resonance frequency together with a
mechanical resonance frequency by the plurality of cylindrical vibrators by a water column
formed by filling water or seawater as a propagation medium of sound waves in the inner space
of the An expandable rubber tube which is disposed in an internal space formed by a cylindrical
vibrator and which encloses a liquid having a different speed of sound from the propagation
medium, and an amount of liquid sealed in the rubber tube in communication with the internal
space. Comprising a compensator for containing the propagation medium which becomes
excessive and a vibrator connected to the rubber tube to supply the liquid from the outside and a
valve for opening and closing the vibrator .
Next, the present invention will be described with reference to the drawings. FIG. 1 is a partial
cross-sectional perspective view (a>) and a longitudinal cross-sectional view (b) of an
embodiment of the present invention. In the tunable transducer according to this embodiment,
cylindrical vibrators 10a to 10d and buffer members 11a to 11c are alternately stacked, and
both ends are supported by support rings 5a and 5b through upper and lower lids la and lb. I
have C. An air chamber 2 is provided in the upper part of the inside, and a later described
condensator 9 is provided. A hollow rubber tube 14 is disposed inside the cylindrical vibrators
10a to 10d, as shown in FIG. 1 (b), and one end of the rubber tube 14 is opened inside the liquid
chamber 8 as an open end. It protrudes. The liquid 8 is connected to the outside by the vibrator
25. By opening and closing the valve 16, the liquid 8 can be sucked or discharged from the liquid
8, whereby the volume of the rubber tube 14 can be increased or decreased. In the transducer,
the adjustment of the volume increase and decrease of the medium 13 is performed by providing
a compensator. That is, when the liquid 15 is sucked into the liquid chamber 8 through the
vibrator 25, the volume of the rubber tube 14 increases, and the medium 13 corresponding to
the volume increase flows into the compensator 9. Conversely, when the liquid 15 is discharged
to the outside through the vibrator 25, the medium 13 is supplied from the compensator by the
reduction of the volume of the rubber tube 14. Thus, by providing the compensator, the volume
of the medium 13 filling the cylindrical vibrators 10a to 10d can be freely changed, so that the
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volume of the rubber tube 14 can be smoothly increased or decreased by adjustment from the
outside. . The liquid 15 inside the rubber tube 14 has a different sound velocity from that of the
medium 13, and the water column resonance frequency fa is arbitrarily changed by changing the
volume ratio of the medium 13 and the liquid 15. It can be done. In this embodiment, seawater
(sound velocity = 1500 m / s) as the medium 13 and silicon oil <sonic velocity 980 m / s 2 as the
liquid are used, and the water column resonance frequency is arbitrarily changed in the range of
Zl and 5 times. Can. As described above, it is possible to realize the transducer capable of
arbitrarily changing the water column resonance frequency by selecting the medium 13 and the
liquid 15 by increasing and decreasing the volume of the rubber tube 14. [Effects of the
Invention] As described above, according to the present invention, a tunable transducer capable
of adjusting the liquid column resonance frequency by providing a volume ratio adjusting
mechanism of liquid having a different sound velocity from that of the medium inside the
cylindrical vibrator. There is an effect that can be realized.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a partial cross-sectional perspective view (a) and a longitudinal cross-section (b) of an
embodiment of the present invention, and FIG. 2 is a longitudinal cross-sectional view (a) and a
vibrator perspective view (b) of a conventional mechanical resonant transducer. FIG. 3 is a
longitudinal sectional view (a) and a perspective view (b) of a conventional water column
resonant transducer.
1a, 1. b-cover, 2 ... air chamber, 3a, 3b screw, 4a, 4b, 4c, 4d-band, '5a 5b .. support ring, 6 ...
charging agent, 7 ... lead wire, 8 ・ ・ ・ Liquid chamber, 9 ・ ・ ・ Convensator, 10 a, 1. +1) b.
10c, 10d: cylindrical vibrator, 1.1a, Ilb. 11c: shock absorber, 12: sheath, 13: medium, 14: rubber
tube, 15: liquid, 16: valve, 30: key-pull, 31a, 31b ... Lid, 3; 2 ... Shaft, 33 ... Sheath, 34 a, 34 b, 34
c, 34 d-W tree, 35 a, 35 b, 35 C-cylindrical vibrator, 36 a, 36 b ... Electrode, 37: piezoelectric
material 40: sheath 41: cable 42: vibrator such as cylinder.
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