JPH0311898

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DESCRIPTION JPH0311898
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to
transducers for use in sonars, and more particularly to small-sized improved transducers with
low frequency, high efficiency, and high water pressure resistance. Conventionally, as shown in
FIG. 4, in this type of transducer, the cylindrical piezoelectric material 10 is laminated as an
electromechanical transducer (hereinafter referred to as an exchange element), and the outer
surface or the inner and outer surfaces thereof are laminated. It had a structure in which the
insulating sheath 11 was provided. And especially, in order to obtain transmission sound
pressure high, the transmission frequency was set using the resonance by the respiration
vibration mode of the cylindrical piezoelectric material 10. FIG. In such a conventional
transducer, since the rigidity of the cylindrical piezoelectric material lO is high, the resonant
frequency tends to be high. When trying to lower the resonant frequency, there is a disadvantage
that the outer diameter is increased and the weight is also increased. In addition, when used at a
low frequency away from the resonance frequency, the power factor of the mechanical
impedance is deteriorated, and the conversion efficiency is lowered. As a result, high
transmission sound pressure can not be obtained. In order to obtain a low resonance frequency
while lowering the rigidity of the electromechanical transducer, as shown in FIG. 5, the
piezoelectric material 21 is attached to the diaphragm 20 to perform flexural vibration, and
sound is transmitted from the outer surface of the diaphragm 20. A transducer designed to do
this is known. In this transducer, the inner surface side of the diaphragm 20 is sealed by a
rattling case 22 in order to prevent the short-circuit phenomenon of the phase-reversed sound
wave. If the inner surface of the diaphragm 20 is an air chamber in order to prevent the short
circuit phenomenon completely, the rigidity of the diaphragm 20 is low, so that the water
pressure resistance can not be increased. The sound wave from the inner surface of the
diaphragm 20 is made by the rattling case 22 to make a sound. However, this sound wave has
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the disadvantage that the thickness of the sound case 22 is increased due to the low frequency,
and the sound wave can be a large and heavy transducer. An object of the present invention is to
provide a transducer which is low in frequency, high in efficiency, high in water resistance, small
in size and light in weight. The transducer according to the present invention is provided with a
plurality of slots y) in the axial direction at the central portion excluding both end portions of the
cylindrical body, and the member between these slits is a diaphragm. A piezoelectric material is
attached to at least one surface of the inner and outer surfaces of the diaphragm, and an
insulating sheath is provided on the inner and outer surfaces and the end surface. The axial
direction of one cylinder has a length of about half a wavelength to one wave. doing. The
structure according to the present invention obtains resonance of low frequency by utilizing
flexural vibration, and the sound itself is configured as a diaphragm in which the sound wave
emitted from the inner surface of the cylindrically arranged diaphragm is a partition 2 By
delaying the phase of the inside of the tube and propagating it to the outside, the short-circuit
phenomenon of the sound waves radiated from the inner and outer surfaces is prevented, and a
compact and lightweight transducer with high t @@ is realized.
Next, the present invention will be described with reference to the drawings. FIG. 1 is a
perspective view including a partial cross section of an embodiment of the present invention. In
the same figure, a plurality of slits 2 are provided in the axial direction at the central portion of a
cylindrical body 1 using an elastic material such as metal or synthetic resin. Then, a member
between the slits is referred to as a diaphragm 3. The diaphragm 3 is lowered in rigidity, and in
order to make it easy to attach the piezoelectric material 4, its cross section is shaped into a
rectangle. The piezoelectric material 4 is attached to the inside of the diaphragm 3 as shown in
FIG. The vibrating plate 3 and the piezoelectric member 4 are connected as shown in FIG. 2, for
example, as shown in FIG. 2 so that the vibration directions of the vibrating plates 3 by the
electric signal are aligned with each other. The portion of the slit 2 can be filled with a soft shock
absorbing material, such as cork, in order to make the inside an air chamber or to not affect the
resonance of the diaphragm. On the inner, outer, outer and end faces of the structure consisting
of the cylinder 1, the slit 2, the diaphragm 3 and the piezoelectric material 4, an insulating
sheath 5 is provided by mold or the like for protecting the structure from seawater. ing. When an
electrical signal of the same frequency as the flexural resonance of the diaphragm 3 to which the
piezoelectric material 4 is attached is applied from the lead wire 6, the piezoelectric material 4
expands and contracts in the axial direction by the piezoelectric effect. At this time, an expansion
/ contraction displacement in the axial direction occurs between the piezoelectric member 4 and
the diaphragm 3, and this becomes a driving force of the flexural resonance, both of which are in
the radial direction as shown by dotted or dotted lines in FIG. To vibrate. Due to this vibration,
sound waves of opposite phase are emitted to the inner and outer surfaces of the diaphragm 3.
Among the sound waves, the sound waves radiated to the inner surface propagate to the upper
and lower end surfaces without being transmitted through the diaphragm 3 because the side wall
of the acoustic tube (that is, the diaphragm 3) vibrates in the same phase. Due to the phase delay
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due to the propagation time, the sound wave emitted to the inner surface is adjusted to the same
phase as the sound wave emitted from the outer surface. As a result, the short circuit
phenomenon of the sound wave radiated from the inner and outer surfaces is efficiently
prevented. The width of the slit 2 may be such a dimension (about 0 ° -1 mm) that the
diaphragms 3 adjacent to each other do not contact at the time of flexural vibration. Can be The
axial length of the cylindrical body 1 is set to about half a wavelength to one wavelength.
According to the present invention, since the diaphragm and the piezoelectric member are made
to be in flexural resonance and the acoustic tube is constituted by the diaphragm, small and
lightweight transmission and reception with low frequency, high efficiency, and high water
resistance are realized. You can get a wave.
[0002]
Brief description of the drawings
[0003]
1 is a partially broken perspective view of an embodiment of a transducer according to the
present invention, FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1, FIG. The
figure which shows a piezoelectric material and FIG. 4 and FIG. 5 are perspective views which
show the conventional transmitter-receiver.
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