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JP2011244133

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DESCRIPTION JP2011244133
The present invention provides a compact acoustic transducer capable of low frequency acoustic
radiation. An acoustic transducer according to the present invention includes a flexural vibration
module (7) composed of at least one plate-like piezoelectric vibrator and at least one flexural
vibrator comprising a diaphragm, and a support member (9) for supporting the flexural vibration
module (7). And an end plate for closing both ends of the acoustic transducer. The plurality of
flexural vibration modules 7 are arranged in a cylindrical shape. The support members 9 radially
extend from the center of the flexural vibration modules 7 arranged in a cylindrical shape, and
are joined to the ends of the diaphragms of the adjacent flexural vibration modules 7, and a part
of the support members 9. A notch 20 is provided at the end of the frame. The end plate is
provided with an open hole 4 penetrating the end plate. The open hole 4 is connected to the
other open hole 4 via the sound generation unit 21 configured by the two adjacent support
members 9 and the flexural vibration module 7 and the notch 20. [Selected figure] Figure 2
Acoustic transducer
[0001]
The present invention relates to acoustic transducers, and more particularly to acoustic
transducers capable of acoustic radiation in water.
[0002]
When observing water, as in oceanographic surveys such as bottom crustal observation, sound
waves are used rather than light or radio waves.
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Light and radio waves are easily attenuated in water, and sound waves are very difficult to
attenuate even in water. Therefore, an acoustic transducer using a vibrator is used as a device for
generating a sound wave in water.
[0003]
There are various types of acoustic transducers. As an example of the related art, there is an
acoustic transducer using a hollow cylindrical piezoelectric vibrator (e.g., Non-Patent Document
1). Electrodes are provided on the inner and outer surfaces of the cylindrical piezoelectric
vibrator, polarization is performed in the thickness direction, that is, between the inner and outer
electrodes, and a voltage is applied between the inner and outer electrodes to radially or
inwardly of the cylindrical piezoelectric vibrator. A uniformly displaced respiratory oscillation is
excited. Sound is emitted to the liquid from the side of the cylindrical piezoelectric vibrator using
this respiratory vibration. In the case of the free flood structure, in addition to the sound being
emitted from the side, the sound is emitted from the inner surface of the hollow portion to the
liquid in the hollow portion, and the sound is further emitted to the outside using the water
column resonance of the liquid.
[0004]
Another example of the related art will be described. FIG. 14 is a schematic view of a free flood
type acoustic transducer in which a flexural vibration module is arranged in a cylindrical shape,
(a) is a schematic view of an appearance, and (b) is a schematic view of an AA ′ cross section.
An electrode 104 is disposed on the inner and outer surfaces of the plate-like piezoelectric
vibrator 102, and one surface of the electrode 104 and the vibrating plate 103 are joined to
constitute a flexural vibration module 101. In the acoustic transducer of this related art, a
bending vibration module 101 is disposed in a tubular shape, and adjacent bending vibration
modules 101 are joined (for example, Patent Document 1). The bending vibration module 101 is
provided with a waterproof structure 110. Each bending vibration module 101 repeatedly bends
back and forth in the thickness direction of the bending vibration module 101 to radiate sound to
the surrounding liquid, or the water column resonance of the liquid inside the cylindrical shape
surrounded by the bending vibration module 101 To emit sound using
[0005]
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Another example of the related art will be described. FIG. 15 is a schematic view of a barrel-stave
type acoustic transducer, (a) is a schematic view of an appearance, (b) is a schematic view of a
cross section of a flexural vibration module 101, and (c) is a schematic view of the inside. In
addition, although not shown in figure, in fact, all the outer surfaces are waterproofed.
[0006]
As shown in FIG. 15A, in the barrel-stave type acoustic transducer, a plurality of bending
vibration modules 101 are arranged in a cylindrical shape, and adjacent bending vibration
modules 101 are not joined but a gap 105 is provided. Both ends of 101 are fixed to the end
plate 106.
[0007]
As shown in FIG. 15B, in the flexural vibration module 101, electrodes 104 are provided on both
sides of the plate-like piezoelectric vibrator 102, and one surface is joined to the diaphragm 103.
Further, as shown in FIG. 15C, the end plate 106 is supported by the support column 107 so that
the distance between the end plates 106 does not change.
[0008]
Japanese Patent Application Laid-Open No. 2-238799
[0009]
Foundations and applications of ocean acoustics, edited by the Japan Society of Ocean Acoustics,
published by Naruyamado Bookstore, 2004, pp. 58-60
[0010]
For acoustic transducers that directly use the vibration of a hollow cylindrical piezoelectric
vibrator that is not free flood type (the end is not open), the efficiency of the acoustic radiation
from the cylindrical piezoelectric vibrator is the best for the cylinder When a resonant vibration
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occurs in which one wavelength of longitudinal vibration in the circumferential direction of the
piezoelectric transducer is matched with the length of the circumference.
In general, the speed of sound traveling through the material constituting the piezoelectric
vibrator is high, so for example, in a cylindrical shape with a diameter of about 10 cm, the
resonance frequency is as high as 5 to 10 kHz.
When the frequency is lowered, one wavelength becomes longer, so in order to perform efficient
acoustic radiation even at low frequencies, it is preferable to use a cylindrical piezoelectric
vibrator with a larger diameter. I will.
[0011]
In the barrel-stave type acoustic transducer as an example of the related art described above, the
resonance frequency can be lowered using bending vibration, but the gap between the bending
vibration modules 101 is restrained by a waterproof structure, or water pressure There are
problems such as suppression of bending vibration, etc., and it was actually difficult.
[0012]
In addition, in the free flood type acoustic transducer as an example of the above-mentioned
related art, it is intended to broaden the acoustic radiation by utilizing two types of resonances:
resonance frequency by respiratory vibration and resonance frequency of water column
resonance with low resonance frequency. ing.
However, the water column resonance frequency is determined by the total length of the acoustic
transducer, and in the case of an axial length of about 20 cm, the water column resonance
frequency is about 1 to 2 kHz. In order to further lower the frequency, the acoustic transducer
had to be made longer or a resonance tube (or an acoustic tube) had to be provided. Therefore, in
order to achieve low frequency acoustic emission, it is necessary to make the acoustic transducer
larger in diameter or length as the frequency decreases.
[0013]
An object of the present invention is to provide an acoustic transducer that solves the abovementioned problem that it is difficult to perform low frequency acoustic radiation without
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increasing the size.
[0014]
The acoustic transducer of the present invention includes a flexural vibration module composed
of at least one flexural vibrator comprising at least one plate-like piezoelectric vibrator and a
diaphragm, a support member for supporting the flexural vibration module, and both ends of the
acoustic transducer. An end plate for closing the part is provided.
The plurality of flexural vibration modules are arranged in a tubular shape. The support
members radially extend from the center of the cylindrically arranged flexural vibration modules,
are joined to the ends of the diaphragms of the adjacent flexural vibration modules, and at the
ends of some of the support members. Is provided with a notch. The end plate is provided with
an open hole penetrating the end plate. The open hole is connected to the other open hole via the
sound generating portion constituted by the two adjacent support members and the flexural
vibration module and the notch.
[0015]
According to the present invention, low frequency acoustic radiation can be provided without
increasing the size of the acoustic transducer.
[0016]
BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of one Embodiment of
the acoustic transducer which concerns on this invention, (a) is the schematic of an external
appearance, (b) is a schematic of the cross section of Y part of (a), (c) is of (a) It is the schematic
of the cross section perpendicular | vertical to an axial direction.
FIG. 2 is a perspective view of the acoustic transducer of FIG. 1; It is a figure which shows the
mode of displacement of the bending vibration module of the acoustic transducer of FIG. 1, (a) is
when applying the voltage which displaces outward, (b) is when applying the voltage which
displaces inward . It is a figure which shows the relationship of the frequency and transmission
voltage sensitivity in the water column resonance which arises with the free flood type | mold
acoustic transducer which the water column resonance which arises in the acoustic transducer of
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FIG. 1 and the related art completely opens. It is the schematic of the bending vibration body of
unimorph structure. It is the schematic of the bending vibration body of a bimorph structure. It is
the schematic of the bending vibration body of a unimorph structure which used the plateshaped piezoelectric vibrator laminated body. It is the schematic of the bending vibration body of
a bimorph structure which used the plate-shaped piezoelectric vibrator laminated body. It is a
figure which shows the relationship between the frequency of the bending vibration of an
acoustic transducer using the bending vibration module which stuck two diaphragms from which
thickness differs to a plate-like piezoelectric vibrator, and transmitting voltage sensitivity. It is a
schematic block diagram of the bending vibration module in other embodiment of the acoustic
transducer concerning this invention, (a) is a bending vibration module with a thick diaphragm,
(b) is a bending vibration module with a thin diaphragm. It is a figure which shows the
relationship between the frequency by the bending vibration, and the transmission voltage
sensitivity when using the acoustic transducer adjacent to a several bending vibration module
from which a resonant frequency differs. It is a figure which shows the relationship between the
frequency of the acoustic transducer of this embodiment, and transmitting voltage sensitivity. It
is a schematic block diagram of the bending vibration module in further another embodiment of
the acoustic transducer concerning this invention. It is the schematic of an example of the free
flood type | mold acoustic transducer which arrange | positions the bending vibration module of
related art in cylindrical shape, (a) is the schematic of an external appearance, (b) is the
schematic of AA 'cross section. BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic of an
example of the barrel stave type acoustic transducer of related art, (a) is the schematic of an
external appearance, (b) is the schematic of the cross section of a bending vibration module, (c) is
the schematic of an inside.
[0017]
Hereinafter, an embodiment of the present invention will be described based on the attached
drawings. In addition, the same number may be given to the structure which has the same
function in attached drawing, and the description may be abbreviate | omitted.
[0018]
FIG. 1 is a schematic configuration view of an embodiment of an acoustic transducer according to
the present invention, where (a) is a schematic view of an appearance, (b) is a schematic view of a
cross section of Y part of (a), (c) is It is the schematic of the cross section of the orthogonal |
vertical direction with respect to the axial direction of (a). In the acoustic transducer of the
present invention, the waterproof structure 5 is provided on the entire flexural vibration module
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7. However, in FIGS. 1A and 1C, a part or all of the waterproof structure 5 is omitted so that the
structure of the acoustic transducer can be easily understood.
[0019]
As shown in FIG. 1A, in the acoustic transducer of the present embodiment, a plurality of flexural
vibrators 1 are stacked in the axial direction to constitute one flexural vibration module 7, and a
plurality of flexural vibration modules 7 are formed. It is arrange | positioned so that it may
become cylindrical shape. The bending vibration module 7 may be configured by only one
bending vibration body 1. Further, although not shown in FIG. 1 (a), a buffer material 6 is
provided between the stacked flexural vibrators 1 (see FIG. 1 (b)). The shaft 8 is provided at the
center of the cylinder formed by the bending vibration module 7, and the support member 9 is
provided from the shaft 8 to a portion where the bending vibration modules 7 are adjacent to
each other (see FIG. 1C). . The supporting member 9 does not have to be integrally provided from
the upper end to the lower end of the entire axial direction of the flexural vibration module 7,
that is, from the upper end to the lower end of the portion where the side portions of the flexural
vibration module 7 are adjacent. It may be divided. In addition, a notch 20 is provided at an end
of a part of the support member 9.
[0020]
Further, end plates 14 having open holes 4 are provided at both ends of the acoustic transducer.
The open hole 4 penetrates the end plate 14 so that liquid can enter and exit from the acoustic
transducer through the open hole 4, that is, acoustic radiation is possible.
[0021]
As shown in FIG. 1 (b), the flexural vibrator 1 is configured by attaching a plate-like piezoelectric
vibrator 2 to one side of a diaphragm 3 made of metal, resin or the like (refer to unimorph
structure, FIG. 5). . Although not shown in FIG. 1, a plate-like piezoelectric vibrator 2 may be
attached to both sides of a diaphragm 3 made of metal, resin or the like (bimorph structure, see
FIG. 6). A bending vibration module 7 is formed by arranging two or more bending vibration
bodies 1 with each other via or directly via a cushioning material 6.
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[0022]
Here, the open hole 4 and the notch 20 of the present invention will be described. FIG. 2 shows a
perspective view of the acoustic transducer of FIG.
[0023]
As shown in FIG. 2, assuming that a triangular prism formed by the flexural vibration module 7
and the support member 9 is a sound generation unit 21, eight sound generation units 21 are
provided. Then, the eight sound generating units 21 are divided into two groups in such a
manner that four continuous sound generating units 21 form one set. First, one set will be
described. End plate 14 of one side of two sound generating units 21 which are located at both
ends of one set of sound generating units 21 and which are not sandwiched between the sound
generating units 21 in the set. The open hole 4 is provided in. Then, the support member 9 is
provided at the end of the support member 9 separating the sound generation unit 21 where the
open hole 4 is located and the sound generation unit 21 adjacent thereto opposite to the side
where the open hole 4 is located. The notch 20 is provided so as to be short in the longitudinal
direction. In addition, at the end of the side where the open hole 4 is located of the support
member 9 that partitions the sound generation units 21 where the open hole 4 is not located, the
notch is cut out so that the support member 9 is shortened in the longitudinal direction Provide
20. By doing this, since a zigzag folded structure in which the plurality of sound generating parts
21 communicate alternately at both ends can be formed, a long pipe can be formed from one
open hole 4 to the other open hole 4. . The other set is similarly provided with the opening 4 and
the notch 20, but the end plate 14 on the other side opposite to one set is provided with the
opening 4. By doing this, as in the above-described one set, a zigzag folded structure can be
formed, and a continuous long tube can be formed from one open hole 4 to the other open hole
4. A series of long tubes made by these can provide a water column resonance length greater
than that of the acoustic transducer.
[0024]
An example of the above-mentioned embodiment is a case where eight sound generation parts
21 (an acoustic transducer has eight angles), that is, an even number. In this case, it is preferable
to provide an even number of open holes 4 in each end plate.
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[0025]
When the sound generation unit 21 is an odd number (the number of angles of the sound
transducer is an odd number), one open hole 4 is provided in the end plate 14 on one side of one
sound generation unit 21. Then, the open hole 4 is formed in the end plate 14 on the other side
of the sound generation unit 21 of one of the sound generation units 21 adjacent to the sound
generation unit 21 in which the open hole 4 is provided in the end plate 14 on one side. Provide
one. Then, the support member 9 partitioning the sound generation units 21 in which the open
hole 4 is located is not provided with the notch portion 20, and communication from the one
open hole 4 to the other open hole 4 is continued As in the example of the above-described
embodiment, notches 20 are alternately provided at both ends of the plurality of support
members 9 so that a tube can be formed. By doing this, a zigzag folded structure in which a
plurality of sound generating parts 21 communicate alternately at both ends can be formed, and
a continuous long pipe can be formed from one open hole 4 to the other open hole 4. A water
column resonance length greater than that of the acoustic transducer can be obtained.
[0026]
As described above, when the sound generation unit 21 is an odd number, it is preferable to
provide one open hole 4 in each of the end plates 14 at both ends of the sound transducer.
[0027]
Next, the operation of the acoustic transducer of this embodiment will be described in detail.
The support member 9 provided from the shaft 8 toward the joint of the adjacent flexural
vibration modules 7 has a function of using the joint of the flexural vibration modules 7 as a
fulcrum of vibration. The bending vibration module 7 is bent by the voltage applied to the platelike piezoelectric vibrator 2. By connecting electrodes 10 (see FIG. 5) to be described later so that
the direction of voltage and the direction of bending are the same in all bending vibration
modules 7, the entire bending vibration modules 7 arranged in a cylindrical shape are displaced
outward. And push the liquid from the surface of the flexural vibration module 7 to the outside
(see FIG. 3A). On the other hand, when the direction of the applied voltage is reversed, the
flexural vibration module 7 is uniformly displaced inward, and the liquid flows from the outside
of the flexural vibration module 7 toward the flexural vibration module 7 (see FIG. 3B). . By
applying an alternating voltage to the plate-like piezoelectric vibrator 2, the displacement of the
flexural vibration module 7 is continuous, that is, vibration occurs, and acoustic radiation from
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the outer surface of the flexural vibration module 7 is performed.
[0028]
Further, the liquid flows into the pipe in which the plurality of sound generating parts 21 are
connected from one open hole 4 to the other open hole 4, and the pipe in which the sound
generating parts 21 are connected by the vibration of the bending vibration module 7. Water
column resonance occurs, which is the resonance of the liquid itself.
[0029]
In the acoustic transducer according to the present invention, since the acoustic generation unit
21 is connected from one open hole 4 to the other open hole 4, the acoustic transducer can be
used without increasing the size of the acoustic transducer or adding a resonance tube. Water
column resonance length much longer than the size can be obtained.
Therefore, as shown in FIG. 4, it is possible to obtain a water column resonance with a low
resonance frequency as compared with a free flood type in which both ends of the acoustic
transducer are open.
[0030]
Furthermore, by shifting and setting the resonant frequency of the flexural vibration of the
flexural vibration module 7 and the water column resonant frequency, the acoustic radiation
frequency band efficiently radiated can be broadened.
[0031]
Further, the length of the water column resonance can be made longer by increasing the number
of the sound generation units 21 of the sound transducer (increasing the number of angles of the
sound transducer).
[0032]
In addition, various structures are possible for the bending vibration body 1.
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The structure of the flexural vibrator 1 will be described in detail below.
[0033]
As a first embodiment of the flexural vibrator 1, an example of a unimorph structure in which the
plate-like piezoelectric vibrator 2 is attached to one side of the diaphragm 3 in FIG. 5 and the
electrodes 10 are provided on both sides of the plate-like piezoelectric vibrator 2 Indicates
From FIG. 5 to FIG. 8 described later, the front side in the drawing is the axial direction upper
side of the acoustic transducer, and the depth side in the drawing is the axial direction lower side
of the acoustic transducer.
[0034]
The plate-like piezoelectric vibrator 2 is polarized between the electrodes 10, that is, in the
thickness direction, and a voltage is applied between the electrodes 10 by the connection wire 11
so that the plate-like piezoelectric vibrator 2 expands and contracts in the width direction.
Vibrate in vibration mode (31 mode).
[0035]
As a second embodiment of the flexural vibrator 1, as shown in FIG. 6, a plate-like piezoelectric
vibrator 2 is attached to both sides of a diaphragm 3 and electrodes 10 are provided on both
sides of the plate-like piezoelectric vibrator 2 respectively. An example is shown.
Here, the plate-like piezoelectric vibrator 2 is polarized in the direction between the electrodes
10, and the direction is symmetrical about the diaphragm 3. In this case, one outer electrode is
connected to the other inner electrode, one inner electrode is connected to the other outer
electrode, and a voltage is applied between the connection wires 11. Further, although not shown
here, by making the polarization direction of the plate-like piezoelectric vibrator 2 asymmetrical
with respect to the diaphragm 3, the outer electrodes of the two plate-like piezoelectric vibrators
2 are connected, Further, the same effect can be obtained by connecting the inner electrodes and
applying a voltage between them by the connection line.
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[0036]
As a third embodiment of the flexural vibrator 1, a structure using a plate-like piezoelectric
vibrator laminate 2 'in which small piezoelectric vibrators are stacked as the plate-like
piezoelectric vibrator 2 is shown in FIG.
[0037]
The plate-like piezoelectric vibrator laminate 2 ′ has a structure in which the electrodes 10 are
provided on the bonding surfaces of small piezoelectric vibrators and arranged in parallel.
In this case, although it is not necessary when the diaphragm 3 is an insulator, in the case of a
conductor, although not shown, it is necessary to provide an insulating layer. Here, the
polarization direction is the direction between the electrodes 10, and the polarization directions
of the adjacent piezoelectric vibrators are alternately made to be opposite directions. The
connection of each electrode 10 is applied with voltage via two connection wires 11 alternately
connected alternately in accordance with the direction of polarization. The piezoelectric vibrator
of this embodiment vibrates in a longitudinal vibration mode (33 mode) in which the polarization
direction and the direction of the electric field generated between the electrodes 10 are the same
and the expansion and contraction direction is also the same.
[0038]
The structure described here is a unimorph structure using a plate-like piezoelectric vibrator
laminate 2 ′ as the plate-like piezoelectric vibrator 2 on one side of the vibration plate 3.
However, as shown in FIG. 8, even in the case of using the 33 mode, the bimorph structure can
be obtained as in the case of using the 31 mode. By causing the polarization direction of the
piezoelectric vibrator to be opposite to that of the piezoelectric vibrator at a position across the
diaphragm 3, the plate-like piezoelectric vibrator laminate 2 'on one side is displaced in the
reduction direction. The plate-like piezoelectric vibrator laminate 2 'on the other side tends to be
displaced in the extension direction. As a result, the flexural vibrator 1 is flexed and deformed.
Although not shown, the same effect can be obtained by making the direction of polarization the
same and reversing the connection direction of the electrodes 10.
[0039]
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Next, another embodiment of the acoustic transducer according to the present invention will be
described. The feature of the present embodiment is that by changing the resonance frequency of
the flexural vibration of the adjacent flexural vibration module 7, the acoustic radiation
frequency band that can be efficiently radiated can be further broadened.
[0040]
Temporarily, in the free flood type acoustic transducer (refer to FIG. 14) as an example of the
above-mentioned related art, two diaphragms 103 having different thicknesses are placed on the
plate-like piezoelectric vibrator 102 so as to sandwich the plate-like piezoelectric vibrator 102. It
is assumed that the resonance frequency of the bending vibration of each diaphragm 103 is
shifted. In this case, the position of the node apparently moves to the position of the center of
gravity of the flexural vibration module 101, coupling resonance is generated, and acoustic
radiation of different resonance frequencies can not be performed (see FIG. 9).
[0041]
FIG. 10 is a schematic configuration view of a flexural vibration module in another embodiment
of the acoustic transducer according to the present invention, in which (a) is a flexural vibration
module with a thick diaphragm, (b) is a flexural vibration module with a thin diaphragm. is there.
In addition, description is abbreviate | omitted about the structure similar to the abovementioned embodiment.
[0042]
In this embodiment, adjacent bending vibration modules 7 are made to have different resonance
frequencies due to bending vibration. Specifically, the diaphragm 3a having a large thickness is
used as one bending vibration module 7 of the adjacent bending vibration modules 7 (see FIG.
10A). Then, the thin diaphragm 3b is used for the other bending vibration module (see FIG. 10
(b)). By doing this, the resonant frequency becomes high in the flexural vibration module 7
having the thick diaphragm 3 a, and the resonant frequency becomes low in the flexural
vibration module 7 having the thin diaphragm 3.
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[0043]
In the acoustic transducer of the present embodiment, the flexural vibration modules 7 are not
joined together, but the flexural vibration modules 7 are fixed to the support member 9.
Therefore, since a portion fixed by the support member 9 becomes a node of vibration, coupled
resonance is not generated in the adjacent flexural vibration module 7. Therefore, the resonance
frequency of the bending vibration of each bending vibration module 7 can be set independently.
Moreover, it is also possible to utilize three or more types of resonance frequencies by changing
the thickness of the diaphragm 3 of the three or more flexural vibration modules 7 to three or
more types.
[0044]
As shown in FIG. 11, the resonance frequency in the bending vibration of the bending vibration
module 7 having the thin diaphragm 3b of one thickness is fr1, the antiresonance frequency is
fa1, and the bending vibration having the thick diaphragm 3a of the other thickness Assuming
that the resonance frequency in bending vibration of the module 7 is fr2 and the antiresonance
frequency is fa2, the resonance frequency fr2 in the vibration mode of the other bending
vibration module 7 is made to coincide with the antiresonance frequency fa2 of one bending
vibration module 7 A large drop in the transmission voltage sensitivity of the acoustic transducer
due to the anti-resonance of the flexural vibration module 7 can be significantly reduced (see FIG.
11).
[0045]
From the above, by utilizing the water column resonance and the bending resonance due to the
bending vibration of the bending vibration module 7 shifted in resonance frequency, as shown in
FIG. 12, an acoustic transducer having high transmission voltage sensitivity over a wide band is
obtained. You can get it.
[0046]
Thus, in the acoustic transducer of the present embodiment, the resonant frequency of the
flexural vibration of the flexural vibration module 7 can be changed by changing the thickness of
the flexural vibration module 7.
04-05-2019
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Therefore, although it is almost always necessary to design an acoustic transducer with limited
dimensions, in the acoustic transducer of the present invention, low frequency water column
resonance can be obtained without increasing the size, and bending vibration Since the resonant
frequency can be set widely, the degree of freedom in design can be increased.
[0047]
Next, still another embodiment of the acoustic transducer according to the present invention will
be described.
FIG. 13 shows a schematic configuration diagram of a flexural vibration module in still another
embodiment of the acoustic transducer according to the present invention. In addition,
description is abbreviate | omitted about the structure similar to the above-mentioned
embodiment.
[0048]
The bending vibration module 7 performs bending vibration with a junction with the support
member 9 as a node. However, since both ends of the flexural vibration module 7 are joined to
the end plate 14, the amplitude of the flexural vibration of the flexural vibration module 7 near
the end plate 14 is suppressed. Therefore, a diaphragm thin portion 3 'in which the thickness of
the diaphragm 3 of the flexural vibration module 7 is reduced in the vicinity of the end plate 14
is provided, or the thickness between the end plate 14 and the diaphragm 3 is greater than the
thickness of the diaphragm 3 Provide a thin cushioning material (not shown). By doing this, it is
possible to make it difficult to transmit the force that restrains the flexural vibration of the
flexural vibration module 7 caused by the end plate 14 to the diaphragm 3, and as a result, the
amplitude of the flexural vibration of the flexural vibration module 7 It can be kept large.
Further, by adopting this structure, it is possible to reduce bending vibration generated in the
bending vibration module 7 by using the joint point between the end plate 14 and the bending
vibration module 7 as a support point.
[0049]
A piezoelectric vibrator laminate in which piezoelectric vibrators are laminated from the shaft 8
04-05-2019
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toward the flexural vibration module 7 can be used as the support member 9 of the acoustic
transducer of the present invention. By applying a voltage to the flexural vibrator laminate, the
piezoelectric vibrator laminate expands and contracts simultaneously in the radial direction. By
transmitting the displacement due to the expansion and contraction to the flexural vibration
module 7, the flexural vibration module 7 can be vibrated to emit acoustic radiation to the
outside. In this case, by utilizing the vibration of the flexural vibration module 7 excited by the
expansion and contraction of the piezoelectric vibrator laminate together with the vibration of
the flexural vibration module 7 itself, the resonance of the resonance frequency and the water
column resonance by the flexural vibration of the flexural vibration module 7 Three resonance
frequencies can be used: frequency, and resonance frequency at which the piezoelectric vibrator
laminate uniformly vibrates the entire bending vibration module 7 in the radial direction. By
shifting the three resonance frequencies little by little and setting the phase relationship
appropriately, it is possible to emit a wider band of acoustic radiation.
[0050]
DESCRIPTION OF SYMBOLS 1 bending vibration body 2 plate-like piezoelectric vibrator 2 'platelike piezoelectric vibrator laminated body 3 diaphragm 3a thick diaphragm 3b thin diaphragm 3'
diaphragm thin part 4 open hole 5 waterproof structure 6 shock absorbing material 7 bending
vibration module 8 Shaft 9 support member 10 electrode 11 connection line 14 end plate 20
notch 21 acoustic generator
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