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JP2015027035

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JP2015027035
The present invention relates to a related ultrasonic transducer using a Langevin transducer,
which secures a usable frequency band without changing the configuration of an electrostrictive
transducer. An acoustic transducer (1) includes an electrostrictive vibrator (11) performing
expansion and contraction operations according to an electrical signal, a first metal plate (12)
and a second metal plate (13) sandwiching the electrostrictive vibrator, and a first metal There is
an acoustic radiation portion 15 disposed on the surface opposite to the surface holding the
electrostrictive vibrator of either the plate or the second metal plate, and a load load structure for
applying a compressive load to the electrostrictive vibrator. The load-loading structure has a
frequency characteristic determined by the configuration of the electrostrictive vibrator and a
characteristic value determined by a predetermined use frequency band. [Selected figure] Figure
1
Sound wave conversion device and sound wave conversion method
[0001]
The present invention relates to a sound wave conversion device and a sound wave conversion
method, and more particularly to a sound wave conversion device and a sound wave conversion
method for achieving high output in a wide band by applying a compressive load to an
electrostrictive transducer.
[0002]
In the underwater active sonar, a high-power ultrasonic transducer (ultrasonic transducer) is
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required to enable search for distant targets.
A Langevin transducer is widely used as such an ultrasonic transducer. FIG. 7 is a view showing
an ultrasonic transducer using a Langevin transducer. Referring to FIG. 7, the ultrasonic
transducer 100 includes an electrostrictive vibrator 101, a front mass 102, a rear mass 103, and
a bolt 104. The polarization direction (vertical direction in the drawing) of the electrostrictive
vibrator 101 is sandwiched by the front mass 102 and the rear mass 103 which are metal
members, and they are fastened by bolts 104 which are metal members. As a result, the axial
direction of the bolt 104 becomes the polarization direction of the electrostrictive vibrator 101,
and a compressive load is applied to the electrostrictive vibrator 101 in the polarization
direction. The electrostrictive vibrator 101 expands and contracts in the axial direction of the
bolt 104 in response to the input of the electrical signal. The energy from the expansion and
contraction is emitted to the water 106 through the front mass 102 and an acoustic emission
unit 105 made of rubber or the like in close contact with the front mass 102.
[0003]
The electrostrictive vibrator 101 is a material weak in the pulling direction, and when a large
electric signal is input, the stress generated by the expansion and contraction of the
electrostrictive vibrator 101 breaks the electrostrictive vibrator 101. Therefore, the ring-shaped
electrostrictive vibrator 101 is sandwiched by metal blocks, and the metal block and the
electrostrictive vibrator 101 are bolted. By adopting such a configuration, a load is applied to the
electrostrictive vibrator 101. This is called a bolted Langevin oscillator. The ultrasonic transducer
100 can prevent destruction of the electrostrictive vibrator 101 due to the input of a large
electric signal, and can output a large acoustic signal from the acoustic radiation unit 105 to the
water 106. However, in the ultrasonic transducer using a bolt-clamped Langevin transducer, a
high-power, narrow-band type ultrasonic transducer and a broadband type ultrasonic transducer
are used to output a high-power acoustic signal at a wide usage frequency. There is a problem
that it is difficult to reduce the size and weight because it is necessary to combine the two.
[0004]
In order to solve this problem, Patent Document 1 describes an ultrasonic transducer in which an
acoustic matching layer is connected to the acoustic signal radiation side of the front mass of a
Langevin transducer. The ultrasonic transducer of Patent Document 1 includes four piezoelectric
ceramic vibrators corresponding to the above-described electrostrictive vibrator 101, and a front
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mass of a metal material disposed on the front end surface of the frontmost piezoelectric ceramic
vibrator. And a rear mass of a metal material disposed on the rear end surface of the last row of
piezoelectric ceramic vibrators. Further, a bolt made of a metal material for connecting the
piezoelectric ceramic vibrator, the front mass and the rear mass by bolting, four electrodes, and
an acoustic matching layer on the acoustic emission surface of the front mass (Corresponding to
105)). The total length of the Langevin oscillator is set to a half wavelength of the fundamental
resonance frequency. Further, the acoustic matching layer has a specific acoustic impedance that
is intermediate between the material of the front mass and the water that is the ultrasonic
transmission material, and is set to one eighth the wavelength of the fundamental frequency of
the Langevin transducer. According to this configuration, it is possible to obtain high power
characteristics in a fundamental resonance frequency band of an acoustic signal radiated
(transmitted) into water by one ultrasonic transducer and wide band characteristics in the
vicinity of a double fundamental frequency.
[0005]
JP 10-178700 A
[0006]
However, a related ultrasonic transducer using a Langevin transducer as described in Patent
Document 1 adopts a structure in which a load is applied to a piezoelectric ceramic transducer,
and the configuration thereof is the center of the piezoelectric ceramic transducer. It consists of a
bolt passing through, a front mass and a rear mass made of metal.
A Langevin oscillator to which such a compressive load structure is applied has anti-resonance,
and there is a frequency band in which the performance of transmission voltage sensitivity of an
acoustic signal radiated into water is extremely reduced. FIG. 8 is a diagram showing an example
of transmission voltage sensitivity that represents the performance of the ultrasonic transducer
in water. The point shown as the frequency 107 in FIG. 8 is the frequency at which the
performance degradation occurs due to the structure of the load. Here, if the bolt is highly rigid
and its mass is large in the Langevin oscillator, the frequency 107 at which the transmission
voltage sensitivity decreases appears in the vicinity of the use frequency band, and the use band
is limited.
[0007]
In order to avoid this, it is necessary to change the configuration of the piezoelectric ceramic
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vibrator, and it has been difficult to secure a use frequency band according to the purpose of use.
[0008]
As described above, in the related ultrasonic transducer using the Langevin transducer, it is
difficult to secure the use frequency band without changing the configuration of the
electrostrictive transducer which is the piezoelectric ceramic transducer. was there.
[0009]
The object of the present invention is the above-mentioned problem. In a related ultrasonic
transducer using a Langevin transducer, it is difficult to secure a usable frequency band without
changing the configuration of the electrostrictive transducer. An object of the present invention
is to provide a sound wave conversion device and a sound wave conversion method that solve the
problem of the problem.
[0010]
In the sound wave conversion device according to the present invention, an electrostrictive
vibrator that performs expansion and contraction according to an electric signal, a first metal
plate and a second metal plate for holding the electrostrictive vibrator, the first metal plate, and
the first metal plate It has an acoustic radiation part which is arranged on the opposite side to
the side of the second metal plate on which the electrostrictive vibrator is sandwiched, and a load
load structure which applies a compressive load to the electrostrictive vibrator. The load-loading
structure has a frequency characteristic determined by the configuration of the electrostrictive
vibrator and a characteristic value determined by a predetermined use frequency band.
[0011]
Further, according to the sound wave conversion method of the present invention, a compressive
load is applied to the electrostrictive vibrator held between the first metal plate and the second
metal plate using a load-loading structure, which is determined by the configuration of the
electrostrictive vibrator. The characteristic value of the load-loading structure is controlled so as
to secure a predetermined use frequency band in frequency characteristics.
[0012]
According to the sound wave conversion device and the sound wave conversion method of the
present invention, it is possible to secure a use frequency band without changing the
configuration of the electrostrictive vibrator.
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[0013]
BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows the structure of the
sound wave conversion apparatus which concerns on the 1st Embodiment of this invention.
It is a sectional view showing the composition of the sound wave conversion device concerning a
2nd embodiment of the present invention.
It is a schematic diagram which shows the two-dimensional analysis model corresponding to the
2nd Embodiment of this invention.
It is a figure which shows the calculation result of the transmission voltage sensitivity
characteristic in the 2nd Embodiment of this invention.
It is sectional drawing which shows the structure of the wire junction part of the 3rd
Embodiment of this invention.
It is sectional drawing which shows the structure of the sound wave conversion apparatus of the
4th Embodiment of this invention.
It is a sectional view showing the composition of the related ultrasonic transducer. It is a figure
which shows the transmission voltage sensitivity characteristic of a related ultrasonic transducer.
It is a schematic diagram which shows the two-dimensional analysis model corresponding to the
related ultrasonic transducer.
[0014]
Hereinafter, embodiments of the present invention will be described in detail.
[0015]
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The sound wave conversion device according to the present invention is composed of an
electrostrictive vibrator, a first metal plate, a second metal plate, an acoustic radiation unit, and a
load carrying structure.
The electrostrictive vibrator is sandwiched between a front mass which is a flat first metal plate
and a second metal plate. An acoustic radiation unit is provided on the surface opposite to the
surface of the front mass that sandwiches the electrostrictive vibrator. Further, the load-loading
structure applies a compressive load to the electrostrictive vibrator via the first metal plate and
the second metal plate. By applying a compressive load to the electrostrictive vibrator having
frequency characteristics determined by the structure of the electrostrictive vibrator, it is
possible to secure frequency characteristics in a predetermined use frequency band. The specific
embodiment is described below.
[0016]
First Embodiment A first embodiment of the present invention will be described in detail with
reference to the drawings. FIG. 1 is a cross-sectional view showing the configuration of the sound
wave conversion device according to the first embodiment of the present invention, and is a view
cut along a plane including the central axis of the sound wave conversion device. The
configuration of the sound wave conversion device 1 according to the first embodiment of the
present invention will be described with reference to FIG.
[0017]
The sound wave conversion device 1 includes an electrostrictive vibrator 11, a front mass 12, an
acoustic radiation portion 15, a rear mass 13, a fastening portion 20, a screw portion 18, and a
wire 19. The electrostrictive vibrator 11 is sandwiched between a front mass 12 and a rear mass
13 which are a set of metal plates (flat plates made of metal members). Here, the rear mass 13 is
hollow. The polarization direction of the electrostrictive vibrator 11 is made to coincide with the
direction in which the front mass 12 and the rear mass 13 sandwich it. Thereby, periodic
stretching vibration is generated in the direction along the central axis of the sound wave
conversion device 1 along with the input of the periodic electric signal (for example, alternating
current signal) from the electrode (not shown) of the electrostrictive vibrator . A fastening
portion 20 (for example, a nut), which is a metal plate, is disposed on the surface of the rear mass
13 opposite to the contact surface with the electrostrictive vibrator 11. One or a plurality of high
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strength one or more wires 19 connected to a fixed part provided at the center of the front mass
12 by welding or hooks pass through the approximate center of the electrostrictive vibrator 11
and the rear mass 13 and a fastening part A screw portion 18 engaged with a female screw
formed at a central portion of 20 is fastened. Here, the front mass 12, the fixing portion provided
at the central portion thereof, the fastening portion 20, the screw portion 18 provided at the
central portion thereof, and the wire 19 constitute a load loading structure. The case where one
wire 19 is used will be described below. In addition, the rigidity of a load load structure can be
adjusted with the number of wires, and the ratio for which it accounts for the rigidity of the
sound wave conversion structure 1 whole can be controlled.
[0018]
The acoustic radiation unit 15 is disposed on the surface of the front mass 12 opposite to the
contact surface with the electrostrictive vibrator 11, and the acoustic radiation unit 15 is in
contact with the water 16. The mechanical stretching vibration generated in the electrostrictive
vibrator 11 is radiated from the acoustic radiation unit 15 to the water 16 through the front
mass 12. Without rotating the screw portion 18 around the fastening portion 20 with respect to
the sound wave conversion device 1 (specifically, the electrostrictive vibrator 11, the front mass
12, the rear mass 13 and the acoustic radiation portion 15), or The wire 19 is tensioned by
moving it in a direction away from the front mass 12 without twisting the wire 19. Thereby, a
compressive load is applied to the electrostrictive vibrator 11 sandwiched between the front
mass 12 and the rear mass 13 (or the fastening portion 20) in the direction along the central axis
of the sound wave conversion device 1 (hereinafter referred to as the central axis direction). It
takes As a result, mechanical energy converted from electric energy by the electrostrictive
element 11 is radiated to the water 16 through the front mass 12 and the acoustic radiation unit
15.
[0019]
The diameter of the wire 19 is sufficiently smaller than the inner diameter of the rear mass 13
and the electrostrictive vibrator 11. Further, the cross-sectional shape of the wire 19 is not
particularly limited. It may be circular, oval, polygonal or cylindrical.
[0020]
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The electrostrictive vibrator 11 may be cylindrical (ring-shaped). Specifically, the circumferential
shape of the cylinder may be a shape of a cylinder, or a shape of a rectangular cylinder which is a
polygon such as a triangle or a square. Furthermore, the rear mass 13 may also have the same
cylindrical shape as the electrostrictive vibrator 11. The outer peripheral shape of the fastening
portion 20 is the same as the outer peripheral shape of the electrostrictive vibrator 11 and the
rear mass 13. As a result, a compressive load can be applied uniformly in the central axis
direction of the electrostrictive vibrator 11 by the tension of the wire 19. The outer
circumferential surfaces of the rear mass 13 and the electrostrictive vibrator 11 and the outer
circumferential surface of the fastening portion 20 do not necessarily have to match. The outer
peripheral surface of the fastening portion 20 may protrude from the outer mass of the rear
mass 13 and the outer peripheral surface of the electrostrictive vibrator 11. Further, the size of
the screw hole of the screw portion 18 received in the fastening portion 20 is made smaller than
the inner diameter of the rear mass 13.
[0021]
The direction along the central axis of the sound wave conversion device 1 coincides with the
direction in which the front mass 12, the electrostrictive element 11, the rear mass 13, and the
fastening portion 20 are stacked.
[0022]
As described above, in the first embodiment of the present invention, the electrostrictive vibrator
11 sandwiched between the front mass 12 and the rear mass 13 (or the fastening portion 20) is
compressed by the wire 19 provided at the center of the sound wave conversion device 1 By
applying a load, it is possible to prevent the self-destruction caused by the expansion of the
electrostrictive vibrator itself.
Furthermore, it is possible to control the frequency at which the transmission voltage sensitivity
is reduced by the configuration of the load-loading structure. Therefore, the frequency band of
the transmission wave used by the sound wave conversion device 1 can be secured without
changing the configuration of the electrostrictive vibrator.
[0023]
Second Embodiment Subsequently, a second embodiment of the present invention will be
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described in detail. FIG. 2 is a cross-sectional view showing the configuration of a sound wave
conversion device according to a second embodiment of the present invention. Similar to FIG. 1,
FIG. 2 is a view cut along a plane including the central axis of the sound wave conversion device.
In the second embodiment, the electrostrictive vibrator of the first embodiment is divided into a
plurality of parts in the central axis direction, and an electrode is inserted between the divided
electrostrictive elements. The same components as in FIG. 1 are described with the same
reference numerals. The configuration of the sound wave conversion device 2 according to the
second embodiment of the present invention will be described with reference to FIG.
[0024]
In addition to the component parts of the sound wave conversion device 1 of the first
embodiment, the sound wave conversion device 2 is a ring-shaped electrostrictive element 22,
23, 24, 25 polarized in the central axis direction of the ring, and an electrode 32. 33, 34, 35, 36,
a collar 21 and a joint portion 17. A fixing portion 17 for fixing the wire 19 is provided in a
central region of the upper surface (surface facing the rear mass 13) of the front mass 12, and a
collar 21 is provided on the outside thereof. Electrostrictive elements 22 to 25 and electrodes 32
to 36 are alternately stacked on the upper surface of collar 21 (the surface facing rear mass 13).
The electrostrictive elements 22 to 25 are arranged such that adjacent electrostrictive elements
and polarization directions alternate. The rear mass 13 is disposed on the electrode 22 and the
fastening portion 20 is disposed thereon. Here, the front mass 12, the fixing portion 17, the
fastening portion 20, the screw portion 18, and the wire 19 constitute a load-loading structure.
[0025]
From the inside of the ring-like laminated structure 37 composed of the electrostrictive elements
22 to 25, the electrodes 32 to 36, the collar 21, and the rear mass 13, the wire 19 joined to the
fixing portion 17 by welding or hook is drawn. The tip end of the wire 19 opposite to the fixing
point of the fixing portion 17 is engaged with the screw portion 18. With the screw portion 18
fixed in the rotational direction, the fastening portion 20 is turned relative to the ring-shaped
laminated structure 37 so that the screw portion 18 moves in the central axial direction of the
sound wave conversion device 2 and in the direction away from the front mass 12. The screw
portion 18 is fixed in the rotational direction so as to prevent the wire 19 from being twisted as
the fastening portion 20 rotates. Since the wire 19 is joined to the joint 17 of the front mass 12,
the front mass 12 is also pulled by the wire 19 and tries to move to the rear mass 13 side, but a
ring is formed between the front mass 12 and the fastening portion 20 Since the laminated
structure 37 is present, movement of the front mass 12 in the central axis direction of the sound
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wave conversion device 2 is suppressed, and only the screw portion 18 moves in a direction
away from the front mass 12 along the central axis of the sound wave conversion device 2.
Therefore, tension is applied to the wire 19 in a direction approaching the front mass 12 along
the central axis of the sound wave conversion device 2, and conversely, a compressive load is
applied to the ring-like laminated structure 37 in the direction opposite to the tension.
[0026]
Further, on the surface of the front mass 12 opposite to the surface on which the ring-shaped
laminated structure 37 is installed, the acoustic radiation portion 15 made of rubber or the like is
bonded. The surface of the acoustic radiation portion 15 opposite to the surface bonded to the
front mass 12 is in contact with the water 16.
[0027]
The compressive load on the ring-shaped laminated structure 37 is set to a value larger than the
maximum generated stress generated in the electrostrictive element. Specifically, when the
maximum voltage that can be assumed for the electrostrictive elements 22 to 25 is input, the
total stress generated in the electrostrictive elements 22 to 25 by electromechanical conversion
is defined as the maximum generated stress, and from that value Set a large value as the
compression load.
[0028]
In addition, between each laminated structure of the ring-shaped laminated structure 37, it is
fixing with an adhesive agent. Further, at least a part of the electrodes 32 to 36 protrudes from
the outer peripheral surface of the electrostrictive elements 22 to 25. The projection is a terminal
for inputting an electric signal, and the electric wire is joined.
[0029]
Wires are connected so that the pair of electrodes 32, 33, 34 and the pair of electrodes 35, 36
have the same potential, respectively, and an AC electrical signal is input. Electro-mechanical
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conversion occurs in the electrostrictive elements 22 to 25 respectively, and the electrostrictive
oscillations 22 to 25 expand and contract in synchronization with each other. The energy due to
this expansion and contraction operation propagates through the front mass 12 and the acoustic
radiation unit 15 and is radiated as an acoustic signal into the water 16. Here, a desired acoustic
signal can be obtained by changing the frequency of the alternating current electrical signal and
the input voltage.
[0030]
The calculation result of performing the finite element method analysis as the two-dimensional
axisymmetric model shown in FIG. 3 is shown in FIG. 4 as the second embodiment shown in FIG.
In addition, calculation results of finite element analysis performed using the two-dimensional
axisymmetric model shown in FIG. 9 are also shown in FIG. 4 for the related ultrasonic
transducers. In FIG. 3, the same components as in FIG. 2 are denoted by the same reference
numerals. The electrodes 32 to 36 are omitted to simplify modeling in finite element analysis.
Further, in FIG. 9, as in the analysis model of FIG. 3, the collar 121 is disposed on the upper
surface (bolt 104 attachment surface) of the front mass 102, the electrostrictive elements 122 to
125 are stacked thereon, A rear mass 103 is stacked on the top surface of the substrate 122. The
head 108 of the bolt 104 is disposed on the upper surface of the rear mass 103.
[0031]
FIG. 4 shows the result of calculation of the voltage sensitivity of the transmission signal emitted
to the underwater 16 by the sound wave conversion device 2. The horizontal axis represents the
frequency of the transmission signal, and the vertical axis represents the transmission voltage
sensitivity. Furthermore, the solid line graph in the figure is the calculation result of the present
embodiment, and the dotted line graph in the figure is the calculation result for an ultrasonic
transducer that is a related Langevin transducer.
[0032]
In order to easily compare the calculation results of the ultrasonic transducer related to the
present embodiment, in the analysis models of FIGS. 3 and 9, the stacked electrostrictive
elements, the front mass, the rear mass, and the color both have the same dimensions. . Further,
in FIG. 3, the screw portion and the fastening portion are made of the same material, and in the
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analysis, they are regarded as an integrated fitting 28 in which the screw portion and the
fastening portion are integrated. Further, the head 108 of the bolt 104 of the related ultrasonic
transducer is set to have the same shape as the fitting 28 of the present embodiment.
Furthermore, the diameter of the wire 19 in FIG. 3 was set to be smaller than the diameter of the
bolt 104.
[0033]
From FIG. 4, the antiresonance point, which is a performance reduction point at which the
transmission voltage sensitivity of the ultrasonic transducer that is the related Langevin
transducer is extremely reduced, is the frequency 38, and the transmission voltage sensitivity of
this embodiment is extremely reduced. The performance degradation point is the frequency 39.
It can be seen that the frequency 39 is moved to a higher frequency side than the frequency 38.
Assuming that the use frequency of the sound wave conversion device is a region shown by the
bandwidth 40, the antiresonance point which is a performance reduction point of the sound
wave conversion device using the wire 19 is the high frequency outside the use band,
specifically, the upper limit of the use frequency band. It can be moved to the side. Since there is
no performance deterioration point that is an anti-resonance point in the use zone and in the
vicinity of the use zone, desired dimensions can be easily adjusted by adjusting the dimensions of
the components to be compressively loaded without changing the configuration of the
electrostrictive vibration element. Favorable frequency characteristics of transmission voltage
sensitivity in the used frequency band can be obtained.
[0034]
As described above, in the second embodiment of the present invention, as in the first
embodiment, it is possible to prevent the self-destruction accompanying the expansion of the
electrostrictive element itself. Moreover, the working frequency band of the transmission wave of
the sound wave conversion device 2 can be secured without changing the entire configuration of
the plurality of electrostrictive vibration elements and the configuration of each of the
electrostrictive vibrators. Specifically, by applying tension only in the direction of the central axis
to the thin wire 19 having low rigidity, unnecessary stress in the direction of the central axis
from the electrostrictive element 22 to 25 is suppressed, and the frequency at which
performance degrades It is possible to shift to a higher band side than the use frequency band.
[0035]
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Third Embodiment Next, the third embodiment of the present invention will be described in
detail. FIG. 5 is a cross-sectional view showing the configuration of the wire bonding portion of
the sound wave conversion device according to the third embodiment of the present invention.
The sound wave conversion device of the third embodiment has the same configuration as that of
the second embodiment. However, the configuration of the wire 19 is different. That is, in the
second embodiment, one wire 19 is disposed, but in the third embodiment, a plurality of wires 19
are disposed. FIG. 5 is a top view of the front mass 12 viewed from the rear mass 13 side, and the
black circles “●” described in the joint portion 17 indicate the wire 19.
[0036]
When two wires 19 are used, as shown in FIG. 5 (a), they are located at substantially the same
distance from the center 41 of the fixed portion 17 and at positions that are point symmetrical
(or two times symmetrical) with respect to the center 41. Join the wires 19 of the
[0037]
When three wires 19 are used, as shown in FIG. 5 (b), each wire 19 is located at substantially the
same distance from the center 41 of the joint 17 and at a position three times symmetrical with
respect to the center 41. Join.
Further, as shown in FIG. 5C, each wire has a substantially same distance from the center 41 of
the fixed portion 17 and a point symmetrical (or two-fold symmetry) with respect to the center
41 and each wire Join 19 together.
[0038]
When four wires 19 are used, as shown in FIG. 5 (d), each wire 19 is located at substantially the
same distance from the center 41 of the fixed portion 17 and at a position symmetrical to the
center 41 four times. Join. Further, as shown in FIG. 5E, each wire 19 is joined to the center 41
and a position which is approximately the same distance from the center 41 of the fixing portion
17 and which is three-fold symmetric with respect to the center 41.
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[0039]
Furthermore, when five wires 19 are used, as shown in FIG. 5 (f), each wire 19 is located at
substantially the same distance from the center 41 of the fixed portion 17 and five times
symmetrical with respect to the center 41. Join. Further, as shown in FIG. 5 (g), the respective
wires 19 are joined to the center 41 and a position which is substantially the same distance from
the center 41 of the fixing portion 17 and which is four-fold symmetric with respect to the center
41.
[0040]
Thus, the wires are arranged at equal intervals on the circumference of a predetermined distance
from the center 41. Moreover, when the number of wires is three or more, one of the wires is set
as the center 41, and the other wires are arranged at equal intervals on the circumference
described above. The plurality of wires preferably have the same material and the same diameter,
but is not limited thereto. If the compressive load from the electrostrictive elements 22 to 25 can
be uniformly applied, it is not necessary to match the material and diameter of each wire.
[0041]
Further, the plurality of wires 19 directed to the screw portion 18 extend and are joined to the
screw portion 18 while maintaining the relative positional relationship of the wires in the fixing
portion 17. That is, the relative positional relationship between the joints of the respective wires
joined to the joint 17 and the relative positional relationship between the joints of the respective
wires joined to the screw portion 18 coincide with each other. Moreover, when tension is applied
to the wire 19 by turning the fastening portion 20, the screw portion 18 is not rotated as in the
first and second embodiments. Thereby, even if the fastening portion 20 rotates, tension can be
applied while maintaining the relative positional relationship of the respective wires, and a
compressive load can be applied uniformly to the electrostrictive elements 22 to 25.
[0042]
As described above, in the third embodiment of the present invention, by setting a plurality of
wires, it is possible to apply an equal compressive load to the electrostrictive element while
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suppressing the tension of the wire per wire. Furthermore, by arranging a plurality of wires at
equal intervals around the center of the sound wave conversion device, rotation of the sound
wave conversion device against external force applied to the sound wave conversion device, in
particular, external force applied around the central axis. Can be prevented. Fourth Embodiment
Next, a fourth embodiment of the present invention will be described in detail. FIG. 6 is a crosssectional view showing the configuration of the sound wave conversion device according to the
fourth embodiment of the present invention. Similar to FIG. 2, FIG. 6 is a view cut along a plane
including the central axis of the acoustic transducer. In the fourth embodiment, as in the second
embodiment, the electrostrictive element is divided into a plurality of parts in the axial direction,
and an electrode is inserted between the divided electrostrictive elements. The same components
as those in FIG. 2 are denoted by the same reference numerals. The configuration of the sound
wave conversion device 3 according to the fourth embodiment of the present invention will be
described with reference to FIG. In addition, it demonstrates focusing on the structure different
from the sound wave conversion apparatus 2 of 2nd Embodiment.
[0043]
The sound wave conversion device 3 differs from the sound wave conversion device 2 of the
second embodiment in the projecting direction of the electrode. That is, the ring-shaped
electrodes 52 to 56 are provided with the terminals for joining the electric wires on the inside,
and they project inward of the respective electrodes. Wires are connected so that the pair of
electrodes 52, 53, 54 and the pair of electrodes 55, 56 have the same potential, and an AC
electrical signal is input.
[0044]
The fixing portion 50 of the wire 49 is provided in a region outside the collar 21 on the upper
surface of the front mass 12. The high strength wire 49 is joined to the fixing portion 50 using
welding or a hook or the like. The wire 49 may be a wire made of metal, but is not limited
thereto. It may be a thin flat plate (ribbon) metal plate.
[0045]
As in the second embodiment, the collar 21 is disposed on the upper surface of the front mass
12, and the electrostrictive elements 22 to 25 and the electrodes 52 to 55 are alternately stacked
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thereon. The polarization direction of the electrostrictive element is along the central axis
direction of the sound wave conversion device 3. Furthermore, the electrostrictive elements
adjacent to each other are arranged in such a direction that their polarization directions
alternate. The rear mass 13 is disposed on the electrode 52, and the tail plate 46 is disposed
thereon. Guides 47 for passing the wires 49 are respectively provided on an outer peripheral
region that is axially symmetric (two-fold symmetry) on the surface opposite to the contact
surface with the rear mass 13, that is, the upper surface of the tail plate 46. In addition, a
winding portion 51 serving as another fixing portion is provided in an outer peripheral area of
the fixing portion 50 of the front mass 12 that is axially symmetrical. The fixing portion 50, the
two guides 47, and the winding portion 51 are arranged to be substantially aligned with each
other when viewed from above the sound wave conversion device 3. The wire 49 joined to the
fixed portion 50 is wound by the winding portion 51 across the guide 47 of the tail plate 46. In
the present embodiment, the front mass 12, the wire 49, the tail plate 46, the fixing portion 50,
and the winding portion 51 are members constituting a compression load structure.
[0046]
The winding direction of the winding unit 51 substantially coincides with the direction along the
central axis of the sound wave conversion device 3. By winding the wire 49 by the winding unit
51, the ring-shaped laminated structure 57 configured of the electrostrictive elements 22 to 25,
the electrodes 52 to 56, the ring 21, the rear mass 13, and the tail plate 46 is It is pressed in the
direction toward the front mass 12 along the central axis, and a load in the compression
direction is applied. An adhesive is fixed to each component of the ring-shaped laminated
structure 57.
[0047]
The electric wire joined to the electrodes 52 to 56 is drawn out from the through hole 48
provided in the central portion of the tail plate 46.
[0048]
The compressive load on the ring-shaped laminated structure 57 is set to a value larger than the
maximum generated stress generated in the electrostrictive element.
Specifically, when the maximum voltage that can be assumed for the electrostrictive elements 22
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to 25 is input, the total stress generated in the electrostrictive elements 22 to 25 by
electromechanical conversion is defined as the maximum generated stress, and from that value
Set a large value as the compression load. The electrostrictive element has a property of being
fragile in the force in the pulling direction, so when a large voltage is input, the electrostrictive
element may be broken by the stress generated by the expansion and contraction of the
electrostrictive element itself. However, as in the other embodiments, breakage can be prevented
by applying a compressive load larger than the maximum generated stress to the electrostrictive
element in advance.
[0049]
When an alternating current electrical signal is input through the electric wires such that the set
of electrodes 52, 53, 54 and the set of electrodes 55, 56 have the same potential,
electromechanical conversion is performed in each of the electrostrictive elements 22 to 25. ,
And the electrostrictive elements 22 to 25 expand and contract. This expansion and contraction
operation propagates through the front mass 44 and the acoustic radiation unit 58 and is
emitted as an acoustic signal to the water 16.
[0050]
As described above, the desired acoustic signal can be obtained by changing the frequency and
voltage of the alternating current electrical signal. In addition, also by the configuration in which
the compressive load is applied by the wire 49 from the outside of the ring-like laminated
structure 57, the performance deterioration point of the transmission voltage sensitivity of the
sound wave conversion device 3 can be moved to the high frequency side of the use frequency
band. That is, without changing the configuration of the electrostrictive vibrator, the frequency
characteristics of the transmission voltage sensitivity in the working frequency band are secured
by adjusting the dimensions of each member even in the compression load configuration where
the wire straddles the ring-shaped laminated structure. It becomes possible.
[0051]
In addition, in 4th Embodiment, although the wire 49 is made into 1 wire and the compressive
load is applied to the ring-like laminated structure 57, it does not restrict to this. For example, the
ring-shaped laminated structure 57 may be compressively weighted by a plurality of wires. In
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this case, joints and joints for joining the respective wires are provided on the outer periphery of
the front mass 12 at axially symmetrical (2-fold symmetry) positions. Also, two guides are
provided on the outer periphery of the upper surface of the tail plate 46 at axially symmetrical
positions. A fixing part, a winding part, and two guides are prepared for each wire, and their
arrangement is arranged in a straight line when viewed from above the sound wave conversion
device 3.
[0052]
In the third embodiment, the plurality of wires 19 are disposed along the central axis direction,
but the present invention is not limited thereto. The wire 19 may be inclined to the central axis
from the front mass 12 toward the front mass 13. However, when there is a wire passing through
the central axis, the wire is not inclined. The inclination direction of each wire to be inclined can
be made to spread radially around the central axis, and the inclination angle can be made the
same degree with respect to the central axis.
[0053]
The present invention is not limited to the above embodiment, and various modifications are
possible within the scope of the invention described in the claims, and they are also included in
the scope of the present invention. Needless to say.
[0054]
1, 2, 3 sound wave conversion device 11, 101 electrostrictive vibrator 12, 102 front mass 13,
103 rear mass 15, 105 acoustic radiation part 16, 106 underwater 17, 50 fixing part 18 screw
part 19, 49 wire 20 fastening part 22 , 23, 24, 25 electrostrictive element 21, 121 collar 32, 33,
34, 35, 36, 52, 53, 54, 55, 56 electrode 37, 57 ring-shaped laminated structure 38, 39, 107
frequency 40 bandwidth 41 Center 46 Tail plate 48 Through hole 47 Guide 51 Winding portion
100 Ultrasonic transducer 104 bolt
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