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DESCRIPTION JPH03140097

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DESCRIPTION JPH03140097
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
underwater acoustic wave transmitter for generating a sound wave in water, which is used for
ranging in water using pulse sound. (Prior Art) Conventionally, there have been techniques as
shown in FIGS. 2 and 3 as techniques in such a field. The configuration will be described below
with reference to the drawings. FIG. 2 is a schematic block diagram of a conventional disk type
underwater acoustic wave transmitter. This disk type underwater acoustic wave transmitter is
used in a high frequency region, and has a thin disk-like piezoelectric vibrator 1 for vibrating at
high frequency, and electrodes on the upper and lower surfaces of the piezoelectric vibrator 1
And 2.3 are deposited, and the terminals 4 and 5 are connected to the electrodes 2 and 3
respectively. The piezoelectric vibrator 1 and the electrode 2.3 are coated with a rubber mode
material or the like (not shown). In this underwater acoustic wave transmitter, when a voltage is
applied to the terminals 4 and 5, it vibrates in the voltage application direction, that is, the
thickness direction of the piezoelectric vibrator 1. In particular, when the piezoelectric vibrator 1
is driven at the fundamental resonance frequency in the thickness direction, the vibration
displacement of the transmitting wave front 6 is maximized, so that it is used at a fundamental
resonance frequency. That is, this underwater acoustic wave transmitter transmits a sound wave
from the wave transmission surface 6 by utilizing the resonance (longitudinal vibration) in the
thickness direction of the piezoelectric vibrator 1 due to the piezoelectric phenomenon of the
piezoelectric vibrator 1. FIG. 3 is a schematic block diagram of another conventional disk type
underwater acoustic wave transmitter. In this disk type underwater acoustic wave transmitter,
the piezoelectric vibrator 1 is finely divided (diced), and the electrodes 2 respectively attached to
the divided piezoelectric vibrators 1 are mutually connected by the lead wires 7. It is connected.
In this underwater acoustic wave transmitter, when a voltage is applied to the electrodes 4 and 5,
the divided individual piezoelectric vibrators 1 expand in the thickness direction and vibrate, that
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is, piston movement. Can be oscillated in phase with the same amplitude. (Section M that the
Invention is to Solve) However, the underwater acoustic wave transmitter of the above
configuration has the following problems. (1) As shown in FIG. 2, in the conventional underwater
acoustic wave transmitter, the wave transmission wave 6 is generated using the thickness
vibration of the thin disk-like piezoelectric vibrator 1 mainly used in the high frequency range
Because the piezoelectric vibrator 1 is thin even if resonance in the thickness direction is used,
the amplitude of the transmission surface 6 can not be large, and the power is small. In order to
eliminate the power shortage, the diameter of the piezoelectric vibrator 1 may be increased.
However, when the diameter of the piezoelectric vibrator 1 is increased, the displacement in the
thickness direction has a distribution on the wave transmission surface 6 (referred to as spurious
displacement distribution), so that the thickness resonance mode, that is, the displacement of the
wave transmission surface 6 is in phase There is a problem that the following piston vibration
mode can not be realized faithfully.
(2) As a measure for removing the spurious displacement of the piezoelectric vibrator 1, as
shown in FIG. 3, an underwater acoustic wave transmitter in which the piezoelectric vibrator 1 is
diced is proposed. In this underwater acoustic wave transmitter, it is possible to vibrate the wave
front 6 of each of the diced piezoelectric vibrators 1 in phase and with the same amplitude.
However, the strength is weak such as a part of the diced part is missing, and there is a
manufacturing complexity such that the individual diced piezoelectric vibrators 1 have to be
connected by the lead wires 7. In addition, it is difficult to obtain good transmission performance
because the lead wire 7 is cut or the like. In the underwater acoustic wave transmitter using
thickness resonance, the present invention has the problem that the amplitude of the wave
transmission surface can not be largely reduced when the thickness of the piezoelectric vibrator
is thin, and the wave transmission surface An underwater acoustic wave transmitter that solves
the problem of weakening strength when dicing, complexity of connecting work to connect
individual piezoelectric vibrators that have been diced, and deterioration of transmission
performance due to cutting of the lead wire To provide (Means for Solving the Problems) In
order to solve the above-mentioned problems, the present invention replaces the underwater
acoustic wave transmitter utilizing the thickness resonance of the piezoelectric vibrator as in the
prior art, and applies the voltage in the radial direction. The elastic member is a disk-shaped
piezoelectric vibrator that performs spreading vibration, an annular elastic body mounted on the
outer periphery of the piezoelectric vibrator and having a substantially triangular radial cross
section, and the elasticity in a state in which the inside communicates with the outside through
an orifice. An annular shear spring having a function of supporting the periphery of the body and
converting the displacement in a direction perpendicular to the radial direction, and an annular
rigid body supporting the periphery of the shear spring with a molding material It covers and
comprises an underwater acoustic wave transmission machine. (Operation) According to the
present invention, since the underwater acoustic wave transmitter is configured as described
above, the piezoelectric vibrator expands and vibrates in its radial direction by voltage
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application. The elastic body, the shear spring, and the rigid body support the periphery of the
piezoelectric vibrator, and function to convert the radial spreading vibration in a direction
perpendicular to the transmission wave surface to transmit an acoustic wave. As described above,
it is possible to cause the planar transmitting wavefront to be oscillated in a piston efficiently by
utilizing the radial spread vibration. Therefore, the problem can be solved. 1 (a) and 1 (b) are
block diagrams of an underwater acoustic wave transmitter according to an embodiment of the
present invention, wherein FIG. 1 (a> is a plan view and FIG. 1 (b) is a plan view. It is the sectional
view on the AA line of the figure (a). This underwater acoustic wave transmitter has a diskshaped piezoelectric vibrator 10 that vibrates in the radial direction by applying a voltage, and
on the upper and lower surfaces of the piezoelectric vibrator 11 is an electrode 11.12 made of a
conductive film. Terminals 13.14 are respectively connected to the electrodes 11.12.
An annular elastic body 15 having a triangular cross section in the radial direction is mounted on
the outer periphery of the piezoelectric vibrator 11, and the peripheral edge of the elastic body
15 is further supported by an annular shear spring 16. The shear spring 16 has a hollow
rectangular shape in radial cross section and has a function to resist a shear force, and the cavity
17 inside the shear spring 16 has an outer surface of the transmitter via the orifice 18. The
medium (water) is filled. The peripheral edge of the shear spring 16 is supported by an annular
rigid body 19. The entire transmitter is covered with a mold material 20 such as urethane rubber
having good sound permeability, and the orifice 18 formed in the mold material 20 and the rigid
body 19 is in communication with the cavity 17 . In addition, the code | symbol 21 in FIG. 1 is a
wave transmission surface which generate | occur | produces a sound wave. Next, the operation
will be described. When a voltage is applied to the terminals 13.14, the piezoelectric vibrator 10
radially expands and contracts. When the piezoelectric vibrator 10 extends in the radial
direction, the annular elastic body 15 provided on the outer peripheral surface of the
piezoelectric vibrator 10 extends in the circumferential direction of the circular ring based on the
extension of the piezoelectric vibrator 10 and is deformed. As a result, radially extending
axisymmetric deformation occurs. Thereby, the elastic body 15 presses the outer ring-shaped
shear spring 16. Since the shear spring 16 is supported on the outer side by a ring-shaped rigid
body 19, as shown in FIG. 4 which is a shear deformation view of the shear spring 16, a force
acting in a direction B parallel to the surface in contact with the elastic body 15. The components
of the shear spring 16 undergo shear deformation such that the cross section of the shear spring
16 becomes a parallelogram. Due to this shear deformation, the piezoelectric vibrator 10 and the
elastic body 15 become one body and are pushed up in the direction perpendicular to the
transmission surface 21. On the other hand, when the piezoelectric vibrator 10 is contracted in
the radial direction, conversely, the piezoelectric vibrator 10 and the elastic body 15 become one
body and are pushed down in the direction perpendicular to the wave transmitting surface 21. As
described above, when the piezoelectric vibrator 10 expands and contracts in the radial direction,
the transmitting wavefront 21 vibrates in a piston, and a sound wave is transmitted in the
medium (in water). At this time, since the medium outside the transmitter flows into the cavity 17
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through the orifice 18, the static pressure acting on the outside of the shear spring 16 and the
static pressure acting on the inside of the shear spring 16 are balanced. . In the present
embodiment, in order to increase the transmission sound pressure of the transmission device, the
transmission surface performance is expanded, that is, the diameter of the piezoelectric vibrator
10 is increased. Further, the piston vibration displacement in the direction perpendicular to the
wave transmitting surface 21 of the piezoelectric vibrator 10 is enlarged, and the large radial
displacement of the end surface of the piezoelectric vibrator due to the radial spreading vibration
of the piezoelectric vibrator 10 is converted into the vertical direction. A mechanism is provided.
The support mechanism is composed of an elastic body 15, a shear spring 16 and a rigid body
19. Specifically, the following measures are taken to improve the transmission sound pressure.
The elastic body 15 is softer than the piezoelectric vibrator 10 and has an appropriate hardness
in order to prevent the radial vibration of the piezoelectric vibrator 10 from breaking and not to
be broken by pressure when the shear spring 16 is pressed. It is made of a polymer material
such as polyethylene. Further, the radial thickness of the cross section of the elastic body 15 is
reduced so as to be sufficiently higher than the transmission frequency for the thickness
resonance in the radial direction of the elastic body 15. By doing so, the circular elastic body 15
can be vibrated to freely expand and contract only in the circumferential direction. Further, in
order to prevent the shear spring 16 from being deformed by compression, the thickness of the
portion other than the portion in contact with the elastic body 15 and the portion in contact with
the rigid body 19 is increased. On the other hand, in order to freely deform the shear force
received from the elastic body 15, the bending stiffness of the four rectangular sections in cross
section is reduced. Therefore, as shown in FIG. 1, the four corners are rounded. By doing this, the
radial displacement of the piezoelectric vibrator 10 and the elastic body 15 is converted into the
direction perpendicular to the radial direction by the function of the shear spring 16 without
being restricted. According to this method, it is possible to make vertical displacement of the
piezoelectric vibrator 10 the same as radial displacement or to amplify it based on the crosssectional shape of the annular elastic member 15. That is, the cross-sectional shape of the elastic
body 15 of FIG. 1 is made a triangle of another angle, and the attachment of the shear spring 16
can set the vertical displacement arbitrarily by changing the angle. Further, with reference to
FIGS. 5 and 6, a specific example of the present embodiment will be described in detail using
simulation results. Here, in order to simplify the explanation, it is assumed that a transmitter is
placed in the air and that water is not loaded around the transmitter. FIG. 5 shows a vibration
system of the piezoelectric vibrator 10 having an annular elastic body 15 and a shear spring 16
around the periphery used for the simulation. The radius of the piezoelectric vibrator 10 is
represented by a, and the thickness is represented by h1, and the outer radius of the annular
elastic body 15 having a triangular cross section in the radial direction is represented by C1
average radius by b (= (a + c) / 2). Further, the length of the outer side line of the annular elastic
member 15 is h, and the inclination angle of the side line is 線. The shape of the shear spring 16
is represented by a width h and a height ρ as shown in the figure. Assuming that the transverse
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elastic modulus of the shear spring 16 is G, the shear force acting on the shear spring 16 is per
unit area.
Therefore, the force in the radial direction is uj cos2ψ per unit area, and assuming that the
equivalent spring constant focused on the radial direction is K, K becomes j cos2ψ per unit area.
Further, in order to prevent the shear deformation of the elastic body 15, the lateral elastic
modulus of the shear spring 16 is selected to be smaller than that of the elastic body 15. Table 1
shows material constants and dimensions used as calculation conditions. Table 1 Material
Constants and Dimensions In FIG. 6, it acts on the natural vibration mode and natural frequency
of only the piezoelectric vibrator 10 calculated based on the calculation conditions of Table 1,
and further on the circular elastic body 15 and the radial direction around it. The natural
vibration mode and natural frequency when mechanical impedance by shear spring 16 is
attached are shown. As apparent from this figure, the natural frequency of only the piezoelectric
vibrator 10 is at 6.53 KHz, but when the mechanical impedance is attached, the natural
frequency rises to 6.70 KHz. This is the effect of the mechanical impedance loading of the elastic
body 15 and the shear spring 16 outside it. However, comparing the vibration modes, it can be
seen that both have almost the same shape 1). That is, the vibration displacement around the
disk of the piezoelectric vibrator 10 itself maintains a large value without being affected by the
external side of the piezoelectric vibrator 10 (this, even if the mechanical impedance selected
here is applied). Therefore, the radial displacement is transmitted as displacement of the same
amplitude while maintaining a large value in the direction perpendicular to the wave transmitting
surface 21 by the conversion mechanism of the shear spring 16. On the other hand, the natural
frequency of only the elastic body 15 was calculated to be 944 Hz. Furthermore, the natural
frequency of a system consisting of the elastic body 15 and the shear spring 16 outside thereof
was calculated to be 16.3 KHz. Therefore, the influence of the natural vibration of the elastic
body 15 and the system consisting of the elastic body 15 and the shear spring 16 can be ignored
for the drive frequency of 6.7 KHz. This brings about the advantage that peeling of the bonding
surface between the piezoelectric vibrator 10 and the elastic body 15 hardly occurs when the
wave transmitter of this embodiment is actually manufactured. As described above, this
embodiment has the following advantages. (1) In order to convert the radial expansion vibration
of the disk-shaped piezoelectric vibrator 10 into vibration in the direction perpendicular to the
wave sending surface 21, a support mechanism including the elastic body 15, the shear spring
16 and the rigid body 19 is provided. The displacement of the same size as the large
displacement around the piezoelectric vibrator 10 or the amplified displacement in the vertical
direction can be accurately taken out. (2) The transmission surface 21 of the piezoelectric
vibrator 10 performs faithful piston vibration if the plate-like piezoelectric vibrator 10 is selected
to have an appropriate thickness so as not to generate thickness vibration and bending vibration
in the target frequency range. .
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(3) If the diameter of the piezoelectric vibrator 10 is increased, the natural frequency decreases,
and a large displacement around the piezoelectric vibrator can be taken out, so that a low
frequency high power transmission can be achieved. (4) If the material of the elastic body 15 to
be fitted to the side surface of the piezoelectric vibrator 10 is selected to have a high density, the
natural frequency of the transmitter is lowered. That is, although a single piezoelectric vibrator
having a small diameter has a high natural frequency, the natural frequency may be lowered by
increasing the mass of the elastic body 15 while keeping the diameter of the piezoelectric
vibrator 10 small. it can. (5) The pressure balance structure in which the inside of the cavity 17
communicates with the outside of the transmitter via the orifice 18 has good water resistance
and can be used in deep water. (6) The transmitter has a large area in the radial direction but is
thin, so it can be easily bolted to a mount or a housing and used. The present invention is not
limited to the illustrated embodiment. For example, the shear spring 16 may be changed to a
shape other than a rectangular shape, the shape of the elastic body 15 or the rigid body 19 may
be changed to another shape, or an orifice accordingly. Various modifications can be made, such
as providing the formation position 18 at a location other than the illustrated one. (Effects of the
Invention) As described above in detail, according to the present invention, in order to convert
radial expansion vibration of a disk-like piezoelectric vibrator into vibration in a direction
perpendicular to the wave transmission surface, Since a support mechanism consisting of an
elastic body, a shear spring and a rigid body is provided on the outside, high power can be
obtained by increasing the amplitude of the transmitting wavefront, and low frequency output
can be obtained by enlarging the diameter of the piezoelectric vibrator. At the same time, it is
possible to faithfully vibrate the transmission surface of the piezoelectric vibrator with a piston.
Furthermore, since the structure is simple, manufacture is easy, mechanical strength is large, and
good transmission performance can be obtained. Moreover, since the shear spring has a pressure
balance structure communicating with the outside through the orifice, it has good water
resistance and can be used in deep sea.
[0002]
Brief description of the drawings
[0003]
1 (a) and 1 (b) are block diagrams of the underwater acoustic wave transmitter showing one
embodiment of the present invention, and FIG. 1 (a) is a plan view and FIG. 1 (b) is a sectional
view taken along the line A-A. Fig. 2 is a block diagram of a conventional disc type underwater
acoustic wave transmitter, Fig. 3 is a block diagram of another disc type underwater acoustic
wave transmitter of the prior art, and Fig. 4 is a shear in Fig. 1 5 shows a shear deformation of a
spring, FIG. 5 shows a vibration system of a piezoelectric vibrator having an annular elastic body
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and a shear spring around the periphery in FIG. 1, FIG. 6 shows one of the piezoelectric vibrators
in FIG. It is a figure which shows the next radial direction expansion natural vibration mode.
10 · · · Piezoelectric vibrator, 11.12 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · elastic
body, 16 · · · shear springs, 17 ...... cavity 18 ...... orifice, 19 ...... rigid, 20 ...... molding material, 21
...... transmitting surface.
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