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JPH08214394

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JPH08214394
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electroacoustic transducer for use in an underwater transducer, and more particularly to an
electroacoustic transducer for use at low frequencies.
[0002]
2. Description of the Related Art Conventionally, this type of underwater low-frequency
electroacoustic transducer converts low-frequency acoustic waves into water by converting
electrical energy into mechanical energy and transmitting the mechanical energy into the water. .
As a conventional electroacoustic transducer utilizing bending vibration, for example, as shown
in FIG. 5, a piezoelectric vibrator 10a and a shell 1b having an elliptical cross-sectional shape as
shown in FIG. And fixed in one place of the long diameter portion of the shell 1b by adhesion or
bolting, the piezoelectric vibrator 10a flexes and vibrates the shell 1b to emit ultrasonic waves in
water. The vessel is disclosed. The head mass 10c located at both ends of the piezoelectric
vibrator 10a and the inner diameter surface on the short arc side of the shell 1b are coupled at
one place.
[0003]
FIG. 6 is a diagram showing the operating state of the shell. In FIG. 6, a solid line indicates the
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equilibrium state of the shell, and a broken line indicates the state of deformation of the shell
when a force is applied to the major diameter portion of the shell in the direction of the thick
arrow. ξa is the displacement of the shell in the minor axis direction, and ξb is the
displacement in the major axis direction. As can be seen from FIG. 6, in this type of
electroacoustic transducer, by displacing the major diameter portion of the ellipse, the minor
diameter portion can be displaced more largely to emit an acoustic wave into the water.
[0004]
In the conventional electroacoustic transducer, in order to efficiently emit sound waves, it is
necessary to increase the volume velocity, and it is apparent from FIG. 6 that the displacement
ξa of the minor diameter of the shell is apparent. The ratio ξa / ξb of the displacement ξb of
the major axis to must be increased. For this purpose, it is necessary to reduce the ratio a / b of
the major diameter 2b to the minor diameter 2a of the shell. However, when the ratio of minor
axis to major axis ratio a / b of the shell is 1, that is, when the cross section of the shell is
circular, it is most resistant to hydrostatic pressure, but as a / b becomes smaller, it is deformed
by hydrostatic pressure, It will be crushed. For this reason, due to this deformation, a tensile
force is exerted on the bonding portion where the inner diameter surface of the shell and the
both ends of the piezoelectric vibrator are bonded by bonding or bolting, and peeling of the
bonding portion when exceeding a certain deformation. Or in order to cause destruction of a
piezoelectric vibrator, it was difficult to improve water pressure resistance, maintaining the
radiation efficiency of a sound wave.
[0005]
One solution is to feed compressed air into the shell to compensate for the hydrostatic pressure.
However, it is necessary to add a cylinder, etc., resulting in an increase in size and complexity of
the structure. It is not practical because it has problems.
[0006]
An object of the present invention is to solve the above-mentioned problems and to provide an
electroacoustic transducer capable of improving the water pressure resistance while maintaining
the radiation efficiency of sound waves.
[0007]
According to the present invention, there is provided an electro-acoustic transducer for bending
and vibrating a shell having an inner diameter surface of an elliptical cross section by a drive unit
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comprising a piezoelectric vibrator and a head mass provided at both ends thereof. The drive unit
is disposed in the shell such that the head masses are in contact with each other on two lines
which are in a symmetrical positional relationship with each other in an inner diameter surface
on the short arc side of the shell. An acoustic transducer is obtained.
[0008]
Further, according to the present invention, in the electro-acoustic transducer in which a shell
having an inner diameter surface having an elliptical cross-sectional shape is bent and vibrated
by a drive unit including a piezoelectric vibrator and a head mass provided at both ends thereof.
A metal plate is attached to the inner diameter surface of the head, and each of the head masses
is provided with two notched grooves, and a rod is accommodated in the notched groove, and the
rod is the metal plate of the metal plate. An electro-acoustic transducer is obtained, which is
arranged in the shell in such a way as to be in contact with two lines which are in a symmetrical
positional relationship with each other in an inner diameter surface.
[0009]
DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will
now be described with reference to FIGS.
FIG. 1 is a longitudinal sectional perspective view showing an embodiment of the present
invention.
In FIG. 1, the piezoelectric vibrator 1a is formed by laminating a large number of plate-like
ceramic elements, and is electrically connected in parallel, so that a large displacement can be
obtained with a relatively small voltage.
At both ends of the piezoelectric vibrator 1a, a head mass 1c for smooth coupling with the shell
1b is attached by an adhesive or the like, and a driving portion is formed by the piezoelectric
vibrator 1a and the head mass 1c.
The driving portion is fitted in the shell such that the head masses 1c located at both ends are in
contact with each other on two lines which are in a symmetrical positional relationship with each
other in the inner diameter surface on the short arc side of the shell 1b. The connection point
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with 1b (hereinafter referred to as a connection point) is provided in the vicinity of the node of
the shell 1b. The material of the shell 1b is generally high-tensile steel or the like in order to
achieve low frequency and water pressure resistance. Before the drive is inserted into the shell
1b, the shell 1b is stretched in advance, and after the drive is inserted, a compressive force is
applied to the drive. Further, both sides of the shell 1b are covered with oval side plates to keep
the water tight.
[0010]
FIG. 2 is an enlarged view showing the connection point between the drive unit and the shell.
One end of the head mass 1c has a semi-elliptical shape so as to couple only near the node of the
shell 1b. In this case, since two connecting points are required, at least the radius of curvature of
the semi-elliptic of the head mass 1c is the short arc of the short circular arc forming the inner
diameter surface in the major diameter direction among the inner diameter surfaces of the shell
1b having an oval cross section. It needs to be larger than the radius of curvature. The head mass
1c and the shell 1b are held in position by receiving a compressive force, and are not fixed by
bonding or the like, and slippage occurs when the shell is deformed.
[0011]
FIG. 3 is a view showing a deformed state of the shell and the head mass shown in FIG. 2 before
and after application of hydrostatic pressure. The analysis was performed by the finite element
method (FEM). The analysis conditions are the length 50 cm of the major axis of the shell 1 b, the
ratio of minor axis to major axis of 0.45, the thickness 2 cm of the shell 1 b, and the material is
iron. The vertical axis and the horizontal axis in FIG. 3 indicate xy coordinates, and the origin (0,
0) of the coordinates is an inner contact on the major axis of the shell 1 b. The solid line in the
figure shows the outline of the inside of the shell 1b in the equilibrium state of the shell 1b, the
dotted line shows the outline when hydrostatic pressure is applied, and the alternate long and
short dash line shows the shape of the head mass 1c. The vertical axis and the horizontal axis
respectively have a scale of 10 mm. The point B on the major axis of the shell 1b moves to the
point B 'when hydrostatic pressure is applied, and it can be seen that the point B is deformed by
3.2 mm.
[0012]
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If the head mass is connected to one point B on the shell as in the conventional method, the
connection point is separated when the hydrostatic pressure is applied, as shown in the figure,
and the contact point is non-contact, and the force from the drive unit to the shell Can not be
transmitted. Also, it is clear that when the head mass and the shell are bonded, a very strong
tensile force is exerted on the joint. On the other hand, in the case of the present invention, the
point A on the shell 1b connected to the point α of the head mass 1c moves to the point A ′
after application of hydrostatic pressure, but instead, the point C on the shell 1b Is moved to the
same position as the point A, and the point α on the head mass 1c is always coupled to the shell
1b. Therefore, even after the deformation of the shell 1b due to hydrostatic pressure, the sliding
force generated at the joint between the head mass 1c and the shell 1b does not generate a
tensile force at the drive portion and a compressive force always works, improving the water
pressure resistance. Further, since the drive unit and the shell 1b are always coupled, the force
can be transmitted from the drive unit to the shell 1b, and sound waves can be emitted
efficiently.
[0013]
Next, another embodiment of the present invention will be described with reference to FIG. FIG. 4
is a longitudinal sectional view showing another embodiment of the present invention. In FIG. 4,
the head mass 1c is cut into a circular shape so as to be able to accommodate a cylindrical rod
1e. The notch groove is slightly larger than the diameter of the rod 1e, and the accommodated
rod 1e can freely rotate. It is known that the shell 1b can be reduced in size and weight by using
a reinforced plastic such as CFRP. However, since a reinforced plastic etc. has a relatively rough
surface compared to metal, a plate made of a metal material equivalent to the head mass on the
inner diameter surface on the short arc side of the shell 1b to reduce friction due to contact with
the rod 1e. It is necessary to attach 1d by adhesion etc. The attachment area of the plate 1d is
always an area where the rod 1e and the plate 1d come into contact, in consideration of the
deformation of the shell due to hydrostatic pressure. As a result, since the rod 1e is coupled to
the shell 1c through the plate 1d, the rod 1e is smoothly coupled, the transmission of the force
from the drive unit is improved, and the durability against friction is also improved. The wedge
mechanism 1f is pinched by the piezoelectric element 1a, and the length of the drive part can be
finely adjusted by tightening the nut 1g. As a result, the operation of fitting the drive unit into the
shell 1b is simplified, and the compression force on the piezoelectric element can be freely finely
adjusted. It is obvious that in this structure also, the water pressure resistance can be improved
by driving the vicinity of the node of the shell. In the present embodiment, a piezoelectric
element is used as the drive element of the drive unit, but it may be a magnetostrictive element
made of, for example, Tb03Dy07Fe2.
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[0014]
As described above, according to the present invention, by providing two driving points of the
shell near the node of the shell, the radiation efficiency of the sound wave is maintained as
compared with the conventional electroacoustic transducer. It is possible to improve the water
pressure resistance as it is.
[0015]
Brief description of the drawings
[0016]
1 is a longitudinal sectional perspective view showing an embodiment of the present invention.
[0017]
2 is a partially enlarged vertical sectional view showing the connection point of the drive portion
and the shell.
[0018]
3 is a diagram showing the deformation state of the shell and head mass shown in FIG. 2 before
and after the application of hydrostatic pressure.
[0019]
4 is a partially enlarged vertical sectional view showing another embodiment of the present
invention.
[0020]
5 is a longitudinal sectional perspective view showing a conventional electro-acoustic transducer.
[0021]
6 is a diagram showing the operating state of the shell.
[0022]
Explanation of sign
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[0023]
1a Piezoelectric Vibrator 1b Shell 1c Head Mass 1d Plate 1e Rod 1f Wedge Mechanism 1g Nut
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