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JPH04309881

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DESCRIPTION JPH04309881
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the
improvement of a submersible transducer for exciting a vibrating portion, and more particularly
to a submersible which enables elimination of unnecessary vibration modes or enhancement of
radiation surface vibration by excitation of a base portion. It relates to a transducer.
[0002]
2. Description of the Related Art Conventionally, when low frequency sound waves are radiated
into water, in order to make a relatively small and light-weight transmitter, it is disclosed in
Japanese Patent Application No. 60-021148 and Japanese Patent Application No. 62-88811. As
can be seen, a structure has been devised in which the diaphragm of the sound wave emitting
surface has a flexural vibration mode. However, the structure shown above has the following
problems, and there is a problem that needs to be solved.
[0003]
In the underwater transducer, it is preferable that the transmitter and the receiver have the same
structure, and in the present specification, the present invention will be described from the
viewpoint of the transmitter.
[0004]
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For example, in Japanese Patent Application No. 62-088811, the vibration mode is described
only for the acoustic radiation surface, but in practice the extent to which the base other than the
radiation surface can not be neglected May have a vibration amplitude of
For this reason, an acoustic vibration wave is actually emitted also from the base part, and as a
result, this is introduced to the output side from the acoustic radiation surface and interferes
with this, resulting in a problem that the radiation output is inhibited.
[0005]
In the conventional structure, since the radiation output is controlled only by the excitation of the
excitation unit, if the radiation output is to be increased, the excitation input voltage to the
excitation unit is increased or the area of the excitation unit is increased. It is necessary to
increase the number of excitation elements so as to increase the number of excitation elements.
Therefore, to avoid enlarging the excitation part, it was necessary to rely solely on the means for
increasing the input voltage. The increase of the input voltage is limited, for example, in view of
the dielectric breakdown of the piezoelectric element as a vibrating element to which it is
applied. Therefore, conventionally, it has been difficult in practice to increase the adjustment
range for increasing the output.
[0006]
Furthermore, when a large number of transmitters are arranged and used, transmission outputs
mutually interfere with each other, which may cause variations in the transmitter outputs. It
could cause damage to the drive side.
[0007]
In order to solve such problems, the present invention provides an underwater transducer
capable of achieving the following objects.
That is, the first purpose is to eliminate vibrational displacement of the base. The second object is
to make it possible to further enhance the output than ever before. The third object is to make it
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easier to align the output from each transmitter when using a large number of transmitters in
array.
[0008]
SUMMARY OF THE INVENTION In order to achieve the above object, an underwater transducer
according to the present invention is provided with a piezoelectric element laminate for exciting
a base portion in the base portion. That is, in the present invention, in the configuration of the
underwater transducer, in addition to the excitation of the excitation portion as in the prior art,
the base portion can be simultaneously excited. Here, it is effective and preferable that the
piezoelectric element laminate provided in the base portion be in close contact with the base
portion as a bimorph-like laminate.
[0009]
When the excitation unit is conventionally excited, an acoustic output can be obtained from the
acoustic radiation surface, but at the same time vibration is caused in the base. Therefore,
according to the present invention, the base portion is excited by the piezoelectric element
laminate provided in the base portion, and in that case, (1) the excitation mode of the base
portion according to the present invention is opposite in phase to the vibration mode of the base
portion by the conventional excitation. It becomes possible to make vibration displacement by
both excitations zero if it excites so that it may become and it adjusts amplitude. This eliminates
unwanted vibration modes in the base and does not exert unwanted interference on the acoustic
output from the acoustic emission surface. (2) By exciting the excitation mode according to the
present invention so as to be in phase with the vibration mode of the base by the conventional
excitation, the vibration displacement of the acoustic radiation surface can be further enhanced
compared to the case of only the conventional excitation. . Moreover, since the increase of the
output does not increase the excitation input to the conventional excitation unit, the dielectric
breakdown of the piezoelectric element does not occur. Furthermore, when a large number of
transducers are used in array, the vibration of the acoustic radiation surface of each array
transducer is detected by a known method (for example, the method disclosed in JP-A-61-86668)
and the vibrations are aligned. By adjusting the excitation amplitude to the base of each
transducer as described above, it is possible to make the outputs of the transducers uniform. In
this case, since the adjustment is performed by adjusting the excitation of the base without
enhancing the excitation input of the excitation unit, the drive circuit is not damaged due to the
excitation.
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[0010]
For example, a laminate in which a large number of piezoelectric elements are stacked in the left
and right directions is further stacked in the upper and lower directions, and a voltage is applied
thereto to cause polarization in each piezoelectric element as shown in FIG. Is known as a
bimorph element, in which, for example, when the upper stack is stretched, the lower stack
operates to shrink, thereby acting as an efficient piezoelectric effect element. It has been known.
In the present invention, if the piezoelectric element is brought into close contact with the base
as a bimorph-like laminate, it is possible to give the base a “swarf” vibration of the plate, that
is, a bending mode using the highly efficient bimorph piezoelectric effect. This makes it possible
to efficiently achieve the three objects of the invention with relatively small excitation inputs
other than conventional excitation.
[0011]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present
invention will be described below with reference to FIG. In FIG. 1, the acoustic radiation surface 1
vibrates in a vibration mode having a vibration displacement as shown by an arrow by vibration
excitation by applying an alternating voltage to the vibration parts 14a and 14b of the vibration
part 2. At this time, the base 3 vibrates in the vibration mode as shown by the downward arrow.
In order to cancel the vibration of the base portion 3 which is the first object of the present
invention, the piezoelectric element laminate 5 is bonded to the base portion 3 via the insulator 7
as an example. At this time, it is desirable that the insulator 7 be a ceramic or the like having a
small vibration loss because it is necessary to strongly transmit the vibration. As shown in FIG. 2,
the configuration of the piezoelectric element laminate 5 used here is such that the piezoelectric
elements 53, 54, 55, 56,... The upper electrode is connected to the lead wire 51, and the lower
electrode is connected to the lead wire 52. Thus, when an alternating voltage is applied between
the lead wires 51 and 52, bending vibration is caused in the vibration mode as shown by the
arrow. At this time, it is important that each of the piezoelectric elements 53, 54, 55, 56,... And
the insulating plate etc. 7 be firmly adhered by a hard epoxy resin or the like. This piezoelectric
element laminate 5 acts to cancel the vibration if it vibrates in the opposite phase to the vibration
mode shown downward in FIG. 1, and if the vibration amplitude is matched, the vibration of the
base portion 3 is the first purpose. It becomes zero. At this time, if the direction of the alternating
voltage applied to the lead wires 51 and 52 is reversed, that is, the phase is reversed, the
vibration becomes opposite to the arrow shown in FIG. 2, and the vibration of the base 3 in FIG.
Therefore, the vibration displacement of the acoustic radiation surface 1 of FIG. 1 is enhanced. It
operates to achieve the second object. If the voltage applied to the lead wires 51 and 52 is
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controlled in this state, the vibration displacement amount of the acoustic radiation surface 1 can
be controlled, and the third object can be achieved.
[0012]
Although the piezoelectric element laminate 5 is illustrated on the outer side in FIG. 1, that is, on
the lower side of the same figure, the same effect can be obtained by dividing and bonding the
inner side, ie, on the upper side of the base 3 in the same figure. .
[0013]
FIG. 3 shows experimental data of the linearity of the acoustic radiation level when the
piezoelectric element laminate 5 is not driven and when it is driven as an example applied to the
second object.
From this figure, it can be seen that the effect of driving the piezoelectric element stack 5 is
enhanced by about 2 dB. The vertical axis in FIG. 3 represents the magnitude of the acoustic
radiation sound pressure at a point 1 m away from the transmitter of the sound source in dB
when the sound pressure is 1 μPa (Pa is Pascal) is 0 dB. It is a thing.
[0014]
According to the present invention, the vibration of the base portion 3 as the first object is
eliminated by controlling the amplitude and the phase by exciting the piezoelectric element
laminate 5 in close contact with the base portion 3. The vibration displacement of the acoustic
radiation surface 1 as the second object is enhanced, and the vibration displacement as the third
object can be controlled.
[0015]
Brief description of the drawings
[0016]
1 is a cross-sectional view of an embodiment of the present invention.
[0017]
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2 is a cross-sectional view of a piezoelectric element laminate according to an embodiment of the
present invention.
[0018]
Fig. 3 Experimental values of piezoelectric element applied voltage and acoustic radiation level
relationship.
[0019]
Explanation of sign
[0020]
DESCRIPTION OF SYMBOLS 1 ... Acoustic radiation surface, 1a ... Boundary area, 2 ... Excitation
part 2a ... Excitation element element, 3 ... Base part, 3a ... Mounting part, 5 ... Piezoelectric
element laminated body, 51, 52 ... Lead wire, 53, 54, 55, 56: Piezoelectric element, 7: Insulator
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