JPH0520498

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DESCRIPTION JPH0520498
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the
improvement of a receiver having a piezoelectric body.
[0002]
2. Description of the Related Art Conventionally, underwater acoustic wave receivers have been
used to receive underwater sound. This is a receiver that receives sound propagating in water by
a piezoelectric body and outputs the sound as an electrical signal to the outside. FIG. 3 shows the
configuration of a receiver according to a conventional example and having the same
configuration as that disclosed in JP-A-59-176992. In particular, the cross section is shown in
FIG. 3 (a), and the element connection is shown in FIG. 3 (b).
[0003]
As shown in FIG. 3 (a), in this conventional example, two cylindrical piezoelectric vibrators 8 and
9 are coaxially arranged, and the inner piezoelectric vibrator 9 is a sound insulation layer. And
the outer piezoelectric vibrator 8 is in contact with the outer layer 11. In a receiver having such a
configuration, the outer piezoelectric vibrator 8 receives the sound wave via the outer layer 11
that transmits the sound wave. The piezoelectric vibrator 8 converts the received sound wave
into a voltage, and outputs the voltage from plus and minus electrodes formed on the front and
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back (outside and inside of the cylinder). This voltage is represented by Es in FIG. 3 (b).
[0004]
The inner piezoelectric vibrator 9 is connected in reverse phase to the outer piezoelectric
vibrator. That is, as also shown in FIG. 3B, the negative electrode of the piezoelectric vibrator 9 is
short-circuited with the negative electrode of the piezoelectric vibrator 8, and the positive
electrode of the piezoelectric vibrator 8 and the positive electrode of the piezoelectric vibrator 9
It is wired to output a voltage from between. The piezoelectric vibrator 9 is a vibrator for
canceling an acceleration component included in the output voltage of the piezoelectric vibrator
8.
[0005]
That is, this conventional example has a cable-like appearance, and when acceleration is applied
in the shear direction of the cable, the piezoelectric vibrators 8 and 9 respectively generate a
voltage Eα applied to the acceleration. However, as a result of the piezoelectric vibrators 8 and 9
being connected in reverse phase, the output voltage from the series connection becomes a
voltage in which the voltage Eα applied to the acceleration is offset. That is, only the voltage Es
related to the reception of the sound wave.
[0006]
Thus, conventionally, the voltage Eα applied to the acceleration is offset. In general, the
acceleration voltage Eα increases the noise level and degrades the S / N of the receiver. This
conventional example is used in a so-called non-resonant system, that is, in a frequency band
lower than the resonance point, and such suppression of acceleration sensitivity is very effective
in improving the S / N.
[0007]
However, in the conventional wave receiver having such a configuration, the acceleration
sensitivities of the two vibrators are made equal or the two vibrators are When the acceleration
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sensitivity is different, it is necessary to finely adjust the gain of the head amplifier to cancel the
voltage related to the acceleration. This, together with the need to use two types of vibrators of
different sizes, has been a manufacturing obstacle.
[0008]
The present invention has been made to solve these problems, and while using vibrators of the
same size and the same acceleration sensitivity, the voltage component due to acceleration is
offset to take out only the voltage related to the sound wave. To provide a receiver capable of
[0009]
SUMMARY OF THE INVENTION In order to achieve the above object, according to the present
invention, a plurality of piezoelectric bodies formed of a perforated piezoelectric material, and
the piezoelectric bodies being supported by point contact on both sides And supporting the
piezoelectric body in phase.
[0010]
In the present invention, the plurality of piezoelectric members are formed of a perforated
piezoelectric material.
The perforated piezoelectric material is, for example, a material disclosed in JP-A-1-172281
according to the prior application of the applicant of the present application, whereby a
piezoelectric body with a low specific gravity is obtained, and the acceleration component is
suppressed.
Further, in the present invention, the piezoelectric body is point-contacted and supported on both
sides of the support housing. Due to the support on both sides, an acceleration component is
generated in the opposite phase in each piezoelectric body. Therefore, the acceleration
component is electrically canceled by the in-phase connection of the piezoelectric body.
Furthermore, the point contact support increases the freedom of movement of the piezoelectric
body and reduces the acousto-electrical conversion loss.
[0011]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the
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present invention will be described below with reference to the drawings.
[0012]
FIG. 1 shows the configuration of a wave receiver according to an embodiment of the present
invention.
In particular, FIG. 1 (a) shows the cross section of the embodiment, and FIG. 1 (b) shows the
element connection. As shown in this figure, the present embodiment has two piezoelectric
vibrators 1 and 2. The piezoelectric vibrators 1 and 2 have a cylindrical shape, and electrodes
(not shown) are formed on the front and back (outside and inside of the cylinder). Leads 7 are
drawn from the electrodes, respectively.
[0013]
The piezoelectric vibrators 1 and 2 are supported and fixed on both sides of a support housing 4
via a connecting rod 3. The connecting rod 3 has a function of point-contacting the piezoelectric
vibrators 1 and 2 on the support housing 4. In addition, the inside of the piezoelectric vibrators 1
and 2 is filled with the foam rubber 5 of a closed cell, and the whole receiver is molded by the
urethane rubber 6.
[0014]
Further, in this embodiment, the piezoelectric vibrators 1 and 2 are connected in phase as shown
in FIG. 1 (b). That is, the connection is made so that the voltage generated in the piezoelectric
vibrator 1 and the voltage generated in the piezoelectric vibrator 2 are added. Furthermore, in
the present embodiment, the material forming the piezoelectric vibrators 1 and 2 is a so-called
porous piezoelectric material. As a piezoelectric material, lead zirconate titanate (PZT) is
conventionally known, but its specific gravity is as large as about 7.4. However, since the voltage
generated by the acceleration is in proportion to the specific gravity of the piezoelectric material,
the unnecessary voltage generated by the acceleration applied to the entire receiver is higher as
the specific gravity is larger. The porous piezoelectric material used in this example is disclosed
in the above-mentioned JP-A-1-172281, etc., and its specific gravity is, for example, about 4.6.
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[0015]
FIG. 2 shows the manufacturing process of this porous piezoelectric material. The piezoelectric
vibrators 1 and 2 formed of a porous piezoelectric material are prepared by mixing a
piezoelectric material 100 such as PZT and a high molecular polymer 101 such as methacrylic
resin (102), and ) And further firing at a predetermined temperature (104). Further, in order to
take out a voltage from the piezoelectric vibrators 100 and 101, it is necessary to bake an
electrode on the surface thereof. After the baking 105 is performed, polarization (106) is
performed in a predetermined direction to obtain piezoelectric vibrators 1 and 2 formed of a
porous piezoelectric material having desired characteristics. For example, when the mixing ratio
of the polymer 101 to the PZT 100 is 15 wt%, the ratio (porosity) of pores generated by burning
out the polymer 101 by the firing 104 is 41%, and the specific gravity is Piezoelectric vibrators 1
and 2 formed of the porous piezoelectric material of 4.6 are obtained.
[0016]
This embodiment has the above construction. In this embodiment, when a sound wave is
propagated and received from the water via the urethane rubber 6 to the piezoelectric vibrators
1 and 2, the voltage related to the output from the piezoelectric vibrators 1 and 2 is shown in
FIG. 1 (b). The signals are added by wiring and output as a receiver signal. This is due to the
isobaric propagation of underwater acoustic waves.
[0017]
The piezoelectric vibrators 1 and 2 are fixed to both sides of the support housing 4 by a
predetermined number of (for example, three) connection rods 3. Therefore, the radial movement
of the cylinders of the piezoelectric vibrators 1 and 2 is easy, and the underwater acoustic wave
can be efficiently converted into an electric signal.
[0018]
The external acceleration component (for example, vibration) applied to the wave receiver is
applied to the support housing 4 and transmitted to the piezoelectric vibrators 1 and 2 through
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the connecting rod 3, respectively. When the support housing 4 moves upward, this acceleration
applies a compressive force to the piezoelectric vibrator 1 and an expansion force to the
piezoelectric vibrator 2. Conversely, when the support housing is moved downward, an extension
force is applied to the piezoelectric vibrator 2 and a compression force is applied to the
piezoelectric vibrator 1. The voltage generated by the acceleration applied in this manner, that is,
the acceleration signal component is generated in the opposite phase in each of the piezoelectric
vibrators 1 and 2. The voltages related to the acceleration generated in the opposite phase in this
manner are electrically canceled each other by the wiring shown in FIG. 1 (b). Therefore, the
component related to the acceleration is not included in principle in the receiver component.
[0019]
However, in principle, although offsets are made in this way, voltage related to acceleration may
remain due to element characteristics, variations at the time of manufacture, and the like. On the
other hand, the voltage generated by acceleration is proportional to the mass of the piezoelectric
vibrators 1 and 2 and therefore sufficiently suppressed in the piezoelectric vibrators 1 and 2
formed of a porous piezoelectric material having a smaller specific gravity than before. Only the
acceleration component of the level is output. Therefore, according to the present embodiment,
the influence of the acceleration component is eliminated not only in terms of the material of the
piezoelectric vibrators 1 and 2, but also in terms of the support structure of the piezoelectric
vibrators 1 and 2, and wire connection. The unnecessary voltage generated by the acceleration is
reduced. Further, since the piezoelectric vibrators 1 and 2 are attached to the support housing 4
by the connecting rod 3, the efficiency (conversion efficiency) of converting underwater acoustic
waves into electric signals is increased. In addition, the number of connecting rods 3 may not be
three.
[0020]
As described above, according to the present invention, the piezoelectric body is formed of the
perforated piezoelectric material, and the piezoelectric body is supported so as to be pointcontact supported on both sides of the support housing. Furthermore, since the piezoelectric
members are connected in phase, a receiver with less noise which can remove the acceleration
component in material, structure and connection can be obtained. In addition, point contact
support increases the degree of freedom of movement of the piezoelectric body, and the
conversion efficiency of sound waves into electric signals increases.
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