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JPS62220099

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DESCRIPTION JPS62220099
[0001]
<Industrial field of application> The present invention radiates a sound wave or an ultrasonic
wave toward the object to be detected, or reflects it back by the object to be detected, such as a
seafloor seismic detector or a fish finder. The present invention relates to an underwater
piezoelectric transducer sheet that receives an incoming reflected wave. <Prior Art> Piezoelectric
organic compounds such as polyvinylidene fluoride, polyvinylidene fluoride, polyvinylidene
chloride, polyvinyl chloride, nylon, etc. or organic substances of synthetic rubbers or synthetic
resins, such as titanium zirconate, lead titanate, etc. A piezoelectric flexible sheet such as a
piezoelectric organic ceramic composite formed by mixing dielectric ceramic particles has a
characteristic that acoustic impedance approximates to acoustic impedance of water, and
therefore, propagates in water as a piezoelectric transducer. Used to receive acoustic waves.
Other than this, there are piezoelectric ceramic plates that are used as piezoelectric transducers.
Furthermore, a piezoelectric flexible sheet or a piezoelectric ceramic plate is also used as a
transmitter for emitting a sound wave or an ultrasonic wave toward a detected object. The
conventional constitution of the piezoelectric transmitting and receiving sheet for water using a
piezoelectric flexible sheet or a piezoelectric plate such as piezoelectric ceramic, as shown in FIG.
8, electrodes on the upper and lower surfaces of the piezoelectric plate a made of the
piezoelectric material A predetermined DC voltage is applied between the electrodes c and c to
polarize the piezoelectric plate a in the thickness direction, and this is immersed in water to apply
an alternating voltage to the electrodes c and c. Alternatively, an ultrasonic wave is oscillated, an
output signal is taken from between the electrodes c, and an acoustic wave propagating in water
is received. <Problems to be Solved by the Invention> By the way, the piezoelectric plate having
the above-mentioned configuration detects sound under hydrostatic pressure when it is used for
receiving waves, and this sensitivity is the piezoelectric constant of the piezoelectric plate.
Determined by gh. This gh is given by the following equation. Here, the constant g 33 indicates
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the sensitivity to the pressure PI in the thickness direction (polarization direction), and the
constant g zt indicates the sensitivity to the pressure p 2 in the surface direction (direction
perpendicular to the polarization axis). By the way, since g 31 is a negative value, gh <gff 3 holds,
and in the conventional configuration, the value of gh is. It was only g 31 ya-y and low in
sensitivity. This is the same in the case of transmission as well, and there is a disadvantage that
the piezoelectric constant dh is reduced by the water pressure from the surface direction.
According to the present invention, by removing the pressure p2 in the surface direction
(direction perpendicular to the polarization axis) as much as possible, the constant g: 11 is made
equal to zero and the constants gh and g 33 are equalized. It is an object of the present invention
to provide a piezoelectric transducer sheet for water which can improve wave sensitivity and
increase the constant cih to improve transmission performance.
According to the first aspect of the present invention, the outer peripheral edge of the
piezoelectric plate having electrodes formed on the upper and lower sides and polarized in the
thickness direction is a peripheral frame having substantially the same thickness as that of the
piezoelectric plate. A buffer peripheral area such as an air layer 1 foam material layer is
produced between the piezoelectric plate peripheral edge and the frame inner edge, and the
upper and lower outer surfaces of the frame and the piezoelectric plate are covered with resin. It
is said that. In the second invention according to the above-mentioned invention, the outer
peripheral edge of the piezoelectric plate is surrounded by the peripheral frame having
substantially the same thickness as the piezoelectric plate via the space maintaining claw so that
the piezoelectric body can be surrounded by the space maintaining claw. An air layer having a
predetermined interval to be a buffer circumferential area is formed. Furthermore, according to
the third invention, in the above invention, the rigid plates are arranged in a crosswise manner at
the upper and lower positions of the air layer which becomes the buffer circumferential area. In
the above configuration, the pressure p2 in the surface direction (the direction perpendicular to
the polarization axis) acts from the peripheral edge of the piezoelectric transducer sheet, and the
pressure p2 is determined by the peripheral edge of the piezoelectric plate due to the buffer
peripheral region. The impact on is eliminated. For this reason, when used as a receiver, the
surface direction constant g 31 has an apparent zero on the surface. In the second aspect of the
invention, the width of the air layer between the piezoelectric plate and the peripheral frame is
maintained constant by the first spacing holding claw. Therefore, the piezoelectric plate and the
peripheral edge are formed in the process of forming the piezoelectric transmitting and receiving
sheet. The positional relationship with the frame is not biased to one side, and the contact does
not occur, so that the assembly is facilitated and the buffer effect by the air layer can be stably
generated. Furthermore, in the third invention, the rigid plate is extended to the upper and lower
positions of the air layer. When the piezoelectric receiving sheet is immersed deep in water, the
large water pressure may cause the resin layers above and below the air layer to be depressed to
generate a component of force in the surface direction at the periphery of the piezoelectric plate,
which may lower the sensitivity. . Therefore, generation of a component of force in the surface
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direction is prevented by the rigid plate. EXAMPLE Referring to FIG. 1.2, reference numeral l
denotes a rectangular piezoelectric plate 1 made of a piezoelectric flexible sheet such as a
piezoelectric rubber or a piezoelectric ceramic, which is polarized in the thickness direction, and
the upper and lower surfaces thereof are electrodes 2 , 2 are formed so that a signal can be taken
out from between the electrodes 2.2 by the lead wire 3.3. The piezoelectric plate l may be formed
of a thick hydrophone constant 1, for example, a lead titanate (P bT i O: l) based material. A
rectangular frame 10 having substantially the same thickness as that of the piezoelectric plate l
is externally fitted on the outer peripheral edge of the piezoelectric plate l with a rectangular
interval 11 therebetween. The rectangular frame lO is made of a rigid (high longitudinal
modulus) material such as metal or plastic, and its strength and thickness are selected so as to be
optimal for water pressure and sound pressure level to be detected.
Next, a urethane resin mold or the like is applied to the upper and lower surfaces of the
piezoelectric plate 1 and the rectangular frame 10 to form a resin layer 12.12. The rectangular
frame lO uses a rigid (high longitudinal modulus) material such as metal or plastic, and its
strength and thickness are determined so as to be optimum for the water pressure and the
detected sound pressure level. The resin layer 12.12 is prevented from flowing into the
rectangular space 11, and the rectangular space 11 is used as an air layer 13 serving as a buffer
circumferential area. Thus, with this configuration, a piezoelectric transducer sheet is formed,
and even if pressure p2 is applied from the peripheral edge, it is buffered by the air fi 13 and the
effect does not reach the outer peripheral edge of the piezoelectric plate l. In order to confirm
this, the piezoelectric plate l is made 100 mm in length-59 WII in width-3 mm in thickness
(including the piezoelectric material 2 intestinal layer), and its characteristics are electrostatic
capacity 1173 P, F, tan δ = 5.9% When the gap 11 is set to one track, the one shown in FIG. 2 is
configured, and the wave receiving sensitivity of the present invention is −193 as compared
with the conventional configuration of FIG. 8 using the same piezoelectric plate l. , 9 dB and the
conventional one was -201 ° fidB. That is, it was found that in the present invention, the
receiving sensitivity was improved by 7.7 dB. Furthermore, as a result of sequentially applying a
pressure of up to 100 kg / crn '' to such a constitution and examining the receiving sensitivity
performance, it became as shown in FIG. 3, and it was found that stable sensitivity was obtained.
As shown in FIG. 4, the foam material layer 20 may be formed by filling a foam material such as
foam rubber in the rectangular space 11. In this configuration, the piezoelectric plate 1 may The
arrangement relationship of the form intervals 11 can be properly maintained, and the buffer
circumferential area around the piezoelectric plate 1 can be formed uniformly. In FIG. 5, a
plurality of interval holding claws 30 having a degree of protrusion equal to the width of the
rectangular interval 11 is formed on the inner peripheral surface of the rectangular frame 10. In
this configuration, the positional relationship between the piezoelectric plate 1 and the
rectangular space 11 can be properly maintained by the holding claws 30. Moreover, since the
holding claw 30 contacts the outer periphery of the piezoelectric plate 1 with its acute angle end,
pressure propagation in one surface direction is minute. The spacing holding claws 30 may
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protrude on the outer peripheral surface of the piezoelectric plate l, or may be provided on both
the outer peripheral surface of the piezoelectric plate l and the inner peripheral surface of the
rectangular frame 10 in a staggered manner or the like. You may In FIG. 6, a rectangular annular
metal flat plate 40 is provided above and below the rectangular interval 11. That is, in the case
where the flat plate 40 is not provided, as shown in FIG. 7, the resin layer 12.12 is sunk by the
pressure PI in the thickness direction acting on the upper and lower outer surfaces, It will
generate a surface direction force.
As a result, the sensitivity of the piezoelectric transducer sheet is reduced. However, the
depression of the resin layers 12 is prevented by the flat plate 40, and the adverse effect is
removed. The flat plate 40 is resin at the upper and lower positions of the rectangular interval
11. It may be embedded within 12.12. <Effects of the Invention> As the present invention has
clarified the pressure in the surface direction acting on the peripheral edge of the piezoelectric
plate as clarified by the above description, the constant g 31 can be seen in the reception. There
is an excellent effect that the value gh is improved as the upper limit is zero, the high sensitivity
can be generated, and the constant dh is increased and the transmission performance is
improved in transmission.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is an exploded perspective view of the piezoelectric plate 1 and the rectangular frame 10
used in the first embodiment of the present invention, FIG. 2 is a longitudinal side view of the
first embodiment, and FIG. Graph showing wave sensitivity performance, FIG. 4 is a longitudinal
sectional view of a part of a modification of the first embodiment, FIG. 5 is a perspective view of
the piezoelectric plate 1 and the rectangular frame 10 of the second embodiment, FIG. FIG. 7 is a
longitudinal side view of the third embodiment, FIG. 7 is a partial longitudinal side view without
the flat plate 40, and FIG. 8 is a longitudinal side view of a conventional example.
1; Piezoelectric plate 10; Rectangular frame ll: Rectangular spacing 12; Resin 13; Air W! 20:
Foam material layer 30; Spacing claw 40; Flat plate FIG. 2 FIG. 321 12 l FIG. 6 FIG. 7 FIG. 1148
FIG.
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