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JPS6199499

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DESCRIPTION JPS6199499
[0001]
<Industrial Application> In the present invention, whether it is in a hydrophone for seafloor
seismic survey or fish school detection, or in a cleaning solution of ultrasonic cleaning
equipment? ’Ff1! The present invention relates to an underwater piezoelectric wavereceiving sheet that is suitably used as a stator. Prior art polyvinylidene fluoride, polyvinylidene
fluoride, polyvinylidene chloride, poly 1! A piezoelectric organic ceramic composite formed by
mixing lead zirconate titanate, lead titanate and other ferroelectric ceramic particles in a
piezoelectric organic substance of synthetic phenyl or nylon '): or an organic substance of
synthetic rubber or synthetic resin, Compared with a general sintered negative piezoelectric
ceramic material, its acoustic impedance is similar to the acoustic impedance of water. Therefore,
using this as a pressure transducer, acoustic waves propagating in water can be efficiently used.
There is an advantage of receiving waves and increasing sensitivity. Therefore, as shown in Fig.
4, as shown in Fig. 4, the electrode sheet b), c is provided on the upper and lower surfaces of the
piezoelectric sheet a) made of the piezoelectric material, and a predetermined DC voltage is
applied between the electrode sheet b, c C) a) Polarized in the thickness direction and immersed
in water to extract an output signal from between the electrode sheet b and the conductive
coating C to receive an acoustic wave propagating in the water. There is a wave sheet. Problems
to be solved by the light 15I> By the way, since the piezoelectric sheet according to the Itij
configuration is flexible, pressure 1 other than the acoustic wave, for example, a draw flow stress
of a blow-off weir or a flow of wood, a bending stress by them etc. These mechanical stresses
distort in the surface direction of the piezoelectric sheet a (direction perpendicular to the
polarization axis) to generate electric charges or voltages, which are superimposed on the
acoustic wave as a noise signal, and S / There is a disadvantage of reducing the N ratio. An object
of the present invention is to provide an underwater piezoelectric wave-receiving sheet which
can prevent influences other than acoustic waves to eliminate the drawbacks of the conventional
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configuration. In the present invention, a first piezoelectric sheet and a second piezoelectric sheet
made of a piezoelectric organic ceramic composite are laminated, and either of the above
piezoelectric sheets is compared to the other piezoelectric sheet. And the Iv, load or voltage
generated by the stress acting in the surface direction are almost equal, and the charge generated
from the first piezoelectric sheet and the second piezoelectric sheet Or, it comprises a connection
means for taking out the difference in voltage. Effect> The noise cancellation principle in the
present invention is as follows. Now, assuming that the hydrophone constant of one piezoelectric
sheet is l d h and the piezoelectric constant is' d 33 and 'd: l I respectively, the relationship of' d h
= 'd 33 + 2' d: 11 is obtained. is there.
Also, regarding the other piezoelectric sheet, assuming that the constants are “d h,” “d 33,”
and “d 3 +,” there is a relationship of “d h = 2 d: 13 +2 ′ d 31” between them. By the way,
the piezoelectric constant 'd33,' d1: 1 represents an electric conversion rate in response to the
pressure in the thickness direction (polarization direction), and the acoustic wave signal is a
charge based on this constant. Further, the pressure i mini number 1d: II, "d: lI represents an
electrical conversion ratio responsive to pressure in the surface direction (direction
perpendicular to the polarization axis), and the noise signal is a charge based on this constant.
Therefore, the difference between 'd 3: l and' d 33 is taken out by setting l d h − ′ d h field O...
′ D 31 − ′ d: l I = O − + @ from these relations, The noise signal is removed and only the
signal by the acoustic wave is taken out. Therefore, in the present invention, the material of one
piezoelectric sheet is selected from a piezoelectric organic ceraminic composite having a large
hydro 7-on constant 1 d h, such as lead titanate (P bTi 03) mixed with an organic substance such
as rubber and resin. use. Incidentally, a material obtained by mixing PbTi0z and silicone rubber
at a ratio of 7:10 is 1 dh = 35 x-+ 210 (C / N). Also, select a piezoelectric composite material with
a small hydrophone constant h2dh, such as zircon M · f tough M lead (P b (Z r IIT i) 01) mixed
with an organic substance such as di-rubber, vA oil, etc. use. Incidentally, a material obtained by
mixing Pb (ZrQTi) 03 and silicone rubber at a ratio of 7 · lO is 2d h = 8 × 10 (C: / N). By making
such a piezoelectric sheet of such a size as a piezoelectric material having a larger hydrophone
constant than that of the other piezoelectric sheet, it is possible to satisfy the above-mentioned
relational expression (1). On the other hand, these piezoelectric materials have different
piezoelectric constants 'd 31 and' d 31, and materials having a large hydrophone constant 1d h
have small 'd' I +, for example, P b Ti O z materials compounded at the above specific ratio In the
case of 'd 31 = −5 × I Q (C / N), in the case of the same <Pb (Ti̶Zr) O: l material, it differs from
“dz + = − 25 × I O (C / N). Therefore, in order to satisfy the above-mentioned relational
expression f in the present invention, the piezoelectric constant t12d3 + kaPbTiO: I of the
material n1 is 1 d: n with respect to the material Pb (Ti-Zr) O: 1. If they are equal to each other, it
is necessary to lower the polarization voltage to reduce 2d31.
Since the d: lI (7) decrease of the Pb (Ti-Zr) 03 material simultaneously decreases by 2 d h, the
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2
difference with the Id h of the P bT i 03 material becomes larger and the effect of optimizing the
sensitivity is achieved. There is also. Although the noise cancellation principle based on the
charge Q generated in the piezoelectric sheet has been described above, even if the charge Q is
different only by considering the capacitance C from the relational expression of V = Q / C even
with 1 generated voltage V Of course, it can be explained similarly. The present invention is
based on the noise cancellation principle, and when the piezoelectric sheet is subjected to stress
in the surface direction by tension or bending, charges (or voltages) generated in the second
piezoelectric sheet and the first piezoelectric sheet based on the stress. ) Equal and disappear by
electrical subtraction. For this reason, when an acoustic wave is generated in water, it becomes
possible to take out only the charge (or voltage) based on the difference between the hydrophone
constants of the two piezoelectric sheets from the connection means. EXAMPLE Referring to FIG.
1.2, 1.2 are rectangular second and second piezoelectric sheets made of piezoelectric rubber or
the like, and polarized in the same direction so that, for example, the upper surface side is
negative and the lower surface side is positive. It is done. The piezoelectric sheet 1.2 is laminated
via the electrode sheet 3, the electrode sheet 4 is on the upper surface of the first piezoelectric
sheet 1 in the upper part, and the electrode sheet 5 is similarly on the lower surface of the
second piezoelectric sheet 2 in the lower part. It is provided. The piezoelectric wave-receiving
sheet having the above-mentioned configuration requires means such as covering with the
insulating coating 6 in order to insulate the electrode sheet 3 and the electrode sheet 4.5 from
each other. As described above, one of the first piezoelectric sheet l and the second piezoelectric
sheet 2, for example, the first piezoelectric sheet 1, is formed of, for example, a lead titanate
(PbTiO: +) material having a large hydrophone constant. The second piezoelectric sheet 2 is
formed of a normal Pb (Tj 壷 Zr) 03 based material. The rectangular piezoelectric wave receiving
sheet thus formed is electrically connected by the electrode sheet 4 serving as the negative
electrode of the first piezoelectric sheet l, the electrode sheet 5 serving as the positive electrode
of the second piezoelectric sheet 2, and the wedge reed 10 , And the electrode sheet 3 interposed
between the positive electrode surface of the first piezoelectric sheet 1 and the negative
electrode surface of the second piezoelectric sheet 2 by the lead wire 1). The output terminal B is
an end of the output terminal B, and an output signal is taken out from between the output
terminals A and B. The output terminal A is on the ground side. Explaining the operation of the
above-mentioned embodiment, when stress in the surface direction is generated in the
piezoelectric wave-receiving sheet by them etc., charges (or voltages) are generated in the
piezoelectric sheet 111).
By the way, since d ′ + 1 of the first piezoelectric sheet l and the second piezoelectric sheet 2 is
substantially equal, the amount of charge (or voltage) generated on the piezoelectric sheets 1 and
2 by the stress in the surface direction is as follows: Almost the same, as described above, the
negative electrode of the first piezoelectric sheet 1 and the positive electrode of the second
piezoelectric sheet 2 are the lead wire l. And the positive electrode of the first piezoelectric sheet
1 and the negative electrode of the second piezoelectric sheet 2 are short-circuited through the
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electrode sheet 3 and thus depolarize each other, and eventually between the output terminals A
and B There is no potential difference (or voltage difference) due to their external stress, while
the influence of the NW wave acts on the entire surface of the sheet, but the first piezoelectric
sheet 1 is a hydrophone. The sensitivity to acoustic waves is higher than that of the second
piezoelectric sheet 2 because it is formed of a material with a large constant, so that when an M F
wave is generated in the liquid, the output corresponding to the sensitivity difference is the
output terminal A, It occurs between B. Therefore, as described above, since the generation of the
potential due to their external stress is eliminated, only the electrical signal corresponding to the
acoustic wave is extracted between the terminals A and B. For this reason, only the f harmonic
can be received without being affected by the curvature. The piezoelectric receiving sheet having
the above-described configuration can be scattered at an appropriate place in the water, and the
sound 17P wave at each position can be detected to detect the dispersion of the acoustic wave in
the water. FIG. 3 shows an embodiment in which the polarization directions of the first
piezoelectric sheet l and the second piezoelectric sheet 2 are reversed. In this case, the electrode
sheet 7a in contact with the upper surface of the second piezoelectric sheet 2 and the first
piezoelectric sheet ') [Polar sea) 7b in contact with the lower surface of the sheet 1] is insulated
by the insulating sheet 8 and the electrode sheet 7a acting as the negative electrode of the
second sheet 1 is the positive electrode of the second piezoelectric sheet 2 The electrode sheet 4
to be the positive electrode of the first piezoelectric sheet 1 is connected to the electrode sheet 1
b to be the negative electrode of the second piezoelectric sheet 2 and to a large extent electrically
connected. Also, in order to prevent any other connection, for example, the insulation coating m6
is applied to the entire circumference of the aforementioned pressure receiving sort. The other
effects and effects are the same as in the above embodiment and will be omitted. In place of the
connection means shown in each of the above embodiments, the charge generated from one
sheet may be inverted, and may be combined with the charge generated from the other
piezoelectric sheet to take out the difference . The shape of the JL 屯 received wave depends on
the application: species, · · ·,! ! 'Can be chosen, the shape of a disc can be considered. <Effects of
the Invention> As the present invention makes clear from the above description, when the
pressure-sensitive receiving sheet is bent by the external pressure, the charges generated in the
first piezoelectric sheet 1 and the second piezoelectric sheet 2 are Since they cancel each other
out so that only the charge corresponding to the acoustic wave generated in the pressure-C sheet
formed by the material having a large hydrophone constant can be taken out from the output
terminal There is an excellent effect such that the influence can be removed as much as possible
and extracted, and the S / N ratio of the output of the piezoelectric sheet can be significantly
improved.
[0002]
Brief description of the drawings
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[0003]
FIG. 1 is a perspective view of a first embodiment of the present invention, FIG. 2 is a longitudinal
side view of the same, FIG. 3 is a longitudinal side view of a second embodiment, and FIG. .
1 ... 1st piezoelectric sheet 2 ... 2nd piezoelectric sheet 3-5, 7a, 7b ... electrode sheet A, B ... output
terminal
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