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JPH0448897

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DESCRIPTION JPH0448897
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic transducer used in water, and more particularly to the structure of an ultrasonic
transducer that ensures high insulation in water for a long period of time. 2. Description of the
Related Art Heretofore, in this type of ultrasonic transducer, it is common to excite or receive
ultrasonic waves using the respiration vibration of a cylindrical piezoelectric ceramic. FIG. 2 is a
partially broken front view showing a conventional ultrasonic transducer. In the figure, 1 is a
cylindrical piezoelectric ceramic, 2.3 is a disk-shaped spacer having an outer diameter
substantially the same as the outer diameter of the piezoelectric ceramic 1, and 4.5 is an outer
diameter substantially the same as the outer diameter of the piezoelectric ceramic 1 The two
open ends of the piezoelectric ceramic 1 are closed by the flange 4.5 via the spacer 2.3. Further,
as described above, when the both open ends of the piezoelectric ceramic 1 are closed, holes
communicating with each other are formed in the center portions of the spacer 2.3 and the
flanges 4 and 5. 6 is a bolt, and penetrates from the flange 5 side to the above-mentioned hole,
and tightens the nut 7 on the bolt 6 penetrating to the flange 4 side, so that the flange 4.5 is
pressed to both open ends of the piezoelectric ceramic 1 An air chamber is formed in an airtight
state inside. Reference numeral 8 denotes a cable as a signal line, the core of which is connected
to the electrode of the piezoelectric ceramic 1. Reference numeral 9 denotes a piezoelectric
porcelain 1 whose both ends are closed as described above, and a molding material which coats
the cable 8. The end of the cable 8 is covered by integrally coating one end side of the cable 8
and the whole piezoelectric porcelain 1. The piezoelectric ceramic 1 is fixed to the Here, as the
molding material 9 described above, since the ultrasonic transducer is often used in the ocean so
that the piezoelectric ceramic 1 is not broken due to an unavoidable artificial impact or the like,
the molding material is damaged There has been used a material which does not lose its function
and is not damaged due to wear or immersion to the surface of the piezoelectric ceramic 1. Also,
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adhesion with the cable 8 is emphasized so that the boundary between the mold material 9 and
the cable 8 does not peel off due to bending or temperature change and cause water immersion
from that portion. Therefore, as the material of the molding material 9, the degree of freedom of
choice is extremely small, and specifically, chloroprene rubber, urethane rubber, epoxy resin or
the like used as an outer cover of the cable 8 is used. The [Problems to be Solved by the
Invention] However, in the above-mentioned conventional ultrasonic transducer, although the
function is hardly impaired due to external factors, the specific resistance of the used molding
material is at most 1010 to 1013 Ω0, Moreover, since the water absorption rate is about 0.2 to
1.0% / 24 hr, when using the ultrasonic transducer for long periods in seawater, it will gradually
infiltrate the mold material without any external factor. In some cases, the water reaches the
cylindrical surface of the piezoelectric ceramic, and then enters the air chamber inside the
cylinder of the piezoelectric ceramic as moisture, thereby reducing the insulation of the
piezoelectric ceramic.
When the insulation of the piezoelectric ceramic is lowered, there is a problem that the applied
voltage at the time of the transmission excitation causes discharge breakdown and becomes
unusable. Even when used exclusively for receiving waves, the insulation resistance is parallel to
the capacitive output impedance of the piezoelectric ceramic if the insulation of the piezoelectric
ceramic is reduced, so the low frequency region is blocked by both of them. There is a problem
that it has frequency characteristics and can not receive an ultrasound signal of audible
frequency. The present invention has been made to solve such problems, and it is an object of the
present invention to provide an ultrasonic transducer having a high impact resistance and a low
water absorption property with a double structure of a molding material. [Means for Solving the
Problems] In order to achieve the above object, the present invention sandwiches both open ends
of a cylindrical piezoelectric ceramic with a circular flange having an outer diameter substantially
the same as the outer diameter of the piezoelectric ceramic. Also press the cable connected with
the electrodes of the piezoelectric ceramic! In the ultrasonic transducer, which is disposed on one
end side of the porcelain, and the entire piezoelectric ceramic and the end of the cable are
integrally covered with a molding material to form a watertight structure, the molding material is
used as the inner layer, with low water absorption and specific resistance. A double material that
covers the entire inner layer and the end of the cable with a high material that covers the entire
piezoelectric ceramic and that has excellent impact resistance and abrasion resistance as the
outer layer and excellent adhesion between the cable and the inner layer. The [Function] The
present invention having the above-described structure has a double structure in which the
molding material for covering the piezoelectric ceramic is used, and the inner layer is made of a
material having high specific resistance and low water absorption, and the outer layer has impact
resistance and wear resistance. It is intended to use a material which is excellent in the property
and in the adhesion between the cable and the inner layer. Therefore, according to this, the outer
layer is excellent in impact resistance and abrasion resistance, so it is strong against external
factors, and the inner layer is high in specific resistance and low in water absorption, so even if
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left in the sea for a long time The portion of the piezoelectric ceramic will not be flooded. An
embodiment will be described below with reference to the drawings. FIG. 1 is a partially broken
front view showing an embodiment of the present invention, in which 1 is a cylindrical
piezoelectric ceramic, and 2.3 is a disk-like spacer having an outer diameter substantially the
same as the outer diameter of the piezoelectric ceramic 1 , 4.5 is a disk-shaped flange having an
outer diameter substantially the same as the outer diameter of the piezoelectric ceramic 1 and
both open ends of the piezoelectric ceramic 1 are closed by the flange 4.5 through the spacer
2.3. ing. Further, as described above, when the both open ends of the piezoelectric ceramic 1 are
closed, holes communicating with each other are formed in the center portions of the spacer 2.3
and the flange 4.5. 6 is a bolt, and penetrates from the flange 5 side to the above-mentioned hole,
and tightens the nut 7 on the bolt 6 penetrating to the flange 4 side, so that the flange 4.5 is
pressed to both open ends of the piezoelectric ceramic 1 An air chamber is formed in an airtight
state inside.
Reference numeral 8 denotes a cable as a signal line, the core of which is connected to the
electrode of the piezoelectric ceramic 1. 10 is a molding material which coats the piezoelectric
ceramic 1 and the cable 8 whose both ends are closed as described above, and one end of the
cable 8 and the entire piezoelectric ceramic 1 are coated integrally, thereby the end of the cable
8 The piezoelectric ceramic 1 is fixed to the Here, the molding material 10 has a two-layer
structure consisting of an inner layer 10a and an outer layer 10b, and an ethylene propylene
rubber is used for the inner layer 10a. Since this ethylene propylene rubber has a specific
resistance of 10'5 Ω1 or more and a water absorption of 0.1% / 24 hr or less, even when an
ultrasonic transducer is used for long-term use in the sea, Sea water does not reach the portion of
the piezoelectric ceramic 1 through the inner layer 10a to reduce the insulation. Here, the
propylene-based rubber described above is insufficient in impact resistance and abrasion
resistance, and is artificially scratched or worn during transportation or installation work, and
thus is an ultrasonic transducer alone. Can not serve as the exterior of the Therefore, the outer
layer 10b is made of chlorobron rubber or urethane rubber, an epoxy resin or the like, and these
materials are excellent in impact resistance and abrasion resistance, and also with the surface of
the inner layer 10a and the cable 8. Excellent adhesion. Thereby, the outer layer 10b covers the
inner layer 10a and the cable 8 without peeling off, and protects the inner layer 10a and further
the piezoelectric ceramic 1 from damage and abrasion due to external factors. The material of
the inner layer is not limited to ethylene-propylene rubber, and any material having higher
specific resistance than conventional chlorobron rubber or urethane rubber, epoxy resin, etc.
may be used, and the specific resistance is 10 The effect is produced if "" Ω or more. Also, the
outer layer is not limited to the conventional chlorobron rubber, urethane rubber, epoxy resin,
etc., and has impact resistance and abrasion resistance equal to or higher than these materials,
and has high adhesion with the inner layer and cable. What is necessary. [Effects of the
Invention] As described above, according to the present invention, both open ends of the
cylindrical piezoelectric ceramic are sandwiched by a circular flange having an outer diameter
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substantially the same as the outer diameter of the piezoelectric ceramic, and an electrode of the
piezoelectric ceramic An ultrasonic transducer with a watertight structure in which a cable
connected to the cable is disposed on one end side of the piezoelectric ceramic, the entire
piezoelectric ceramic and the end of the cable are integrally covered with a molding material, and
the molding material is used as an inner layer. A material with low resistance and high specific
resistance that covers the entire piezoelectric ceramic, is excellent in impact resistance and
abrasion resistance as an outer layer, and has excellent adhesion between the cable and the inner
layer, and covers the entire inner layer and cable It has a double structure covering the end.
Therefore, according to this, since the outer layer is excellent in impact resistance and abrasion
resistance, there is an effect that the ultrasonic transducer is not damaged or worn out by an
external factor. In addition, since the inner layer has high specific resistance and low water
absorption, even if it is left in the sea for a long time, it does not flood the part of the
piezoelectric ceramic to reduce the insulation of the piezoelectric ceramic, thereby transmitting
waves. Cause discharge breakdown due to the applied voltage. This has the effect that the
ultrasonic transducer can not be disabled due to a failure such as an inability to receive
ultrasonic signals at low audible frequencies.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a partially cutaway front view showing one embodiment of the present invention, and
FIG. 2 is a partially broken pressure surface view showing a conventional example.
1 · 8 · 10 · 0a 0b · Piezoelectric ceramic · Cable · molding material · inner layer · outer layer
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