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JPS5750198

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DESCRIPTION JPS5750198
Description 1, title of the invention
Underwater transducer
3. Detailed Description of the Invention The present invention relates to an underwater
transducer using a flexible piezoelectric material. Conventionally, this type of underwater
transducer uses a piezoelectric ceramic or magnetostrictive vibrator, but these vibrators are
likely to reflect sound because the acoustic impedance density is much different from that of
water, and The weight is also heavy. In addition, there is an unavoidable disadvantage that
equipment for forming is required at the time of production. For example, when the ratio of the
acoustic impedance density of the piezoelectric ceramic type vibrator to that of water is as large
as 15 or more and the water wave receiver is used and the above vibrator is used, the reflectance
of the sound strength is 80% or more Can be mentioned. The present invention eliminates the
reflection of sound generated due to acoustic impedance density mismatch, and simplifies
manufacture, transportation, assembly, and weight reduction by using a piezoelectric body for
the transducer of the underwater transducer. It is an object of the present invention to provide an
advantageous underwater transducer. In order to achieve such an object, the underwater
transducer according to the present invention has a structure in which electrodes are provided
on the inner and outer surfaces of the piezoelectric body, and both end surfaces or the entire
outer surface are covered with an acoustically transparent insulating material. It is characterized
by Next, embodiments of the present invention will be described with reference to the drawings.
The piezoelectric body is capable of converting not only sound to electricity but also electricity to
sound, and has so-called reversibility. However, the case of conversion from sound to electricity
EndPage: 1 conversion will be described. FIG. 1 is a structural view of a transducer according to
the present invention, in which a weir is a cross-sectional view taken at right angles to the axial
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direction, and (Bl is a cross-sectional view showing a part of the piezoelectric body in the axial
direction. The transducer according to the present invention is a rod-like piezoelectric body 1
(hereinafter simply referred to as the piezoelectric body 1) which is made of a polymer
piezoelectric material or a composite piezoelectric material of a polymer material and a fine
powder of a piezoelectric ceramic material and polarized in the radial direction. Electrodes 2.3
are provided on the inner and outer surfaces of each of the electrodes and connected to
terminals 2: 3 by lead wires, and the entire surface of the piezoelectric body 1 is covered with an
acoustically transparent insulating material 4 so as to leave no air bubbles or air layers. It is. The
principle of operation will now be described. The acoustic impedance density (1, 6 × 10 to 23 ×
10 (gr / cffl-s)) of the piezoelectric body is very similar to that of water (1, 5 × 10S (gr // cf-s)).
Therefore, the incoming sound is incident on the piezoelectric body with little reflection. Now, it
is assumed that the sound pressure distribution at a certain point in time of the sound incident in
the axial direction of the piezoelectric body is in the state of FIG. Where X is the axial position
and p is the sound pressure. Now, assuming that the length of the piezoelectric body is l, the
pressure in the piezoelectric body is pI. This means that the length l of the piezoelectric body
changes depending on the sound pressure, and it can be seen that an output voltage proportional
to pj is generated between the electrodes 2 and 3 and between the terminals 2131.
Although the above-described piezoelectric body has been described as having a rod-like shape,
the same operation can be carried out with a pipe-like piezoelectric body as shown in FIG. 3
(person) and (B), and in this case the pipe is hard. It may be a flexible material. Moreover,
although the thing of the structure which the whole outer surface contact | connects in water
was demonstrated above, the structure which interrupt | blocks the whole surface or one part
other than an end surface acoustically may be sufficient. The number of piezoelectric bodies need
not be one, and plural piezoelectric bodies may be connected acoustically in parallel in the axial
direction. Furthermore, the diameters of the piezoelectric bodies do not have to be the same, and
they have different diameters. A plurality of piezoelectric members may be used. As described
above, the present invention can be easily manufactured by cutting the piezoelectric body to a
desired length and covering the end face or the entire surface with an acoustically transparent
insulating material, and from the structure, it can It is possible to obtain a low-loss underwater
transducer which is sufficiently durable and light in weight as compared to a conventional
vibrator and has less reflection of sound.
4. Brief description of the drawings FIGS. 1 (A) and 1 (B) show the first embodiment of the
present invention in which (A) is a cross-sectional view perpendicular to the axial direction, and
(B) is a partial cut in the axial direction. 2A and 2B are explanatory diagrams of the present
invention, in which FIG. 2A is a sound pressure distribution map at the time of the vertical
incident from the axial direction, and FIG. 2B is a center at the axial direction Fig. 3 body) + (B)
shows a second embodiment of the present invention. (Λ) is a cross-sectional view perpendicular
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to the axial direction (B) is a cross-sectional view with a part cut in the axial direction It is. 1:
Piezoelectric body 2: External electrode 21: External electrode terminal. 3: Internal electrode, 31:
Internal electrode terminal, 4: Insulating coating. Attorney Attorney Attorney Uchihara EndPage:
2
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