JPH0287798

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DESCRIPTION JPH0287798
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
vibration noise suppression structure for an underwater ultrasonic wave receiver. (Prior Art)
Conventionally, as a technique in such a field, for example, there are those shown below. FIG. 3 is
a cross-sectional view showing one structural example of the wave receiver, wherein 11 is a mold
resin, 12 is a cylindrical piezoelectric element, 13 is a buffer rubber, 14 is a support fitting, 15 is
a cable, and 16 is a fitting. Be done. In the underwater ultrasonic wave receiver configured as
described above, the sound wave generated in water is received by the cylindrical piezoelectric
element 12 through the mold resin 11, and the sound pressure is converted into a voltage and
the d111 is determined by the external device. Is done. (Problems to be Solved by the Invention)
However, in the wave receiver of the above configuration, the unnecessary vibration transmitted
to the mounting bracket 16 is also transmitted to the cylindrical piezoelectric element of the
wave receiving portion, and is simultaneously measured as sound wave as vibration noise There
is a drawback that it is impossible to measure only sound waves with high accuracy. Here, the
vibration noise means that the cylindrical piezoelectric element is subjected to vibration from the
outside to be compressed and pulled in the direction of the vibration, thereby generating a
voltage in the cylindrical piezoelectric element. An object of the present invention is to remove
the deterioration in accuracy of sound measurement due to the vibration noise described above,
and to provide a receiver excellent in the suppression effect of the vibration noise. (Means for
Solving the Problems) In the present invention, in order to solve the above-mentioned problems,
a plurality of cylindrical piezoelectric elements are arranged symmetrically with respect to the
mounting portion of the neutral plate, and the mounting portion of the neutral plate The direct
attachment is supported by metal fittings, and the entire receiver is resin-molded. (Operation)
According to the present invention, as described above, the plurality of cylindrical piezoelectric
elements are arranged symmetrically with respect to the mounting portion of the neutral plate,
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and the neutral plate mounting portion is directly supported by the mounting bracket. Because
the vibration applied to the mounting bracket is directly applied to the neutral plate, the
mounting bracket and the neutral plate vibrate in the same manner. For example, when an
upward vibration is applied, the cylindrical piezoelectric element attached downward of the
neutral plate has a tensile force (negative In addition, a cylindrical piezoelectric element mounted
in the upper direction of the neutral plate generates a force (positive voltage) in the compression
direction. Therefore, when the outputs of the cylindrical piezoelectric elements are respectively
connected in parallel, the outputs become a sum of positive and negative voltages, which cancel
each other out and act to suppress vibration noise. It goes without saying that the same action
occurs when downward vibration is applied. Embodiments of the present invention will be
described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view of an underwater ultrasonic wave receiver showing an
embodiment of the present invention, and FIG. 2 is a vibration noise output / frequency
characteristic diagram. In FIG. 1, 1 is a mold resin, 2 is a cylindrical piezoelectric element, 3 is a
buffer rubber, 4 is a neutral plate, 5 is a cable, 6 is a mounting bracket, 7 is a cylindrical
piezoelectric element, and 8 is a screw. The neutral plate attachment is a screw. The cylindrical
piezoelectric element 2 is directly fixed to the neutral plate 4 in a vertically symmetrical manner
via the buffer rubber 3 with screws 7. The positive and negative electrodes (not shown) of the
cylindrical piezoelectric element 2 are connected in parallel and connected to the cable 5. On the
other hand, a neutral plate 4 made of a material 1 having high rigidity, for example, a metal
material 9 reinforced fiber plastic or the like, is attached to the attachment fitting 6 with a
plurality of attachment screws 8 at a central attachment portion. Further, the neutral plate 4 is
molded with the mold resin 1 including the cylindrical piezoelectric element 2 except for the
portion in contact with the mounting bracket 6. Accordingly, the mounting fitting 6 directly
contacts the neutral plate 4. The neutral plate 4 vibrates in the same manner as the mounting
bracket 6 as the mounting bracket 6 vibrating in this manner directly supports the neutral plate
4. When the cylindrical piezoelectric element 2 mounted opposite to the neutral plate 4 is
subjected to upward vibration, the cylindrical piezoelectric element 2 mounted below the neutral
plate 4 has a force (negative The cylindrical piezoelectric element 2 mounted above the neutral
plate 4 generates a force (positive voltage) in the compression direction. Therefore, the outputs
obtained by connecting the outputs of the cylindrical piezoelectric element 2 in parallel are equal
to each other as the addition of the positive voltage and the negative voltage, and cancel each
other to suppress the vibration noise. This is the same even when downward vibration is applied.
FIG. 2 is a diagram showing vibration noise output voltage-frequency characteristics according to
the present invention, wherein the solid line in the figure is the data of the present invention and
the broken line is the data of the prior art. For each data, attach the bracket to the vibrator, excite
the bracket, and divide the output voltage (vl) of the receiver by the vibration acceleration output
voltage (V) of the vibrator (V1 / vo) The decibel display value of is taken on the vertical axis, and
the frequency f is taken on the horizontal axis. In this characteristic chart, a peak is seen in a
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frequency band that is both a solid line and a broken line, but this peak is a resonance in a state
in which the mounting bracket 6 and the receiver are connected, rigidity of the mounting bracket
and reception It is possible to easily remove the operating frequency band of the receiver by
changing the weight of the receiver. (Effects of the Invention) As described above in detail,
according to the present invention, the neutral plate on which the cylindrical piezoelectric
element is mounted opposite to the vibrating mounting member is directly supported, and the
output of the cylindrical piezoelectric element The outputs of each connected in parallel cancel
each other as positive voltage and addition of negative voltage, and suppress vibration noise of
10 dB to 20 dB or more in the operating frequency band as can be seen from FIG. effective.
In addition, vibration noise can be suppressed regardless of the vibration of the attachment, and
it is possible to accurately measure the sound wave, which is the object of the present invention.
[0002]
Brief description of the drawings
[0003]
1 is a sectional view of the underwater ultrasonic wave receiver according to the present
invention, FIG. 2 is a vibration noise output-frequency characteristic showing the characteristics
of the present invention, and FIG. 3 is a sectional view of a conventional underwater ultrasonic
wave receiver. is there.
In the figure, l: mold resin, 2: cylindrical piezoelectric element, 3: buffer rubber, 4: neutral plate,
5: cable, 6: mounting bracket, 7, 8 · · Installation Neso. Ebietsu 5 sound wave dogo sea figure
figure 1 figure 2 of this invention
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