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JPS62245800

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DESCRIPTION JPS62245800
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
support structure of a piezoelectric vibrator of a pressure balance type underwater transducer
used for position measurement or distance measurement in water. [Background Art]
Conventionally, various support structures of this type have been put into practice, and there are,
for example, those shown in FIG. FIG. 4 is a cross-sectional view showing a conventional support
structure disclosed by Japanese Patent Application Laid-Open No. 60-226299. In FIG. 4, 1 is a
circular substrate, this substrate 1 has a cable 2 fixed at its center, and a bottomed cylindrical
rubber boot 4 is attached to the outer wall with 7 flanges 3 by tightening the band 5 There is. A
piezoelectric vibrator 6 transmits and receives ultrasonic waves. The piezoelectric vibrator 6 is
supported in the rubber boot 4 by a support rod T such as a bolt fixed at the center of the
substrate 1. FIG. 5 is a perspective view showing the details of this support structure. The
piezoelectric vibrator 6 is formed in a cylindrical shape by an outer wall 6a and an inner wall 6b,
and is held by disk-shaped metal caps 8a and 8b fixed to the support rod I. In FIG. 4, 9 is oil filled
in the rubber boot 4 and the piezoelectric vibrator 6 in order to maintain the hydrostatic
pressure balance. Next, the operation of the transducer provided with the piezoelectric vibrator 6
of the supporting structure will be described with reference to FIG. When transmitting ultrasonic
waves with this transducer, the radiation wave from the outer wall 6a of the piezoelectric
vibrator 6 and the radiation wave from the inner wall 6b are combined, and this combined wave
is transmitted as a measurement signal wave. Ru. In addition, when the ultrasonic wave is
received by the transducer, the incident wave on the outer wall 6a of the piezoelectric vibrator 6
and the incident wave on the inner wall 6b are synthesized in the reverse of the case of the
transmission wave. The composite wave is received as a measurement signal wave. FIG. 4 is a
figure which shows the characteristic of the vertical directivity by the said transducer. In the
piezoelectric vibrator 6 of the support structure, the level of the radiation wave or the incident
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wave from the inner side wall 6b is large, so that the directivity phenomenon occurs in the
direction of 270 ° to 0 ° to 90 °, and constant The directivity of the level was not obtained.
[Problem to be Solved by the Invention] Therefore, in the case of mounting the transducer on the
housing and measuring the distance or position in water in the support structure, the
transmission 2 and the reception in the direction of low directivity. There is a problem that the
level decreases and measurement becomes difficult. Therefore, the present invention has been
made focusing on the above-mentioned problems, and an object thereof is to provide an
underwater transducer whose measurement accuracy is improved by making the level of the
vertical directivity of the transducer constant. An object of the present invention is to provide a
support structure for a piezoelectric vibrator.
[Problems to be Solved by the Invention] The structure of the present invention for achieving the
above object is a support structure for a piezoelectric vibrator of an underwater transducer,
wherein the metal cap has the same outer diameter as the piezoelectric vibrator, and the metal
The gist of the present invention is to have an axial length which makes the sound pressure
transmittance of the cap be 0.3 or less at the lower limit of the use frequency. [Operation] When
transmitting and receiving ultrasonic waves with a transducer provided with the piezoelectric
vibrator of the support structure, the sound pressure transmittance of the metal cap is set to 0 °
3 or less, so the inner side wall of the piezoelectric vibrator The level of the radiation or incident
wave from the Therefore, it is possible to eliminate the synthesis of radiation waves or incident
waves from the outer wall and the inner wall of the piezoelectric vibrator. As a result, the level of
the vertical directivity (270 ° to 0 ° to 90 °) of the transducer becomes constant, and the
above problem is solved. Embodiments of the present invention will be described in detail with
reference to the drawings. FIG. 2 is a longitudinal sectional view showing a support structure of a
piezoelectric vibrator according to an embodiment of the present invention. In FIG. 2, reference
numeral 11 denotes a cylindrical piezoelectric vibrator, and metal caps 13 a and 13 b are
attached to both ends of the piezoelectric vibrator 11 via support rods 12. FIG. 1 is a perspective
view showing the details of the metal camps 13a and 13b. As shown in FIG. 1, the metal cap 13a.
13 b has a cylindrical shape, has the same outer diameter d as the piezoelectric vibrator 11, and
is formed flush with the outer wall 11 a of the piezoelectric vibrator 11. The metal caps 11a and
11b have an axial length t, and the length t is such that the sound pressure transmittance α of
the metal caps 11a and 11b is 0.3 or less at the lower limit of the use frequency in the following
equation The value is set to be Here, Zl is the specific acoustic impedance of the oil 14, Z2 is the
specific acoustic impedance of the metal cap 13a # 13b, and K2 is the metal cap 13a. It is a wave
number of 13b. Reference numeral 11 b denotes an inner @ wall of the piezoelectric vibrator 11.
Next, the operation of the transducer provided with the piezoelectric vibrator 11 of the
supporting structure will be described with reference to FIG. When position measurement in
water is performed, when ultrasonic waves are transmitted by the transducer, radiation waves
are respectively propagated from the outer wall 11 a and the inner wall 11 b of the piezoelectric
vibrator 11. The metal cap 13 a is a radiation wave transmitted from the inner side wall 11 b of
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the piezoelectric vibrator 11 through sound pressure. The sound pressure transmittance α of 13
b is set to 0.3 or less at the lower limit of the operating frequency by the support structure.
Therefore, the radiation wave transmitted through the sound pressure from the inner side wall
11 b of the piezoelectric vibrator 11 can be suppressed to an extremely small level.
As a result, the radiation waves from the inner side wall 11b are not synthesized, and only the
radiation waves from the outer side wall 11a are propagated as measurement signals, thus
eliminating the directivity degradation phenomenon. FIG. 3 is a diagram showing the vertical
directivity characteristic of the transducer according to this embodiment. As apparent from this
figure, in the range of 270 ° to 0 ° to 90 °, the Δ difference is suppressed to 6 dB or less, and
directivity of a nearly constant transmission level can be obtained. The operation in the case of
receiving the reflected sound is the same as in the case of the transmission of the ultrasonic
wave, so the description thereof will be omitted. [Effects of the Invention] As described above,
according to the present invention, in the supporting structure of the piezoelectric vibrator of the
underwater transducer, the both ends of the piezoelectric vibrator have a length for reducing the
radiation wave or incident wave from the inner side wall of the piezoelectric vibrator. Since the
metal cap having the height and the outer diameter is provided, it is possible to eliminate the
synthesis of the radiation waves from the outer wall and the inner wall of the piezoelectric
vibrator or the synthesis of the incident waves. Therefore, the vertical directivity level of the
transducer can be made substantially constant in the range of 270 ° to 00 ° to 90 °. As a
result, when performing position or distance measurement, it is possible to measure the drop of
the transmit / receive level. There is no problem that the direction in which the direction
becomes difficult arises, and the effect of improving the measurement accuracy can be obtained.
[0002]
Brief description of the drawings
[0003]
1 is a perspective view showing the details of the support structure of the piezoelectric vibrator
according to the embodiment of the present invention, FIG. 2 is a longitudinal sectional view
showing the outline of the support structure, and FIG. 3 is the vertical directivity in this
embodiment FIG. 4 is a longitudinal sectional view showing an outline of a conventional support
structure, FIG. 5 is a perspective view showing details of the conventional support structure, and
FIG. 6 is a vertical directivity in the conventional example. It is explanatory drawing which shows
a characteristic.
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11 · · · Piezoelectric vibrator 11 & · · · outer wall 11b · · · inner wall 12 · · · support rod 13a, 13b · ·
· · metal cap 14 · · · Patent applicants Oil patent attorney Oki Electric Industry Co., Ltd. Kinkura
Tsuyoshi Figure showing the characteristics of two examples-3 Detailed drawings showing the
conventional example of the country 5
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