JPH0638395

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DESCRIPTION JPH0638395
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
directional acoustic transducer for underwater acoustics, and in particular, a directional
transducer that can be used in a wide measurement frequency range as a standard device for
measuring the sensitivity of the transducer. About
[0002]
2. Description of the Related Art As a method of measuring the sensitivity of underwater acoustic
transmitters and receivers, it is possible to transmit between an object to be measured and a
standard whose transmitter sensitivity or receiver sensitivity is known. There is a method of
measuring wave or wave reception and converting the wave transmission sensitivity or wave
reception sensitivity of the object to be measured from the sensitivity of the standard. This
measurement method is generally performed in the sea and lakes, but at high frequencies it is
possible to measure in a water tank. In these measurements, the reflected wave from the water
surface, the tank wall, etc. and the acoustic noise coming from the surroundings should be
negligible compared to the direct wave. Therefore, in order to avoid reflected waves and ambient
noise, it is desirable that at least the standard products have appropriate directivity.
[0003]
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FIG. 2 is a sectional view showing a conventional directional transducer, and shows an
underwater transducer used as a standard product. In the figure, reference numeral 1 denotes a
piezoelectric vibrator as an electroacoustic transducer. The piezoelectric vibrator 1 is generally a
disk-shaped piezoelectric vibrator made of piezoelectric ceramics, for example, PZT (lead titanate,
zirconate), is polarized in the thickness direction of the disk, and is positive and negative on both
sides of the disk. Electrodes are formed. A two-core waterproof cable 2 is connected to each of
the positive and negative electrodes of the piezoelectric vibrator 1, and a waterproof rubber 3
molded to prevent exposure of the conductive parts of the piezoelectric vibrator 1 and the
waterproof cable 2.
[0004]
The directional transducer according to this configuration utilizes the thickness vibration mode
of the disk of the piezoelectric vibrator 1 and has an angle φ 1/2 at which the sensitivity is
reduced to one half of the width of the main pole. Assuming that the wavelength λ and the
diameter of the disk are d, for example, when λ / d = 1.4, it becomes a directional transducer
with an angle of φ1 / 230 °.
[0005]
However, in the directional transducer of the above configuration, when the measurement
frequency range is wide, the directivity of the standard product is sharpened at high frequency,
and is made to face the object to be measured. At low frequencies, the width of the main pole of
directivity widens and is susceptible to noise.
For this reason, it was necessary to replace the standard with different directivity according to
the frequency. For example, if d is 15 mm, φ1 / 2 will be 45 degrees to 14 degrees in the
measurement frequency range of 100 kHz to 300 kHz, and the directivity will be appropriate,
but if the measurement frequency range is 50 kHz to 600 kHz, 90 degrees in 50 kHz However,
the sensitivity does not decrease to 1⁄2, and 1/21/2 becomes 7 degrees at 600 kHz, which
makes it difficult to measure a wide frequency range.
[0006]
In the present invention, when the measurement frequency range is wide, the directivity becomes
sharp, and the alignment to face the object to be measured becomes difficult, the width of the
main pole of directivity widens at low frequencies, and reflected waves and In order to eliminate
problems such as being susceptible to ambient noise, at least one of the positive electrode and
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the negative electrode provided on both sides of the piezoelectric polymer is coaxially divided,
and the divided electrodes are separated. It is an object of the present invention to provide an
excellent apparatus capable of measuring a wide range of measurement frequencies with one
standard device by selecting.
[0007]
SUMMARY OF THE INVENTION A directional transducer according to the present invention uses
a piezoelectric polymer as an acoustic transducer, and positive electrodes provided on both sides
of the piezoelectric polymer. And at least one of the negative electrodes is coaxially divided and
configured, and the divided electrodes are arbitrarily selected according to the measurement
frequency.
[0008]
The present invention makes it possible to eliminate the need to replace the standard for a wide
range of measurement frequencies, while suppressing the effects of noise and facilitating the
alignment.
[0009]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing
an embodiment of a directional transducer according to the present invention.
In the figure, 4 is a piezoelectric polymer as an electroacoustic transducer, and it is formed, for
example, in a circle with a diameter of 30 mm.
Generally as this piezoelectric polymer 4, PVDF (polyvinylidene fluoride), P (VDF-TrFE)
(vinylidene fluoride trifluoro ethylene copolymer), P (VDCN-VAC) (vinylidene cyanide-vinyl
acetate) Copolymers etc. are known.
5a, 5b and 5c are divided positive electrodes formed by being divided on one side of the
piezoelectric polymer 4, 6 is a common negative electrode formed on the other side of the
piezoelectric polymer 4, and 7 is this divided A 4-core waterproof cable connected to each of the
positive electrodes 5a, 5b and 5c and the common negative electrode 6 is an output of 3
channels. 8 is a molded waterproof rubber for waterproofing.
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[0010]
The divided positive electrodes 5a, 5b and 5c and the common negative electrode 6 are formed
by deposition of Al or Ni or bonding of a Cu foil, and the divided positive electrodes 5a, 5b and
5c have the same center, for example, Divided into a circle with a diameter of 15 mm and 7.5
mm with a slight width
[0011]
Next, in the case of measurement using the directional transducer with the above configuration,
the core of the waterproof cable 7 is first selected, and the channels of the divided positive
electrode 5a and the common negative electrode 6 are used. A directional transducer of .5 mm
aperture can be configured.
Similarly, if the core wire of the waterproof cable 7 is selected and two channels of the divided
positive electrodes 5a and 5b and the common negative electrode 6 are used in parallel, a
directional transducer equivalent to an opening with a diameter of 15 mm can be configured.
Similarly, if the core of the waterproof cable 7 is selected and three channels of the divided
positive electrodes 5a, 5b, 5c and the common negative electrode 6 are used in parallel, a
directional transducer equivalent to an opening of 30 mm in diameter can be configured. it can.
Therefore, if the frequency range of 50 kHz to 150 kHz, 100 kHz to 300 kHz, and 200 kHz to
600 kHz is set as the measurement range for each opening, the variation of .phi.1 / 2 can be
suppressed to 14 degrees to 45 degrees.
[0012]
As described above, if the channel is switched according to the measurement frequency, the
range of 50 kHz to 600 kHz can be easily measured without replacing the standard.
[0013]
In the above embodiment, the case where three channels are provided adjacent to each other has
been described. However, the present invention is not limited to this, and it is needless to say that
N (where N 同 様 2) channels can be similarly provided. It is.
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The reason why the N channel can be adjacent to one another is that the acoustic impedance of
the piezoelectric polymer is close to the acoustic impedance of water, and the material property
that reflection is small is utilized.
[0014]
In addition to PVDF, P (VDF-TrFE) and P (VDCN-VAC), the piezoelectric polymer as the abovementioned electroacoustic transducer can be made of PZT (lead titanate, zirconate) as a rubber
material. It is of course possible to use mixed particles of V particles and voided polyvinylidene
fluoride (PVD), and in particular, this voided PVDF is particularly suitable for the present
embodiment because the acoustic impedance substantially matches the acoustic impedance of
water. .
[0015]
Although the shape of the piezoelectric polymer is described as being circular, it is not limited to
this, and it is possible to change the width of the main pole of directivity in any shape such as
square, oval, etc. Of course what you can do.
[0016]
Further, although the positive electrode is divided and the negative electrode is described as the
common electrode, it is of course possible to divide the negative electrode and use the positive
electrode as the common electrode.
[0017]
Of course, the piezoelectric polymer may be divided corresponding to the division of the positive
electrode or the negative electrode, or grooves may be formed in that portion without division.
[0018]
As described above, according to the directional transducer according to the present invention,
the piezoelectric polymer is used as the electroacoustic transducer, and the piezoelectric polymer
is used as the positive and negative electrodes. Since at least one of them is coaxially divided and
the channels are connected according to the measurement frequency, the directivity width can be
made within a certain range.
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This has the effect of suppressing the influence of noise and eliminating the difficulty of
alignment.
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