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DESCRIPTION JPH09271093

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DESCRIPTION JPH09271093
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
acoustic water transmitter and a method of adjusting its characteristics, and more particularly, to
a transmitter capable of emitting sound in a wide frequency band and a method of adjusting a
frequency band.
[0002]
2. Description of the Related Art An acoustic water transmitter and receiver are used to measure
the distance to a target object in the water or the sea floor. In water, since the sound wave has a
smaller propagation attenuation than the electromagnetic wave, various transmitters using
ultrasonic waves have been developed.
[0003]
Reference is made to the inclining view of FIG. 5 and the sectional view of FIG. 6 showing a
conventional cylindrical transmitter utilizing water column resonance. In this transmitter, the
piezoelectric vibrators 10a, 10b, 10c, 10d and 10e in the form of cylinders, that is, hollow
cylinders, are stacked on a cylindrical axis and adhered to each other, and the respective
piezoelectric vibrators 10a, 10b, 10c, 10d and 10e are provided with copper plates 20a, 20b,
20c and 20d for fastening adjacent internal electrodes, and copper plates 30a, 30b, 30c and 30d
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for fastening external electrodes on the opposite side are provided, and a cable connected to an
oscillation source 40 are respectively connected to the inner and outer surfaces of the
piezoelectric vibrator 10a, and the entire surface is covered with a synthetic resin 50 such as
urethane or polystyrene to ensure watertightness.
[0004]
Here, the coating of the cable 40 and the synthetic resin 50 prevent the entry of water, thereby
preventing the deterioration of the internal wiring, the piezoelectric vibrator, the copper plate,
and the like. Further, the height m of the piezoelectric vibrator 10a is uniform everywhere on the
circumference, and the other piezoelectric vibrators 10a, 10b, 10c, 10d and 10e are common.
[0005]
The piezoelectric vibrators 10a, 10b, 10c and 10d are called piezo electric vibrators or piezo
electric transducers, and used as resonators or as an electro-mechanical energy conversion
element, piezoelectric As materials, Rochelle salt and various porcelain materials are used.
[0006]
When a voltage is applied from the cable 40 to the transmitter of such a configuration, the
cylindrical piezoelectric vibrators 10a to 10e expand and vibrate in diameter, and the density of
the medium in the cylinder is increased through the resin 50 to generate a water column.
[0007]
Reference is made to the cross-sectional view of FIG. 7 showing a vibration model of the water
column in this cylinder.
The vibration in the cylindrical tube 80 is a standing wave having a maximum amplitude 81 at
both ends and a node 82 at the center, and emits sound waves from both upper and lower ends.
[0008]
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In such a transmitter, the approximate resonance frequency is determined by the height of the
cylinder, that is, the height of the water column, but the loss of the medium or the piezoelectric
vibrator is small, the acoustic radiation surface is small, and the acoustic load is not easily
applied. Thus, since the resonance characteristic is sharp and Q is high, the frequency band that
can be transmitted is extremely narrow.
For this reason, not only the radiation loss increases when the transmission frequency fluctuates,
but there is also the disadvantage that transmission can not be performed when the transmission
frequency is changed.
[0009]
Therefore, in order to realize a wide transmission frequency band, it has been necessary to
arrange a large number of transmitters with slightly different resonance frequencies. In addition,
in the case of modulating and transmitting the transmission frequency, it is necessary to have a
frequency bandwidth that radiates up to both sidebands, but it is accurate by increasing the
radiation loss of both sidebands due to the sharp resonance characteristic. It also has the
disadvantage that it can not send out
[0010]
Another conventional broadband underwater acoustic wave transmitter is disclosed in JP-A-61230599. In this transmitter, the sound wave radiation vibration shell (shell) 91 is a thick-walled
cylinder, a plurality of holes 92 are processed and arranged in a cylindrical shape in the thickwalled cylinder, and a taper is provided inside the thick-walled cylinder. Insert the tapered
cylindrical piezoelectric ceramic vibrator 93 and tighten it with the bolt 96 and the nut 97
through the insulating washer 94 and the push 95 to give the piezoelectric ceramic vibrator 93 a
suitable circumferential compressive bias stress, An electric signal is applied to the outer and
inner electrodes of the cylinder of the piezoelectric ceramic vibrator 93 by the lead wires 98 and
99 to drive it, and the outer side of the shell 91 is placed in water as a medium, thereby sound
wave from the outer surface of the shell 91 into water. There is a statement to the effect that it
was made to emit.
[0011]
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Since this configuration utilizes the complex resonance characteristic in which eight holes 92 and
the like are provided in the shell 91, not only the structure becomes complicated, but also the
adjustment position of the dimension for setting the central resonance frequency In addition,
since the taper is formed on the side of the shell 91 and on the side of the vibrator 93,
adjustment of the taper is not sufficient only by processing the vibrator 93. In addition, because
of the complex resonance structure, a number of peak values appear in the frequency
characteristic, and a smooth characteristic curve can not be obtained.
[0012]
Reference is made to Japanese Patent Application Laid-Open No. 60-194380, which shows an
ultrasonic sensor. There is disclosed a technique for fixing the horn by tilting it upward so that
the directivity characteristics of the ultrasonic horn do not face the ground, but such a technique
may be applied to water, but It does not contribute at all to broadening the frequency of
[0013]
SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention
is to provide an acoustic water wave transmitter having the following functions. (1) A cylindrical
transmitter using water column resonance is equipped with a wide transmission frequency band.
(2) It is not necessary to arrange many transmitters. (3) A modulated transmission frequency can
be emitted with good characteristics. (4) A common transmitter can be used even if the
transmission frequency is changed. (5) The radiation loss does not increase even if the
transmission frequency changes. (6) Instead of a complex resonant structure, a simple single
resonant structure is adopted. (7) Minimize the number of adjustment points for obtaining
desired frequency characteristics. (8) The adjustment of the inclination angle such as the taper
can be performed only by the processing of the vibrator. (9) The structure is simple and easy to
manufacture. (10) Ensure sufficient water tightness. (11) To obtain a frequency characteristic
having a smooth peak value, not a frequency characteristic curve having a large number of peak
values as seen in the case of a composite resonant structure.
[0014]
SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an acoustic
underwater transmitter according to the present invention comprises a single cylindrical
piezoelectric vibrator or a plurality of cylindrical piezoelectrics arranged with their cylindrical
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axes aligned. In the sound wave submersible wave transmitter provided with a vibrating portion
comprising a vibrator, the cylindrical axes are aligned at one end and the other end of the
vibrating portion, and cylindrical tubes are arranged, and a circle at one end and the other end of
the cylindrical tube The circumferential end face is configured to be inclined not orthogonal to
the cylindrical axis.
[0015]
Further, according to another aspect of the present invention, there is provided an acoustic
submersible wave transmitter comprising a vibration part comprising a single cylindrical
piezoelectric vibrator or a plurality of cylindrical piezoelectric vibrators arranged with their
cylindrical axes aligned. In the wave transmitter, circumferential end faces of one end and the
other end of the vibrating portion are configured not to be orthogonal to the cylindrical axis but
to be inclined.
[0016]
Furthermore, the method of adjusting the characteristics of the submersible acoustic wave
transmitter according to the present invention is configured to adjust the degree of inclination of
the circumferential end face of the cylindrical tube or the vibrating portion so as to obtain a
desired frequency bandwidth characteristic. .
[0017]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the perspective view
of FIG. 1 and the sectional view of FIG. 2 showing a first embodiment of the present invention.
In the transmitter of this embodiment, the uniform cylindrical piezoelectric vibrators 1a, 1b and
1c of height are laminated on the cylindrical shaft 9 and adhered to each other, and further
between the piezoelectric vibrators 1a and 1b, piezoelectric vibration Copper plates 2a and 2b
and copper plates 3a and 3b are provided on the inner and outer surfaces between the elements
1b and 1c. For example, all of the inner electrodes are positive electrodes, and all of the outer
electrodes are negative electrodes.
The copper plates 2a and 2b are similarly formed in the places facing the copper plates 2a and
2b, and the copper plates 3a and 3b are also provided on the opposite outer surface of the
opposed copper plates 2a and 2b.
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[0018]
Here, the cables 4 are connected to the inner surface and the outer surface of the piezoelectric
vibrator 1a, respectively.
This cable 4 has a watertight coating. The obliquely cut cylindrical tube 6a is laminated on the
cylindrical shaft 9 and adhered to the inner peripheral end face of the upper end of the laminated
piezoelectric vibrator 1a.
[0019]
The lower end of the cylindrical tube 6a exhibits a plane perpendicular to the cylindrical axis 9
so as to fit the upper end of the piezoelectric vibrator 1a, but the upper end exhibits a
circumferential end face obliquely cut with respect to the cylindrical axis 9. The cable 4 is
connected to both surfaces of the piezoelectric vibrator 1a by inserting the obliquely cut
cylindrical tube 6a.
[0020]
The obliquely cut cylindrical tube 6b is similarly bonded to the lower end of the piezoelectric
vibrator 1c. Both the upper and lower obliquely cut cylindrical tubes 6a and 6b are not
piezoelectric vibrators, and an electrically insulating pair having a high elastic modulus is
preferable. Moreover, it is preferable to arrange the circumferential portion of the smallest height
among the upper and lower obliquely cut cylindrical tubes 6a and 6b so as to overlap in the
vertical direction along the cylindrical axis 9, and therefore the circumferential portion of the
largest height It is preferable that the upper and lower ones overlap.
[0021]
A resin 5 is provided to cover the exposed surface of the cable 4 and the surfaces of the
cylindrical tubes 6a, 6b, the piezoelectric vibrators 1a, 1b, 1c, and the copper plates 2a, 2b, 3a,
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3b for watertight protection. The cylindrical diameters of the obliquely cut cylindrical tubes 6a
and 6b and the piezoelectric vibrators 1a, 1b and 1c are common, and the thickness between the
outer diameter and the inner diameter is also common.
[0022]
Now, reference is made to FIG. 4 showing the frequency characteristics when the transmitter has
an outer diameter of 75 mm, an inner diameter of 58 mm, a height A of 190 mm and a height B
of 210 mm. When an oscillation source is connected to the cable 4 and a voltage is applied, the
piezoelectric vibrators 1a, 1b, 1c vibrate by respiration, and a water column resonance occurs in
which both ends of the cylinder are antinodes of the vibration and the central part is a node.
[0023]
Here, when the frequency of the oscillation source is changed, the frequency characteristic of the
transmission level of FIG. 4 is obtained. The solid line in FIG. 4 is a characteristic curve in the
case of the above-described embodiment, and the dotted line is a characteristic curve when the
heights A and B are common to the conventional example and this is 200 mm.
[0024]
In general, the water column resonance angular frequency ω is as shown in FIG. 4, and A is A =
α3 × L / 2a + α4. Further, α1 is a coefficient determined by the velocity of sound and elastic
modulus of the medium, the inner radius of the piezoelectric vibrators 1a, 1b and 1c and the
elastic modulus, and α2, α3 and α4 are correction coefficients of the end portion of the
cylinder. L is a cylindrical shape length. As the medium, water, one having a modulus of 6.1 ×
10 10 (N / m 2) of a piezoelectric vibrator is used.
[0025]
Now, when the applied frequency is changed from the low band to the high band, water column
resonance starts to occur at a portion corresponding to 210 mm of the cylindrical height B, and
the frequency at this time is 2.26 KHz. When the frequency of the oscillation source is further
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raised, water column resonance occurs up to a portion corresponding to 190 mm of height A,
that is, 2.57 KHz. That is, the substantially usable frequency band is at least 0.32 KHz.
[0026]
In order to secure a wider frequency band, it is necessary to increase the dimensional difference
between the heights A and B, that is, to increase the inclination angle.
[0027]
According to this embodiment, since the both ends are inclined in a cylindrical shape, a structure
in which the length (height) of the cylindrical body changes continuously is exhibited, whereby
the sharp resonance characteristic is blunted. Thus, wide frequency characteristics can be
obtained.
[0028]
In addition, since the frequency bandwidth can be changed only by changing the inclination
angle of both ends, adjustment and fabrication are not only extremely easy, but also in frequency
characteristics exhibiting a large number of peak values as in a complex resonance structure.
Instead, since the peak value is extremely smooth as shown by the solid line in FIG. 4, an ideal
transmission wave can be obtained even when amplitude or frequency modulation is applied.
[0029]
Next, reference is made to FIG. 3 showing a second embodiment of the present invention.
This embodiment is different from the first embodiment described above in that obliquely cut
piezoelectric vibrators 7a and 7b, copper plates 3c and 3d on the outer surface, and copper
plates 2c and 2d on the inner surface exist, and so on. Is common to the first embodiment, the
description of the configuration effect of this common part is omitted.
[0030]
The obliquely cut piezoelectric vibrators 7a and 7b have the same external dimensions as the
obliquely cut cylindrical tubes 6a and 6b in FIG. 1 respectively, but have different properties of
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the material, and piezoelectric vibration such as piezoelectric vibrators 1a, 1b and 1c. It consists
of a child.
After laminating and bonding the obliquely cut piezoelectric vibrator 7a and the piezoelectric
vibrator 1a, the inner and outer electrodes are fastened with copper plates 2c and 3c
respectively, and the obliquely cut piezoelectric vibrator 7b and the piezoelectric vibrator 1c are
laminated and then adhered The external electrodes are fastened with copper plates 2d and 3d,
respectively.
The polarization directions of the inner and outer electrodes are the same as those of the
piezoelectric vibrators 1a, 1b and 1c. The cable 3 is connected to the outer surface of the
obliquely cut piezoelectric vibrator 7a.
[0031]
According to this embodiment, it is possible to obtain a smaller characteristic of the transmission
level loss than the solid line in FIG.
[0032]
The inclination angles of the circumferential end faces of the cylindrical tube in the first
embodiment and the obliquely cut piezoelectric vibrator in the second embodiment are
manufactured with values designed in advance so as to obtain a desired frequency bandwidth.
Although it is good, in order to obtain a more accurate frequency bandwidth, it is desirable to
finely adjust the tilt angle by cutting or grinding with a cutting tool.
[0033]
In the first embodiment, the number of piezoelectric vibrators is three. However, the number of
piezoelectric vibrators is not limited to three, and may be one, two, or four or more.
Further, in the second embodiment, although the number of piezoelectric vibrators is five
including obliquely cut ones, it is not limited to this, and may be one, two, three, four or more. Of
course, it may be six or more.
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[0034]
As described above, according to the present invention, not only widening the frequency
bandwidth but also smoothing is achieved by inclining the circumferential surfaces of both ends
of the cylindrical piezoelectric vibrator or cylindrical tube. A frequency characteristic having a
peak value is obtained, and the above-mentioned object is achieved in a remarkable manner.
[0035]
Brief description of the drawings
[0036]
1 is a perspective view showing a first embodiment of the present invention.
[0037]
2 is a cross-sectional view of the first embodiment.
[0038]
3 is a cross-sectional view showing a second embodiment of the present invention.
[0039]
4 is a characteristic diagram showing the frequency characteristics of the first embodiment and
the conventional example.
[0040]
5 is a perspective view showing a conventional single underwater wave transmitter.
[0041]
6 is a cross-sectional view of the underwater wave transmitter of FIG.
[0042]
7 is a cross-sectional view showing a vibration model of the water column of the underwater
wave transmitter.
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[0043]
8 is a cross-sectional view showing another conventional underwater wave transmitter.
[0044]
Explanation of sign
[0045]
1a, 1b, 1c, 10a, 10b, 10c, 10e Piezoelectric vibrators 2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d, 20a, 20b, 20c,
20d, 30a, 30b, 30c, 4 and 5 Reference Signs List 40 cable 5, 50 resin 6a, 6b obliquely cut
cylindrical tube 7a, 7b obliquely cut piezoelectric vibrator 80 cylindrical pipe 81 amplitude 82
section 91 shell 92 hole 93 vibrator 94 washer 95 bush 96 bolt 97 nut 98, 99 lead wire
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