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DESCRIPTION JPH08275295

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DESCRIPTION JPH08275295
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
acoustic transducer which is intended to transmit and receive in water mainly at around 100 kHz
to several hundreds of kHz.
[0002]
2. Description of the Related Art FIG. 6 is a cross-sectional view of a conventional acoustic
transducer in which a plurality of rectangular parallelepiped transducers are arranged at equal
intervals and fixed by a synthetic resin. As shown in FIG. 6, in the conventional acoustic
transducer, electrodes are formed on both sides of the piezoelectric ceramic vibrator 1, lead
wires 4a and 4b are connected to each of the electrodes on the both sides, and they are drawn
out into the housing 5. And is connected to the underwater connector. Further, the piezoelectric
ceramic vibrator 1 is mounted by the rings 12 and 13 from the back surface integrated with the
housing 5 through the two-layer plates 10 and 11, watertightness is achieved by the O-ring 9,
and it can be used underwater It becomes a thing.
[0003]
In addition, in order to obtain desired directivity characteristics at a desired frequency, a plurality
of rectangular piezoelectric ceramic vibrators are arrayed at equal intervals, and the electrodes
are provided on both end faces of the piezoelectric ceramic vibrator so that the length can be
obtained. A plurality of the arrayed sound sources are arranged such that the ones polarized in
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the direction are one acoustic surface of the electrode and the polarization direction is the same.
[0004]
In the conventional method, since the vibration mode in the longitudinal direction is used to
obtain the required resonance frequency, the vibrator becomes smaller as the frequency band
becomes higher.
In the case of forming an array sound source, it is necessary to position one by one rectangular
transducers, and as the number of arrays increases, there is a tendency that it becomes difficult
to assemble by increasing the dimensional accuracy of the array.
[0005]
In order to solve this problem, there is a method of using transducers that merely insert slits at
equal intervals in a rectangular parallelepiped transducer, but the directivity is determined by the
shape of the original plate, so the side lobes It was difficult to suppress. In order to suppress the
side lobes, it is effective to change the shape of the vibrator from a simple rectangular
parallelepiped to a trapezoid or a rhombus. However, since the vibrator is a fragile piezoelectric
ceramic material, it is very difficult to process it into a complicated shape, and a sufficient side
lobe suppressing effect has not been obtained.
[0006]
The present invention is to eliminate these drawbacks and to provide an acoustic transducer in
which excellent directivity characteristics can be easily obtained with suppressed side lobes at a
desired resonance frequency.
[0007]
SUMMARY OF THE INVENTION According to the present invention, there is provided an acoustic
transducer in which a slit is inserted from one side of an electrode of a piezoelectric ceramic
vibrator of a rectangular plate which is polarized by electrodes provided on both sides in the
thickness direction. In the above, when the length of one side of the sound source of the unit
acoustic surface where the piezoelectric ceramic vibrator is divided by the slit is 1, the depth of
the slit is 3 times or more, and the pitch and width of the slit are changed. , An acoustic
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transducer characterized by being subjected to shading.
[0008]
Shading is a method of controlling to some extent the directional pattern of a specific array
sound source.
Specifically, amplitude shading is commonly known which shades the array of piezoelectric
ceramic vibrators so as to obtain a maximum response at the center of the array and reduce the
response toward the periphery.
[0009]
The shading of the acoustic transducer according to the present invention is a method according
to the general Chuvisshev shading, a method of binomial shading etc., or an arbitrary array pitch
to simulate only a specific side lobe, simulating the source size of one unit There is a method of
setting by calculation and applying shading equivalently.
[0010]
When shading is applied by the method of the present invention, there is a problem of removing
the coupling between the thickness vibration mode that determines the resonance frequency and
the vibration direction in the spreading direction that changes depending on the size of the
piezoelectric ceramic vibrator that determines the directional characteristics.
[0011]
In the present invention, in determining the arrangement configuration, the dimensional ratio of
the depth of the slit to the opening (individual sound source dimensions after slit processing) is
set roughly so that the thickness vibration mode and other modes do not cause coupling. Do as
follows.
[0012]
Sound source size: Slit depth = a: N · a (N ≧ 3; where a represents one side length of the sound
source size) By determining such a size ratio, it is possible to suppress the coupling of vibration
modes. .
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[0013]
Therefore, side lobes are suppressed when designing as an array sound source shaded by the
sound source strength or array pitch by processing the slits in the piezoelectric ceramic vibrator
used in the present invention with the above-mentioned dimensional ratio. An acoustic
transducer with a single resonant frequency with excellent directional characteristics is obtained.
That is, when processing the slits in the vibrator, by changing the pitch and width, it is possible
to obtain an acoustic transducer in which the side lobes are suppressed by applying shading.
[0014]
Embodiments of the present invention will be described below with reference to the drawings.
[0015]
FIG. 1 is a cross-sectional view of a transducer according to a first embodiment of the present
invention.
The acoustic transducer according to the present invention is, as shown in FIG. 1, integrally
formed with the piezoelectric ceramic vibrator 1, the housing 5 for housing the piezoelectric
ceramic vibrator 1, the lid 7 of the housing 5 with the underwater connector 8 and the housing
5. It comprises an acoustic rubber 6 which is made up of two layers of plates 10 and 11 and
rings 12 and 13.
[0016]
Furthermore, the electrodes 2a and 2b are formed on both sides of the piezoelectric ceramic
vibrator 1, the side of the electrode 2a is conducted by a conductive foil (for example, a
conductor such as copper foil) 3 and the lead wires 4a and 4b are formed. , Are respectively
connected, and are drawn out into the housing 5.
[0017]
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As described above, the piezoelectric ceramic vibrator 1 to which the lead wires 4a and 4b are
attached is bonded (or pressure-welded) to the acoustic rubber 6 by the lids 7 with the rings 12
and 13 via the double plates 10 and 11 from the back. In order to be watertight at the O-ring 9, it
becomes an acoustic transducer usable in water.
[0018]
FIG. 2 is a plan view and a sectional view of a piezoelectric ceramic vibrator according to a first
embodiment of the present invention.
As shown to Fig.2 (a), the sound source 1b is dicing-processed so that it may become length 1a of
one side.
Furthermore, as shown in FIG. 2B, the depth t of the slit 21 of the piezoelectric ceramic vibrator
1 is set to three times the length 1a of one side of the dimension of the sound source 1b, and the
width S of the slit 21 is I'm changing the dimensions.
Thus, assuming that the sound source intensity at the central portion of the piezoelectric ceramic
vibrator 1 is 1, for example, the sound source intensity of "1, 0. 69, 0.30" toward the outer
peripheral direction according to Chevyshev's shading. The dimensions are determined.
An acoustic transducer using a piezoelectric ceramic vibrator that performs such shading can
obtain excellent directivity with suppressed side lobes as shown in FIG.
[0019]
In FIG. 3, the directional characteristics (shown by dotted lines) of the first embodiment in the
case of applying Chewyshev shading and the conventional product do not apply shading of “1,
1, 1” as the sound source intensity at even intervals. Directional characteristics (indicated by
solid lines) are shown together for comparison.
[0020]
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As can be seen from FIG. 3, in the directivity characteristics of the conventional product, as
shown by the curve A, the second curve 16 and the third curve 17 are larger than the first curve
15, and in the directivity characteristics of the first embodiment, As shown by curve B, the
second curve 19 and the third curve 20 are smaller than the first curve 18.
The side lobes are the second curves 16, 19 and the third curves 17, 20.
This indicates that the sound in one direction is clearly transmitted or received, and the
transmission or reception disturbance due to the unwanted reflected sound is reduced.
That is, the directivity characteristics show that the first embodiment of the present invention is
far superior to the conventional product.
[0021]
FIGS. 4A and 4B show an example in which the piezoelectric ceramic vibrator 1 used in the
acoustic transducer according to the second embodiment of the present invention is shaded to
change only the arrangement pitch. . That is, in the piezoelectric ceramic vibrator 1, the length
1a of one side of the sound source 1b is the same, but the depth t of the slit 21 is three times the
length 1a of one side. Further, in the widths S1, S2 and S3 of the slits 21, the pitches h1, h2 and
h3 are 1: 1.5: 2.0.
[0022]
The directivity characteristic of the acoustic transducer according to the second embodiment also
has a curve as shown in FIG. 3, and the second curve and the third curve become smaller in
comparison with the first embodiment. That is, the side lobe is suppressed.
[0023]
5 (a) and 5 (b), the piezoelectric ceramic vibrator 1 used in the acoustic transducer according to
the third embodiment of the present invention is shaded by changing the area of the unit
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acoustic surface, An example in which the depth of the slit 21 is changed is shown. That is, in the
piezoelectric ceramic vibrator 1, the lengths 1a to 3a of one side of the unit acoustic surface 1b
are directed from the central portion to the outer peripheral direction, for example, 1a: 2a: 3a =
1: 0.69: 0.3 By making the size of the sound source, the depth of the slit 21 can be changed as
follows. The depths t1, t2 and t3 of the slits 21 are in the relationship of t1> t2> t3, but the
depths of the slits 21 are three times the lengths 1a, 2a and 3a of one side of the unit acoustic
surface. In an acoustic transducer using a piezoelectric ceramic vibrator to which such shading is
applied, excellent directivity characteristics in which side lobes are suppressed as shown in FIG. 3
can be obtained.
[0024]
According to the present invention, it is possible to obtain an underwater acoustic transducer
having directivity characteristics in which side lobes of a single resonance frequency are
suppressed in a high frequency band.
[0025]
Brief description of the drawings
[0026]
1 is a cross-sectional view showing an acoustic transducer according to a first embodiment of the
present invention.
[0027]
2 is a plan view and a cross-sectional view of a piezoelectric ceramic vibrator according to a first
embodiment of the present invention.
FIG. 2A is a plan view.
FIG.2 (b) is sectional drawing.
[0028]
3 is a diagram showing an example of the present invention and the conventional directional
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characteristics.
[0029]
4 is a plan view and a cross-sectional view of a piezoelectric ceramic vibrator according to a
second embodiment of the present invention.
FIG. 4A is a plan view.
FIG.4 (b) is sectional drawing.
[0030]
5 is a plan view and a cross-sectional view of a piezoelectric ceramic vibrator according to a third
embodiment of the present invention. FIG. 5 (a) is a plan view. FIG.5 (b) is sectional drawing.
[0031]
6 is a cross-sectional view showing an example of a conventional acoustic transducer.
[0032]
Explanation of sign
[0033]
DESCRIPTION OF SYMBOLS 1 piezoelectric ceramic vibrator 1a one side length 1b sound source
2a, 2b electrode 3 foil 4a, 4b lead wire 5 conductor 6 acoustic rubber 7 lid 8 underwater
connector 9 O ring 10 plate 10 plate (insulation plate) 11 plate (back) Plate) 12 Ring (Presser
bracket) 13 Ring (Onion skin paper) 15 (conventional product) first curve 16 (conventional
product) second curve 17 (conventional product) third curve 18 (of the first embodiment) First
curve 19 Second curve 20 (of the first embodiment) Third curve 21 (the first embodiment) Slit
41 Composite resin material 42 Adhesive layer A Curve B of the conventional product Curve S of
the first embodiment of the present invention , S1, S2, S3 (slit) width h1, h2, h3 pitch t (slit)
depth
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