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JPH0564285

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DESCRIPTION JPH0564285
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic transducer, and more particularly to an ultrasonic transducer in which the generation
of side lobes accompanying the transmission in the vertical direction is reduced.
[0002]
2. Description of the Related Art In order to uniformly radiate ultrasonic waves from a single
location to a wide area of the seabed or sea area, it is necessary to use an omnidirectional
ultrasonic transducer (hereinafter simply referred to as a transducer). Is formed in an arc shape
as shown in FIG. 1 and the directivity characteristic in this case is shown in FIG.
[0003]
SUMMARY OF THE INVENTION However, when underwater detection is performed, even if
ultrasonic waves are emitted at a uniform level over a wide range, their backscattering intensity
is lower than when they are vertically incident on the object. When obliquely incident, a
difference of about 20 dB occurs.
Therefore, the backscattering intensity in the oblique direction may be equal to or less than the
side lobe accompanying radiation in the vertical direction, and in such a case, the seabed
detection has become impossible.
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[0004]
The present invention has been made to solve the above-mentioned problems, and by reducing
the transmission intensity in the vertical direction, the influence of side lobes accompanying the
transmission in the vertical direction is reduced, and a wide range of underwater is realized. An
object of the present invention is to provide an ultrasonic transducer capable of detection.
[0005]
SUMMARY OF THE INVENTION In order to solve the above problems, the present invention is an
ultrasonic transducer having a wide band characteristic, in which the transmission intensity
radiated downward is reduced compared to the transmission intensity laterally. It is
characterized by having done.
[0006]
[Function] In order to study the transmission characteristics of the oscillator whose oscillation
surface is an arc, as shown in FIG. 3, the oscillator whose oscillation surface is a circle with a
radius of 1 centered on the origin is considered. Try.
As shown in the figure, the arc is expressed by Equation 1 when the −y direction is the direct
direction.
[0007]
[Equation 1] y = -SQR (1-x2) (SQR means a root symbol) Here, it is assumed that the oscillation
surface is replaced by a minute flat vibrating element piece, with this arc as a set of minute
straight lines.
As the inclination of each vibrating element piece approaches 0 (parallel to the x-axis), that is, as
the radiation direction proceeds to the direct downward direction (−y direction), the radiation
intensity in the direct downward direction becomes stronger. Therefore, if the radiation intensity
in the downward direction of the whole of the vibrating element piece is weakened by reducing
the vibrating element pieces whose inclination is close to 0, the transmission intensity in the
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downward direction is reduced, and the seabed erroneous detection in oblique direction by side
lobe Is also suppressed. Then, in order to know the inclination of the equation 1, the equation y
can be obtained by obtaining the derivative y 'of y.
[0008]
(2) y '= x / SQR (1-x2) In the equation (2), when x is smaller than 1 and sufficiently close to 0,
SQR (1-x2) 式 1 holds, so equation 2 becomes y' It can be approximated as = x. Therefore, in the
vicinity of the coordinate (0, -1), the inclination of the arc is approximately equal to the x
coordinate value. In order to reduce the radiation in the downward direction near the coordinates
(0, -1), the inclination in this portion may be increased, and therefore, here, assuming an
equation having the inclination α times the x coordinate Assuming that Y is Y, the differential
expression Y ′ is Y ′ = αx, and is expressed as Y = αx2 / 2 + C. That is, by making the
oscillation surface not a circular arc but a quadratic curve (parabola), the radiation intensity in
the downward direction can be reduced as shown by the directivity characteristic of FIG.
[0009]
In addition, as another means for reducing the radiation intensity in the downward direction, the
conventional vibrator that radiates a uniform intensity over a wide range is used, and in order to
reduce the radiation intensity in the downward direction from this oscillator, the downward
direction Provide a sound insulation material that increases the sound insulation effect, or
configure the vibrator with a plurality of vibrating element pieces, and weight the excitation
voltage to each vibrating element piece so that the radiation intensity in the downward direction
is reduced. May be set, and specific configuration examples thereof will be described in the
following embodiments.
[0010]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 5 shows a vertically elongated
flat transducer element bent in a direction perpendicular to its longitudinal direction so as to
have a secondary parabolic curve with a cross-sectional shape of y = x2 / 60 (mm). The obtained
oscillator 1 is shown, and the simulation of the directivity characteristic when the size in the x
direction is 12 cm at −60 mm to 60 mm and the applied frequency is 500 KHz is shown in FIG.
It is reduced by about 10 dB.
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By the way, since the vibrator is hard and brittle and it is difficult to form an arbitrary curve, it is
formed into a quadratic curve of y = 1.1 × 2/30 (mm) using six linear vibrating element pieces
The vibrator 2 shown in FIG. 7 is shown in FIG. 7. As shown in FIG. 8, the directivity
characteristic at this time is reduced by about 20 dB in the downward direction.
[0011]
FIG. 9 shows a combination of two arc-shaped vibrators 3a and 3b with a radius of 51.356 mm in
the form of a quadratic curve, and the directivity characteristic at this time is approximately
approximately in the direct direction as shown in FIG. It is reduced by 15 dB. In the above
embodiment, the transmission intensity in the downward direction is weakened by changing the
inclination of the oscillation surface in the vicinity of the lowermost portion of the oscillator to
suppress the occurrence of side lobes associated therewith. An embodiment of the invention will
be described.
[0012]
FIG. 11 shows a crescent-shaped sound insulation material 5 whose thickness becomes maximum
at the lowermost part (central part) close to the lower part of the conventional arc-shaped
vibrator 4 with a radius of 30 mm, the longitudinal direction of the vibrator 4 It is provided in
the (vertical direction with respect to the paper), and the directivity characteristic in this case is
reduced by at most 10 dB in the downward direction, as shown in FIG.
[0013]
FIG. 13 shows that the sound insulation material 5 'is provided in the longitudinal direction of the
vibration arc 4 with respect to the curved central portion of the vibrator 4, and substantially the
same effect as that of FIG.
[0014]
In any of the above-described vibrators, the mold is surrounded by a mold having a certain
thickness in order to protect its oscillation surface, but as shown in FIG. Even in this case, the
same sound insulation effect as in the case of FIG. 11 can be obtained.
[0015]
FIG. 15 shows a cavity X formed in the longitudinal direction of the vibrator 4 in the mold 6 at
the curved central portion instead of thickening the mold 6 at the curved central portion of the
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vibrator 4 in FIG. The same effect as 14 is obtained.
[0016]
If the frequency applied to the vibrator 4 is high, it is not necessary to use an arc-shaped one as
in the vibrator 4 in FIG. If it is long, a linear transducer can be used.
[0017]
The vibrator 8 shown in FIG. 17 has minute vibrator pieces 8a arranged in a circular arc, and the
excitation voltage applied to each of the vibrator pieces 8a is the smallest at the lowermost
portion (0.25 The same effect as that of the above-described embodiment can be obtained by
setting a weight of 1 on both sides.
[0018]
FIG. 18 shows electrodes P and Q formed on the surface of the vibrator 4 whose cross section
has an arc shape (note that these electrodes are also formed on the above-described vibrators but
are omitted). In the curved central portion of the inner electrode P, two electrode cuts Z in which
the electrodes are cut out are formed along the longitudinal direction of the vibrator 4.
The electrodes P which are divided to the left and right by the electrode cut Z are connected to
each other by a crossover m.
In this configuration, when an excitation signal is applied between the electrodes P and Q, the
electrode P ′ divided by the electrode cut Z is dragged by the vibration on both sides regardless
of non-excitation and vibrates.
Therefore, in order to damp the vibration at the electrode P ′, the electrode P ′ is shortcircuited to the electrode Q on the back surface with the crossover wire n.
According to this configuration, since the vibration of the bending central portion of the vibrator
4 is suppressed, the transmission intensity in the downward direction is reduced.
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The same effect can be obtained even if the electrode cut Z is provided on the outer electrode Q.
[0019]
As described above, according to the present invention, the curvature of the curved central
portion of the ultrasonic transducer is made larger than that of other portions, or a sound
insulating material is provided at the curved central portion of the ultrasonic transducer. Since
the transmission intensity in the downward direction is reduced by the etc., the side lobe
generated along with the transmission in the downward direction is reduced, so that the side lobe
signal is also detected for the detection signal in the oblique direction. Can be detected reliably
without being buried in
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