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JP2008078718

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DESCRIPTION JP2008078718
PROBLEM TO BE SOLVED: To provide a transducer which is small in size even in a low frequency
region, has freedom in design, and can be broadened in bandwidth. SOLUTION: The cylindrical
piezoelectric vibrator 10 and a second cylindrical piezoelectric vibrator 11 having an outer
diameter and a length different from each other are disposed inside the first cylindrical
piezoelectric vibrator 10, and the first and second cylinders are arranged. The type piezoelectric
vibrators 10 and 11 are sandwiched by two elastic bodies 12 and 13 from both sides in the
direction of their central axes to form a Langevin type vibrator. The elastic body 12 is made of
cylindrical metal with a hole for bolt at the center, but the elastic body 13 sandwiches the first
cylindrical piezoelectric vibrator 10 with the length in the central axis direction including the
elastic body. It has a structure in which two cylinders or cylinders are combined so that the part
and the part sandwiching the second cylindrical piezoelectric vibrator 11 are different. [Selected
figure] Figure 1
Transducer
[0001]
The present invention relates to a transducer that transmits and receives signals mainly using
ultrasonic waves in water, and in particular, a transducer using a Langevin transducer configured
by sandwiching a piezoelectric transducer between elastic members and bolting it. About.
[0002]
Conventionally, sound waves have been used for transmission and reception of signals in water,
and the handset is composed of a piezoelectric vibrator or an electrostrictive vibrator as shown in
Patent Document 1 below.
04-05-2019
1
[0003]
FIG. 4 is a cross-sectional view showing an example of a conventional transducer using a
Langevin type transducer.
In FIG. 4, the cylindrical piezoelectric vibrator 41 is sandwiched between two elastic bodies 42
from both sides in the central axis direction and is tightened by bolts 45 to form an integral
structure.
The elastic body 42 is made of cylindrical metal with a hole for bolt at the center. A sound wave
is emitted in the central axis direction by applying and exciting a voltage of a specific frequency
to the cylindrical piezoelectric vibrator 41, and a sound wave coming from the central axis
direction is converted into an electric signal by the cylindrical piezoelectric vibrator 41. It is
something to detect.
[0004]
JP 2001-16693 A
[0005]
As in the case of communication on the ground, in the case of communication in the water, there
is a demand for wide bandwidth in order to increase the amount of information.
However, in general, the band is limited by the resonance characteristics of the vibrator. An
example of the frequency characteristic of a transducer using the conventional Langevin type
vibrator shown in FIG. 4 is shown in FIG. Assuming that the length in the central axis direction
including the elastic body 42 of the transducer is L0, the wavelength of the sound wave is λ0,
and the velocity is Vs, resonance occurs at the frequency f0 where f0 = Vs / λ0 = Vs / (2L0) As
shown in FIG. 5, the sound pressure sensitivity becomes maximum at f0. Usually, since the Q
factor of resonance is about 6 to 7 and the center frequency f0 is a low frequency region of
several kHz to several tens of kHz from the viewpoint of communicable distance, communication
environment, etc., its 3 dB bandwidth Δf is , 2 or 3 kHz or less.
04-05-2019
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[0006]
In addition, in order to widen the band, it has been devised to stack elastic bodies with different
elastic constants on the elastic body 42 in FIG. 4 to reduce the Q value of resonance, but the
shape becomes large or lamination There are problems that it is difficult to ensure the reliability
of the adhesive surface of the body and that the degree of freedom in design can not be taken.
[0007]
Therefore, an object of the present invention is to provide a transducer which is small in size and
has a freedom of design even in a low frequency region, and which can be broadened in
bandwidth.
[0008]
In order to achieve the above object, in the transducer of the present invention, a second
cylindrical piezoelectric vibrator having an outer diameter different from that of the first
cylindrical piezoelectric vibrator is disposed inside the first cylindrical piezoelectric vibrator. In
addition, a Langevin type vibrator is used in which the first and second cylindrical piezoelectric
vibrators are sandwiched by two elastic bodies from both sides in the direction of their central
axes and bolted.
[0009]
Preferably, the length in the central axis direction including the elastic body is different between
a portion sandwiching the first cylindrical piezoelectric vibrator and a portion sandwiching the
second cylindrical piezoelectric vibrator.
[0010]
Further, each of the first and second cylindrical piezoelectric vibrators may be driven
independently.
[0011]
In addition, the length in the central axis direction including the elastic body of the portion
sandwiching the first cylindrical piezoelectric vibrator and the central axial direction including
the elastic body in the portion sandwiching the second cylindrical piezoelectric vibrator The ratio
of lengths may be 1/2 to 3/2.
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[0012]
As described above, according to the present invention, by configuring the Langevin-type
vibrator with cylindrical piezoelectric vibrators having two different shapes, the size is small even
in the low frequency region, and there is a degree of freedom in design. A possible transducer
can be provided.
[0013]
Embodiments of the present invention will be described below based on the drawings.
[0014]
FIG. 1 is a sectional view showing a first embodiment of a transducer according to the present
invention.
In FIG. 1, the cylindrical piezoelectric vibrator 10 and the second cylindrical piezoelectric
vibrator 11 having an outer diameter and a length different from each other are disposed inside
the first cylindrical piezoelectric vibrator 10, and the first and second cylinders are arranged. The
type piezoelectric vibrators 10 and 11 are sandwiched by two elastic bodies 12 and 13 from
both sides in the direction of their central axes to form a Langevin type vibrator.
[0015]
The elastic body 12 is made of cylindrical metal with a hole for bolt at the center as in the elastic
body 42 in FIG. 4, but the elastic body 13 has a length in the central axis direction including the
elastic body. It has a structure in which two cylinders or cylinders are combined so that the
portion sandwiching the first cylindrical piezoelectric vibrator 10 and the portion sandwiching
the second cylindrical piezoelectric vibrator 11 are different.
[0016]
In the present embodiment, the cylindrical piezoelectric vibrator 11 has an outer diameter and a
length smaller than that of the cylindrical piezoelectric vibrator 10 and is coaxially disposed
inside the cylindrical piezoelectric vibrator 10.
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Further, the length of the portion where the elastic body 13 and the elastic body 12 sandwich the
cylindrical piezoelectric vibrator 10 is L1, and the length of the portion where the elastic body 13
and the elastic body 12 sandwich the cylindrical piezoelectric vibrator 11 is L2 Then, the
resonance frequency f1 of the portion sandwiching the cylindrical piezoelectric vibrator 10 is f1
= Vs / (2L1), and the resonance frequency f2 of the portion sandwiching the cylindrical
piezoelectric vibrator 11 is f2 = Vs / (2L2) Become.
[0017]
FIG. 2 is a diagram showing an example of the frequency characteristic of the transducer of this
embodiment.
As shown in FIG. 2, the frequency characteristic of this embodiment is a characteristic indicated
by a solid line in which the resonance characteristic indicated by a broken line at frequency f1
and the resonance characteristic indicated by a broken line at frequency f2 are superimposed. It
can be about twice or more as compared with the conventional transducer.
In FIG. 5, the equivalent Q value of resonance is also about half or less than that of the prior art.
[0018]
The frequency characteristics can be optimized according to the purpose by selecting the lengths
L 1 and L 2 and designing the shapes of the cylindrical piezoelectric vibrators 10 and 11.
Furthermore, in the present embodiment, the drive terminals of the cylindrical piezoelectric
vibrators 10 and 11 are taken out independently of each other, and the amplitude and phase of
the drive signals are independently controlled to obtain resonance characteristics and frequency
at the frequency f1. It is also possible to independently control the resonance characteristics at
f2 and adjust the frequency characteristics in which they are superimposed.
As described above, the transducer of this embodiment has a large degree of freedom in design
in the characteristics obtained as compared with the conventional transducer.
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[0019]
Further, in the present embodiment, it is not necessary to stack a plurality of elastic bodies
sandwiching the cylindrical piezoelectric vibrator as in the prior art in order to widen the
bandwidth, so that the size can be reduced.
[0020]
The cylindrical piezoelectric vibrators 10 and 11 used in this embodiment can be made of a
general piezoelectric material such as PZT, and the elastic bodies 12 and 13 are metal materials
such as aluminum, stainless steel, brass and the like. Or, other materials having similar elastic
constants such as sound velocity and density to the above materials can be used.
The shape of the transducer of this embodiment is determined by the frequency to be used, but
the outer diameter is about 10 to 20 cm and the length is about 20 to 50 cm.
[0021]
FIG. 3 is a cross-sectional view showing a second embodiment of a transducer according to the
present invention.
In FIG. 3, the cylindrical piezoelectric vibrator 20 and the second cylindrical piezoelectric
vibrator 21 having different outer diameter and length are disposed inside the first cylindrical
piezoelectric vibrator 20, and the first and second cylinders are arranged. The type piezoelectric
vibrators 20 and 21 are sandwiched by two elastic bodies 22 and 23 from both sides in the
direction of their central axis to form a Langevin type vibrator.
[0022]
Further, the elastic body 22 is made of a cylindrical metal with a hole for bolt at the center as in
the elastic body 42 of FIG. 4, but the elastic body 23 has a length in the central axis direction
including the elastic body It has a structure in which two cylinders or cylinders are combined so
that the portion sandwiching the first cylindrical piezoelectric vibrator 20 and the portion
sandwiching the second cylindrical piezoelectric vibrator 21 are different.
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[0023]
In the present embodiment, the cylindrical piezoelectric vibrator 21 is smaller in outer diameter
and longer in length than the cylindrical piezoelectric vibrator 10, and is coaxially disposed
inside the cylindrical piezoelectric vibrator 20.
Further, the length of the portion where the elastic body 23 and the elastic body 22 sandwich the
cylindrical piezoelectric vibrator 20 is L11, and the length of the portion where the elastic body
23 and the elastic body 22 sandwich the cylindrical piezoelectric vibrator 21 is L22. In the same
manner as in the first embodiment, a wide frequency band is obtained with two resonance
frequencies corresponding to their lengths.
[0024]
As described above, also in the present embodiment, a transducer which is compact and has
freedom in design even in a low frequency region, and can be broadened in bandwidth can be
obtained.
[0025]
Note that if the frequencies f1 and f2 are too far apart, the usable frequency bands are separated,
the ratio of L1 to L2 or the length ratio of L11 to L22 is 1/2 to 3/2 to prevent it. Is desirable.
[0026]
In the present invention, the lengths of the first cylindrical piezoelectric vibrator and the second
cylindrical piezoelectric vibrator are the same, and the lengths in the central axis direction of the
elastic bodies sandwiching them are different. One resonance frequency is obtained, and the
effect of the present invention is obtained.
In addition, even in the case where the lengths of the first cylindrical piezoelectric vibrator and
the second cylindrical piezoelectric vibrator are different and the lengths in the central axis
direction including the elastic body sandwiching them are the same, Since the elastic structures
of the portions sandwiching the two cylindrical piezoelectric vibrators are different and the
04-05-2019
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equivalent sound velocities are different, two different resonance frequencies can be obtained,
and the object of the present invention can be achieved.
In this case, although the effect of the increase in Δf is small, manufacturing and handling
advantages occur.
[0027]
Further, the present invention is not limited to the above-described embodiment, and the shape
and material of the cylindrical piezoelectric vibrator or the elastic body can be selected and
designed according to the target frequency characteristic.
[0028]
1 is a cross-sectional view of a first embodiment of a transducer according to the present
invention;
The figure which shows an example of the frequency characteristic of the transducer of 1st
Example.
Sectional drawing which shows 2nd Example of the transducer by this invention.
Sectional drawing which shows an example of the transducer which used the conventional
Langevin type | mold vibrator. The figure which shows an example of the frequency
characteristic of the transducer which used the conventional Langevin type | mold vibrator.
Explanation of sign
[0029]
10, 11, 20, 21, 41 cylindrical piezoelectric vibrator 12, 13, 22, 23, 42 elastic body 15, 25, 45
bolt
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