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JP2012134909

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DESCRIPTION JP2012134909
To provide an acoustic transducer capable of achieving low frequency, small size and light
weight. A first annular member (20) and a second annular member (30) stacked in the direction
of an axis O via a buffer material (5), and a part of the first annular member (20) and a second
annular member in the circumferential direction Notches C which are formed by notching and
which form the first end 21, 31 and the second ends 22, 32 in the first annular member 20 and
the second annular member 30, and a pair of these notches C Are provided to form the ring
vibrator 10 by providing the first connecting portion 40 and the second connecting portion 50
that connect the first annular member 20 and the second annular member 30 so as to intersect
the axis O direction. . [Selected figure] Figure 1
Acoustic transducer
[0001]
The present invention relates to an electroacoustic transducer that emits a sound wave to a
liquid, and more particularly to an acoustic transducer that can emit a sound wave into water
efficiently.
[0002]
As an acoustic transducer provided with a ring vibrator for emitting an acoustic wave into a
liquid such as water, there is known an acoustic transducer in which one or more annular
members having a hollow inside are provided in the axial direction.
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The acoustic transducer is configured to emit a sound wave based on the vibration into the liquid
by supplying a current to the annular member to vibrate the entire ring vibrator. As such an
acoustic transducer, the thing of patent document 1 and patent document 2 is mentioned.
[0003]
In the acoustic transducer described in Patent Document 1, a plurality of ring vibrators each
having a hollow inside are coaxially connected in the axial direction, the upper end in the axial
direction of the ring vibrator is supported by the ring, and the lower end in the axial direction Is
supported by a ring. Further, the ring at the axially upper end and the ring at the axially lower
end are fixed by bolts and nuts that penetrate the hollow interior. Furthermore, a thin axial
diaphragm that vibrates in a flexural vibration mode is supported around the ring vibrator, and
disk-shaped end diaphragms that vibrate in a flexural vibration mode at both ends of the axial
diaphragm. Are provided respectively. And by making the mechanical resonance frequency of an
axial direction diaphragm and an end surface diaphragm different, a broadband sound wave
radiation characteristic can be obtained. As a similar structure, as in the acoustic transducer
described in Patent Document 3, a thin axially-long rectangular diaphragm on which a
piezoelectric vibrator vibrating in a bending vibration mode is attached is disposed on a plurality
of circumferences, and A method of acoustically reflecting in water using bending vibration has
been proposed.
[0004]
The acoustic transducer described in Patent Document 2 includes a coiled vibrator formed in a
spiral shape by an electrostrictive material that generates a strain in response to an applied
voltage. Further, the upper end portion and the lower end portion of the coiled vibrator are fixed
to a metal fitting. Thereby, the vibration generated in the coiled vibrator can be converted into
the low frequency radial vibration corresponding to the length of the coiled vibrator.
[0005]
JP 2001-333487 A JP 60-196 100 A
[0006]
By the way, in the case of an acoustic transducer that radiates sound into water using respiratory
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vibration of a ring vibrator, in the case of a structure in which both ends are sealed so that liquid
does not flow in and the inside is filled with air etc. There has been a problem that high-efficiency
acoustic radiation can not be obtained when driven at a frequency lower than the resonant
frequency of the respiratory vibration mode.
[0007]
Here, as a drive source generally used as a ring vibrator, a ring-shaped piezoelectric vibrator
such as a piezoelectric ceramic or the like having a simple structure and driving or a polygonal
ring vibrator in which rectangular piezoelectric vibrators are arrayed in a cylindrical shape are
used. Be
Lead zirconate titanate, which is a piezoelectric material, is a material whose mass and elastic
modulus are almost equal to that of metal.
Now, the resonant frequency of the ring oscillator is proportional to the square root of the elastic
modulus of the constituent material and inversely proportional to the square root of the density.
When the circumferential length of the ring oscillator corresponds to one wavelength of the
velocity of sound of the constituent material, the ring oscillator resonates in a respiratory
vibration mode that uniformly increases or decreases from the basic state to a small radius
contraction state or a large radius expansion state. Do. As described above, this resonant
frequency is determined by the density and elastic modulus of the piezoelectric ceramic, and the
velocity of sound of the piezoelectric ceramic is very high because it is as fast as metal. In
addition, there is also a piezoelectric ceramic called a soft system having a small elastic modulus,
but the resonance frequency can not be greatly reduced.
[0008]
In general, as a ring vibrator, an electrode is disposed on the inner and outer surfaces, a
respiratory vibration of the ring vibrator is excited by a piezoelectric transverse effect, and a
sound is emitted from the outside of the ring vibrator in general. Also, in order to protect the ring
oscillator from short circuiting by surrounding liquid, it is common to cover the sheath or to
mold it with synthetic resin for protection. An end plate is disposed on the end face of the ring
vibrator so that the liquid does not enter the inside of the ring vibrator. Also, a buffer material
such as cork or laminated paper is provided between the ring vibrator and the end plate so that
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the end plate does not inhibit the respiratory vibration of the ring vibrator. In addition, a sheath
or a mold is applied to this portion so that the surrounding fluid does not infiltrate into the inside
through the gap between the end plate and the ring oscillator.
[0009]
Further, as another method of configuring the ring vibrator, there is a method in which
rectangular piezoelectric vibrators having a substantially rectangular parallelepiped shape are
arranged in a polygonal shape through wedge blocks having a substantially triangular prism
shape to approximate a cylindrical shape. is there.
[0010]
The acoustic transducer having the above-described structure can most efficiently acoustically
reflect in the respiratory vibration mode that occurs when the cylinder length of the ring vibrator
corresponds to one wavelength of the speed of sound of the constituent material.
According to a general piezoelectric ceramic material, in the case of a cylinder having a diameter
of about 10 cm, the resonance frequency of the respiratory vibration mode is about 5 to 10 kHz.
When used at a frequency lower than this, it deviates from the resonance frequency of the ring
oscillator, so the acoustic radiation efficiency must be low.
[0011]
On the other hand, in a free flood type acoustic transducer in which water is also introduced into
the ring vibrator without providing the end plate, the resonance of the breathing vibration mode
of the ring vibrator and the resonance of water in the ring vibrator (water column resonance)
Can be used for efficient acoustic radiation.
[0012]
When the water column resonance is used at a frequency lower than the resonance frequency of
the respiratory vibration mode, the acoustic radiation efficiency must be low.
That is, since the frequency of water column resonance is determined in inverse proportion to
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the height of the cylindrical vibrating body, the resonant frequency can be designed
independently of respiratory vibration, but since the drive source is respiratory vibration mode,
both If the frequency is far away, efficient water column resonance can not be obtained. Whether
using respiratory vibration mode or water column resonance, it is necessary to increase the
diameter of the cylinder in order to be used efficiently at lower frequencies, and this results in a
large Size and mass are required. In the case of a helical structure as shown in Patent Document
2 as a conventional example, it is possible to lengthen the entire length of the coiled vibrator, and
it is possible to reduce the resonance frequency in the longitudinal direction. Due to the
structural asymmetry of the vibrating body, flexural vibration of the entire coil lower than the
resonance frequency in the longitudinal direction of the vibrating body is generated, and the
required vibration in the longitudinal direction of the coil is not necessarily radial expansion or
contraction of the cylinder. There was a problem that it did not become respiratory vibration.
[0013]
The present invention has been made in view of the above circumstances, and it is an object of
the present invention to provide an acoustic transducer capable of achieving low frequency,
small size and light weight.
[0014]
In order to solve the above-mentioned subject, the present invention provides the following
means.
That is, the acoustic transducer according to the present invention is formed by cutting out a pair
of annular members stacked in the axial direction via a buffer material, and a part of each
annular member in the circumferential direction, A first connection connecting the first end of
one of the annular members to the second end of the other annular member, with a notch
forming a first end and a second end in the member The ring vibrator is characterized by
including: a second connecting portion connecting the second end of the one annular member
and the first end of the other annular member.
[0015]
Further, the acoustic transducer according to the present invention is formed by cutting out a
plurality of annular members stacked in the axial direction via a buffer material, and a part of
each annular member in the circumferential direction, A notch portion forming a first end
portion and a second end portion in the second portion, and the first end portion of the ring
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member being the other of the ring members adjacent to one axial direction of the ring member
And a ring vibrator having a connecting portion connected to the two ends.
[0016]
According to the acoustic transducer of the present invention, the circumferential length of the
ring vibrator can be twice or more times the circumferential length of the actual diameter of the
annular member.
That is, it becomes possible to extend the propagation length of the longitudinal vibration by a
factor of two or more, and the resonance frequency of the respiratory vibration can be
significantly lowered. Therefore, the ring oscillator can realize low frequency without increasing
the diameter of the annular member. Thereby, size reduction and weight reduction can be
achieved compared with the acoustic transducer using the conventional annular member. In the
coiled form, the asymmetry causes the flexural vibration of the vibrator, but in the case of this
structure, the annular members are uniformly disposed circumferentially except for the notch
portion, and connection is made. By making the apparent mass and modulus of elasticity of the
bump identical to that of the annular portion, no flexural vibration occurs.
[0017]
It is a perspective view of a ring vibrator of an acoustic transducer concerning an embodiment. It
is a longitudinal cross-sectional view of an example of an acoustic transducer. It is a longitudinal
cross-sectional view of an example of an acoustic transducer. It is an example of the electricity
supply method to a ring vibrator. It is an example of the electricity supply method to a ring
vibrator. FIG. 5 is a perspective view of an acoustic transducer in which a plurality of ring
vibrators are stacked in the axial direction. FIG. 2 is a longitudinal cross-sectional view of an
acoustic transducer in which a pair of ring transducers are arranged coaxially and radially spaced
from each other. It is a side view of the acoustic transducer formed by laminating a plurality of
annular members.
[0018]
Hereinafter, the acoustic transducer 1 of the embodiment of the present invention will be
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described in detail with reference to the drawings. FIG. 1 is a perspective view of a ring vibrator
10 of an acoustic transducer 1 according to an embodiment. The ring vibrator 10 includes a first
annular member 20, a second annular member 30, a first connection portion 40, and a second
connection portion 50.
[0019]
The first annular member 20 and the second annular member 30 are substantially annular
members made of an elastically deformable material such as a steel material, and are stacked and
arranged in a state in which their axes O coincide with each other. Further, between the first
annular member 20 and the second annular member 30, a shock absorbing material 5 made of a
flexible material such as cork or laminated paper is provided. That is, the first annular member
20 and the second annular member 30 are laminated in the direction of the axis O with the
buffer material 5 interposed therebetween. The shock absorbing material 5 prevents the first
annular member 20 and the second annular member 30 from being mechanically coupled. The
first annular member 20 and the second annular member 30 are preferably made of a
piezoelectric ceramic alone or a piezoelectric ceramic laminate, respectively.
[0020]
The first annular member 20 and the second annular member 30 each have a cutout C formed so
that a part in the circumferential direction is cut out. That is, the first annular member 20 and
the second annular member 30 are each formed in a C shape by forming the cutout portion C,
and both ends of the C shape oppose each other in the circumferential direction. The first end 21,
31 and the second end 22, 32 are provided. The first end portions 21 and 31 of each of the first
annular member 20 and the second annular member 30 both face one side in the circumferential
direction, and the respective second ends 22 and 32 have both circumferential directions. I'm
facing the other side. In the present embodiment, the first annular member 20 and the second
annular member 30 are stacked in the direction of the axis O in a state in which the respective
cutouts C are made to coincide in the circumferential direction.
[0021]
Similar to the first annular member 20 and the second annular member 30, the first connection
portion 40 is a member made of steel or the like, and the first end portion 21 of the first annular
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member 20 and the second annular member The second ends 32 of the members 30 are
connected to one another. That is, the first connection portion 40 is connected to the first end 41
connected to the first end 21 of the first annular member 20 and the second end connected to
the second end 32 of the second annular member 30. 42 and a connecting portion 43 for
connecting the first piece 41 and the second piece 42 in the direction of the axis O.
[0022]
Similar to the first connection portion 40, the second connection portion 50 is a member made of
steel or the like, and the second end portion 22 of the first annular member 20 and the first end
portion 31 of the second annular member 30. And are connected to each other. That is, the
second connection portion 50 is connected to the first end 51 connected to the first end 32 of
the second annular member 30 and the second end connected to the second end 32 of the first
annular member 20. And a connecting portion 53 for connecting the first piece 51 and the
second piece 52 in the direction of the axis O.
[0023]
Thus, the first annular member 20 and the second annular member 30 intersect each other in
the direction of the axis O by the first connecting portion 40 and the second connecting portion
50 provided in the respective cutouts C. It is connected to A gap is formed between the first
connection portion 40 and the second connection portion 50. Moreover, it replaces with the said
clearance gap and the said shock absorbing material 5 may be arrange | positioned between
both. Furthermore, the first connection portion 40 and the second connection portion 50 are
made of a material or a structure that makes the apparent density and the elastic modulus
substantially equal to those of the first annular member 20 and the second annular member 30.
Is preferred.
[0024]
Here, in general, the respiration vibration of a single ring oscillator is determined under the
condition that longitudinal oscillation of one wavelength occurs on the circumference of the ring.
The resonant frequency of the longitudinal vibration is uniquely determined by the density and
elastic modulus of the material constituting the vibrator. Therefore, in order to realize the
resonance frequency at a lower frequency, the length corresponding to one wavelength can be
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lengthened, that is, the diameter can be realized by increasing the diameter of the oscillator
composed of a ring. However, in this case, there is a disadvantage that the size of the vibrator
itself becomes large, which hinders the downsizing.
[0025]
On the other hand, in the present embodiment, the first annular member 20 and the second
annular member 30 are stacked on each other in the direction of the axis O, and the first annular
member 20 and the second annular member 30 are arranged. Are connected by the first
connection portion 40 and the second connection portion 50 so as to cross in the direction of the
axis O. Therefore, the dimension of the circumferential direction of the ring vibrator 10 is the
sum of the first annular member 20 and the second annular member 30, that is, the case of the
first annular member 20 alone or the second annular member 30 alone It is twice the length of
the circumferential direction of This makes it possible to double the propagation length of the
longitudinal vibration and to reduce the resonance frequency of the respiratory vibration by
approximately half.
[0026]
Therefore, according to the ring vibrator 10 of the present embodiment, the first ring member 20
and the second ring member 30 are connected by intersecting the axial O direction by the first
connection portion 40 and the second connection portion 50. Thereby, a low frequency of about
1⁄2 can be realized without increasing the diameter of the first annular member 20 or the second
annular member 30. This makes it possible to reduce the size and weight.
[0027]
In addition, adjustment of a frequency can be easily performed by changing the length of the
circumferential direction of the 1st connection part 40 and the 2nd connection part 50. FIG. That
is, if the dimensions in the circumferential direction of the first connection portion 40 and the
second connection portion 50 are increased, the outer diameter of the ring vibrator 10 can be
increased and the frequency can be lowered, and the length of the second connection portion 50
Can be shortened to reduce the outer diameter of the ring vibrator 10 and to increase the
frequency.
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[0028]
For example, as shown in FIG. 2, as an acoustic transducer 1 including such a ring vibrator 10, a
pair of end plates 6 is disposed at both ends in the direction of the axis O of the ring vibrator 10
to open both ends of the ring vibrator 10. It may be closed and the synthetic resin 9 may be
molded so as to cover the entire ring oscillator 10 and the entire end plate 6. Such an acoustic
transducer 1 has a cylindrical outer shape and a hollow interior, so that sound is emitted from
the outer peripheral surface of the ring vibrator 10.
[0029]
Further, for example, as shown in FIG. 3, the acoustic transducer 1 may be configured by molding
the entire ring vibrator 10 with the synthetic resin 9. In this case, the outer shape of the acoustic
transducer 1 has a donut shape like the ring vibrator 10. In this case, the liquid flows into the
inside of the acoustic transducer 1 to form a free flood ring structure utilizing the underwater
resonance of the liquid. In these acoustic transducers 1, the ring vibrator 10 may be covered with
a sheath instead of the synthetic resin 9.
[0030]
As a method of energizing the ring vibrator 10, for example, as shown in FIG. 4, an anode 7 is
provided as an electrode on the outer peripheral surface of the first annular member 20 and the
second annular member 30, and a cathode is formed on the inner peripheral surface. Electricity
may be supplied by providing eight. For example, as shown in FIG. 5, the anode 7 is provided on
the upper surface of the first annular member 20 corresponding to the end of the ring vibrator
10 and the lower surface of the second annular member 30, and the first annular member 20 is
opposed to each other. The cathode 8 may be provided on the lower surface of the second
annular ring 30 and the upper surface of the second annular member 30.
[0031]
Furthermore, for example, as shown in FIG. 6, a plurality of ring vibrators 10 in which the first
annular member 20 and the second annular member 30 are laminated in the direction of the axis
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O may be laminated in the direction of the axis O . In this case, the buffer material 5 is provided
between the ring vibrators 10 adjacent to each other in the axis O direction. Thereby, the
dimension in the direction of the axis O can be freely set, and the water column resonance
frequency can be reduced in proportion to the dimension.
[0032]
For example, as shown in FIG. 7, a pair of ring vibrators 10 are arranged coaxially and radially
spaced from each other, and a pair of end plates 6 closing the openings at both ends of the ring
vibrators 10 is provided. In this case, by driving the inner ring vibrator 10 and the outer ring
vibrator 10 in opposite directions to each other, sound pressure generation and ring of
underwater resonance inside the ring vibrator 10 can be achieved. Efficient acoustic reflection
can be realized in which the phases of sound pressure generation from the outer surface of the
vibrator 10 are matched.
[0033]
Furthermore, for example, the acoustic transducer 1 may include the ring vibrator 10 illustrated
in FIG.
In the ring vibrator 10, three annular members 60 having the same configuration as the first
annular member 20 and the second annular member 30 are stacked in the direction of the axis O
with the buffer material 5 interposed therebetween. In addition, a notch C is formed in each of
the annular members 60, whereby the first end 61 and the second end 62 are formed in each
annular member 60. Further, the circumferential positions of the notches C of the respective
annular members 60 coincide with each other.
[0034]
Of the three annular members 60, the first end 61 of the upper annular member 60 and the
second end 62 of the lower annular member 60 are connected by the connecting portion 70.
Further, the connection portion 70 connects the second end portion 62 of the upper ring
member 60 and the first end portion 61 of the middle ring member 60 in the middle.
Furthermore, the second end 62 of the intermediate ring member 60 and the first end 61 of the
lower ring member 60 are connected by the connecting portion 70. In addition, these connection
parts 70 have comprised the structure similar to the said 1st connection part 40 and the 2nd
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connection part 50. FIG. Then, the acoustic transducer 1 is configured by laminating a plurality
(five in the present embodiment) of the ring vibrator 10 having such three ring members 60 in
the direction of the axis O with the buffer material 5 interposed therebetween. There is.
[0035]
With such a configuration, the dimension in the circumferential direction of the ring oscillator 10
is the sum of the three annular members 60, so that the propagation length of the longitudinal
vibration can be extended by the number of times of the annular members 60. Become.
Therefore, the resonant frequency of respiratory vibration can be significantly reduced. In
addition, although the ring vibrator 10 was comprised from the three ring members 60 here, it is
not limited to this, the same ring vibrator 10 is comprised from the several ring member 60 of
four or more, May be That is, the ring vibrator 10 may be configured by sequentially connecting
the annular members 60 stacked in the direction of the axis O.
[0036]
As mentioned above, although embodiment of this invention was described in detail, as long as it
does not deviate from the technical idea of this invention, it is not limited to these and some
design changes etc. are possible. For example, in the embodiment, the circumferential positions
of the notches C of the first annular member 20 and the second annular member 30 and the
circumferential positions of the notches C of the plurality of annular members 60 are made to
coincide with each other. However, the positions of the notches C may be spaced apart in the
circumferential direction. When the position of the notch C coincides with the circumferential
direction, a structurally nonuniform portion is formed, which may induce bending vibration in
addition to the respiratory vibration, but the notch C The flexural vibration can be avoided by
arranging the circumferentially spaced apart, preferably equally spaced apart.
[0037]
In addition, as the first annular member 20, the second annular member 30, and the annular
member 60, for example, a plurality of rectangular piezoelectric vibrators having a rectangular
parallelepiped shape are arrayed in an annular shape using wedge members having a triangular
prism shape It may be configured by
[0038]
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DESCRIPTION OF SYMBOLS 1 ... Acoustic transducer, 5 ... Buffer material, 6 ... End plate, 7 ...
Anode, 8 ... Cathode, 9 ... Synthetic resin, 10 ... Ring vibrator, 20 ... 1st annular member (annular
member), 30 ... The 1st Two annular members (annular members), 40: first connection portion,
41: first piece, 42: second piece, 43: connection portion, 50: second connection portion, 51: first
piece, 52: fifth Two pieces, 53 ... connection part, 60 ... ring member, 70 ... connection member, C
... notch, O ... axis
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