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JPH1198595

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JPH1198595
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is an electroacoustic transducer which emits an acoustic wave into a medium such as water or seawater, and
utilizes the resonance of a columnar medium filling the inside of the cylinder to produce a
cylinder periphery. A plurality of cylindrical transmitters emitting sound waves in the medium
are arranged in series on the same cylindrical axis, and the resonance frequency of the media
column is set by changing the arrangement interval of the plurality of cylindrical transmitters. In
particular, the present invention relates to a coupled cylindrical transmitter capable of expanding
the variable width of a resonant frequency that changes according to the arrangement interval of
the cylindrical transmitters.
[0002]
2. Description of the Related Art First, the structure and operation of a cylindrical piezoelectric
vibrator 1 will be described with reference to FIG.
[0003]
As shown in FIG. 2A, in the piezoelectric vibrator 1, the leads 2 are connected to the respective
electrodes of the inner peripheral surface 12 and the outer peripheral surface 13 of the
cylindrical piezoelectric material 11, and an electric signal is transmitted between these
electrodes The addition causes mechanical resonance, and an acoustic output can be obtained
through the surrounding medium.
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[0004]
The mechanical resonance frequency fr by the breathing mode applied to the electrodes of the
inner circumferential surface 12 and the outer circumferential surface 13 in order to obtain a
high rate of high acoustic output in the piezoelectric vibrator 1 is the sound velocity c and the
average diameter of the cylindrical piezoelectric vibrator 1 In the case of d, it is obtained by the
following equation 1.
[0005]
fr = c / πd (1) On the other hand, in the case of the piezoelectric vibrator 1 of a cylindrical wave
transmitter provided in water, the entire surface is covered with a sheath for waterproofing, but
the cylindrical wave transmitter in water is mechanically In addition to the resonance frequency
fr, as shown in FIG. 2 (B), it has an acoustic resonance frequency Fr by the water column inside
the cylindrical shape.
The acoustic resonance frequency Fr is determined by the sound velocity and the elastic modulus
of the medium flowing into the hollow portion in the cylinder, the inner radius R of the
piezoelectric vibrator 1 and the elastic modulus, and the correction coefficients α2, α3,. In
addition, α 4 is the length L of the piezoelectric vibrator 1 in the axial direction, and is obtained
by the following Equation 2 and Equation 3.
[0006]
Fr = α1 × (A−A2−α2) / 4π (2) A = α3 × L / (2R) + α4 (3) When driving the piezoelectric
vibrator 1 by the electric signal of this acoustic resonance frequency Fr, a cylinder The medium
inside resonates, and as with the mechanical resonance of the cylindrical piezoelectric vibrator 1,
an acoustic output with high efficiency can be obtained.
[0007]
Next, with reference to FIG. 3 and FIG. 4 together, the change of the resonant frequency due to
the change of the relative positional relationship of the connected cylindrical transmitters will be
described.
[0008]
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As shown in FIG. 3A, two cylindrical transmitters 21 and 22 having an axial length λ are
arranged in series at a sufficient distance a in the cylindrical axis direction, and the resonance
frequency f1 of the water column is Set to occur.
Then, from this state, when the distance a between the two cylindrical transmitters 21 and 22 is
gradually made closer to bring them into close contact as shown in FIG. 3 (B), the resonance
frequency f 1 is shown by curve C in FIG. It gradually decreases to the resonance frequency f2 so
that
[0009]
When the n cylindrical piezoelectric vibrators 1 are in close contact with each other, the axial
length λ of the cylindrical shape is n times, so that a low resonance frequency f1 / n can be
obtained as the resonance frequency as a theoretical value. .
[0010]
Conventionally, in this type of linked cylindrical transmitter, a single cylindrical transmitter 100
as shown in FIG. 5 connects the leads 2 to the inner and outer peripheral surfaces of the
cylindrical piezoelectric vibrator 1 respectively. The outer peripheral surface and both end
surfaces of the piezoelectric vibrator 1 are covered with a sheath 103 made of synthetic resin or
the like.
Although a state in which a plurality of cylindrical wave transmitters 100 are connected and
installed is not shown, it is a structure in which a medium such as fresh water or seawater can
flow into the hollow portion of each of the cylindrical wave transmitters 100.
[0011]
Therefore, at the end face contact portion of the cylindrical transmitter 100 in close contact, a
molding material made of synthetic resin or the like for watertight protection is present.
Since a molding material made of synthetic resin or the like is acoustically regarded as
substantially the same as water, an acoustic gap exists between the piezoelectric vibrators 1 even
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when the cylindrical transmitter 100 is closely attached. It is inevitable.
Therefore, the resonance frequency f1 decreases from the resonance frequency f1 as shown in
FIG. 4 and only the resonance frequency f2 can be obtained even in a close contact state, and the
change of the resonance frequency is compared with the resonance frequency f0 of the curve R
based on theoretical calculation. The range is narrower.
[0012]
SUMMARY OF THE INVENTION In the above-described conventional connected cylindrical type
wave transmitter, a single cylindrical type wave transmitter is used to protect the molding
material by the synthetic resin or the like present at the end face contact portion in close contact.
Since it can not be removed, even if the cylindrical wave transmitter is closely attached, an
acoustic gap is generated between the piezoelectric vibrators due to the presence of the molding
material by a synthetic resin or the like which is regarded as substantially the same as water
acoustically. It will be present, and there is a problem that the range of change of the water
column resonance frequency is significantly narrowed.
[0013]
The object of the present invention is to solve this problem and to protect the watertightness of
the cylindrical transmitter when changing the water column resonance frequency by changing
the arrangement interval of the cylindrical transmitters, and also to change the water column
resonance frequency. It is an object of the present invention to provide a coupled cylindrical
transmitter capable of taking a wide variation range close to the theoretical calculation value.
[0014]
SUMMARY OF THE INVENTION A coupled cylindrical transmitter according to the present
invention comprises a cylindrical transmitter that emits sound waves into the medium around the
cylinder by utilizing the resonance of the medium column filling the cylinder. A plurality of
connected cylindrical wave transmitters arranged in series on the same cylindrical axis and
variably setting the resonance frequency of the media column by changing the arrangement
interval of the cylindrical wave transmitters, wherein the cylindrical wave transmitters A sheath
having a function of insulating at least the medium covering the inner peripheral surface and the
outer peripheral surface of the cylindrical piezoelectric material, the cylindrical sheath having a
sufficiently large acoustic impedance compared to the medium, and At least both end surfaces of
the piezoelectric material are closely adhered and covered to prevent the piezoelectric material
from coming in contact with the medium, and an end plate having an insulating function with
respect to the medium is provided.
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[0015]
Furthermore, the end surface plate further includes an L-shaped collar portion which protrudes
into the sheath material at a contact surface with the sheath and has a tip in a direction opposite
to a direction in which the medium presses the sheath material. There is.
[0016]
By using a rigid body with sufficiently large acoustic impedance compared to the medium, for
example, aluminum, for the above-mentioned end plate, the degree of adhesion of the
piezoelectric vibrator is increased, and the resonance frequency when the cylindrical transmitter
is in close contact is calculated theoretically Approach the value.
In addition, the L-shaped buttocks can prevent peeling of the sheath due to resonance.
[0017]
DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention
will be described with reference to the drawings.
Although not shown in the drawings, the connected cylindrical transmitters have a structure in
which single cylindrical transmitters are aligned by means of an array fitting and the cylindrical
axes are aligned at intervals to generate a desired resonance frequency.
[0018]
FIG. 1 is a cross-sectional perspective view showing an embodiment of a single cylindrical wave
transmitter according to the present invention.
In the cylindrical wave transmitter 10 shown in FIG. 1, the lead 2 for supplying power is
connected to the cylindrical piezoelectric vibrator 1, and the entire inner and outer peripheral
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surfaces are the sheath 3, the sheath 3 and the piezoelectric Both end surfaces of the vibrator 1
are bonded by the end surface plate 4 so that the medium such as water does not enter.
By this structure, the piezoelectric vibrator 1 is covered with the sheath 3 and the end surface
plate 4 over the entire surface.
[0019]
The sheath 3 is formed of a mold such as a synthetic resin, and the end plate 4 is a material
having a sufficiently large acoustic impedance than a medium such as water, for example, a rigid
body such as aluminum.
[0020]
The end plate 4 has a size that covers both end surfaces of the cylindrical piezoelectric vibrator 1
and the sheath 3 and is in close contact with the sheath 3 covering the inner peripheral surface
and the outer peripheral surface of the piezoelectric vibrator 1 respectively. On the surface, an Lshaped collar 5 whose tip is directed in the direction opposite to the external pressure is
provided in a state where it is bitten into the sheath 3.
[0021]
Next, the functional operation will be described with reference to FIG. 1 together with FIG. 2 to
FIG.
[0022]
As shown in FIG. 3 (A), when two cylindrical transmitters 10 are arranged at a sufficiently
separated position and a voltage is applied to the piezoelectric vibrator 1, as shown in FIG. 2 (B)
The piezoelectric vibrator 1 breathes and vibrates, and a water column resonance occurs in
which both ends of the cylinder are antinodes of the vibration in the cylinder.
[0023]
The resonance frequency Fr at this time is determined by the length of the cylinder formed by
the laminated and bonded piezoelectric vibrator 1 and the end surface plate 4 according to the
above-mentioned equation (2).
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When the arrangement interval of the two cylindrical transmitters 10 is reduced from FIG. 3 (A)
to FIG. 3 (B) in close contact, the amount of sound leaking from between the two cylindrical
transmitters 10 is reduced, The resonance frequency is lowered as it approaches structural
integration.
[0024]
When the facing end plates 4 of the two cylindrical transmitters 10 are in close contact and have
no gap, there is no gap acoustically, and the oscillation frequency f3 in this state is as shown by
the curve I shown in FIG. The resonance frequency f1 / 2 = f0 of the theoretical calculation value
determined by the total cylinder length 2L obtained by superposing the two cylindrical
transmitters 10 approaches as close as possible.
[0025]
Therefore, the variable range of the water column resonance frequency in the coupled cylindrical
transmitters extends from the resonance frequency f1 to approximately the resonance frequency
f1 / 2.
[0026]
In addition, when water pressure is applied to the linked cylindrical transmitter in water, the
sheath of a molding material such as a synthetic resin for protecting the watertightness of each
of the plurality of cylindrical transmitters constituting the connected cylindrical transmitter is
subjected to external pressure. It is compressed because it receives and compresses, but on the
surface of the end face plate in close contact with the sheath, the L-shaped collar with its tip
facing in the direction opposite to the external pressure bites into the sheath. The sheath does
not get caught on the buttocks and peel off.
Therefore, the watertightness of the coupled cylindrical transmitter can be maintained.
[0027]
In the above description, a cylindrical transmission with two cylindrical transmissions has been
described, but the above-described function can be similarly exhibited in a plurality of cases in
which more than two transmissions are used.
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[0028]
In the above description, the end face plate is illustrated so as to just cover the both end faces of
both the sheath and the piezoelectric vibrator, but the inner diameter is smaller than the inner
diameter of the sheath and the outer diameter is larger than the outer diameter of the sheath It is
also good.
[0029]
Although in the above description, the leads are illustrated as being connected to the inner and
outer peripheral surfaces of the piezoelectric vibrator, this connection structure is illustrated for
the convenience of the description and limits the present invention It is not something to do.
As described above, although the above description is made with reference to the drawings, the
structure is free as long as the above function is satisfied, and the above description does not
limit the present invention.
[0030]
As described above, according to the present invention, by means of an extremely simple
structure, a plurality of cylindrical wave transmitters are connected, and by changing their
intervals, the variable range in which the resonance frequency is variably set is theoretically A
coupled cylindrical transmitter can be obtained which can be expanded to near the calculated
value.
[0031]
The reason is that the gap to which the arranged cylindrical transmitters are in close contact is
filled with an end plate having a material whose acoustic impedance is sufficiently larger than
that of a medium such as water.
[0032]
Also, for this structure, in order to increase the degree of sealing with respect to the piezoelectric
vibrator, that is, the adhesion between the end surface plate and the sheath, and to prevent the
sheath from peeling off the piezoelectric vibrator, a direction opposite to the external pressure
An L-shaped buttock with its tip facing is provided in a state of biting into the sheath.
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[0033]
Brief description of the drawings
[0034]
1 is a cross-sectional perspective view showing an embodiment of a single cylindrical transmitter
according to the present invention.
[0035]
2 is a perspective view (A) and a sectional view (B) showing an example of a piezoelectric
vibrator for explaining the resonance frequency of the cylindrical transmitter.
[0036]
3 is an explanatory view showing an example of the positional relationship between two
cylindrical transmitters.
[0037]
4 is an output characteristic diagram curving the resonance frequency corresponding to the
positional relationship of the plurality of cylindrical transmitters.
[0038]
5 is a cross-sectional perspective view showing an example of a conventional single-piece
cylindrical transmitter.
[0039]
Explanation of sign
[0040]
Reference Signs List 1 piezoelectric vibrator 2 lead 3 sheath 4 end surface plate 5 ridge portion
10 cylindrical wave transmitter
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