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JP2006261728

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2006261728
PROBLEM TO BE SOLVED: To eliminate the need for a DC bias power supply for applying a DC
bias voltage between a vibrating membrane and a fixed electrode, and to uniformly make a large
number of fine holes at a fixed depth on the surface of the fixed electrode. An ultrasonic
transducer is provided which can make work unnecessary. An ultrasonic transducer for
generating an ultrasonic signal by vibration of a vibrating membrane, the flat single support
member having a plurality of through holes for transmitting vibration sound of the vibrating
membrane; A vibrating membrane including a first electrode layer crimped to one surface of the
supporting member, and a pressure means for applying pressure to the vibrating membrane and
crimping the vibrating membrane to the surface of the supporting member An alternating
current for applying an alternating current signal between a second electrode layer arranged to
face a surface on the side to be pressurized of the vibrating membrane, and the first electrode
layer and the second electrode layer And signal applying means. [Selected figure] Figure 1
Ultrasonic transducer
[0001]
The present invention relates to an ultrasonic transducer, and in particular, an electrostatic type
that does not require a DC bias power supply for applying a DC bias voltage between a vibrating
membrane and a fixed electrode, and can reduce processing costs. The present invention relates
to an ultrasonic transducer.
[0002]
Electrostatic ultrasonic transducers (electrostatic transducers) are conventionally known as
broadband ultrasonic transducers capable of generating high sound pressure over high
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frequency bands.
[0003]
FIG. 6 shows an example of an electrostatic ultrasonic transducer.
The ultrasonic transducer 20 shown in FIG. 6 is opposed to the vibrating film 21 formed of an
insulating film 21B formed of an insulator and an electrode layer 21A formed on the insulating
film 21B, and the insulating film 21B of the vibrating film 21. A fixed electrode (lower electrode)
22 in which a plurality of irregularities are formed on the surface, a DC bias power supply 24
and a signal source 25 are included.
[0004]
A constant DC bias voltage is always applied between the electrode layer 21A of the vibrating
membrane 21 and the fixed electrode 22 by the DC bias power supply 24 capable of voltage
adjustment, and the fixed electrode 22 is generated by the electrostatic force generated by this
electric field. The vibrating membrane 21 is adsorbed to the convex portion 22A, and the hollow
portion 23 formed between the vibrating membrane 21 and the fixed electrode 22 is in close
contact.
In addition, an alternating current signal (the frequency is an ultrasonic frequency band of 20
kHz or more) which is a signal voltage by the signal source 25 in a state of being superimposed
on the direct current bias voltage by the direct current bias power supply 24 between the
diaphragm 21 and the fixed electrode 22. Is to be applied.
[0005]
In the above configuration, when a DC bias voltage is applied between the electrode layer 21A of
the diaphragm 21 and the fixed electrode 22 by the DC bias power supply 24, the diaphragm 21
is attracted to the convex portion 22A of the fixed electrode 22, In this state, an alternating
current signal is applied from the signal source 25 between the vibrating film 21 (electrode layer
21A) and the fixed electrode 22 in a superimposed manner on the direct current bias voltage.
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Thereby, the electrostatic attraction between the vibrating membrane 21 and the fixed electrode
22 is changed by the alternating current signal, and the vibrating membrane 21 is driven by the
alternating current signal to vibrate.
[0006]
As described above, the ultrasonic transducer 20 shown in FIG. 6 is called a pull type because the
vibrating membrane 21 vibrates by receiving a suction force from the fixed electrode 22.
[0007]
However, in the pull-type ultrasonic transducer shown in FIG. 6, in order to cause the vibrating
membrane 21 which is a thin film to be in close contact with the convex portion of the fixed
electrode 22, a high voltage direct current is applied between the vibrating membrane 21 and
the fixed electrode 22. There is a need for a DC bias power supply 24 for applying a bias voltage.
In addition, in order to realize the vibration of the ultrasonic band, it is necessary to set the hole
diameter of the hollow portion 23 in which the vibrating film 21 vibrates to several mm or less.
For this reason, it is necessary to make a large number of fine holes uniformly at a fixed depth on
the surface of the fixed electrode 22, which causes an increase in cost due to the hole processing.
[0008]
In addition, the prior art about an ultrasonic transducer is disclosed (for example, refer patent
document 1, 2). The prior art of Patent Document 1 aims to provide a parametric audio system
having a carrier frequency that is sufficiently higher than the carrier frequency of the
conventional system, with reduced distortion and improved efficiency. Further, the prior art of
Patent Document 2 aims to provide a transducer which is efficient and has a wide operating
band. However, the present invention is intended to solve the problem that a DC bias power
source is required to bring the vibrating film, which is a thin film, into close contact with the
fixed electrode, and the cost problem of drilling holes in the vibrating portion. The present
invention and the prior art have different purposes and configurations of the invention. Japanese
Patent Laid-Open No. 2000-50387 Japanese Patent Laid-Open No. 2000-50392
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[0009]
As described above, the conventional ultrasonic transducer shown in FIG. 6 requires a DC bias
power supply for applying a DC bias voltage between the vibrating membrane and the fixed
electrode. Moreover, since it is necessary to make many fine holes of a fixed depth on the surface
of the fixed electrode (lower electrode), the processing cost is increased.
[0010]
The present invention has been made to solve the above problems, and an object of the present
invention is to eliminate the need for a DC bias power supply for applying a DC bias voltage
between a vibrating membrane and a fixed electrode, and to fix the same. An object of the
present invention is to provide an ultrasonic transducer which can eliminate the task of
uniformly opening a large number of fine holes at a fixed depth on the surface of an electrode.
[0011]
In order to achieve the above object, an ultrasonic transducer according to the present invention
is an ultrasonic transducer that generates an ultrasonic signal by vibration of a vibrating film,
and is a flat plate having a plurality of through holes transmitting vibration sound of the
vibrating film. And a vibrating membrane including a first electrode layer crimped to one surface
of the single supporting member, and a pressure applied to the vibrating membrane, the
vibrating membrane being the supporting member A second electrode layer disposed to face the
surface of the vibrating membrane on which pressure is applied, the first electrode layer, and the
second electrode And alternating current signal application means for applying an alternating
current signal between the layers.
In the ultrasonic transducer configured as described above, the pressing means is used to press
the vibrating membrane against the support member in which the plurality of through holes are
formed, and the portion where the vibrating membrane protrudes from the through hole is
vibrated and ultrasonic waves are generated. Make it happen. Then, an alternating current signal
is applied between the first electrode layer formed on the vibrating film and the second electrode
layer facing the vibrating film to vibrate the vibrating film to generate an ultrasonic wave.
Therefore, although the conventional ultrasonic transducer requires a DC bias power supply for
applying a DC bias voltage between the vibrating membrane and the fixed electrode, the
ultrasonic transducer of the present invention requires the use of a DC bias power supply. There
is no Further, in the ultrasonic transducer of the present invention, unlike the prior art, it is not
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necessary to form a large number of minute holes on the surface of the fixed electrode, so that
the processing cost can be reduced.
[0012]
In the ultrasonic transducer according to the present invention, the pressurizing means is a
support film which is filled with a gas to form an elastic body, the support film is pressed against
the vibrating film, and the pressure of the gas in the support film The vibrating membrane is
configured to be pressure-bonded to the support member. In the ultrasonic transducer
configured as described above, the vibration film is pressed against the support member using a
support film (for example, a disk-like support film) which is an elastic body filled with a gas, and
the pressure of the gas in the support film The diaphragm is crimped to the support member by
the Therefore, the vibrating membrane can be pressure-bonded to the support member without
using a direct current bias power supply and without using an adhesive or the like, and the
configuration of the ultrasonic transducer can be simplified. In addition, in the through hole
portion of the support member, the vibrating membrane can be stretched without difficulty and
can be vibrated in accordance with the alternating current signal.
[0013]
The ultrasonic transducer of the present invention is characterized in that the second electrode
layer is formed in a portion in contact with the vibrating membrane of the support membrane. In
the ultrasonic transducer configured as described above, an electrode layer is formed of a
conductive material such as aluminum foil on the upper portion of a support film (for example, a
disk-like support film) which is an elastic body filled with a gas. An alternating current signal is
applied between the electrode layer and the electrode layer of the vibrating membrane.
Therefore, the ultrasonic transducer can be configured without using a fixed electrode. Therefore,
the configuration of the ultrasonic transducer can be further simplified.
[0014]
Further, in the ultrasonic transducer according to the present invention, the second electrode
layer is a fixed electrode formed of a conductive material or a fixed electrode including a
conductive layer, and the second electrode layer is a fixed electrode including the conductive
layer. A pressure means is arranged. In the ultrasonic transducer configured as described above,
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the second electrode layer is used as a fixed electrode, and a pressing means such as an elastic
body filled with gas is disposed between the fixed electrode and the support film, and The
pressure means is pressed against the vibrating membrane from the fixed electrode side, and the
vibrating membrane is crimped to the support member. Therefore, the vibrating membrane can
be crimped to the support member without using a direct current bias power supply and without
using an adhesive or the like, and the assembly process of the ultrasonic transducer can be
simplified. In addition, in the through hole portion of the support member, the vibrating
membrane can be stretched without difficulty and can be vibrated in accordance with the
alternating current signal.
[0015]
Further, in the ultrasonic transducer according to the present invention, the pressing means is
formed by a closed space between the vibrating membrane and the fixed electrode, and the
pressure in the closed space crimps the vibrating membrane to the support member. It is
characterized in that In the ultrasonic transducer configured as described above, the second
electrode layer is used as a fixed electrode, and the fixed electrode and the support film form a
closed space, and the pressure in the closed space is pressurized to support the vibrating film as
a support member. Crimp to Therefore, the vibrating membrane can be crimped to the support
member by adjusting the pressure in the closed space without using a direct current bias power
supply and without using an adhesive or the like.
[0016]
Next, the best mode for carrying out the present invention will be described with reference to the
drawings. FIG. 1 is a view showing a configuration example of an ultrasonic transducer of the
present invention. The ultrasonic transducer 1 shown in FIG. 1 includes a single circular flat
support member 2, a vibrating membrane 3 disposed on the lower surface of the supporting
member 2, and a lower surface of the vibrating membrane 3 filled with a gas such as air. A
cylindrical support film (pressurizing means) 4 formed of an elastic material to be formed, and a
lower support member 5 disposed on the lower surface of the support film 4. Note that the
support member 2 is provided with a plurality of through holes 2A that form the shape of the
vibration hole. Further, an electrode layer (second electrode layer) 4A is formed on the upper
surface of the vibrating film 4 by aluminum foil or the like.
[0017]
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Then, the vibrating membrane 3 and the support membrane 4 are sandwiched between the
support member 2 and the lower support member 5, and the frame members 6 and 7 apply
pressure to the support member 2 and the lower support member 5 vertically in the figure, The
vibrating membrane 3 is pressed against the supporting member 2 by 4 and the vibrating
membrane 3 is crimped to the supporting member 2 and fixed.
[0018]
As the vibrating film 3, a dielectric (insulator) such as PET (polyethylene terephthalate resin)
having a thickness of about 3 to 20 μm is used.
[0019]
FIG. 2 is a view showing a cross section of the vibrating membrane 3.
As shown in FIG. 2, the vibrating film 3 is configured to cover the whole of the electrode layer
(first electrode layer) 3A with insulating films 3B and 3C such as PET.
[0020]
Moreover, as a material used for the supporting member 2, inorganic materials, such as resin,
glass, ceramic, iron, and copper, and organic materials, such as acrylic resin, polystyrene resin,
polyacetal resin, polycarbonate resin, etc. can be used.
Further, by configuring the hole diameter radius of the through hole 2A of the support member 2
to be about 450 μm to 1050 m, it is possible to configure an ultrasonic transducer having a
sound pressure peak around 40 kHz to 50 kHz.
[0021]
FIG. 3 is a view schematically showing a cross section of the ultrasonic transducer shown in FIG.
As shown in FIG. 3, the vibrating membrane 3 is pressed against the supporting member 2 by the
supporting membrane 4 which is an elastic body filled with a gas such as air, and the vibrating
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membrane 3 in the through hole 2A of the supporting member 2. A part of 3 projects, and this
overhang part 31 vibrates to generate an ultrasonic wave.
[0022]
The theoretical formula of the resonant frequency of the portion of the through hole 2A of the
vibrating membrane 3 is expressed by the following equation. f = (unm / 2πa) √ (T / ρ), where
f is a resonance frequency (Hz), a is a hole radius (m), and unm is a solution of Bessel function Jo
(x) (2.405, 5.520,...・), Ρ is density (kg / m ^ 3) ... 1.39 E + 03 (PET), T is stress (Pa) ... 3.17 E +
06 (PET).
[0023]
For example, when PET (polyethylene terephthalate resin) is used as the vibrating membrane, the
hole radius radius corresponding to the primary resonance frequency or the secondary
resonance frequency is 450 μm to 1050 μm to make the sound pressure peak around 40 kHz
to 50 kHz. It becomes a small vibration hole.
[0024]
FIG. 4 is a diagram showing an example of a circuit configuration for driving electrostatic force of
the diaphragm.
As described above, the vibrating film 3 is formed of an insulator such as PET (polyethylene
terephthalate resin) having a thickness of about 3 to 20 μm, and has the electrode layer 3A
formed of a conductive material such as aluminum foil inside. doing. In addition, an electrode
layer 4A is formed on the upper surface of the support film 4 (the surface in contact with the
vibrating film 3) with a conductive material such as aluminum foil.
[0025]
In the above configuration, in the ultrasonic transducer 1, an alternating current signal output
from a signal source (AC signal application unit) 8 is applied to the electrode layer 3 A of the
vibrating film 3 and the electrode layer 4 A of the support film 4. Note that this alternating
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current signal is a signal obtained by amplitude-modulating the ultrasonic carrier wave by an
acoustic signal in the audible band.
[0026]
As a result, in the positive half cycle of the alternating current signal output from the signal
source 8, the positive voltage of the alternating current signal is applied to the electrode layer 3A
of the vibrating film 3, and the alternating current signal is applied to the electrode layer 4A of
the support film 4. Because a negative voltage is applied, the portion of through hole 2A of
vibrating membrane 3 is attracted by electrostatic attraction in the direction of support
membrane 4 due to the potential difference between electrode layer 3A and electrode layer 4A,
and Displace in the direction. When the alternating current signal becomes zero, the potential
difference between the electrode layer 3A and the electrode layer 4A disappears, the electrostatic
attraction does not act, and the vibrating membrane 3 is pulled upward in the figure by the
elastic restoring force.
[0027]
Next, for the negative half cycle of the alternating current signal output from the signal source 8,
the negative voltage of the alternating current signal is applied to the electrode layer 3A of the
vibrating film 3, and the alternating current signal is applied to the electrode layer 4A of the
support film 4. Because a positive voltage is applied, the portion of the through hole 2A of the
vibrating membrane 3 is attracted in the direction of the support membrane 4 by electrostatic
attraction due to the potential difference between the electrode layer 3A and the electrode layer
4A. Displace. When the alternating current signal becomes zero, the potential difference between
the electrode layer 3A and the electrode layer 4A disappears, the electrostatic attraction does not
act, and the vibrating membrane 3 is pulled upward in the figure by the elastic restoring force.
[0028]
In this manner, the portion of the through hole 2A of the diaphragm 3 vibrates up and down in
the figure according to the change of the AC signal to generate an acoustic signal at a sound
pressure level sufficient to obtain the parametric array effect. Can.
[0029]
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In the example described above, the gas filled in the support film 4 is not limited to air, and may
be another gas.
Moreover, it is also possible to comprise the whole (external and internal) of the support film 4
with elastic bodies, such as rubber | gum.
[0030]
With the above configuration, the vibrating membrane 3 is crimped to the supporting member 2
by the supporting film 4 without using a direct current bias power source as in the conventional
ultrasonic transducer shown in FIG. 6 and without using an adhesive or the like. be able to. In
addition, in the portion of the through hole 2A of the support member 2, the vibrating membrane
13 can be stretched without difficulty and can be vibrated in accordance with the AC signal.
Furthermore, in the ultrasonic transducer according to the present invention, unlike the
conventional ultrasonic transducer shown in FIG. 6, it is not necessary to make a large number of
small holes in the surface of the fixed electrode, so that the processing cost can be reduced.
[0031]
Moreover, FIG. 5 is a figure which shows the other structural example of the ultrasonic
transducer of this invention. The example of the ultrasonic transducer 1a shown in FIG. 5A is an
example in which a closed space (pressurizing means) 11 is provided between the vibrating
membrane 13 and the fixed electrode (second electrode layer) 10. In the vibrating film 13, an
electrode layer (first electrode layer) 13A is formed on the insulating film 13B by a conductive
material such as aluminum foil. The fixed electrode 10 is formed of a metal material or formed so
as to include an electrode layer.
[0032]
According to the above configuration, the air pressure in the closed space 11 is pressurized by
the pressurizing device 12 and pressure is applied to the vibrating membrane 13 in the direction
of the supporting member 2 to press the vibrating membrane 13 against the supporting member
2 for pressure bonding. When the vibrating membrane 13 is pressure-bonded to the supporting
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member, the vibrating membrane 13 enters the through hole 2A portion of the supporting
member 2 in the portion of the through hole 2A of the vibrating membrane 13 as shown in FIG.
It becomes a shape (a shape in which the vibrating membrane 13 protrudes).
[0033]
In the above configuration, an alternating current signal output from the signal source 8 is
applied to the electrode layer 13A of the vibrating membrane 13 and the fixed electrode 10.
[0034]
As a result, in the positive half cycle of the alternating current signal output from the signal
source 8, the positive voltage of the alternating current signal is applied to the electrode layer
13A of the diaphragm 13, and the negative voltage of the alternating current signal is applied to
the fixed electrode 10 Due to the potential difference between the electrode layer 13A and the
fixed electrode 10, the portion of the through hole 2A of the vibrating film 13 is attracted to the
fixed electrode 10 by the electrostatic attraction force and is displaced downward in the figure in
order to be applied. .
Then, when the AC signal becomes 0, the potential difference between the electrode layer 13A
and the fixed electrode 10 disappears, the electrostatic attraction does not act, and the vibrating
membrane 13 is pulled upward in the figure by the elastic restoring force.
[0035]
Next, for the negative half cycle of the alternating current signal output from the signal source 8,
the negative voltage of the alternating current signal is applied to the electrode layer 13A of the
vibrating film 13, and the positive voltage of the alternating current signal is applied to the fixed
electrode 10 Because of the potential difference between the electrode layer 13A and the fixed
electrode 10, the portion of the through hole 2A of the vibrating membrane 13 is attracted
toward the fixed electrode 10 by electrostatic attraction and displaced downward in the figure.
Then, when the AC signal becomes 0, the potential difference between the electrode layer 13A
and the fixed electrode 10 disappears, the electrostatic attraction does not act, and the vibrating
membrane 13 is pulled upward in the figure by the elastic restoring force.
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[0036]
In this manner, the portion of the through hole 2A of the diaphragm 13 vibrates up and down in
the figure according to the change of the AC signal to generate an acoustic signal of a sound
pressure level sufficient to obtain the parametric array effect. Can.
[0037]
With the above configuration, the pressure in the closed space 11 is made higher than the
ambient air pressure without using a DC bias power source as in the conventional ultrasonic
transducer shown in FIG. 6 and without using an adhesive or the like. Thus, the vibrating
membrane 13 can be pressed against the support member 2 and pressure-bonded.
In addition, in the portion of the through hole 2A of the support member 2, the vibrating
membrane 13 can be stretched without difficulty and can be vibrated in accordance with the AC
signal.
[0038]
In the configuration example shown in FIG. 5, instead of pressing the vibrating membrane 13
against the supporting member 2 by the closed space 11, the vibrating membrane 13 may be
bonded to the supporting member 2.
[0039]
As mentioned above, although the embodiment of the present invention was described, the
ultrasonic transducer of the present invention is not limited only to the example of the abovementioned illustration, and various changes can be added in the range which does not deviate
from the gist of the present invention. Of course.
[0040]
The figure which shows the structural example of the ultrasonic transducer of this invention.
The figure which shows the cross section of a vibrating membrane.
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FIG. 2 is a cross-sectional view of the ultrasonic transducer shown in FIG. FIG. 7 is a diagram
showing an example of a circuit configuration for driving electrostatic force of a vibrating
membrane. The figure which shows the other structural example of an ultrasonic transducer. The
figure which shows the example of the conventional ultrasonic transducer.
Explanation of sign
[0041]
DESCRIPTION OF SYMBOLS 1, 1a ... Ultrasonic transducer, 2 ... Support member, 2A ... Through
hole, 3, 13 ... Vibrating film, 3A, 13A ... Electrode layer, 3B, 3C, 13B ... Insulating film, 4: Support
film, 4A ... Electrode layer 5, lower support member 6, 7, frame member 8, signal source 10, fixed
electrode 11, closed space 12, pressure device
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