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DESCRIPTION JP2009118093
In a pull-type electrostatic transducer, electrostatic force can be efficiently transmitted to a
vibrating membrane to increase the amplitude of the vibrating membrane, and sound pressure
can be further increased by using a resonance tube. , Provide an electrostatic transducer. A
vibrating membrane having a vibrating electrode layer is disposed on one side of the vibrating
membrane, and a voltage applied between the vibrating membrane and the vibrating membrane
is applied to one side of the vibrating membrane. And an electrode for applying an electrostatic
attraction force, wherein the electrode is configured such that the electrostatic attraction force
acts on a central portion of the vibrating portion of the vibrating membrane, and a sound wave
generated from the vibrating membrane And a resonant tube structure that acts as a resonant
tube. [Selected figure] Figure 1
Electrostatic transducer and ultrasonic speaker
[0001]
The present invention relates to an electrostatic transducer and an ultrasonic speaker capable of
increasing the sound pressure of a sound wave to be output by efficiently transmitting
electrostatic force to a vibrating film to increase the amplitude of vibration.
[0002]
As an electrostatic transducer used for an ultrasonic speaker etc., there is an electrostatic
transducer called a pull type.
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In addition, the electrostatic transducer which radiates ¦ emits the sound wave of ultrasonic
frequency is also called an electrostatic ultrasonic transducer.
[0003]
FIG. 18 is a view showing a configuration example of a conventional pull-type electrostatic
ultrasonic transducer (see, for example, Patent Document 1). The electrostatic ultrasonic
transducer 101 shown in FIG. 18 includes an upper electrode 110 including a vibrating film 102
formed of an insulator and a conductive film 103 formed on the vibrating film 102, and a
vibrating film 102 of the upper electrode 110. The lower electrode 120 is provided with a
plurality of concavities and convexities on the surface opposite to the DC bias power supply 130,
and an AC signal source 131.
[0004]
A constant DC bias voltage is always applied between the upper electrode 110 and the lower
electrode 120 by the DC bias power supply 130 capable of voltage adjustment, and the convex
portion A of the lower electrode 120 is generated by the electrostatic force generated by this
electric field. The upper electrode 110 is adsorbed on the upper electrode 110, and except for
the cavity B formed between the upper electrode 110 and the lower electrode 120, the upper
electrode 110 is in close contact. In this state, an alternating current signal is superimposed on
the DC bias voltage and applied between the upper electrode 110 and the lower electrode 120,
thereby facing the electrode portion of the upper electrode 110 and the lower electrode 120 (the
vibrating portion of the diaphragm 102). An electrostatic force acts on the surface 121, and the
vibrating membrane 102 is driven by an alternating current signal and vibrates by the
electrostatic attraction force and the elastic restoring force.
[0005]
As described above, the electrostatic ultrasonic transducer 101 shown in FIG. 18 is called a pull
type electrostatic ultrasonic transducer because the vibrating membrane 102 receives an
electrostatic attraction force from one direction. The advantage of this pull-type electrostatic
ultrasonic transducer is that the aperture area is large and the sound pressure can be easily
obtained.
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[0006]
In the above-described electrostatic ultrasonic transducer 101, it is generally necessary to
increase the amplitude of the vibrating film 102 in order to increase the sound pressure.
However, in the conventional pull-type electrostatic ultrasonic transducer, as shown in FIG. 19A,
the electrostatic force acting between the lower electrode 120 and the vibrating membrane 102
is the end of the vibrating portion of the vibrating membrane 102. The electrostatic force is
generated only in the unit. Therefore, compared to the configuration in which the electrostatic
force is generated at the central portion of the vibrating portion of the vibrating film 102 as
shown in FIG. 19B, the vibrating film 102 is efficiently vibrated and thus no force is applied. It
was For this reason, there is a problem that the electrostatic force can not be efficiently
transmitted to the vibrating film 102 to increase the amplitude.
[0007]
FIG. 20 is a view showing another configuration example of a pull-type electrostatic ultrasonic
transducer (see, for example, Patent Document 2). In the pull-type electrostatic ultrasonic
transducer 201 shown in FIG. 20, the upper electrode 210 composed of the vibrating film 202
formed of an insulator and the conductive film 203 formed on the vibrating film, and the
vibrating film 202 The lower electrode 220 has a plurality of concavities and convexities formed
on the opposite surface, the upper electrode and the lower electrode are in close contact with
each other, and an alternating current signal is applied between the upper electrode and the
lower electrode. There is. In addition, a resonance pipe unit 240 having a plurality of vent holes
242 forming a both-end opening pipe resonating at a desired frequency on the plate member
241 is fixed on the surface of the upper electrode 210.
[0008]
In this electrostatic ultrasonic transducer 201, the resonance pipe unit 240 is used to increase
the sound pressure. However, since the lower electrode 220 is merely uneven, even if the
vibrating film 202 vibrates. By the fact that the air does not escape from the lower electrode 220
side, the air resistance when the vibrating membrane 202 vibrates becomes large. Conversely,
when the unevenness is simply a through hole, the electrostatic force generated between the
lower electrode and the upper electrode is only at the end of the through hole, and like the
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electrostatic ultrasonic transducer 101 shown in FIG. Electrostatic force can not be efficiently
applied to the central portion of the membrane. Therefore, sufficient sound pressure could not be
obtained. JP, 2005-117103, A JP, 2005-223820, A
[0009]
In an electrostatic transducer, it is generally necessary to increase the amplitude of the vibrating
film in order to increase the sound pressure. However, in the conventional pull-type electrostatic
transducer, the electrostatic force can not be efficiently applied to the central portion of the
vibrating portion of the vibrating membrane, and a force is applied to efficiently vibrate the
vibrating membrane. There was no configuration. For this reason, there has been a problem that
the electrostatic force can not be efficiently transmitted to the vibrating membrane to increase
the amplitude of the vibrating membrane.
[0010]
The present invention has been made to solve such a problem, and an object thereof is to
effectively transmit an electrostatic force to a vibrating membrane to increase the amplitude of
the vibrating membrane in a pull-type electrostatic transducer. It is an object of the present
invention to provide an electrostatic transducer and an ultrasonic speaker which can further
increase sound pressure by using a resonance tube.
[0011]
The present invention has been made to solve the above problems, and the electrostatic
transducer according to the present invention has a vibrating membrane having a vibrating
electrode layer, a plurality of through holes, and a space between the vibrating membrane and
the vibrating membrane. An electrode that exerts an electrostatic attraction force on one surface
side of the vibrating film by an applied voltage, and a vibrating unit disposed between the
electrode and the vibrating film to divide the vibrating film into a plurality of vibrating portions A
dividing member, wherein the electrode is configured to exert an electrostatic attraction force on
a central portion of a vibrating portion of the vibrating membrane, and as a resonance tube for
sound waves generated from the vibrating membrane Characterized in that it comprises a
working resonance tube structure.
In the electrostatic transducer according to the present invention having the above configuration,
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the vibration film having the vibration electrode layer is disposed on one side of the vibration
film, and the vibration is generated by a voltage applied between the vibration film and the
vibration film. And an electrode for applying an electrostatic attraction force to one surface side
of the membrane, wherein the electrode is configured such that the electrostatic attraction force
acts on a central portion of the vibrating portion of the vibrating membrane. It has a resonance
tube structure which acts as a resonance tube with respect to the sound wave generated from the
said vibrating film, It is characterized by the above-mentioned. As a result, the electrostatic force
is generated at the central portion of the vibrating portion of the vibrating membrane, and a
force for efficiently vibrating the vibrating membrane can be applied. Moreover, the sound
pressure of the radiated sound wave can be increased by the resonance tube action. Therefore, it
is possible to realize an electrostatic transducer that can obtain high efficiency and high sound
pressure.
[0012]
Further, in the electrostatic transducer according to the present invention, a DC bias power
supply is applied to the vibrating electrode layer, and a carrier wave of an ultrasonic frequency
band is modulated with a signal wave of an audible frequency band between the vibrating
electrode layer and the electrode portion. And the electrostatic transducer is an electrostatic
ultrasonic transducer that emits ultrasonic waves. In the electrostatic transducer of the present
invention configured as described above, the electrostatic transducer according to the present
invention is used as an electrostatic ultrasonic transducer, and a modulated wave in which a
carrier wave in the ultrasonic frequency band is modulated by a signal wave in the audio
frequency band Thus, in the electrostatic ultrasonic transducer, the vibrating membrane can be
efficiently vibrated, and the sound pressure of the radiated sound wave can be increased by the
resonance tube action.
[0013]
In the electrostatic transducer according to the present invention, an electrostatic force is
generated by a voltage applied between a vibrating membrane having a vibrating electrode layer,
a plurality of through holes and the vibrating membrane adjacent to the through holes. And a
vibrating portion dividing member disposed between the electrode and the vibrating membrane
to divide the vibrating membrane into a plurality of vibrating portions, and in the plurality of
vibrating portions, the vibrating portion The electrode portion is located at a position opposite to
the central portion, and has a plurality of through holes on the surface of the vibrating film
opposite to the electrode side to act as a resonance tube for sound waves generated from the
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vibrating portion And a resonant tube member is disposed. In the electrostatic transducer of the
present invention configured as described above, the vibrating membrane and the electrode are
disposed so as to sandwich the vibrating portion dividing member (for example, the epoxy resin
layer). Then, when the vibrating membrane is attracted to the electrode by electrostatic force,
there is an electrode portion that generates an electrostatic force with respect to the central
portion of the vibrating portion of the vibrating membrane. In addition, on the side opposite to
the electrode side of the vibrating membrane, a resonance tube member having a through hole
that acts as a resonance tube for the sound wave generated from the vibrating portion of the
vibrating membrane is disposed. As a result, an electrostatic force is generated at the central
portion of the vibrating portion in which the vibrating membrane vibrates, and a force for
efficiently vibrating the vibrating membrane can be applied. Moreover, the sound pressure of the
radiated sound wave can be increased by the resonance tube action. Therefore, it is possible to
realize an electrostatic transducer that can obtain high efficiency and high sound pressure.
[0014]
Further, in the electrostatic transducer according to the present invention, a DC bias power
supply is applied to the vibrating electrode layer, and a carrier wave of an ultrasonic frequency
band is modulated with a signal wave of an audible frequency band between the vibrating
electrode layer and the electrode portion. And the electrostatic transducer is an electrostatic
ultrasonic transducer that emits ultrasonic waves. In the electrostatic transducer of the present
invention configured as described above, the electrostatic transducer according to the present
invention is used as an electrostatic ultrasonic transducer, and a modulated wave in which a
carrier wave in the ultrasonic frequency band is modulated by a signal wave in the audio
frequency band Thus, in the electrostatic ultrasonic transducer, the vibrating membrane can be
efficiently vibrated, and the sound pressure of the radiated sound wave can be increased by the
resonance tube action.
[0015]
In the electrostatic transducer according to the present invention, an electrostatic force is
generated by a voltage applied between a vibrating membrane having a vibrating electrode layer,
a plurality of through holes and the vibrating membrane adjacent to the through holes. And a
vibrating portion dividing member disposed between the electrode and the vibrating membrane
to divide the vibrating membrane into a plurality of vibrating portions, and in the plurality of
vibrating portions, the vibrating portion The electrode portion is located at a position facing the
central portion, and resonance is generated for the sound wave generated from the vibrating
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portion on the surface of the electrode opposite to the vibrating membrane side and passing
through the through hole of the electrode. It is characterized in that a resonance pipe member
having a plurality of through holes acting as a pipe is disposed. In the electrostatic transducer of
the present invention configured as described above, the vibrating membrane and the electrode
are disposed so as to sandwich the vibrating portion dividing member (for example, the epoxy
resin layer). Then, when the vibrating membrane is attracted to the electrode by electrostatic
force, there is an electrode portion that generates an electrostatic force with respect to the
central portion of the vibrating portion of the vibrating membrane. Further, on the side opposite
to the vibrating membrane side of the electrode, a resonance tube member having a through hole
acting as a resonance tube for the sound wave generated from the vibrating portion of the
vibrating membrane is disposed. As a result, an electrostatic force is generated at the central
portion of the vibrating portion in which the vibrating membrane vibrates, and a force for
efficiently vibrating the vibrating membrane can be applied. Moreover, the sound pressure of the
radiated sound wave can be increased by the resonance tube action. Therefore, it is possible to
realize an electrostatic transducer that can obtain high efficiency and high sound pressure.
[0016]
Further, in the electrostatic transducer according to the present invention, a DC bias power
supply is applied to the vibrating electrode layer, and a carrier wave of an ultrasonic frequency
band is modulated with a signal wave of an audible frequency band between the vibrating
electrode layer and the electrode portion. And the electrostatic transducer is an electrostatic
ultrasonic transducer that emits ultrasonic waves. In the electrostatic transducer of the present
invention configured as described above, the electrostatic transducer according to the present
invention is used as an electrostatic ultrasonic transducer, and a modulated wave in which a
carrier wave in the ultrasonic frequency band is modulated by a signal wave in the audio
frequency band Thus, in the electrostatic ultrasonic transducer, the vibrating membrane can be
efficiently vibrated, and the sound pressure of the radiated sound wave can be increased by the
resonance tube action.
[0017]
In the electrostatic transducer according to the present invention, an electrostatic force is
generated by a voltage applied between a vibrating membrane having a vibrating electrode layer,
a plurality of through holes and the vibrating membrane adjacent to the through holes. And a
vibrating portion dividing member disposed between the electrode and the vibrating membrane
to divide the vibrating membrane into a plurality of vibrating portions, and in the plurality of
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vibrating portions, the vibrating portion The electrode portion is located at a position facing the
central portion, and the through hole portion of the electrode is configured to act as a resonance
tube. In the electrostatic transducer of the present invention configured as described above, the
vibrating membrane and the electrode are disposed so as to sandwich the vibrating portion
dividing member (for example, the epoxy resin layer). Then, when the vibrating membrane is
attracted to the electrode by electrostatic force, there is an electrode portion that generates
electrostatic force with respect to the central portion of the vibrating portion of the vibrating
membrane. In addition, the through hole portion of the electrode acts as a resonance tube. As a
result, an electrostatic force is generated at the central portion of the vibrating portion in which
the vibrating membrane vibrates, and a force for efficiently vibrating the vibrating membrane can
be applied. Further, the sound pressure of the radiated sound wave can be increased by the
resonance tube action by the through hole of the electrode. Therefore, it is possible to realize an
electrostatic transducer that can obtain high efficiency and high sound pressure.
[0018]
Further, in the electrostatic transducer according to the present invention, a DC bias power
supply is applied to the vibrating electrode layer, and a carrier wave of an ultrasonic frequency
band is modulated with a signal wave of an audible frequency band between the vibrating
electrode layer and the electrode portion. And the electrostatic transducer is an electrostatic
ultrasonic transducer that emits ultrasonic waves. In the electrostatic transducer of the present
invention configured as described above, the electrostatic transducer according to the present
invention is used as an electrostatic ultrasonic transducer, and a modulated wave in which a
carrier wave in the ultrasonic frequency band is modulated by a signal wave in the audio
frequency band Thus, in the electrostatic ultrasonic transducer, the vibrating membrane can be
efficiently vibrated, and the sound pressure of the radiated sound wave can be increased by the
resonance tube action.
[0019]
In the electrostatic transducer according to the present invention, an electrostatic force is
generated by a voltage applied between a vibrating membrane having a vibrating electrode layer,
a plurality of through holes and the vibrating membrane adjacent to the through holes. And a
vibrating portion dividing member disposed between the electrode and the vibrating membrane
to divide the vibrating membrane into a plurality of vibrating portions, and in the plurality of
vibrating portions, the vibrating portion The electrode portion is located at a position opposite to
the central portion, and has a plurality of through holes on the surface of the vibrating film
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opposite to the electrode side to act as a resonance tube for sound waves generated from the
vibrating portion A first resonance pipe member is disposed, and further, as a resonance pipe for
a sound wave generated from the vibrating portion on the surface of the electrode opposite to
the vibrating membrane side and passing through the through hole of the electrode A plurality of
acting through holes Resonance tube member is arranged in that, characterized by. In the
electrostatic transducer of the present invention configured as described above, the vibrating
membrane and the electrode are disposed so as to sandwich the vibrating portion dividing
member (for example, the epoxy resin layer). Then, when the vibrating membrane is attracted to
the electrode by electrostatic force, there is an electrode portion that generates electrostatic
force with respect to the central portion of the vibrating portion of the vibrating membrane. In
addition, the first resonance tube member having a through hole that acts as a resonance tube
for the sound wave generated from the vibrating portion of the vibrating membrane is disposed
on the opposite surface side to the electrode side of the vibrating membrane. Furthermore, a
second resonance tube member having a through hole acting as a resonance tube for the sound
wave generated from the vibrating portion of the vibrating membrane is disposed on the side
opposite to the vibrating membrane side of the electrode. As a result, an electrostatic force is
generated at the central portion of the vibrating portion in which the vibrating membrane
vibrates, and a force for efficiently vibrating the vibrating membrane can be applied. Also, due to
the resonance tube action, the sound pressure of the sound waves output from both sides of the
electrostatic transducer is increased. Therefore, it is possible to realize an electrostatic transducer
that can obtain high efficiency and high sound pressure.
[0020]
Further, in the electrostatic transducer according to the present invention, a DC bias power
supply is applied to the vibrating electrode layer, and a carrier wave of an ultrasonic frequency
band is modulated with a signal wave of an audible frequency band between the vibrating
electrode layer and the electrode portion. And the electrostatic transducer is an electrostatic
ultrasonic transducer that emits ultrasonic waves. In the electrostatic transducer of the present
invention configured as described above, the electrostatic transducer according to the present
invention is used as an electrostatic ultrasonic transducer, and a modulated wave in which a
carrier wave in the ultrasonic frequency band is modulated by a signal wave in the audio
frequency band Thus, in the electrostatic ultrasonic transducer, the vibrating membrane can be
efficiently vibrated, and the sound pressure of the radiated sound wave can be increased by the
resonance tube action.
[0021]
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In the electrostatic transducer according to the present invention, an electrostatic force is
generated by a voltage applied between a vibrating membrane having a vibrating electrode layer,
a plurality of through holes and the vibrating membrane adjacent to the through holes. And a
vibrating portion dividing member disposed between the electrode and the vibrating membrane
to divide the vibrating membrane into a plurality of vibrating portions, and in the plurality of
vibrating portions, the vibrating portion The electrode portion is located at a position opposite to
the central portion, and has a plurality of through holes on the surface of the vibrating film
opposite to the electrode side to act as a resonance tube for sound waves generated from the
vibrating portion A resonance pipe member is disposed, and the through hole portion of the
electrode is configured to act as a resonance pipe. In the electrostatic transducer of the present
invention configured as described above, the vibrating membrane and the electrode are disposed
so as to sandwich the vibrating portion dividing member (for example, the epoxy resin layer).
Then, when the vibrating membrane is attracted to the electrode by electrostatic force, there is
an electrode portion that generates electrostatic force with respect to the central portion of the
vibrating portion of the vibrating membrane. Further, on the side opposite to the electrode side
of the vibrating membrane, a resonance tube member having a plurality of through holes acting
as a resonance tube for the sound wave generated from the vibrating portion of the vibrating
membrane is disposed. Furthermore, the through hole of the electrode acts as a resonance tube.
As a result, an electrostatic force is generated at the central portion of the vibrating portion in
which the vibrating membrane vibrates, and a force for efficiently vibrating the vibrating
membrane can be applied. Also, due to the resonance tube action, the sound pressure of the
sound waves output from both sides of the electrostatic transducer is increased. Therefore, it is
possible to realize an electrostatic transducer that can obtain high efficiency and high sound
pressure.
[0022]
Further, in the electrostatic transducer according to the present invention, a DC bias power
supply is applied to the vibrating electrode layer, and a carrier wave of an ultrasonic frequency
band is modulated with a signal wave of an audible frequency band between the vibrating
electrode layer and the electrode portion. And the electrostatic transducer is an electrostatic
ultrasonic transducer that emits ultrasonic waves. In the electrostatic transducer of the present
invention configured as described above, the electrostatic transducer according to the present
invention is used as an electrostatic ultrasonic transducer, and a modulated wave in which a
carrier wave in the ultrasonic frequency band is modulated by a signal wave in the audio
frequency band Thus, in the electrostatic ultrasonic transducer, the vibrating membrane can be
efficiently vibrated, and the sound pressure of the radiated sound wave can be increased by the
resonance tube action.
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[0023]
Further, in the ultrasonic speaker according to the present invention, a carrier wave of an
ultrasonic frequency band is modulated by a signal wave output from a signal source generating
an audio frequency band signal wave, and an electrostatic transducer is driven by the modulated
wave. An ultrasonic speaker that reproduces signal sound in an audible frequency band, wherein
the electrostatic transducer has a vibrating membrane having a vibrating electrode layer, a
plurality of through holes, and is applied between the vibrating membrane An electrode that
exerts an electrostatic attractive force on one surface side of the vibrating membrane by the
voltage applied, and a vibrating portion division which is disposed between the electrode and the
vibrating membrane and divides the vibrating membrane into a plurality of vibrating portions A
member, and the electrode is configured such that an electrostatic attraction force acts on a
central portion of a vibrating portion of the vibrating membrane, and a resonance tube for sound
waves generated from the vibrating membrane age Providing the resonance tube structure which
acts, characterized by. In the ultrasonic speaker according to the present invention having the
above configuration, the carrier wave (carrier wave) of the ultrasonic frequency band is
modulated by the signal wave of the audio frequency band, and the ultrasonic speaker drives the
electrostatic transducer by the modulated wave. While using a pull-type electrostatic transducer
that applies an electrostatic force from one surface side to the film, an electrode structure that
electrostatically attracts the central portion of the vibrating portion of the vibrating film, and a
sound wave generated from the vibrating film An electrostatic transducer is used which
comprises a resonant tube structure which acts as a resonant tube. Thereby, in the ultrasonic
speaker, high sound pressure can be obtained with high efficiency. Therefore, it is possible to
realize an ultrasonic speaker capable of generating an acoustic signal with a sound pressure level
high enough to obtain a parametric array effect.
[0024]
Hereinafter, embodiments of the present invention will be described with reference to the
attached drawings.
[0025]
[Explanation of Basic Concept of Electrostatic Transducer of the Present Invention] FIG. 1 is a
view for explaining the basic concept of the electrostatic transducer of the present invention.
[0026]
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FIG. 1A shows a state of application of electrostatic force to the vibrating film 31 in a
conventional pull-type electrostatic transducer.
As shown in FIG. 1A, in the conventional pull-type electrostatic transducer, the electrostatic force
f is applied only to the end of the vibrating membrane 31, and the vibrating membrane 31 is
vibrated with high efficiency. It was difficult.
[0027]
On the other hand, FIG. 1B shows a state of application of electrostatic force to the vibrating film
31 in the pull-type electrostatic transducer of the present invention.
As shown in FIG. 1B, in the electrostatic transducer according to the present invention, the
electrode portion 14 of the electrode 11 is disposed at the central portion of the diaphragm 31,
and the electrostatic force f is applied to the central portion of the diaphragm 31. Is configured
as. As a result, the electrostatic force is efficiently transmitted to the vibrating film 31, the
amplitude of the vibrating film 31 is increased, and the sound pressure is improved.
[0028]
Further, the through hole 22 of the resonance tube member 21 is disposed to the vibrating
membrane 31, and the through hole 22 acts as a resonance tube, and the sound pressure of the
sound wave (for example, ultrasonic wave) emitted from the vibrating membrane 31 It is
configured to be increased further.
[0029]
First Embodiment FIG. 2 is a view showing a configuration of an electrode of an electrostatic
transducer according to a first embodiment of the present invention.
In addition, FIG. 2 shows a part of electrode for description.
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[0030]
As shown in FIG. 2A, in the electrostatic transducer according to the present invention, a plurality
of through holes are provided in a conductive material of a thin plate metal (for example,
aluminum alloy, stainless steel, etc.) as the electrode 11. In the example shown in FIG. 2, four
through holes 12a, 12b, 12c and 12d are arranged on concentric circles R (circle R of center X
shown in FIG. 2C). In addition, when naming four through-holes 12a, 12b, 12c, 12d generically, it
calls "the through-hole part 12" (the same also in drawing).
[0031]
A plurality of through holes 12 are arranged on the electrode 11 (for example, arranged in a
honeycomb shape). Then, as shown in FIG. 2 (B), an epoxy insulating layer is applied on one
surface side of the electrode 11 (the side facing the vibrating film 31). In this case, the epoxy
insulating layer is applied so as to provide a circular electrode portion (exposed surface not
covered with the epoxy insulating layer) 14 including the four through holes 12a, 12b, 12c and
12d. For example, an epoxy insulating layer is pattern-printed on the surface of the electrode 11
(the side facing the vibrating film 31) in the same manner as resist printing on a printed circuit
board. This becomes the vibrating portion dividing member 13, which is disposed between the
electrode 11 and the vibrating membrane 31 and serves to divide the vibrating membrane 31
into a plurality of vibrating portions (vibrating portions).
[0032]
Therefore, as shown in FIG. 2C, on one surface of the electrode 11, four through holes 12a, 12b,
12c, 12d, an electrode portion 14 including these through holes, and a vibrating portion division,
A member 13 (epoxy insulating layer) 13 is formed. As described above, in the electrode 11, the
electrode surface (electrostatic force generating surface) for generating electrostatic force is
located at the central portion of the electrode portion 14, and the through hole 12 is provided in
the periphery thereof.
[0033]
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FIG. 3 is a view showing the configuration of a resonance tube 21 of the electrostatic transducer
according to the first embodiment of the present invention. In addition, FIG. 2 shows a part of
resonance pipe member 21 for description.
[0034]
As shown in FIG. 3, the through holes 22 a, 22 b, and 22 c are formed as a resonance pipe in a
resin (for example, acrylic, super engineering plastic, etc.) as the resonance pipe member 21. For
example, it can be produced by drilling or injection molding of a resin. The diameter of each
through hole to be the resonance tube is sized to include the four through holes 12 on the
electrode portion 14 shown in FIG.
[0035]
FIG. 3B is a view showing the configuration of the vibrating film 31. As shown in FIG. The
vibrating film 31 is formed by sandwiching the vibrating electrode layer 31A, which is a
conductive layer, with the dielectric film (insulating layer) 31B. The vibrating electrode layer 31A
is formed of, for example, an aluminum thin film by sputter deposition.
[0036]
FIG. 4 is a view for explaining the configuration of the electrostatic transducer according to the
first embodiment of the present invention.
[0037]
As shown in FIG. 4, in the electrostatic transducer according to the present invention, the
resonance tube 21 is moved in the direction of arrow A, the electrode 11 is moved in the
direction of arrow B, and the electrode 11 and the resonance tube 21 sandwich the diaphragm
31. In the same way.
In this case, the vibrating membrane 31 is held so that the position of the circular electrode
portion 14 including the through hole 12 of the electrode 11 and the position of the through
hole 22 of the resonance pipe member 21 coincide with each other. Therefore, the centers of the
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four through holes of the electrode 11 (see the center X of FIG. 2C) and the center of the through
hole 22 of the resonance pipe member 21 coincide or substantially coincide with each other with
the diaphragm 31 interposed therebetween. It will be.
[0038]
FIG. 5 is a view showing the cross-sectional shape of the electrostatic transducer according to the
first embodiment of the present invention, and is a cross-sectional view passing through the
center of the circular portion of the epoxy insulating layer (in FIG. 2 (B) Sectional view in the XX
′ direction).
[0039]
As shown in FIG. 5A, in the electrostatic transducer 1, the vibrating film 31 and the electrode 11
are disposed so as to sandwich the vibrating portion dividing member 13 (epoxy resin layer) 13.
At this time, the circular portion (refer to FIG. 2B) of the vibration portion dividing member 13
and the through hole (resonance pipe) 22 of the resonance pipe member 21 are disposed to face
each other. Thus, a cavity a is provided between the electrode 11 and the vibrating membrane
31. The portion of the vibrating film 31 facing the hollow portion a (the portion not pressed by
the vibrating portion dividing member 13) is the vibrating portion of the vibrating film 31.
[0040]
The vibrating film 31 is formed by sandwiching the vibrating electrode layer 31A, which is a
conductive layer, with the insulating dielectric film 31B. With such a configuration, the vibrating
membrane 31 and the electrode portion 14 of the electrode 11 face each other via the hollow
portion a, and between the vibrating electrode layer 31A of the vibrating membrane 31 and the
electrode portion 14 of the electrode 11 Electrostatic force acts.
[0041]
FIG. 5 (B) is a figure for demonstrating the application method of the voltage in the electrostatic
transducer of this invention. As shown in FIG. 5B, a DC bias voltage is applied to the vibrating
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electrode layer 31A of the vibrating film 31 by the DC bias power supply 32. An AC signal (AC
drive voltage) from an AC signal source 33 is applied between the vibrating electrode layer 31A
of the diaphragm 31 and the electrode 11 in a superimposed manner on the DC bias voltage.
However, the method of applying the voltage is not limited to this, and an alternation can be
made, such as applying an alternating current signal (AC drive voltage) to the vibrating film 31
and applying a direct current bias voltage to the electrode 11.
[0042]
The alternating current signal output from the alternating current signal source 33 may be a
signal in the audible frequency band, and is a signal of a modulated wave obtained by modulating
the carrier wave in the ultrasonic frequency band with a signal wave in the audible frequency
band It is also good. When the signal applied to the electrostatic transducer 1 is a signal in the
ultrasonic frequency band, the electrostatic transducer 1 emits an acoustic wave in the ultrasonic
frequency band, and is also called an electrostatic ultrasonic transducer.
[0043]
FIG. 6 is a diagram for explaining the vibration state of the vibrating membrane 31 of the
electrostatic transducer. By the voltage application method shown in FIG. 5B, as shown in FIG.
6A, the vibrating film 31 is attracted toward the electrode 11 by electrostatic force. Then, the
electrostatic force changes (strong or weak) due to the change of the voltage of the AC signal,
and the vibrating membrane 31 vibrates due to the balance between the elastic restoring force of
the vibrating membrane 31 and the electrostatic force.
[0044]
At this time, since the vibrating film 31 is attracted to the electrode 11 side, the vibrating film 31
sticks to the vibrating portion dividing member 13. Therefore, since the vibrating membrane 31
hardly vibrates in this portion, the vibrating membrane 31 is divided into a plurality of vibrating
portions (vibrating portions). Specifically, the vibrating portion (vibrating portion) of the
vibrating film 31 has the same shape as the circular portion (see FIG. 2B) of the vibrating portion
dividing member (epoxy insulating layer) 13. Therefore, the electrode portion 14 is positioned at
a position facing the central portion of the vibrating portion (vibration portion). Therefore, it is
possible to apply a force for vibrating the vibrating membrane 31 more efficiently than exerting
04-05-2019
16
an electrostatic force at the end of the vibrating section as in the conventional pull-type
electrostatic transducer. Therefore, the amplitude also increases, and the sound pressure can be
increased.
[0045]
Further, sound waves generated by the vibration of the vibrating film 31 pass through the
through holes 22 of the resonance tube member 21. At this time, the through hole 22 acts as a
resonance tube. That is, when it is desired to generate an acoustic wave mainly at 50 kHz
(ultrasonic wave), the wavelength of the sound is determined as the velocity of the sound about
340 m / sec. Therefore, for example, when the thickness of the resonance tube member 21, that
is, the length of the through hole 22 is about 1/4 (about 1.5 mm) of the wavelength, the through
hole 22 acts as a resonance tube, and the sound pressure is reduced. Increase. The length of the
through hole is not limited to about 1⁄4 of the wavelength, and when the wavelength length is λ
as the resonance condition, (on / 4) · n, where n is a positive odd number It is also good.
Also, the reason for setting the wavelength to be about 1/4 is because the length is slightly
changed from 1⁄4 of the wavelength due to the open end correction of the resonance tube. In
addition, the conditions of resonance are disclosed by Unexamined-Japanese-Patent No. 200768148 grade ¦ etc.,.
[0046]
In addition to forming the electrode portion 14, the through hole 12 of the electrode 11 has an
effect of reducing the air resistance of the vibrating film 31 when air is released from the
through hole 12.
[0047]
According to the above configuration, as shown in FIG. 6B, the sound wave emitted from the
vibrating membrane 31 passes through the through hole (resonance tube) 22 and is emitted to
the front surface of the electrostatic transducer.
[0048]
As described above, in the configuration of the electrostatic transducer according to the present
invention, when the vibrating membrane 31 is attracted to the electrode 11, there is an electrode
portion that generates an electrostatic force corresponding to the central portion of the vibrating
04-05-2019
17
portion of the vibrating membrane 31.
For this reason, a force can be applied to the vibrating membrane 31 to vibrate efficiently as
compared with the conventional configuration.
Further, by forming the resonance pipe by the through hole 22 of the resonance pipe member
21, the sound pressure can be further increased. Therefore, the electrostatic force can be
efficiently transmitted to the vibrating film 31 to increase the amplitude of the vibrating film 31,
and an electrostatic transducer with high efficiency and high sound pressure output can be
realized.
[0049]
Second Embodiment In the first embodiment, an example of the electrostatic transducer
constituted by sandwiching the vibrating film 31 between the resonance tube member 21 and
the electrode 11 has been described. In the second embodiment, an example in which the
resonance pipe member 21 is disposed on the side of the electrode 11 will be described.
[0050]
FIG. 7 is a view showing the configuration of the electrostatic transducer according to the second
embodiment of the present invention, and is a cross-sectional view passing through the center of
the circular portion of the epoxy insulating layer (X in FIG. 2 (B) Cross section in the -X
'direction).
The electrode 11 is the same as that shown in FIG. 2, and the resonance pipe member 21 is the
same as that shown in FIG. 3, and the description thereof will be omitted.
[0051]
In the electrostatic transducer 1A shown in FIG. 7, the vibrating membrane 31 and the electrode
11 are disposed so as to sandwich the vibrating portion dividing member (epoxy resin layer) 13
therebetween.
[0052]
04-05-2019
18
Then, the resonance pipe member 21 is disposed on the surface of the electrode 11 opposite to
the vibrating membrane 31 side.
At this time, the circular part (circular part where the epoxy insulating layer is not applied) of the
vibration part dividing member 13 and the through hole (resonance pipe) 22 of the resonance
pipe member 21 correspond to each other with the electrode 11 interposed therebetween.
Placed in position.
[0053]
FIG. 7B is a view showing a method of applying a voltage to the electrostatic transducer
according to the second embodiment of the present invention. As shown in FIG. 7B, a DC bias
voltage is applied to the vibrating film 31 by the DC bias power supply 32, and an AC signal (AC
drive voltage) is applied to the electrode 11 by the AC signal source 33. However, the method of
applying the voltage is not limited to this, and an alternation can be made, such as applying an
alternating current signal (AC drive voltage) to the vibrating film 31 and applying a direct current
bias to the electrode 11.
[0054]
The alternating current signal output from the alternating current signal source 33 may be a
signal in the audible frequency band, and is a signal of a modulated wave obtained by modulating
the carrier wave in the ultrasonic frequency band with a signal wave in the audible frequency
band It is also good. When the signal applied to the electrostatic transducer 1A is a signal in the
ultrasonic frequency band, the electrostatic transducer 1A is also referred to as an electrostatic
ultrasonic transducer because it emits sound waves in the ultrasonic frequency band.
[0055]
FIG. 8 is a view for explaining the vibration state of the vibrating membrane 31 of the
electrostatic transducer shown in FIG. By the voltage application method shown in FIG. 7B, as
shown in FIG. 8A, the vibrating film 31 is attracted toward the electrode 11 by electrostatic force.
04-05-2019
19
Then, the electrostatic force changes (strong or weak) due to the change of the voltage of the AC
signal, and the vibrating membrane 31 vibrates due to the balance between the elastic restoring
force of the vibrating membrane 31 and the electrostatic force.
[0056]
At this time, since the vibrating film 31 is attracted to the electrode 11 side, the vibrating film 31
is stuck to the vibrating portion dividing member (epoxy insulating layer) 13. Therefore, since
the vibrating membrane 31 hardly vibrates in this portion, the vibrating membrane 31 is divided
into a plurality of vibrating portions (vibrating portions). Specifically, the vibrating portion
(vibration portion) has the same shape as the circular portion of the vibrating portion division
member 13. Therefore, the electrode portion 14 is positioned at a position facing the central
portion of the vibrating portion (vibration portion). Therefore, a force can be applied to the
vibrating membrane more efficiently than by applying an electrostatic force at the end of the
vibrating portion (vibrating portion) as in the conventional pull-type electrostatic transducer.
Therefore, the amplitude also increases, and the sound pressure can be increased.
[0057]
Further, sound waves generated by the vibration of the vibrating membrane 31 pass through the
portion of the through hole 12 of the electrode 11 and pass through the through hole 22 of the
resonance pipe member 21. At this time, the through hole 22 acts as a resonance tube. That is,
when it is desired to generate an acoustic wave mainly at 50 kHz (ultrasound), the wavelength of
the sound is determined as the velocity of the sound about 340 m / sec. Therefore, for example,
when the thickness of the resonance tube member 21, that is, the length of the through hole 22
is about 1/4 (about 1.5 mm) of the wavelength, the through hole 22 acts as a resonance tube,
and the sound pressure is reduced. Increase. The length of the through hole 22 is not limited to
about 1⁄4 of the wavelength, and (in / 4) · n, where n is a positive odd number assuming that
the wavelength is a resonance condition. It is also good. The reason for setting the wavelength to
be about 1⁄4 is that the correction of the open end of the resonance tube causes the length to
slightly change more than 1⁄4 of the wavelength and the resonance frequency to change by the
thickness of the electrode. This results in an electrostatic transducer with high efficiency and
high sound pressure output. In addition, the conditions of resonance are disclosed by
Unexamined-Japanese-Patent No. 2007-68148 etc. FIG.
[0058]
04-05-2019
20
In addition to forming the electrode portion 14, the through hole 12 of the electrode 11 has an
effect of reducing the air resistance of the vibrating film 31 when air is released from the
through hole 12.
[0059]
Thus, in the configuration of the electrostatic transducer shown in FIG. 7, when the vibrating
membrane 31 is attracted to the electrode 11, there is an electrode portion that generates an
electrostatic force corresponding to the central portion of the vibrating portion of the vibrating
membrane 31. Therefore, a force can be applied to the vibrating membrane 31 to vibrate
efficiently as compared with the conventional configuration.
Further, by forming the resonance pipe by the through hole 22 of the resonance pipe member
21, the sound pressure can be further increased. Therefore, the electrostatic force can be
efficiently transmitted to the vibrating film 31 to increase the amplitude of the vibrating film 31,
and an electrostatic transducer with high efficiency and high sound pressure output can be
realized.
[0060]
Third Embodiment In the first and second embodiments, the example in which the resonance
tube is formed by the through hole 22 of the resonance tube member 21 has been described. Can
be formed. In the third embodiment of the present invention, an example in which a resonance
tube is formed in an electrode will be described.
[0061]
FIG. 9 is a view showing a configuration of an electrode 11A in an electrostatic transducer
according to a third embodiment of the present invention. FIG. 9 shows a part of the electrode for
the purpose of explanation.
[0062]
04-05-2019
21
As shown in FIG. 9, as the electrode 11A, a through hole 12A is formed in a conductive material
of metal (for example, aluminum alloy, stainless steel, etc.). As a method of forming the through
holes 12A, there is a method of laminating or drilling metal edged thin plates. The electrode 11A
shown in FIG. 9 is characterized in that the thickness t is larger than that of the electrode 11
shown in FIG. 2 (the thickness is required to form a resonance tube).
[0063]
Then, an epoxy insulating layer (for example, a resist film) is applied on the electrode 11A so as
to include four holes (12Aa, 12Ab, 12Ac, 12Ad). This is the vibrating portion dividing member
13A, which is disposed between the electrode 11A and the vibrating film 31 and serves to divide
the vibrating film 31 into a plurality of vibrating portions (vibrating portions). The vibrating
membrane 31 has the same configuration as the vibrating membrane used in the first
embodiment and the second embodiment (see FIG. 3B).
[0064]
FIG. 10 is a view showing the configuration of the electrostatic transducer according to the third
embodiment of the present invention, and is a cross-sectional view passing through the center of
the circular portion of the vibrating portion division member 13A. As shown in FIG. 10, in the
electrostatic transducer 1B, the vibrating membrane 31 and the electrode 11A are disposed so as
to sandwich the vibrating section dividing member 13A.
[0065]
FIG. 10B is a diagram showing a method of applying a voltage to the electrostatic transducer
according to the third embodiment of the present invention. As shown in FIG. 10 (B). A DC bias
voltage is applied to the vibrating film 31 by the DC bias power supply 32, and an AC signal (AC
drive voltage) is applied to the electrode 11A by the AC signal source 33. However, the method
of applying the voltage is not limited to this, and a change such as applying an AC signal (AC
drive voltage) to the vibrating film 31 and applying a DC bias voltage to the electrode 11A is
possible.
04-05-2019
22
[0066]
The alternating current signal output from the alternating current signal source 33 may be a
signal in the audible frequency band, and is a signal of a modulated wave obtained by modulating
the carrier wave in the ultrasonic frequency band with a signal wave in the audible frequency
band It is also good. When the signal applied to the electrostatic transducer 1 is a signal in the
ultrasonic frequency band, the electrostatic transducer 1 emits an acoustic wave in the ultrasonic
frequency band, and is also called an electrostatic ultrasonic transducer.
[0067]
FIG. 11 is a diagram for explaining the vibration state of the vibrating membrane 31 of the
electrostatic transducer shown in FIG. By the voltage application method shown in FIG. 10B, as
shown in FIG. 11, the vibrating film 31 is attracted toward the electrode 11A by electrostatic
force. Then, the electrostatic force changes (strong or weak) due to the change in voltage of the
AC signal (AC drive voltage), and the diaphragm 31 vibrates due to the balance between the
elastic restoring force of the diaphragm 31 and the electrostatic force.
[0068]
At this time, since the vibrating film 31 is attracted to the electrode 11A side, the vibrating film
31 sticks to the vibrating portion dividing member 13A. Therefore, since the vibrating membrane
31 hardly vibrates in this portion, the vibrating membrane 31 is divided into a plurality of
vibrating portions (vibrating portions). Specifically, the vibrating portion (vibrating portion) has
the same shape as the circular portion of the vibrating portion dividing member (epoxy
insulating layer) 13A. Therefore, the electrode portion 14A is located at a position facing the
central portion of the vibrating portion (vibration portion). For this reason, it is possible to apply
a force to the vibrating membrane to vibrate efficiently, rather than exerting an electrostatic
force at the end of the vibrating portion (vibrating portion). Therefore, the amplitude also
increases, and the sound pressure can be increased.
[0069]
Further, sound waves generated by the vibration of the vibrating membrane 31 pass through the
04-05-2019
23
through hole 12A of the electrode 11A. At this time, the portion of the through hole 12A acts as
a resonance pipe. That is, when it is desired to generate a sound wave mainly at 50 kHz
(ultrasonic wave), the sound wavelength is determined as the sound velocity of about 340 m /
sec, so for example, the thickness of the resonance tube member 21, that is When the
wavelength is about 1⁄4 (about 1.5 mm), the through hole 12A acts as a resonance tube to
increase the sound pressure. Incidentally, the length of the through hole 12A is not limited to
about 1/4 of the wavelength, and when the wavelength length is λ as the resonance condition,
(in / 4) · n, where n is a positive odd number It is good also as ". Also, the reason for setting the
wavelength to be about 1/4 is because the length is slightly changed from 1⁄4 of the wavelength
due to the open end correction of the resonance tube. This results in an electrostatic transducer
with high efficiency and high sound quality. In addition, the conditions of resonance are disclosed
by Unexamined-Japanese-Patent No. 2007-68148 etc. FIG.
[0070]
In addition, as a structure of an electrode, it can change into the structure shown to the electrode
11B shown in FIG. In the electrostatic transducer 1C shown in FIG. 12, the electrode 11B is made
of a resin (for example, acrylic, super engineering plastic, etc.) 23. Then, the through holes 25 are
formed in the resin 23 by drilling or injection molding of the resin, and the conductive paste 24
is applied to the surface of the resin 23. Thereby, the weight of the electrostatic transducer can
be reduced.
[0071]
Fourth Embodiment FIG. 13 is a diagram showing a configuration of an electrostatic transducer
according to a fourth embodiment of the present invention. The electrostatic transducer 1D
shown in FIG. 13 is an example in which the resonance pipe member 21 is disposed on both
surfaces of the vibrating membrane 31 and the electrode 11. Thereby, the sound pressure can be
increased for the sound waves generated from both sides of the vibrating film 31 and can be
used.
[0072]
Fifth Embodiment FIG. 14 is a diagram showing a configuration of an electrostatic transducer
according to a fifth embodiment of the present invention. The electrostatic transducer 1E shown
04-05-2019
24
in FIG. 14 is an example in which the resonance tube member 21 is disposed on the surface side
of the vibrating membrane 31 in the electrostatic transducer 1B of the third embodiment shown
in FIG. Thereby, the sound pressure can be increased for the sound waves generated from both
sides of the vibrating film 31 and can be used.
[0073]
Sixth Embodiment From the above-described first embodiment, the shapes of the electrodes and
the through holes in the fifth embodiment are not limited to the shapes shown in FIGS. 2 and 9.
For example, the shape shown in FIG. 15 (A) or FIG. 15 (B) may be used.
[0074]
The electrode 11C shown in FIG. 15A is obtained by increasing the number of through holes 12C
in the electrode portion 14C.
The electrode 11D shown in FIG. 15B is provided with a through hole 12D so that the electrode
portion 14D has a cross shape.
[0075]
Seventh Embodiment Next, an electrostatic transducer provided with an acoustic reflector
according to a seventh embodiment of the present invention will be described. FIG. 16 is a view
showing the configuration of an electrostatic transducer provided with an acoustic reflection
plate.
[0076]
The configuration of the electrostatic transducer having the acoustic reflector shown in FIG. 16 is
the same as that of the electrostatic transducer according to the first embodiment except that the
acoustic reflectors 51 and 52 are provided on the back of the electrostatic transducer. It is
identical to the configuration of 1 (see FIG. 5). In FIG. 16, only a part of the electrostatic
transducer 1 is shown because of easy viewing of the drawing.
04-05-2019
25
[0077]
The electrostatic transducer provided with the acoustic reflectors 51 and 52 exerts a remarkable
effect particularly when driven by a modulation signal obtained by modulating a carrier wave in
the ultrasonic frequency band with a signal in the audio frequency band. is there. Therefore, in
the following description, the electrostatic transducer 1 is described as being used as an
electrostatic ultrasonic transducer.
[0078]
In FIG. 16, the acoustic reflectors 51 and 52 are configured so that the ultrasonic waves emitted
from the through holes 12 of the electrodes 11 of the electrostatic transducer 1 are all emitted to
the front of the electrostatic transducer in the same length path. Is located in
[0079]
That is, one end of the acoustic reflection plate is located at the center position M of the back
surface of the electrostatic transducer, and the acoustic reflector is disposed at an angle of 45 °
to both sides of the back surface of the electrostatic transducer with respect to the center
position M At an angle perpendicular to the ends of the pair of first reflecting plates 51, 51 of a
length corresponding to the ends X1, X2 of the electrostatic transducer and the pair of first
reflecting plates 51, 51 A pair of second reflecting plates 52, 52 are respectively connected in
the outward direction of the first reflecting plate and have a length equal to the length of the first
reflecting plate.
[0080]
In the above configuration, the first reflecting plates 51, 51 are disposed at an angle of 45 °
with respect to both sides of the center position M of the back surface of the electrostatic
transducer, to the point where the end thereof coincides with the end of the electrostatic
transducer The length of the
The ultrasonic waves emitted from the back of the electrostatic transducer by the first reflecting
plate 51 are horizontally reflected.
04-05-2019
26
[0081]
Next, by connecting the second reflectors 52, 52 connected at an angle perpendicular to the first
reflectors 51, 51 to the outside of the first reflectors 51, 51, the ultrasonic waves are
electrostatically Emitted to the front of the mold transducer.
It is necessary that the second reflector length be equal to the first reflector length. The
important thing here is that the ultrasonic waves emitted from the back of the electrostatic
transducer all have the same length of path. The fact that the path lengths are the same means
that the phases of the ultrasonic waves emitted from the back are all in phase.
[0082]
Also, as shown in FIG. 16, the acoustic wave can be geometrically handled because the emitted
acoustic wave is an ultrasonic wave and has extremely strong directivity. Another point that
needs to be mentioned is the time difference between the ultrasound emitted from the front of
the electrostatic transducer and the ultrasound reflected from the back and emitted to the front.
[0083]
Assuming that the transducer is circular and the radius is r, the ultrasonic waves emitted from a
point separated from the center position M of the transducer by a distance from the center
position M to the transducer front face are approximately 2r, ie, equal to the diameter of the
transducer . Of course, the distance a must satisfy the following equation. ０≦ａ≦ｒ …… （１）
[0084]
Now, assuming that the diameter of the transducer is about 10 cm and the speed of sound is 340
m / sec, the time difference between the ultrasonic wave emitted from the front and the
ultrasonic wave emitted from the back to reach the front is about 0.29 msec. There is no problem
because it is a time difference that human beings can not perceive. That is, ultrasonic waves
emitted from the front and back of the transducer can be used effectively.
04-05-2019
27
[0085]
Eighth Embodiment Next, an ultrasonic speaker according to an eighth embodiment of the
present invention will be described. FIG. 17 is a view showing the configuration of an ultrasonic
speaker using the electrostatic transducer of the present invention.
[0086]
The ultrasonic speaker according to the present embodiment is the above-described electrostatic
transducer (the electrostatic transducer according to the first to seventh embodiments) of the
present invention, which generates a sound wave in an ultrasonic frequency band. Used as an
electrostatic ultrasonic transducer.
[0087]
Since this electrostatic ultrasonic transducer has an electrode portion for generating an
electrostatic force corresponding to the central portion of the vibrating portion of the vibrating
membrane 31, the force is more efficiently vibrated in the vibrating membrane 31 compared to
the conventional configuration. Can be added.
Further, by forming the resonance pipe by the through hole 22 of the resonance pipe member
21, the sound pressure can be further increased.
[0088]
In FIG. 17, the ultrasonic speaker includes an audio frequency wave oscillation source 61 that
generates a signal wave in the audio wave frequency band, and a carrier wave oscillation source
62 that generates and outputs a carrier wave (carrier wave) in the ultrasonic frequency band. A
modulator 63, a power amplifier 64, and an electrostatic ultrasonic transducer 65 are included.
The modulator 63 modulates the carrier wave output from the carrier wave oscillation source 62
with the signal wave in the audio wave frequency band output from the audio frequency wave
oscillation source 61, and the electrostatic ultrasonic transducer via the power amplifier 64.
Supply to 65.
04-05-2019
28
[0089]
In the above configuration, the carrier wave in the ultrasonic frequency band output from the
carrier wave oscillation source 62 is modulated by the modulator 63 by the signal wave output
from the audio frequency wave oscillation source 61, and the modulation signal amplified by the
power amplifier 64 The electrostatic ultrasonic transducer 65 is driven. As a result, the
modulated signal is converted to a sound wave of finite amplitude level by the electrostatic
ultrasonic transducer 65, and this sound wave is emitted into the medium (in air) and the original
audio frequency band by the nonlinear effect of the medium (air). Signal sound is selfreproduced.
[0090]
That is, since the sound wave is a compression wave propagating through the air as a medium, in
the process of propagation of the modulated ultrasonic waves, the dense part and the sparse part
of the air appear prominently. As the speed of sound is slowed, the modulation wave itself is
distorted, so that the waveform is separated into the carrier wave (ultrasonic frequency band),
and the signal wave (sound signal) in the audible wave frequency band is reproduced.
[0091]
Ultrasonic waves are highly attenuated in the air and decay in proportion to the square of their
frequency.
Therefore, when the carrier frequency (ultrasound) is low, it is possible to provide an ultrasonic
speaker having a low attenuation and having a beam shape that allows sound to reach far.
Conversely, if the carrier frequency is high, the attenuation is severe, so that the parametric array
effect does not occur sufficiently, and it is possible to provide an ultrasonic speaker in which the
sound spreads. These are very effective functions because the same ultrasonic speaker can be
used according to the application.
[0092]
04-05-2019
29
In addition, dogs that often live with humans as pets can listen to sounds up to 40 kHz and cats
up to 100 kHz, so if you use a carrier frequency higher than that, there is no effect on pets. It
also has an advantage. In any case, being available at various frequencies brings many benefits.
[0093]
As described above, in the ultrasonic speaker according to the present invention, the electrostatic
transducer according to the present invention is used, and electrostatic force can be efficiently
transmitted to the vibrating membrane to increase the amplitude of the vibrating membrane.
Further, since the output sound pressure can be further increased by the resonance pipe, the
sound signal can be reproduced with a sufficient sound pressure level and a wide band
characteristic. In particular, in an ultrasonic speaker, an acoustic signal can be reproduced so as
to be emitted from a virtual sound source formed in the vicinity of a sound wave reflection
surface such as a screen with a sufficient sound pressure level and a wide band characteristic.
Therefore, control of the reproduction range can be easily performed.
[0094]
As described above, in the electrostatic transducer according to the present invention, the
electrode portion is positioned at a position opposed to the central portion of the vibrating
portion (vibration portion). Therefore, an electrostatic force is generated at the central portion of
the vibrating portion where the vibrating membrane vibrates. For this reason, compared with the
structure which an electrostatic force produces only at the edge part of the vibration part which
a diaphragm vibrates when the same electrostatic force arises, the force for vibrating a
diaphragm efficiently can be applied. Further, according to the configuration of the present
invention, the through hole or the through hole portion acting as a resonance pipe is provided.
Thus, the resonance tube action can increase the sound pressure of the radiated sound wave.
Therefore, according to the present invention, a configuration that generates both of the effects
described above can be realized, so that an electrostatic transducer that can obtain high
efficiency and high sound pressure, an ultrasonic speaker including the same, and the like can be
realized.
[0095]
The electrostatic transducer according to the present invention can be used not only for
ultrasonic speakers but also for sensors such as distance sensors.
04-05-2019
30
[0096]
Although the embodiments of the present invention have been described above, the electrostatic
transducer and the ultrasonic speaker according to the present invention are not limited to the
above illustrated examples, and various modifications may be made within the scope of the
present invention. Of course, changes can be made.
[0097]
Explanatory drawing of the basic concept of the electrostatic transducer of this invention.
BRIEF DESCRIPTION OF THE DRAWINGS The block diagram of the electrode of the electrostatic
transducer which concerns on 1st Embodiment.
The block diagram of the resonance tube member of an electrostatic transducer. Explanatory
drawing of a structure of the electrostatic transducer concerning 1st Embodiment. FIG. 1 is a
cross-sectional view of an electrostatic transducer according to a first embodiment. Explanatory
drawing of the vibration state of the vibrating film of the electrostatic transducer shown in FIG.
The block diagram of the electrostatic transducer which concerns on 2nd Embodiment.
Explanatory drawing of the vibration state of the vibrating film of the electrostatic transducer
shown in FIG. The block diagram of the electrode of the electrostatic transducer which concerns
on 3rd Embodiment. The block diagram of the electrostatic transducer which concerns on 3rd
Embodiment. FIG. 11 is an explanatory view of a vibration state of a vibrating membrane of the
electrostatic transducer shown in FIG. 10. The figure which shows the other structure of the
electrode of an electrostatic type transducer. The block diagram of the electrostatic transducer
concerning 4th Embodiment. The block diagram of the electrostatic transducer concerning 5th
Embodiment. The figure which shows the example of the other shape of an electrode part and a
through-hole part. The figure which shows the structure of an electrostatic transducer provided
with an acoustic reflection board. The figure which shows the structure of the ultrasonic speaker
of this invention. The figure which shows the structural example of the conventional pull type
electrostatic ultrasonic transducer. Explanatory drawing of the problem of the conventional pull
type electrostatic ultrasonic transducer. FIG. 8 is a view showing another configuration example
of a conventional pull-type electrostatic ultrasonic transducer.
Explanation of sign
04-05-2019
31
[0098]
1, 1A, 1B, 1C, 1D, 1E: electrostatic transducers, 11, 11A, 11B, 11C, 11D, electrodes 12, 12, 12A,
12C, 12D, through holes 13, 13A ... Vibrating part dividing member, 14, 14A, 14C, 14D ...
Electrode part, 21 ... Resonance tube member, 22 ... Through hole, 23 ... Resin, 24 ... Conductive
paste, 25 · · · Through hole, 31 · · · vibrating film, 31 A · · · vibrating electrode layer, 31 B · · ·
dielectric film, 32 · · · DC bias power supply, 33 · · · · · · 51, 52 · · · · · · Acoustic reflection plate, 61
··· Audio frequency wave oscillation source, 62 · · · Carrier wave oscillation source, 63 · · · · · · · · · · ·
· · · · · · · · · · · · · · Power amplifier, 65 · · · electrostatic ultrasonic transducer
04-05-2019
32

JP2007274363

JP2006262092

JP2001054189

JP2003189390

JP2008227832

JP2004140629

JP2009038637

JP2001245385

Document 754123

JP2000295687