JP2011205298

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DESCRIPTION JP2011205298
PROBLEM TO BE SOLVED: To provide an electro-acoustic transducer capable of eliminating a
diaphragm by electro-acoustic conversion using high frequency discharge, which is easy to
manufacture and easily prevents spark discharge and dissipates heat. To obtain an
electroacoustic transducer capable of producing the SOLUTION: A discharge portion is formed by
a needle electrode 5 and a horn 6 surrounding the periphery thereof, and a high frequency
oscillation circuit including a discharge portion and generating a high frequency discharge,
according to a sound wave introduced to the discharge portion An electro-acoustic transducer
that converts into voice by taking out a modulated voice signal or performing discharge
according to a high frequency signal modulated by the voice signal in a discharge unit. The horn
6 is in the shape of a funnel having a wide-mouthed portion and a narrow-mouthed cylindrical
portion 62. The cylindrical portion 62 surrounds the tip outer periphery of the needle-like
electrode 5 at a predetermined distance, A ceramic coating layer 9 is provided on the inner
peripheral surface of the surface 62. [Selected figure] Figure 1
Electro-acoustic transducer and method of manufacturing the same
[0001]
The present invention is an electroacoustic transducer capable of eliminating a diaphragm by
electroacoustic conversion utilizing high frequency discharge, which is easy to manufacture and
easily prevents spark discharge and dissipates heat. And a method of manufacturing the same.
[0002]
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A diaphragm is used in general electroacoustic transducers such as microphones and speakers.
In the case of a microphone, the vibration of a diaphragm that receives and vibrates a sound
wave is captured as an electromagnetic change, a change in electrostatic capacitance, or an
optical change, and converted into an electrical signal. In the case of a speaker, generally, an
audio signal is electromagnetically converted to be converted into vibration of a diaphragm, and
output as a sound wave. The diaphragms in these electroacoustic transducers are used to convert
between air vibration and electrical signals. In other words, three systems of acoustic systemmechanical vibration system-electric circuit system are connected by one diaphragm. As
described above, since the conventional general electroacoustic transducer, particularly the
microphone and the speaker, have the diaphragm in any system, there is a limit of frequency
response due to the presence of the diaphragm. Therefore, even if the mass of the diaphragm is
reduced to the limit, the inertia force is exerted because the mass is present, and the sound
collection limit exists at the frequency.
[0003]
As an example of an electroacoustic transducer without a diaphragm, Patent Document 1
describes a method of detecting particle velocity using a discharge and performing
electroacoustic conversion. The invention described in Patent Document 1 comprises a needlelike discharge electrode and a counter electrode surrounding the discharge electrode with a gap,
the counter electrode being spherical and made of a conductive material perforated so as to
transmit sound waves. The discharge electrode extends toward the inside of the spherical counter
electrode and reaches near the center of the sphere. A high frequency voltage signal is applied to
the discharge electrode from a high frequency voltage generation circuit modulated by a low
frequency signal to be converted into sound waves, and corona discharge corresponding to the
high frequency voltage signal is performed between the discharge electrode and the counter
electrode. As a result, the low frequency signal, that is, the sound wave is emitted.
[0004]
Further, FIG. 2 shows an example of a discharge type speaker using discharge instead of a
diaphragm, which is known from Non-Patent Document 1, as another example of the
electroacoustic transducer having no diaphragm. The discharge type speaker shown in FIG. 2
mainly includes a base 1, an insulator 2, an attachment panel 3, a horn 6 and a needle electrode
5.
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[0005]
In this discharge type speaker, a discharge portion is formed between the needle electrode 5 and
the horn 6 which is a plate electrode. The discharge portion constitutes a part of the high
frequency oscillation circuit that causes high frequency discharge, and an unequal electric field is
formed between the needle electrode 5 and the horn 6, and a high frequency voltage is applied
thereto to thereby achieve high frequency. A discharge (plasma) is to be generated. As described
above, this discharge is also referred to as a flame discharge, and reference numeral 8 in FIG. 2
indicates a flame generated by the discharge in the discharge portion between the needle
electrode 5 and the horn 6. Since the needle electrode 5 side has a high electric field, flame
discharge occurs near the needle electrode 5 and extends to the horn 6 side.
[0006]
The needle-like electrode 5 is a member having a needle-like shape with a pointed distal end, and
the base end is covered with the insulating cylinder 4. The needle electrode 5 is connected to a
drive circuit (not shown). The drive circuit includes a high frequency oscillation circuit oscillating
at about 27 to 28 MHz, a modulation circuit in which the oscillation signal is modulated by an
audio signal, and a power supply circuit boosting the power supply voltage to a high voltage DC
voltage. The needle electrode 5 is made of, for example, a material suitable as a discharge
electrode, such as platinum and indium. The needle electrode 5 is attached to the base 1.
[0007]
The horn 6 is a conductive member formed of a metal such as brass or aluminum having good
processability, and constitutes a plate-like electrode. The inner circumferential surface of the
horn 6 is in the shape of a funnel that draws a gentle arc. On the outer peripheral surface of the
horn 6, a flat portion in contact with the mounting panel 3 described later and a hollow
cylindrical portion 62 having a narrow mouth extending from the flat portion are formed. The
outer diameter of the cylindrical portion 62 is substantially the same as the inner diameter of the
insulator 2 described later and the diameter of the hole of the mounting panel 3. The sound wave
moves in and out of the insulator 2 through the horn 6. Further, a step portion 61 is formed on
the inner peripheral surface of the cylindrical portion 62 by expanding the inner diameter.
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[0008]
A cylindrical quartz glass 7 which is an insulator is fitted in the expanded inner diameter portion
of the cylindrical portion 62. The outer diameter of the quartz glass 7 is substantially the same as
the expanded inner diameter portion of the cylindrical portion 62. Further, the thickness of the
quartz glass 7 is the same as the step of the step portion 61, and the inner circumferential
surface of the horn 6 and the inner circumferential surface of the quartz glass 7 are smoothly
continued.
[0009]
Since it is necessary to apply a high voltage to generate a high frequency discharge between the
needle electrode 5 and the horn 6, a high frequency oscillation circuit (not shown) is used to
oscillate a vacuum tube capable of withstanding high voltage. It is used as an active element. The
discharge current of the discharge path formed between the needle electrode 5 and the horn 6 is
fed back to the vacuum tube to constitute a high frequency oscillation circuit by self-oscillation.
Specifically, an audio signal is input to the high frequency oscillation circuit, and a high
frequency signal modulated by the audio signal is generated. Then, discharging using this high
frequency signal generates a sound wave corresponding to the audio signal.
[0010]
The discharge portion formed by the needle electrode 5 and the horn 6 is covered by the base 1,
the insulator 2 and the mounting panel 3.
[0011]
The base 1 is formed of a dielectric, and is grounded through a not-shown grounding wire.
A hole 11 is formed in the central portion of the base 1. The needle electrode 5 is inserted into
the hole 11 and attached to the base 1 in a state of being extended to a space surrounded by the
base 1, the insulator 2 and the mounting panel 3. The insulator 2 is a member surrounding the
periphery of the discharge portion, and is a cylindrical member formed of an insulating material.
The base 1 is attached to one end of the insulator 2 and the mounting panel 3 is attached to the
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other end.
[0012]
The mounting panel 3 is a plate-like material having an insulating property, and a hole is formed
in the central portion. The horn 6 is attached to the insulator 2 through the attachment panel 3,
and the cylindrical portion 62 of the horn 6 is inserted into the hole of the attachment panel 3.
The mounting panel 3 is a member corresponding to a baffle plate in a general speaker.
[0013]
Japanese Patent Application Laid-Open No. 55-140400 Published by Seibundo Shinkosha "Radio
and Experiment" December 2001 issue "100 years of speaker technology"
[0014]
By the way, in order for the speaker shown in FIG. 2 to function, the discharge needs to extend in
the direction of the horn 6.
However, since the horn 6 is entirely made of metal, the flame discharge may cause spark
discharge in the radial direction of the cylindrical portion 62, and the radially inner surface may
be destroyed by the spark discharge. In order to prevent this spark discharge, in the abovedescribed conventional discharge type speaker, the inner peripheral surface of the cylindrical
portion 62 is covered with the quartz glass 7 which is an insulator. However, the processing of
the quartz glass 7 is difficult in terms of accuracy, and the design is limited in size and the like.
Further, since it is difficult to make the quartz glass 7 thinner, it is disadvantageous when the
heat generated from the discharge portion during the flame discharge is radiated from the quartz
glass 7 to the outside through the horn 6.
[0015]
The present invention solves the problems of the conventional electroacoustic transducer using
the high frequency discharge described above, that is, by using a ceramic coating layer as an
insulator, the production is easy and the shape is arbitrarily designed. It is an object of the
present invention to provide an electroacoustic transducer excellent in heat dissipation and a
method of manufacturing the same, as well as capable of providing a thin coating.
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[0016]
The present invention includes a needle-like electrode, a plate-like electrode surrounding the
periphery of the needle-like electrode, a discharge portion formed between the needle-like
electrode and the plate-like electrode, and a discharge portion. A high frequency oscillation
circuit to be caused to generate an audio signal by taking out an audio signal modulated
according to the sound wave introduced into the discharge unit, or discharging the discharge unit
according to the high frequency signal modulated by the audio signal The plate-like electrode has
a funnel-like shape having a wide-mouthed portion and a narrow-mouthed cylindrical portion,
and the cylindrical portion has a tip-shaped outer periphery of the needle-like electrode. The
main feature is that the ceramic coating layer is provided on the inner circumferential surface of
the cylindrical portion.
[0017]
Furthermore, the present invention includes a needle electrode, a funnel-shaped plate electrode
surrounding the periphery of the needle electrode, a discharge portion formed between the
needle electrode and the plate electrode, and a discharge portion. And a high frequency
oscillation circuit for generating high frequency discharge in the unit, wherein an audio signal
modulated according to the sound wave introduced into the discharge unit is taken out, or a
discharge according to the high frequency signal modulated with the audio signal in the
discharge unit A method of manufacturing an electroacoustic transducer for converting sound
into voice by performing the method, wherein the plate electrode has a narrow cylindrical
portion, and the ceramic coating liquid is applied to the inner peripheral surface of the cylindrical
portion of the plate electrode. After spraying, assembling is performed to assemble an
electroacoustic transducer using a coating step of sintering to form a ceramic coating layer, a
plate-like electrode on which the formation of the ceramic coating layer is finished, a needle
electrode, and a high frequency oscillation circuit. And step The main features of the door.
[0018]
According to the present invention, by using the ceramic coating layer as the insulator provided
on the inner peripheral surface of the plate-like electrode surrounding the periphery of the
needle-like electrode, the production is easy and the shape can be arbitrarily designed, and the
coating is Because of its thinness, it is possible to provide an electroacoustic transducer excellent
in heat dissipation and a method of manufacturing the same.
[0019]
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It is a longitudinal cross-sectional view which shows the Example of the electroacoustic
transducer based on this invention.
It is a longitudinal cross-sectional view which shows the example of the electroacoustic
transducer by the conventional high frequency discharge.
[0020]
Hereinafter, as an embodiment of the electroacoustic transducer according to the present
invention, it will be described with reference to FIG. 1 showing an example of a discharge type
speaker.
The same reference numerals as in the prior art shown in FIG. 2 denote the same parts.
In the discharge type speaker shown in FIG. 1, a discharge portion is formed between the needle
electrode 5 and the horn 6 which is a plate electrode.
The discharge portion constitutes a part of a high frequency oscillation circuit that causes high
frequency discharge, and an unequal electric field is formed between the needle electrode 5 and
the horn 6, and a high frequency voltage is applied thereto to produce a high frequency
discharge. (Plasma) is to be generated. As described above, this discharge is also referred to as a
flame discharge, and reference numeral 8 in FIG. 1 indicates a flame generated by the discharge
in the discharge portion between the needle electrode 5 and the horn 6. Since the needle
electrode 5 side has a high electric field, flame discharge occurs near the needle electrode 5 and
extends to the horn 6 side.
[0021]
The needle-like electrode 5 is a member having a needle-like shape with a pointed distal end, and
the base end is covered with the insulating cylinder 4. The needle electrode 5 is connected to a
drive circuit (not shown). The drive circuit includes a high frequency oscillation circuit oscillating
at about 27 to 28 MHz, a modulation circuit in which the oscillation signal is modulated by an
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audio signal, and a power supply circuit boosting the power supply voltage to a high voltage DC
voltage. The needle electrode 5 is made of, for example, a material suitable as a discharge
electrode, such as platinum and indium. The needle electrode 5 is attached to the base 1.
[0022]
The horn 6 is a conductive member formed of a metal such as brass or aluminum having good
processability, and constitutes a plate-like electrode. The inner circumferential surface of the
horn 6 is in the shape of a funnel that draws a gentle arc. On the outer peripheral surface of the
horn 6, a flat portion in contact with the mounting panel 3 described later and a hollow
cylindrical portion 62 having a narrow mouth extending from the flat portion are formed. The
outer diameter of the cylindrical portion 62 is substantially the same as the inner diameter of the
insulator 2 described later and the diameter of the hole of the mounting panel 3. The sound wave
moves in and out of the insulator 2 through the horn 6. Further, a ceramic coating layer 9 is
formed on the inner circumferential surface of the cylindrical portion 62. The ceramic coating
layer 9 is an insulating layer which is considerably thinner than the quartz glass 7 used in the
conventional electroacoustic transducer.
[0023]
Since it is necessary to apply a high voltage to generate a high frequency discharge between the
needle electrode 5 and the horn 6, a high frequency oscillation circuit (not shown) is used to
oscillate a vacuum tube capable of withstanding high voltage. It is used as an active element. The
discharge current of the discharge path formed between the needle electrode 5 and the horn 6 is
fed back to the vacuum tube to constitute a high frequency oscillation circuit by self-oscillation.
Specifically, an audio signal is input to the high frequency oscillation circuit, and a high
frequency signal modulated by the audio signal is generated. Then, discharging using this high
frequency signal generates a sound wave corresponding to the audio signal.
[0024]
The discharge portion formed by the needle electrode 5 and the horn 6 is covered by the base 1,
the insulator 2 and the mounting panel 3.
[0025]
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The base 1 is formed of a dielectric, and is grounded through a not-shown grounding wire.
A hole 11 is formed in the central portion of the base 1. The needle electrode 5 is inserted into
the hole 11 and attached to the base 1 in a state of being extended to a space surrounded by the
insulator 2.
[0026]
The insulator 2 is a member surrounding the periphery of the discharge portion, and is a
cylindrical member formed of an insulating material. The base 1 is attached to one end of the
insulator 2 and the mounting panel 3 is attached to the other end. The mounting panel 3 is a
plate-like material having an insulating property, and a hole is formed in the central portion. The
horn 6 is attached to the insulator 2 through the attachment panel 3, and the cylindrical portion
62 of the horn 6 is inserted into the hole of the attachment panel 3. The mounting panel 3 is a
member corresponding to a baffle plate in a general speaker.
[0027]
As described above, in the discharge speaker as the electro-acoustic transducer according to the
present embodiment, the horn 6 is different from the discharge speaker as the conventional
electro-acoustic transducer shown in FIG. The step portion 61 is not formed, and the inner
peripheral surface of the cylindrical portion 62 is a smooth curved surface over the whole. A
ceramic coating layer 9 is formed on the inner peripheral surface of the cylindrical portion 62.
This ceramic coating layer 9 is a layer which is considerably thinner than the quartz glass 7 used
in the speaker as a conventional electroacoustic transducer, and has an insulating property. The
ceramic coating layer 9 is formed by sintering at a temperature of about 200 ° C. after spraying
with a ceramic coating spray onto the inner peripheral surface of the cylindrical portion 62 or
application with a brush of a ceramic coating liquid or the like. Can.
[0028]
In the manufacture of the discharge speaker as the electroacoustic transducer according to the
present embodiment, first, the coating of the ceramic coating liquid is performed on the inner
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peripheral surface of the cylindrical portion 62 of the horn 6. This application may be by spray
or brush application. Then, after the ceramic coating solution is applied, sintering is performed to
form a ceramic coating layer. Next, the horn 6 after the formation of the ceramic coating layer 9
is combined with the other members, the base 1, the insulator 2, the panel 3, the insulating
cylinder 4, and the needle-like electrode 5 according to the present embodiment. A discharge
speaker is created as a converter.
[0029]
Like the quartz glass, the ceramic coating layer 9 can prevent the occurrence of spark discharge
in the discharge speaker produced in this manner. Furthermore, since the ceramic coating layer 9
is an extremely thin layer, the heat generated in the discharge portion is transmitted to the horn
6 through the ceramic coating layer 9 and easily released from the horn 6 to the outside, so that
the heat dissipation is excellent. In addition, since the ceramic coating layer is easily formed by
application and sintering of the ceramic coating liquid, it is easy to make and the shape can be
designed arbitrarily.
[0030]
The illustrated embodiment has been described as a discharge speaker using high frequency
discharge. However, the present invention is not limited to this, and the particle velocity of the
discharge unit changes according to the particle velocity of the sound wave, and the equivalent
impedance of the high frequency discharge unit changes, thereby utilizing the phenomenon that
the oscillation signal from the high frequency oscillation circuit is modulated. It can be operated.
Therefore, the electroacoustic transducer according to the present invention can be used as a
microphone or a speaker. The principle of using the electroacoustic transducer according to the
present invention as a speaker will be described.
[0031]
The particle velocity of the discharge part formed by the needle electrode and the horn changes
with the particle velocity of the sound wave, and the equivalent impedance of the high frequency
discharge part changes. By changing the equivalent impedance of the discharge part by the
sound wave, the oscillation signal by the above oscillation circuit is modulated by the sound
wave. The modulation signal includes frequency modulation, ie, an FM modulation component,
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and amplitude modulation, ie, an AM modulation component, but includes more FM modulation
components. Therefore, by taking out the FM-modulated signal and inputting it to the FM
demodulation circuit, it can be converted into an audio signal corresponding to the sound wave
introduced from the sound wave introducing unit.
[0032]
Reference Signs List 1 base 11 hole 2 insulator 3 mounting panel 4 insulating cylinder 5 needle
electrode 6 horn 61 step portion 62 cylindrical portion 7 quartz glass 8 flame 9 ceramic coating
layer
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