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JPS5892199

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JPS5892199
[0001]
TECHNICAL FIELD OF THE INVENTION The present invention relates to an electrostatic acoustic
transducer suitable for condenser-type microphones, headphones, pickups and the like using
electrets. Technical Background of the Invention For example, as a condenser microphone using
an electret, as shown in FIG. 1, a spacer ring 4 is provided in front of a fixed electrode 3 formed
by forming a molecular dielectric 112 on a metal electrode plate 1. There is known one having a
so-called pack electret structure in which a thin film diaphragm 5 on which a thin film movable
electrode is vapor-deposited is disposed via a thin film movable electrode. Also, as shown in FIG.
2, a so-called wedge electret formed by arranging a thin film diaphragm 5 opposite to a polymer
dielectric layer 2 via a spacer ring 4 in front of a metal electrode plate 1 as a fixed electrode. It is
also known to have a shaped structure. In FIGS. 1 and 2, reference numeral 6 denotes a weir ring
having a thin film diaphragm 5 stretched. Background art tma point However, in a condenser
microphone having a structure as shown in FIG. 1, a thin film diaphragm 5 disposed at a slight
distance in front of the polymer dielectric layer 2 of the fixed electrode 3 is an electret It is easy
to be attracted electrostatically by the charge held by the polymer dielectric layer 2 which is
formed. This suction force (F) is represented by F = K (Q +, Qz) / r ", K is a multiplier, r is the
distance between the polymer dielectric layer 2 and the thin film diaphragm 51Il, and Ql and Ql
are high. It is a charge device held by the molecular dielectric layer 2 and the 81 m diaphragm 5.
When the absorbing force acts on the * S diaphragm 5 in this manner, the thin film diaphragm 5
is curved in the direction of the fixed electrode 3 as shown by a broken line as shown in FIG.
There is a drawback that the resonant frequency ("0") of the plate 5 is high and the output signal
is likely to be distorted. Furthermore, when the dark gap between the identification electrode 3
and the thin film diaphragm 5 can not be increased, the thin film diaphragm 5 is adsorbed to the
polymer dielectric 112 and becomes nonviable or a discharge occurs to cause the polymer
dielectric layer 2 There is a problem in that the electret degradation of the microphones is
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caused to shorten the life of the microphone. In addition, the sensitivity of the microphone is
likely to be varied due to the suction phenomenon, and in order to assemble the thin film
diaphragm 5 so as not to bend, the skill of the jaw structure is required, and the workability is
inferior to one. The condenser microphone using the electret having the configuration as shown
in FIG. 2 also has the same defect as that of FIG. The present invention was made to solve the
above-mentioned drawbacks, and an object thereof is to provide an electrostatic acoustic
transducer having a good dynamic range and frequency characteristics.
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention has a
diaphragm in which a magnetic layer having a good coercivity is formed on the front surface of
an electrode plate made of a conductive material having a good coercivity with a slight gap. By
arranging and forming a polymer dielectric layer on at least one of the electrode plate or the
opposing surface of the diaphragm, and by magnetizing the electrode plate and the second
magnetic layer so that they face each other with the same magnetic pole. It is characterized in
that the electrostatic attraction force is canceled by the repulsive force. Embodiments of the
Invention Embodiments of the invention will now be described in detail with reference to one
side. 3 and 4 are a cross-sectional view and an exploded perspective view in which the
electrostatic acoustic transducer of the present invention is used for a microphone. The same
reference numerals as in FIGS. 1 and 2 denote the same parts in FIG. In the figure, the fixed
electrode 3 is formed by forming a polymer dielectric material such as polycarbonate or Teflon
on one main surface of a conductive metal electrode plate 1 having good coercivity such as iron,
nickel, cobalt, etc. The electrode plate 1 is magnetized, for example, with the side of the
molecular dielectric layer 2 as the S pole and the opposite side as the N pole. In front of the fixed
electrode 3, an ill film diaphragm is disposed with a spacer ring 4 provided on the periphery
thereof. The thin 1IWT working plate 5 is composed of a movable electrode 8 in which a
magnetic layer 7 having a good coercive force is formed on the opposite surface to the fixed
electrode 3 and is stretched on the lower surface of the conductive film ring 6 and slightly
spaced from the fixed electrode 3 Are arranged opposite to each other. The magnetic material
layer 7 of the vibrating electrode plate 5 has a surface facing the fixed electrode 3 magnetized to
the S pole, and faces the same polarity as the metal electrode plate 1 of the fixed electrode 3, that
is, S poles. FIG. 46M is an exploded perspective view of the condenser microphone of the present
invention shown in FIG. The condenser type microphone configured in this manner grounds the
collar ring 6 holding the thin film diaphragm 5 and uses the metal electrode plate of the fixed
electrode 3 as the output end 9, and the vibration of the diaphragm 1 due to the sound wave
from the sound source An audio voltage is output from the terminal 9 via the output terminal 9,
and the output terminal 9 is connected to the gate G of the FET type transistor Q of the
impedance conversion circuit as shown in FIG. Output at low impedance. The symbol R1 is a bias
resistor, and the symbol R2 is a load resistor. Then, the metal electrode plate 1 of the fixed
electrode 3 and the magnetic body 117 of the thin film diaphragm 5 in the present invention are
magnetized in advance by the magnetizing device 10 as shown in FIG. This magnetizing device
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f10 has a substantially horseshoe shape, and the pole plate 11 is provided opposite to the open
opposite end thereof, and for example, the lil's diaphragm 5 is disposed between the opposing
pole plates 11 and attached. If a direct current is supplied to the coil 12 wound around the
magnetic device f10, the * m diaphragm 5 can be magnetized.
In the condenser type microphone of the present invention thus configured, since the metal
electrode plate 1 of the fixed electrode 3 and the magnetic material layer 7 of the wedge
diaphragm 5 are disposed opposite to each other by the same magnetic pole, the repulsive force
is generated between them. Even if the attraction force due to static electricity acts between the
thin film diaphragm 5 and the polymer dielectric 112 of the fixed electrode 3, the attraction
force is canceled by the repulsion of the same pole rod, and the thin film diaphragm There is no
deflection of 5. As a result, since the dark gap between the thin film diaphragm 5 and the fixed
electrode 3 becomes constant over the entire surface, the diaphragm 5 can be sufficiently
vibrated even for a large input sound, and the dynamic range is improved. To prevent electret
degradation of the molecular dielectric layer 2 and extend the life of the microphone.
Furthermore, since the thin film diaphragm 5 does not bend, distortion does not occur in the
output signal, and the sound quality becomes good over a wide frequency band because it
becomes close to the push-pull operation. When a spiral coil is formed on the movable electrode
8 of the WI diaphragm 5 by etching or the like, it becomes a dynamic transducer, and the
vibration of the thin film diaphragm 5 causes the coil to move from the metal electrode plate 1 of
the fixed electrode 3. Therefore, the electromotive force can be obtained also from both ends of
the coil of the movable electrode 8 to constitute a transducer which is distinguished from the
capacitor type transducer. Therefore, from the capacitor type microphone in which the coil is
formed in this way, two systems of output of a signal obtained from the output terminal 9 of the
metal electrode plate 1 and a signal obtained from both ends of the coil of the movable electrode
8 are obtained. -It becomes possible to constitute a microphone. FIG. 7 shows another
embodiment of the electrostatic acoustic transducer according to the present invention, in which
two fixed electrodes 3 are spaced apart to make the polymer dielectric 2 face each other, and the
fixed electrode is arranged. It shows a configuration in which the M ? vibrational root 5 is
disposed in a sandwiching manner via the spacer 4 in 3 fll. The WI film diaphragm 5 is formed
with magnetic layers 7 on both main surfaces of the movable electrode 8, and is magnetized so
that the metal electrode plate 1 and the magnetic layer 7 facing each other face the same
magnetic pole, The metal electrode plate 1 of the fixed electrode 3 is connected to both ends of
the primary side having the intermediate tap P of the impedance conversion transformer 1. An
impedance-converted output is obtained from the output terminal 13.14 of the secondary
winding of the transformer T. Reference symbols R3 and R4 denote high-value resistors inserted
between the metal electrode plate 1 and the movable electrode 8, respectively. The electrostatic
acoustic transducer of this configuration is referred to as a push-pull type pack electret, and as
shown in the embodiment of FIG. Even if there is variation (variation in charge holding amount)
of the polymer dielectric 2 in the electrode 3, the thin film diaphragm '5 and the fixed electrode 3
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will be disposed substantially in parallel, so that the sound quality is very good. An
electroacoustic conversion 1 is obtained, which is very suitable, for example, for a microphone or
headphones.
As described in detail in the invention, the electrostatic acoustic transducer of the present
invention arranges a thin film diaphragm having a magnetic layer having a good coercivity
forward of an electrode plate made of a conductive material having a good coercivity. In addition,
since the electrode plate and the magnetic layer are made to face each other by the same
electrode, it is possible to offset the attraction of the diaphragm by the polymer dielectric by the
repulsion of the magnetic poles, and the diaphragm is sufficiently vibrated. It has the advantages
of being secured, having a wide dynamic range, less distortion, and a long life. The electrostatic
acoustic transducer according to the present invention is a so-called wedge electret type static
transducer in which a diaphragm in which a polymer dielectric is formed opposite to a fixed
electrode in front of the fixed electrode made of a metal electrode plate. It is needless to say that
the present invention can be applied to an electroacoustic transducer.
[0002]
Brief description of the drawings
[0003]
1 and 2 are sectional views showing a conventional electrostatic acoustic transducer, and FIGS. 3
and 4 are a sectional view and an exploded perspective view showing one embodiment of the
electrostatic acoustic transducer of the present invention. FIG. 5 is an impedance conversion
circuit diagram, and FIG. 6 is used for the electrostatic acoustic transducer of the present
invention!
?? FIG. 7 is a cross-sectional view showing another embodiment of the present invention. 1 и и и и
и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и molecular dielectric layer 3 и и и и и и и и и и и и и и и и и и и и и
и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и Spacer ring 5 и и и и и и и и и и и и и и и и и и и и и и
и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и Electrode 10
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