JPS61247200

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DESCRIPTION JPS61247200
[0001]
FIELD OF THE INVENTION This invention relates to electret condenser microphones. Prior Art
FIG. 3 is a cross-sectional view of a conventional electret condenser microphone. In FIG. 3, 1 is a
cloth, 2 is a cylindrical metal case having a sound hole 2a on the top surface, 3 is a film formed
by uniformly stretching a vibrating film 4 made of an electret material having a metal surface by
metal deposition or the like. Reference numeral 5 denotes a gap spacer, 6 denotes a fixed
electrode, 6a denotes a damping hole, 7 denotes an insulator, 8 denotes an FET, 8a denotes an
input lead, 8b denotes an output lead, 9 denotes a printed circuit board, and 10 denotes a back
air chamber. The output lead 8b is fixed to the printed circuit board 9 by the soldered portion 9a.
In the present description, a wheel electret type using an electret material for the vibrating
membrane 4 is taken as an example, but the same applies to a pack electret type where an
electret material is provided on the fixed electrode 6 side. The fixed electrode 6, the insulator 7,
the FET 8, and the printed circuit board 9 can be considered as one amplifier block, and the
above-described components are fixed to the metal case 2 by the caulking portion 2b after being
inserted. The input lead 8a of the FET 8 is electrically connected to the fixed electrode 6 by spot
welding or contact. In the latter case, the fixed electrode 6 is fixed to the insulator 7 by press
fitting or the like. In the electret condenser microphone configured as described above, the
graphic 1 is for dustproofing or damping of the high-frequency characteristic, and the vibrating
membrane 4 is configured on the front side (sound introducing side) Therefore, it is necessary to
make the sound hole 2a of the metal case 2 smaller to some extent (about .phi.1 fflII or less) in
order to eliminate the drawing cloth 1 and it is necessary to provide a plurality of them in terms
of acoustic characteristics. It is easy to cause damage such as a thousand and the like, and
maintenance is very difficult. An object of the present invention is to provide an electret
condenser microphone having a structure in which the sound holes on the top surface of the
metal case are practically unchanged and dust and the like are practically difficult to enter
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without changing the conventional one It is. MEANS FOR SOLVING THE PROBLEMS In order to
achieve the above object, according to the present invention, a fixed electrode is a front side
(sound introduction (III), and a vibrating membrane (movable electrode) having a metal surface
stretched over a membrane ring). It is configured to be on the back side. Therefore, according to
the present invention, since the braking hole of the fixed electrode is also used as the sound wave
introducing hole, the cloth can be eliminated without deteriorating the dustproof effect and the
high frequency characteristic, and the number of parts can be reduced. Embodiment The
configuration of an embodiment of the present invention will be described below with reference
to the drawings.
FIG. 1 is a cross-sectional view showing an embodiment of the present invention, and the same
parts as FIG. 3 are indicated by the same reference numerals. In FIG. 1, the fixed electrode 6 is
the front surface m <the sound wave introduction side), and the vibrating membrane 4 (movable
electrode) is the back surface side. The damping hole 6a of the fixed electrode 6 is generally a
small hole of about φ1 ma + or less, and can be said to be an optimum size for foreign
substances such as dust and in terms of acoustic characteristics. Therefore, it is not necessary to
make the sound hole 2a of the metal case 2 smaller even if the drawing cloth 1 is eliminated.
This may be the same level as in the prior art, and the fixed electrode 6 plays a sufficient role as
protection of the diaphragm 4. Although the FET 8 of this embodiment uses the dual side type in
which the input / output leads 8a and 8b are led out from both sides, as shown in FIG. 3, any
single side type may be used. Absent. FIG. 2 shows another embodiment of the present invention,
and contrary to FIG. 1, the sound hole 2a side of the top surface of the metal case 2 is the printed
board 9 side which is the output terminal, and the caulking portion is on the fixed electrode 6
side. It is configured to be fixed by 2b. If caulking is performed on the front side as in FIG. 2 in
the prior art of FIG. 3, the diaphragm 4 will be distorted due to the caulking portion on the
membrane ring 3, but in the case of FIG. I do not have to worry about that. In the embodiment of
the present invention, although not particularly shown, it is conceivable to adopt the following
method regarding the ventilation (near leak) to the outside of the back air chamber 10. For
example, the insulator 7 is provided with one or a plurality of notches and the like, and the back
air chamber 10 is ventilated between the metal case 2 and the inside 4 articles such as the
insulator 7 etc. In this method, a groove or the like is provided in the fixed electrode 6 or the gap
spacer 5 and acoustically ventilates with the outside air from the front side. According to such a
method, it is possible not only to realize a reliable near leak but also to control the frequency
characteristics such as lowering the frequency characteristics in the low band by appropriately
setting the acoustic constant. Effects of the Invention As described above, according to the
present invention, the fixed electrode is the front side (the sound wave introduction side) and the
vibrating membrane (the movable electrode) is the back side. There is no need to make the sound
hole on the top surface of the metal case particularly small, because it is possible to prevent
protection and foreign matter from entering. In addition, since the fixed electrode is on the front
side, the back air chamber can be made larger by the inner part of the membrane ring, so the
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sensitivity can be increased if the overall height of the electret condenser microphone is the same
as conventional, and thinner if conventional. It also has the advantage of being configurable.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a sectional view showing an electret condenser microphone according to an embodiment
of the present invention, FIG. 2 is a sectional view showing another embodiment of the present
invention, and FIG. 3 is a sectional view of a conventional electret condenser microphone .
2 · · · · · · · · Metal case, · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
· · · · · fixed electrode, 6a · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · FET FET. Name of agent
Attorney Nakao Toshio and others 1 person Figure 1! 2 Figure
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