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DESCRIPTION JPH10145893

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DESCRIPTION JPH10145893
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
condenser microphone suitable for business use, for example.
[0002]
2. Description of the Related Art A condenser microphone is known as a microphone, and the
microphone unit is configured as shown in FIG. 2, for example. That is, in FIG. 2, reference
numeral 30 denotes the microphone unit, and the diaphragm 31 is formed in a circular shape by
a conductive plate such as a metal plate, and is formed in an annular shape on the rear surface
by an insulating material. A back electrode 33 (fixed electrode) is provided with the spacer 32
interposed therebetween.
[0003]
The back electrode 33 is formed in a circular shape by a conductive member such as a metal
plate, and a plurality of through holes 34 are formed, and the rear surface of the diaphragm 31 is
opened to the rear of the back electrode 33 through the through holes 34. It is done.
[0004]
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Further, the air chamber member 35 is formed in a cup shape as a whole by an insulating
material, and a step 36 is formed inside the opening portion, and the back electrode 33 is located
here.
Further, the case 37 is formed in a cup shape by a conductive material such as metal, and the
through hole 38 is formed on the bottom surface thereof, and the above-mentioned components
31, 32, 33 are formed so that the diaphragm 31 faces the through hole 38. , 35 are provided
inside the case 37. Further, an annular fixing member 39 is provided in the case 37 so as to be in
contact with the rear portion of the air chamber member 35, and components provided in the
case 37 are fixed.
[0005]
Although not shown, the back electrode 33 is connected to the hot side of the front circuit
through the lead wire, and the diaphragm 31 is connected to the ground side of the front circuit
through the case 37 and through the lead wire. As an example, the diameter of the diaphragm 31
is 30 to 40 mm, and the distance between the diaphragm 31 and the back electrode 33 (the
thickness of the spacer 32) is 30 to 50 μ.
[0006]
According to such a configuration, the diaphragm 31 and the back electrode 33 constitute the
capacitor C30, and the diaphragm 31 vibrates as shown by a broken line by a sound wave, and
the capacitance of the capacitor C30 changes. At this time, the rear portion of the diaphragm 31
is opened to the air chamber (the space formed by the rear electrode 33 and the air chamber
member 35) at the rear portion of the back electrode 33 through the through hole 34. Can follow
the sound waves and vibrate.
[0007]
Therefore, if the change in capacitance of the capacitor C30 is extracted as an electric signal, the
signal is nothing other than a signal obtained by acoustic-electrical conversion of the sound wave
that has given vibration to the diaphragm 31, that is, the audio collected by the microphone unit
30. You can get a signal.
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[0008]
Incidentally, the capacitance of the capacitor C30 configured by the diaphragm 31 and the back
electrode 33 is 50 to 60 pF in the case of the above numerical example, and the capacitance
change by the sound wave is several pF.
[0009]
By the way, in the microphone unit 30 of FIG. 2, as is apparent from the above numerical
example, considerable mechanical accuracy is required for each component, and for example, the
thickness of the spacer 32 is required. The variation of V.sub.c is a variation of the capacitance of
the capacitor C30, and is a variation of the level of the output audio signal.
[0010]
On the other hand, the parts 32 and 35 holding the electrodes 31 and 33 must be formed of an
insulating material, for example, acrylic, but generally the insulating material has inferior
processing accuracy compared to metal and is inferior in hardness. There is.
[0011]
Thus, although the processing of the parts 32, 35 requires great care, it is still difficult to process
into complex and fine shapes.
If these problems are to be solved, the structure is generally complicated, which may lead to
deterioration in manufacturing stability and yield.
[0012]
The present invention seeks to eliminate the above-mentioned problems without causing such
problems.
[0013]
Therefore, in the present invention, a conductive diaphragm and a back electrode plate provided
on the back surface of the diaphragm are provided, and the back electrode plate is an insulating
plate and And an electrode plate provided on a surface facing the diaphragm among the
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insulating plates, wherein the vibration of the diaphragm due to the sound wave can be detected
by the change of the capacitance between the diaphragm and the electrode plate. It is to be a
condenser microphone that is taken out as.
Therefore, the electrode plate acts as a back electrode, and at this time, the insulating plate
supports the electrode plate, and the capacitance between the diaphragm and the electrode plate
changes according to the sound wave.
[0014]
DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 10 denotes a
microphone unit according to the present invention, and a diaphragm 11 is formed in a circular
shape by a conductive plate such as a metal plate, and a rear surface thereof The printed wiring
board 20 is provided with spacers 12 formed annularly of metal or the like in between.
[0015]
The printed wiring board 20 is formed in the same manner as a printed wiring board used for
general circuit wiring, and the whole functions as a back electrode plate and its wiring pattern
functions as a back electrode (fixed electrode). is there.
[0016]
That is, in the printed wiring board 20, the insulating board 21 is formed in a circular shape, for
example, by a porous ceramic plate impregnated with an epoxy resin, and the glass cloth
impregnated with the epoxy resin for reinforcement on both sides thereof. A layer (not shown) is
formed.
[0017]
Then, on the surface of the insulating substrate 21 facing the diaphragm 11, a wiring pattern 22
acting as a back electrode is formed in a circular shape so as not to reach the spacer 12 with
copper foil, for example.
Further, a plurality of through holes 23 are formed in the insulating substrate 21 and the wiring
pattern 22, and the rear surface of the diaphragm 11 is opened to the rear of the printed wiring
board 20 through the through holes 23. The pattern 22 is electrically connected to the wiring
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pattern 24 on the rear surface of the insulating substrate 21 by through hole processing.
[0018]
Such a printed wiring board 20 can be manufactured by the same process and operation as the
two-sided printed wiring board generally used.
[0019]
Furthermore, the air chamber member 15 is formed in a cup shape as a whole by a conductive
material such as metal, and the printed wiring board 20 is positioned so as to close the opening.
Further, the case 17 is formed in a cup shape by a conductive material such as metal, and the
through hole 18 is formed on the bottom surface of the case 17 so that the diaphragm 11 faces
the through hole 18. , 15 are provided inside the case 17.
Further, an annular fixing member 19 is provided in the case 17 so as to be in contact with the
rear of the air chamber member 15, and components provided in the case 17 are fixed.
[0020]
Then, although not shown, the wiring pattern 24 of the printed wiring board 20 is connected to
the hot side of the front circuit through the lead wire, and the diaphragm 11 is connected
through the case 17 to the ground side of the front circuit through the lead wire. Ru.
The size of the main part is the same as that of FIG.
[0021]
According to such a configuration, the capacitor C10 is configured by the diaphragm 11 and the
wiring pattern 22, and the diaphragm 11 is vibrated by a sound wave as indicated by a broken
line, and the capacitance of the capacitor C10 changes.
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At this time, the rear portion of the diaphragm 11 is opened to the air chamber (the space
formed by the printed wiring substrate 20 and the air chamber member 15) at the rear portion
of the printed wiring board 20 through the through hole 23. The plate 11 can vibrate following
the sound wave.
[0022]
Therefore, if the change in capacitance of the capacitor C10 is extracted as an electric signal, the
signal is nothing other than a signal obtained by acoustic-electrical conversion of the sound wave
that has given vibration to the diaphragm 11, that is, the audio collected by the microphone unit
10. You can get a signal.
[0023]
And, in this case, according to this microphone unit 10, since the back electrode plate is
constituted by the printed wiring board 20, as shown also in FIG. 1, a spacer for determining the
capacity of the main components, particularly the capacitor C10. 12, etc. can be formed of any
metal by any processing method, and can be formed with high accuracy.
Therefore, since the variation in the capacitance of the capacitor C10 can be suppressed, the
variation in the level of the output audio signal can be suppressed, and the signal level and the S
/ N of the design target can be obtained.
[0024]
In addition, since the insulating substrate 21 of the printed wiring board 20 which can originally
ensure sufficient insulation insulates the wiring pattern 22 acting as the back electrode, the
insulation between the back electrode (wiring pattern 22) and other portions Can be secured
enough.
Furthermore, since the back electrode plate is configured by the printed wiring board 20, the
wiring pattern 22 acting as the back electrode can be formed with sufficient accuracy for the
shape required electrically, and at the same time the insulating substrate 21 is also It can be
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formed in a shape required to support the wiring pattern 22.
Therefore, excellent characteristics can be obtained also from this point as a microphone unit of
a condenser microphone.
[0025]
Furthermore, if there is variation in the diameter of the insulating substrate 21 of the printed
wiring board 20, the printed wiring board 20 will be assembled unevenly in the left and right
direction in FIG. 1, but the capacity of the capacitor C10 is determined The area of the wiring
pattern 22 facing the diaphragm 11 can be formed with sufficient accuracy, so that the variation
in the diameter of the printed wiring board 20 does not matter. Further, even if the thickness of
the insulating substrate 21 varies, the distance between the wiring pattern 22 and the diaphragm
11 is not affected, so that the variation of the thickness of the insulating substrate 21 does not
matter.
[0026]
Further, the signal lines can be drawn out from the wiring pattern 22 which is the back electrode
through the wiring pattern 24 and the extraction is easy. Moreover, as apparent from FIG. 1, the
structure or shape of each part can be simplified, and the processing of each part is simple.
[0027]
In the microphone unit 10 described above, in order to convert the change in capacitance of the
capacitor C10 into an audio signal, a series circuit of the capacitor C10 and a resistor having a
relatively large value may be connected to a DC power supply. That is, if so, an audio signal can
be obtained from the resistor.
[0028]
Alternatively, the capacitor C10 is connected to the resonance circuit of the oscillation circuit,
and the oscillation frequency is FM-modulated by the capacitance change of the capacitor C10,
and the FM signal is FM-demodulated to obtain an audio signal.
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[0029]
The wiring pattern 22 and the through holes 23 can also be formed by applying a conductive
paint or the like in a plate shape.
[0030]
According to the present invention, since the back electrode is provided on the insulating plate,
there is no need to use an insulating part having a complicated shape in order to obtain
insulation between the diaphragm and the back electrode. The microphone unit can be realized
with a simpler structure.
In addition, the positional relationship between the diaphragm and the back electrode can be
obtained with sufficient accuracy, and a good output signal can be obtained.
[0031]
Furthermore, since the back electrode plate and the back electrode are configured by the printed
wiring board, each can be made into a free shape, and the position of the back electrode in the
back electrode plate can also be made arbitrary.
[0032]
Brief description of the drawings
[0033]
1 is a cross-sectional view showing an embodiment of the present invention.
[0034]
2 is a cross-sectional view for explaining the present invention.
[0035]
Explanation of sign
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[0036]
10 = microphone unit, 11 = diaphragm, 12 = spacer, 15 = air chamber member, 17 = case, 18 =
through hole, 19 = fixing member, 20 = printed wiring board, 21 = insulating substrate, 22 and
24 = Wiring pattern, 23 = through hole
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