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JP2006287326

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DESCRIPTION JP2006287326
PROBLEM TO BE SOLVED: To generate noise due to electrostatic coupling between an external
noise source and a fixed pole in a unidirectional condenser microphone unit in which a terminal
plate having an opening of a rear acoustic terminal is fixed to the rear end of a cartridge case To
prevent. SOLUTION: A cylindrical cartridge case having a front acoustic terminal on one end side
and having the other end opened is provided, and the other end side of the case is closed by a
terminal plate 30, and a rear acoustic terminal is mounted on the terminal plate 30. An
unidirectional transducer microphone unit in which an opening 32 is formed, and an impedance
converter (FET) 31 and a chip-type electronic component 40 for protecting the impedance
converter are mounted on a terminal plate 30. The chip-type electronic component 40 is
disposed on the opening 32 so as to close a part of the opening 32 to form a small opening 32a.
[Selected figure] Figure 3
Unidirectional Condenser Microphone Unit
[0001]
The present invention relates to a unidirectional condenser microphone unit, and more
particularly to a technique for preventing noise generation due to electrostatic coupling between
an external noise source and a fixed pole.
[0002]
In the condenser microphone unit, the diaphragm assembly in which the diaphragm and the
fixed pole are combined facing each other through the spacer is housed in the cylindrical
cartridge case, but mainly in the electret type model, the rear end of the case is A terminal board
(circuit board) on which an FET (field effect transistor) as an impedance converter is mounted is
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disposed in the opening, and the rear end of the case is crimped to fix the terminal board.
[0003]
In the unidirectionality, in addition to the front acoustic terminal, a rear acoustic terminal is
provided to make the sound wave from the sound source act on the back side of the diaphragm,
but the opening that becomes the rear acoustic terminal is pressed on the side of the cartridge
case In the case of forming holes by processing or the like, the cost is high, so at present most of
the products are made to have the opening of the rear acoustic terminal in the terminal board.
A unidirectional condenser microphone unit according to one example will be described with
reference to FIG.
[0004]
This uni-directional condenser microphone unit has a cylindrical cartridge case 10 made of an
aluminum material or the like having an opening 11 of a front acoustic terminal at one end and
an opening at the other end. The diaphragm assembly 20 is accommodated.
[0005]
The diaphragm assembly 20 includes a diaphragm 21 tensioned to a support ring (diaphragm
ring) 22 with a predetermined tension, and a fixed electrode 23 supported by an electrically
insulating pedestal 24. And the fixed pole 23 are disposed opposite to each other via a spacer
(not shown).
[0006]
An electrode lead-out rod 26 electrically connected to the fixed electrode 23 is provided
substantially at the center of the pedestal 24. In the electret type model, the surface of the fixed
electrode 23 facing the diaphragm 21 is polarized by corona discharge or the like. The electret
film (not shown) is attached.
[0007]
In addition, a terminal board (circuit board) 30 on which an FET 31 as an impedance converter is
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mounted is disposed in the opening on the other end side of the cartridge case 10, and the
opening edge 12 of the cartridge case 10 is curled inward. The terminal board 30 is fixed by this.
By the pressing force by this caulking, the respective components of the diaphragm assembly 20
are integrally joined without rattling, and the electrical connection between the electrode lead
rod 26 and the gate electrode of the FET 31 is secured.
[0008]
As shown in the plan view of FIG. 6 (a) and the cross-sectional view of FIG. 6 (b), the terminal
plate 30 is provided with an opening 32 as a rear acoustic terminal. The sound passage holes
24a and 23a are bored in the base 24 and the fixed pole 23 respectively so as to reach the back
side of the space, and between the sound passage holes 24a and 23a in order to obtain
predetermined frequency response characteristics etc. A sound resistance material 25 such as a
felt material is interposed.
[0009]
It is preferable that the opening 32 of the terminal plate 30 be acoustically large.
However, when the opening 32 is enlarged, as schematically shown in FIG. 1, the external noise
source A (for example, discharge noise of a fluorescent lamp) and the fixed electrode 23 are
electrostatically coupled through the opening 32 and noise ( Hum) may occur.
[0010]
One of the methods to prevent this is a method of making many small holes in the terminal plate
30. However, this restricts the mounting positions of lead wires and components formed on the
terminal plate 30.
Particularly in recent years, in order to prevent the generation of noise due to electromagnetic
waves radiated from the mobile phone, the terminal board 30 is mounted with electronic
components such as a capacitor for preventing high frequency intrusion and a Zener diode for
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preventing destruction of FET due to static electricity. Therefore, it is not preferable to make
many small holes in the terminal plate 30.
[0011]
Therefore, an object of the present invention is to provide a unidirectional directivity condenser
microphone unit in which a terminal board is fixed to the rear end of the cartridge case by
caulking and the opening of the rear acoustic terminal is formed in the terminal board. An object
of the present invention is to form a large number of substantially small rear acoustic terminal
openings in an electronic component to be mounted to prevent noise generation due to
electrostatic coupling between an external noise source and a fixed pole.
[0012]
In order to solve the above problems, the present invention includes a cylindrical cartridge case
having a front acoustic terminal at one end and an open at the other end, and a diaphragm on the
front acoustic terminal side in the cartridge case. A diaphragm assembly in which the fixed plate
and the fixed pole are combined facing each other via a spacer is disposed, the other end of the
cartridge case is closed by the terminal plate, and the terminal plate has an opening serving as a
rear acoustic terminal. In the unidirectional directivity condenser microphone unit, the chip type
electronic component is formed, and the impedance converter and the chip type electronic
component for protecting the impedance converter are mounted on the terminal board. It is
characterized in that it is disposed on the opening so as to close a part of the opening.
[0013]
According to a preferred aspect of the present invention, the opening is formed as a long hole,
and the chip-type electronic component is disposed on the opening leaving an opening at both
ends of the long hole.
[0014]
Further, the chip type electronic component includes a capacitor element for preventing high
frequency intrusion and a zener diode element for preventing electrostatic breakdown, and the
capacitor element and the zener diode element are in parallel to form a ground terminal of the
audio signal output unit. And the signal hot side terminal and between the ground terminal and
the signal cold side terminal, respectively.
[0015]
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According to the present invention, by arranging the chip-type electronic component so as to
close a part of the opening of the rear acoustic terminal formed in the terminal plate, the opening
becomes smaller, and this small opening is the chip-type electronic component Therefore, noise
generation due to electrostatic coupling between the external noise source and the fixed pole can
be prevented.
In addition, restrictions on the arrangement of the chip-type electronic components are
alleviated, and the degree of freedom in the design of the terminal plate is enhanced.
[0016]
Next, embodiments of the present invention will be described with reference to FIGS. 1 to 4, but
the present invention is not limited thereto.
1 is a cross-sectional view showing the internal structure of the unidirectional directivity
condenser microphone unit according to the present invention, FIG. 2 is a plan view showing a
state before component mounting of a terminal board, and FIGS. 3 (a) and 3 (b) are after
component mounting. A plan view and a sectional view showing the terminal board, and FIG. 4 is
a circuit diagram showing a connection state of parts for protecting the FET.
The same reference numerals are used for constituent elements which may be regarded as
identical or identical to the conventional example of FIG. 5 described above.
[0017]
As shown in FIG. 1, this unidirectional condenser microphone unit has a cylindrical cartridge case
10 made of, for example, an aluminum material, having an opening 11 of a front acoustic
terminal at one end and an opening at the other end. The diaphragm assembly 20 is housed in
the cartridge case 10.
[0018]
The diaphragm assembly 20 includes a diaphragm 21 tensioned to a support ring (diaphragm
ring) 22 with a predetermined tension, and a fixed electrode 23 supported by an electrically
insulating pedestal 24. And the fixed pole 23 are disposed opposite to each other via a spacer
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(not shown).
[0019]
An electrode lead-out rod 26 electrically connected to the fixed electrode 23 is provided
substantially at the center of the pedestal 24. In the electret type model, the surface of the fixed
electrode 23 facing the diaphragm 21 is polarized by corona discharge or the like. The electret
film (not shown) is attached.
[0020]
Further, in the opening on the other end side of the cartridge case 10, the terminal plate 30 on
which the FET 31 as an impedance converter is mounted is disposed, and the terminal plate 30 is
curled by curling the open end 12 of the cartridge case 10 inward. Is fixed.
By the pressing force by this caulking, the respective components of the diaphragm assembly 20
are integrally joined without rattling, and the electrical connection between the electrode lead
rod 26 and the gate electrode of the FET 31 is secured.
[0021]
A printed circuit board is used for the terminal board 30.
The terminal plate 30 is provided with openings 32 of the rear acoustic terminal. In this example,
as shown in FIG. 2, the openings 32 are concentrically arranged at intervals of 90 ° as elongated
holes.
In FIG. 2, reference numerals 30 a and 30 b denote insertion holes of the source terminal and the
drain terminal of the FET 31.
Further, although not shown in FIG. 2, lead wires are formed on the terminal plate 30 in a
predetermined pattern.
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[0022]
The chip-type electronic component 40 is mounted on the terminal plate 30 in addition to the
FET 31. In the case of the present invention, as shown in FIG. 3, the chip-type electronic
component 40 is disposed across the opening 32, The portion 32 is partially closed by the chiptype electronic component 40.
[0023]
In the example of FIG. 3, the chip-type electronic component 40 is arranged to straddle the
opening 32 along the short axis direction at the central portion of the long hole-like opening 32,
thereby making small openings at both ends of the opening 32. Portions 32a, 32a are left, and
the small openings 32a, 32a act as rear acoustic terminals.
[0024]
As described above, by arranging the chip-type electronic component 40 in each of the openings
32, a total of eight small opening portions 32a, 32a can be made in the terminal plate 30, and
this is small in the terminal plate 30. Since it is substantially equivalent to opening a large
number of holes, noise generation due to electrostatic coupling between the fixed pole 23 and
the external noise source A (see FIG. 5) such as a fluorescent lamp is prevented.
[0025]
Further, by arranging the chip-type electronic component 40 on the opening 32, restrictions on
the arrangement of the chip-type electronic component 40 are alleviated as compared with the
case where a large number of small holes are made in the terminal plate 30, Freedom of board
design is enhanced.
[0026]
As described above, in order to dispose the chip-type electronic component 40 on the opening 32
and make a part of the opening 32 a small opening portion 32 a, the size of the chip-type
electronic component 40 (occupying on the terminal plate 30) The size and shape of the opening
32 may be determined in relation to the base area).
[0027]
In the above example, the openings 32 are long holes so that the small openings 32a and 32a
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can be formed at both ends, but as another example, the chip-type electronic component 40 has
different lengths in width and width In the case of a rectangular shape, the opening 32 may be
formed in a circular shape whose diameter is an intermediate length between the vertical width
and the horizontal width.
Also, in some cases, the chip-type electronic component 40 may be arranged so that the small
opening portion 32 a is formed only on one side of the opening 32 instead of both ends.
[0028]
With the spread of mobile phones in recent years, opportunities for using mobile phones in the
vicinity of a microphone are increasing.
Since a very strong electromagnetic wave is emitted from the portable telephone, if the
electromagnetic wave enters the cartridge case 10, it may be detected by the FET 31 and noise
may be generated.
In addition, the FET 31 may be destroyed by static electricity.
[0029]
In order to prevent these problems, a capacitor element for preventing high frequency intrusion
and a zener diode element for preventing electrostatic breakdown are used for the chip-type
electronic component 40, and each of these elements has a circuit diagram as shown in FIG.
Connected
[0030]
FIG. 4 shows an audio signal output unit provided on the terminal plate 30. The capacitor
element 41 and the zener diode element 42 are in parallel, and between the ground terminal E of
the audio signal output unit and the signal hot side terminal SH, and the earth It is respectively
connected between the terminal E and the signal cold side terminal SC.
[0031]
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Sectional drawing which shows the internal structure of the unidirectional directivity condenser
microphone unit by this invention.
The top view which shows the state before components mounting of a terminal board.
(A) The top view which shows the terminal board after component mounting, (b) The sectional
view.
The circuit diagram which shows the connection state of the components for FET protection.
Sectional drawing which shows the internal structure of the conventional unidirectional
condenser microphone unit.
(A) The top view which shows the terminal board currently integrated in FIG. 5, (b) The sectional
view.
Explanation of sign
[0032]
Reference Signs List 10 cartridge case 11 opening (front acoustic terminal) 20 diaphragm
assembly 21 diaphragm 23 fixed pole 24 pedestal 30 terminal plate 31 FET (impedance
converter) 32 opening (rear acoustic terminal) 32a small opening 40 chip type Electronic parts
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