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DESCRIPTION JP2010178009

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DESCRIPTION JP2010178009
An object of the present invention is to secure a shield of a shield member covering a front
acoustic terminal from the inside of a unit case, and to prevent noise generation particularly due
to an electromagnetic wave radiated from a mobile phone. A cylindrical unit case 10 made of a
metal material having a front acoustic terminal 11 at one end, an electrostatic type
acoustoelectric converter 20 housed in the unit case 10, and an acoustoelectric converter 20 In
the condenser microphone unit including the shield member 30 disposed between the front
portion and the front acoustic terminal 11 and covering the front acoustic terminal 11 from the
inside of the unit case 10, the inner wall surface of the unit case 10 as the shield member 30. A
shield 32 plate is used which is made of a metal perforated plate integrally having a plurality of
locking pieces 33 incorporated with elastic deformation. [Selected figure] Figure 1
コンデンサマイクロホンユニット
[0001]
The present invention relates to a condenser microphone unit, and more particularly to an
electromagnetic wave shielding member provided on a front acoustic terminal.
[0002]
As shown in the plan view of FIG. 3 and the exploded sectional view of FIG. 4 (an exploded
sectional view taken along the line A-A of FIG. 3), the condenser microphone unit has a unit case
10, a unit case as a general configuration. And an acoustoelectric transducer 20 of the
electrostatic type housed in 10.
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[0003]
The unit case 10 is formed in a cylindrical shape made of a metal material such as aluminum or
brass alloy, for example, the front acoustic terminal 11 is formed on one end side directed to the
sound source side during sound collection, and the other end is acoustoelectric conversion It is
an opening 12 for storing the container 20 and the like.
[0004]
In this example, as shown in FIG. 3, the front acoustic terminal 11 has a long first slit hole 11a
and a short second slit hole cut from the periphery of one end of the unit case 10 toward the
center. 11b are alternately formed, but alternatively, the front acoustic terminal 11 may be
formed of one circular opening formed coaxially with the unit case 10.
[0005]
In the acoustoelectric converter 20, a diaphragm 21 stretched on a support ring (diaphragm
ring) 22 and a fixed electrode 23 supported by an insulating seat 24 are disposed opposite to
each other via an insulating spacer 25. A type of capacitor element is included.
[0006]
Since the condenser microphone unit according to this conventional example is unidirectional,
the fixed electrode 23 is a porous plate, and the insulating seat 24 is provided with a sound hole
24a as a rear acoustic terminal. The sound wave from the rear portion acoustic terminal 24 a is
configured to act on the back side of the diaphragm 21.
[0007]
Further, an electrode terminal rod 41 electrically connected to the fixed pole 23 is drawn out
from the insulating seat 24 by conductive means such as lead wiring (not shown).
The electrode terminal rod 41 is electrically connected to a gate electrode of an FET (field effect
transistor) as an impedance converter (not shown) disposed in the opening 12 of the unit case
10.
[0008]
In the unit case 10, a shield member 30 covering the front acoustic terminal 11 from the inner
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surface side is provided in order to prevent foreign objects and extraneous electromagnetic
waves from entering from the front acoustic terminal 11 (see Patent Document 1).
[0009]
Usually, a metal mesh (metal mesh) 31 is used for the shield member 30.
As the metal mesh 31 of this type, a stainless steel mesh made of, for example, a wire diameter of
0.1 mm, # 100 mesh, and SUS 304 is employed.
[0010]
The metal mesh 31 is disposed on the inner surface side of the front acoustic terminal 11 and
fixed by the adhesive. However, the front acoustic terminal 11 is formed on one end side of the
unit case 10 to prevent the appearance from being damaged by the adhesive extrusion. For
example, it is fixed to the inner surface of the front wall present in the central portion of the
rubber with a rubber adhesive.
[0011]
After fixing the metal mesh 31 as described above, the condenser microphone unit
accommodates the acoustoelectric converter 20 in the unit case 10 and cuts a lock ring 27
having an external thread from the back thereof into the inner wall of the unit case 10 It is
assembled by screwing and tightening the provided female screw 13.
[0012]
When the unit case 10 is made of, for example, an aluminum material which is easily plastically
deformed, the acoustoelectric converter 20 may be fixed by caulking the open end edge of the
rear portion inside.
[0013]
The shield by the metal mesh 31 is effective for radio waves in the VHF and UHF bands used for
broadcasting and the like, but when a mobile phone that has been widely spread in recent years
is used near the microphone, Noise may be generated by electromagnetic waves.
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[0014]
That is, the electromagnetic wave emitted from the mobile phone has a high frequency and a
short wavelength, and within the range of several centimeters to several tens of centimeters, the
electric field strength is several tens of thousands times the electric field strength generated in
the city by commercial radio waves. In order to reach the fixed pole 23 through the opening of
the metal mesh 31, noise may be generated.
[0015]
One of the causes is that the metal mesh 31 is exclusively fixed to the unit case 10 by the
adhesive and the electrical connection with the unit case 10 is uncertain, but the other cause is
the metal mesh 31. In the case of the plain weave, electrical connection is made at the
intersections of the vertical lines and the horizontal lines, so that the shielding property of the
mesh itself is not uniform.
[0016]
JP 2004-343368 A
[0017]
Therefore, an object of the present invention is to ensure the shield of the shield member
covering the front acoustic terminal from the inside of the unit case, and to prevent the noise
generation particularly due to the electromagnetic wave emitted from the mobile phone.
[0018]
In order to solve the above problems, the present invention provides a cylindrical unit case made
of a metal material having a front acoustic terminal on one end side, an electrostatic type
acoustoelectric converter housed in the unit case, and the above. In a condenser microphone unit
including a shield member disposed between an acoustic-electric converter and the front acoustic
terminal and covering the front acoustic terminal from the inside of the unit case, the unit case as
a shield member as the shield member The present invention is characterized in that a shield
plate made of a metal porous plate integrally having a plurality of locking pieces which are
elastically deformed with respect to the inner wall surface of the frame is used.
[0019]
According to a preferred aspect of the present invention, each of the locking pieces is integrally
connected to the peripheral edge of the shield plate at equal intervals as a triangular shape, and
when inserted into the unit case, the unit case It is bent at a predetermined angle from the
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peripheral edge of the shield plate to the opposite side to the front acoustic terminal so as to be
press-contactable to the inner wall surface.
[0020]
In the present invention, the front acoustic terminal may be formed of a plurality of slit holes,
and the front acoustic terminal may be formed of one circular opening coaxially formed with the
unit case. It is also good.
[0021]
According to the present invention, as a shield member for covering the front acoustic terminal
from the inside of the unit case, the metal integrally has a plurality of locking pieces in the
peripheral edge portion that are elastically deformed with respect to the inner wall surface of the
unit case. By using a shield plate made of a perforated plate, the shield plate can be securely
connected electrically and mechanically to the unit case, and the shield plate is a perforated plate
made of metal, and the shieldability is uniform over the entire surface. Since high frequency
current resulting from the external electromagnetic wave flows to the unit case without entering
the unit case, noise generation due to the external electromagnetic wave can be prevented.
[0022]
In addition, the locking pieces are formed into a triangle shape and integrally connected to the
peripheral edge of the shield plate at equal intervals, and the peripheral edge of the shield plate
can be pressed against the inner wall surface of the unit case when inserted into the unit case. By
bending the shield plate at a predetermined angle toward the opposite side to the front acoustic
terminal, the shield plate can be easily fixed in the unit case simply by pushing the shield plate
into the unit case.
[0023]
FIG. 2 is an exploded cross-sectional view of a condenser microphone unit according to the
present invention.
The top view which shows the shield member used by this invention.
The top view seen from the front acoustic terminal side of the conventional condenser
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microphone unit.
FIG. 4 is an exploded cross-sectional view along the line AA of FIG. 3;
[0024]
Next, an embodiment of the present invention will be described with reference to FIGS. 1 and 2,
but the present invention is not limited thereto.
In the description of this embodiment, the same reference numerals as in the conventional
example described in FIGS. 3 and 4 above denote constituent elements that do not require
modification.
[0025]
As shown in FIG. 1, the condenser microphone unit according to this embodiment also includes a
unit case 10 and an electrostatic type acoustoelectric converter 20 housed in the unit case 10 as
a basic configuration.
[0026]
The unit case 10 is formed in a cylindrical shape made of a metal material such as aluminum or
brass alloy, for example, the front acoustic terminal 11 is formed on one end side directed to the
sound source side during sound collection, and the other end is acoustoelectric conversion It is
an opening 12 for storing the container 20 and the like.
Further, in this embodiment, on the inner wall of the unit case 10, a female screw 13 in which a
lock ring 27 described later is screwed is formed.
[0027]
With reference to FIG. 3 together, the front acoustic terminal 11 has a long first slit hole 11 a
and a short second slit hole cut from the periphery of one end side of the unit case 10 toward the
center. The front acoustic terminals 11 may be formed as one circular opening coaxially formed
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with respect to the unit case 10.
[0028]
In the acoustoelectric converter 20, a diaphragm 21 stretched on a support ring (diaphragm
ring) 22 and a fixed electrode 23 supported by an insulating seat 24 are disposed opposite to
each other via an insulating spacer 25. A type of capacitor element is included.
[0029]
In the case of unidirectionality, the fixed electrode 23 is a porous plate, and a sound hole 24a as
a rear acoustic terminal is formed in the insulating seat 24, and a sound wave from the rear
acoustic terminal 24a is a diaphragm. Act on the back side of 21.
[0030]
Further, an electrode terminal rod 41 electrically connected to the fixed pole 23 is drawn out
from the insulating seat 24 by conductive means such as lead wiring (not shown).
The electrode terminal rod 41 is electrically connected to a gate electrode of an FET (field effect
transistor) as an impedance converter (not shown) disposed in the opening 12 of the unit case
10.
[0031]
Also in the present invention, a shield member 30 covering the front acoustic terminal 11 from
the inner surface side is provided in the unit case 10 in order to prevent foreign objects and
extraneous electromagnetic waves from entering from the front acoustic terminal 11. In the
invention, a shield plate 32 as shown in FIG. 2 is used as the shield member 30.
[0032]
The shield plate 32 is formed of a porous plate (punching metal) of an elastically deformable
metal formed in a disk shape having an outer diameter slightly smaller than the inner diameter of
the unit case 10.
[0033]
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A large number of holes 32a are formed in the shield plate 32. However, in order to shield the
electromagnetic waves emitted from the mobile phone, the diameter of the holes 32a is 0.3 mm,
and they are arranged in a zigzag at a pitch of 0.6 mm. Good to be done.
Moreover, it is preferable that a material is stainless steel (especially SUS304).
[0034]
A plurality of locking pieces 33 for fixing the shield plate 32 to the inner wall surface of the unit
case 10 are integrally and continuously provided at the peripheral edge portion of the shield
plate 32.
In practice, the shield plate 32 is punched out of a mother's punching metal by a press or the like
in a form including a plurality of locking pieces 33.
[0035]
Each locking piece 33 is preferably triangular so as to be easily fitted into the inner wall surface
of the unit case 10, and is preferably arranged at equal intervals on the peripheral edge of the
shield plate 32.
[0036]
The outer diameter of each locking piece 33 passing through each vertex 33a is larger than the
inner diameter of the unit case 10. However, as shown in FIG. 1, the insertion into the unit case
10 is easy. It is preferable that the shield plate 32 be bent at a predetermined angle from the
peripheral edge of the shield plate 32 to the opposite side to the front acoustic terminal 11.
[0037]
According to this, as the shield plate 32 is inserted (press-fit) from the opening 12 side of the
unit case 10 toward the front acoustic terminal 11 side, the plurality of locking pieces 33 are
elastically deformed to make the unit case 10 Since the shield plate 32 is in contact with the
inner surface of the front acoustic terminal 11, the unit case 10 can be reliably and electrically
connected mechanically and reliably because the shield plate 32 is inserted into the inner wall
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surface.
[0038]
Thereafter, the acoustoelectric converter 20 is housed in the unit case 10, and the lock ring 27
having an external thread is screwed into the female screw 13 provided on the inner wall of the
unit case 10 from behind and tightened. The condenser microphone unit is assembled.
[0039]
As described above, according to the condenser microphone unit of the present invention, as the
shield member 30 covering the front acoustic terminal 11 from the inside of the unit case 10, the
peripheral portion is accompanied by elastic deformation with respect to the inner wall surface
of the unit case 10. By using shield plate 32 made of a metal perforated plate integrally having a
plurality of locking pieces 33 to be inserted, shield plate 32 is securely connected electrically and
mechanically to unit case 10 Since the shield plate 32 is a metal porous plate and uniform in
shielding performance over the entire surface, high frequency current caused by extraneous
electromagnetic waves does not enter the unit case and flows to the unit case side, so noise
generated by extraneous electromagnetic waves Can be prevented.
[0040]
In addition, the locking pieces 33 are formed in a triangle and integrally connected to the
peripheral edge of the shield plate 32 at equal intervals, and the shield can be pressed against
the inner wall surface of the unit case 10 when inserted into the unit case 10. By bending the
shield plate 32 into the unit case 10 by bending the shield plate 32 at a predetermined angle
from the peripheral portion of the plate 32 to the opposite side to the front acoustic terminal 11,
the unit case 10 can be manufactured. It can be easily fixed inside.
[0041]
In the case where the unit case 10 is made of, for example, an aluminum material which is easily
plastically deformed, the acoustoelectric converter 20 can be fixed by caulking the open end
edge of the rear portion inward.
Also, although not shown, a circuit board on which an FET as an impedance converter is mounted
can be disposed in the opening at the rear end of the unit case 10.
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[0042]
Reference Signs List 10 unit case 11 front acoustic terminal 20 acoustoelectric converter 21
diaphragm 23 fixed pole 30 shield member 32 shield plate 33 locking piece
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