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JP2012094957

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DESCRIPTION JP2012094957
An object of the present invention is to provide sufficient electrostatic shielding including a
portion of a lead wire from a microphone unit to a circuit board to more effectively reduce the
generation of noise due to an external electromagnetic wave. The circuit board 30 is mounted on
the recess 11 of the base plate 10 with the component mounting surface 30b side having the
audio signal output unit 31 as the lower surface, and the shield pattern 34 is formed on the
upper surface 30a side of the circuit substrate 30 In the boundary microphone formed by
electrostatically shielding the inside of 11 and mounting the microphone unit 40 in the opening
32 of the circuit board 30 via the holder 50A, the holder 50A is fitted with the rear end side of
the microphone unit 40 A cylindrical portion 51, and a D-cut portion 52 formed by cutting a part
of the circumferential surface and the bottom surface of the bottomed cylinder integral with the
cylindrical portion 51 in parallel along the substrate surface of the circuit board 30, The lead
wire 43 of the microphone unit 40 is wired in the D-cut portion 52. [Selected figure] Figure 1
バウンダリーマイクロホン
[0001]
The present invention relates to boundary microphones, and more particularly to a technique for
reducing noise generation due to extraneous electromagnetic waves.
[0002]
The boundary microphone is a microphone having a short flat outline used by being placed on a
table, a floor surface or the like, and as shown in FIG. 4, includes a base plate 10 and a cover 20
placed thereon.
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1
[0003]
The base plate 10 has a flat bottom surface 10a, a recess 11 for mounting a circuit board on the
top surface and a support 12 for connecting a cover, and a rear wall 13 having a microphone
cable lead-in hole 13a at the rear. .
In many cases, the base plate 10 is made entirely of, for example, a die cast of aluminum.
[0004]
Although not shown in detail, for the cover 20, a metal punching plate (perforated plate) or wire
mesh material having a large number of sound wave passage holes is used.
The cover 20 is screwed to the support 12 by the male screw 21 to form an internal space on the
upper surface side of the base plate 10.
[0005]
A circuit board 30 having an audio signal output unit 31 is mounted on the recess 11 of the base
plate 10. Although not shown, the audio signal output unit 31 includes an impedance converter
such as a FET (field effect transistor), a sound quality adjustment circuit, a filter circuit, and the
like.
[0006]
The circuit board 30 has an opening 32 in a part of the circuit board 30, and the microphone
unit 40 is disposed in the opening 32 via the holder 50. In general, the microphone unit 40
employs a unidirectional condenser microphone unit having a front acoustic terminal 40 a and a
rear acoustic terminal 40 b.
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[0007]
A cord bushing 14 is provided in the microphone cable lead-in hole 13a of the back wall 13, and
the microphone cable 15 is drawn into the internal space through the cord bushing 14 and
electrically connected to the terminal portion of the circuit board 30. .
[0008]
The base plate 10 and the cover 20 are in contact at a plurality of contact points and are in direct
current conduction, but the electrostatic shielding is insufficient for a relatively strong
electromagnetic wave emitted from the mobile phone.
[0009]
Therefore, when the portable telephone is used in the vicinity of the boundary microphone, a
high frequency current due to the electromagnetic wave enters the microphone and is detected
by a semiconductor element such as an FET mounted on the circuit board 30 to generate noise. is
there.
[0010]
Therefore, as shown in FIG. 4, the inventor of the present invention sets the component mounting
surface 30b side where the audio signal output unit 31 of the circuit board 30 is disposed to the
recess 11 side as shown in FIG. It has been proposed to form a shield pattern consisting of a
copper foil solid pattern on the side opposite to the component mounting surface 30a), and to
use this shield pattern and the base plate 10 as a shield case for the recess 11.
[0011]
According to this, although the noise generation due to the external electromagnetic wave can be
reduced to a certain extent, there are still points to be solved.
[0012]
With reference to FIG. 4, the microphone unit 40 is fitted and held in a holder 50, which is a
cylindrical cylinder with a metal at the rear end, and is disposed in the opening 32 of the circuit
board via the holder 50. In the above, the lead wires 42 and 42 connected to the terminal
substrate 41 of the microphone unit 40 are drawn out from the small holes 51 on the bottom
surface of the holder 50 and soldered to predetermined lands of the circuit substrate 30.
[0013]
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In this case, the electrostatic shielding of the lead wire portion drawn out from the inside of the
holder 50 of the lead wires 42 and 42 to the circuit board 30 is insufficient, and when an
electromagnetic wave is applied to the lead wire portion, The high frequency current may enter
and still generate noise.
[0014]
Further, since it is difficult to keep the shapes uniform because the lead wires 42 and 42 use the
coated lead wires, the frequency of the noise-generating electromagnetic wave and the
magnitude of the noise are not uniform, There is also the problem of.
[0015]
Patent No. 4471818
[0016]
Therefore, the object of the present invention is to improve the boundary microphone described
in Patent Document 1 and to provide sufficient electrostatic shielding, including the portion of
the lead wire from the microphone unit to the circuit board, to the external electromagnetic
wave. The purpose is to more effectively reduce the generation of the noise caused.
[0017]
In order to solve the above problems, the present invention has a flat base plate made of a metal
material having a flat bottom surface and a concave portion for mounting a substrate on the top
surface side, and a large number of sound wave passing holes. A cover which is placed on the
upper surface side, a circuit board which is mounted on the base plate to cover the recess and
which has an opening for mounting a microphone unit in a part, and a microphone which is
mounted in the opening via a metal holder An audio signal output unit is provided on the lower
surface side of the circuit board facing the recess, including a unit, and a shield pattern for
electrostatically shielding the inside of the recess along with the base plate is formed on the
upper surface side of the circuit substrate. And the output terminal of the microphone unit is
electrically connected to the audio signal output unit through a lead wire. In the UNDERY
microphone, the holder has a cylindrical portion to which the rear end portion side of the
microphone unit is fitted, and a part of a peripheral surface and a bottom surface of a bottomed
cylinder integrated with the cylindrical portion on the substrate surface of the circuit board And
a D-cut portion which is cut in parallel along the length, and the lead wire is wired in the D-cut
portion.
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[0018]
According to a preferred aspect of the present invention, the D-cut portion is soldered to the
ground pattern.
[0019]
Preferably, a solder plated wire having no coating on the lead wire is used, and the lead wire is
drawn to the lower surface side of the circuit board through a through hole and soldered to the
audio signal output portion.
[0020]
According to the present invention, as a metal holder for mounting the microphone unit in the
opening formed in the circuit board, the cylindrical portion into which the rear end portion side
of the microphone unit is fitted and the integral with the cylindrical portion A lead wire from the
microphone unit to the circuit board in the D cut portion using a holder including a D cut portion
formed by cutting a part of the circumferential surface and the bottom surface of the bottom
cylinder in parallel along the substrate surface of the circuit board By wiring the wires, portions
of the lead wires are also sufficiently shielded electrostatically, and the generation of noise due to
external electromagnetic waves can be more effectively reduced.
[0021]
Also, by making the lead wire a solder-plated wire without a coating, the wiring shape can be
easily made uniform, and even if noise is generated, the frequency to be disturbed can be made
constant, so it is designed It becomes easy to handle.
[0022]
Sectional drawing which shows the internal structure of the boundary microphone concerning
one Embodiment of this invention.
The perspective view which shows the relative relationship of the holder which is the principal
part of this invention, and the opening part of a circuit board.
The side view which shows the state which attached the said holder to the circuit board.
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Sectional drawing which shows the internal structure of the boundary microphone as a prior art
example.
[0023]
Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 3,
but the present invention is not limited to this.
In the description of this embodiment, the same reference numerals as in the conventional
example described above with reference to FIG.
[0024]
As shown in FIG. 1, the boundary microphone according to this embodiment includes a base
plate 10 and a cover 20 to be put on it, as in the prior art described above.
[0025]
The base plate 10 has a flat bottom surface 10a so as to be stably placed on a table surface or a
floor surface, and has a recess 11 for mounting a circuit board and a support 12 for connecting a
cover on the top surface side The rear wall 13 is provided with a microphone cable lead-in hole
13a.
The base plate 10 may be made entirely of, for example, a die cast of aluminum.
[0026]
For the cover 20, a metal punching plate (perforated plate) or wire mesh material having a large
number of sound wave passage holes may be used.
The cover 20 is screwed to the support 12 by the male screw 21 to form an internal space on the
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upper surface side of the base plate 10.
[0027]
A circuit board 30 having an audio signal output unit 31 is mounted on the recess 11 of the base
plate 10.
Although not shown, the audio signal output unit 31 includes an impedance converter such as a
FET (field effect transistor), a sound quality adjustment circuit, a filter circuit, and the like.
[0028]
The circuit board 30 has an opening 32 in a portion thereof, and the microphone unit 40 is
mounted in the opening 32 via the holder 50A.
In this embodiment, the microphone unit 40 employs a unidirectional directivity condenser
microphone unit having a front acoustic terminal 40a and a rear acoustic terminal 40b.
[0029]
A cord bushing 14 is provided in the microphone cable lead-in hole 13a of the back wall 13, and
the microphone cable 15 is drawn into the internal space through the cord bushing 14 and
electrically connected to a terminal portion (not shown) of the circuit board 30. Be done.
A two-core shield coated wire is used for the microphone cable 15.
[0030]
The base plate 10 and the cover 20 are in contact at a plurality of contact points and are in direct
current conduction, but the electrostatic shielding is insufficient for a relatively strong
electromagnetic wave emitted from the mobile phone.
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[0031]
Therefore, in the present invention, according to the invention described in Patent Document 1,
the component mounting surface 30b side on which the audio signal output unit 31 of the circuit
board 30 is provided is disposed toward the inside of the recess 11 with the lower surface As
shown in FIG. 2, a shield pattern 34 formed of a solid pattern of copper foil is formed on the
upper surface (non-component mounting surface) 30a side of the substrate 30, and the shield
pattern 34 and the base plate 10 shield the recess 11 Make up the case.
[0032]
Although not shown, the shield pattern 34 is electrically connected to the shield coated wire and
/ or the base plate 10 of the microphone cable 15 alone or together with the ground pattern on
the component mounting surface 30 b side.
[0033]
With reference to FIG. 2 and FIG. 3 together, in the present invention, in order to also
electrostatically shield a pair of lead wires 43 and 43 wired between the terminal substrate 41 of
the microphone unit 40 and the circuit substrate 30, The holder 50A configured as in FIG.
[0034]
That is, the holder 50A is entirely made of a metal material, and the cylindrical portion 51 with
which the rear end portion side of the microphone unit 40 is fitted, and a part of the
circumferential surface and the bottom of the bottomed cylinder integrated with the cylindrical
portion 51 And a D-cut portion 52 cut in parallel along the substrate surface of the substrate 30.
[0035]
Such a holder 50A prepares a metal bottomed cylindrical body as an example, leaving the
cylindrical portion on the opening side as it is to form a cylindrical portion 51, and milling a part
from the circumferential surface to the bottom surface on the bottom side It can obtain easily by
cutting in parallel along the substrate surface of circuit board 30 by processing etc., and setting it
as D cut part 52.
[0036]
As shown in FIG. 2, the cylindrical portion 51 is mounted in the opening 32 of the circuit board
30 together with the microphone unit 40 in a state where the microphone unit 40 is fitted and
held, but the D cut portion 52 is The axial cutting surface (cut surface) 52 a contacts the
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peripheral portion of the opening 32 of the circuit board 30 with almost no gap.
[0037]
Therefore, the inside of the D-cut portion 52 is a space isolated from the upper surface 30 a side
of the circuit board 30, and by wiring the lead wires 43, 43 in the D-cut portion 52, sufficient for
the lead wires 43, 43 Electrostatic shielding is provided.
[0038]
In order to make the electrostatic shielding with respect to the lead wires 43, 43 more effective,
it is preferable to solder the cutting surface 52a of the D-cut portion 52 to the shield pattern 34
formed on the circuit board 30.
[0039]
Further, through holes 33, 33 are formed in the portion of the circuit board 30 covered by the D
cut portion 52, and the lead wires 43, 43 are inserted into the through holes 33, 33, and their
respective end portions are the circuit board It is good to solder on the predetermined |
prescribed pattern of the audio | voice signal output part 31 in the lower surface side of 30. FIG.
[0040]
Further, it is preferable to use a solder plated wire without coating on the lead wires 43, 43, in
particular, a tin plated wire.
According to the tin-plated wire, since the wiring shape can be easily made uniform, even if noise
is generated, the frequency to be disturbed can be made constant. For example, application of
ferrite beads according to the frequency, etc. It becomes easy to deal with the design.
[0041]
In order to further enhance the electrostatic shielding of the internal space, a conductive material
such as a conductive cloth or a conductive gasket may be interposed between the contact
surfaces of the cover 20 and the base plate 10.
[0042]
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DESCRIPTION OF SYMBOLS 10 base plate 11 recessed part 12 post | mailbox 13 back wall 15
microphone cable 20 cover 30 circuit board 31 audio signal output part 32 opening part 33
through hole 34 shield pattern 40 microphone unit 41 terminal board 43 lead wire 50A holder
51 cylindrical part 52 D cut part
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