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DESCRIPTION JP2016076828

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DESCRIPTION JP2016076828
Abstract: [Problem] To provide a condenser microphone unit in which transmission of an audio
signal and shielding action of an external electromagnetic wave can function independently while
maintaining a compact form. A unit component 1 is configured by integrally molding a fixed pole
17 disposed opposite to the back surface of a diaphragm 14 and a fixed pole support member 18
supporting the fixed pole from a resin material. doing. The conductive films 2A and 2B are
electrically separated from each other at a portion corresponding to the fixed electrode 17 and a
portion corresponding to the fixed electrode support member 18, respectively. The circuit board
19 is mounted on the back surface of the diaphragm assembly 13 having this configuration, and
the diaphragm assembly 13 is accommodated in the metal unit case 12. The electrical conduction
circuit from the diaphragm 14 through the conductive film 2B is a signal transmission path from
the diaphragm side, and the unit case 12 is divided into functions as a shield member for
shielding extraneous electromagnetic waves. [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 provided with a shielding function
against high frequency extraneous electromagnetic waves.
[0002]
There are also cases where the condenser microphone unit (hereinafter, simply referred to as a
"microphone unit").
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) Is provided in a state in which the diaphragm assembly is housed in a metal unit case. This
diaphragm assembly is generally formed in a state in which the diaphragm and the fixed
electrode face each other via a ring-shaped spacer.
[0003]
Further, in the electret condenser microphone unit having the electret dielectric film on the
diaphragm or the fixed pole, a circuit board (PCB) mounting an FET (field effect transistor) on the
rear end side of the unit case is mounted There is. The FET functions as an impedance conversion
element. The electret condenser microphone unit fixes the diaphragm assembly in the unit case
by caulking the rear end portion of the unit case inward. A part of the unit case is connected to
the reference potential point (earth line) of the circuit board by the caulking.
[0004]
FIG. 3 is a cross-sectional view showing a basic configuration of a conventional condenser
microphone unit 11. As shown in FIG. The condenser microphone unit 11 includes a unit case 12
made of, for example, an aluminum material, and the diaphragm assembly 13 is accommodated
in the unit case 12. The unit case 12 has an opening 12a on the front side facing the sound
source, and the rear side of the unit case 12 opens in a cylindrical shape. The diaphragm 14
constituting the diaphragm assembly 13 is attached to the conductive diaphragm support ring
15 with a predetermined tension, and is disposed immediately after the opening 12 a in the unit
case 12. Then, an insulating spacer 16 formed in a ring shape is disposed on the back side of the
diaphragm 14, and a fixed electrode 17 made of metal is disposed to face the diaphragm 14 via
the spacer 16. ing.
[0005]
The microphone unit 11 is configured such that an electret dielectric film (not shown) subjected
to polarization processing is attached to either the diaphragm 14 or the fixed electrode 17 to
constitute an electret condenser microphone unit. . Further, the fixed electrode 17 is supported
by a fixed electrode support member 18 formed of an insulating material. An annular recess 18 a
for mounting a disk-shaped circuit board (PCB) 19 is formed on the back surface side of the fixed
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electrode support member 18.
[0006]
On the circuit board 19, an FET (field effect transistor) 20 functioning as an impedance
conversion element is mounted. The gate terminal of the FET 20 is connected to the fixed pole
17, and the other terminal of the FET 20 is connected to the circuit board 19 by soldering or the
like to form, for example, a source follower circuit. Then, as shown in FIG. 3, the rear opening
edge 12 b of the unit case 12 is crimped inward, so that a diaphragm assembly including the
diaphragm 14, the support ring 15, the spacer 16, the fixed pole 17, and the fixed pole support
member 18. The solid 13 is held by the unit case 12. At the same time, the crimped tip end
portion (rear opening edge 12 b) of the unit case 12 is connected to a reference potential point
(earth line) formed on the circuit board 19.
[0007]
According to the conventional example shown in FIG. 3, the first electrical conduction path
(signal path from the diaphragm side) and the second electrical conduction path (signal
transmission path from the fixed pole side) are formed in the microphone unit 11. The first
electric conduction path forms a path from the conductive film (not shown) formed on the
diaphragm 14 to the ground line of the circuit board 19 through the diaphragm support ring 15
and the unit case 12, and the second electric conduction path The path constitutes a path from
the fixed pole 17 through the FET 20 to the circuit board 19.
[0008]
Among the above, there is a problem that noise is superimposed on the audio signal since the
audio signal from the diaphragm side and the high frequency signal by receiving the external
electromagnetic wave simultaneously flow in the unit case 12 constituting the first electric
conduction path. It will occur. Particularly in recent years, there have been many opportunities
for portable terminals and the like to approach the microphone unit 11, and the frequency of
receiving interference from the portable terminals and the like is also increasing.
[0009]
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Therefore, in order to solve the problem of interference caused by the external electromagnetic
wave described above, an electric conduction path (the first electric conduction path) for
transmitting an audio signal from the diaphragm side, and a shielding path which performs a
shielding function against the external electromagnetic wave It is desirable to separate the socalled double shield function.
[0010]
FIG. 4 is a cross-sectional view showing an example of the microphone unit 11 having a double
shield function.
That is, in the example shown in FIG. 4, a metal shield case (outer case) 22 is covered on the
outside of the unit case 12 constituting the microphone unit 11 shown in FIG. 3 described above.
The microphone unit (inside the outer case 22) formed in the unit case 12 is the same as the
microphone unit 11 described above with reference to FIG. Therefore, in FIG. 4, the same
symbols are attached to the main members, and the detailed description thereof is omitted.
[0011]
The shield case 22 of the microphone unit 11 shown in FIG. 4 is configured to be slightly larger
than the inner unit case 12. Similar to the inner unit case 12, an opening 22 a is formed on the
front surface of the shield case 22. Then, the rear opening edge 22 b of the cylindrical outer
shield case 22 is crimped inward, and its tip is connected to a reference potential point (earth
line) formed on the circuit board 19. An electrically insulating spacer 23 is disposed between the
outer shield case 22 and the inner unit case 12.
[0012]
According to the microphone unit 11 shown in FIG. 4, the inner unit case 12 constitutes an
electrical conduction path (the first electric conduction path described above) which becomes a
signal path from the microphone unit, and the outer shield case 22 is exclusively used. It
functions as a shield layer that shields external electromagnetic waves. Therefore, according to
the microphone unit 11 configured as shown in FIG. 4, the external electromagnetic wave can be
prevented from being added to the inner unit case 12, so that the influence of the
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electromagnetic wave on the audio signal can be further reduced.
[0013]
As shown in FIG. 3 described above, the diaphragm assembly 13 is fixed in the unit case 12 by
caulking the rear end portion of the unit case 12 inward, and a part of the unit case is a circuit
board. Patent Document 1 discloses a microphone unit configured to be connected to a reference
potential point (earth line). In addition, as shown in FIG. 4, a microphone unit having a unit case
12 for transmitting an inner audio signal and a shield case 22 having a function of shielding an
external electromagnetic wave exclusively for the outer side is disclosed as a patent. It is
disclosed in reference 2.
[0014]
JP, 2006-74149, A JP, 2008-131191, A
[0015]
By the way, according to the microphone unit 11 having the configuration shown in FIG. 4, the
electrical conduction path (unit case 12) serving as the signal path of the audio signal as
described above and the shield case 22 for shielding extraneous electromagnetic waves are
provided double.
Therefore, the problem that the whole microphone unit 11 enlarges arises. Further, since the unit
case 12 and the outer shield case 22 are both connected to the ground line of the circuit board
19 by caulking, the number of assembling steps is increased, and there is a problem that the
manufacturing cost is increased. Furthermore, the inner unit case 12 and the outer shield case
22 will be double crimped. Therefore, the structure of the microphone unit 11 tends to be
unstable, and the connection of the caulking portions of the respective cases 12 and 22 to the
ground line of the circuit board 19 becomes insufficient.
[0016]
The present invention has been made focusing on the above-mentioned problems of the
conventional microphone unit, and, for example, a voice generated by the microphone unit while
maintaining a compact form like the microphone unit shown in FIG. An object of the present
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invention is to provide a condenser microphone unit which can function independently of signal
transmission and shielding function of an external electromagnetic wave and can effectively
prevent noise from being superimposed on an audio signal. .
[0017]
A condenser microphone unit according to the present invention, which has been made to solve
the above problems, includes a diaphragm, a fixed pole disposed facing the back of the
diaphragm, and a fixed pole supporting member for supporting the fixed pole. The condenser
microphone unit is housed in a unit case, and each of the fixed pole and the fixed pole support
member is made of an insulating material on which a conductive film is formed, and the
diaphragm and the fixed pole support member A conductive spacer is disposed in between, and
the conductive film formed on the outer periphery of the diaphragm and the fixed electrode
supporting member via the spacer is used as a first electric conduction path.
[0018]
In this case, the unit case is preferably an electromagnetic shield member made of metal.
In a preferred embodiment, the fixed electrode and the fixed electrode support member are
integrally formed of a resin on which a conductive film is formed to form a unit component.
In addition, a configuration in which the spacer is integrally formed with the unit component may
be suitably employed.
[0019]
Then, a circuit board having an impedance conversion element mounted thereon is disposed on
the back surface of the fixed electrode support member, and the first electric conduction path is
connected to a reference potential point of the circuit board as a signal path from the diaphragm
side. At the same time, the unit case is connected to the reference potential point of the circuit
board by caulking the rear end of the unit case.
[0020]
Furthermore, the controlled electrode terminal of the impedance conversion element is
connected to the conductive film formed on the fixed electrode separated from the signal path
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from the diaphragm side, and the impedance is measured from the conductive film formed on the
fixed electrode. The second electrical conduction path passing through the conversion element is
formed as a signal transmission path from the fixed pole side.
[0021]
According to the above-described condenser microphone unit according to the present invention,
the signal path from the diaphragm side can be configured independently from the diaphragm
via the conductive spacer formed on the conductive spacer and the fixed electrode support
member, The outer unit case functions as a shield member that shields external electromagnetic
waves.
Therefore, the signal transmission path for transmitting the audio signal generated by the
microphone unit, the signal path for connecting the diaphragm and the reference potential point
of the circuit board, and the shield of the external electromagnetic wave can be functioned
independently, respectively. It is possible to provide a condenser microphone unit that can
effectively prevent noise from being superimposed on the.
[0022]
In addition, the conductive film formed on the fixed electrode support member can be formed by
applying a so-called plastic plating to the resin material.
Therefore, the thickness of the conductive film formed on the fixed pole support member
functioning as a signal transmission path of the audio signal is small, which can contribute to the
downsizing of the entire condenser microphone unit.
[0023]
It is sectional drawing which showed the assembly process of the capacitor | condenser
microphone unit which concerns on this invention. It is sectional drawing which showed a part of
assembly process of the other form of the capacitor | condenser microphone unit based on this
invention. It is sectional drawing which showed the basic composition of the conventional
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condenser microphone unit. It is sectional drawing which showed an example of the conventional
double shield type condenser microphone unit.
[0024]
FIG. 1 shows the assembling process of the condenser microphone unit according to the present
invention in order. FIG. 1E is a cross-sectional view of the completed state of the condenser
microphone unit according to the present invention. Therefore, the configuration of each part of
the condenser microphone unit will be sequentially described based on the description of the
assembly process shown in FIG. In the assembly process drawings shown below, only necessary
reference numerals corresponding to the description of each process are given. In the other
drawings, the reference numerals of the corresponding parts may be omitted due to the space of
the paper.
[0025]
The code | symbol 1 shown to FIG. 1 (A) has shown the unit components in which the whole was
shape | molded annularly by the resin raw material. The unit component 1 corresponds to the
fixed electrode 17 and the fixed electrode support member 18 in the basic configuration shown
in FIG. 3, and these are integrally molded of a resin material. Therefore, FIG. 1A shows the fixed
pole 17 and the fixed pole support member 18 in a state of being divided by a dashed line as a
virtual line for convenience of explanation. A plurality of through holes 17a are formed in a
portion corresponding to the fixed pole 17 in the unit component 1 in the thickness direction.
This is to make the back side of the diaphragm 14 to be described later communicate with the air
chamber formed on the back of the fixed electrode 17.
[0026]
A conductive film 2 is formed on the unit component 1 described above so as to cover the entire
unit component 1 as indicated by a thick line in FIG. 1 (B). The conductive film 2 is formed by
performing so-called plastic plating on the entire unit component 1 formed of a resin material.
[0027]
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Then, in the unit component 1 in which the conductive film 2 is formed on the entire surface, cut
portions of the conductive film 2 are formed on the front and back sides of the unit component 1
as indicated by reference numerals 3 and 4 in FIG. Be done. The cutouts 3 and 4 are formed in
such a state that grooves are cut in a ring shape along the outer shape of the unit component 1.
Thus, the conductive film 2 formed on the unit component 1 is mainly formed on the peripheral
side of the fixed electrode support member 18 described above and the conductive film 2A
formed mainly on the fixed electrode 17 side. It is electrically separated from the conductive film
2B.
[0028]
As shown in FIG. 1D, a spacer 16 is attached to the outer peripheral edge on the front side of the
unit component 1 described above. For the spacer 16 used in this embodiment, a metal foil, a
resin film with a metal foil attached to the surface, for example, or a conductive film treated by
metal deposition or the like is used. The spacer 16 is disposed so as to be conductive to the
conductive film 2 B formed on the peripheral side surface of the unit component 1.
[0029]
Further, as shown in FIG. 1D, the diaphragm 14 attached to the diaphragm support ring 15 with
a predetermined tension is placed on the front side of the unit component 1, and the outer
peripheral edge of the diaphragm 14 is It is attached in contact with the spacer 16. In this
embodiment, a resin film is used as the diaphragm 14. The surface of the diaphragm 14 facing
the unit component 1 is subjected to a conductive treatment such as metal deposition.
[0030]
Therefore, the metal surface of the diaphragm 14 on which the conductive processing has been
performed is conducted to the conductive film 2B formed on the peripheral side surface of the
unit component 1 through the spacer 16. Further, in this embodiment, the electret dielectric film
is provided on the opposite surface of the diaphragm 14, that is, on the front surface side of the
diaphragm 14, to form a condenser microphone unit of a film electret system. Ru.
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[0031]
An annular recess 18 a is formed on the back surface of the unit component 1, and a disk-shaped
circuit board (PCB) 19 is attached to the recess 18 a. The circuit board 19 is mounted with an
FET 20 that functions as an impedance conversion element. The controlled electrode terminal
(gate terminal) of the FET 20 is connected to the conductive film 2A on the fixed electrode 17
side of the unit component 1 and the other terminal of the FET 20 is connected to the circuit
board 19 by soldering or the like. Be done. The FETs 20 constitute a source follower circuit by
being connected in this manner. As a result, a second electric conduction path (a signal
transmission path from the fixed electrode side) extending from the fixed electrode conductive
film 2A to the circuit board 19 via the FET 20 is formed.
[0032]
Further, a reference potential point (earth line) of the circuit is formed on the outer peripheral
edge of the back surface of the circuit board 19. Therefore, as shown in FIG. 1D, by mounting the
circuit board 19 on the back surface of the unit component 1, the conductive film 2B formed on
the peripheral side of the unit component 1 is grounded. Can be connected to the line. In this
case, by adding a conductive paste or the like between the outer peripheral edge of the circuit
board 19 and the unit component 1 as necessary, the electrical connection can be sufficiently
secured. As a result, a first electric conduction path (from the diaphragm side) extending from
the conductive film (not shown) of the diaphragm 14 described above to the ground line of the
circuit board 19 through the spacer 16 and the conductive film 2B on the fixed electrode support
member side. A signal path is formed. The diaphragm 14, the fixed pole 17, and the circuit board
17 are connected by the first electrical conduction path and the second electrical conduction
path, and a circuit that outputs an audio signal is configured.
[0033]
The diaphragm assembly 13 and the circuit board 19 shown in FIG. 1 (D) are accommodated in
the unit case 12 as shown in FIG. 1 (E). The diaphragm assembly 13 is held by the unit case 12
as the rear opening edge 12 b of the unit case 12 is crimped inward. At the same time, the
crimped tip end portion (rear opening edge 12 b) of the unit case 12 is connected to a reference
potential point (earth line) formed on the circuit board 19.
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[0034]
The microphone unit 11 shown in FIG. 1E is set to be nondirectional by closing the back surface
of the unit component 1 with the circuit board 19. However, the circuit board 19 is provided
with an appropriate through hole, and the sound passage communicating with the back surface
of the diaphragm 14 is formed, whereby the microphone unit 11 of bi- or uni-directionality can
be configured.
[0035]
According to the condenser microphone unit 11 shown in FIG. 1 (E), particularly, the conductive
film 2B formed on the peripheral side wall of the unit component 1 is used to connect the first to
the ground line of the circuit board 19 from the diaphragm 14 side. Electrical conduction paths
are formed. Also, the unit case 12 on the outer side functions as a shield member that shields
external electromagnetic waves. Therefore, according to this embodiment, it is possible to
provide a condenser microphone unit capable of effectively preventing noise from being
superimposed on an audio signal.
[0036]
In addition, the conductive film 2B can be formed by plating the unit component 1 made of a
resin material. Therefore, according to this embodiment, it is possible to obtain the operation
effect as described in the column of the effect of the invention described above, such as
downsizing of the entire condenser microphone unit.
[0037]
FIG. 2 shows another embodiment of the condenser microphone unit according to the present
invention, and FIGS. 2 (A) to 2 (D) show the assembling steps shown in FIGS. 1 (A) to (D)
described above. The same steps are shown. In the microphone unit shown in FIG. 2, as shown in
FIG. 2A, the fixed pole 17 and the fixed pole support member 18 are integrally molded of a resin
material to constitute a unit component 1. Further, a spacer 16 is integrally formed in a ring
shape around the front side of the unit component 1.
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[0038]
Then, in a state where the spacer 16 is integrally formed on the unit component 1, the
conductive film 2 is formed on the whole as shown in FIG. 2 (B). Subsequently, as shown in FIG.
2C, the cut portions 3 and 4 are formed in the conductive film 2. The conductive film 2 formed
on the unit component 1 is formed on the peripheral side of the fixed electrode support member
18 mainly by the conductive film 2A mainly formed on the fixed electrode 17 side by the
cutaway portions 3 and 4 It is electrically separated from the conductive film 2B. At this time, the
conductive film 2 formed on the spacer 16 is connected to the conductive film 2B on the fixed
electrode supporting member 18 side.
[0039]
Therefore, as shown in FIG. 2 (D), the diaphragm 14 on which the conductive processing is
applied is mounted by mounting the outer peripheral edge of the diaphragm 14 attached to the
diaphragm support ring 15 on the spacer 16. Metal surface is conducted to the conductive film 2
B via the conductive film on the spacer 16.
[0040]
In this state, although not shown in FIG. 2, the diaphragm assembly 13 and the circuit board 19
are accommodated in the unit case 12, and the rear opening edge 12b of the unit case 12 is
crimped inward, thereby making the condenser microphone unit It can be configured.
According to the microphone unit shown in FIG. 2, it is possible to further reduce the number of
parts, and to provide a condenser microphone unit having the same effects as the example shown
in FIG. 1.
[0041]
DESCRIPTION OF SYMBOLS 1 unit component 2 conductive film 2A fixed electrode side
conductive film 2B fixed electrode support member side conductive film 3, 4 cutout of
conductive film 11 capacitor microphone unit 12 unit case 12a opening 12b rear opening edge
(crimping portion) 13 diaphragm assembly Solid 14 diaphragm 15 diaphragm support ring 16
spacer 17 fixed pole 18 fixed pole support member 18a annular recess 19 circuit board 20 FET
(impedance conversion element)
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