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JP2011239086

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DESCRIPTION JP2011239086
The present invention provides a compact and low noise microphone device having a simple
configuration. A microphone element (101) and a case for holding and fixing the microphone
element (101). The case (102) is made of a conductive material and directly contacts an outer
metal part of the microphone element (101). It has a structure in contact with or connected to
the GND pattern of the circuit board 104 such as a preamplifier for amplifying a signal from the
element. [Selected figure] Figure 1
Microphone device
[0001]
The present invention relates to a microphone device, and more particularly, to an assembly
composed of a microphone element housed in a holding / fixed case made of rubber or rubber
and a resin material and an amplifier circuit board, and this case and amplifier The present
invention relates to a microphone device having a structure in contact with a GND pattern of a
circuit board.
[0002]
In the conventional microphone device, as a countermeasure against the ingress of external noise
from the surroundings, a metal shield component is added between or on the components, and
the shield component itself is connected to the GND pattern of the amplifier circuit board with a
wire or the like. By connecting it, shielding measures are taken by escaping the intruding external
noise to GND.
01-05-2019
1
[0003]
Also, as shown in Patent Document 1, measures are taken by connecting the microphone element
and the shield coated wire to the shield case and connecting the shield coated wire to the GND
circuit of the circuit board via the high frequency choke coil. It was
FIG. 6 shows a cross-sectional view of a mounting structure of a conventional microphone.
Conventionally, a metallic shield case 507 is added between the nonconductive rubber case 502
and the outer case 103a, and the shield case 507 is connected to the GND terminal of the
substrate by a wire (not shown) or the like. I was getting a shield effect. As described above, since
the rubber case 502 having no conductivity is used, there is a problem that a separate shield case
and a wire for connection are required.
[0004]
As described above, measures against external noise in the conventional microphone device are
coped with by adding a shield case 507 or a shield part, and since the shield case 507 is added,
the cost of parts and the number of assembling steps increase, etc. Had problems. In addition,
since it is necessary to arrange the shield case 507 so as to cover the microphone element 101
and parts such as the holding / fixing case, there is also a problem that the entire apparatus
becomes large.
[0005]
Furthermore, in order to secure the effect of the shield, it is necessary to connect the shield case
507 itself to the GND pattern of the circuit board, and since connection is performed, wire parts
such as connecting wire (not shown) increase. There were also problems such as an increase in
the number of steps for connecting wires.
[0006]
Also, as another method, it is possible to use a component having conductivity by applying a
conductive paint on the surface of a holding / fixing case of rubber or resin or metal plating. And
coating and plating, etc., and there are problems such as an increase in the number of steps.
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[0007]
JP 2005-333183 A
[0008]
The present invention has been made in view of the above-described circumstances, and an
object thereof is to provide a small-sized, low-noise microphone device having a simple
configuration.
[0009]
The microphone device of the present invention comprises a microphone element and a case for
holding and fixing the microphone element, and the case is made of a conductive material and is
in direct contact with the outer metal portion of the microphone element, and the microphone
element Contact or connect to the GND pattern of the preamplifier circuit board that amplifies
the signal from the
[0010]
In the microphone device according to the present invention, the case is formed of an elastic
body having conductivity.
[0011]
In the microphone device according to the present invention, the case is made of a plurality of
materials such as a conductive rubber material or a conductive resin material.
[0012]
According to the present invention, in the microphone device, the volume resistivity of the
conductive material used for the case is 15 MΩ · cm or less.
[0013]
Needless to say, the above features can be combined as appropriate so as not to cause
contradiction.
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In addition, in each feature, even when a plurality of effects can be expected, not all effects must
be exhibited.
[0014]
According to the present invention, the case component for holding and fixing the microphone
element is a component having conductivity by mixing carbon fiber or the like into rubber
material or resin material itself and forming the component as a conductive component. I can
have a role.
Then, the case component is brought into close contact with the GND pattern of the amplifier
circuit board to secure the GND connection, and external noise is dissipated to the GND potential,
thereby providing a shielding effect.
Therefore, it is possible to obtain a small-sized and low-noise microphone device having a simple
configuration.
In addition, the holding / fixing case component can be obtained by obtaining conductivity even
if the component is made of a plurality of materials such as a conductive rubber material or a
conductive resin material and a rubber material. It has a shield effect.
Further, by setting the volume resistivity of the conductive material used for the holding and
fixing case to 15 MΩ · cm or less, a reliable shielding effect is obtained.
[0015]
FIG. 6 is a cross-sectional view of the microphone device according to the first embodiment of the
present invention, an enlarged perspective view of the microphone element, an assembly view of
a conductive rubber case and the microphone element in the microphone device, showing the
microphone device of the second embodiment of the present invention, Assembly drawing in the
case where the conductive part is composed of two parts in the same microphone device
Comparison of noise levels of the microphone device in the same microphone device A crosssectional view of a conventional shielded microphone device in the same microphone device
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[0016]
Embodiment 1 Hereinafter, Embodiment 1 of the present invention will be described in detail
with reference to FIGS. 1 to 4.
Further, the materials and numerical values used in the present invention only exemplify
preferable examples, and the present invention is not limited to this form.
Moreover, changes can be made as appropriate without departing from the scope of the concept
of the present invention.
Furthermore, combinations with other embodiments are also possible.
Here, the microphone element is a coin-type microphone element.
[0017]
The microphone device according to the first embodiment of the present invention will be
described below. FIG. 1 is a cross-sectional view showing the basic concept of the microphone
device of the present invention. In this microphone device, the microphone element 101 is
inserted into the conductive rubber case 102 and in close contact with the microphone element
101, and is inserted into the resin case as the exterior case 103a. The conductive rubber case
102 is disposed in such a manner that the circuit board 104 constituting the preamplifier
substrate is in contact in the case 103a, and the conductive rubber case 102 is closely attached
to the circuit board 104 by the resin outer cover 103b. A GND pattern is provided on the circuit
board 104 in a portion where the conductive rubber case 102 contacts, and the contact is
secured with the GND pattern, and the conductive rubber case 102 is at the same level as the
GND potential. In addition, the cable 105 electrically connects the microphone element 101 and
the circuit board 104, and the connector cable 106 connected to the circuit board 104 outputs
an audio output to an external device. 108 is a non-woven fabric for preventing dust.
[0018]
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As the conductive rubber, one obtained by adding carbon to ethylene propylene rubber is used.
Here, the conductivity can be improved by increasing the amount of carbon, but if the amount of
carbon is too large, the properties of the rubber are degraded, so it is necessary to select the
optimum amount. Ethylene-propylene rubber is of two types: EPM (EPR), which is a copolymer of
ethylene and propylene, and EPDM (EPT), a terpolymer, which further contains a small amount of
a third component. Generally, EPM is used in industrial rubber products due to peroxide crosslinking agents etc. However, at present, a large amount of it is used for resin blend as an impact
modifier by adding it to general purpose resin such as polypropylene. Used for On the other
hand, since the specific gravity is small, it is effective for weight reduction.
[0019]
Further, since the conductive rubber case 102 has elasticity, the conductive rubber case 102
elastically contacts the circuit board 104 to fix and fix the circuit board 104, and GND on the
circuit board 104 in the contacting portion is provided. Achieve good electrical connection with
the pattern.
[0020]
Further, by setting the volume resistivity of the conductive material used for the conductive
rubber case 102 as the holding and fixing case to 15 MΩ · cm or less, the shielding effect can be
secured.
In the microphone device, it has been found that the hearing sensitivity is significantly improved
when the noise level is less than 50 decibels. Fifty decibels is a level that is not recognized as an
output. Therefore, when the volume resistivity is set to 15 MΩ · cm or less, preferably 1 MΩ ·
cm or less in order to release the electrostatic noise, the electrostatic noise efficiently flows out.
[0021]
Here, as the rubber case having conductivity, EPDM added with carbon is used, but rubber may
be impregnated with a liquid containing conductive particles such as carbon. Also, it may be a
sponge impregnated with conductive particles.
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[0022]
FIG. 2 is an enlarged view of the microphone element 101 used here. A metal case 101a on the
outside of the microphone element is connected to the GND potential of the substrate via a
conductive rubber case 102 (see FIG. 1). Reference numeral 101 b denotes a terminal board for
taking out the signal of the microphone element, which is connected to the cable 105.
[0023]
FIG. 3 shows an assembly of the conductive rubber case 102 and the microphone element 101 of
the present invention. The microphone element 101 is configured to be inserted into a recess
102 c formed in the conductive rubber case 102.
[0024]
In the case of the conventional microphone described above, since a non-conductive rubber case
502 is used, a metallic shield case 507 is added, and this shield case is connected to the GND
terminal with a wire (not shown), I needed to get a shield effect. On the other hand, by using the
conductive rubber case which is the conductive part of the present invention, the shield part such
as the shield case and the wire to be connected to the GND of the substrate become unnecessary,
and downsizing becomes possible. And can reduce the number of assembling steps.
[0025]
The conductive rubber case 102 may be made of a component obtained by combining a plurality
of conductive resin materials and a plurality of conductive rubber materials.
[0026]
As described above, in the microphone device of the present invention, conductivity is ensured
by mixing and molding carbon fiber or the like in the rubber material or resin material of the
case component for holding and fixing the microphone element without using the shield
component. I have a configuration.
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With this configuration, it is possible to have the role of a shield component, and by keeping this
case component in close contact with the GND pattern of the amplifier circuit board to secure the
GND connection, noise and the like are released to GND with a very simple configuration. Can do.
[0027]
Second Embodiment The second embodiment of the present invention will be described below.
FIG. 4 shows an assembly portion in which the portion holding the microphone element is
composed of two conductive parts according to the second embodiment of the present invention.
A conductive resin having a recess that matches the outer shape of the microphone element 101.
The microphone element 101 is held in a conductive case 402 made of rubber having
conductivity via the conductive holder 401. Thus, even if it comprises two parts which have
conductivity, the performance similar to one part is securable. The other parts are the same as in
the first embodiment, and thus the description thereof is omitted here.
[0028]
Further, by using two parts, even if the shape of the microphone element 101 changes, the same
effect can be easily obtained by changing the conductive holder 401. Further, the same effect can
be obtained even when the case made of a conductive resin is fixed by a holder made of a
conductive rubber part.
[0029]
FIG. 5 shows the influence of the noise level appearing at the output of the microphone device
generated due to extraneous noise. The noise level of the microphone output when the volume
resistivity of the conductive material is changed in the microphone device of the present
invention is compared, and the noise generation level can be suppressed by reducing the volume
resistivity, and 15 MΩ · By setting the distance to cm or less, noise levels equivalent to those of a
microphone device equipped with a metal shield can be obtained, and a noise prevention effect
can be obtained. a shows the noise level of the unshielded microphone device, b shows the noise
level of the microphone device equipped with the conventional metal shield as shown in FIG. 6, c
shows a volume resistivity of 15 MΩ · cm The noise level of the microphone device of the
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present invention using the conductive case is shown, d is the noise level of the microphone
device using a conductive component having a volume resistivity of 30 MΩ · cm, and e is the
volume resistivity 1 GΩ -It is a figure which shows the noise level of a microphone apparatus at
the time of using an electroconductive component of cm. Compared to the case without the
shield, the noise level is improved by using the conductive case, and it is possible to maintain the
same noise level as the microphone device (b) equipped with the metal shield. As shown in d and
e, when the volume resistivity is large, the noise level is large. From this result, it is understood
that the volume resistivity of this conductive case is desirably 15 MΩ · cm or less.
[0030]
According to the microphone device of the present invention, since miniaturization and noise
reduction can be achieved, it is useful as a microphone device for mobile use such as portable
terminals.
[0031]
DESCRIPTION OF SYMBOLS 101 microphone element 101a metal element of microphone
element 101b signal terminal of microphone element 102 conductive rubber case 103a exterior
case 103b exterior cover 104 circuit board 105 cable 106 connector cable 401 conductive
holder 402 conductive case 502 rubber case (non-conductive) ) 507 shield case
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