JP3574770B2 - Front electret condenser microphone - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a front electret condenser microphone, and more particularly, to a front electret condenser microphone that forms a capacitor between a conductive capsule and a diaphragm opposed thereto.
[0002]
[Prior art]
A foil electret condenser microphone will be described with reference to FIG. The cylindrical conductive capsule 11 made of aluminum has a front plate 11a integrally formed on the front surface thereof. A sound hole 12 is formed at the center of the front plate 11a. A cloth 13 is coated on the outer surface of the front plate 11a. A vibrating membrane ring 14 made of a metal material is positioned in contact with a peripheral edge of the inner surface of the front plate 11a, and both are electrically connected. An electret vibrating film 15 is attached to the surface of the vibrating film ring 14 opposite to the front plate 11a. The electret vibration film 15 has a thickness of 12. A metal thin film is formed on one surface of a fluoroethylene propylene (FEP) film, which is a relatively thick polymer film of about 5 μm, and the polymer film is electrically polarized. The electret vibrating film 15 is attached such that its metal-deposited film side is in electromechanical contact with the vibrating film ring 14.
[0003]
The plate-shaped back electrode 17 made of a metal material is attached to the electret vibrating film 15 through a ring-shaped spacer 16 made of an insulating material. The back pole 17 is held on a front end face of a cylindrical back pole holder 18. An impedance conversion IC element 21 is accommodated and positioned in a back chamber 19 formed inside the back pole holder 18. The input terminal 22 of the impedance conversion IC element 21 is electrically connected to the back pole 17. Here, the opening end of the cylindrical conductive capsule 11 is closed by a wiring board 24, and the output terminal 23 and the common terminal (not shown) of the impedance conversion IC element 21 project from the wiring board 24 and Connected to wiring. The opening end of the conductive capsule 11 is bent and caulked to the back surface of the wiring board 24. In the case of a foil electret condenser microphone, a capacitor is formed between the metal thin film forming the electret vibrating film 15 and the back electrode 17.
[0004]
A back electret type condenser microphone will be described with reference to FIG. In the above-mentioned foil electret condenser microphone, the diaphragm itself is electretized. On the other hand, in the back electret condenser microphone, the electret polymer film 26 is directly formed in close contact with the upper surface of the back electrode 17. That is, an FEP film as an electret material is welded or bonded to the upper surface of the back electrode 17 to form a polarized electret. In the case of a back electret condenser microphone, a condenser is formed between the conductive vibration film 29 and the back electrode 17.
[0005]
A front electret condenser microphone will be described with reference to FIG. The front electret condenser microphone has a structure in which an electret polymer film 26 is formed on the inner surface of a front plate 11a in which the sound hole 12 is formed, and a conductive vibration film 29 is positioned and fixed in close proximity to the film. . In the case of this front electret condenser microphone, a capacitor is formed between the front plate 11a of the conductive capsule 11 and the conductive vibration film 29 positioned opposite to the front plate. Unlike the wheel electret type and the back electret type, it does not have the back electrode 17.
[0006]
[Problems to be solved by the invention]
The assembled electret condenser microphone is used by being electromechanically connected to a circuit board. In this case, the electrical connection between the output terminal of the microphone and the connection terminal of the electrical wiring formed on the circuit board is usually made by soldering. However, today, there is a method in which pressure is applied to the front plate 11a of the conductive capsule 11 of the electret microphone, and the output terminal of the microphone is electrically connected to the connection terminal of the electric wiring of the circuit board by pressing the microphone. Has been adopted.
[0007]
Here, considering the effect of applying pressure from the outside to the front plate 11a of the conductive capsule 11, in the case of the foil electret condenser microphone of FIG. 3, the condenser has the electret diaphragm 15 as described above. It is configured between the formed metal thin film and the back electrode 17. This capacitor is not structurally and mechanically directly connected to the front plate 11a of the conductive capsule 11, but is separated from the front plate 11a. Therefore, even if pressure is applied to the front plate 11a from the outside, the diaphragm 15 The electrode spacing between the deposited metal thin film and the back electrode 17 does not change.
[0008]
Similarly, in the case of the back electret condenser microphone shown in FIG. 4, the capacitor constituted by the conductive vibrating membrane 29 and the back electrode 17 is not directly and structurally and mechanically coupled to the front plate 11a. Therefore, even if a pressure is externally applied to the front plate 11a, the distance between the two electrodes does not change.
On the other hand, in the conventional front electret condenser microphone, as shown in FIG. 5, an electret polymer film 26 is formed on the inner surface of the front plate 11a in which the sound hole 12 is formed. That is, the electret polymer film 26 forms a capacitor in a state interposed between the front plate 11a of the conductive capsule 11 and the conductive vibration film 29 positioned opposite thereto. Here, when the front plate 11a of the conductive capsule 11 is pressurized, the electrode spacing between the front plate 11a forming the capacitor and the conductive vibration film 29 facing the front plate 11a fluctuates. As a result, the sensitivity of sound pressure detection of the microphone fluctuates. In particular, since the electret polymer film 26 interposed between the front plate 11a constituting the capacitor and the conductive vibration film 29 opposed to the front plate 11a has an extremely large dielectric constant, the sensitivity of the sound pressure detection is reduced accordingly. Fluctuations are significant.
[0009]
The present invention provides a front electret condenser microphone that solves the above-described problem in which the sensitivity of sound pressure detection of the microphone does not fluctuate even when the front plate 11a of the conductive capsule 11 in which the microphone sound hole is formed is pressurized. To provide.
[0010]
[Means for Solving the Problems]
Claim 1: The conductive capsule 11, the conductive reinforcing plate 17 'in which the peripheral ring portion 17a is formed on the peripheral edge and the electret polymer film 26 is bonded on the lower surface, and the conductive vibration film holding ring 14 on the peripheral edge A conductive vibrating membrane 29, which is held as such, and a ring-shaped spacer 16, and the peripheral ring portion 17a of the conductive reinforcing plate 17 'is housed in the conductive capsule 11 in a state of being engaged with the front plate 11a. In addition, a front electret condenser microphone in which the conductive vibration film 29 is accommodated in the conductive capsule 11 with the ring-shaped spacer 16 interposed therebetween and facing the electret polymer film 26 is formed.
[0011]
Claim 2: The front electret condenser microphone according to claim 1, comprising a conductive reinforcing plate holder 18 'and a wiring board 24 on which the impedance converting IC element 21 is mounted and electrically connected, The wiring board 24 is accommodated in the conductive capsule 11 with the conductive reinforcing plate holder 18 ′ interposed between the wiring board 24 and the conductive vibration film holding ring 14, and the open end of the conductive capsule 11 is wired. A front electret condenser microphone caulked to the back of the substrate 24 was constructed.
[0012]
Claim 3: In the front electret condenser microphone according to any one of claims 1 and 2, a cylindrical space is provided between the cylindrical conductive capsule 11 and a member accommodated therein. A front electret condenser microphone containing the compatible resin molded member 30 was configured.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIG. In FIG. 1, members common to members in the conventional example are denoted by common reference numerals. A front plate 11a, which is the bottom of the conductive capsule, is integrally formed with the cylindrical conductive capsule 11 made of aluminum. A sound hole 12 is formed in the center of the front plate 11a. Reference numeral 17 'denotes a conductive reinforcing plate introduced according to the present invention, which is made of a highly rigid metal material. A peripheral ring portion 17a is formed on the periphery of the conductive reinforcing plate 17 '. A peripheral ring portion 17a of a conductive reinforcing plate 17 'is positioned in contact with a peripheral portion of the inner surface of the front plate 11a of the conductive capsule 11, and the front plate 11a and the peripheral ring portion 17a are electromechanically connected to each other. are doing. A plurality of through holes 17b are formed in the conductive reinforcing plate 17 ', and communicate with the upper and lower surfaces of the back electrode. An electret polymer film 26 is thermally welded to the entire lower surface of the conductive reinforcing plate 17 'in the drawing. The electret polymer film 26 has a thickness of 12. It is made of a fluoroethylene propylene (FEP) film, which is a relatively thick polymer film of about 5 μm, and is electrically polarized. The ring-shaped spacer 16 is interposed between the electret polymer film 26 welded to the lower surface of the conductive reinforcing plate 17 ′ and the peripheral portion of the conductive vibration film 29, and This provides room for vibration with the film 26. The conductive vibration film holding ring 14 made of a metal material is joined to a peripheral portion of the conductive vibration film 29, and thereby the shape of the conductive vibration film 29 is maintained. The conductive reinforcing plate 17 'is supported by a conductive reinforcing plate holder 18' made of a cylindrical metal material with the conductive vibration film holding ring 14 interposed therebetween. Numeral 30 denotes a cylindrical resin molding member, which is housed in a gap between the cylindrical conductive capsule 11 and a member housed therein, and is formed of a cylindrical conductive capsule 11 and a member housed therein. Electrically isolate between the two to strengthen the mechanical engagement.
[0014]
Here, the open end of the cylindrical conductive capsule 11 is closed as follows by the wiring board 24 on which the impedance conversion IC element 21 is mounted and electrically connected. That is, a conductive reinforcing plate 17 ′ having an electret polymer film 26 thermally welded to the lower surface, a ring-shaped spacer 16, a conductive vibration film 29 whose peripheral edge is held by the conductive vibration film holding ring 14, and a conductive reinforcement. The plate holders 18 'are accommodated in the cylindrical conductive capsule 11 in this order. Finally, the opening end of the conductive capsule 11 is mounted with the impedance conversion IC element 21 and closed by the electrically connected wiring board 24, and the opening end is bent and crimped to the rear surface of the wiring board 24.
[0015]
In the above-mentioned front electret condenser microphone, the conductive vibration film 29 forms one electrode of the capacitor, and the conductive reinforcing plate 17 'made of a metal material forms the other electrode of the capacitor. The conductive vibration film 29, which is one of the electrodes, is a field-effect transistor that forms an impedance conversion circuit via the conductive vibration film holding ring 14 made of a metal material, the conductive reinforcing plate holder 18 ', and the wiring of the wiring board 24. To the gate of The conductive reinforcing plate 17 ', which is the other electrode, is electrically connected to the ground terminal via the conductive capsule 11 made of a metal material and the wiring of the wiring board 24. When acoustic vibration enters the microphone through the sound hole 12 of the front plate 11a of the conductive capsule 11, the conductive vibration film 29 vibrates due to this, and the conductive vibration film 29 corresponding to this vibration and the conductive vibration film 29 The change in the electric capacity between the conductive reinforcing plate 17 'and the conductive reinforcing plate 17' is output as an electric signal.
[0016]
【The invention's effect】
As described above, according to the present invention, a conductive reinforcing plate 17 'in which a peripheral ring portion 17a is formed on a peripheral edge and an electret polymer film 26 is bonded on a lower surface, and a conductive vibration film on a peripheral edge portion A conductive vibration film 29 which is held by joining the holding ring 14 and a ring-shaped spacer 16 are provided, and the conductive reinforcing plate 17 ′ is electrically conductive in a state where the peripheral ring portion 17 a is engaged with the front plate 11 a. A structure in which the conductive vibration film 29 is accommodated in the capsule 11 and faces the electret polymer film 26 with the ring-shaped spacer 16 interposed between the conductive reinforcing plate 17 ′ and the conductive vibration film 29 is adopted. Constitutes a capacitor. That is, the conductive reinforcing plate 17 'constituting the capacitor is independent of the front plate 11a, and has a loose mechanical coupling with the area of the front plate 11a which is deformed by applying pressure. Since the pressure transmitted from the front plate 11a to the conductive reinforcing plate 17 'is relieved and the conductive reinforcing plate 17' itself has a large rigidity, the conductive reinforcing plate 17 'is not deformed. Become smaller. Therefore, the capacitance fluctuation of the capacitor is small accordingly, and the fluctuation of the sound pressure detection sensitivity as the microphone is small. Further, since a slight gap is formed between the front plate 11a of the conductive capsule 11 and the upper surface of the conductive reinforcing plate 17 ', the deformation of the front plate 11a is absorbed in this gap, and the gap between the front plate 11a and the conductive reinforcing plate 17' is reduced. The transmission of pressure is even smaller.
[0017]
Then, the inner surface of the conductive capsule 11 and the conductive reinforcing plate 17 ′ are accommodated by housing the cylindrical resin-molded member 30 in the gap between the cylindrical conductive capsule 11 and the member housed therein. Are firmly engaged with each other. Therefore, even if the pressure applied to the front plate 11a is transmitted to the conductive reinforcing plate 17 ', the conductive reinforcing plate 17' is mechanically firmly held by the conductive capsule 11, so that there is no room for deformation. It becomes even smaller.
[Brief description of the drawings]
FIG. 1 illustrates an embodiment.
FIG. 2 is a diagram illustrating a reinforcing plate.
FIG. 3 illustrates a conventional example.
FIG. 4 is a diagram illustrating another conventional example.
FIG. 5 is a diagram illustrating still another conventional example.
[Explanation of symbols]
REFERENCE SIGNS LIST 11 conductive capsule 11 a front plate 12 sound hole 14 conductive vibration film holding ring 16 ring-shaped spacer 17 ′ conductive reinforcing plate 17 a peripheral ring portion 17 b through hole 18 ′ conductive reinforcing plate holder 21 impedance conversion IC element 24 wiring Substrate 26 Electret polymer film 29 Conductive vibration film 30 Cylindrical resin molding

Claims (3)

A conductive capsule, a conductive reinforcing plate in which a peripheral ring portion is formed on the periphery and an electret polymer film is joined on the lower surface, and a conductive vibration film held by joining a conductive vibration film holding ring to the periphery. , A ring-shaped spacer,
The conductive reinforcing plate is housed in the conductive capsule with the peripheral ring part engaged with the front plate, and the conductive vibration film is opposed to the electret polymer film with a ring-shaped spacer interposed between the conductive capsule and the conductive capsule. A front electret condenser microphone characterized by being housed. The front electret condenser microphone according to claim 1,
A conductive reinforcing plate holder and a wiring board on which an IC element for impedance conversion is mounted and electrically connected are provided, and the wiring board is interposed between the conductive reinforcing plate holder and the conductive vibration film holding ring. A front electret-type condenser microphone characterized in that it is housed in a conductive capsule in an upright state, and an opening end of the conductive capsule is caulked to a back surface of a wiring board. A front electret condenser microphone according to any one of claims 1 and 2,
A front electret-type condenser microphone characterized in that a tubular synthetic resin molded member is accommodated in a gap between a tubular conductive capsule and a member accommodated therein.

Images