JP4934552B2 - Condenser microphone unit - Google Patents

Description

  The present invention relates to a condenser microphone unit, and more particularly, to a spacer ring disposed between a diaphragm and a fixed pole.

  In a condenser microphone unit, a diaphragm and a fixed pole are disposed opposite to each other via an electrically insulating spacer ring, so that a kind of capacitor as an acoustoelectric converter is formed, and a diaphragm is formed by incoming sound waves. The change in capacitance caused by the vibration of the sound is output as an electrical audio signal via the impedance converter.

  In this case, the diaphragm is used in a state of being stretched with a predetermined tension on one surface of the support ring, and the fixed pole is used in a state of being supported by an insulating seat made of, for example, a synthetic resin material. In this specification, a diaphragm in which a diaphragm is stretched on a support ring is referred to as a “diaphragm assembly”, and a structure in which a fixed pole is supported on an insulating seat is referred to as a “fixed pole assembly”.

  The spacer ring is made by punching a resin film into a ring shape, and is sandwiched between the surface of the support ring on which the diaphragm is attached and the surface facing the diaphragm of the fixed pole. In other words, the spacer ring causes a stray capacity that reduces the sensitivity between the inner diameter of the support ring, that is, between the inner diameter of the support ring and the outer diameter of the fixed pole. In this specification, a portion where the spacer ring is sandwiched between the support ring and the fixed pole is referred to as an “overlapping portion”.

  Reducing the area of the overlapping part also reduces the problem of stray capacity, but the area that is maintained by the spacer ring is reduced, resulting in non-uniform spacing between the diaphragm and the fixed pole. It is easy to cause performance variation due to this.

  Usually, the spacer ring is made of a film material such as PET (polyethylene terephthalate) that has a high surface resistivity and a high volume resistivity and has a stable thickness in order to maintain the above-mentioned distance.

  The stray capacity of the overlapped portion is a value obtained by multiplying the electrostatic capacity in the absence of the spacer ring by the relative dielectric constant of the spacer ring, but the relative dielectric constant of PET is relatively high and about 3.0. , It will cause a significant sensitivity drop.

  In this regard, Patent Document 1 proposes a spacer ring made of a synthetic resin film having a plurality of closed cells. This spacer ring has a low relative dielectric constant because a plurality of closed cells are contained in the synthetic resin film, but if it is strongly sandwiched between the support ring and the fixed electrode, the closed cells may shrink, There are cases where the interval cannot be kept stable.

Japanese Utility Model Publication No. 6-34399

  Accordingly, an object of the present invention is to provide a condenser microphone unit including a spacer ring having a low relative dielectric constant capable of stably maintaining a distance between a support ring of a diaphragm and a fixed pole.

  In order to solve the above-mentioned problems, the invention described in claim 1 includes a diaphragm assembly in which a diaphragm is stretched on one surface of a support ring, and a fixed pole assembly in which a fixed pole is supported on an insulating seat. A unit case having a front acoustic terminal on one end side and an open end on the other end, and the diaphragm of the diaphragm assembly and the fixed pole of the fixed pole assembly between them An acoustoelectric converter is configured by being opposed to each other via an electrically insulating spacer ring, and the acoustoelectric converter is housed in the unit case with the diaphragm assembly as the front acoustic terminal side, In the condenser microphone unit in which the acoustoelectric converter is fixed in the unit case by a predetermined fixing means from the other end side of the unit case, a synthetic resin mesh material is used for the spacer ring. Features and To have.

  The invention described in claim 2 is characterized in that, in claim 1, the mesh material of the synthetic resin is a plain weave fabric of warp and weft.

  A third aspect of the present invention is characterized in that, in the first or second aspect, the synthetic resin mesh material is subjected to water repellent treatment.

  According to a fourth aspect of the present invention, in the second aspect, the volume of the working space surrounded by the diaphragm and the fixed pole, the outer peripheral surface of the acoustoelectric converter, and the inner peripheral surface of the unit case. The volume of the enclosed cylindrical space is acoustically connected through the acoustic resistance of the synthetic resin mesh material.

  According to a fifth aspect of the present invention, in the positioning unit according to any one of the first to fourth aspects, the other surface of the support ring of the diaphragm assembly is in contact with one end of the unit case. And a front mesh made of a metal net is interposed between the positioning step and the other surface of the support ring.

  According to the first aspect of the present invention, the synthetic resin mesh material is used for the spacer ring that holds the space between the diaphragm and the fixed pole, so that the air layer in the mesh material is formed in the overlapping portion. Therefore, the relative permittivity is lowered accordingly, and the sensitivity can be suppressed from decreasing.

  According to the invention described in claim 2, by using a plain weave cloth as the mesh material of the synthetic resin, in the overlapped portion, the crossing portion of the mesh warp and weft substantially serves as a spacer. Since there are many intersections, the distance between the support ring of the diaphragm and the fixed pole can be kept more stable. Further, since air exists between the warp and the weft, the relative dielectric constant is lowered accordingly.

  According to the invention described in claim 3, since the surface resistivity is improved by applying a water repellent treatment to the synthetic resin mesh material used as the spacer ring, noise generation due to leakage current can be further reduced. .

  Since the mesh material is a plain weave and has air permeability in the surface direction, according to the invention described in claim 4, the volume of the working space surrounded by the diaphragm and the fixed pole, and the acoustoelectric converter The volume of the cylindrical space surrounded by the outer peripheral surface and the inner peripheral surface of the unit case is acoustically connected via the acoustic resistance of the mesh material, so that the inner surface of the fixed pole assembly and the unit case are Unnecessary resonance due to the volume of the cylindrical space surrounded by the peripheral surface is prevented.

  According to the fifth aspect of the present invention, the positioning step portion on which the other surface of the support ring of the diaphragm assembly abuts is formed on one end side in the unit case. Since a front mesh made of a metal net is interposed between the other surface of the first and second surfaces, low-frequency sound waves from the front acoustic terminals enter the unit case through the front mesh. Thus, since it enters the volume of the cylindrical space surrounded by the outer peripheral surface of the acoustoelectric converter and the inner peripheral surface of the unit case, the low frequency response is lowered, which helps to prevent wind noise.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 is a front view of a condenser microphone unit according to the present invention as viewed from the front sound source side, FIG. 2 is a cross-sectional view taken along the line II of FIG. 1, FIG. 3 is an exploded view of FIG. FIG. 5 is a partially enlarged plan view of the ring, FIG. 5 is an enlarged view of a main part of the present invention, and FIG. 6 is a mechanical equivalent circuit diagram of the condenser microphone unit of the present invention.

  First, referring to FIG. 1 to FIG. 3, this condenser microphone unit 1 is basically composed of a unit case 10 and a diaphragm assembly in which a diaphragm 22 is stretched on one surface of a support ring 21. A solid body 20, a fixed pole assembly 30 in which a fixed pole 32 is supported on an insulating seat 31, and an electrically insulating spacer ring 40 disposed between the diaphragm assembly 20 and the fixed pole assembly 30. I have.

  The unit case 10 is formed in a bottomed cylindrical shape with a metal material such as aluminum, has a front acoustic terminal 11 on one end 10a side, and is open on the other end 10b side. The unit case 10 is provided with a dust-proof net 12 that covers the front acoustic terminal 11.

  On the inner surface of the unit case 10 on the other end 10b side, a female screw 13 to which a lock ring 50 described later is screwed is formed. A positioning step 14 for the diaphragm assembly 20 is provided on the one end 10 a side in the unit case 10.

  A support ring (also called a diaphragm ring) 21 in the diaphragm assembly 20 is made of metal and has conductivity. The diaphragm 22 is made of a film material in which a metal vapor deposition film is formed on a synthetic resin thin film such as polyethylene terephthalate (PET), and is stretched in a state where a predetermined tension is applied to one surface of the support ring 21. Yes.

  Since the insulating seat 31 provided in the fixed pole assembly 30 is a disc body made of synthetic resin, and the condenser microphone unit 1 in this embodiment is unidirectional, the rear acoustic terminal 311 is formed in the insulating seat 31. It is installed. An acoustic resistance material 314 is provided on the rear acoustic terminal 311.

  The fixed pole 32 is formed of a metal material such as aluminum or brass alloy, and is fixed to the surface of the insulating seat 31 that faces the diaphragm assembly 20. A rear air chamber 312 that communicates with the rear acoustic terminal 311 is provided between the fixed pole 32 and the insulating seat 31.

  The fixed pole 32 has a plurality of sound holes 321 for allowing sound waves from the rear acoustic terminal 311 to act on the back surface side of the diaphragm 22. An electrode rod 313 that is electrically connected to the fixed pole 32 via a wiring member (not shown) is integrally attached to the insulating seat 31.

  In the case of the membrane electret model, the electret dielectric film is integrally formed on the diaphragm 22, and in the case of the back electret model, the electret dielectric film is integrally formed on the surface of the fixed pole 32 that faces the diaphragm 22. It is formed.

  In the unit case 10, the diaphragm assembly 20 and the fixed pole assembly 30 are combined with each other such that the diaphragm 22 and the fixed pole 32 face each other, and a spacer ring 40 is disposed therebetween. The capacitor type acoustoelectric converter 2 is configured.

  Thereafter, the lock ring 50 having a male screw is screwed into the female screw 13 on the other end 10b side of the unit case 10, and the other surface of the support ring 21 of the diaphragm assembly 20 is positioned as described above. The entire acoustoelectric converter 2 is fixed in the unit case 10 by contacting the stepped portion 14. Instead of the lock ring 50, the other end 10b of the unit case 10 may be caulked to fix the acoustoelectric converter 2.

  At this time, the distance between the diaphragm 22 and the fixed pole 32 is held by the spacer ring 40, but as shown in FIG. 3, the spacer ring 40 has an inner diameter of the support ring 21 and an outer diameter of the fixed pole 32. Is sandwiched between the overlapping portions B.

  In the overlapped portion B, the spacer ring 40 causes a stray capacity that reduces the sensitivity. In the present invention, a synthetic resin mesh material is used for the spacer ring 40 in order to suppress sensitivity reduction due to stray capacity as much as possible.

  The mesh material of the synthetic resin may be one in which the warp and the weft are integrally combined in the same plane by molding or the like, but the warp 41 and the weft 42 are plain woven as shown in FIG. A woven fabric (cloth) is preferable.

  According to this plain weave, in the overlapping portion B, the intersecting portion C of the warp yarn 41 and the weft yarn 42 of the mesh substantially serves as a spacer, and there are many intersecting portions C. The distance between the support ring 21 of the plate 22 and the fixed pole 32 can be kept stable. Further, since air exists between the warp yarn 41 and the weft yarn 42, the relative dielectric constant is reduced accordingly.

  As Example 1 according to the present invention, a plain weave polyester mesh (T-No. 305T manufactured by NBC Kogyo Co., Ltd.) was used for the spacer ring 40, and the capacitance at the overlapped portion B was measured to be 8.2 pF. .

  As Comparative Example 1 with respect to Example 1, the capacitance in the overlapped portion B was measured using a spacer ring made by punching a normal PET film, and found to be 16.9 pF.

  In both Example 1 and Comparative Example 1, the effective capacitance of the portion that vibrates with the sound wave of the diaphragm 22 existing inside the overlapped portion B was 29.7 pF. The sensitivity decreased by the stray capacity is -2.1 dB in the case of Example 1 and -3.9 dB in the case of Comparative Example 1, and the sensitivity difference is 1.8 dB. According to Example 1, the sensitivity is about 23%. The improvement was seen.

  Next, in consideration of the case where the diaphragm assembly 20 and the fixed pole assembly 30 which are components of the acoustoelectric converter 2 are housed in the unit case 10, as shown in FIG. A cylindrical space A2 is provided as a slight clearance between the inner peripheral surface 10 and the assemblies 20, 30 (acoustoelectric transducer 2).

  In the case where the spacer ring 40 is a plain weave mesh material, it has a certain degree of air permeability in the surface direction, so that the volume of the working space A1 surrounded by the diaphragm 22 and the fixed pole 32 and the outer periphery of the acoustoelectric transducer 2 are increased. Since the volume of the cylindrical space A2 surrounded by the surface and the inner peripheral surface of the unit case 10 is acoustically connected via the acoustic resistance of the mesh material, the outer peripheral surface of the acoustoelectric transducer 2 And unnecessary resonance due to the volume of the cylindrical space A2 surrounded by the inner peripheral surface of the unit case 10 is prevented.

  Preferably, the synthetic resin mesh material used for the spacer ring 40 is impregnated with a fluorine coating material as a water repellent treatment. According to this, the surface resistivity of the spacer ring 40 is improved, and noise generation due to leakage current can be suppressed.

  3 and 5, a front mesh 60 made of a wire mesh is placed on one end 10 a side in the unit case 10, and the positioning stage formed on the support ring 21 of the diaphragm assembly 20 and the unit case 10. It may be sandwiched between the part 14.

  According to this, among the sound waves that enter the unit case 10 from the front acoustic terminal 11, low-frequency sound waves pass through the front mesh 60 and the outer peripheral surface of the acoustoelectric transducer 2 and the inner peripheral surface of the unit case 10. Since it enters the volume of the cylindrical space A2 surrounded by, the low-frequency response is lowered, which helps to prevent wind noise.

  The front mesh 60 may be formed in either a ring shape or a single disk shape having substantially the same diameter as the support ring 21, but in the case of a single disk shape, a dustproof wire mesh is used. 12 can be omitted. On the other hand, the skirt of the dustproof wire mesh 12 can be extended and the skirt can be used as the front mesh 60.

  FIG. 6 shows a machine equivalent circuit for facilitating understanding of the acoustic characteristics of the condenser microphone unit 1 having the above-described configuration. P1 is a front sound source, P2 is a rear sound source, rf is an acoustic resistance of the front mesh 60, rs is an acoustic resistance of the spacer ring 40 made of a mesh material, mo, so, and ro are impedances of the diaphragm 22, and ss is the above cylindrical space. The volume of A2, s1 is the volume of the rear air chamber 312, and r1 is the acoustic resistance due to the acoustic resistance material 314 of the rear acoustic terminal 311.

The front view seen from the front sound source side which shows the capacitor | condenser microphone unit which concerns on embodiment of this invention. II sectional view taken on the line of FIG. The exploded view of FIG. The partial enlarged top view of the spacer ring used by this invention. The principal part enlarged view of this invention. The machine equivalent circuit diagram of the capacitor | condenser microphone unit which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor microphone unit 2 Acoustoelectric converter 10 Unit case 11 Front acoustic terminal 14 Positioning step part 20 Diaphragm assembly 21 Support ring 22 Diaphragm 30 Fixed pole assembly 31 Insulation seat 311 Rear acoustic terminal 312 Rear air chamber 313 Electrode Rod 314 Acoustic resistance material 32 Fixed pole 321 Sound hole 40 Spacer ring 41 Warp thread 42 Weft thread 50 Lock ring 60 Front mesh

Claims (5)

A diaphragm assembly in which a diaphragm is stretched on one surface of the support ring, a fixed pole assembly in which a fixed pole is supported on an insulating seat, a front acoustic terminal on one end side, and the other end An open unit case, and the diaphragm of the diaphragm assembly and the fixed pole of the fixed pole assembly are arranged to face each other via an electrically insulating spacer ring between them. The electric transducer is configured, the acoustoelectric transducer is housed in the unit case with the diaphragm assembly as the front acoustic terminal side, and the acoustic signal is received from the other end side of the unit case by a predetermined fixing means. In the condenser microphone unit formed by fixing the electrical converter in the unit case,
A condenser microphone unit, wherein a synthetic resin mesh material is used for the spacer ring.   2. The condenser microphone unit according to claim 1, wherein the synthetic resin mesh material is a plain weave fabric of warp and weft.   3. The condenser microphone unit according to claim 1, wherein the synthetic resin mesh material is subjected to a water repellent treatment.   The volume of the working space surrounded by the diaphragm and the fixed pole, and the volume of the cylindrical space surrounded by the outer peripheral surface of the acoustoelectric converter and the inner peripheral surface of the unit case are the synthetic resin. The condenser microphone unit according to claim 2, wherein the condenser microphone unit is acoustically connected through acoustic resistance of the mesh material.   A positioning step portion with which the other surface of the support ring of the diaphragm assembly abuts is formed on one end side in the unit case, and the positioning step portion and the other surface of the support ring are in contact with each other. The condenser microphone unit according to any one of claims 1 to 4, wherein a front mesh made of a metal net is interposed therebetween.

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