JP5139698B2 - Condenser microphone unit - Google Patents

Description

  The present invention provides a condenser microphone capable of avoiding the occurrence of resonance caused by a gap portion inevitably left between an inner peripheral surface of a case body and an outer peripheral surface of a built-in unit accommodated in the case body. It is a technology related to the unit.

Among the small and lightweight condenser microphone units, the built-in unit consisting of multiple components is accommodated and held in the case body by caulking the open edge side of the case body that has a bottomed cylindrical shape. There is something. In this type, as shown in the following Patent Document 1 (see FIG. 1 of the same document), since it is necessary to facilitate the introduction of components into the case body, the inner diameter of the case body is the maximum of the built-in unit. It is formed larger than the outer diameter.
JP 2006-74149 A

  Therefore, the condenser microphone unit inevitably has a gap between the inner peripheral surface of the case body and the outer peripheral surface of the built-in unit when the built-in unit is fixed by caulking the open edge of the case body. It is left and formed.

  FIG. 3 is an explanatory diagram showing an example of the internal structure of a conventional condenser microphone unit. According to the figure, a condenser microphone unit (hereinafter referred to as “microphone unit”) 1 includes a case body 2 having a bottomed cylindrical shape with a bottom 2a on one side and an opening 2b on the other, It is comprised at least by the built-in unit 4 which consists of a combination of the some structural member accommodated in the case body 2. FIG.

  Among these, the case body 2 made of a conductive metal such as aluminum has a front sound hole 2c serving as a front acoustic terminal on the bottom 2a. In addition, a front mesh 3 made of a conductive material such as a wire mesh for shielding the front sound hole 2c is disposed on the inner bottom surface 2d of the bottom 2a.

  On the other hand, the built-in unit 4 includes a diaphragm ring 5a disposed on the bottom 2a side with the diaphragm 5b stretched, a back electrode plate 5d disposed opposite the diaphragm 5b via a spacer 5c, These are integrally combined by individual components including an insulating seat 5e that supports the back electrode plate 5d, a printed circuit board 5f that seals the opening 2b side, and an impedance converter 5g that is mounted on the printed circuit board 5f. Yes.

  In this case, a caulking portion 2e formed by caulking the open end edge portion of the case body 2 is pressed against the printed circuit board 5f, and the caulking pressure generated by the caulking portion 2e is received. Thereby, the position of the built-in unit 4 including the printed board 5f is fixed in the case body 2. In this case, the gap G is inevitably left between the outer peripheral surface 4 a of the built-in unit 42 and the inner peripheral surface 2 f of the case body 2.

  The printed circuit board 5f is provided with a plurality of rear sound holes 6a that serve as rear acoustic terminals. The built-in unit 4 is secured between the rear sound hole 6a, the through hole 6b provided in the insulating seat 5e in a positional relationship facing the rear sound hole 6a, and the back electrode plate 5d and the insulating seat 5e. A sound path 6 is formed through the air chamber 6c and the through hole 6d of the back electrode plate 5d to reach the diaphragm 5b.

  In addition, the built-in unit 4 includes an acoustic resistance material R embedded in a circumferential recess 7 provided on the printed circuit board 5f side of the insulating seat 5e and communicating with the sound path 6, and is unidirectional to the condenser microphone unit 1. It is the composition which can be given.

  By the way, in the microphone unit 1 as shown in FIG. 3, surface roughness such as irregularities tends to occur on the finished surface of each component of the built-in unit 4. For this reason, there are many cases in which individual constituent members come into contact with the mating member due to such surface roughness.

  On the other hand, such a gap may be acoustically coupled to the gap G. In particular, the diaphragm ring 5a having the surface roughness and the front mesh 3 may be in contact with each other by generating a narrow gap Ga. In such a case, the gap Ga and the gap G are acoustically coupled. It becomes.

  FIG. 4 is an equivalent circuit diagram showing the acoustic system elements of the microphone unit 1 of FIG. 3 corresponding to each element of the electric circuit when the gap Ga and the gap G are acoustically coupled. According to the figure, it is clear that the acoustic mass (mL) of the gap Ga and the acoustic capacity (ss) of the gap G form a resonance circuit.

  Incidentally, in FIG. 4, mf is the acoustic mass of the front sound hole 2c, sf is the acoustic stiffness of the front mesh 3, m0 is the mass of the diaphragm 5b, s0 is the stiffness of the diaphragm 5b, and r0 is the diaphragm. 5b braking resistance, s1 is the acoustic stiffness of the air chamber 6c, r1 is the acoustic resistance of the acoustic resistance material R, P1 is the sound pressure on the front sound hole 2c side, and P2 is the sound pressure on the rear sound hole 6a side Respectively.

  That is, the gap Ga and the gap G are acoustically coupled to each other to form a resonance circuit by coupling the mutual acoustic reactance components, that is, the acoustic mass in the gap Ga and the acoustic capacitance in the gap G. Will end up. In such a case, the microphone unit 1 generates resonance and deteriorates the directivity frequency response in the vicinity of the resonance frequency that is set in a high range in advance.

  For this reason, at the prototype stage of the microphone unit 1, the influence of resonance due to the generation of the gap Ga is measured, and measures are taken based on the measurement results to complete the prototype. In addition, after going through the prototype stage, the measures taken for the prototype were applied to each actual product to move to the mass production stage.

  However, since the volume of the gap Ga varies in the surface roughness of the diaphragm ring 5a, it is not constant for each individual microphone unit 1, and the degree of influence of resonance is also different. I was sorry. That is, even if the microphone unit 1 shown in FIG. 3 is mass-produced based on the prototype, there is a problem that the directional frequency response still varies for each product.

  In view of the above-described problems of the prior art, the present invention minimizes the reactance component generated by the void portion by densely arranging the elastic acoustic resistance material in the void portion, and the surface of each component member in the built-in unit. An object of the present invention is to provide a condenser microphone unit capable of effectively avoiding the occurrence of resonance even when there is an acoustic coupling between a gap and a gap generated due to roughness.

The present invention has been made to achieve the above object, and includes a case body that has a bottomed cylindrical shape, a diaphragm ring that is stretched and arranged on the bottom side of the case body, and the case body. And a built-in unit comprising a combination of a plurality of constituent members that are easily accommodated in the case body, including a printed circuit board that is sealed by caulking through a caulking portion. The built-in unit has a thickness of a front mesh disposed on the inner bottom surface side of the case body in a condenser microphone unit formed by leaving a gap between the outer circumferential surface and the inner circumferential surface of the case body. within the gap portion between the separation position of the diaphragm ring up to the position immediately before the crimping portion, minimizing acoustic reactance component generated by the airspace Most major that so as not to form a resonance circuit between the gap portion and the gap is generated between the elastic acoustic resistance material closely orbiting disposed between the diaphragm ring and the front mesh order to Features.

In this case, it is preferable that the sound passage is provided extending from the rear sound hole side where the printed circuit board has to the vibration plate side.

  In addition, in this case, it is preferable that the printed circuit board is provided with a notch in a part of the peripheral edge thereof so that the gap is communicated with the rear sound hole side.

  According to the first aspect of the present invention, the elastic acoustic resistance material that is arranged in the gap portion can fill the gap portion closely and minimize the reactance component generated by the gap portion. Therefore, the elastic acoustic resistance material does not form a resonance circuit even if the gap portion, the gap generated between the diaphragm ring and the front mesh are connected to each other, so that the condenser microphone unit can effectively avoid the occurrence of resonance. Can be provided.

  In addition, the condenser microphone unit can be configured to effectively avoid the occurrence of resonance, eliminating the need for countermeasures against the effects of resonance that had been done for each individual product and mass production without varying the directional frequency response. Can be migrated to.

  According to the invention of claim 2, since the condenser microphone unit can exhibit unidirectionality, a narrow directional microphone having excellent performance can be formed by being incorporated in the acoustic tube.

  Further, according to the invention of claim 3, since a notch portion communicating with the gap portion is provided in a part of the peripheral edge portion of the printed circuit board, when the condenser microphone unit is incorporated in the acoustic tube, The difference in sound pressure between the side sound hole side and the rear sound hole side can be reduced, and a narrow directivity microphone that reliably reduces wind noise can be formed.

  FIG. 1 shows an example of the present invention, and FIG. 2 is an explanatory diagram showing the internal structure of another example of the present invention. The microphone unit 11 shown in these drawings has the same member configuration except that the printed circuit board 48 in FIG. 2 includes a notch 48b in a part of the peripheral portion thereof. Will be explained.

  According to FIG. 1, the microphone unit 11 has a bottom body 23 on one side and an opening 25 on the other side, and a case body 22 having a bottomed cylindrical shape, and a plurality of configurations housed in the case body 22. It is comprised at least by the built-in unit 42 which consists of a combination of members.

  Of these, the case body 22 made of a conductive metal such as aluminum has a front sound hole 24 to be a front acoustic terminal at the bottom 23, and a front mesh 32 made of a conductive material on the inner bottom surface 23 a side of the bottom 23. It is arranged. The front mesh 32 has a structure capable of ensuring at least axial ventilation, and shields the front sound hole 24 from the inner bottom surface 23a side. The front mesh 32 can also be bonded to the inner bottom surface 23a side of the bottom 23 with an adhesive.

  On the other hand, the built-in unit 42 is formed by combining individual components shown below. That is, the diaphragm 44 is stretched between the constituent members, and the diaphragm ring 43 disposed on the bottom 23 side of the case body 22 and the back electrode disposed opposite to the diaphragm 44 via the spacer 45. It includes at least a board 46, an insulating seat 47 that supports the back electrode board 46, and a printed circuit board 48 that is mounted on the side of the opening 25 of the case body 22 by mounting the impedance converter 49.

  As shown in FIG. 1, the case body 22 houses a built-in unit 42 formed by combining individual constituent members based on a predetermined positional relationship. In this case, a printed circuit board 48 that seals the opening 25 is fixed by caulking through a caulking portion 26 formed by bending the open end edge side of the case body 22 inward.

  The built-in unit 42 is fixed in position in the case body 22 by receiving caulking pressure applied to the printed circuit board 48 via the caulking portion 26.

  Further, the built-in unit 42 is provided separately from the plurality of rear sound holes 48a as rear acoustic terminals of the printed circuit board 48 that is a component of the built-in unit 42 in the insulating seat 47 in a positional relationship facing the rear sound holes 48a. A sound path P that reaches the diaphragm 44 through the through hole 47a, the air chamber 47b secured between the insulating seat 47 and the back electrode plate 46, and the through hole 46a of the back electrode plate 46. Is provided.

  Further, the built-in unit 42 is provided with an insulating seat 47 having a circular recess 47 c communicating with the through hole 47 a and in which the acoustic resistance material R is embedded. As described above, the built-in unit 42 includes the acoustic resistance material R and the sound path P embedded in the circumferential recess 47 c, so that the microphone unit 11 can be given unidirectionality.

  On the other hand, the case body 22 is formed so that the inner diameter thereof is larger than the maximum outer diameter of the built-in unit 42 in order to smoothly and smoothly accommodate the constituent members of the built-in unit 42. For this reason, the built-in unit 42 is disposed in the case body 22 via the gap G inevitably left between the outer peripheral surface 42 a and the inner peripheral surface 27 of the case body 22.

  In addition, as shown in FIG. 1, an elastic acoustic resistance material 52 that is in close contact with the inner peripheral surface 27 of the case body 22 and the outer peripheral surface 42a on the built-in unit 42 side is arranged around the gap G. The entire microphone unit 11 is formed. In this case, as the elastic acoustic resistance material 52, for example, sponge, paper, non-woven fabric or the like can be suitably used.

  In the example shown in FIG. 1, since the notched portion 48 b is not provided in the printed circuit board 48, the opening portion 25 side of the gap portion G is closed by the caulking portion 26. In the other example shown in FIG. 2, since the notch 48b is provided in the peripheral portion of the printed circuit board 48, the gap G is opened through the notch 48b. In this case, at least one notch 48 b is provided along the periphery of the printed circuit board 48.

  Furthermore, in this case, each component member has a surface roughness including irregularities on the surface in contact with the counterpart material, and the built-in unit 42 is formed while a gap is interposed in the contact surface with the counterpart material. Become.

  Next, the operation and effect of the present invention will be described with reference to the equivalent circuit diagram shown in FIG. 4 as a conventional example.

  First, in the case body 22 in which the front mesh 32 is disposed on the inner bottom surface 23 a, the elastic acoustic resistance material 52 is arranged around the entire inner peripheral surface 27. Next, in the case body 22 in which the elastic acoustic resistance material 52 is disposed, a diaphragm ring 43 with a diaphragm 44 stretched, a spacer 45, and a back electrode plate 46 opposed to the diaphragm 44 from the bottom 23 side. The built-in unit 42 is assembled by housing individual components in the order of the insulating seat 47 to be supported and the printed circuit board 48 having the impedance converter 49.

  In this case, the individual constituent members of the built-in unit 42 can be smoothly accommodated and arranged in the case body 22 while pressing the elastic acoustic resistance material 52 arranged in the case body 22 on the outer peripheral side against the case body 22 side. it can. At that time, since the elastic acoustic resistance material 52 can be freely compressed and deformed in the radial direction by the elastic force provided, it does not hinder the smooth accommodation arrangement of the individual components.

  After the built-in unit 42 is accommodated in the case body 22, the caulking portion 26 is formed. The built-in unit 42 including the printed circuit board 48 is positioned in the case body 22 with the outer peripheral surface 42 a side thereof being in close contact with the elastic acoustic resistance material 52 via the printed circuit board 48 that is caulked and fixed by the caulking portion 26. Fixed. At this time, the gap G between the inner peripheral surface 27 of the case body 22 and the outer peripheral surface 42 a of the built-in unit 42 is densely filled with the elastic acoustic resistance material 52.

  On the other hand, since the individual constituent members in the built-in unit 42 are accompanied by surface roughness, they come into contact with each other through a gap. In particular, when the gap Ga connected to the front sound hole 24 is generated between the diaphragm ring 43 and the front mesh 32, the gap Ga communicates with the gap G and the mutual reactance components are combined. It will be. Therefore, in the conventional microphone unit 1 shown in FIG. 3, a resonance circuit as shown in FIG. 4 is formed.

  However, since the microphone unit 11 shown in FIG. 1 and FIG. 2 is formed by the elastic acoustic resistance material 52 being arranged around the gap G, the acoustic impedance of the gap G is mainly composed of a resistance component and reactance. Components will be minimized.

  Therefore, in the case of the microphone unit 11 shown in FIG. 1, since the gap G that operates as an acoustic capacity (reactance component) without the elastic acoustic resistance material 52 operates as an acoustic resistance, the gap Ga and the gap G Resonance is prevented from occurring.

  On the other hand, in the case of the microphone unit 11 shown in FIG. 2, since the gap G that operates as an acoustic mass (reactance component) operates as an acoustic resistance in the absence of the elastic acoustic resistance material 52, the gap Ga and the gap are again used. Resonance with the part G does not occur.

  Therefore, in the present invention, the elastic acoustic resistance material 52 arranged around the gap G can replace the reactance component of the gap G with the resistance component, thereby minimizing the reactance component and causing the microphone unit 11 to resonate. Occurrence can be avoided.

  In this case, the elastic acoustic resistance material 52 is disposed between the position where the thickness of the front mesh 32 is separated in the axial direction and the position immediately before the caulking portion 26, thereby minimizing the non-arranged volume in the gap portion G. The reactance component generated by the gap G can be minimized.

  According to the present invention, since the microphone unit 11 is configured as described above, it is possible to effectively avoid the occurrence of resonance and to stabilize the directivity frequency response near the resonance frequency.

  In addition, since the microphone unit 11 is configured so as to avoid the occurrence of resonance, it is not necessary to take measures against the influence of resonance for each actual product, and shift to mass production without varying the directional frequency response. Can do.

  Further, when the microphone unit 11 is formed with unidirectionality as shown in the illustrated example, a narrow directional microphone can be formed by being incorporated in an acoustic tube. Moreover, when the cutout portion 48b communicating with the gap portion G is provided on the printed circuit board 48, the microphone unit 11 can reduce the sound pressure difference between the front sound hole 24 side and the rear sound hole 48a side. Therefore, it is possible to form a narrow directional microphone with reduced wind noise when incorporated in an acoustic tube.

  In addition, since the elastic acoustic resistance material 52 can be disposed in close contact with the outer peripheral surface 42a side of the built-in unit 42 over the entire circumference of the gap G, individual components of the built-in unit 42 are allowed to idle in the radial direction. Positioning without any problem. For this reason, the built-in unit 42 can be fixed in position by aligning the axes of the individual constituent members, and can provide high-quality sensitivity and S / N ratio to the microphone unit 11.

The explanatory view showing the internal structure about an example of the present invention. Explanatory drawing which shows the internal structure about the other example of this invention. An explanatory view showing an example of the internal structure of a conventional condenser microphone unit. FIG. 4 is an equivalent circuit diagram showing the acoustic system element of the microphone unit shown in FIG. 3 in correspondence with each element of the electric circuit.

DESCRIPTION OF SYMBOLS 11 Condenser microphone unit 22 Case body 23 Bottom part 23a Inner bottom surface 24 Front sound hole 25 Opening part 26 Caulking part 27 Inner peripheral surface 32 Front mesh 42 Built-in unit 42a Outer peripheral surface 43 Diaphragm ring 44 Diaphragm 45 Spacer 46 Back pole Plate 46a Through-hole 47 Insulator seat 47a Through-hole 47b Air chamber 47c Circumferential recess 48 Printed circuit board 48a Rear sound hole 48b Notch 49 Impedance transducer 52 Elastic acoustic resistance material G Gap Ga gap P Sound path R Acoustic resistance material

Claims (3)

A case body having a bottomed cylindrical shape, a diaphragm ring and a diaphragm ring arranged on the bottom side of the case body, and an opening portion in the case body are sealed and caulked and fixed through a caulking portion. And a built-in unit comprising a combination of a plurality of constituent members that are easily formed in the case body, the built-in unit comprising an outer peripheral surface thereof and an inner periphery of the case body. In the condenser microphone unit formed by leaving a gap between the surface and the surface,
The gap between the position of the diaphragm ring separated from the thickness of the front mesh disposed on the inner bottom side of the case body and the position immediately before the caulking portion is generated by the gap. An elastic acoustic resistance material for minimizing the acoustic reactance component is densely arranged so as not to form a resonance circuit between the gap generated between the diaphragm ring and the front mesh and the gap. Capacitor microphone unit characterized by that. Condenser microphone unit according to claim 1, sound passage extending from the rear sound hole side to the vibration plate side is provided to the printed circuit board has.   3. The condenser microphone unit according to claim 2, wherein the printed circuit board is provided with a notch at a part of a peripheral edge thereof so as to allow the gap to communicate with the rear sound hole side.

Images