JP2006203749A - Electrostatic type electroacoustic transducer, condenser microphone using the same, and manufacturing method of electrostatic type electroacoustic transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an electrostatic type electroacoustic transducer for avoiding the occurrence of deformation and the positional deviation of a fixed pole plate and a fixing ring for configuring a fixed pole by eliminating the need for heating and cooling in a processing step of the fixed pole, enhancing processing efficiency, and improving sensitivity by decreasing ineffective static capacitance, and to obtain a condenser microphone employing the transducer and a manufacturing method of the electrostatic type electroacoustic transducer. <P>SOLUTION: In the electrostatic type electroacoustic transducer including the fixed pole 30 and a diaphragm arranged opposite to the fixed pole 30 at an interval therefrom and applying a polarization voltage to either of the diaphragm and the fixed pole 30, the fixed pole 30 includes: the fixed pole plate 31; the fixing ring 32 located at the side of an outer circumference of the fixed pole plate 31; and an insulation part 33 interposed between the fixed pole plate 31 and the fixing ring 32 and coupling them integrally, and the insulation part 33 is made of an ultraviolet ray curing resin. The condenser microphone uses the electrostatic type electroacoustic transducer for its microphone unit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrostatic electroacoustic transducer capable of rationalizing a manufacturing process and reducing deformation and displacement of a member, a condenser microphone using the same, and a method of manufacturing an electrostatic electroacoustic transducer. In particular, it is characterized by the fixed pole of the electrostatic electroacoustic transducer.

  There is a condenser microphone as a device, instrument or tool using an electrostatic electroacoustic transducer. The electrostatic electroacoustic transducer has a fixed pole in which a fixed pole plate and a fixed ring are integrated, and a diaphragm arranged to face the fixed pole with a gap, and vibrates according to sound waves. The change in the gap when the plate vibrates is converted into an electrical signal. The condenser microphone unit applies a polarization voltage to either the diaphragm or the fixed pole of the electrostatic electroacoustic transducer, and changes the capacitance generated by the change in the gap between the diaphragm and the fixed pole. Output as a change in. This output voltage corresponds to the sound wave that strikes the diaphragm, and is thus subjected to electroacoustic conversion. In the condenser microphone, the electrostatic electroacoustic transducer constitutes a condenser microphone unit. Since this condenser microphone unit converts the sound wave received by the diaphragm into an electric signal as a change in capacitance and outputs it, it has a high impedance. Therefore, an impedance converter having an active element such as an FET (field effect transistor) is connected to the output side of the condenser microphone unit.

  Capacitance is generated between the fixed electrode and the diaphragm of the electrostatic electroacoustic transducer. The electrostatic capacity is changed by the displacement of the diaphragm and the diaphragm is displaced. There is an invalid capacitance that does not change. The reactive capacitance also includes stray capacitance that does not contribute to electroacoustic conversion. FIG. 4 is an equivalent circuit of these capacitances, in which an effective capacitance is connected in series to the output of the electrostatic electroacoustic transducer 1 composed of a fixed pole and a diaphragm, and ineffective in parallel to this series connection. Capacitance is connected. Therefore, if the values of the effective capacitance and the invalid capacitance are the same, the output converted by the electroacoustic conversion unit 1 is reduced to half. That is, since the sensitivity is halved, it is preferable to make the invalid capacitance as small as possible.

  As a prior art for reducing the reactive capacitance, a condenser microphone is known which has a stray capacitance reduced by forming a spacer with a synthetic resin material having a plurality of closed cells, that is, a material having a low relative dielectric constant. (For example, refer to Patent Document 1). Further, in the electret condenser microphone in which a back electrode substrate having an electret layer formed on a back electrode and a vibration film unit having a vibration film fixed to a support frame are laminated via a spacer, the back electrode substrate is an insulating substrate. A back electrode, an electret layer, and an acoustic hole are formed on the top, and at least a part of the acoustic hole is provided outside the formation region of the back electrode, thereby generating stray capacitance and loss capacity. A condenser microphone for preventing this is known (see, for example, Patent Document 2).

  The effective capacitance and the invalid capacitance will be described more specifically with reference to the drawings. In FIG. 5, reference numeral 2 denotes a disk-shaped fixed pole that forms part of the electrostatic electroacoustic transducer, and reference numeral 3 denotes a diaphragm that forms part of the electrostatic electroacoustic transducer. The diaphragm 3 is disposed to face one side of the fixed pole 2, but in order to maintain a gap 6 having a predetermined width between the diaphragm 3 and the fixed pole 2, the diaphragm 3 is disposed between the diaphragm 3 and the fixed pole 2. The spacer 4 is interposed between the two. In other words, the gap 6 having the same width as the thickness dimension of the spacer 4 is formed. The spacer 4 is a ring-shaped member having the same outer diameter as that of the fixed pole 2. The diaphragm 3 is a flat surface in which an outer peripheral edge of the surface opposite to the surface facing the spacer 4 is attached to the diaphragm ring 5 with an appropriate tension applied thereto. The width of the diaphragm ring 5 in the radial direction is the same as the width of the spacer 4 in the radial direction, and the diaphragm ring 5 is overlapped and fixed to the spacer 4 with the diaphragm 3 interposed therebetween. Therefore, the fixed pole 2, the spacer 4, the diaphragm 3, and the diaphragm ring 5 are stacked in this order and are fixed together. An appropriate number of through-holes are formed in the fixed pole 2 so that the flow of air generated when the diaphragm 3 vibrates smoothly so that the diaphragm 3 that receives the sound wave can vibrate faithfully to the sound wave. Has been.

  As a material of the diaphragm 3, for example, a metal foil is used, or a plastic film in which a metal is deposited by a vacuum deposition method or the like is used. As said metal foil, materials, such as titanium, nickel, nickel alloy, are used. Materials such as gold, nickel, and nickel alloys are used as the metal formed by the above evaporation, and materials such as PET (polyethylene terephthalate), PPS (polyphenylene sulfite), and PEN (polyethylene naphthalate) are used as the plastic film. Is used.

  A metal film formed on the metal foil or the plastic film is sandwiched between the diaphragm 3 and the fixed pole 2 so as to be mechanically fixed with an appropriate interval maintained. As shown in FIG. 5B, the effective capacitance is a capacitance generated when the range of the diameter b in which the diaphragm 3 can vibrate is opposed to the fixed pole 2. Since the outer peripheral edge portion indicated by the width b of the diaphragm 3 which is restrained by the spacer 4 and the diaphragm ring 5 cannot vibrate even when receiving a sound wave, the capacitance generated by facing the fixed pole 2 is ineffective electrostatic. Capacity. As described above, in order to improve the sensitivity of the microphone, it is necessary to increase the effective capacitance. For this purpose, the gap 6 is reduced by reducing the distance between the diaphragm 3 and the fixed pole 2. is necessary. Further, when the diaphragm 3 receives a sound wave and vibrates, if the diaphragm 3 comes into contact with the fixed pole 2, problems such as deterioration of performance as a microphone and generation of noise due to discharge occur. Therefore, the diaphragm 3 and the fixed pole Both facing surfaces need to be flat so that the surfaces facing 2 do not contact each other. The diaphragm 3 is kept flat by being attached to the diaphragm ring 5 with appropriate tension as described above. In order to make the surface of the fixed pole 2 facing the diaphragm 3 flat, it is necessary to perform surface polishing.

  As described above, the fixed pole 2 has a portion that contributes as an effective capacitance and a portion that becomes an invalid capacitance. Therefore, it is necessary to divide the fixed pole 2 electrically into two parts, that is, a part that contributes as an effective capacitance and a part that becomes an invalid capacitance. In the example shown in FIG. 6, the fixed pole 2 includes a fixed pole plate 21, a fixed ring 22 positioned on the outer periphery of the fixed pole plate 21, and interposed between the fixed pole plate 21 and the fixed ring 22. It has the insulation part 23 electrically insulated and combined. Since the fixed electrode plate 21 and the fixed ring 22 need to be mechanically firmly coupled, a peripheral groove having a V-shaped cross section is formed on the outer peripheral surface of the fixed electrode plate 21 and the inner peripheral surface of the fixed ring 22. A thermoplastic plastic, for example, polycarbonate (PC), is injected into a ring-shaped gap formed by facing the inner and outer peripheral grooves and solidified. This thermoplastic plastic constitutes the insulating portion 23. The fixed pole 2 manufactured in this way is subjected to a surface polishing process to increase the flatness of at least the surface facing the diaphragm 3, and then the diaphragm 3 is interposed with the spacer 4 as described above. It is fixed at an appropriate interval.

  The processing steps for insulating and coupling the fixed plate 21 and the fixed ring 22 are as follows. The fixed electrode plate 21 and the fixed ring 22 are manufactured by an appropriate processing method such as cutting or pressing, and then the fixed electrode plate 21 and the fixed ring 22 are temporarily fixed at appropriate positions using a jig or the like. The molten plastic material is poured into a ring-shaped gap formed between 21 and the fixing ring 22 and cooled to solidify. In order to maintain good adhesion between the fixed electrode plate 21 and the fixed ring 22, the fixed electrode plate 21 and the fixed ring 22 and a jig for temporarily fixing them are also adapted to the temperature of the plastic material. Heat and cool.

  However, in the step of insulating and coupling the fixed plate 21 and the fixed ring 22 as described above, the fixed plate 21, the fixed ring 22, The insulating part 23 and the jig expand and contract according to their respective latent expansion coefficients. Accordingly, there is a problem that the fixed electrode plate 21 and the fixed ring 22 are likely to be deformed and displaced. Moreover, since heating and cooling require time, there is also a problem that processing efficiency is poor.

Japanese Utility Model Publication No. 6-34399 JP 2003-125495 A

  The present invention has been made in order to solve such a conventional problem, and has a structure and a manufacturing process of a fixed pole manufactured by integrating a fixed pole plate and a fixed ring through an insulating portion. By devising it, heating and cooling in the machining process are not required, so that deformation and misalignment of the fixed pole plate and fixing ring constituting the fixed pole can be eliminated, and processing efficiency can be increased. Thus, it is an object of the present invention to provide an electrostatic electroacoustic transducer capable of increasing the sensitivity by reducing the ineffective capacitance, a condenser microphone using the same, and a method for manufacturing the electrostatic electroacoustic transducer.

  The present invention relates to an electrostatic electroacoustic transducer having a fixed pole and a diaphragm disposed opposite to the fixed pole with a gap, and applying a polarization voltage to either the diaphragm or the fixed pole. The fixed pole includes a fixed pole plate, a fixed ring located on the outer peripheral side of the fixed pole plate, and an insulating portion that is interposed between the fixed pole plate and the fixed ring and integrally couples them. The insulating part is characterized by being an ultraviolet curable resin.

  The fixed pole includes a fixed pole plate, a fixed ring located on the outer peripheral side of the fixed pole plate, and an insulating portion that is interposed between the fixed pole plate and the fixed ring and integrally couples them. Since the insulating portion is made of an ultraviolet curable resin, in the process of manufacturing the fixed electrode, the ultraviolet curable resin may be irradiated with ultraviolet rays to solidify the resin, and heating and cooling steps are unnecessary. Therefore, the fixed electrode plate and the fixing ring are not deformed or displaced by heating and cooling, and the adhesion between the constant electrode plate and the fixing ring is good. The time required for heating and cooling is also unnecessary, and the time required for producing the fixed electrode can be shortened.

Embodiments of an electrostatic electroacoustic transducer according to the present invention, a condenser microphone using the same, and a method for manufacturing the electrostatic electroacoustic transducer will be described below with reference to the drawings.
1 and 2, reference numeral 30 denotes a disk-shaped fixed pole that constitutes a part of the electrostatic electroacoustic transducer. A diaphragm is disposed opposite to the fixed pole 30 with an appropriate gap. Since the structure of the diaphragm is the same as the example of the electrostatic electroacoustic transducer described with reference to FIG. The depiction of the diaphragm is omitted in FIG. The diaphragm is arranged to face one side of the fixed pole 30. In order to maintain a gap having a predetermined width between the diaphragm and the fixed pole 30, a spacer is interposed between the diaphragm and the fixed pole 30. In other words, a gap having the same width as the thickness dimension of the spacer is formed between the diaphragm and the fixed pole 30.

  The fixed electrode 30 is interposed between the fixed electrode plate 31, the fixed ring 32 positioned on the outer periphery of the fixed electrode plate 31, and the fixed electrode plate 31 and the fixed ring 32. An insulating part 33 is provided. Since the fixed electrode plate 31 and the fixed ring 32 need to be mechanically firmly coupled, a circumferential groove having a V-shaped cross section is formed on the outer peripheral surface of the fixed electrode plate 31 and the inner peripheral surface of the fixed ring 32. Resin is applied and solidified in a ring-shaped gap formed by the inner and outer circumferential grooves facing each other, and this resin constitutes the insulating portion 33. The fixed electrode 30 thus manufactured is subjected to a surface polishing process to increase the flatness of at least the surface facing the diaphragm, and then the diaphragm is appropriately disposed with a spacer as described above. Fixed at intervals. An ultraviolet curable resin is used as the resin constituting the insulating portion 33.

  An example of the manufacturing process of the fixed electrode 30 is shown in FIG. Hereinafter, an example of a manufacturing process of the fixed electrode 30 will be described with reference to FIGS. 1 to 3. The fixed electrode plate 31 and the fixing ring 32 are positioned and set on the jig 40 and temporarily fixed. The jig 40 has a pin 42 for positioning the fixed electrode plate 31. When the diaphragm facing the fixed electrode plate 31 receives a sound wave and vibrates, air smoothly enters and exits the space between the fixed electrode plate 31 and the diaphragm so that the vibration of the diaphragm is smoothly performed. Thus, a plurality of through holes are formed. The fixed electrode plate 31 is positioned by fitting the pin 42 into a through hole 34 formed in the center of the fixed electrode plate 31 among these through holes. The upper surface of the jig 40 is also depressed, and the fixed electrode plate 31 and the fixed ring 32 fall into the depressed portion. The peripheral wall 41 of the depressed portion has the same diameter as the outer peripheral surface of the fixing ring 32, and the fixing ring 32 is positioned by dropping the fixing ring 32 along the surface of the peripheral wall 41. . In this way, the fixed ring 32 is positioned, and the fixed electrode plate 31 is positioned by the pin 42, whereby the relative position between the fixed electrode plate 31 and the fixed ring 32 is also automatically determined. In this way, the fixed electrode plate 31 and the fixing ring 32 are temporarily fixed to the jig 40. In addition, you may add a holding means etc. as needed so that the fixed pole plate 31 and the fixed ring 32 may not move.

  In the temporarily fixed state, an ultraviolet curable resin is applied to the ring-shaped gap generated between the outer peripheral surface of the fixed electrode plate 31 and the inner peripheral surface of the fixed ring 32. In this example, “3041N” manufactured by ThreeBond Co., Ltd. was used as an example of the ultraviolet curable resin. Since the fixed electrode plate 31 and the fixed ring 32 need to be mechanically firmly coupled, a circumferential groove having a V-shaped cross section is formed on the outer peripheral surface of the fixed electrode plate 31 and the inner peripheral surface of the fixed ring 32. An ultraviolet curable resin is applied to a ring-shaped gap formed so that the inner and outer circumferential grooves face each other, and the entire gap including the circumferential groove is filled with the ultraviolet curable resin. Next, the ultraviolet curable resin is irradiated with ultraviolet rays (UV) to cure the ultraviolet curable resin, thereby forming the insulating portion 33. The insulating part 33 electrically insulates the fixed electrode plate 31 and the fixed ring 32 and mechanically and firmly couples the fixed electrode plate 31 and the fixed ring 32. Since the fixed pole assembly is produced in this manner, the fixed pole assembly is removed from the jig 40 and subjected to a planar polishing step of the fixed pole assembly. In the planar polishing process, at least the surface facing the diaphragm is polished so as to be smooth with high precision so that there is no unevenness. Thus, the manufacturing process of the fixed electrode 30 is completed.

  A diaphragm is fixed to the completed fixed pole 30 via a spacer on one surface side of the fixed ring 32. The structure of the spacer and the diaphragm may be the same as the structure of the conventional example described with reference to FIGS. 5 and 6, and corresponds to the thickness of the spacer between the diaphragm and the fixed electrode plate 31 of the fixed electrode 30. The predetermined gap is formed. When a polarization voltage is applied to one of the diaphragm and the fixed electrode 30 and the diaphragm receives and vibrates a sound wave, the distance between the diaphragm and the fixed electrode plate 31 of the fixed electrode 30 changes, and the capacitance is increased. It changes and is converted into an electrical signal corresponding to the sound wave. Therefore, the components including the fixed pole 30 and the diaphragm constitute an electrostatic electroacoustic transducer.

  According to the electrostatic electroacoustic transducer, the fixed electrode 30 includes the fixed electrode plate 31, the fixed ring 32 positioned on the outer peripheral side of the fixed electrode plate 31, and the fixed electrode plate 31 and the fixed ring 32. And the insulating portion 33 is an ultraviolet curable resin, and in the manufacturing process of the fixed electrode 30, the ultraviolet curable resin is irradiated with ultraviolet rays. It only needs to be cured and does not need to be heated. Therefore, there is no need for cooling. Therefore, there is no temperature variation due to heating and cooling, and there is no deformation or misalignment of the fixed electrode plate 31 and the fixing ring 32 due to temperature variation, and a highly accurate fixed electrode 30 can be obtained. If the accuracy of the fixed pole 30 can be increased, even if the distance between the fixed pole 30 and the diaphragm is narrowed, the two do not come into contact with each other, and the sensitivity can be increased. The fixed pole 30 includes a fixed pole plate 31 and a fixed ring 32. Since the fixed pole plate 31 and the fixed ring 32 are electrically separated by an insulating portion 33, only the portion of the fixed pole plate 31 is a diaphragm. Therefore, it is possible to make a portion that generates electrostatic capacitance, and it is possible to greatly reduce the invalid electrostatic capacitance, and it is possible to increase sensitivity from this point.

  The electrostatic electroacoustic transducer configured as described above can be used as a microphone unit of a condenser microphone. A condenser microphone can be configured by incorporating the electrostatic electroacoustic transducer in the microphone case as a condenser microphone unit and incorporating an impedance converter, a connector, and the like. Since the electrostatic electroacoustic transducer according to the above embodiment can increase the sensitivity as described above, the condenser microphone using this as a microphone unit can also increase the sensitivity.

It is a longitudinal cross-sectional view which shows the example of the principal part of the electrostatic electroacoustic transducer concerning this invention, and the example of the jig used at the time of manufacture. It is a top view which shows the example of the principal part of the said electrostatic electroacoustic transducer. It is process drawing which shows the example of the manufacturing process of the principal part of the said electrostatic electroacoustic transducer. It is an equivalent circuit diagram which shows distribution of the electrostatic capacitance in a general electrostatic electroacoustic transducer. The example of the principal part of the conventional electrostatic electroacoustic transducer is shown, (a) is an exploded sectional view, (b) is a sectional view. The other example of the principal part of the conventional electrostatic electroacoustic transducer is shown, (a) is an exploded sectional view, (b) is a sectional view.

Explanation of symbols

30 Fixed Electrode 31 Fixed Electrode Plate 32 Fixed Ring 33 Insulating Part 40 Jig

Claims (5)

An electrostatic electroacoustic transducer having a fixed pole and a diaphragm disposed opposite to the fixed pole with a gap, and applying a polarization voltage to either the diaphragm or the fixed pole,
The fixed pole includes a fixed pole plate, a fixed ring located on the outer peripheral side of the fixed pole plate, and an insulating portion that is interposed between the fixed pole plate and the fixed ring and integrally couples them. Become
The electrostatic electroacoustic transducer according to claim 1, wherein the insulating part is an ultraviolet curable resin.   The electrostatic electricity according to claim 1, wherein grooves are formed in the outer periphery of the fixed electrode plate and the inner periphery of the fixed ring, and both the grooves are filled with an insulating portion, and the fixed electrode plate and the fixed ring are integrally coupled. Acoustic transducer.   The static plate according to claim 1, wherein the diaphragm is fixed to the fixing ring with a spacer interposed therebetween, and a surface capable of vibrating the diaphragm is opposed to the fixed electrode plate with a gap corresponding to the thickness of the spacer. Electric electroacoustic transducer. A fixed pole having a fixed pole plate, a fixed ring positioned on the outer peripheral side of the fixed pole plate, and an insulating portion that is interposed between the fixed pole plate and the fixed ring and integrally couples them; A method of manufacturing an electrostatic electroacoustic transducer having a diaphragm disposed opposite to each other with a gap between the electrodes, and applying a polarization voltage to either the diaphragm or the fixed pole,
Position and temporarily fix the fixed electrode plate and fixing ring,
Apply UV curable resin between the fixed plate and the fixed ring,
This ultraviolet curable resin is irradiated with ultraviolet rays and cured to form an insulating portion, and a fixed electrode plate and a fixed ring are integrally bonded to produce a fixed electrode,
A method of manufacturing an electrostatic electroacoustic transducer, wherein a diaphragm is disposed opposite to the fixed pole. A condenser microphone in which the electrostatic electroacoustic transducer according to claim 1 is incorporated as a condenser microphone unit.

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