JP2006165911A - Manufacturing method of condenser microphone unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a condenser microphone unit where the tension of the vibration plate can be adjusted with high accuracy as intended and the tension of the vibration plate can easily be adjusted. <P>SOLUTION: The vibration plate 1 of a vibration plate assembly 20 wherein the vibration plate 1 is fixed to a vibration plate support 2 is pressurized by compressed air, the tension of the vibration plate 1 is decreased by heating the vibration plate 1 while measuring the displacement of the vibration plate 1, and the pressurization and heating are stopped when the displacement of the vibration plate 1 reaches a prescribed value. The displacement of the vibration plate 1 can be carried out by measuring a static capacitance between the vibration plate and a fixed pole 30 arranged in opposition to the vibration plate. The vibration plate 1 is heated by irradiating the vibration plate 1 with the luminous flux from a light source 8. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a condenser microphone unit, and particularly has a feature in a tension adjustment method of a diaphragm used in the microphone unit.

  An example of a general condenser microphone unit is shown in FIG. In FIG. 2, the code | symbol 1 has shown the diaphragm-shaped diaphragm. The diaphragm 1 is made of, for example, a circular thin resin film, and a metal film such as gold is deposited on the resin film. The outer peripheral edge of the diaphragm 1 is fixed by adhering the vapor deposition surface side of the metal film to the ring-shaped diaphragm holder 2 in a state where a predetermined tension is applied to the diaphragm 1. A ring-shaped spacer 4 is in contact with the outer peripheral edge of the diaphragm 1 on the side opposite to the metal film deposition surface, and the outer peripheral edge of the disk-shaped fixed pole 3 is in contact with the spacer 4. Yes. Therefore, the spacer 4 is interposed between the diaphragm 1 and the fixed pole 3, and a gap g corresponding to the thickness of the spacer 4 is formed between the diaphragm 1 and the fixed pole 3. When the diaphragm 1 and the fixed pole 3 constitute a kind of capacitor and the diaphragm 1 receives a sound and vibrates, the capacitance between the diaphragm 1 and the fixed pole 3 changes according to the vibration. ing. The fixed pole 3 may be referred to as a back plate in relation to the diaphragm 1.

  The fixed pole 3 is supported by an electrically insulating support 5. The support body 5 is a flat dish-shaped member, and a step portion 51 is formed on the inner peripheral edge portion on the open end side, and the outer peripheral edge portion of the fixed pole 3 is fitted on the step portion 51, whereby the fixed pole 3 is formed. It is supported. A space 52 is formed between the fixed pole 3 and the support 5. Each member including the diaphragm 1, the diaphragm holder 2, the fixed pole 3, and the support 5 is incorporated in a unit case (not shown) to constitute a microphone unit of a primary sound pressure gradient condenser microphone.

  The tension of the diaphragm 1 in the primary sound pressure gradient condenser microphone affects the low frequency sound collection limit of the frequency response. FIG. 3 shows the difference in frequency response due to the tension of the diaphragm in the condenser microphone. In FIG. 3, the horizontal axis represents the frequency, and the vertical axis represents the output of the microphone. Curve A is appropriate if the diaphragm tension is relatively low, Curve B is too high, Curve C and D are too low, and the diaphragm is very close to the fixed pole by electrostatic attraction. The cases where the vibration region is extremely limited or are attracted to the fixed pole are shown. As can be seen from FIG. 3, when the diaphragm tension is relatively low, the low frequency sound collection limit of the frequency response is lowered, and the dynamic range is widened to obtain a high-performance condenser microphone. However, if the tension of the diaphragm is made too low in order to reduce the low-frequency sound collection limit sufficiently, the diaphragm is attracted to the fixed pole by the electrostatic attraction force due to the polarization voltage, and can function as a microphone. become unable. In other words, reducing the tension of the diaphragm to achieve high performance and setting the tension of the diaphragm high to ensure stability so that the diaphragm is not attracted to the fixed pole It becomes a conflicting relationship.

  As described above, the variation in the tension of the diaphragm causes a large variation in the lower limit of the frequency response and also causes a large variation in the stability due to the electrostatic attraction force. In particular, since a microphone used for studio recording or the like is required to have high performance, variations in the tension of the diaphragm greatly vary the performance, which becomes a serious problem. By the way, an inexpensive microphone unit whose contents are fixed by curling has a wide tolerance for performance variation and does not require high performance.Therefore, in order to cope with adsorption by the fixed electrode of the diaphragm, The tension is set high to ensure sufficient stability, and the low frequency sound collection limit is set to a relatively high frequency. In other words, an inexpensive microphone unit emphasizes stability at the expense of dynamic range.

  Thus, in order to obtain a high-performance condenser microphone, it is preferable to lower the tension of the diaphragm. Therefore, a method of manufacturing an electret condenser microphone having high sensitivity and stable acoustic characteristics by reducing the stiffness of the diaphragm in the condenser microphone has been proposed. In this manufacturing method, a diaphragm made of PET film is bonded to a diaphragm support ring with a predetermined tension to produce a diaphragm subassembly, and the diaphragm of the diaphragm subassembly is set to a secondary transition point. By performing the heat treatment at a temperature exceeding (eg, 200 ° C.), the stiffness of the vibrating membrane is reduced (eg, see Patent Document 1).

  Patent Document 1 describes that the diaphragm of the diaphragm sub-assembly is heat-treated, thereby reducing the stiffness of the diaphragm and improving the performance of the microphone. No specific technical means such as a control method or a stiffness control method is disclosed.

JP 2003-199196 A

  The present invention has been made in view of the above-described prior art, and is a condenser microphone unit that can adjust the tension of the diaphragm with high accuracy as intended and can easily adjust the tension of the diaphragm. It aims at providing the manufacturing method of.

The present invention is to pressurize the diaphragm of the diaphragm assembly formed by fixing the diaphragm to the diaphragm holder with compressed air, and heat the diaphragm while measuring the displacement of the diaphragm. The most important feature is that pressurization and heating are stopped when the tension of the diaphragm is reduced and the diaphragm reaches a predetermined displacement.
The displacement amount of the diaphragm can be measured by measuring an electrostatic capacity between the diaphragm and a fixed pole disposed to face the diaphragm.
The diaphragm can be heated by irradiating a light beam from a light source.

Since the diaphragm is pressurized by the compressed air, the tension of the diaphragm can be adjusted by adjusting the pressure of the compressed air, and the adjustment is easy.
Since the diaphragm tension is adjusted while measuring the displacement of the diaphragm due to pressure, it can be adjusted accurately to achieve the target tension, and the diaphragm tension can be adjusted for each diaphragm assembly. Can be adjusted to be optimal.
Since the diaphragm is heated while the diaphragm is pressurized with compressed air, a decrease in the tension of the diaphragm is promoted, and the tension of the diaphragm can be adjusted efficiently. There is also an advantage that the lowered tension of the diaphragm is difficult to return to the original state.

  Hereinafter, an embodiment of a method of manufacturing a condenser microphone unit according to the present invention will be described with reference to FIG.

  In FIG. 1, reference numeral 20 denotes a diaphragm assembly (the diaphragm assembly 1) including the diaphragm 1 described in the example of the condenser microphone unit shown in FIG. 2 and the diaphragm holder 2 to which the peripheral portion of the diaphragm 1 is fixed by adhesion or the like. (Diaphragm assembly). The diaphragm assembly 20 is attached to the open end of the pressure vessel 26 whose one end side (the upper end side in FIG. 1) is open, and the open end of the pressure vessel 26 is closed by the diaphragm assembly 20. A fixed pole 30 is disposed in the pressure vessel 26 so as to face the diaphragm 1 of the diaphragm assembly 20 with a predetermined interval. The fixed pole 30 corresponds to the fixed pole 3 described with reference to FIG. 2, and forms a kind of capacitor between the fixed pole 30 and the diaphragm 1. The diaphragm 1 and the fixed pole 30 are connected to the capacitance meter 6, and the capacitance between the fixed pole 30 and the diaphragm 1 is measured. Since the capacitance between the fixed pole 30 and the diaphragm 1 is inversely proportional to the square of the distance between the fixed pole 30 and the diaphragm 1, the capacitance is fixed by the capacitance measured by the capacitance meter 6. The distance between the pole 30 and the diaphragm 1 can be measured, and further, the displacement of the diaphragm 1 can be measured by the variation of the measured value.

  The pressure vessel 26 is supplied with compressed air from the compressed air supply path 22. By supplying compressed air to the pressure vessel 26 whose open end is closed by the vibration plate assembly 20, the vibration plate 1 of the vibration plate assembly 20 is pressurized from the inside of the pressure vessel 26, and the vibration plate 1 is outside. It is pushed out toward. This pressurization reduces the tension of the diaphragm 1. A pressure regulator 24 is disposed in the compressed air supply path 22. The pressure regulator 24 adjusts the pressure of the compressed air while measuring the displacement amount of the diaphragm 1 with the capacitance meter 6. When the displacement amount of the diaphragm 1 reaches a predetermined displacement amount, the supply of compressed air is stopped.

  The light source 8 is disposed so as to face the open end of the pressure vessel 26 and thus face the outer surface of the vibration plate 1 of the vibration plate assembly 20 attached to the open end. The light source 8 functions as a heat source for applying heat by irradiating the diaphragm 1 with a light beam. For example, a halogen lamp is used so that the amount of heat that can sufficiently heat the diaphragm 1 can be generated. Use. A reflector 9 having a parabolic parabolic cross section is disposed behind a light source 8 such as a halogen lamp, and the light flux from the light source 8 is condensed on the diaphragm 1 by the reflector 9. The range in which light is condensed on the diaphragm 1 is arbitrary, and may be the entire diaphragm 1 or a part of the diaphragm 1. As described above, the light source 8 is turned on while the compressed air is supplied from the compressed air supply path 22 to heat the diaphragm 1. The diaphragm 1 is heated and at the same time supplied with compressed air, thereby promoting a decrease in tension.

With the configuration described above, the tension of the diaphragm 1 is adjusted to be a predetermined tension. The adjustment method is as follows.
In producing the diaphragm assembly 20, the diaphragm 1 is set so that the tension of the diaphragm 1 is higher than the target tension. The diaphragm assembly 20 is attached to the open end of the pressure vessel 26 to close the open end. While reading the capacitance between the diaphragm 1 and the fixed electrode 30 with the capacitance meter 6, the light source 8 is turned on to heat the diaphragm 1, and simultaneously compressed air is supplied from the compressed air supply path 22. The compressed air is gradually adjusted from a low pressure to a high pressure while adjusting the pressure by the pressure regulator 24. During this time, the measurement value of the capacitance meter 6 is read, and when the predetermined reading value is reached, the lighting of the light source 8 is stopped.

  As described above, since the tension of the diaphragm 1 is set higher than the target tension in advance, the diaphragm 1 is close to the fixed pole 30 at the beginning of the adjustment, and is measured by the capacitance meter 6. The value of the capacitance to be applied is a high value. As the pressure applied by the compressed air increases, the diaphragm 1 swells outward, the distance from the fixed electrode 30 increases, and the capacitance value measured by the capacitance meter 6 decreases. When the capacitance value becomes a predetermined value, that is, when the pressure of the compressed air applied to the diaphragm 1 becomes an appropriate pressure, more specifically, when the diaphragm 1 becomes an appropriate displacement amount. The light source 8 is turned off, heating is stopped, and the diaphragm 1 is cooled. Although supply of compressed air may be stopped simultaneously with the stop of heating, the above-described appropriate pressure may be maintained until the diaphragm 1 is cooled.

Note that the timing of starting pressurization and heating need not be the same. Heating may be started after pressurization is started, or conversely, the diaphragm 1 is heated in advance, and then pressurization is performed. May start.
The fixed electrode 30 is assembled to the pressure vessel 26 and may be a metal plate or a net-like member.
The purpose of measuring the capacitance between the diaphragm 1 and the fixed pole 30 by the capacitance meter 6 is to measure the amount of displacement of the diaphragm 1 with respect to the fixed pole 30. A measuring device other than the capacitance meter 6 may be used as long as it can directly or indirectly be measured. However, if the capacitance meter 6 is used, the displacement amount of the diaphragm 1 can be measured relatively easily.

It is a conceptual diagram which shows the Example of the manufacturing method of the condenser microphone unit concerning this invention. It is a longitudinal section showing a general example of a condenser microphone unit. It is a graph which shows the difference in the frequency response by the difference in the tension | tensile_strength of the diaphragm of a condenser microphone unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Diaphragm 2 Diaphragm holder 6 Capacitance meter 8 Light source as heat source 9 Reflector 20 Diaphragm assembly 24 Pressure regulator 30 Fixed pole

Claims (8)

  The diaphragm of the diaphragm assembly formed by adhering the diaphragm to the diaphragm holder is pressurized with compressed air, and the diaphragm is heated while measuring the displacement of the diaphragm. And the pressurization and heating are stopped when the vibration plate reaches a predetermined displacement amount.   The method of manufacturing a condenser microphone unit according to claim 1, wherein the measurement of the displacement amount of the diaphragm is performed by measuring an electrostatic capacitance between the diaphragm and a fixed pole disposed to face the diaphragm.   2. The method of manufacturing a condenser microphone unit according to claim 1, wherein the diaphragm is heated by irradiating a light beam from a light source.   4. The method of manufacturing a condenser microphone unit according to claim 3, wherein the light source is a halogen lamp.   4. The method of manufacturing a condenser microphone unit according to claim 3, wherein the light beam from the light source is reflected by a reflecting mirror and condensed on the diaphragm.   A diaphragm assembly is mounted on the open end of the pressure vessel having an open end to close the open end, and a fixed pole is disposed in the pressure vessel so as to face the diaphragm of the diaphragm assembly. The method of manufacturing a condenser microphone unit according to claim 1, wherein compressed air is supplied to the diaphragm to pressurize the diaphragm.   2. The method of manufacturing a condenser microphone unit according to claim 1, wherein a pressure regulator is disposed in the compressed air supply path.   The diaphragm assembly is manufactured by setting the tension of the diaphragm to be higher than the target tension, and the tension of the diaphragm is lowered to the target tension by pressurization and overheating of the diaphragm. 2. A method for manufacturing a condenser microphone unit according to 1.

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