JP4139731B2 - Adjusting tension of diaphragm for condenser microphone - Google Patents

Description

【００２４】
【発明の効果】
以上説明したように、本発明によれば、振動板の中央部分をスポット的に多点状に加熱することにより、振動板の張力を支持リングに張設された後においても下げる方向に調整することができるため、張力が高すぎる不良品を良品として救済でき、全体として製品の歩留まり率の向上が図れる。
【図面の簡単な説明】
【図１】本発明の実施形態を示す模式図。
【図２】本発明の実施例で行った振動板の共振周波数測定方法を示す説明図。
【図３】コンデンサマイクユニットを示す模式的な分解断面図。
【図４】上記コンデンサマイクユニットに用いられる振動板の作製状態を示す模式的な斜視図。
【符号の説明】
１０ 振動板
１０Ｍ マザーフィルム
１１ 支持リング
２０ 固定極
３０ スペーサリング
１００ レーザー照射機
１１０ 昇圧トランス
１２０ 交流電圧発生器
１３０ 共振周波数測定用のマイクロホン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for adjusting the tension of a diaphragm for a condenser microphone, and more particularly to a technique for adjusting the tension of a diaphragm while being stretched on a support ring.
[0002]
[Prior art]
As shown in a schematic exploded cross-sectional view in FIG. 3, the condenser microphone includes a condenser microphone unit in which a diaphragm 10 and a fixed electrode (back electrode) 20 are arranged to face each other via a spacer ring 30. The diaphragm 10 is incorporated in the condenser microphone unit while being stretched on a support ring (diaphragm ring) 11.
[0003]
Usually, the diaphragm 10 is made of a synthetic resin film that can be vibrated by sound waves, and a thin film having a metal vapor-deposited film on one side thereof. Among condenser microphones, those that operate in a sound pressure gradient type are vibrations. The lower limit of the frequency response is governed by the tension of the plate 10.
[0004]
That is, as the tension of the diaphragm 10 is lower, the lower limit is extended to the lower frequency side. However, if the tension of the diaphragm 10 is too low, the diaphragm 10 is fixed by the electric attractive force due to the polarization voltage. In the worst case, the diaphragm 10 comes into contact with the fixed electrode 20.
[0005]
In the contacted state, the stiffness of the diaphragm 10 becomes high, so that the low frequency limit becomes the higher frequency, causing problems such as sensitivity reduction and noise generation. Therefore, the tension of the diaphragm 10 needs to be set to an optimum value.
[0006]
With reference to FIG. 4, a method of adjusting the tension of the diaphragm generally performed in the past will be described. For this, a cylindrical base B made of, for example, a glass material having a smooth upper end surface is used.
[0007]
On the base B, a mother film 10M having a size that allows the diaphragm 10 to be multifaceted is placed, and a weight W is hung around the mother film 10M to apply a predetermined tension to the mother film 10M. Instead of the weight W, a spring or a screw tightening mechanism may be used.
[0008]
A support ring 11 used as an actual unit component is attached to the mother film 10M to which tension is applied in this way with an adhesive such as an epoxy, and the adhesive is solidified. The diaphragm 10 is cut out in a state of being stretched on the support ring 11 and incorporated in the condenser microphone unit.
[0009]
[Problems to be solved by the invention]
Since the tension of the diaphragm 10 affects the performance of the condenser microphone, this tensioning operation is carefully performed, but the tension of each diaphragm 10 still varies. The main causes are the following (1) to (4).
[0010]
(1) Variation due to the cutting position from the mother film 10M. For example, even when a load is evenly applied to the mother film 10M with the weight W, the tension may be different between the central portion and the peripheral portion.
(2) Variation due to scratches on the mother film 10M.
(3) Partial variation due to thermal history during deposition of a metal vapor deposition film.
(4) Variation due to displacement when the support ring 11 is attached.
[0011]
Due to such various causes, a diaphragm that exceeds an appropriate tension range as a capacitor microphone unit may occur. Conventionally, the defective diaphragm has to be discarded, and only the support ring is collected and recycled.
[0012]
Therefore, an object of the present invention is to make it possible to adjust the tension of the diaphragm even after it is stretched on the support ring, to remedy a defective product as a non-defective product and to improve the product yield.
[0013]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a synthetic resin film that is vibrated by sound waves having a metal vapor-deposited film formed on one surface, and a fixed electrode and a predetermined electrode in a state of being stretched on a support ring. In the tension adjusting method for the condenser microphone diaphragm that adjusts the tension of the diaphragm arranged oppositely with a gap, a laser irradiator is used as a heating means , and the other diaphragm of the diaphragm stretched on the support ring is used. The center part of the surface is irradiated with laser light at two or more places by the laser irradiator, and the center part of the diaphragm is heated in a spot-like manner .
[0014]
By heating the central portion of the diaphragm in a spot-like manner, the tension of the diaphragm can be reduced as a whole. Further, by using a laser irradiator as a heating means, heating in a short time is possible.
[0015]
According to the present invention, it is possible to adjust a diaphragm whose tension has deviated to a higher level from the good product reference range to a tension within the good product reference range. Although some tensions are too low in the actual production process, the tension variation is normally distributed, so the average tension value is deliberately produced as a higher shift within the non-defective standard range, and the tension is low. The overall yield can be improved by keeping the rate of occurrence of too much low and by adjusting the tension of too high to an appropriate tension according to the present invention.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 schematically shows an embodiment of the present invention. In the present invention, the diaphragm 10 is partially heated in order to adjust the tension of the diaphragm 10 stretched on the support ring 11. In addition, since it is difficult to perform fine tension adjustment by heating the entire surface, the present invention does not include heating the entire surface of the diaphragm 10.
[0017]
The diaphragm 10 targeted by the present invention is a state in which a synthetic resin film (for example, PPS) that vibrates by sound waves is used as a base material and is stretched from the mother film 10M to the support ring 11 by the method described above with reference to FIG. It may have been cut out with. A diaphragm that is cut out from one mother film 10M with a large diameter is also included in the subject of the present invention.
[0018]
The heating here is heating at a temperature at which the diaphragm 10 is not burned out. The surface on the heating side is the surface opposite to the surface on which the metal vapor deposition film is formed. The heating means, Ru laser irradiation apparatus 100 is suitable der capable heated in a short time.
[0019]
The heating portion of the vibration plate 10, in order to decrease the overall tension in the vibration rotation plate 10, the central portion of the diaphragm 10 to spot, yet it is preferable to heat the multi-point shape.
[0020]
【Example】
Four samples 1 to 4 are prepared by stretching a diaphragm made of PPS (polyphenylene sulfide) with a film thickness of 2 μm and an outer diameter of 15 mm and having a metal vapor deposition film on one side of the support ring. Resonant frequencies f _{0 of} 1 to 4 were measured by the method shown in FIG.
That is, the diaphragm 10 and the fixed pole 20 are opposed to each other with a predetermined interval, and the AC voltage generator 120 is connected between the diaphragm 10 and the fixed pole 20 via the step-up transformer 110. The output voltage was swept from 500 Hz to 2 kHz to drive the diaphragm 10 as a speaker, and the generated sound wave was collected by the microphone 130 to analyze the frequency. As a result, the resonance frequency f ₀ of each of the samples 1 to 4 was the following value.
Sample 1 994 Hz
Sample 2 ... 1016Hz
Sample 3 ... 1059Hz
Sample 4 ... 1062 Hz
[0021]
Next, using a laser irradiator (output 60 mW), a laser beam of 785 nm was irradiated with a spot diameter of 0.5 mm and an irradiation time of 0.2 seconds per part, and each vibrating membrane of Samples 1 to 4 was partially Heated. All of the heating points are the central part of the diaphragm. Then, to measure the resonance frequency f ₀ of each sample 1-4 by the methods described above after laser irradiation (after heating).
[0022]
[Example 1]
For sample 1, only one central portion was irradiated with laser light. The resonance frequency _{f 0} after laser irradiation is 987Hz, the resonance frequency is lowered 7Hz than before laser irradiation.
[Example 2]
Sample 2 was irradiated with laser light so as not to overlap each other at six locations in the central portion. The resonance frequency _{f 0} after laser irradiation is 985Hz, the resonance frequency is lowered 31Hz than before laser irradiation.
Example 3
For sample 3, first, laser light was irradiated to one place in the central portion as the first time. Next, laser light is irradiated to different positions in the central part as the second time, and the irradiation places are made into a total of two places. Further, as the third time, the laser light is irradiated to three positions different from the previous two places in the central part. Irradiation was performed, and a total of five irradiation locations were used.
The resonance frequency f ₀ after the first laser irradiation is 1048 Hz, the resonance frequency f ₀ after the second laser irradiation is 1043 Hz, and the resonance frequency f ₀ after the third laser irradiation is 1030 Hz, respectively, before laser irradiation. Compared to 11 Hz, 16 Hz, and 29 Hz.
Example 4
For sample 4, first, laser light was irradiated to one place in the central portion for the first time. Next, as the second time, laser light was irradiated to different positions in the central portion, and a total of two irradiation locations were obtained.
The resonance frequency f ₀ after the first laser irradiation was 1055 Hz, and the resonance frequency f ₀ after the second laser irradiation was 1045 Hz, which was 7 Hz and 17 Hz lower than before the laser irradiation, respectively.
[0023]
The resonance frequency f ₀ of the tension the diaphragm of the diaphragm is correlated, the resonance frequency f ₀ even lower with the tension decreases. It was confirmed that the diaphragm can be finely adjusted in the direction of decreasing the tension by partially heating the diaphragm from Examples 1-4. For reference, the results of the above examples are summarized in the following table.
[Table 1]

[0024]
【The invention's effect】
As described above, according to the present invention, the central portion of the diaphragm is heated in a spot-like manner so that the tension of the diaphragm is adjusted to be lowered even after the diaphragm is stretched on the support ring. Therefore, a defective product whose tension is too high can be remedied as a non-defective product, and the yield rate of the product can be improved as a whole.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a method for measuring a resonance frequency of a diaphragm performed in an embodiment of the present invention.
FIG. 3 is a schematic exploded cross-sectional view showing a capacitor microphone unit.
FIG. 4 is a schematic perspective view showing a production state of a diaphragm used in the condenser microphone unit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Diaphragm 10M Mother film 11 Support ring 20 Fixed pole 30 Spacer ring 100 Laser irradiation machine 110 Step-up transformer 120 AC voltage generator 130 Resonance frequency measurement microphone

Claims (1)

A synthetic resin film that is vibrated by sound waves having a metal vapor-deposited film formed on one surface, and a diaphragm disposed opposite to the fixed pole in a state of being stretched on a support ring with a predetermined interval In the tension adjustment method of the diaphragm for condenser microphone that adjusts the tension,
Using a laser irradiator as a heating means, the central portion of the other surface of the diaphragm stretched on the support ring is irradiated with laser light at two or more locations with the laser irradiator, and the diaphragm A method for adjusting the tension of a diaphragm for a condenser microphone, characterized in that the central portion of the microphone is spot- heated in a multipoint manner.

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