JPS61265000A - Electoret capacitor microphone - Google Patents

Abstract

PURPOSE:To decrease the number of components and thereby to simplify its assembling and reduce cost of materials by constituting a fixed electrode with a ceiling of a metal case. CONSTITUTION:The titled microphone has no fixed electrode and the ceiling of the metal case 2 functions as the fixed electrode 2, and the vibrating film 4 is constituted on the side of a rear air chamber 11. The input reed 8a of an FET 8 is inserted between a film ring 3 and an insulating body 7, and continuity is made possible by contacting and the like. The number of parts of an amplifier block part is decreased to three from conventional four, therefore the total number of parts becomes eight from conventional nine. The film ring 3 and the metal case 2 need to be insulated from each other. In this connection, such a method exists that the film ring 3 is press-fitted in an insulating material 7 for positioning and fixing, however, this method parts to invite distortion in the vibrating film 4, so is not desirable one. Therefore, the desirable is that there is a small clearance between the film ring 3 and the insulating material 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electret condenser microphone.

BACKGROUND OF THE INVENTION FIG. 8 is a sectional view of a conventional electret condenser microphone. In Fig. 8, 1 is a canvas, 2 is a cylindrical metal case having a sound hole 2a in the center of the top surface, and 3 is a membrane for holding a vibration membrane provided inside the top surface constituting the metal case. ring, 4 is a vibrating membrane made of electret material with a metal layer formed on its surface by vapor deposition, 5 is a gap spacer, 6 is a fixed electrode, 7 is a concave insulator, 8 is F
ET s 8a is an input lead, 8b is an output lead, 9 is a printed circuit board, 10 is a front air chamber, 11 is a back air chamber, and 12 is a capacitor gap. Note that the output lead 8b is fixed to the printed circuit board 9 by a soldered portion 9a.

Moreover, the fixed electrode 6, the insulator 7, the FET 8, and the printed circuit board 9 are inserted into the metal case 2 as one amplifier block, and fixed by the caulking part 2b.

FIG. 9 illustrates the assembly process of the amplifier block section.

Problems to be Solved by the Invention In an electret condenser microphone configured as described above, there are many parts (9 parts in the case of Fig. 8).
In particular, the amplifier block section, which includes the fixed electrode 6, insulator 7, FET 8, and printed circuit board 9, has as many as four parts, making assembly difficult and requiring a lot of time, which inevitably increases costs. In addition, the large number of parts makes automatic assembly complicated, requiring a large amount of equipment cost, and there are also some difficulties, which inevitably leads to a decrease in the operating rate. The present invention eliminates the above-mentioned drawbacks, reduces the number of parts, simplifies configuration and assembly, reduces equipment costs for automatic assembly machines, improves operating rate, and is suitable for mass production. The purpose is to provide an inexpensive electret condenser microphone.

Means for Solving the Problems In order to achieve the above object, the present invention uses a fixed electrode on the top surface of a cylindrical metal case, and a vibrating membrane is provided oppositely at a constant interval. .

Therefore, according to the present invention, there is no need to provide a special fixed electrode as in the conventional case, and the number of parts can therefore be reduced, so that the structure and assembly can be simplified.

EXAMPLE The configuration of an example of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention, and the same parts as in FIG. 8 are designated by the same numbers. The difference between FIG. 1 and FIG. 8 is that there is no fixed electrode 6, and there is no metal case 2.
The top surface serves as the fixed electrode 2b, and the vibrating membrane 4 is arranged on the back air chamber 11 side. Further, the input lead 8a of the FET 8 is sandwiched between the membrane ring 3 and the insulator 7 to enable conduction through contact or the like. In this embodiment, a dual-side type FET 8 is used, but a single-side type FET 8 as shown in FIG. 8 may be used.

FIG. 2 illustrates the assembly of the amplifier block section in FIG. 1. Here, 7a is a recess in which the input lead 8a is located. From FIG. 2, the number of parts in the amplifier block section has been reduced from four to three in the conventional system. Therefore, in the case of this embodiment, the number of parts was 9 in the past, but
It can be as low as 8 points.

In the case of this embodiment, the membrane ring 3 and the metal case 2 need to be insulated. Therefore, there is a method of fixing the position of the membrane ring 3 by press-fitting it into the insulator 7, but in this case, the vibration
This is not preferable because it may cause distortion in the image. Therefore, it is desirable that the membrane ring 3 and the insulator 7 be inserted into each other with some looseness.

FIG. 3 shows a second embodiment of the present invention, and in the case of FIG.
As shown in FIG. 4, this is an example in which an insulating layer 2C is formed on the inner surface of the metal case 2 by coating or the like to enable insulation between the membrane ring 3 and the metal case 2. In this case, the membrane ring 3 is attached to the metal case 2. 2, and the assembly can be made even easier than the case shown in FIG.

FIG. 5 shows a third embodiment of the present invention. In the case of FIG. 5, a boundary portion 17a having an inward taper is formed at the outer portion of the upper end of a concave insulator 17, and the boundary portion 17a is This is to fix the position of the membrane ring 3. 17b is an insulator 17
This is the accommodating part for FET 8 provided in Figure 1 or Figure 3.
As shown in the figure, the housing portion 17b does not need to be provided.

FIGS. 6 and 7 show fourth and fifth embodiments.

One or more recesses 2d on the top surface of the metal case 32
Alternatively, a convex portion 2e is formed and the capacitor gap 12 is configured by this concave and convex portion, and the gap spacer 5
Since the number of parts can be further reduced, the number of parts can be further reduced.
In the case of Fig. 7, it is possible to give 7 points.

In any of the embodiments of the present invention, not only can the number of parts be reduced, but also because there is no fixed electrode, the overall height of the electret condenser microphone can be reduced by this plate thickness. Furthermore, if the overall height is the same, the back air chamber can be made larger, and high sensitivity can be achieved. Therefore, it can be said that it is suitable for obtaining a thin electret condenser microphone with a low overall height.

Effects of the Invention As described above, according to the present invention, since the fixed electrode is constructed using the top surface of the metal case, the number of parts is reduced, assembly is simplified, and material costs can be reduced.

In addition, the automatic assembly machine has a simple configuration, which reduces equipment costs and improves operating rates, making it suitable for mass production.
It has the effect of being an inexpensive electret condenser microphone.

In the case of the present invention, the electret surface of the vibrating membrane is exposed to the outside air, which seems unfavorable in terms of reliability, but reliability tests have confirmed that there is no significant difference.
For further improvement, if a drip-proof (waterproofing) agent or the like is applied to the canvas, the result will be the same as before.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an electret condenser microphone according to an embodiment of the present invention, FIG.
The figure is a partially enlarged sectional view of FIG. 3, FIG. 5 is a sectional view showing the third embodiment, FIG. 6 is a sectional view showing the fourth embodiment, and FIG. 7 is a sectional view showing the fifth embodiment. Cross-sectional view, FIG. 8 is a cross-sectional view showing a conventional electret condenser microphone,
1st... canvas, 2... metal case, 3
...Membrane ring, 4...Vibration membrane, 5...
...Gap spacer, 7...Insulator, 2
6...Fixed electrode. Name of agent: Patent attorney Toshio Nakao and one other person Figure 1
/-Candy l2rIJ 3rd [ Figure 4 Figure 7 Figure 8 Figure 9

Claims (3)

[Claims] (1) An electret condenser microphone comprising a cylindrical metal case having a top surface, the top surface of which is a fixed electrode, and a vibrating membrane facing the top surface and provided at a constant interval. (2) The electret condenser microphone according to claim 1, wherein the inner surface of the cylindrical metal case is insulated. (3) Claim 1 or 2, characterized in that an uneven portion is provided on the top surface of the cylindrical metal case as a means for holding the fixed electrode and the vibrating membrane at a constant interval. electret condenser microphone.