JPH0736640B2 - Electret condenser microphone - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an electret condenser microphone.

2. Description of the Related Art FIG. 8 is a sectional view of a conventional electret condenser microphone. In FIG. 8, 1 is a face cloth, 2 is a cylindrical metal case having a sound hole 2a at the center of the top surface, and 3 is a vibrating film holding member provided inside the top surface which constitutes the metal case. A film ring, 4 is a vibrating film made of an electret material having a metal layer formed on the surface by vapor deposition, 5 is a gap spacer, 6 is a fixed electrode, 7 is a concave insulator, and 8 is FE.
T and 8a are input leads, 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. The output lead 8b is fixed to the printed board 9 by the soldered portion 9a. Further, the fixed electrode 6, the insulator 7, the FET 8, and the printed board 9 are inserted into the metal case 2 as one amplifier block and fixed by the caulking portion 2b.

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

Problems to be Solved by the Invention In the electret condenser microphone configured as described above, the number of parts is large (9 in the case of FIG. 8).
In particular, the fixed electrode 6, the insulator 7, the FET 8, and the amplifier block portion of the printed circuit board 9 have as many as four parts, which is difficult to assemble and requires a lot of time, which inevitably leads to an increase in cost. Further, the large number of parts complicates automatic assembly, requires a large amount of equipment cost, and has drawbacks, which inevitably results in a decrease in operating rate. The present invention eliminates the above-mentioned drawbacks, simplifies the configuration and assembly by reducing the number of parts, reduces the equipment cost of the automatic assembly machine, improves the operating rate, is suitable for mass production, and is cost effective. It aims at providing a cheap electret condenser microphone.

Means for Solving the Problems In order to achieve the above object, the present invention provides a cylindrical metal case having a fixed surface on the top surface thereof, and a vibrating membrane facing the fixed electrode with a constant interval. .

Therefore, according to the present invention, it is not necessary to provide a special fixed electrode as in the prior art, and therefore, the number of parts can be reduced, so that the structure and the assembly can be simplified.

Embodiments The configuration of an embodiment 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 those in FIG. 8 are designated by the same reference numerals. 1 is different from FIG. 8 in that the fixed electrode 6 is not provided, the top surface of the metal case 2 serves as the fixed electrode 2b, and the vibrating membrane 4 is formed on the back air chamber 11 side. It is a point. Further, the input lead 8a of the FET 8 is sandwiched between the membrane ring 3 and the insulator 7 and is capable of conduction by contact or the like. In this example, FET8
Is a dual-side type, but the same is true when a single-side type is used as shown in FIG.

FIG. 2 illustrates the assembly of the amplifier block section in FIG. Here, 7a is a recess in which the input lead 8a is located. From FIG. 2, the number of parts of the amplifier block portion is reduced from the conventional four to three. Therefore, in the case of the present embodiment, the number of parts can be reduced to 8 as compared with 9 in the past.

In this embodiment, the film ring 3 and the metal case 2 need to be insulated. Therefore, there is also a method of press-fitting and fixing to the insulator 7 to fix the position of the membrane ring 3, but in this case, the vibrating membrane 4 may be distorted, which is not preferable. Therefore, it is desirable that the insertion portions of the film ring 3 and the insulator 7 have some play.

FIG. 3 shows a second embodiment of the present invention. In the case of FIG.
As shown in FIG. 4, an example is shown 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 only dropped into the metal case 2 and can be assembled more easily than in the case of FIG.

FIG. 5 shows a third embodiment of the present invention, and in the case of FIG. 5, a bank 17a having an inner taper is formed on the outer peripheral portion of the upper end of the concave insulator 17, and the film ring is formed by the bank 17a. The position of 3 is fixed. Reference numeral 17b denotes a housing portion for the FET 8 provided in the insulator 17, but as shown in FIG. 1 or FIG.
b is not necessary even if not provided.

FIG. 6 and FIG. 7 show the fourth and fifth embodiments. This is the case where one or a plurality of concave portions 2d or convex portions 2e are formed on the top surface of the metal case 32, and the capacitor gap 12 is constituted by these concave and convex portions, and since the gap spacer 5 is not required, the number of parts can be further reduced. It can be reduced, and in the case of FIGS. 6 and 7, it is possible to set 7 points.

In any of the embodiments of the present invention, not only can the number of parts be reduced, but since there is no fixed electrode, this plate thickness can make the overall height of the electret condenser microphone low. Further, if the total height is the same, the back air chamber can be made large, so that high sensitivity can be achieved. Therefore,
It can be said that it is also suitable for obtaining a low-profile, low-profile electret condenser microphone.

EFFECTS OF THE INVENTION As described above, according to the present invention, since the fixed electrode is constructed by utilizing the top surface of the metal case, the number of parts is reduced, the assembly is simplified, and the material cost can be reduced.
Also, the automatic assembly machine can be configured with a simple structure, which reduces equipment costs and improves the operating rate, making it suitable for mass production.
It has an effect that it can be used as an inexpensive electret condenser microphone.

In the case of the present invention, since the electret surface of the vibrating membrane is exposed to the outside air, it seems to be unfavorable in terms of reliability, but it has been confirmed that there is no great difference as a result of the reliability test.
For further improvement, if a drip-proof (waterproof) agent is used for the face cloth, the result is no different from the conventional one.

[Brief description of drawings]

FIG. 1 is a sectional view showing an electret condenser microphone according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram showing an assembling process of an amplifier block portion in FIG. 1, and FIG. 3 is a second embodiment of the present invention. FIG. 4 is a partially enlarged sectional view in FIG. 3, FIG. 5 is a sectional view showing a third embodiment, and FIG. 6 is a sectional view showing a fourth embodiment.
8 is a sectional view showing a fifth embodiment, FIG. 8 is a sectional view showing a conventional electret condenser microphone, and FIG. 9 is a schematic configuration diagram showing an assembling process of an amplifier block portion in FIG. 1 ... Face cloth, 2 ... Metal case, 3 ... Membrane ring, 4 ...
… Vibration membrane, 5 …… Gap spacer, 7 …… Insulator, 26
...... Fixed electrode.

Claims (3)

[Claims] 1. A cylindrical metal case having a top surface uses the top surface as a fixed electrode, and a vibrating membrane facing the top surface and having a constant interval, and an electrical contact with the fixed electrode via a conductive member. Electret condenser microphone equipped with an active element that performs. 2. The electret condenser microphone according to claim 1, wherein the inner surface of the cylindrical metal case is insulated. 3. A convex-concave portion is provided on the top surface of a cylindrical metal case as a means for holding the fixed electrode and the vibrating membrane at a constant interval. Electret condenser microphone.