JPH0134477Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an electret condenser microphone.

A conventional electret condenser microphone will be explained with reference to FIG. 1 is a face cloth, 2 is a case, 3 is a diaphragm ring, 4 is a diaphragm electret, 5 is a spacer, 6 is a back electrode, 7 is an insulator, 8 is a printed circuit board (hereinafter referred to as the board), 9 is an example. It is an electrical impedance conversion element (hereinafter referred to as FET) such as a field effect transistor. In this configuration, the FET 9 is inserted into the insulator 7, and the air chamber in the inserted part acoustically functions as a back air chamber.
If a pinhole is formed in the soldered part A of the output terminal 9a of the FET9, the low frequency will drop due to the characteristics.
There was a problem with negative effects. Also FET
In cases where the positioning of the back air chamber 9 is configured on the insulator 7 to facilitate assembly, the volume of the back air chamber tends to become small, which poses a problem that, as is well known, sensitivity tends to decrease.

In view of the above points, it is an object of the present invention to provide an electret condenser microphone that can obtain excellent characteristics by separating the housing part of the electrical impedance conversion element from the back air chamber.

That is, in order to achieve the above object, the present invention provides a housing part for an electrical impedance conversion element whose input part is coupled to the back electrode in a part of the insulator for holding the back electrode and forming the back air chamber. , and this housing section is separated from the back air chamber.

Embodiments of the present invention will be described below based on the drawings. FIG. 2 is a cross-sectional view showing one embodiment of the present invention, and the same components as those shown in FIG. In the embodiment shown in FIG. 2, the difference from the conventional structure is that the housing part for the FET 9 is provided almost in the center of the insulator 7, and the back air chamber 10 is provided on the outer periphery of the insulator 7, and each is separated. This is because the back electrode 6 is provided with a ventilation hole 11 that communicates with the back air chamber 10. Therefore, the housing section of FET9 is not involved in acoustics, so
Even if a pinhole is formed in the soldered portion A of the output terminal 9a, it will not affect the characteristics in any way. Further, the back air chamber 10 is formed in an annular shape outside the accommodating portion of the FET 9, and the internal volume can be increased, so that a decrease in sensitivity is not caused, and assembly can be easily automated. In addition, the back air chamber 10 is a FET
Those having circular cross sections may be provided at appropriate intervals in the circumferential direction on the same circumference concentrically with the accommodating portion 9.

FIG. 3 shows another embodiment, in which the FET 9 may be inserted into the insulator 7 from the back electrode 6 side.

In the above embodiment, an example was explained in which the back air chamber 10 was formed so as to open on the upper surface of the insulator 7, but the back air chamber 10 was formed so as to open on the lower surface of the insulator 7, and this A small hole may be formed in the insulator 7 to communicate the air chamber 10 with the hole of the back electrode 6.

Further, in the above embodiment, an example has been described in which the housing portion of the FET 9 is provided almost at the center of the insulator 7, but it goes without saying that the same effect can be obtained even if the housing portion is provided at the outer peripheral portion.

Further, in each of the above embodiments, even if there is some air leak between the housing part of the FET 9 and the back air chamber 10, there is no problem as long as it does not affect the characteristics.

As explained above, according to the electret condenser microphone according to the present invention, the storage part for the electrical impedance conversion element is separated from the back air chamber, and the ventilation hole communicating with the back air chamber is formed in the back electrode. When adjusting the sensitivity of frequency characteristics, it can be controlled simply by the diameter and number of vents, making it extremely easy to design the optimal frequency characteristics.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional electret condenser microphone, Fig. 2 is a sectional view of an electret condenser microphone in one embodiment of the present invention, and Fig. 3 is a sectional view of the main parts of an electret condenser microphone in another embodiment. FIG. 6...Back electrode, 7...Insulator, 9...Electric impedance conversion element, 10...Back air chamber, 11...
...vents.

Claims (1)

[Claims for Utility Model Registration] (1) An insulator for holding a back electrode, and housing of an electrical impedance converting element provided on a part of the insulator, the input part of which is coupled to the back electrode. a back air chamber provided on the outer periphery of the accommodating portion in the insulator separately from the accommodating portion, and a ventilation hole provided in the back electrode so as to communicate with the back air chamber. electret condenser microphone. (2) The electret condenser microphone according to claim 1, wherein the electric impedance conversion element is housed in the housing portion from the back electrode side or the opposite side.