JP2995240B2 - Condenser microphone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a condenser microphone having a low cutoff frequency characteristic adjusting function.

[0002]

2. Description of the Related Art In a conventional condenser microphone having a metal diaphragm, as shown in FIG. 2, an annular fixed ring 21 holding a peripheral portion of a metal diaphragm 4 is screwed to an outer peripheral surface of a push-up ring 22. In the hollow portion of the push-up ring 22, a back electrode mounting plate 23 made of an insulating material having a base end fixed to the center of the back electrode 3 is formed on the inner peripheral surface of the push-up ring 22. It is axially positioned on the step portion 24 via the annular spacer 5 and is fitted and fixed.

The front end surface of the back electrode 3 is drawn in from the plane including the front end edge of the push-up ring 22, and the gap between both surfaces is a minute gap of about 20 to 25 μm. Due to the relative displacement in the axial direction between the annular fixed ring 21 and the push-up ring 22 due to the relative rotation, an appropriate tension is applied to the metal diaphragm 4 with the leading edge of the push-up ring 22 as a fulcrum.

The back air chamber defined by the metal diaphragm 4, the push-up ring 22 and the back electrode mounting plate 23 is a push-up ring.
It communicates with the outside through a small-diameter vent hole 25 drilled in 22.

[0005] Since the back air chamber is in a sealed state, the metal diaphragm 4 is displaced by a pressure difference between the outside and the outside of the back air chamber due to a change in the outside air pressure or the like, thereby affecting the sensitivity to voice and changing the characteristics of the condenser microphone. . Therefore, a vent hole 25 is provided to give a time constant and make the pressure in the back air chamber equal to the external pressure. That is, vent hole 25
Is intended for low frequency cutoff. Therefore, according to the pressure difference between the inside and outside of the back air chamber, air is squeezed and circulated in the vent hole 25, but the low cutoff frequency characteristic of the condenser microphone is determined by the diameter of the vent hole 25. By adjusting the diameter of 25, a desired low-frequency cutoff frequency characteristic is given to the condenser microphone.

[0006]

In order to provide a desired low cut-off frequency characteristic to a condenser microphone by the above-mentioned conventional technique, it is necessary to make the vent hole 25 a predetermined diameter in drilling a hole. Very difficult for. Therefore, the diameter of the vent hole 25 is adjusted by inserting an appropriate minute diameter metal wire (tungsten wire) into the vent hole 25, that is, the low-frequency cutoff frequency characteristic is adjusted.
Therefore, the adjustment of the low cut-off frequency characteristic of the condenser microphone according to the related art is inefficient and the productivity is low. The present invention simplifies the adjustment of the low-frequency cutoff frequency characteristic in the condenser microphone.

[0007]

SUMMARY OF THE INVENTION A condenser microphone according to the present invention is provided with an annular body, a metal diaphragm stretched on a distal end surface of the annular body under tension, and mounted inside the annular body via an insulator. A back electrode whose surface is separated from the back of the metal diaphragm with a small gap, a terminal fitted into the inner peripheral surface of the annular body, forming a back air chamber between the back electrode and the insulator, and connected to the back electrode with a conductor A fixing screw member which is adjustably screwed to the inner peripheral surface of the annular main body so as to sandwich the terminal mounting plate between the terminal mounting plate to which the terminal mounting plate is attached and the engaging portion of the inner peripheral surface of the annular main body. A minute gap communicating with the back air chamber is formed on the outer peripheral surface of the mounting plate and the holding area of the terminal mounting plate.

[0008]

In the above-mentioned condenser microphone, the back air chamber between the back electrode / insulator and the terminal mounting plate has a minute gap on the outer peripheral surface of the terminal mounting plate and an engaging portion / fixing screw on the inner peripheral surface of the annular main body. It communicates with the outside through a minute gap in the terminal mounting plate sandwiching area between the rings, and in accordance with a pressure difference between the inside and outside of the back air chamber due to a change in air pressure, air is squeezed and circulated through the minute gap, With the time constant, there is no pressure difference between the outside and the inside of the back air chamber. That is, a low cut-off frequency characteristic is given to the condenser microphone.

The minute gap in the terminal mounting plate sandwiching area of the terminal mounting plate, that is, the ventilation diaphragm is adjusted by adjusting the rotation of the fixing screw ring, whereby the condenser microphone is adjusted to a desired low-frequency cutoff frequency characteristic. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A condenser microphone according to an embodiment of the present invention will be described with reference to the drawings. The vertical relationship in the following description is the vertical relationship in FIG. As shown in FIG. 1, an upper annular main body 1 of a condenser microphone
The annular insulator 2 and the cylindrical back electrode 3 are concentrically integrated. The inner peripheral surface of the upper annular main body 1 and the outer peripheral surface of the annular insulator 2 are in contact, and the inner peripheral surface of the annular insulator 2 is in contact with the outer peripheral surface of the back electrode 3. In the illustrated example, the small-diameter portion of the cylindrical back electrode 3 having the step portion 31 formed on the lower surface is in contact with the inner peripheral surface of the annular insulator 2, and the step portion 31 is in contact with the upper surface of the annular insulator 2. The outer peripheral surface of the annular insulator 2 lower than the annular main body 1 is in contact with the lower inner peripheral surface of the upper annular main body 1.

The integration of the upper annular body 1, the annular insulator 2, and the cylindrical back electrode 3 may be individually bonded,
Upper annular body 1 and cylindrical back electrode 3 arranged concentrically
The upper annular main body 1 and the cylindrical back electrode 3 are concentrically integrated with each other through an insulator by integrally forming the annular insulator 2 with a thermoplastic resin or a thermosetting resin between the two. Is more appropriate.

The distal end surface of the upper annular main body 1 and the distal end surface of the back electrode 3 are coplanar as reference surfaces, and an appropriate tension is applied to the distal end surface of the upper annular main body 1 in the radial direction. An annular spacer 5 having a predetermined thickness (20 to 25 μm) is interposed between the peripheral portion of the metal diaphragm 4 in the state and the peripheral portions of the upper annular main body 1, the annular spacer 5 and the metal diaphragm 4 are integrally welded. I have.

Thus, the front end face of the back electrode 3 is parallel to the metal diaphragm 4, and a small gap corresponding to the thickness of the annular spacer 5 is provided between the front end face of the back pole 3 and the back surface of the metal diaphragm 4. Is held.

Further, a terminal mounting plate 6 made of an insulating elastic body (for example, Teflon) is fitted to the intermediate inner peripheral surface of the lower annular main body 7 with a small gap, and a back gap is formed between the back electrode 3 and the annular insulator 2. Although an air chamber is formed, a step portion 11 and a screw portion 12 adjacent to the step portion 11 are formed on an intermediate inner peripheral surface of the lower annular main body 7,
The terminal mounting plate 6 is fixed to the fixing screw ring 7 screwed to the step portion 11 and the screw portion 12 with an appropriate minute gap therebetween. The minute gap on the outer peripheral surface of the terminal mounting plate 6 may be formed by the threaded surface of the thread portion 12.

The back pole 3 is penetrated by vent holes 32, 32 ° of minute diameter in the axial direction for damping adjustment, and the gap between the metal diaphragm 4 and the back pole 3 is formed by the back pole 3 and the terminal. It communicates with the back air chamber between the mounting plates 6. Since an appropriate number of ventilation holes 32 can be provided at appropriate positions, appropriate damping adjustment is easy. The terminal 8 attached to the terminal attachment plate 6 and the lower end surface of the back electrode 3 are connected by a conducting wire 9.
The terminal 8 is connected to an external amplifier by a conductor.

In manufacturing the microphone, the upper annular main body 1 and the lower annular main body 7 are welded and integrated at the time of assembly. If necessary, the surface of the metal diaphragm 4 and the upper end surface of the back electrode 3 are coated with a thin film of a water-repellent polymer material (for example, Parylene (trade name)) by chemical vapor deposition. This thin film fills the pinholes on the surface of the metal diaphragm 4 and prevents the occurrence of condensation on the surface of the metal diaphragm 4 even in the case of a sudden temperature change.

In the above-mentioned condenser microphone, if an electret film is formed on the upper end surface of the back electrode 3, an electret condenser microphone is formed. When an electret film is used instead of the metal diaphragm 4, a front electret condenser microphone is formed.

In the above condenser microphone,
The back air chamber has a minute gap between the outer peripheral surface of the terminal mounting plate 6 and the intermediate inner peripheral surface (screw surface) of the annular main body 1 and the upper and lower peripheral surfaces of the terminal mounting plate 6 and the step portion 11 of the annular main body 1 for fixing. It communicates with the outside through a minute gap with the screw ring 7, and in response to a pressure difference between the inside and outside of the back air chamber due to a change in air pressure or the like, air is squeezed and circulated through the minute gap, and the back air has a time constant. The pressure difference between the room and outside is eliminated. That is, a low cut-off frequency characteristic is given to the condenser microphone.

The minute gap between the peripheral upper and lower surfaces of the terminal mounting plate 6 and the step 11 of the annular main body 1 and the fixing screw ring 7, that is, the ventilation aperture, is adjusted by adjusting the rotation of the fixing screw ring 7. Thereby, the condenser microphone is adjusted to a desired low cutoff frequency characteristic.

[0020]

The adjustment of the low cut-off frequency characteristic of the condenser microphone according to the present invention is performed simply by adjusting the rotation of the fixing screw ring so that the terminal mounting plate is sandwiched between the engaging portion of the inner peripheral surface of the annular main body and the fixing screw ring. It is a very simple operation of adjusting the minute gap in the area.

[Brief description of the drawings]

FIG. 1 is a configuration sectional view of a condenser microphone according to an embodiment of the present invention.

FIG. 2 is a configuration sectional view of a condenser microphone according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper annular main body 2 Annular insulator 3 Back pole 11,31 step part 32 Vent hole 4 Metal diaphragm 5 Annular spacer 6 Terminal mounting plate 7 Lower annular main body 8 Terminal 9 Lead wire 10 Fixing screw ring 12 Screw part

Continued on the front page (72) Inventor Keiji Migami 1-1-16 Hakusan, Midori-ku, Yokohama-shi, Kanagawa Prefecture Ono Sokki Technical Center (72) Inventor Tadashi Ikeda 1-16, Hakusan, Midori-ku, Yokohama-shi, Kanagawa -1 Inside Ono Sokki Technical Center (72) Inventor Taku Yamamoto 1-16-1 Hakusan Midori-ku, Yokohama-shi, Kanagawa Prefecture Inside Ono Sokki Technical Center (72) Inventor Masanao Ohashi Yokohama, Kanagawa Prefecture 1-16-1 Hakusan, Midori-ku Ono Sokki Technical Center Co., Ltd. (56) References JP-A-60-217800 (JP, A) JP-A 64-18898 (JP, U) (58) Fields surveyed (Int.Cl. ⁶ , DB name) H04R 19/04 H04R 1/00 320

Claims (1)

(57) [Claims] 1. An annular main body, a metal diaphragm stretched on a distal end surface of the annular main body under tension, attached to the annular main body via an insulator, and the distal end surface is separated from the back surface of the metal diaphragm by a minute gap. The back pole is fitted into the inner peripheral surface of the annular main body, forms a back air chamber between the back pole and the terminal mounting plate on which the terminal connected to the back pole and the conductor is attached, and the inner peripheral surface of the annular main body. It is composed of a fixing screw member which is adjustably screwed to the inner peripheral surface of the annular main body so as to clamp the terminal mounting plate between the engaging portion and the outer peripheral surface of the terminal mounting plate and the holding area of the terminal mounting plate. A microphone with a minute gap leading to the air chamber.