JPH053600A - Condenser microphone - Google Patents

Abstract

PURPOSE:To simplify the adjustment of a low-pass shielding frequency characteristic in the condenser microphone. CONSTITUTION:This condenser microphone consists of a toroidal main body 1, a metal diaphragm 4 extended over the leading surface of the toroidal main body, back pole 3 installed through an isolator 2 to the toroidal main body and the leading surface of which is separated by the back surface of the metal diaphragm and the fine space, and a screw member 10 embedded on the toroidal main body inner peripheral surface, forming an exhaust room between the back pole and the isolator, and engaged freely adjustably in the toroidal main body inner peripheral surface holding a terminal mounting board between a terminal mounting board 6 and an engagement part 11 of the toroidal main body inner peripheral surface to which a terminal 8 is connected by the back pole and a leading wire 9. A small space leading to the exhaust room is formed in the outer peripheral surface of the terminal mounting board and the fitting area of the terminal mounting board. The small space, that is, low-pass shielding frequency characteristic in a terminal mounting board holding area of the terminal mounting board is adjusted by the rotation adjustment of the fixed screw member.

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 fixing ring 21 holding the peripheral edge of the metal diaphragm 4 is screwed onto the 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 and having the base end of the back electrode 3 fixed to the center is formed on the inner peripheral surface of the push-up ring 22. The stepped portion 24 is positioned in the axial direction through the annular spacer 5 and fitted and fixed.

The tip surface of the back electrode 3 is pulled inward from the plane including the tip edge of the push-up ring 22, and the gap between both surfaces is a minute gap of about 20 to 25 μm. Appropriate tension is applied to the metal diaphragm 4 with the tip edge of the push-up ring 22 as a fulcrum by relative displacement in the axial direction between the annular fixed ring 21 and the push-up ring 22 due to relative rotation therebetween.

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 is communicated with the outside through a vent hole 25 having a minute diameter formed in 22.

Since the back air chamber is in a sealed state, the metal diaphragm 4 is displaced by a pressure difference between the inside and outside of the back air chamber due to a change in atmospheric pressure and the like, sensitivity to sound is influenced, and characteristics of the condenser microphone are changed. .. Therefore, the vent hole 25 is provided to make the pressure in the back air chamber equal to the external pressure with a time constant. That is, the 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, the condenser microphone is given the desired low cutoff frequency characteristics.

[0006]

When the desired low cutoff frequency characteristic is given to the condenser microphone by the above-mentioned conventional technique, it is necessary to make the vent hole 15 a predetermined diameter in drilling, because the diameter is very small. Very difficult to do. Therefore, an appropriate fine metal wire (tungsten wire) is inserted into the vent hole 25 to adjust the diameter of the vent hole 25, that is, the low cutoff frequency characteristic.
Therefore, adjusting the low cutoff frequency characteristic of the condenser microphone according to the conventional technique is inefficient and poor in productivity. The present invention simplifies the adjustment of low cutoff frequency characteristics in a condenser microphone.

[0007]

SUMMARY OF THE INVENTION A condenser microphone according to the present invention includes an annular body, a metal diaphragm which is tensioned and stretched on the distal end surface of the annular body, and is mounted in the annular body via an insulator to provide a distal end. A terminal whose surface is separated from the back surface of the metal diaphragm by a small gap and is fitted to the inner peripheral surface of the annular body to form a back air chamber between the back electrode and the insulator, and which is connected to the back electrode by a conductor. A terminal mounting plate to which is attached and a fixing screw member adjustably screwed to the inner peripheral surface of the annular body so as to sandwich the terminal mounting plate between the terminal mounting plate and the engaging portion of the inner peripheral surface of the annular body. A minute gap communicating with the back air chamber is formed in the outer peripheral surface of the mounting plate and the sandwiching region of the terminal mounting plate.

[0008]

In the above condenser microphone, the back air chamber between the back electrode / insulator and the terminal mounting plate has a small gap on the outer peripheral surface of the terminal mounting plate, an engaging portion on the inner peripheral surface of the annular body, and a fixing screw. It communicates with the outside through a minute gap in the terminal mounting plate sandwiching area between the rings, and according to the pressure difference between the inside and outside of the back air chamber due to changes in atmospheric pressure, air circulates after being squeezed in the minute gap. With the time constant, the pressure difference inside and outside the back air disappears. That is, the condenser microphone is provided with a low cutoff frequency characteristic.

Then, the minute gap in the terminal mounting plate holding region of the terminal mounting plate, that is, the ventilation diaphragm, is adjusted by adjusting the rotation of the fixing screw ring, and thereby the condenser microphone is adjusted to a desired low cutoff frequency characteristic. ..

[0010]

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, the upper annular body 1 of the condenser microphone
The annular insulator 2 and the cylindrical back electrode 3 are concentrically integrated with each other. The inner peripheral surface of the upper annular body 1 is in contact with the outer peripheral surface of the annular insulator 2, 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 which is lower than the annular main body 1 is in contact with the lower inner peripheral surface of the upper annular body 1.

The upper annular body 1, the annular insulator 2 and the cylindrical back electrode 3 may be integrally bonded to each other, but they may be bonded separately.
The upper annular body 1 and the cylindrical back electrode 3 arranged concentrically
The ring-shaped insulator 2 is integrally molded with a thermoplastic resin or a thermosetting resin between the upper ring-shaped body 1 and the cylindrical back electrode 3 so as to be concentrically integrated via the insulator. Is more appropriate.

The tip surface of the upper annular body 1 and the tip surface of the back electrode 3 are arranged on the same plane as a reference plane, and an appropriate radial tension is applied to the tip surface of the upper annular body 1. An annular spacer 5 having a predetermined thickness (20 to 25 μm) is interposed between the peripheral portion of the metal diaphragm 4 and the peripheral portion of the upper annular body 1, the annular spacer 5 and the peripheral portion of the metal diaphragm 4 which are integrally welded. There is.

Thus, the tip surface of the back electrode 3 and the metal diaphragm 4 are parallel to each other, and a minute gap corresponding to the thickness of the annular spacer 5 is provided between the tip surface of the back electrode 3 and the back surface of the metal diaphragm 4. Is held.

Further, a terminal mounting plate 6 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 minute gap, and is provided between the back electrode 3 and the annular insulator 2 in the back. Although the air chamber is formed, a step portion 11 and a thread portion 12 adjacent to the step portion 11 are formed on the intermediate inner peripheral surface of the lower annular main body 7,
The terminal mounting plate 6 is fixed by being sandwiched by a fixing screw ring 7 screwed to the step portion 11 and the thread portion 12 with an appropriate minute gap. The minute gap on the outer peripheral surface of the terminal mounting plate 6 may be formed by the screw surface of the thread portion 12.

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

In manufacturing the microphone, the upper annular body 1 and the lower annular body 7 are welded together at the time of assembling. 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. The thin film fills the pinholes on the surface of the metal diaphragm 4 and prevents dew condensation on the surface of the metal diaphragm 4 even in the case of a sudden temperature change.

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

In the above condenser microphone,
The back air chamber is for fixing a small 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 stepped portion 11 of the annular main body 1. It communicates with the outside through a minute gap with the screw ring 7, and according to the pressure difference between the inside and outside of the back air chamber due to changes in atmospheric pressure, air is squeezed in the minute gap and circulates. There is no pressure difference between indoor and outdoor. That is, the condenser microphone is provided with a low cutoff frequency characteristic.

A minute gap between the upper and lower surfaces of the peripheral edge of the terminal mounting plate 6 and the stepped portion 11 of the annular main body 1 and the fixing screw ring 7, that is, a ventilation throttle is adjusted by rotating the fixing screw ring 7. Thereby, the condenser microphone is adjusted to a desired low cutoff frequency characteristic.

[0020]

The adjustment of the low cutoff frequency characteristic of the condenser microphone according to the present invention is performed by sandwiching the terminal mounting plate between the engaging portion of the inner peripheral surface of the annular body and the fixing screw ring by simply adjusting the rotation of the fixing screw ring. A very simple operation of adjusting a minute gap in the area is sufficient.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view of a configuration of a conventional condenser microphone.

[Explanation of symbols]

 1 Upper annular body 2 Annular insulator 3 Back electrode 11,31 Step portion 32 Vent hole 4 Metal diaphragm 5 Annular spacer 6 Terminal mounting plate 7 Lower annular body 8 Terminal 9 Conductor wire 10 Fixing screw ring 12 Thread part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiji Mikami 1-16-1 Shirayama, Midori-ku, Yokohama-shi, Kanagawa Ono Sokki Technical Center (72) Inventor Tadashi Ikeda 1 Shirayama, Midori-ku, Yokohama-shi, Kanagawa -16-1 Inside the Ono Sokki Technical Center (72) Inventor Taku Yamamoto 1-16-1 Shirayama, Midori-ku, Yokohama-shi, Kanagawa (72) Inside the Ono Sokki Technical Center (72) Inventor Masahisa Ohashi Yokohama, Kanagawa 1-16-1 Hakusan, Midori-ku Ono Sokki Technical Center Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. An annular body, a metal diaphragm which is tensioned and stretched on the tip end surface of the annular body, and a metal diaphragm attached inside the annular body via an insulator. A terminal mounting plate fitted with a back electrode, which is separated from the back surface with a small gap, on the inner peripheral surface of the annular body, forms a back air chamber between the back electrode and a terminal connected to the back electrode by a conductor, and It is composed of a fixing screw member that is adjustably screwed to the inner peripheral surface of the annular body so as to sandwich the terminal mounting plate with the engaging portion of the inner peripheral surface of the annular body. Microphone with a small gap that communicates with the back chamber in the pinching area of the plate