JPS62213400A - Capacitor type microphone - Google Patents

Abstract

PURPOSE:To make the thickness of a spacer thinner and to obtain a high sensitivity in a wider band by constituting an inter-pole spacer of an outer peripheral spacer part surrounding a vibrating surface and its inner division spacer part, and making a diaphragm vibrate divisionally. CONSTITUTION:A microphone uses a metallic foil or a metallized film for the diaphragm 1, and is disposed facing a back pole 4 which possesses a large quantity of pores 3 over a spacer 2. The spacer 2 is provided with the outer peripheral spacer part 2a whose thickness hold constant the space between the diaphragm 1 and the back pole 4. In the area surrounded by the part 2a, the division spacer part 2b is provided in a position dividing the vibration area of the diaphragm 1 into two parts. Since the inter-pole discharge never occurs due to the part 2b even if the thickness of the spacer 2 is made far thinner than before, the sensitivity rises and an S/N is improved. The vibration area of the diaphragm 1 is bisected by the part 2b and the diaphragm 1 vibrates divisionally, so the limit of a high frequency band extends and the wider band can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a condenser type (including electret type or bank electret type) microphone.

[Summary of the invention]

In a microphone in which a diaphragm forming a capacitor and a fixed back electrode face each other via a spacer, the spacer is composed of an outer peripheral spacer part and a dividing spacer part inside the diaphragm, and the diaphragm substantially causes divided vibration. This increases the high-frequency limit of the response, and by preventing the diaphragm and back electrode from coming into contact with each other due to electrostatic attraction using the dividing spacer, the distance between the electrodes is reduced and sensitivity is increased. It is something.

[Conventional technology]

In order to increase the sensitivity of a capacitor type microphone (including electric left type or back electric left type), it is possible to increase the bias DC voltage between the diaphragm and the back plate that form the capacitor, or to increase the bias DC voltage between these plates. It is necessary to reduce the distance or increase the area of the diaphragm.

[Problem that the invention seeks to solve]

There are limits to increasing the bias voltage due to insulation problems and built-in power supply (battery) problems. Furthermore, when the distance between the electrode plates is reduced, the area of the diaphragm is increased, or the bias voltage is increased as described above, the electrostatic attractive force between the diaphragm (membrane) and the back electrode increases. - For this reason, it is necessary to increase the tension in the plane of the diaphragm or diaphragm so that the diaphragm does not come into contact with the back electrode, making it difficult to manufacture a microphone with a limited external shape.

Furthermore, if the area of the diaphragm is increased or the tension is increased, the sensitivity of high frequencies decreases, resulting in a problem that the band becomes narrower.

In view of these problems, it is an object of the present invention to provide a condenser microphone having a simple configuration, high sensitivity, and providing broadband frequency characteristics.

[Means for solving problems]

As shown in FIG. 1A, FIG. 2, or FIG. The spacer is composed of an outer spacer part 2a surrounding the outer periphery of the vibration surface and a splitting spacer part 2b arranged inside this outer spacer part so that the plate 1 causes split vibration. .

[Function] By generating split vibration, the high-frequency limit of the response-frequency characteristic increases. Furthermore, since interelectrode discharge is prevented by the presence of the dividing spacer portion, it is possible to make the spacer thinner and increase sensitivity.

〔Example〕

FIG. 1A is a sectional view showing the basic structure of a condenser microphone, and FIG. 1B is a plan view of a spacer between electrode plates. As is well known, this type of microphone has a diaphragm l.
spacer 2 using metal foil or metallized film.
The structure is such that it is placed opposite to a back electrode 4 (fixed side) having a large number of pores 3 in between. A bias DC voltage E is applied between the diaphragm 1 and the back electrode 4, and the change in potential of the back electrode 4 accompanying the vibration of the diaphragm 1 is extracted as a microphone output.

As shown in FIG. 1B, the spacer 2 includes an outer peripheral spacer portion 2a, and its thickness maintains a constant distance between the diaphragm 1 and the back electrode 4. A dividing spacer portion 2b is further provided inside the area surrounded by the outer peripheral spacer portion 2a.

In the example of FIG. 1B, the spacer portion 2b is continuous with the outer peripheral spacer portion 2a, and is formed at a position that approximately bisects the vibration region of the diaphragm. Such a spacer 2 can be made by punching or etching a piece of insulating film such as polyester, polyimide, or styrene.

Since there is a dividing spacer portion 2b, no interpolar discharge occurs even if the thickness of the spacer 2 is made much thinner than before. This substantially increases interelectrode capacitance and increases sensitivity. Furthermore, the S/N ratio improves by the amount that the sensitivity increases.

Further, the spacer 2 is sandwiched between the diaphragm 1 and the back electrode 4 by electrostatic attraction, and the outer peripheral spacer portion 2a and the dividing spacer portion 2b are in close contact with the diaphragm 1.

Therefore, the vibrating area of the diaphragm 1 is divided into two parts by the dividing spacer portion 2b, and the diaphragm 1 vibrates dividedly in each divided part. In other words, the stiffness of the diaphragm l increases as the height increases, and as a result, the high-frequency limit of the output frequency characteristic of the microphone increases, resulting in a wider band. Note that since a capacitor type microphone has good low-frequency characteristics in principle, even if the low-frequency characteristics deteriorate somewhat due to the divided vibration of the diaphragm 1, this can be electrically compensated for in the amplification system.

Since the spacer 2 is pressed between the diaphragm 1 and the back electrode 4 by electrostatic attraction, there is no need to fix the spacer 2 to the surface of the back electrode 4 with an adhesive. If necessary, it may be fixed with adhesive. The dividing spacer portion 2b is preferably formed at a position avoiding the pores 3 of the back electrode 4.

The present invention can also be applied to the electric left type microphone shown in FIG. 2 or 3, which is known as a condenser type microphone. In FIG. 2, an electret film with permanently fixed charges is used as the diaphragm 1, and the structure is such that it faces the back electrode 4 with a spacer 2 in between, as in FIG. 1A. No bias voltage needs to be applied. The structure shown in FIG. 3 is called a back electret type, in which an electret film 5 is fixed to the surface of a back electrode 4, and a metallized diaphragm 1 faces the metallized diaphragm 1 with a spacer 2 in between.

In the electric left type microphone shown in FIG. 2 or 3, the same effect as described above can be obtained by using a spacer as shown in FIG. 1B. Note that in the electret type or back electret type, when the interelectrode capacitance increases, the voltage division ratio with respect to the input capacitance of the FET input amplifier changes, resulting in increased sensitivity.

FIG. 4 shows various modifications of the spacer 2. A is an example in which the dividing spacer portion 2b is projected from one side of the outer peripheral spacer portion 2a to approximately the center of the vibration region, and B is an example in which a pair of dividing spacer portions 2b are projected from two opposing sides of the outer peripheral spacer portion 2a. This is an example. In either case, the vibration region surrounded by the outer peripheral spacer portion 2a is divided into approximately two parts, and divided vibration occurs in each part.

In FIG. 4C, the dividing spacer portion 2b is made into a rectangular shape surrounding a smaller area than the outer peripheral spacer portion 2a, and the spacer portion 2a and the outer peripheral portion 2a are connected by a connecting portion 2C. The vibration surface is divided into three parts: two peripheral parts and a central part. D is an example in which the vibration region is unevenly divided into two parts by one dividing spacer portion 2b. E is an example in which a diagonal dividing spacer portion 2b is provided so that a portion of the triangular corner is divided.

FIG. 4F shows an example in which a dividing spacer portion 2b surrounding a small rectangular region is provided inside the outer peripheral spacer portion 2a. In this example, since the outer peripheral spacer portion 2a and the dividing spacer portion 2b are not continuous, the dividing spacer portion 2b is adhesively fixed to the surface of the back electrode 4 during assembly. The vibration surface is divided into two parts, an inner region and an outer region.

Fig. 4G shows an example in which a dot-shaped dividing spacer portion 2b is provided, and although the vibration surface is not divided into two parts in terms of area, the diaphragm 1 causes divided vibration using the spacer portion 2b as a node, so This is a similar vibration plane division, and similar effects can be obtained.

Note that the outer shape of the diaphragm 1 may be round or polygonal in addition to the rectangular shape, and various division shapes of the spacer 2 can be considered depending on the outer shape of the diaphragm 1.

FIG. 5 shows the frequency characteristics of the microphone when the spacer shown in FIG.
Sensitivity is also improved. Approximately similar frequency characteristics can be obtained when the spacers 2 shown in FIG. 1B and FIGS. 4A to 4E and G are used.

〔Effect of the invention〕

As described above, in the present invention, the spacer 2 between the poles of the condenser microphone is constituted by the outer peripheral spacer portion 2a surrounding the vibration surface and the dividing spacer portion 2b inside thereof, so that the stiffness of the diaphragm 1 is locally increased. , the high-frequency limit of the response rises and wider band characteristics are obtained. In addition, the dividing spacer portion 2b prevents the diaphragm 1 from coming into contact with the back electrode 4 due to the electrostatic attraction between the electrodes and causing discharge, so the spacer thickness is made thinner and the distance between the electrodes is reduced. As a result, the capacitance between the electrodes can be increased, high sensitivity and high output can be obtained, and the S/N ratio can also be relatively improved.

[Brief explanation of drawings]

FIG. 1A is a sectional view of a main part of a condenser microphone according to an embodiment of the present invention, FIG. 1B is a plan view of a spacer, and FIGS. 2 and 3 are sectional views of a main part of a Nireto drift type microphone showing another embodiment , FIGS. 4A to 4G are plan views showing modified examples of the spacer, and FIG. 5 is a frequency characteristic diagram. In addition, in the symbols used in the drawings, 1-1----・-----1-----Vibration plate 2・----
---・-----Spacer 2a・---11-------Outer spacer part 2b・-----1-------------Dividing spacer part 3−−−−−−−−−−−−−−・−−−・Stomata 4・−・・−・−・−・−・−Back electrode 5−・−・−・・−−−− --...-It is an eletotore soto film.

Claims (1)

[Claims] A diaphragm forming a capacitor and a fixed back electrode are made to face each other via a spacer, and the spacer is arranged so that the diaphragm causes divided vibration, and an outer periphery spacer portion surrounding the outer periphery of the vibration surface, and this outer periphery spacer. A condenser microphone consisting of a dividing spacer section placed inside the section.