WO1982000745A1

WO1982000745A1 - Back plate for condenser microphone and structure thereof

Info

Publication number: WO1982000745A1
Application number: PCT/JP1981/000047
Authority: WO
Inventors: Co Ltd Primo
Original assignee: Kishi K
Priority date: 1980-08-21
Filing date: 1981-03-06
Publication date: 1982-03-04
Also published as: JPS5739700A

Abstract

A back plate, and the structure thereof, used for a stationary electrode of an electrostatic converter for a condenser microphone. The effective surface (7) of the back plate (4) is devoid of holes and is not flat but defines a hyperboloid of revolution, which surface is either convex or concave or a composite of these shapes. Further, the peripheral edge surface (9) of the back plate (4) is inclined into a tapered state, and is engaged with the triangular cutouts (11a) of a plurality of retaining hooks (11) projecting from an insulating retainer (10), thereby to retain the back plate, and the retainer (10) is fixedly engaged with an intermediate cylinder (12) forming a part of a microphone. The air between the electrodes moves around the peripheral edge surface (9) of the back plate (4) to thus reach a back chamber (6) behind the back plate (4).

Description

Akira

Name of the invention

Pack plate of condenser microphone mouth phone and its components

The present invention relates to a condenser microphone and, more particularly, to a pack plate used for a fixed electrode of an electrostatic converter in such a microphone and a structure thereof.

Background 'technology

A condenser microphone is an electroacoustic element that converts a sound wave into an electric waveform using an electrostatic converter composed of a fixed electrode and a movable electrode. Fig. 1 shows a longitudinal cross-sectional view of a model that has been widely used in the past as such a microphone mouthpiece. In FIG. 1, the vibrating membrane 1z extends on a ring frame to form a vibrating plate (movable electrode), and faces a pack plate (fixed electrode) 4 'having a flat surface with a narrow gap 3' therebetween. You. Thereby, a capacitance C is formed between the vibrating membrane 1 'and the pack plate. Further, a DC voltage is applied to the pack plate via a high resistance (not shown), and electric charges are charged between both electrodes. Alternatively, a permanent charge is held between both electrodes by interposing an electret. When the vibrating membrane having an effective area S is vibrated by the addition of the signal sound pressure member P o, a small change in the capacitance G occurs, and a signal electromotive force is induced in the pack plate 4. This signal is transmitted to an in-vehicle device such as a field-effect transistor.

_ΟΙ.ίΡΙ- After being amplified by the dance conversion amplifier 8z, it is sent to the external zero point as an output signal voltage.

The thickness of the gap 5 ′ between the active membrane 1 ′ and the pack plate 4 is generally about 20 to 30 so that the capacitance C is formed, while the gap in the gap is thin. Air layer force Shows the viscoelasticity of the fluid and controls the vibration of diaphragm 1. Normally, the pack plate is provided with a plurality of through holes 5 ′ so that the gap 3 ′ communicates with the back room 0 ′. When the vibrating membrane 1 ′ vibrates, the air molecules in the gap 3 ′ flow in the radial direction as shown by the arrows, and escape from the through-hole 5 ′ to the back chamber 0 ′, and then again into the gap. Breathing is performed. At this time, since the air flowing through the narrow gap 3 'has viscous resistance rA and elastic CA, this is the vibrating membrane as shown in the equivalent circuit diagram of the condenser microphone vibration system in Fig. 2. An effective mass m _{Q of} 1 'and an elastic Co by extension tension are added in series to control the velocity u of the vibrating membrane. There is a radiation impedance outside this, but it is excluded here. Among the above, the 'viscous resistance rA is a force that has the effect of suppressing the resonance of the vibrating membrane 1' and flattening the characteristics.This is unfavorable because excessively lowering the sensitivity of the microphones . Also, elastic CA has the effect of increasing the resonance frequency of the diaphragm and extending the band, but if it is excessive, it produces a high-pitched beak and causes mechanical vibration of the diaphragm. This is also harmful, such as increased dance and reduced sensitivity. Therefore, when making a condenser microphone, it is necessary to determine the optimal conditions for elastic CA and viscous resistance rA. Basically important.

Such a conventional condenser microphone horn pack prep is composed entirely of a flat surface, and is provided with a groove, a through-hole, a closed hole, or the like, and is appropriately connected to the diaphragm. The air flow in the gap is adjusted. However, in recent years, as microphones have become increasingly smaller, the above-mentioned conventional adjustment means are no longer applicable. Also, in the case of a so-called pack electret microphone in which an electret film is applied to a pack plate, when the through hole 5 ′ is processed, the sagging or separation of the film or separation of the film occurs. Paris tends to occur, causing variations in sensitivity and characteristics. Furthermore, in the case of a conventional microphone having a general structure in which a gap ring is inserted to set a gap between the diaphragm and the pack plate, a large amount of stray capacity is generated. However, this is added in parallel to the original main capacitance, causing sensitivity loss, degrading the ratio, and reducing the performance, such as increasing nonlinear distortion.

Disclosure of the invention

According to the present invention, instead of making the effective surface a flat surface and forming a hole in the surface, the rotating surface is made a rotating curved surface and is made non-porous, and furthermore, a structure that does not require a ring for setting a gap is used. Except for the drawbacks, the pack plate of the condenser microphone and its structure, which facilitates the automation of the assembling work and enables the supply of a compact and high-performance condenser microphone at low cost, has been developed. With the purpose of providing Is what you do.

According to the present invention, there is provided a pack plate of a capacitor microphone, wherein the effective surface is formed of a non-porous and non-flat rotating surface, and a rotating surface of an effective non-porous and non-flat surface. The inclined peripheral surface of the pack plate of the condenser microphone configured with the above is engaged with and held by the triangular cuts of a plurality of holding claws projecting from the insulating holding body, and the holding body is It is a component of a condenser plate of a condenser microphone that is fitted and fixed to another tube that forms part of the microphone.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 is a horizontal vertical sectional view of a conventional condenser microphone.

Fig. 2 is an equivalent circuit diagram of the condenser microphone of Fig. 1,

3 (a) to 3 (e) are schematic longitudinal sectional views showing a basic form of a pack plate and a diaphragm according to an embodiment of the present invention,

FIG. 4 is a perspective view showing the holding cylinder and the intermediate cylinder in the first embodiment,

FIG. 5 is a longitudinal sectional view of the microphone mouth phone according to the first embodiment, FIG. 5 is a longitudinal sectional view of the microphone mouth phone according to the second embodiment, and FIG. 7 is a holding cylinder and a diaphragm in the second embodiment. And a perspective view of the packing plate,

FIG. 8 is a longitudinal sectional view of the microphone according to the third embodiment, and FIG. 9 is a perspective view of the microphone according to the present invention having an electret film applied thereto. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described below with reference to FIGS.

FIG. 3 shows a basic form of the pack plate of the present invention and a configuration of a capacitor microphone horn which faces the diaphragm with a gap 3 therebetween. For the diaphragm 1 of the diaphragm, a film of biaxially stretched polyester resin having a thickness of 5 or less is suitable, and a metal layer such as aluminum is deposited on the upper surface as a conductive surface. It is spread flat on the ring frame 2 and electrically conductively bonded. If the surface of the pack plate 4 that faces the vibrating membrane 1 and forms a capacitance is the effective surface 7, the surface 7 is constituted by a rotating curved surface that is not a flat surface.

3 As shown in FIGS. 3 (a) and 3 (b), the surface of a small disk-shaped pack plate 4 mainly made of metal is formed into a convex or concave lens shape. The effective surface 7 is held by a highly insulating holding carrier, which will be described later, and faces the vibrating membrane 1 with a narrow gap 3 of about 20 to 30 to form a thin air layer. At the same time, a capacitance of about 20 to 30 PF is formed. .

In the convex lens pack plate shown in FIG. 3 (a), since the cross section of the gap 3 has a shape extending from the center to the outer periphery, the air flow in the gap is good. The air bypasses the peripheral end face 9 of the pack plate 4 and can easily reach the back chamber ό behind.As a viscoelastic effect of the thin air layer, the elastic CA is small and the viscous resistance r A is large. O PI be able to.

On the other hand, in the concave lens-shaped pack plate shown in Fig. 3 (), since the peripheral edge of the gap 3 is narrowed, the air flow is poor and the air tends to accumulate, the elastic CA is large, and the viscous resistance is high. ? · A becomes small. Thus, the packs shown in Figs. 5 (a) and 5 (b). Since the rate has contradictory erections, the radius of curvature of the convex or concave surface can be selected, or the optimal values of elasticity C A and viscous resistance r A can be obtained by combining the two. For example, as shown in Fig. 3 (c), a top flat type in which the center of the flat surface is a flat surface, as shown in Fig. 3 (d), a top concave type in which the center of the convex surface is a concave surface, etc. Is effective. The protruding type shown in Fig. 3 (e) is easy to process and can be manufactured at low cost. Furthermore, the mushroom-shaped mushroom-shaped ones shown in Fig. 8 are suitable for ultra-small microphones, and can be widely used depending on the application. The peripheral surface 9 of these pack plates is formed as an inclined surface in order to easily hold the pack plate, reduce stray capacitance, and improve air flow.

In order to construct a condenser microphone mouth phone using these pack plates, it is necessary to firmly hold the pack plate while maintaining the gap 3 with the diaphragm 1 at a predetermined size. is necessary.

Next, a condenser microphone as a structure using the pack plate will be described with reference to three embodiments.

O PI As shown in FIG. 4 (partial perspective view) and FIG. 5 (cross-sectional view of the entire structure), the insulating holder 10 made of synthetic resin has a right-angled triangular notch 1 The three holding claws 11 that form 1a are erected, and the pack plate 4 cuts the peripheral end face 9 while pushing the claws 11 slightly open using a jig (not shown). 1a is inserted, and the portion below the effective surface 7 is clamped by the claws 11. Then, this is press-fitted into a metal or resin intermediate cylinder 12. The flat surface 13 at the upper end of the intermediate cylinder 12 is a reference surface on which the diaphragm is placed, and is attached to a jig for setting the size of the gap 3 (for example, a flat surface plate, not shown). And press-fit the holder 10 into the intermediate cylinder 12 until the gap between the jig and the effective surface 7 reaches a predetermined gap. When the position is determined, the holder 10 and the intermediate cylinder Inject an appropriate amount of cyanoacrylate instant adhesive from the lower end to the contact surface with 1 and 2 to fix them together. This gap size setting is based on the capacitance measurement between the metal jig on which the flat surface 15 is placed and the pack plate 4 rather than the method of directly measuring the gap size as described above. The indirect setting method is preferred.

In this way, the pack plate having completed the setting of the gap 3 is held by pressing the tapered surface below the effective surface by the pawls 11 and press-fitted into the intermediate cylinder 12 to be joined. However, there is no fear that the information will be out of order. In addition, the peripheral end surface 9 of the pack plate 4 is held in an insulated manner by the inner surface of the intermediate cylinder 12 and the insulating retaining claws 11, so that the intermediate cylinder 1 2 There is no problem even if is made of metal. At the same time, there is an arc-shaped gap between the peripheral edge of the pack plate and the inner surface of the intermediate cylinder 12, separated by the holding claws 11, 11, so that there is free space between the gap 3 and the back chamber ό. It is possible to breathe air in the air, and there is no need to drill through holes 5 in the pack plate 4 as in the conventional case. A field-effect transistor 14 for constructing a capacitor microphone has a drain and source terminal 1 ό soldered to a printed circuit board 17, and a coil spring 15 connected to the gate. When the gate is inserted and inserted through the transistor opening 25 provided in the holder 10, the gate conducts to the back of the pack plate 4 and signal output can be taken out between the drain and source. State. Finally, the diaphragm is placed on the flat surface 13 at the upper end of the intermediate cylinder 12, the shield case 19 is fitted over it, and the lower end 20 of the case 19 is narrowed down. The vibrating membrane 1 is grounded to the case 19 via the metal ring frame 2 to form a transistor circuit and complete an integrated structure as a microphone unit. In order to make this microphone microphone have directivity, as shown in Fig. 5, the holes 21 of the printed circuit board 17, the ventilation resistance 22 of the felt, etc., and the holes 18 of the holder 10 The sidetone can be introduced into the back room を通して through the.

Example 2

The microphones shown in Fig. I (overall cross-sectional view) and Fig. 7 (partial configuration diagram) use a so-called tie pin microphone (neck collar microphone) with an outer diameter of about 〜 to 8. It is an example. In FIG. 7, the holding body 10 has four holding claws 11. It has a right-angled triangular notch 11 1a and a flat surface 13 at the upper end.When the diaphragm is placed on the flat surface 13, a notch is made so that the specified gap size can be obtained with the packed plate that is sandwiched. It is configured by determining the position of 1 1a. Therefore, after the diaphragm is inserted into the shield case 19 having the front opening 30, the holding body 10 holding the pack plate 4 is pressed into the case 19, and the screw at the lower end is inserted. When the lid 25 is tightened, the gap 7 is maintained between the surface 7 of the pack plate 4 and the diaphragm 1, and the claws 11 are tightened on the inner surface of the case 19.

In the second embodiment, the dimension between the lower surface of the notch 11a of the claw 11 of the holder 10 and the flat surface 13 at the upper end must be accurately obtained, and this is a limitation in processing. However, since the intermediate cylinder 12 in the first embodiment is not required, the outer diameter can be made thin. Therefore, this configuration is suitable for microphones that require miniaturization. When the microphone is unidirectional, the screw cap at the lower end as shown

If a sidetone is introduced into the case from the through hole 25 of 25, and this is led from the hole 21 of the printed circuit board 17 and the through hole 18 of the holder 10 to the back room 、, Directivity can be provided. In FIG. 5, numeral 2 denotes a wind screen, and numeral 27 denotes an output deriving code.

Example 3

As shown in Fig. 8 (cross-sectional view), the pack plate 4 is mushroom-shaped, has fixing feet 4a at the center of the lower surface, and is inserted into the hole at the center of the holder 10 of the ecstatic green. Penetration, caulking and fixing

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— I do. The flat surface 28 at the upper end of the shield case 19 is a reference surface for placing the diaphragm. In the case of assembly, this surface is placed on a metal flat plate (not shown) and While gradually measuring the capacitance between the plate 4 and the leveling plate, the holder 10 is gradually press-fitted. When the capacitance reaches a predetermined value, the connection between the holder 10, 10 and the case 19 is established. Inject an appropriate amount of cyanoacrylate instant adhesive from the rear end to the contact surface to complete the fixation. The field-effect transistor 14 has the drain and source terminals 1 ό attached to the printed circuit board 17, and the spring 15 is fitted to the gate to form the hollow caulking of the pack plate. Insert into the hole, connect cord 27 to terminal 1, and apply screw cap 25. Then, the diaphragm is placed on the flat surface 28 of the shield case 19, and the cap 29 having the front opening 30 is tightened to complete the microphone microphone.

The pack plate of the present invention used in the above three examples can be manufactured by using a precision die in a cold forging method using a metal plate such as a copper alloy or aluminum. High-precision products can be mass-produced and supplied at low cost. -In addition, in the case of electret microphones, which are awarded as small microphones, as shown in Fig. 9 (cross-sectional view), the electret microphones are formed by vacuum molding. Can be simultaneously coated on the surface 7 of a large number of metal pack plates, and unnecessary parts (called ears) can be punched out with a taper. It is easy if you use the surface. In the electret microphone, minute-polar processing (c:? Ι However, in the structure using the pack plate of the present invention, since the gap setting step can be performed on the completed structure, there is no charge decay such as deterioration of tentacles, which is advantageous. is there. This polarization treatment can be performed using either the high-pressure method, which is performed one by one, or the low-pressure method, which is performed simultaneously on a large number. That is, a ground electrode is inserted into the transistor opening 23 to ground the pack plate. In the high-pressure method, the needle end electrodes are opposed to each other, and a high-voltage collector of DC 25 KV or more is used. Discharge. In the low-pressure method, a multipole electrode for applying an electric field is adhered to the surface of a number of pack plate components arranged on a jig, and a voltage of 250 V DC or more is applied in a heating atmosphere. Slowly cools to obtain stable and good electret charges.

Ό o

The features of the above-described pack plate of the present invention and its components are listed below.

(1) The pack plate 4 is non-porous, the effective surface 7 is composed of a rotating curved surface, and by selecting the radius of curvature, the best value of the viscoelastic effect is obtained, and the DC pass type or electret A compact and high-quality condenser microphone can be constructed by applying it to any of the tube-type models.

(2) Pack plate 4 keeps the tapered peripheral end face insulating.

Holds the holding claw 10 with the holding claw 11 and presses it into the intermediate cylinder to tighten it. Or, if it has supporting feet, it will be caulked to the center of the holding body 10 and fixed, so stable performance Can be maintained. And the effective surface 7 is a curved surface

CMPI It does not matter if there is some inclination.

(3) Since a ring for setting the gap is not required, there are few defects and variations in sensitivity due to dust mixing during the assembly work, which is advantageous in automating the assembly work.

(4) The stray capacitance generated between the periphery of the pack plate and the ring frame 2 or the shield case 19 can be minimized to reduce sensitivity loss, improve ΖΝ ratio, and increase nonlinearity. Distortion (mainly third harmonic distortion) can be improved, which is particularly advantageous when constructing a small microphone with a small diameter.

(5) In the case of electret microphones, the electret film is simultaneously applied to the surface of many pack plates by vacuum molding, The excision is easy and there is no danger of turning over. If the polarization is performed during the assembly process, attenuation such as tentacle deterioration can be reduced. '-

(6) Capacitance, electric charge, insularity, etc. can be checked in a timely manner in the intermediate process of assembling by using the transistor opening, the early detection and rejection of defective products can be achieved, and the quality can be improved. Thorough management can be implemented.

0:? 1

Claims

The scope of the claims

1. A condenser microphone mouthpiece phon plate characterized in that the effective surface is non-porous and has a non-flat rotating surface.

2. The pack plate of the condenser mic opening horn according to claim 1, wherein an electret film is applied to an outer surface other than the bottom surface of the pack plate and a permanent charge is applied.

5. The inclined peripheral end face (9) of the condenser plate of condenser microphones, which has a non-perforated and non-flat rotating surface, is attached to the insulating holder (10). Triangular cuts of a plurality of protruding holding claws (11)

(11a), and the holding body (10) is fitted and fixed in another cylinder constituting a part of the microphone mouthpiece, thereby forming a microphone plate of the condenser microphone. body.

4. In Claim 3, the pack plate holder (10) and the other intermediate tube (12) constituting the capacitor microphone are slidable, and the effective surface of the pack plate and the intermediate tube After the gap between the diaphragm and the diaphragm stretched in contact with the reference end face of (12) is set to a predetermined value, the capacitor micro that fixes the pack plate holder (10) and the intermediate tube (12) is fixed. Hong's pack plate-construction.

5. In claims 3 or 4, the pack plate holder (10) is provided with a transistor opening (23), and the coilless spring (15) is fitted to the gate. Ngis

, Gu-, A hole is inserted into the opening (23), and the microphone is inserted through the spring (15). Mic plate structure of a condenser microphone with conduction between the rate (4) and the gate of the transistor.