JPS599516Y2 - condenser microphone - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a condenser microphone in which a diaphragm, a back electrode, a holder thereof, etc. housed inside the capsule are mechanically fixed by crimping the ends of the capsule.

In this type of condenser microphone, the internal parts are mechanically stabilized by crimping, which simplifies manufacturing and assembly; however, crimping can cause the diaphragm to become too tight or sag, leading to variations in sensitivity. was there.

Furthermore, it was necessary to increase the accuracy of the fitting for holding the back electrode in its holder.

First, let's clarify these problems by explaining the condenser microphone.

As shown in FIG. 1, a cylindrical capsule 11 made of aluminum, for example, with one end closed is used, the closing plate is a front plate 12, and a central hole 1 is formed in the center of the capsule.
3, and a cloth 14 is attached to the front plate 12 so as to close the center hole 13 and allow sound to pass through but block dust and the like.

Inside the capsule 11, the diaphragm 1 faces the front plate 12.
5 is placed.

The diaphragm 15 is, for example, attached to one surface of the ring 16. In this example, an electret diaphragm is used as the diaphragm 15, and the dielectric film is polarized to form an electret I. A metal film is adhered to the metal ring 16, and the metal film side is in contact with and stuck to the metal ring 16.

A side of the ring 16 opposite to the diaphragm 15 is in contact with the front plate 12.

A back electrode 18 is arranged facing the diaphragm 15 with a ring-shaped spacer 17 in between.

The back electrode 18 is a cylindrical holder 19 made of a composite resin material.
is fitted and held at the end of the

That is, the inner peripheral surface of the end of the holder 19 on the back electrode 18 side is made large in diameter to form a holding portion 21, and the back electrode 1 is held in the holding portion 21.
8 is fitted and held.

An acoustic passage 22 is formed in the back electrode 18 .

An impedance conversion element 23 electrically connected to the back electrode 18 is provided within one holder.

The impedance conversion element 23 converts a high impedance input signal into a low impedance signal.

The output terminal 25 of the impedance conversion element 23 is connected by solder 26 to a wiring board 24 that is in contact with the back side of the holder 19, that is, on the side opposite to the back electrode 18.

The open end of the capsule 11 is bent and pressed against the back surface of the wiring board 24 and is so-called caulked.
9 is pressed against the front plate 12, and these internal parts are mechanically fixed.

When the end of the capsule 11 is crimped, in order to accurately maintain the distance between the diaphragm 15 and the back electrode 18, that is, to maintain the thickness of the spacer 17 between them, the holding portion 21 of the holder 19 must be The thickness D1 of the back electrode 18 is selected to be larger than the height of the peripheral wall portion 27, that is, the distance H1 from the back electrode contacting surface 28, which receives one surface of the back electrode 18, to the end surface on the diaphragm 15 side. In other words, it is necessary to maintain this state even in the case where the holder 19 is disposed on the diaphragm side.

When the height H1 becomes larger than the thickness D1, the distance between the diaphragm 15 and the back electrode 18 is no longer determined by the thickness of the spacer 17.

The height H1 varies depending on the conditions when the holder 19 is shaped, and the thickness D1 of the back electrode 18 also varies. Taking these variations into account, the thickness D1 must be larger than the height H1.

In order to prevent the effective area of the diaphragm 15 from becoming smaller as the size of the microphone decreases, the ring 16 of the diaphragm is brought as close to the inner peripheral surface of the capsule 11 as possible.

On the other hand, as mentioned earlier, a gap 29 exists between the spacer 17 and the holder 19.

Therefore, when the capsule 11 is crimped, the outer peripheral edge 31 of the ring 16 is pressed so as to rotate toward the end surface of the holder 19 using the outer peripheral edge 32 of the back pole 18 as a fulcrum, as partially shown in FIG. 2A. Therefore, as shown in FIG. 2B, the ring 16 is bent and the diaphragm 15 is tensioned more strongly than necessary, or conversely, the inner diameter of the ring 16 is reduced and the tension of the diaphragm 15 is loosened. In some cases, the diaphragm 15 came into contact with the back electrode 18 and was attracted to it.

In these cases, the product will be defective, and even if it is not a defective product, the gap between the diaphragm 15 and the back electrode 18 will not be constant, and the sensitivity for keeping the tension of the diaphragm 15 constant will vary widely.

In order to avoid such a situation as much as possible, it may be possible to increase the thickness D2 of the peripheral wall 27 of the back electrode holding portion 21, but doing so would increase the overall size and go against miniaturization.

On the other hand, it is conceivable to make the thickness of this peripheral wall 27 sufficiently small, but if it is made too small, there is a risk that the thin peripheral wall 27 will break when fitting the back electrode 18 to the holding part 21. Then, when the holder 19 is made by molding, there is a problem that the flow of hot water from the mold to that part is poor, and the holding part 21 having a predetermined peripheral wall cannot be made.

Furthermore, in conventional condenser microphones, the entire diaphragm 1 is compressed in its axial direction when tightened.
The volume of the acoustic chamber on the back side of the microphone 5, the so-called back chamber, is reduced as a whole, and as a result, a large amount of pressure is applied to the diaphragm 15, which may cause the sensitivity of the microphone to deviate from a predetermined value.

Furthermore, the air pressure applied to the diaphragm 15 changes due to the expansion and contraction of the air in the back chamber due to changes in ambient temperature, and the sensitivity is affected by the temperature.

This design prevents the diaphragm from becoming too tight or too loose when the capsule is tightened, and the air pressure applied to the diaphragm does not change significantly even if the volume of the back chamber changes. To provide a condenser microphone which is easy to manufacture without having to make the precision of fitting held in a back electrode holder very strict, has no variation in sensitivity, and is not subject to changes in sensitivity due to temperature changes. There is a particular thing.

According to this invention, a notch is provided on the circumferential surface of the holding part of the back electrode surface that holds the back electrode, and a convex part is provided on the back end face and the opposing surface, and this convex part is deformed by crimping. It is assumed to have a certain elasticity.

For example, in FIG. 3, parts corresponding to those in FIG. 1 are given the same reference numerals.

In this invention, a notch 3 is provided in the peripheral wall 27 of the back electrode holding portion 21.
4 are provided at equal angular intervals, for example.

This notch 34 is configured to reach the bottom surface of the holder holding portion 21, that is, the contact surface 28 that receives the back electrode.

A convex portion 35 is integrally formed on the bottom surface 28 of the holding portion 21.

In this example, the convex portion 35 is formed as a ring-shaped protrusion along its surface, and the protrusion has a height of, for example, Q. It is said to be about lmm.

During this caulking, the protrusion is deformed so that its height can be reduced.

Further, a convex portion of the ring-shaped protrusion 35 is cut away from the notch 34, and in this example, a passage 36 is formed by cutting off a convex portion at a portion corresponding to exactly the middle position between the two notches 34.

As shown in FIG. 5, the thickness D1 of the back electrode 18 is selected to be larger than the distance H2 from the top surface of the convex portion 35 to the end surface of the holder 19 on the diaphragm side.

The height H1 of the peripheral wall 27 is selected to be larger than the thickness D1.

In other words, H1>D1>H2. Therefore, before crimping, the back electrode 18 is located closer to the diaphragm than the end surface of the peripheral wall 27, and as a result of crimping, the convex portion 35 is squeezed, and the end surface of the peripheral wall 27 approaches or contacts the spacer 17. It will be done like this.

Therefore, the distance between the back electrode 18 and the diaphragm 15 is set by the spacer 17.
The thickness is precisely maintained as determined by the thickness of the material.

Moreover, as described with reference to FIG. 2, even if a force that causes the ring 16 to curve is applied, the convex portion 35 is crushed, so the ring 16 will not be deformed, and in other words, the tension of the diaphragm 15 will not change. do not have.

Moreover, there is no possibility that the end face of the peripheral wall 27 and the spacer 17 will come into contact with each other and the diaphragm 15 will be attracted to the back electrode 18.

Even if the size of the back electrode 18 varies slightly when fitting it into the holder 19 and excessive force is applied to the peripheral wall 27, the presence of the notch 34 prevents the peripheral wall 27 from deforming and damaging the back electrode 18. is retained.

Furthermore, even if the air pressure in the back chamber changes, a small air passage is formed between the ring-shaped protrusion 35 and the peripheral wall 27 and the outside through the notch 34, so that the air pressure in the back chamber gradually changes to the outside air pressure. Follow and match.

Therefore, there is no fear that the diaphragm 15 will swell due to changes in ambient temperature or changes in internal volume during crimping, and the sensitivity can be maintained constant.

The convex portion 35 is the bottom surface 2 of the holding portion as shown in FIG.
8 may be formed on the rough surface 37.

In this case, there is no need to particularly shape the passage 36.

If you want to show off this rough surface, you can do it by making a scratch on it.

This applies not only to the bottom surface 28 but also to the back electrode 18.
The surface in contact with the bottom surface 28 may be a rough surface.

As shown in FIG. 7, a separation wall 38 is integrally formed in the middle part of the holder 19 in the axial direction, and the separation wall 38 acoustically separates the diaphragm 15 side and the impedance conversion element side. This idea can be applied.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional condenser microphone.
FIG. 2 is a partially enlarged sectional view for explaining the influence of the ring 16 when tightening the capsule, and FIG. 3 is a sectional view showing an example of the condenser microphone according to this invention.
Fig. 4 is a plan view of the holder 19, Fig. 5 is a partially enlarged view of the relationship between the holding part and the back electrode, Fig. 6 is a partially sectional view showing a modification of the convex part, and Fig. FIG. 7 is a sectional view showing another example of the condenser microphone according to the invention. 11: Capsule, 15: Vibration plate, 17: Spacer, 18
: back electrode, 19: holder, 21: holding part, 27: peripheral wall,
28: Back electrode contact surface of holding part, 34: Notch, 35.37
: Convex part.

Claims (1)

[Scope of utility model registration request] A spacer is interposed between the diaphragm and the back electrode in the capsule, the back electrode is fitted and held at the end of the cylindrical holder, and by bending and crimping the end of the capsule, the diaphragm, In a condenser microphone in which a back electrode holder is mechanically fixed, a notch is formed in the peripheral wall of the back electrode fitting part of the holder, and the back electrode contact surface of the holder that receives the negative surface of the back electrode is provided with a notch. A condenser microphone that has a convex shape that can be deformed by caulking.