JPS6366479B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dust cap for a cone type speaker, etc.

As shown in FIG. 1, the cone-shaped speaker includes a magnetic circuit 4 including a magnetic gap 3 formed by a plate 1 and a center pole 2, a coil bobbin 6 wound with a voice coil 5 disposed in the magnetic gap 3, and a coil bobbin 6 wound with a voice coil 5 arranged in the magnetic gap 3. A damper 7 that elastically supports the coil bobbin 6 in the center, a cone paper 8 fixed to the upper end of the coil bobbin 6, an edge 10 that connects the outer edge of the cone paper 8 and the frame 9, and the edge 10 extends the outer edge of the cone paper. It can be molded into one piece, or it can be molded from separate parts and then glued together. and the upper edge of the coil bobbin 6 or the coil bobbin 6 of the cone paper 8
It consists of a dust cap 11 fixed near the attachment part of the dust cap.

As is well known, the purpose of the dust cap 11 is to prevent dust in the air from entering the gap between the coil bobbin 6 and the center pole 2 through the upper end opening of the coil bobbin 6.

On the other hand, since the dust cap 11 is connected to the coil bobbin 6 or the cone paper 8, it vibrates in accordance with the vibration of the coil bobbin 6 and radiates sound waves forward.

If this sound wave is in phase with the sound wave emitted from the paper cone 8, it will not cause any adverse effects, but due to interference with the in-phase and anti-phase components due to self-resonance at a specific frequency, it may cause interference with the in-phase and anti-phase components, especially at high frequencies of the speaker. Steep peaks and dips occur in the characteristics, causing a significant deterioration of hearing sensation.

However, at present, dust cap 11
At present, little consideration has been given to suppressing the resonance, and at best, a significant internal loss is caused by attaching or painting a viscoelastic material or the like.

In general, a large internal loss and a large Young's modulus are contradictory properties in terms of material properties.
It is extremely difficult to satisfy both.

From this point of view, among synthetic resin materials, polyolefin-based synthetic resin materials are currently attracting attention as materials that are close to the above objectives.

For example, polyethylene, one of the polyolefin synthetic resins mentioned above, has a small density (ρ<1.0).
Since E/ρ (E: Young's modulus, ρ: density) is relatively large, the second moment of area per unit weight (Eh ³ /12, h: thickness) is large, resulting in high shape rigidity and internal Loss (tanδ) is 0.05 to 0.1
It has extremely high properties and is more preferable as the material for the dust cap.

However, as is well known, since the polyolefin resin has a non-polar crystal structure, it has defects in which adhesiveness is extremely poor.

Therefore, when using the polyolefin resin for the dust cap, the adhesive strength with the diaphragm or coil bobbin becomes a problem, and various proposals have been made to solve this problem.

For example, there are methods of activating the surface of the resin by corona discharge, gas flame, or chemical treatment, and surface roughening by sandblasting.

These treatments improve the adhesion to some extent, but from a cost standpoint, it is not desirable to add such treatment means.

Therefore, this invention improves adhesion by forming a dust cap with chlorinated polyolefin resin, minimizes the cost increase associated with this, and minimizes the deterioration of the properties of polyolefin resin. Chlorinated polyethylene will be explained in more detail below.

Chlorinated polyethylene is obtained by chlorinating polyethylene in a solution or suspension of carbon tetrachloride, chloroform, trichlorethylene, etc. at a temperature below 60°C, or by chlorinating polyethylene powder in an aqueous suspension with chlorine gas. .

By molding these into a film, a chlorinated polyethylene dust cap material is completed.

A dust cap (dome shape, etc.) can be obtained by vacuum or pressure forming this as in the conventional method.

Dust caps made of such chlorinated polyethylene have improved adhesion due to the active groups of chlorine, and can obtain sufficient adhesive strength between the dust cap and the diaphragm and coil bobbin without any other treatment. Ta.

In addition, there are various advantages when applied not only to the chlorinated polyethylene alone but also to a composite dust cap in which the chlorinated polyethylene is used as a part of the structure.

For example, in order to impart rigidity to the chlorinated polyethylene diaphragm, titanium, beryllium, magnesium, aluminum, etc., or an alloy or compound thereof, and a boron layer formed on the surface to further increase the rigidity of the above metals. or thermoplastic resins that are more rigid than chlorinated polyethylene, such as polystyrene, styrene-based copolymers, ABS resin, PVC, polycarbonate, polybutylene terephthalate, or carbon fibers,
When providing a dust cap laminated with reinforced thermoplastic synthetic resin mixed with carbon flakes, silicon carbide, glass fiber, glass flakes, aromatic polyamide fiber, etc., there is no significant adhesion between the dust cap and the metal or thermoplastic resin. You can gain power.

In addition, chlorinated polyethylene, which has a chlorination content of about 45%, has the maximum internal loss at room temperature, so it has the most remarkable effect of effectively suppressing resonance, which is a disadvantage of a highly rigid diaphragm.

Furthermore, by mixing the chlorinated polyethylene with polyethylene, it is possible to increase the adhesive strength compared to polyethylene alone, and it is possible to minimize the loss of the physical properties of polyethylene. Further, chlorinated polypropylene, which is another chlorinated polyolefin, may be mixed.

Although the above explanation has been made regarding chlorinated polyethylene, the same effect can be obtained also with chlorinated polypropylene.

As explained above, the present invention is a dust cap made of a chlorinated polyolefin or a composite that includes the chlorinated polyolefin as a part of its structure, and it is possible to improve adhesiveness without involving any other processing steps. This made it possible to assemble it in the same way as before.

On the other hand, the dust cap has an extremely large internal loss, and also has a large shape rigidity as mentioned above. Furthermore, by having a composite structure as mentioned above, the dust cap has the characteristics of high rigidity and large internal loss. It can be made to have both.

Therefore, since the speaker equipped with the dust cap according to the present invention has a large internal loss, the resonance suppressing effect of the dust cap is extremely large, so that it is possible to prevent an adverse effect on the frequency characteristics of the speaker, and it also has a high rigidity. It supplements the strength of the cone paper 8 and the coil bobbin 6 in the radial direction, and has a remarkable effect of suppressing abnormal noises caused by gear misalignment due to bell vibrations, voice coil short-circuit accidents, etc.

[Brief explanation of drawings]

The drawing is a cross-sectional view of a cone-shaped speaker.

Claims (1)

[Scope of Claims] 1. A dust cap for a speaker, characterized in that it is formed from a chlorinated polyolefin resin or a composite material comprising this as a part of the structure. 2. The dust cap for a speaker according to claim 1, wherein the composite is made by laminating metal foil on the surface of a chlorinated polyolefin resin. 3. The speaker dust according to claim 1, wherein the composite is made by layering a thermoplastic resin or reinforced thermoplastic resin with a higher Young's modulus on the surface of a chlorinated polyolefin resin. Cap. 4. The dust cap for a speaker according to claim 1, wherein the composite is a mixture of a chlorinated polyolefin resin and a polyolefin resin.