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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
heat-resistant center cap for a speaker characterized by using a heat-resistant resin material.
[Background Art] A center camp is attached to the center of a diaphragm of a cone type speaker
to prevent the entrance of iron powder, iron powder and the like into a magnetic circuit gap. The
same material as the diaphragm or one using metal simultaneously serves as a diaphragm.
Conventionally, an aluminum foil, a felt, or a cloth is used for the center cap, and a polyethylene
terephthalate film has been used as a plastic. In the case of the speaker, since the vicinity of the
voice coil which is the driving source is heated at the time of driving, it is desirable that the
center cap be made of a material sufficiently resistant to high heat. However, metal foils and the
like have been used for applications where heat resistance of polyethylene terephthalate at a
continuous use temperature of C. or higher is required. OBJECTS OF THE
INVENTION The present invention has been devised to provide a high heat resistant, good center
cap which has hitherto not been possible with plastics. [Structure of the Invention] In the present
invention, a film having an amorphous thermoplastic polyetherimide resin as a main component
is formed into a speaker center cap. The amorphous thermoplastic polyetherimide resin is, for
example, one having cyclic units. [Effects of the Invention] The film used in the present invention
has excellent heat resistance, a continuous cap temperature of about 170 ° C., and a selfextinguishing property. Is most suitable as a center cap for applications requiring heat resistance
and flame resistance, such as in-vehicle use. Also, the film is amorphous, does not crystallize even
if it is left in a high temperature atmosphere for a long time, and hardly changes in size.
Therefore, the change in the appearance, of course, has little influence on the reproduction in the
middle or high range. EXAMPLE A film having a basic structure shown below was used as a
diaphragm forming film. The physical properties of the film having the above-mentioned basic
structure were a specific gravity of 1,27, an elastic modulus IC4000 (kf / d) and a loss of 0.11.
Vacuum forming was performed as a method of forming the diaphragm, and a center cap having
a diameter of 40 鵡 φ and a thickness of 40 μm was formed. Using this center cap, a speaker as
shown in FIG. 1 was made. When this center cap was left at 150 ° C. for 2 hours, no change in
shape was observed.
The table shows the dimensional change at 150 ° C. of the film of the example and the
polyethylene terephthalate film. Table: Dimension change after leaving at 150 ° C for 1 hour
Brief description of the drawings
FIG. 1 is a cross-sectional view of a speaker using the center cap of the present invention.
1 is a diaphragm, 2 is an edge, 3 is a center cap, 4 is a yoke, 5 is a magnet, 6 is a voice coil, 7 is a
center ball, 8 is a bobbin. Patent applicant Sumitomo Bakelite Co., Ltd. Fig. 1
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