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DESCRIPTION JPH03177198

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DESCRIPTION JPH03177198
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker used in various audio and visual devices. 2. Prior Art A conventional loudspeaker of this
type is configured as shown in FIG. That is, in the front portion of the upper plate 2 of the
magnetic circuit 4 configured by sandwiching the magnet 1 by the upper plate 2 and the lower
plate 3, from the range of 60% of the outer diameter of the upper plate 2 to the outer peripheral
portion The hold portion 5 of the magnetic circuit 4 is provided in such a shape that the
thickness becomes larger as the minimum thickness is IIn + 1 or more and closer to the outer
periphery, and the magnetic circuit 4 is integrated with the frame 6 and insert-molded by
thermoplastic resin The diaphragm 8 is bonded to the peripheral edge of the frame 6 of the
housing 7 obtained, and the voice coil 9 for driving the diaphragm 8 is centered with the damper
10 at its middle portion and fitted in the magnetic gap 11 The dust cap 12 is bonded to the
surface of the connecting portion of the diaphragm 8 and the voice coil 9 so as to be embedded.
SUMMARY OF THE INVENTION However, the conventional speaker of this type has a magnet
and a top plate. Since the magnetic circuit 4 composed of the lower plate 3 is insert-molded of
resin to form the frame-equipped casing 7, the magnetic circuit 4 is covered with resin around its
periphery. Therefore, when these are subjected to a reliability test, ie, a thermal shock test, a
stress generated due to a difference between the thermal expansion coefficient of the metal
material constituting the magnetic circuit 4 and the resin material insert-molding them due to a
change in ambient temperature. Cracks from the resin portion around the magnetic circuit 4,
particularly from the inside diameter of the holding portion 5 on the front surface of the upper
plate 2, making it impossible to hold the magnetic circuit 4 for a long time, or the cracks There
were quality problems such as generation of abnormal noise due to flicker between the magnetic
circuit 4 and the resin portion in which a crack occurred during the speaker operation test. The
present invention solves such conventional problems, heat,? It is an object of the present
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invention to provide a speaker having a resin circuit of magnetic circuit insert molding type
which has very excellent performance against the reliability such as the In shock. Means for
Solving the Problems In order to solve the above problems, the present invention improves the
shape and size of the inner diameter portion of the holding portion of the upper plate where the
crack is generated among the resin portions holding the magnetic circuit. That is, the size of the
inner diameter portion of the hold portion is large, and the minimum thickness portion of the
innermost diameter portion is made larger than that of the conventional product to make the
hold portion stronger.
With the above-described structure, even if stress due to thermal expansion or thermal
contraction of the magnetic circuit generated from a change in ambient temperature is applied,
the mechanical strength of the inner diameter portion of the hold portion is strong, thereby
preventing generation of cracks and heat The reliability against impact is improved, and the
magnetic circuit can be held for a long period of time, so that the occurrence of cracked defects
does not occur. Embodiment A speaker having a resin frame of a magnetic circuit insert molding
type according to an embodiment of the present invention will be described with reference to the
drawings. As shown in FIG. 1, the front surface portion of the upper plate 22 of the magnetic
circuit 24 configured by sandwiching the magnet 21 by the upper plate 22 and the lower plate
23 is in the range of 70% to 90% of the outside dimension of the upper plate 22. To the outer
periphery, that is, in this embodiment, for the outer diameter 50rIIm of the upper plate, an inner
diameter portion of 40% which is 80% thereof is provided, and the minimum thickness portion
thereof is 1.2 mm or more That is, in this embodiment, the hold portion 25 of the magnetic
circuit 24 is provided in such a shape that a thick portion of two ridges is provided and the
thickness becomes larger as it gets closer to the outer peripheral portion. Integrated with the
part 25 and insert molded with thermoplastic resin, that is, resin such as PS (polystyrene) or ABS
(acrylonitrile butadiene styrene) Constitute a housing 27. Then, a diaphragm 28 is bonded to the
peripheral portion of the frame 26 of the housing 27, and the voice coil 29 for driving the
diaphragm 28 is center-held by the damper 30 at its middle portion. The dust cap 32 is bonded
to the surface of the connecting portion of the diaphragm 28 and the voice coil 29 so as to be
embedded. In this way, the reinforced hold portion 25 on the front surface of the top plate 22 of
the magnetic circuit 24 prevents the occurrence of cracks even when thermal shock is applied.
As described above, according to the present invention, since the hold portion on the front
surface of the top plate of the magnetic circuit is reinforced by its shape and size, thermal
expansion and thermal contraction of the magnetic circuit caused by a change in ambient
temperature By preventing the cracks in the inner diameter portion of the hold portion generated
from the dimensional change, the reliability such as thermal shock can be improved, and the
magnetic circuit can be held for a long time. Furthermore, in the prior art, due to the occurrence
of this crack, an abnormal sound due to flickering was generated between the resin portion
where the crack occurred and the magnetic circuit at the time of the operation test of the
speaker, and defective products occurred frequently. It is possible to provide a speaker which can
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be prevented simultaneously and which can simultaneously improve the reliability and reduce
the defect rate, and its industrial value is very great.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a cross-sectional view of a speaker having a resin frame of a magnetic circuit insert
molding type according to an embodiment of the present invention, and FIG. 2 is a crosssectional view of a speaker having a resin frame of a conventional magnetic circuit insert
molding type. It is.
21 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · hold part · · · · · · · · · · · · · · · Frame, 27 · · · · housing · · · · · · · · · · · ·
· · · voice coil, 30 · · · · damper 31 ... Magnetic gap, 32 ..... Dust cap.
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