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DESCRIPTION JPH07111695

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DESCRIPTION JPH07111695
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker center cap which is disposed at the center of a cone and which functions as a part of a
diaphragm and functions as dustproofing, and a method of manufacturing the same.
[0002]
2. Description of the Related Art A speaker center cap (hereinafter referred to as a center cap) is
a component attached near the center of a cone, and has a dustproof function and several
functions.
[0003]
When the diameter of the voice coil is large, etc., the center cap itself also becomes large and
vibrates together with the diaphragm, which may affect the reproduction of the high-frequency
range as a part of the diaphragm. In such cases, materials such as duralumin foil are often used.
[0004]
It may be used to cut the high range quite the contrary.
At this time, the center cap is attached to the middle part of the cone to block the high sound
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emitted from the cone neck.
The radial strength of the cone can also be increased by using a strong material for the center
cap. In addition to this, there is also a dustproof one having air permeability by using a felt or
cloth.
[0005]
Thus, the center cap has various functions as a part of the vibrating part, and is regarded as one
of the very important parts.
[0006]
Such a center cap is used, for example, in a dynamic speaker as shown in FIG.
[0007]
That is, a magnetic circuit is configured by the back plate 1 having the pole piece 2 at the center,
and the magnet 3 and the plate 4 mounted on the back plate 1.
The voice coil bobbin 6 supported by the damper 7 is inserted into the magnetic gap provided
between the plate 4 and the pole piece 2.
[0008]
The voice coil 5 wound around the voice coil bobbin 6 is coupled to the diaphragm 8.
The outer peripheral edge of the diaphragm 8 is attached to the frame 11 via the edge 10. A
center cap 9 is attached to the center of the diaphragm 8.
[0009]
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In such a configuration, when an audio signal is supplied to the voice coil 5, the voice coil bobbin
6 moves up and down in the magnetic gap by the reaction of the magnetic flux with the magnet
3, and the sound wave is emitted by the vibration of the diaphragm 8. . At this time, the center
cap 9 is connected to the diaphragm 8 and vibrates simultaneously with the diaphragm 8 to
affect the sound pressure frequency characteristics. Therefore, various materials are considered
as in the diaphragm 8.
[0010]
As described above, in the conventional center cap 9 described above, various materials are
considered as in the case of the diaphragm 8 because the sound pressure frequency
characteristics are greatly affected. .
[0011]
That is, as described above, in the case of a speaker with a large diameter having a large voice
coil diameter, the center cap 9 itself becomes large, so the generation of sound due to the natural
vibration of the center cap 9 itself becomes a problem.
[0012]
In order to solve such a problem, a woven fabric of polyester is coated with a urethane resin and
molded, or a paper is used which is diluted and impregnated with an adhesive of a rubber thread.
Of course, a center cap made of paper itself is also used.
[0013]
The purpose of these materials is to utilize the large internal loss, suppress the natural vibration
of the center cap 9 itself, and eliminate the influence on the sound pressure frequency
characteristics by lowering the resonance frequency. It is.
[0014]
However, with conventional materials, it is not sufficient in terms of internal loss, and it is
insufficient to avoid the influence on sound pressure frequency characteristics.
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[0015]
The present invention has been made to cope with such a situation, and a speaker center cap that
can eliminate the influence on sound pressure frequency characteristics by increasing the
internal loss and lowering the resonance frequency, and its manufacture Intended to provide a
method.
[0016]
[Means for Solving the Problems] The speaker center cap according to the present invention is
integrated with a shortcut fiber of synthetic fiber, or a base body formed by mixing fibrillated
fiber and wood pulp. It is characterized in that it is composed of roughly kneaded SBR, NBR, butyl
and other rubber bodies.
[0017]
The method for producing a speaker center cap according to the present invention is mainly
composed of wood pulp and contains 5 wt% to 50 wt% of shortcut fibers of synthetic fibers
having an mp (melting point) of 120 ° C. to 170 ° C. or fibrillated fibers. A sheet-formed
product obtained by blending in weight% and forming into a sheet, and press-drying so as not to
dissolve the synthetic fiber is placed in a mold of a predetermined shape, and further roughlyground rubber such as SBR, NBR, butyl and the like It is placed and vulcanized at a vulcanization
temperature of 170 ° C. to 190 ° C. to unite the synthetic fibers while melting, and then cut
into a predetermined shape.
[0018]
[Function] The speaker center cap according to the present invention can be formed by
integrating a short body of synthetic fiber or a base body formed by forming a fibrillated fiber
with a rubber body such as coarsely blended SBR, NBR or butyl. Because it is formed, the internal
loss is further enhanced compared to the internal loss of each of the paper and rubber alone.
[0019]
In the method of manufacturing a center cap for a speaker according to the present invention, a
natural material such as wood pulp which can be selected relatively freely is used as a base, and
is melted at a temperature below the vulcanization temperature of rubber described later. The
short-cut fiber or pulp of the plastic resin is compounded and vulcanized, and at the same time, is
integrated in a molten state, and the integrated member has a further increase in internal loss
compared to the internal loss of paper or rubber alone.
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[0020]
As natural fibers, in addition to BKP, BSP, UKP, and USP made from common wood pulp, fibers
such as cotton linters and kapok can also be used.
Also, bast fibers and the like can be used.
[0021]
As synthetic fibers having an mp (melting point) of 120 ° C. to 170 ° C., for example, cut fibers
of acrylic fibers, cut fibers of polyethylene fibers, and so-called synthetic pulps which are also
high density polyethylene pulps can be used.
[0022]
There is no particular limitation on the cut length of the fiber, but about 1 to 3 mm is preferable
to achieve good dispersion.
[0023]
As rubber, typical SBR, NBR, butyl etc. can be used.
Of course, it is generally said rubber, and a vulcanizing agent, a vulcanization accelerator, a
dispersant and a stabilizer are blended.
[0024]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the embodiments of
the speaker center cap and the method of manufacturing the same according to the present
invention will be described with reference to the drawings.
In the drawings described below, the parts common to FIG. 1 will be described with the same
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reference numerals.
[0025]
FIG. 1 shows an embodiment of a speaker center cap according to the present invention, wherein
the center cap 9 is a base body 9a formed of a synthetic short cut fiber or a fibrillated fiber, and
the base body 9a. It is composed of a coarsely kneaded SBR, NBR, a rubber body 9b such as butyl
integrated with 9a.
[0026]
Then, the manufacturing method of the center cap for speakers is demonstrated.
The softwood bleached kraft pulp (NBKP) is beaten (brushed and beaten) so as not to lose the
fiber form in a beader, beaten to 710 ml with a Canadian freeness tester, and dispersed in water.
Next, this suspension is formed into a sheet with a predetermined center cap shape, and is
pressed and dried in a mold.
The drying temperature at this time is 180 ° C.
[0027]
Comparative Example A 20 wt% high density polyethylene pulp is blended with the raw material
of the comparative example, similarly, it is formed into a sheet with a predetermined center cap
shape, and it is breath-dried by a die.
The drying temperature at this time is 180 ° C.
Therefore, in this example, the high density polyethylene pulp is once melted and heat sealed.
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[0028]
Comparative Example A 40 wt% high density polyethylene pulp is blended with the raw material
of the comparative example, and it is formed into a sheet with a predetermined center cap shape
in the same manner as the comparative example and the comparative example, and press dried
with a die.
The drying temperature at this time is 180 ° C.
Therefore, also in this example, the high density polyethylene pulp is once melted and heat
sealed.
However, in the case of the composition of 40 wt%, since the mold is fused, the mold is once
cooled to 90 ° C. and then taken out.
[0029]
Comparative Example Instead of the high density polyethylene pulp of the comparative example,
20 wt% of cut fibers of acrylic fiber are blended, similarly, it is formed into a sheet with a
predetermined center cap shape, and is pressed and dried by a mold. The drying temperature at
this time is 180 ° C. The acrylic fiber used in this example has a cut length of 5 mm and an mp
of 150.degree. Therefore, also in this case, it is once melted and heat sealed.
[0030]
Comparative Example Instead of the high density polyethylene pulp of the comparative example,
20 wt% of cut fibers of polypropylene fiber are blended, similarly, it is formed into a sheet with a
predetermined center cap shape, and press dried with a mold. The drying temperature at this
time is 180 ° C. The polypropylene fiber used in this example has a cut length of 5 mm, mp 190
° C. Therefore, in this case, it remains in the fibrous state without melting.
[0031]
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Comparative Example Cotton linters are used in place of NBKP of the comparative example.
Similarly, brushing beating is performed, and the beating degree is 750 ml. A cotton linter is
dispersed in water, similarly made into a sheet with a predetermined center cap shape, and pressdried with a die. The drying temperature at this time is 180 ° C.
[0032]
Comparative Example Instead of NBKP in the comparative example, a kabok is used. In this case,
free beating is performed to cut the fibers. The freeness is 640 ml. The Kabok is dispersed in
water, similarly made into a sheet with a predetermined center cap shape, and press-dried with a
die. The drying temperature at this time is 180 ° C. Then adjust the rubber. The base rubber is
butyl rubber, to which 0.5 to 2.4 wt% of sulfur, zinc flower l. 8 to 4.9 wt%, and 0.5 to 3.8 wt% of
DM as a vulcanization accelerator are blended and sufficiently cured.
[0033]
Example The above-prepared butyl rubber is placed on a comparative example, and heated and
pressurized with a mold having a predetermined shape. The pressure is 40 kg / cm 2, the
vulcanization temperature is 180 ° C., and the vulcanization time is 8 minutes. In the paper
making process of the comparative example, the press drying temperature is performed at 120
° C., and a center cap is left without leaving the form of fibers without melting high density
polyethylene pulp. The above-prepared butyl rubber is placed on this, and heated and
pressurized with a mold having a predetermined shape. The pressure is 40 kg / cm 2, the
vulcanization temperature is 180 ° C., and the vulcanization time is 8 minutes.
[0034]
EXAMPLE In the paper making process of the comparative example, the press drying
temperature is 120 ° C., and a center cap is left without leaving the form of fiber without
melting high density polyethylene pulp. The above-prepared butyl rubber is placed on this, and
heated and pressurized with a mold of a predetermined shape. The pressure is 40 kg / cm 2, the
vulcanization temperature is 180 ° C., and the vulcanization time is 8 minutes.
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[0035]
EXAMPLE In the paper making process of the comparative example, the press drying
temperature is 140 ° C., and a center cap is left without leaving the form of the acrylic fiber cut
without melting. The above-prepared butyl rubber is placed on this, and heated and pressurized
with a mold having a predetermined shape. The pressure is 40 kg / cm 2, the vulcanization
temperature is 180 ° C., and the vulcanization time is 8 minutes.
[0036]
Example The above-prepared butyl rubber is placed on a comparative example, and is heated and
pressurized with a mold having a predetermined shape. The pressure is 40 kg / cm 2, the
vulcanization temperature is 180 ° C., and the vulcanization time is 8 minutes. In this case, since
the polypropylene fiber was not melted originally, it was carried out in the meaning of
comparison between the case of melting and the case of not melting.
[0037]
Example The above-prepared butyl rubber is placed on a comparative example, and is heated and
pressurized with a mold having a predetermined shape. The pressure is 40 kg / cm 2, the
vulcanization temperature is 180 ° C., and the vulcanization time is 8 minutes.
[0038]
Example The above-prepared butyl rubber is placed on a comparative example, and is heated and
pressurized with a mold having a predetermined shape. The pressure is 40 kg / cm 2, the
vulcanization temperature is 180 ° C., and the vulcanization time is 8 minutes.
[0039]
EXAMPLE The same combination as in the example, but with the rubber down and the base cap
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as the base up. Next, these physical properties are shown in Table 1.
[0041]
From the above results, it can be seen that although the level of internal loss is slightly different
depending on the type of natural fiber to be a base, when the thermoplastic resin fiber is clearly
blended, the internal loss becomes larger. In addition, those having mp higher than the
vulcanization temperature, ie, those that do not melt during vulcanization, have a low effect when
they are blended with thermoplastic resin fibers, and they do not blend thermoplastic resin
fibers, that is, It is also understood that there is not much difference from the case of using only
natural fibers.
[0042]
Furthermore, it is also understood that the effect is different in the positional relationship
between the center cap of the base and the rubber when vulcanized, that is, when the rubber is
upside and downside.
[0043]
As described above, in the present embodiment, the resonance of the center cap for the speaker
can be suppressed by increasing the internal loss, and the Young's modulus is also increased as it
appears in the physical properties.
Of course, this is due to the balance between the base paper and the rubber, in other words, it is
possible to select a wide range of physical properties.
[0044]
Therefore, the present invention may be applied not only to the center cap but also to other soft
speaker components and diaphragms as well as other speaker components that affect the sound
pressure frequency characteristics such as edges and dampers.
[0045]
As described above, according to the speaker center cap and the method of manufacturing the
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same of the present invention, a natural material such as wood pulp which can be selected
relatively freely is used as the base, A short cut fiber or pulp of thermoplastic resin which melts
at a temperature not higher than the vulcanization temperature of rubber described later is
compounded and vulcanized at the same time as being integrated in a molten state, and this
integrated member is a paper or rubber alone Since the internal loss is further enhanced as
compared with the internal loss of (1), the resonance frequency is lowered, so that the influence
on the sound pressure frequency characteristic can be eliminated.
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