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JPS59298

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DESCRIPTION JPS59298
[0001]
The present invention relates to a method of manufacturing a loudspeaker diaphragm having a
circular sandwich structure. Recently, a speaker diaphragm of a sandwich structure has been
developed, in which skin materials are adhered to both the front and back sides of a lightweight
and highly rigid core material. The speaker diaphragm having such a configuration is
characterized in that the bending rigidity is extremely large as compared with a conventional
single-sheet cone-type speaker diaphragm. Therefore, the divided resonance frequency of the
diaphragm is increased, and the reproduction band can be extended. An aluminum honeycomb
structure is generally used as a core material of this sandwich structure. However, the aluminum
honeycomb structure has the drawback of being expensive because it requires many
manufacturing steps. As an alternative to this aluminum honeycomb core, a corrugated core
material 2 as shown in FIG. 1 obtained by press forming or vacuum forming a plastic film has
been proposed. Although this core material can be manufactured by one molding, the number of
steps can be significantly reduced, but it also has the disadvantages described below. FIG. 2 is a
cross-sectional view of a press mold for forming the core material 2 shown in FIG. 1, in which 1
is an upper mold and 1 'is a lower mold. In the radial core 2 shown in FIG. 1, since the pitch P1 of
the circumferential direction of the outermost circumference is larger than the pitch P2 of the
circumferential direction of the inner circumference, the side 2a of the mountain has a twisted
shape. Therefore, it is very difficult to process a press die for press forming the core shown in
FIG. Also, the accuracy of the clearance between the upper mold 1 and the lower mold 1 'must be
smaller than the film thickness throughout the entire mold. For these reasons, the cost of the
press die is increased. In addition, the thickness 2b of the core material, which is related to the
magnitude of the bending rigidity of the diaphragm, is determined by the mold, and has a
drawback that the thickness 2b can not be freely controlled. 3 and 4 are principle diagrams in
the case of vacuum forming the core material 2 shown in FIG. 3 is a vacuum mold, 4 is a recess
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of the mold 3 and 5 is a suction hole. This vacuum forming method can be formed as shown in
FIG. 4 by placing the heated plastic film 2 on the mold 3 and exhausting the air of the recess 4
from the suction holes 5. In this method, the heated plastic film 2 contacts the film to the mold
38 with the start of suction, and the film in that portion is heat-removed and hardens
immediately, so its thickness is almost the same as that before molding Absent. When suction is
further continued, the film begins to deform along the recess 4 of the mold, and the film
gradually contacts the mold and hardens from a portion closer to the mold 3a.
Therefore, the thickness becomes thinner toward the bottom 3 b of the recess, and the thickness
of the portion in contact with the bottom 3 b becomes the thinnest. As described above, in the
vacuum forming method, the film thickness is distorted, and the side portion 2a which needs to
be thickened becomes thinner. Therefore, in order to make the thickness of the side portion 2a a
predetermined value, the film of molding must be made quite thick, and there is a drawback that
the weight of the whole diaphragm becomes heavy. Further, if the thickness 2b of the core
material is increased, the thickness of the film contacting the bottom 3b of the four parts
becomes extremely thin, and the film may be broken or the mold separation may be deteriorated.
The object of the present invention is to eliminate the disadvantages of the above molding
method and to obtain a core material having a predetermined thickness. Hereinafter, an
embodiment of the present invention will be described with reference to the drawings. FIGS. 5
and 6 are principle diagrams showing a first embodiment of the molding method of the core
material shown in FIG. 1 according to the present invention. 11 is an upper mold, 11a is an
upper mold plate-like plug, 11 'is a lower mold, 11'a is a lower mold plate-like plug, and the
distance between 11a and 11'a is the thickness of film 2 in comparison with Big enough. Using
this mold, as shown in FIG. 5, the heated plastic film 2 is held between the upper mold 11 and
the lower mold 11 'and pressed to obtain the core of the plastic film shown in FIG. FIG. FIG. 8 is a
plan view of the mold shown in FIG. 5, and plate-like plugs 11a and 11'a radially project from the
center. FIG. 9 shows a second embodiment according to the present invention, in which plate-like
plugs 12a and 12'a'e are formed in a mold 12.degree. 12 'so that the cross-sectional shape in the
circumferential direction of the core material becomes trapezoidal. . FIG. 10 shows a third
embodiment according to the present invention in which the tips of the plate-like plugs 13a and
13'a of the molds 13 and 13 'are rounded to make the cross-sectional shape in the
circumferential direction of the core material sinusoidal. It is. Also, as shown in FIG. 11, if the
radial shape of the plate-like lugs 14a and 14'a is a rectangular mold 14 ° 14 ', a core material
with parallel front and back can be obtained, and further By forming a tapered portion on the
plate-like plug 15a of the upper mold 15 as shown in FIG. 12, it is possible to obtain a core
material having a chi and e on the back side. In addition, said 1st. 2nd. Of course, the crosssections of the plate-like plugs 11'a + 11'a, 12a + 12'a, 13a + 13 "a according to the third
embodiment may be tapered. By bonding a skin material having a high modulus of longitudinal
elasticity to the front and back of the core material obtained in the above example. A loudspeaker
diaphragm with a high rigidity sandwich structure is obtained.
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According to the molding method of the core material according to the present invention
described above, first, the tips of the upper and lower mold plate-like plugs are in contact with
the heated Zolasch and Cu-film respectively to take away heat, so this part is rapid After cooling
and curing, the uncooled plastic film between the plate-like plugs is drawn and molded. For this
reason, in the molding method according to the present invention, there is no thickness
unevenness that occurs in vacuum molding, and it is possible to make the thickness uniform, and
it is possible to eliminate the unevenness of immediateness of the core material. Further, in the
mold according to the molding method of the present invention, since the upper and lower mold
plugs can be formed into a plate shape, it can be easily processed unlike the mold shown in FIG.
It can be made 9 at low cost. Furthermore, since there are few parts in which the molded product
and the mold are in surface contact, mold release from the molded product is very good. In
addition, although it was impossible to change the thickness of the core material related to the
rigidity of the diaphragm in the conventional mold, in the present invention, the upper mold
shown in FIG. 6, FIG. 9 and FIG. The thickness can be easily changed by changing the plate-like
plugs of the lower mold into the overlapping dimension 2 cf, so that core materials of various
thicknesses can be manufactured with one mold, and the minimum It is possible to determine the
optimum sandwich core in a short time at cost.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a partial perspective view of a corrugated core, FIG. 2 is a cross-sectional view showing a
conventional press die, and FIG.
Fig. 4 is the principle of vacuum forming, Fig. 5 and Fig. 6 are sectional views showing one
embodiment of the present invention, and Fig. 7 and Fig. 8 are upper and lower dies used in the
same embodiment. 9 is a sectional view showing another embodiment of the present invention,
and FIG. 10 is a sectional view showing still another embodiment of the present invention, and
FIGS. 11 and 12 are molds respectively. Is a diagram showing a cross section in the radial
direction of FIG. 2 ・ ・ ・ Plastic film (and molded core material), 11,12.13, 14.15 ・ Upper
mold, 1'l ', l 2', 13 ', 14', l 5 '-· · Lower mold , Lla. 12a, 13a, 14a, 15a...-Upper plug, 11'a, 12'a,
13'a, 14'a, 15 ', a ... lower plug. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5. Figure 6 Figure 7
'Figure 8 Figure 9 Figure 11
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