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JP2000004496

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DESCRIPTION JP2000004496
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
diaphragm for an electroacoustic transducer having a multilayer structure manufactured using
an injection molding method.
[0002]
2. Description of the Related Art The physical properties required of diaphragms for
electroacoustic transducers such as speakers are high in specific modulus (E / .rho.) And specific
flexural rigidity (E / .rho.3), and appropriate internal loss is required. It is resistant to mechanical
fatigue and has good weather resistance. Furthermore, in recent years, waterproofness has
become one of the important characteristics, especially for vehicles. In order to meet such
demands, materials such as various metals, ceramics, synthetic resins, synthetic fibers, natural
cellulose fibers, and more recently microbial cellulose fibers using biotechnology have been
proposed, and various processing methods are used. Has been processed and used.
[0003]
Among them, metals and ceramics have relatively high elastic modulus but high density and low
internal loss, so they are relatively excellent for high-frequency reproduction, but low to midranges where light weight and high rigidity are required. And unsuitable for the whole band.
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Also, so-called paper diaphragms using cellulose fibers such as wood pulp as the main raw
material are relatively lightweight and have appropriate elastic modulus and internal loss, and
there are various manufacturing methods and designs. Because of its high degree of freedom, it
has long been used as a balanced diaphragm.
[0004]
However, this paper diaphragm also has a limited elastic modulus, poor waterproofness, and
mainly uses natural fibers, so the number of manufacturing processes is also limited. There are
problems such as many complexity and large variations. On the other hand, in recent years,
synthetic resin diaphragms are mainly formed using an injection molding method, mainly using
an olefin-based resin such as polypropylene as a base and mixing fillers such as mica and carbon
fibers. This synthetic resin diaphragm by injection molding can be said to be an excellent
diaphragm because it can be manufactured inexpensively with less variation, not to mention
waterproofness, but it can be said that it is an excellent diaphragm, but the type and filling
amount of fillers that can be mixed in the manufacturing process The low degree of design
freedom is a drawback.
[0005]
The present invention has been made in view of these points, and it is possible to increase the
degree of freedom in the design of injection molded synthetic resin diaphragms, and to provide a
diaphragm for electroacoustic transducers having excellent characteristics with a multilayer
structure. Intended to be provided.
[0006]
SUMMARY OF THE INVENTION In a synthetic resin diaphragm manufactured using an injection
molding method, a diaphragm for a surface layer, which has been molded into a predetermined
shape in advance, is inserted in a mold, After providing a mold gap, the material for the
diaphragm for the surface layer and another injection material are injected, and at least two or
more layers of different materials are provided in the thickness direction, and the electroacoustic
characteristics of the multilayer structure having excellent characteristics A transducer
diaphragm is obtained.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION In order to solve the above-mentioned
problems, the diaphragm for electro-acoustic transducer of the present invention comprises
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2
inserting a diaphragm for surface layer previously formed into a predetermined shape into at
least one mold. Then, move the mold to a predetermined position to provide a predetermined
mold gap, inject an injection material different from the material of the diaphragm for the surface
layer into the space using injection molding, and move in the thickness direction It is
characterized in that at least two or more layers of different materials are provided.
[0008]
Also, it is characterized in that the mold gap is formed to be larger than the thickness originally
intended to be obtained, and it is molded to a predetermined thickness by further pressing
during or after injection of the injection material. There is.
Furthermore, the diaphragm for surface layer is characterized in that an adhesive is applied.
[0009]
Also, it is characterized in that the front and back two surface layer diaphragms are bacterial
cellulose, and the injection material filled between them is polypropylene.
Furthermore, the diaphragm for the surface layer is poly-p-phenylene-terephthalamide, and the
injection material through the adhesive is poly-methylpentene.
[0010]
Embodiments of the present invention will be described below with reference to the drawings.
Although the embodiment is a free edge type diaphragm, it is needless to say that it can be
applied to a fixed edge type. FIG. 1 is a cross-sectional view of a multi-layered electroacoustic
transducer diaphragm according to the present invention. In the figure, 1 is a diaphragm for an
electroacoustic transducer, 2 is an edge, 3 is a diaphragm main body, 4 is a diaphragm for
surface layer, and 5 is an injection material. The injection material 5 between the two surface
layer diaphragms 4 is made of a material different from that of the surface layer diaphragm 4.
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Therefore, the diaphragm main body 3 has a three-layer structure, and has excellent
characteristics of a multilayer structure.
[0011]
A first embodiment of the present invention will be described with reference to FIGS. 2, 4 and 5.
FIG. FIG. 2 is a cross-sectional view of a diaphragm main body constituting the diaphragm for
electro-acoustic transducer in the first embodiment of the present invention, and FIG. 4 is a
diaphragm main body constituting the diaphragm for electro-acoustic transducer according to
the present invention. It is a figure which shows a manufacturing process. In the figure, 4 is a
diaphragm for surface layer made of bacterial cellulose, and 5 is an injection material made of
polypropylene. Further, 10 is a male mold and 11 is a female mold.
[0012]
【0012】1. Preparation of diaphragm 4 for surface layer 1a Water of about twice mass
was added to bacterial cellulose obtained from microorganisms, and the mixture was
disintegrated for 3 minutes with a mixer to prepare a pulp slurry. 1b 1a The pulp slurry prepared
in 1a is formed into a predetermined shape by wet sheet-forming method, adjusted to a water
content of about 80%, and then pressurized heat drying with a predetermined die (120 ° C., 2
kg / cm 2, 60 seconds And two diaphragms 4 for the surface layer having a thickness of about
70 .mu.m. A hole (φ 10 mm) for gate was made in the center of the surface layer diaphragm 4
manufactured in 1c 1b.
[0013]
【0013】2. Injection molding 2a 1c. Insert the two surface layer diaphragms 4 prepared in
the above into the male and female molds 10 and 11 with a predetermined shape previously
attached to the injection molding machine (see FIG. 4, a), and It fixed to the mold by the vacuum
adsorption device of (refer to FIG. 4, b). 2b The mold is moved to a predetermined position, and
after providing a space (see FIG. 4, c) larger than the mold gap that is originally intended to be
obtained, polypropylene which is injection material 5 injected in advance into the injection
molding machine (Mitsubishi Polypro BC2A) is injected (see FIG. 4, d), and the injected
polypropylene is pressed before it solidifies (see FIG. 4, e), and a three-layer structure of a
predetermined thickness (about 300 μ) The diaphragm main body 3 (see FIG. 4, f) was obtained.
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4
[0014]
FIG. 5 is a frequency-sound pressure characteristic diagram comparing a speaker using the
diaphragm for electro-acoustic transducer according to the present invention with a speaker
using the conventional diaphragm for electro-acoustic transducer. In the figure, the solid line A is
the characteristic according to the first embodiment, the solid line B is the characteristic
according to the second embodiment, and the broken line C is the characteristic according to the
conventional example. 3. The diaphragm body 3 of the three-layer structure obtained in the
performance check 3a 2b is punched out to a predetermined dimension, and the foamed rubber
edge formed in the predetermined shape is bonded to obtain the diaphragm 1 for an
electroacoustic transducer having the shape of FIG. The The diaphragm 1 for an electroacoustic
transducer obtained in 3b 3a was incorporated into a speaker with a diameter of 13 cm 2 and
the frequency-sound pressure characteristic (see the solid line A in FIG. 5) was measured.
Further, the material and the forming process were the same as those described above, a plate
having a flat shape was produced, and physical properties were measured using a vibration lead
method. For comparison, a material (Kuraray MRP 230) made of 70% polypropylene and 30%
mica was molded with the same injection molding machine and mold. Of course, the other steps
and materials were the same as in the first embodiment. The frequency-sound pressure
characteristics (see FIG. 5-dashed line C) were measured. Regarding physical properties, as
shown in Table 1, the first embodiment has high specific elastic modulus (sound velocity) and
high specific flexural rigidity as compared with the conventional product, and further has a
suitable internal loss. it can. The frequency-sound pressure characteristics support the height of
the physical property value, and as shown in FIG. 5, the high-range reproduction limit is extended
in Example 1 as compared with the conventional product, and the superior performance is
provided.
[0015]
FIG. 3 is a cross-sectional view of a diaphragm main body constituting a diaphragm for an
electroacoustic transducer according to a second embodiment of the present invention. In the
figure, 7 is a diaphragm for surface layer made of PPTA, 8 is an injection material made of
polypropylene, and 9 is an adhesive.
[0016]
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【0016】1. Preparation of diaphragm 7 for surface layer 1 A 50 μm thick poly-paraphenylene terephthalamide (PPTA) film is formed into a predetermined shape at 350 ° C., 8 kg /
cm 2 for 30 seconds, and diaphragm 7 for surface layer is formed. Made. The adhesive 9 was
applied to the back surface (convex surface) of the diaphragm 7 for a surface layer manufactured
in 1b 1a. 2. The diaphragm 7 for surface layer prepared by injection molding 2a 1b was
inserted into a mold (convex) having a predetermined shape previously attached to the injection
molding machine, and fixed to the mold by a vacuum suction device in the mold. . 2b Move the
mold to a predetermined position, create a space larger than the mold gap originally intended to
be obtained, and then put polymethylpentene (Mitsui Petrochemicals Co., Ltd. TPXMX-004),
which has been charged in advance into the injection molding machine. After the injection, and
further, the injected polymethylpentene was not solidified, it was pressed to obtain a diaphragm
body 6 having a two-layer structure of a predetermined thickness (about 300 μ).
[0017]
【0017】3. The diaphragm body having a two-layer structure obtained in the performance
check 3a 2b was punched into a predetermined size, and the foamed rubber edge formed into a
predetermined shape was bonded to obtain an electroacoustic transducer diaphragm of the
shape of FIG. The diaphragm body 6 obtained in 3b 3a was incorporated into a 13 cm-aperture
speaker, and the frequency-sound pressure characteristics (see the solid line B in FIG. 5) were
measured. Further, the material and the forming process were the same as those described
above, a plate having a flat shape was produced, and physical properties were measured using a
vibration lead method. For comparison, a material (Kuraray MRP 230) made of 70%
polypropylene and 30% mica as in the first embodiment was molded by the same injection
molding machine and mold. Of course, the other steps and materials were the same as in the
second embodiment. With regard to the physical properties, as shown in Table 1, the second
embodiment is estimated to be an excellent diaphragm because it has a high specific elastic
modulus (sound velocity), a high specific flexural rigidity, and a suitable internal loss compared
to the conventional product. it can. The frequency-sound pressure characteristics (see FIG. 5-solid
line B) support the height of the physical property values, and as shown in FIG. 5, the second
embodiment has a higher reproduction limit than the conventional product (see FIG. Extend and
provide excellent performance.
[0018]
【0018】
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[0019]
Various combinations are possible other than the embodiment, for example, one surface layer is
made of aluminum and the other surface layer is made of plant cellulose fiber, so-called paper,
and the injection material constituting the intermediate layer is carbon. A three-layered structure
made of fiber-filled polypropylene can also be produced.
Other materials to be inserted include metals such as titanium and magnesium and alloys thereof,
polyethylene terephthalate, polybutylene terephthalate, polysulfone, polyether sulfone,
polyphenylene sulfide, polyimide, polyethylene naphthalate, polycarbonate, acrylonitrilebutadiene-styrene three-way material Copolymers, synthetic resins such as polyethylene,
polyamide, polystyrene, liquid crystal polymers, and alloys thereof, and ceramics can be used,
and materials to be injected include polyethylene terephthalate, polybutylene terephthalate,
polysulfone, polyether sulfone, polyphenylene sulfide, Polyimide, polyethylene naphthalate,
polycarbonate, acrylonitrile-butadiene-styrene ternary copolymer Body, polyethylene, polyamide,
polystyrene, synthetic resins and their alloys, such as liquid crystal polymers can be used.
[0020]
According to the present invention, it is possible to increase the degree of freedom in the design
of an injection-molded synthetic resin diaphragm and to provide a diaphragm with excellent
characteristics which has a multilayer structure. The multilayer structure diaphragm can make
full use of the characteristics of each material by arranging layers of different materials in the
thickness direction, and further, it has excellent characteristics due to the physical effect of
arranging layers. Can provide a diaphragm of For example, even if it is highly elastic, its density
is high and its internal loss is small, so a material that could not be used except for high band
reproduction is made a surface layer, and the inside is not so elastic modulus, but relatively
dense The three-layer diaphragm made of a material having a low internal loss and a high
internal loss is an ideal diaphragm having a high specific elastic modulus, a high specific flexural
rigidity, and a suitable internal loss. In addition, even in terms of weatherability, by arranging a
material with good weatherability on the surface, the material on the back and inside can be
protected, so materials that can not be used conventionally due to problems with weatherability
should be used effectively. Can. Further, in the case where expensive ultraviolet light absorbers
and the like are added, the cost can be reduced because these additives do not need to be added.
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[0021]
Brief description of the drawings
[0022]
1 is a cross-sectional view of a multi-layered electro-acoustic transducer diaphragm according to
the present invention.
[0023]
2 is a cross-sectional view of the main body of the diaphragm constituting the diaphragm for
electroacoustic transducer in the first embodiment of the present invention.
[0024]
3 is a cross-sectional view of the main body of the diaphragm constituting the diaphragm for
electro-acoustic transducer in the second embodiment of the present invention.
[0025]
4 is a diagram showing a manufacturing process of the diaphragm body constituting the
diaphragm for electro-acoustic transducer according to the present invention.
[0026]
5 is a frequency-sound pressure characteristic diagram comparing the speaker using the
diaphragm for electro-acoustic transducer according to the present invention and the speaker
using the conventional diaphragm for electro-acoustic transducer.
[0027]
Explanation of sign
[0028]
Reference Signs List 1 diaphragm for electroacoustic transducer 2 edge 3 diaphragm main body
4 diaphragm for surface layer 5 ejection material 6 diaphragm main body 7 diaphragm for
surface layer 8 ejection material 9 adhesive 10 male die 11 female die
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