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JP2005328297

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DESCRIPTION JP2005328297
PROBLEM TO BE SOLVED: To obtain a diaphragm of a speaker which can be made high in
rigidity by reducing density and widening a reproduction frequency range from a low range to a
high range. A diaphragm of a speaker having a foam structure by dissolving carbon dioxide gas
or nitrogen gas in a molten state of a resin made of an injection moldable thermoplastic polymer
material and performing injection molding at an ultra-high speed. And a foam shape is disposed
in parallel to the flow direction of the resin inside the first and second skin layers 3a and 3b on
the other surface side and the first and second skin layers 3a and 3b respectively. In contrast,
first and second oriented micro-foamed layers 2a and 2b having a cylindrical shape with a length
of 2 or more, and a core portion for reinforcing the foaming direction inside the first and second
oriented micro-foamed layers 2a and 2b And a five-layer structure with the reinforced foam layer
1 of FIG. [Selected figure] Figure 1
Speaker diaphragm and method of manufacturing speaker diaphragm
[0001]
The present invention relates to a speaker diaphragm and a method for manufacturing a speaker
diaphragm, in which a reproduction frequency range from a low range to a high range is
expanded.
[0002]
Generally, in the diaphragm of a speaker designed to expand the reproduction frequency range
from low to high range, the specific elastic modulus E / ρ (E is elastic modulus, ρ is density
(specific gravity) to expand the piston movement area Is required to have a large internal loss for
smoothing the frequency characteristics.
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[0003]
Conventionally, in order to improve the elastic modulus, a material in which a high elastic fiber
or filler is filled in a polypropylene material having a relatively large internal loss is often used as
a material of a diaphragm obtained by injection molding or sheet molding.
[0004]
However, since the specific gravity of this material increases with the increase of the amount of
additives such as high elastic fibers and fillers, the improvement of the specific elastic modulus is
suppressed, and at the same time, the flow length of the resin decreases in injection molding and
thin-wall filling There is a limit to the improvement of both physical properties because
[0005]
Therefore, in order to improve the specific elastic modulus, conventionally, a chemical foaming
agent is added to a polypropylene material, and this polypropylene material is foamed to reduce
the density to enhance the rigidity (Patent Document 1).
[0006]
Moreover, the diaphragm which consists of an injection-foaming molded object which combined
the injection molding, the chemical foaming agent, and the reinforced fiber is proposed (patent
document 2).
According to the description of this patent document 2, the effect of reinforcing the skin layer is
created by causing the foam cells inside the foam layer to foam longitudinally in the surface
thickness direction during injection molding.
[0007]
On the other hand, in recent years, as a method of forming a micropore foam cell, Patent
Document 3 discloses a microcellular technology in which a supercritical fluid is used and foam
density is uniformly dispersed at 10 <9> / cm <3> or more.
[0008]
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A crystalline thermoplastic sheet is impregnated with supercritical carbon dioxide gas using the
technique disclosed in this patent document 3, and a microcellular sheet uniform to about 10
μm is made simultaneously with pressure release, and this sheet-formed diaphragm is a patent
document 4).
The diaphragm described in Patent Document 4 is more uniform than the diaphragm of the
conventional foam sheet, and is excellent in appearance.
[0009]
Patent No. 3238693 gazette JP, 8-340594, A JP 26 25 576 gazette JP, 2002-30039, A
[0010]
However, in the invention described in Patent Document 1, although weight reduction (small
density (specific gravity)) is realized due to foaming, the variation of the foam diameter is large,
and the foaming ratio is also limited to about 3 times.
The relative bending stiffness value of the diaphragm is expressed by the Young's modulus
(elastic modulus) and the cube root of the thickness, so the effect of triple the thickness is large.
[0011]
However, since the diameter of the foam cell is large due to the foaming by the chemical foaming
agent and the wall surface of the foam cell is thin, the decrease of the Young's modulus is
remarkable and the expected improvement of the frequency characteristics can not be expected.
In addition, there is a disadvantage that the foam form is not uniform and it is difficult to make a
product excellent in appearance.
[0012]
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Further, in the case of Patent Document 2 as well, it is extremely difficult to control the size of
the foamed cells to a large size such as several hundreds μm and to form a uniformly foamed
state over the entire surface because of foaming by a chemical foaming agent.
[0013]
Moreover, although the reinforcement fiber is taken in in order to reinforce in description of
patent document 2, this reinforcement fiber does not reinforce an internal foaming cell, the
improvement effect of a specific elastic modulus has a limit, and improvement of a frequency
characteristic can be expected. Absent.
[0014]
Also, when trying to foam a thin diaphragm using a chemical foaming agent, the time for foaming
of the chemical foaming agent decomposed at the time of resin melting is extremely short, and
the foaming power is weak, so the mold temperature is raised. There are many inconveniences in
manufacturing, such as opening the mold instantaneously.
[0015]
In the invention described in Patent Document 4, since the unfoamed crystalline resin used is a
single material such as polyester resin, the elastic modulus is lower than that of the conventional
diaphragm material, and the elastic modulus is further increased by foaming. Is declining.
Therefore, although the specific gravity is small, the decrease in elastic modulus is large, the
specific elastic modulus is not large, and it can not be expected to improve the frequency
characteristics of the speaker using this diaphragm.
[0016]
An object of the present invention is to obtain a diaphragm of a speaker capable of reducing the
density and achieving high rigidity and expanding the reproduction frequency range from the
low tone range to the high tone range.
[0017]
The diaphragm of the speaker of the present invention is a diaphragm of a speaker having a
foam structure by dissolving carbon dioxide gas or nitrogen gas in a molten state of a resin made
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of an injection-moldable thermoplastic polymer material and performing injection molding at an
ultra-high speed. A foam shape is disposed in parallel to the flow direction of the resin on the
first and second skin layers on one surface side and the other surface side and inside of each of
the first and second skin layers. Five layers of a first and a second oriented micro-foamed layer
having a cylindrical shape with a length of 2 or more, and a reinforced foam layer of a core
portion reinforcing the foaming direction inside the first and the second oriented micro-foamed
layer It consists of a structure.
[0018]
Further, according to the method of manufacturing the diaphragm of the speaker of the present
invention, carbon dioxide gas or nitrogen gas is dissolved in a molten state of a resin made of an
injection moldable thermoplastic polymer material, and injection molding is performed at an
ultra high speed. A cylindrical oriented fine foam layer is formed in the vicinity of the surface
layer and a reinforced foam layer is formed in the core portion.
[0019]
According to the present invention, since carbon dioxide gas or nitrogen gas is dissolved in a
molten state of a resin made of an injection moldable thermoplastic polymer material and
injection molding is performed at an ultra high speed to form a diaphragm of a speaker having a
foam structure, the appearance is good. High foaming ratio For example, high foaming of about 8
times is realized, low specific gravity and high rigidity of, for example, about 0.103 can be
realized, and a speaker diaphragm is obtained in which the reproduction frequency range from
the low range to the high range is extended be able to.
[0020]
Hereinafter, with reference to the drawings, an example of the best mode for carrying out the
diaphragm of the speaker of the present invention and the method of manufacturing the
diaphragm of the speaker will be described.
[0021]
FIG. 4 shows a configuration example of an injection molding machine for manufacturing the
diaphragm of the speaker according to the present embodiment.
The clamping pressure between the movable mold 21 held by the movable platen 24 of the mold
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20 forming the diaphragm of the speaker in the injection molding machine shown in FIG. 4 and
the fixed mold 22 held by the fixed platen 25 is , And a mold clamping mechanism 23 controlled
by a mold clamping pressure control unit (not shown).
[0022]
The injection port of the injection device 26 is inserted into the injection port of the fixed side
mold 22.
The injection device 26 is controlled by injection conditions controlled by an injection process
control unit (not shown).
Further, information on the molding process is output from the injection device 26 side, and the
mold clamping pressure control by the mold clamping pressure control unit according to the
information and the information on the distance on the movable platen 24 side, etc. Is done.
[0023]
The specifications of the injection molding machine in this example are: Maximum injection
pressure: 2800 kg / cm <2> Maximum injection speed: 1500 mm / sec Rise speed: 10 msec
Clamping force: 160 tons Screw diameter: Ultra-high-speed injection molding machine adjusted
to Φ 32 mm It is.
[0024]
In FIG. 4, reference numeral 27 denotes a carbon dioxide gas cylinder containing carbon dioxide
gas, and the carbon dioxide gas from the carbon dioxide gas cylinder 27 is brought to a
supercritical state (7.4 MPa or more, 31.degree. C. or more). The critical state generation device
28 feeds the injection port side of the input portion of the hopper 29 of the plasticizing screw 26
a of the injection device 26 and the fixed mold 22.
[0025]
In this case, a resin made of an injection-moldable thermoplastic polymer material from the
hopper 29, for example, a special polyolefin resin obtained by multistage polymerization of an
ultra-high molecular weight polyolefin and a high molecular weight olefin in which an alignment
layer is easily formed when injected (Mitsui Chemical Co., Ltd.) is introduced, and is heated and
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melted by the plasticizing screw 26a.
[0026]
Carbon dioxide gas is pressed into the cylinder of the plasticizing screw 26a of the injection
device 26, and the carbon dioxide gas penetrates and dissolves in the molten resin in the
cylinder.
[0027]
In this case, if the pressure of the carbon dioxide gas from the carbon dioxide gas cylinder 27 is
lower than the pressure of the resin in the molten state, the press-in becomes difficult.
For this reason, it is necessary to adjust the carbon dioxide gas pressure by the pressure rising
pump of the supercritical state generation device 28 while detecting the pressure of the resin,
and press-in.
[0028]
The carbon dioxide gas is not particularly limited as long as it is in a gas or supercritical state,
but it is desirable that the carbon dioxide gas pressure be as high as it is necessary to increase
the dissolving power of the carbon dioxide gas in the resin.
However, an increase in pressure more than necessary is not preferable because it causes the
occurrence of a large blister on the surface of the molded article.
[0029]
Further, since the mold 20 is injected at a high pressure in a state in which carbon dioxide gas is
dissolved in the molten resin, the mold 20 is equivalent to the same carbon dioxide gas in a state
where the fixed side mold 22 and the movable side mold 21 are closed. It is good to keep the
pressure of
[0030]
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In this case, it is desirable that the mold be packed and sealed with rubber or the like so that the
carbon dioxide gas dissolved from the mold 20 does not escape when the molten resin is injected
into the mold 20.
[0031]
In addition, the mold clamping mechanism 23 of this injection molding machine can be opened
to a desired thickness instantaneously after resin filling in order to control the thickness of a
reinforced foam layer described later using a hydraulic direct pressure type or an electric type. It
was a thing.
[0032]
With the movable-side mold 21 and the fixed-side mold 22 of the mold 20 closed, a cone-shaped
diaphragm having an outer diameter of 115 mm and a thickness of 0.35 mm as shown in FIG. 3
is obtained. The shape is made to spread uniformly from the gate to the thin diaphragm portion
through the film gate.
[0033]
The diaphragms of the speakers of Examples 1 to 4 as shown in Table 1 were formed using the
injection molding machine shown in FIG. 4 described above.
The diaphragms of the loudspeakers of Examples 1 to 4 are obtained by multistage
polymerization of ultra high molecular weight polyolefin and high molecular weight olefin, which
are easy to form an alignment layer when injected, as a resin made of an injection moldable
thermoplastic polymer material. Special polyolefin resin, Lubmer L 3000 (manufactured by
Mitsui Chemicals, Inc.) was used.
[0034]
Injection conditions for charging this resin from the hopper 29 are as follows: Plasticizing screw
26 a part: 240 ° C. Injection speed: 1500 mm / sec Mold temperature: 45 ° C. Carbon dioxide
pressure: 8 MPa
[0035]
In Example 1, a resin in a molten state in which carbon dioxide gas is dissolved under the above
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conditions is filled in a state where the movable side mold 21 and the fixed side mold 22 are
closed, and after holding pressure, the movable side mold 21 is assembled as Injection molding
was performed under the condition of 5 mm opening to obtain a diaphragm.
[0036]
The diaphragm of this Example 1 was good in appearance due to the formation of a skin layer.
As shown in Table 1, the thickness of this diaphragm is 0.905 mm, the expansion ratio is 0.905
÷ 0.35 = 2.58 times, the specific gravity is 0.264, the internal loss is 0.020, and the bending is
The stiffness ratio was 2.8.
[0037]
In the second embodiment, a resin in a molten state in which carbon dioxide gas is dissolved is
filled in a state in which the movable side mold 21 and the fixed side mold 22 are closed under
the above conditions, and the movable side mold 21 is opened 2 mm after pressure holding
Injection molding was performed under the conditions to obtain a diaphragm.
[0038]
The diaphragm of this Example 2 was good in appearance due to the formation of a skin layer.
As shown in Table 1, the thickness of this diaphragm was 1.852 mm and the expansion ratio was
5.29 times, the specific gravity was 0.153, the internal loss was 0.023, and the bending rigidity
ratio was 15.8. .
[0039]
The frequency characteristic of the speaker using the diaphragm of this embodiment 2 was a
good one for widening the reproduction frequency range as shown by curve a in FIG.
[0040]
In the third embodiment, a resin in a molten state in which carbon dioxide gas is dissolved is
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filled in a state in which the movable side mold 21 and the fixed side mold 22 are closed under
the above conditions, and after holding pressure, the movable side mold 21 is opened 3 mm.
Injection molding was performed under the conditions to obtain a diaphragm.
[0041]
The diaphragm of this Example 3 was excellent in appearance due to the formation of a skin
layer.
As shown in Table 1, the thickness of this diaphragm was 2.795 mm and the expansion ratio was
about 8 times, and the specific gravity was 0.103, the internal loss was 0.026, and the flexural
rigidity ratio was 46.4. .
[0042]
Further, the frequency characteristics of the speaker using the diaphragm of Example 3 were
good as shown by the curve b in FIG.
[0043]
In Example 4, a resin in a molten state in which carbon dioxide gas is melted under the above
conditions is filled in a state where the movable side mold 21 and the fixed side mold 22 are
closed, and after holding pressure, the movable side mold 21 is opened 4 mm. Then, injection
molding was carried out to obtain a diaphragm.
[0044]
The diaphragm of this Example 4 was good in appearance due to the formation of a skin layer.
As shown in Table 1, the thickness of this diaphragm is 3.453 mm and the expansion ratio is
9.87 times, the internal loss is 0.028, the specific gravity is 0.101 and lighter than the paper
diaphragm, and the bending rigidity ratio is High rigidity was realized in 62.0.
[0045]
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Moreover, a comparative example is a diaphragm which does not have foaming which used the
same metal mold and was injection-molded by resin which does not melt carbon dioxide gas.
[0046]
The thickness of the diaphragm of this comparative example is 0.35 mm, the specific gravity is
0.952, the Young's modulus is 7.90 × 10 <9> Pa, the internal loss is 0.015, and the flexural
rigidity ratio is 1.
The frequency characteristic of the speaker using the diaphragm of this comparative example is
as shown by a curve d in FIG.
[0047]
[0048]
Further, FIG. 1 shows a schematic cross-sectional view in the direction perpendicular to the flow
direction of the resin of the diaphragm of the first to fourth embodiments (arrow X direction in
FIG. 3). FIG. 2 shows the diaphragm of the first to fourth embodiments. The flow direction (arrow
Y direction of FIG. 3) of a resin is a cross-sectional schematic diagram.
[0049]
The structures of the diaphragms of Examples 1 to 4 which can be seen from FIGS. 1 and 2 are
the reinforced foam layer 1 of the core portion, and the oriented fine foam layers 2a and 2b
formed on both surface sides of the reinforced foam layer 1 of this core portion. The five-layer
structure is composed of skin layers 3a and 3b on the surface side of each of the oriented fine
foam layers 2a and 2b.
[0050]
The skin layers 3a and 3b are formed by cooling with the molds 20, 21 and 22, respectively.
[0051]
The oriented fine foam layers 2a and 2b are cylindrical layers having a bubble diameter of 50
μm or less and a bubble length of at least twice the diameter, and a large number of bubble
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layers dispersed in the resin orientation part. It suppresses the rate decrease and acts as a
cushion between the skin layers 3a and 3b and the reinforced foam layer 1 of the core portion.
[0052]
In particular, the reinforced foam layer 1 in the core part may break through the skin layers 3a
and 3b because the gas maintaining the high pressure dissolved therein foams and may be
exposed on the surface, but the oriented fine foam layers 2a and 2b It also works to prevent
[0053]
As in this example, when the diaphragm is thin-walled and injection-molded at an ultra high
speed, oriented fine foam layers 2a and 2b are formed within the skin layers 3a and 3b, which
have a sensible force, to be specifically foamed in the resin flow direction.
[0054]
In addition, the reinforced foam layer 1 of the core part is filled with resin in the molds 20, 21
and 22 in the high pressure gas state, and then the movable side mold 21 is opened by a
necessary amount at once to maintain strength in the thickness direction. Take structure.
In particular, unlike the foaming by a chemical foaming agent, a thin, high foaming can be
realized with a foaming ratio of about 3 to 10 times.
[0055]
According to this example, carbon dioxide gas is dissolved in the molten state of a resin made of
an injection moldable thermoplastic polymer material, for example, a special polyolefin resin, and
ultra high speed injection molding is performed to form a diaphragm of a speaker having a foam
structure. High expansion ratio, for example, high expansion of about 3 to 10 times, low rigidity
with high specific gravity, for example, about 0.101 to 0.264, and a diaphragm of a speaker
having improved reproduction frequency characteristics. Can.
[0056]
In the above example, carbon dioxide gas is dissolved in the molten resin, but nitrogen gas can be
used instead of carbon dioxide gas.
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[0057]
Novatec PPBC10 (manufactured by Nippon Polypropylene Corporation) was used as a resin made
of an injection moldable thermoplastic polymer material when nitrogen gas was used instead of
carbon dioxide gas in the above example.
[0058]
The same injection molding machine as that shown in FIG. 4 is used, and the injection conditions
are as follows: Plasticizing screw 26a: 200 ° C. Injection speed: 1500 mm / sec Mold
temperature: 45 ° C. Nitrogen gas pressure: 10 MPa; A diaphragm was formed in the same
manner as described above using.
[0059]
When this nitrogen gas is used, the same function and effect as when carbon dioxide gas is used
can be obtained, and the frequency characteristic when a speaker is configured using this
diaphragm is good as shown by curve c in FIG. It was a thing.
[0060]
The present invention is of course not limited to the above-described example, and various other
configurations can be adopted without departing from the scope of the present invention.
[0061]
It is a cross-sectional schematic diagram of the perpendicular | vertical direction of the resin flow
direction of the diaphragm of this invention speaker.
It is a cross-sectional schematic diagram of the resin flow direction of the diaphragm of this
invention speaker.
It is a front view showing an example of a diaphragm of a speaker.
It is a block diagram of the injection molding machine by this example.
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It is a diagram which shows a frequency characteristic.
Explanation of sign
[0062]
1. Reinforcement foam layer, 2a, 2b .. Oriented fine foam layer, 3a, 3b .. Skin layer, 20 .. Mold, 21
.. Movable side mold, 22 .. Fixed side mold, 26 .. Injection apparatus, 26a: plasticizing screw, 27:
carbon dioxide gas cylinder, 28: supercritical state generator
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