JP2014097645

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DESCRIPTION JP2014097645
An object of the present invention is to control the orientation direction of a resin by a rotational
molding technique using a synthetic resin, and to produce a cone-shaped molded product having
high mechanical strength despite its thinness and light weight, at low cost. Abstract: A method
for producing a molded article is provided, in particular, the specific elastic modulus E / ρ is
increased, the internal loss is increased, and a loudspeaker diaphragm having excellent acoustic
characteristics is provided. A molding is provided with a cavity for molding a rotationally
symmetrical conical molding 3 having a thin-walled cone or truncated cone, and having a
pouring portion 4 of molten resin on the top corresponding to the top of the conical molding.
The mold 1 is used to fill the cavity with the molten resin at the same time or at the same time as
filling, or immediately after the filling is completed, at least one of the inner part and the outer
part of the mold in the conical molded article is circumferentially rotated. The molecular
orientation of the resin was made to have components in both the generatrix direction and the
circumferential direction. It is optimal to form the speaker diaphragm with a liquid crystal
polymer. [Selected figure] Figure 1
Method of manufacturing conical shaped article and diaphragm for speaker
[0001]
The present invention relates to a method of manufacturing a conical molded product made of a
synthetic resin and whose orientation is controlled, and to a diaphragm for a loudspeaker
according to the method.
[0002]
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The diaphragm of the dynamic type speaker is required to have less natural vibration due to
divided vibration and resonance and to have high conversion efficiency.
For this reason, the diaphragm is made of a material having a specific elastic modulus E / ρ (E:
Young's modulus, ρ: density) as large as possible, and a suitably large internal loss in order to
smooth the frequency characteristics in the high range, that is, hard Light materials are used.
Moreover, it is also important that there is little aging deterioration. It is not easy to find a
material that fills all of these in high dimensions.
[0003]
Conventionally, cone paper is mainly used as a speaker diaphragm. In order to increase E / ρ, it
is molded using a composite material in which a plurality of materials such as carbon fiber and
biocellulose are mixed with paper pulp. In addition, synthetic resin materials such as polyester,
aramid and polypropylene have come to be used as means for improving the specific elastic
modulus of paper-based diaphragms, and these materials are used by bonding to honeycomb
structures and other substances. Used for low to medium tone units. In addition, a metal
diaphragm is also used, and in particular, a beryllium diaphragm has excellent characteristics.
Generally, metals are used mainly for high-pitched units because they have a higher specific
gravity than paper and have an excellent specific modulus but small internal loss.
[0004]
Patent Document 1 discloses a speaker diaphragm having an alignment of a liquid crystal
polymer inside with a thermoplastic aromatic polyester liquid crystal polymer as a material.
Then, as a method of manufacturing a speaker diaphragm, a material containing a thermoplastic
aromatic polyester liquid crystal polymer is heated and melted at a temperature higher than the
temperature at which the liquid crystal polymer is liquidized, and a predetermined pressure is
applied to the heated and melted material. It is disclosed that the solution is poured into a mold
maintained at a predetermined temperature in the region where the liquid crystal polymer
solidifies, and the multilayer alignment layer of the liquid crystal polymer is molded therein.
Here, it has injection part in the center, and a shaping ¦ molding part is shape ¦ molded by
injection molding using the mold which is a truncated cone shape.
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[0005]
The liquid crystal polymer has the property of molecular orientation with a slight shear force and
is strong in the molecular orientation direction due to its high orientation, but weak in the
direction orthogonal to the molecular orientation direction, and easily broken when it is thinned
Has the disadvantage of Therefore, in Patent Document 2, when forming a speaker diaphragm
using a liquid crystal polymer, the direction of flow of the liquid crystal polymer is on the surface
of the mold by partially forming a meandering groove on the surface of the mold. It is disclosed
that the strength is improved by meandering and meandering of the alignment of the liquid
crystal polymer.
[0006]
In Patent Documents 3 and 4, the molten resin is injected and filled into the mold at the same
time or at the filling stage, and further immediately after the filling is completed, it is rotated in
the circumferential direction by the rotating means equipped with the rotation control device.
There is disclosed a method of manufacturing a cylindrical injection molded article having means
for controlling an angle at which at least one of an inner side and an outer side of a mold rotates,
a rotational speed, a rotational torque and a rotational start time. Since the resin is oriented in
the circumferential direction, the cylindrical molded article obtained thereby has high mechanical
strength and there is no variation in strength due to portions of the molded article.
[0007]
Japanese Patent Publication No. 4-39279 Japanese Patent Application Laid-Open No. 4-77095
Japanese Patent No. 2537131 Japanese Patent No. 3185039
[0008]
In view of the above-described situation, the present invention aims to solve the problem by
controlling the molecular orientation direction of the resin by rotational molding technology
using a synthetic resin, so that the cone is high in mechanical strength despite being thin and
lightweight. The present invention provides a method of manufacturing a conical molded product
capable of mass-producing the molded product inexpensively, and in particular, increases the
specific elastic modulus E / ρ and increases the internal loss to obtain a speaker diaphragm
having excellent acoustic characteristics. It is in the point to offer.
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[0009]
In order to solve the above-mentioned problems, the present invention relates to a method for
producing a rotationally symmetric conical shaped article having a thin-walled cone or truncated
cone, comprising a cavity for shaping the conical shaped article, and Using a mold having a
molten resin injection portion at the top corresponding to the top of the green molded article,
filling the molten resin into the cavity at the same time or in a filling stage, and immediately after
the filling is completed, Production of a conically shaped article characterized in that at least one
of the inner part and the outer part of the mold is rotated in the circumferential direction, and
the molecular orientation of the resin has components in both the generatrix direction and the
circumferential direction. The method is configured (claim 1).
[0010]
Here, it is preferable to fill the cavity with the molten resin from the injection part of the mold by
injection molding (claim 2).
[0011]
And it is more preferable that the said resin is a liquid crystal polymer of a thermoplastic
aromatic polyester type (Claim 3).
[0012]
In particular, the conical shaped part is formed by a conical part, a closed part that blocks the top
of the conical part and intersects the center of rotation of the mold, and points radially outward
at the bottom of the conical part It is preferable to have a flange portion (claim 4).
[0013]
Then, using the conical molded product formed by the method for manufacturing a conical
molded product described above, a part of the conical molded product was cut off to
manufacture a speaker diaphragm having a cone shape (claim 5).
[0014]
Here, using a conical shaped article having a frusto-conical surface orthogonal to the center of
rotation of the forming mold at the top and a flange section directed radially outward at the
bottom, the closed section of the conical shaped article And the flange portion was cut to
produce a cone-shaped speaker diaphragm (claim 6).
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[0015]
According to the method of manufacturing a conical molded article of the present invention as
described above, there is provided a method of manufacturing a rotationally symmetric conical
molded article having a thin-walled cone or truncated cone, wherein a cavity for molding the
conical molded article Using a mold having a molten resin injection portion at the top
corresponding to the top of the conical molding, and filling the molten resin into the cavity at the
same time, or in a filling step, or immediately after the filling is completed Since at least one of
the inner part and the outer part of the mold in the conical molded product is circumferentially
rotated, and the molecular orientation of the resin has components in both the generatrix
direction and the circumferential direction, the conical molded product The molecular orientation
of the resin in the conical part of the product is twisted, which provides sufficient mechanical
strength even when molded into a thin wall, eliminates non-uniformity of the characteristics due
to the part of the molded product, and is excellent in shape stability. .
Here, "twist of molecular orientation" means that molecular orientation has an angle with respect
to the generatrix direction of the conical shaped article.
[0016]
In addition, when a liquid crystal polymer of thermoplastic aromatic polyester is used, since it is
excellent in fluidity at the time of molding, a thin molded product can be easily molded, and it is
oriented in one direction by a slight shear force. Since the molecular orientation of the resin has
components in the generatrix direction and the circumferential direction, molded articles having
high mechanical strength and high elastic modulus can be obtained even if thin.
[0017]
Then, by using a conical molded product formed by the above-described method for
manufacturing a conical molded product and cutting out a part of the conical molded product to
form a cone shape, a thin and high-strength speaker diaphragm is manufactured. be able to.
In particular, when manufactured using a liquid crystal polymer, E / ρ is high and internal loss is
large even when molded to be thin and lightweight, so that a speaker diaphragm having excellent
acoustic characteristics can be manufactured.
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[0018]
Here, a conical molded article having a conical portion, a closed portion that blocks the top of the
conical portion and intersects the center of rotation of the mold, and a flange portion directed
radially outward at the bottom of the conical portion If a cone-shaped loudspeaker diaphragm is
manufactured by cutting off the closed portion and flange portion of the conically shaped
product, only the conically shaped portion in which the mechanical properties of the conically
shaped product are stable can be used. In addition, it is possible to manufacture a speaker
diaphragm that is further excellent in acoustic characteristics.
[0019]
It is a simplified sectional view of the mold used for the manufacturing method of the conical
shaped article of the present invention.
It is a perspective view of a conical shaped article taken out from a forming die.
It is sectional drawing of a conical shaped article similarly.
It is a perspective view for description which shows the orientation direction of resin of the
conical-shaped molded article shape ¦ molded by this invention.
It is a perspective view of the diaphragm for speakers.
[0020]
The details of the present invention will be described below based on the embodiments.
FIG. 1 shows a mold using the rotational molding technique employed in the method for
producing a conical molded article of the present invention, and FIGS. 2 and 3 show a conical
molded article molded thereby, in which reference numeral 1 indicates a molded article. A mold,
2 indicates a cavity, and 3 indicates a conical shaped article, respectively.
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[0021]
The present invention relates to a method for producing a rotationally symmetric conical shaped
article having a thin-walled cone or truncated cone, comprising a cavity for shaping the conical
shaped article, and corresponding to the top of the conical shaped article. With the mold having
the injection part of the molten resin at the top, the molten resin is filled into the cavity at the
same time or at the filling stage, and immediately after the filling is completed, the inner part and
the outer part of the mold in the conical molding At least one of them is rotated in the
circumferential direction so that the molecular orientation of the resin has components in both
the generatrix direction and the circumferential direction.
[0022]
Here, the conical molded article 3 is molded by injection molding in which the molten resin is
filled from the injection portion 4 of the mold 1 to the cavity 2 by injection molding.
[0023]
Specifically, as shown in FIG. 1, the mold 1 has a rotationally symmetrical inner mold 5, a mold
main body 6 rotatably holding the inner mold 5, and the inner mold 5. And an end face of the
mold body 6 to form an outer mold 7 that forms a cavity 2.
Then, the inner mold 5 is rotatably inserted at a fixed position by the radial bearing 8 and the
movement restricting portion 9 in the axial direction with respect to the mold main body 6, and
the inner surface of the conical molding 3 is obtained. The inner molding surface of the tip to be
formed protrudes from the end face of the mold body 6, and a rotation means 10 is provided at
the base end.
The outer mold 7 has an outer molding surface that forms the outer surface of the conical
molded product 3 and is joined to the end surface of the mold body 6 to form the cavity 2.
Further, the conical molded product 3 can be taken out by releasing the mold from the end face
of the mold body 6.
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The injection portion 4 is formed to penetrate from the outer surface of the outer mold 7 to the
outer molding surface.
In addition, an ejector pin 11 for pushing out the conical molding 3 from the end face of the
mold body 6 is provided so as to be able to protrude and retract.
[0024]
In the present embodiment, as shown in FIGS. 2 and 3, the conical molded article 3 is a conical
portion 12 and a closed portion which blocks the top of the conical portion 12 and intersects the
center of rotation of the inner mold 5. 13 and a flange portion 14 directed radially outward at
the bottom of the conical portion 12. Here, the closed portion 13 is a frusto-conical surface
orthogonal to the rotation center of the inner mold 5. Further, the sprue 15 protruding to the
center of the closed portion 13 is a portion corresponding to the injection portion 4. When the
molten resin is filled from the injection portion 4 of the outer mold 7, first, it radially spreads to
the closed portion 13, then the conical portion 12 radially spreads to flow to the bottom portion,
and finally the flange portion 14 is filled. In order to uniformly fill the molten resin in the cavity
2, it is preferable to arrange the center of rotation of the conical shaped article 3 in the vertical
direction, but it may be arranged in the horizontal direction.
[0025]
Then, at the same time as the molten resin is injected into the cavity 2 of the mold 1 by injection
filling, or at the filling stage, or immediately after the filling is completed, the inner mold 5 is
rotated in the circumferential direction by the rotating means 10 A component in the
circumferential direction is provided in the molecular orientation direction of the resin. Here,
when the inner mold 5 is rotated, the magnitude (vector) of the component in the circumferential
direction of the molecular orientation direction is controlled by controlling the rotation angle,
rotation speed, rotation torque and rotation start time thereof. Do. The mold 1 is also provided
with the above-mentioned molecular orientation control means. This rotational molding
technique itself is known.
[0026]
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In the present embodiment, the rotation means 10 fixes the pinion 16 to the base end of the
inner mold 5 and controls the rotation by winding the timing belt 17 around the pinion 16 and a
pinion of a drive motor (not shown). Although structured, other rotating means such as sprocket
and chain drives, gear drives, etc. may be used. Further, in the present embodiment, the inner
mold 5 serving as the core is rotated, but it is also possible to rotate the outer mold 7. It is also
possible in principle to rotate both the inner mold 5 and the outer mold 7 with a rotational
difference.
[0027]
Thus, when the inner mold 5 is rotated in the R direction of FIG. 1 during molding of the conical
molded product 3, the molten resin filled from the injection portion 4 is the inner molding
surface of the inner mold 5. The flow direction is twisted as shown in FIG. In general, in the resin,
the molecular orientation direction P of the molecular chains tends to be oriented in the flow
direction. FIG. 4 shows an example in which the molecular orientation direction P of the conical
portion 12 of the conical molded article 3 has components in the generatrix direction and the
circumferential direction. When the rotation angle, the rotation speed or the rotation torque is
made larger when the inner mold 5 is rotated, the component in the circumferential direction of
the molecular orientation direction P is increased.
[0028]
Then, a thermoplastic aromatic polyester liquid crystal polymer is used as the resin. The liquid
crystal polymer can be made highly rigid due to the dense crystal structure, and can be made
thinner and lighter due to the high fluidity unique to liquid crystals. And, the liquid crystal
polymer has a property that molecular entanglement is small at the time of melting, and it has a
property of molecular orientation in one direction only by receiving a slight shear force, and
exhibits liquid crystal properties while being liquid. Then, when cooled and solidified, the state is
stably maintained. That is, at the time of molding, the molecular chains are molecularly oriented
in the flow direction, and a reinforcement effect is produced as if it were reinforcing itself by
itself, and extremely high strength and elastic modulus (Young's modulus) can be obtained. It is
also known that, despite the high modulus of elasticity, it exhibits very good vibration absorption
properties.
[0029]
And, by the rotational molding technology, the molecular alignment direction of the liquid crystal
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polymer has a circumferential component, and the crystal alignment can be strengthened, and
further, the molecular alignment can be further reinforced and thinned by high-speed injection
molding.
[0030]
The liquid crystal polymer used in the present embodiment is Civeras L304 M35 (trade name of
Toray Industries, Inc.).
Molding conditions are a resin temperature of 350 ° C., a mold temperature of 150 ° C., an
injection time of 0.3 seconds, and a cooling time of 5 seconds. The dimensions of the conically
shaped part (conical part 12) are 120 mm in outer diameter and 0.3 mm in thickness, and the
twist angle α of molecular orientation is 15 °. Here, in FIG. 4, the twist angle α is an angle
formed by the generatrix direction B and the tangential direction of the molecular orientation.
[0031]
When there was no twist angle α (normal injection molding), molding was possible, but the
strength was weak in the direction perpendicular to the molecular orientation (flowing direction)
and in the direction perpendicular to the circumference (circumferential direction), and cracking
occurred easily. On the other hand, the molded article provided with the twist angle α did not
break. Here, a sample (width 5 mm, length 50 mm) was cut out from the molded article and
subjected to a tensile test. As a result, the elastic modulus was increased by about 1.7 times, to
13 MPa for the twist angle α of 0, and to 22 MPa for the twist angle α of 15 °.
[0032]
Then, as shown in FIG. 5, using the conical molded product 3 molded by the above-described
manufacturing method, the conical molded product 3 was processed into a cone shape, and a
speaker diaphragm 18 was manufactured. Specifically, as shown in FIG. 5, the closed portion 13
and the flange portion 14 of the conical shaped product 3 are cut out to manufacture a speaker
diaphragm having a cone shape. Then, although not shown, an edge member is adhered to the
outer periphery of the speaker diaphragm 18, a voice coil and a center cap are adhered to the
central portion, and they are attached to a frame together with a magnet to manufacture a
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dynamic speaker. .
[0033]
As described above, the speaker vibration made of the conventional liquid crystal polymer is
caused by providing components in both the generatrix direction and the circumferential
direction in the molecular alignment direction P of the conical portion 12 by rotational molding
technology using the liquid crystal polymer. It is possible to achieve high E / ρ which is not in
the plate, and to achieve cost reduction by high productivity (injection molding). When the
specific elastic modulus is high, the speed of sound traveling through the inside of the diaphragm
is high, and the speaker has excellent acoustic characteristics. Furthermore, freedom of design in
E / 賦 and the size of internal loss can be achieved by adding a filler to control molding
conditions, shape complex shapes by hot pressing, or improve internal loss. The degree is
increased, which makes it possible to provide an optimum diaphragm for each use range.
[0034]
Besides liquid crystalline polymers based on thermoplastic aromatic polyester, polypropylene
(PP), polyethylene (PE), polystyrene, polyethylene terephthalate (PET), polymethyl methacrylate,
polymethylpentene (TPX), polyetherimide (PEI) It is also possible to use
[0035]
Furthermore, the above-mentioned synthetic resin can be appropriately filled with a filler for
improving acoustic characteristics.
[0036]
DESCRIPTION OF SYMBOLS 1 forming die 2 cavity 3 conical molded product 4 injection part 5
inner mold 6 mold body 7 outer mold 8 bearing 9 movement control part 10 rotation means 11
ejector pin 12 conical part 13 closed part 14 flange part 15 sprue 16 pinion 17 Timing Belt 18
Speaker Diaphragm R Rotational Direction P Molecular Orientation Direction B Bust Direction
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