JP2014097645A - Method for producing conical molded part and diaphragm for speaker thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a conical molded part capable of mass-producing a conical molded part having high mechanical strength though it is thin and lightweight by controlling the orientation direction of a resin by a rotary molding technique using a synthetic resin, and to provide a diaphragm for a speaker having excellent acoustic properties particularly by increasing its specific modulus E/ρ and increasing its internal loss.SOLUTION: Using a molding die 1 provided with a cavity molding a conical molded part 3 with a rotational symmetry form having a thin cone or truncated cone, and further an injection part 4 for a molten resin at the tip part corresponding to the tip part of the conical molded part, the molten resin is fitted into the cavity, and simultaneously, or, in a step of the filling, and further, directly after the completion of the filling, at least either the inside part or the outside part of the molding die in the conical molded part is rotated to a circumferential direction, and both components in the bus direction and the circumferential direction of the resin are given to the molecular orientation of the resin. It is most suitable that a diaphragm for a speaker is molded with a liquid crystal polymer.

Description

  The present invention relates to a method of manufacturing a conical molded product made of a synthetic resin and controlled in orientation, and a speaker diaphragm using the method.

  The diaphragm of a dynamic speaker is required to have less natural vibration due to divided vibration or resonance and to have good conversion efficiency. For this reason, the diaphragm has a material having a specific elastic modulus E / ρ (E: Young's modulus, ρ: density) as large as possible, and a moderately large internal loss in order to smooth the frequency characteristics in the high sound range, that is, it is hard. Light material is used. It is also important that there is little deterioration over time. It is not easy to find a material that satisfies all of these requirements at a high level.

  Conventionally, cone paper has been mainly used as a speaker diaphragm. For the purpose of increasing 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. Used for low to medium sound units. Further, a metal diaphragm is also used, and in particular, a beryllium diaphragm has excellent characteristics. In general, metals have a higher specific gravity than paper and have a high specific modulus, but they are mainly used for high sound units due to their low internal loss.

  Patent Document 1 discloses a speaker diaphragm that uses a thermoplastic aromatic polyester-based liquid crystal polymer as a material and has an orientation of the liquid crystal polymer inside. As a method for manufacturing a speaker diaphragm, a material containing a thermoplastic aromatic polyester-based liquid crystal polymer is heated and melted at a temperature equal to or higher than a temperature at which the liquid crystal polymer becomes liquid crystal, and a predetermined pressure is applied to the heat-melted material. Is added to a mold that is maintained at a predetermined temperature in a region where the liquid crystal polymer is solidified, and a multilayer alignment layer of the liquid crystal polymer is molded inside. Here, an injection part is provided at the center, and the molding part is molded by injection molding using a mold having a truncated cone shape.

  The liquid crystal polymer has the property of molecular orientation with a slight shear force, and its orientation is high, so it is strong in the molecular orientation direction, but weak in the direction perpendicular to the molecular orientation direction, and thin and easy to break. There is a drawback of becoming. Therefore, in Patent Document 2, when a diaphragm for a speaker is formed using a liquid crystal polymer, a meandering groove is partially formed on the mold surface so that the liquid crystal polymer flows in the mold surface. It is disclosed that the strength is improved by meandering and the alignment of the liquid crystal polymer meanders.

  In Patent Documents 3 and 4, the molten resin is rotated in the circumferential direction by a rotating means equipped with a rotation control device at the same time as injection or filling of the molten resin into the mold, or immediately after the filling. A method for manufacturing a cylindrical injection-molded product having means for controlling an angle, a rotational speed, a rotational torque, and a rotation start time of at least one of an inner part and an outer part of a mold is disclosed. The cylindrical molded product obtained thereby has a high mechanical strength because the resin is oriented in the circumferential direction, and there is no variation in strength due to the site of the molded product.

Japanese Examined Patent Publication No. 4-39279 JP-A-4-77095 Japanese Patent No. 2537131 Japanese Patent No. 3185093

  In view of the above-mentioned situation, the present invention intends to solve the problem of controlling a molecular orientation direction of a resin by a rotational molding technique using a synthetic resin, so that a cone having high mechanical strength despite being thin and lightweight. A method for producing a cone-shaped molded product capable of mass-producing a molded molded product at low cost, and in particular, a speaker diaphragm having excellent acoustic characteristics by increasing internal loss and increasing specific elastic modulus E / ρ The point is to provide.

  In order to solve the above-mentioned problems, the present invention is a method of manufacturing a rotationally symmetric cone-shaped product having a thin cone or a truncated cone, comprising a cavity for molding the cone-shaped product, and the cone. In a cone-shaped molded article, a mold having a molten resin injection part at the top corresponding to the top of the shaped molded article is used at the same time as or after the filling of the molten resin into the cavity, and immediately after the filling is completed. Production of a conical molded product characterized in that at least one of the inner part and the outer part of the molding die is rotated in the circumferential direction so that the molecular orientation of the resin has both the generatrix and circumferential components. A method was constructed (claim 1).

  Here, it is preferable to fill the cavity with the molten resin from the injection portion of the mold by injection molding.

  More preferably, the resin is a thermoplastic aromatic polyester-based liquid crystal polymer.

  Specifically, the conical molded product is directed radially outward at a conical portion, a closing portion that closes a top portion of the conical portion and intersects a rotation center of the mold, and a bottom portion of the conical portion. It is preferable to have a flange portion (claim 4).

  Then, using the conical molded product molded by the above-mentioned method for manufacturing a conical molded product, a part of the conical molded product was cut out to produce a cone-shaped speaker diaphragm.

  Here, a conical molded product having a truncated cone surface orthogonal to the rotation center of the mold at the top and a flange portion facing radially outward at the bottom is used, and the closed portion of the conical molded product is used. The speaker diaphragm was cut into a cone shape by cutting the flange portion.

  According to the method for producing a cone-shaped article of the present invention as described above, a method for producing a rotationally symmetric cone-shaped article having a thin cone or a truncated cone, the cavity for molding the cone-shaped article. And a mold having a molten resin injection portion at the top corresponding to the top of the conical shaped product, and filling the cavity with the molten resin, or at the time of filling, 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 shaped product is rotated in the circumferential direction, the molecular orientation of the resin has both the generatrix and circumferential components. The molecular orientation of the resin in the cone-shaped part of the product is twisted, so that it has sufficient mechanical strength even when molded into a thin wall, there is no unevenness of characteristics due to the part of the molded product, and it has excellent shape stability . Here, “twist of molecular orientation” means that the molecular orientation has an angle with respect to the generatrix direction of the conical shaped product.

  In addition, when a thermoplastic aromatic polyester-based liquid crystal polymer is used, it is excellent in fluidity during molding, so that a thin molded product can be easily molded and oriented in a single direction with a slight shear force. In addition, since the resin molecular orientation has components in the generatrix direction and the circumferential direction, a molded product having high mechanical strength and high elastic modulus can be obtained even if it is thin.

  Then, using the cone-shaped molded product molded by the above-described method for producing a cone-shaped molded product, a portion of the cone-shaped molded product is cut into a cone shape to produce a thin and strong speaker diaphragm. be able to. In particular, when manufactured using a liquid crystal polymer, even if it is thin and lightweight, E / ρ is high and internal loss is large, so that a speaker diaphragm having excellent acoustic characteristics can be manufactured.

  Here, a conical molded article having a conical portion, a closing portion that closes the top of the conical portion and intersects with the rotation center of the mold, and a flange portion that faces radially outward at the bottom of the conical portion. When a speaker diaphragm having a cone shape is manufactured by cutting off the closed portion and the flange portion of the cone-shaped product, only the conical portion with stable mechanical properties of the cone-shaped product can be used. Furthermore, a speaker diaphragm having excellent acoustic characteristics can be manufactured.

It is a simplified sectional view of a forming die used for a manufacturing method of a cone-shaped molded article of the present invention. It is a perspective view of the cone-shaped molded product taken out from the shaping | molding die. Similarly it is sectional drawing of a conical molded product. It is an explanatory perspective view which shows the orientation direction of resin of the cone-shaped molded article shape | molded by this invention. It is a perspective view of the diaphragm for speakers.

  Hereinafter, details of the present invention will be described based on embodiments. FIG. 1 shows a mold using a rotational molding technique employed in the method for manufacturing a cone-shaped article of the present invention, and FIGS. 2 and 3 show a cone-shaped article molded by the mold. A mold, 2 is a cavity, and 3 is a conical molded product.

  The present invention relates to a method of manufacturing a rotationally symmetric cone-shaped article having a thin cone or truncated cone, comprising a cavity for molding the cone-shaped article, and corresponding to the top of the cone-shaped article. Using a mold having a molten resin injection part at the top and filling the cavity with the molten resin, or at the stage of filling, and immediately after the filling, the inner part and the outer part of the mold in the conical molded product At least one of them is rotated in the circumferential direction, and the molecular orientation of the resin has both the generatrix and circumferential components.

  Here, the conical molded product 3 is molded by injection molding in which the cavity 2 is filled with molten resin from the injection portion 4 of the molding die 1 by injection molding.

  Specifically, as shown in FIG. 1, the mold 1 includes a rotationally symmetric inner mold 5, a mold body 6 that rotatably holds the inner mold 5, and the inner mold 5. And an outer mold 7 that forms the cavity 2 with the end face of the mold body 6. The inner mold 5 is inserted into the mold main body 6 so as to be rotatable at a fixed position by a radial bearing 8 and an axial movement restricting portion 9, and the inner surface of the conical molded product 3 is inserted. An inner molding surface of the distal end portion to be formed protrudes from the end surface of the mold body 6, and a rotating means 10 is provided at the proximal end portion. The outer mold 7 includes 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 constitute the cavity 2. Further, the conical molded product 3 can be taken out from the end face of the mold body 6. The injection part 4 is formed so as to penetrate from the outer surface of the outer mold 7 to the outer molding surface. An ejector pin 11 for extruding the conical molded product 3 from the end surface of the mold body 6 is provided so as to be able to appear and retract.

  In the present embodiment, as shown in FIGS. 2 and 3, the conical molded product 3 includes a conical portion 12 and a closing portion that closes the top of the conical portion 12 and intersects the rotation center of the inner mold 5. 13 and a shape having a flange portion 14 facing outward in the radial direction at the bottom of the conical portion 12. Here, the closing portion 13 is a truncated cone surface orthogonal to the rotation center of the inner mold 5. Further, the sprue 15 protruding to the center of the closing 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 spreads radially to the closing portion 13, then spreads the conical portion 12 in the same radial direction and flows to the bottom, and finally fills the flange portion 14. In order to uniformly fill the molten resin into the cavity 2, it is preferable to arrange the rotation center of the conical shaped product 3 in the vertical direction, but it may be arranged in the horizontal direction.

  At the same time as the molten resin is injected and filled into the cavity 2 of the mold 1, or at the time of filling, and immediately after the completion of filling, the inner mold 5 is rotated in the circumferential direction by the rotating means 10, A circumferential component is provided in the molecular orientation direction of the resin. Here, when the inner mold 5 is rotated, the size (vector) of the circumferential component of the molecular orientation direction is controlled by controlling the rotation angle, rotation speed, rotation torque, and rotation start time. To do. The mold 1 is also provided with the aforementioned molecular orientation control means. This rotational molding technique itself is known.

  In the present embodiment, the rotating means 10 fixes the pinion 16 to the proximal end portion 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 it has a structure, it is also possible to use other rotating means such as a sprocket and a chain drive or a gear drive. Moreover, in this embodiment, although the said inner side metal mold | die 5 used as a core was rotated, the said outer side metal mold | die 7 can also be rotated. It is also possible in principle to rotate both the inner mold 5 and the outer mold 7 with a rotational difference.

  As described above, when the inner mold 5 is rotated in the R direction in FIG. 1 when the conical molded product 3 is molded, the molten resin filled from the injection portion 4 becomes the inner molding surface of the inner mold 5. As shown in FIG. 4, the flow direction is twisted. In general, the resin tends to have the molecular orientation direction P of the molecular chain in the flow direction. FIG. 4 shows an example in which the molecular orientation direction P of the conical portion 12 of the conical shaped product 3 has components in the generatrix direction and the circumferential direction. When the inner mold 5 is rotated, if the rotation angle, the rotation speed, or the rotation torque is increased, the circumferential component of the molecular orientation direction P increases.

  A thermoplastic aromatic polyester liquid crystal polymer is used as the resin. The liquid crystal polymer can be made highly rigid due to its dense crystal structure, and can be made thinner and lighter due to the high fluidity unique to liquid crystals. The liquid crystal polymer has little entanglement of molecules at the time of melting, has a property of molecular orientation in one direction only by receiving a slight shear force, and exhibits a crystal property while being liquid. And when cooled and solidified, the state is kept stable. In other words, the molecular chains are molecularly oriented in the flow direction at the time of molding, producing a reinforcing effect as if they were reinforcing themselves, and extremely high strength and elastic modulus (Young's modulus) can be obtained. It is also known that it exhibits very good vibration absorption characteristics despite its high elastic modulus.

  Then, by the rotational molding technique, the molecular orientation direction of the liquid crystal polymer has a circumferential component, so that the crystal orientation can be strengthened, and further, the molecular orientation can be further strengthened and thinned by high speed injection molding.

  The liquid crystal polymer used in this embodiment is Siberus L304 M35 (trade name of Toray Industries, Inc.). The 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 conical shaped product (cone portion 12) are an outer diameter of 120 mm and a thickness of 0.3 mm, and the twist angle α of the molecular orientation is 15 °. Here, the twist angle α is an angle formed by the generatrix direction B and the tangential direction of the molecular orientation in FIG.

  When there was no twist angle α (normal injection molding), molding was possible, but the strength in the molecular orientation direction (flow direction) and the vertical direction (circumferential direction) was weak, and it was easily cracked. On the other hand, the molded product provided with the twist angle α was not broken. Here, a sample (width 5 mm, length 50 mm) was cut out from the molded product, and a tensile test was performed. As a result, the elastic modulus was 13 MPa when the twist angle α was 0, whereas it was 22 MPa when the twist angle α was 15 °, and increased by about 1.7 times.

  Then, as shown in FIG. 5, a speaker diaphragm 18 formed by processing the cone-shaped product 3 into a cone shape by using the cone-shaped product 3 molded by the above-described manufacturing method was manufactured. Specifically, as shown in FIG. 5, a speaker diaphragm having a cone shape is produced by cutting off the closing portion 13 and the flange portion 14 of the conical molded product 3. Although not shown, an edge member is bonded to the outer periphery of the speaker diaphragm 18, a voice coil and a center cap are bonded to the center, and these are attached to a frame together with a magnet to manufacture a dynamic speaker. .

  As described above, the rotational vibration technique using the liquid crystal polymer causes the molecular orientation direction P of the conical portion 12 to be twisted by having both the generatrix direction and the circumferential direction component. High E / ρ that is not found on the plate can be achieved, and cost reduction can be achieved by high productivity (injection molding). When the specific elastic modulus increases, the speed of sound transmitted through the inside of the diaphragm increases, resulting in a speaker with excellent acoustic characteristics. Furthermore, by controlling the molding conditions and forming a complicated shape by hot pressing into the molded product, or adding a filler to improve the internal loss, the design freedom in E / ρ and the size of the internal loss is free. As a result, it becomes possible to provide an optimum diaphragm for each operating sound range.

  In addition to thermoplastic aromatic polyester-based liquid crystal polymers, polypropylene (PP), polyethylene (PE), polystyrene, polyethylene terephthalate (PET), polymethyl methacrylate, polymethylpentene (TPX), polyetherimide (PEI) Etc. can also be used.

  Furthermore, the above-mentioned synthetic resin can be appropriately filled with a filler for improving acoustic characteristics.

DESCRIPTION OF SYMBOLS 1 Mold 2 Cavity 3 Cone-shaped molded article 4 Injection | pouring part 5 Inner metal mold | die 6 Mold main body 7 Outer metal mold | die 8 Bearing 9 Movement control part 10 Rotating means 11 Ejector pin 12 Conical part 13 Closure part 14 Flange part 15 Sprue 16 Pinion 17 Timing belt 18 Speaker diaphragm R Rotational direction P Molecular orientation direction B Bus direction

Claims (6)

  A method of manufacturing a rotationally symmetric cone-shaped molded article having a thin-walled cone or truncated cone, comprising a cavity for molding the cone-shaped molded article, and a molten resin at the top corresponding to the top of the cone-shaped molded article At the same time as or after the filling of the molten resin into the cavity, and immediately after the filling, at least one of the inner part and the outer part of the mold in the conical shaped product is used. A method for producing a conical molded product, characterized in that it is rotated in the circumferential direction so that the molecular orientation of the resin has both the generatrix and circumferential components.   The method for manufacturing a conical molded product according to claim 1, wherein the cavity is filled with molten resin from an injection portion of the mold by injection molding.   The method for producing a conical molded product according to claim 1, wherein the resin is a thermoplastic aromatic polyester-based liquid crystal polymer.   The conical molded product has a conical portion, a closing portion that closes the top of the conical portion and intersects with the rotation center of the mold, and a flange portion that faces radially outward at the bottom of the conical portion. The method for producing a conical molded product according to any one of claims 1 to 3.   5. A loudspeaker diaphragm using a conical molded product formed by the method for producing a conical molded product according to claim 1, wherein a portion of the conical molded product is cut out to form a cone shape.   A loudspeaker diaphragm for a speaker, wherein a conical molded product molded by the method for producing a conical molded product according to claim 4 is used, and a closed portion and a flange portion of the conical molded product are cut out to form a cone shape.

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