JP3343622B2 - Method of manufacturing plastic cover boots - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a cover boot for covering a constant velocity joint of an automobile by blow molding a thermoplastic elastomer.

[0002]

2. Description of the Related Art Generally, in the process of forming a small-diameter mouth portion integrally with a body portion by blow molding, means for driving an inner diameter regulating body into the mouth portion to regulate the inner diameter is disclosed in Japanese Patent Laid-Open No. 63-7 / 1988.
No. 2521. Also, in the step of molding a cover boot for a constant velocity joint of an automobile by blow molding of a thermoplastic elastomer, an inside diameter regulating body for regulating the inside diameter of the small diameter fixing portion is inserted into a parison arranged between the divided molds, Means for regulating the inner surface of the small diameter fixing portion is described in Japanese Patent Application Laid-Open No. 2-92615.

[0003]

In the above-mentioned conventional method of manufacturing a cover boot, the inside diameter regulating body for regulating the inside diameter of the small diameter fixing portion is inserted into the parison arranged in the split mold and blow-molded. While regulating the inner diameter of the small diameter fixing portion with high accuracy, the inner surface can be formed flat, but in the step of driving the inner diameter regulating body into the small diameter fixing portion,
The molten resin is moved inward by the inner diameter regulating body, and the resin is liable to accumulate in an inner portion of the small diameter fixing portion, and as a result, the sealing performance of the small diameter fixing portion with respect to the shaft portion of the constant velocity joint is impaired. Problem.

SUMMARY OF THE INVENTION An object of the present invention is to solve the conventional problems as described above, and when forming a cover boot by blow molding of a thermoplastic elastomer, a flexible cover portion of the cover boot and By molding the small-diameter fixed part using a separate fixed-part molding die from the blow-molding die that blow-molds the large-diameter fixed part, a small-diameter fixed part with high dimensional accuracy of the inner diameter and no resin accumulation is formed. ,
It has excellent sealing properties, and furthermore, the parison, which is extruded from the extrusion head and placed between the blow molding dies, hangs down along the mandrel, so that variations in wall thickness due to the weight of the palison placed between the blow molding dies can be reduced. It is an object of the present invention to provide a method of manufacturing a plastic cover boot which can easily and accurately control the thickness of a parison.

[0005]

In order to achieve the above object, the present invention has developed the following means. That is, the method of manufacturing a plastic cover boot according to the present invention is such that a small-diameter fixing portion is provided at one end, a large-diameter fixing portion is provided at the other end, and a flexible cover portion is provided in the middle of the blow-molded thermoplastic elastomer. In the manufacturing method of the formed cover boot, a fixing part forming die for forming a small diameter fixing part of the cover boot is arranged at a lower end of an extrusion head including a die and a mandrel forming a resin path, and protruding from the extrusion die. Between the mandrel and the fixed part forming mold, a cavity of the small diameter fixing part is formed, and first, the molten resin is extruded from the resin path of the extrusion head to fill the cavity of the small diameter fixing part with the molten resin, and then, While the molten resin continuously extruded from the resin path of the extrusion head follows the surface of the mandrel, the fixed part forming die is drooped between the blow molding die together with the mandrel. Te, the upper end face of the fixing portion molding die while moving to a position in contact with the blow mold the lower end face of the places the Parisun that along a surface of the mandrel between the blow molding mold,
Next, the blow molding die is closed, and a pressure fluid is introduced into the parison to blow-mold the flexible cover portion and the large-diameter fixing portion.

[0006]

According to the present invention, the molten resin extruded from the extrusion head is filled into the cavity of the small-diameter fixing portion formed by the fixed portion forming mold and the mandrel separate from the blow molding die, and the small-diameter is formed first. The fixing part is formed. Next, the parison arranged between the blow molding dies is extruded from the extrusion head and the parison arranged between the blow molding dies is hung down along with the surface of the mandrel together with the fixed part forming mold, and is blown by the blow molding mold. The flexible cover portion and the large diameter fixing portion are blow molded, and a cover boot in which the small diameter fixing portion, the flexible cover portion, and the large diameter fixing portion are integrated is formed.
Since the small diameter fixing portion of the cover boot thus formed is formed by the cavity of the small diameter fixing portion formed by the mandrel and the fixing portion forming die as described above, the dimensional accuracy of the inner diameter is high, In addition, a small-diameter fixing portion having no resin pool is formed. Further, since the parison extruded from the extrusion head and disposed between the blow molding dies hangs down along the surface of the mandrel, the thickness of the parison disposed between the blow molding dies does not fluctuate due to its own weight. In addition, the thickness of the parison can be easily and accurately controlled by adjusting the extrusion speed or the extrusion pressure of the molten resin extruded from the extrusion head.

[0007]

1 to 3 show steps of manufacturing a plastic cover boot according to the present invention. In the drawings, reference numeral 1 denotes an extrusion head, and the extrusion head 1
A die 3 and a core 4 that form the resin path 2, and a mandrel 5 that projects downward from the center of the core 4 and that can move up and down. Reference numeral 6 denotes a blow mold of a split type. The blow mold 6 has a cavity 7 for forming a cover boot large diameter fixing portion and a cavity 8 for forming a bellows-like flexible cover. . Reference numeral 9 denotes a fixed part forming die, and the fixed part forming die 9 forms a cavity 10 of a small diameter fixed part by its inner surface and the protruding part of the mandrel 5.

Next, the manufacturing process will be described. As shown in FIG. 1, the blow molding die 6 is in an opened state, the fixing portion forming die 9 is arranged so as to be in contact with the lower end surface of the extrusion head 1, and the cavity of the small diameter fixing portion is formed by the projecting portion of the mandrel 5. The molten resin 11 is extruded from the resin path 2 of the extrusion head 1 and filled in the cavity 10.

Next, as shown in FIG.
With the fixed part molding die 9 attached to the lower end of
While sequentially lowering the mandrel 5, the molten resin 11 is extruded from the extrusion head 1 and adheres to the surface of the mandrel 5, and the parison 12 adhered to the surface of the mandrel 5 is arranged between the blow molding dies 6, and the fixing portion is formed. The lowering of the mandrel 5 is stopped at a position where the upper end surface of the molding die 9 contacts the lower end surface of the blow molding die 6. As described above, the parison 12 arranged between the blow molding dies 6 adheres to the surface of the mandrel 5 and hangs down. Therefore, a drawdown in which the thickness of the parison 12 becomes thinner due to its own weight does not occur. By adjusting the extrusion speed or pressure of the molten resin extruded from the extrusion head 1 or by adjusting the distance between the core 4 and the mandrel 5 by moving the core 4 up and down, the wall thickness of the parison 12 in the hanging direction can be easily increased. It can be controlled accurately. In the example shown in FIG. 2, the portion corresponding to the cavity 8 for forming the large-diameter fixing portion where the blow ratio at the time of blow molding is large by the above means is made thicker than the other portions.

Next, as shown in FIG. 2, when the arrangement of the parison 12 between the blow molds 6 is completed, the blow mold 6 is closed and pressure is applied from the mandrel 5 into the paris 12, as shown in FIG. By introducing the fluid, the large diameter fixing portion 14 of the cover boot 13 by the cavities 7 and 8,
The bellows-like flexible cover 15 is blow molded. Further, since the small diameter fixing portion 16 has already been formed by the cavity 10 of the fixing portion forming die 9 and the upper end surface of the fixing portion forming die 9 is in contact with the lower end surface of the blow molding die 6, The small diameter fixing portion 16 is formed integrally with the movable cover portion 15 in a continuous manner.

Although not shown, after the blow molding die 6 and the fixed portion molding die 9 are cooled, the blow molding die 6 is cooled.
Is opened, and the mandrel 5 is pulled up to take out the formed cover boot 13. Since the end surface of the large-diameter fixing portion 14 of the cover boot 13 is closed as shown in FIG. 3, the large-diameter fixing portion 14 is opened by cutting off that portion.

As the thermoplastic elastomer forming the cover boot 13, a polyester elastomer, a polyamide elastomer, a polyurethane elastomer, a polyolefin elastomer or the like can be used. (Polyester-based elastomer) Multi-block copolymer having a soft segment mainly composed of aliphatic polyether or aliphatic polyester and a hard segment composed of high-melting crystalline aromatic polyester. . In principle, various types of polyester elastomers can be obtained by changing the types and proportions of dibasic acids, glycols and polyesters or polyethers. Polyester elastomers currently on the market include “Hytrel” by Dupont Toray, “Pelprene” by Toyobo, “Lomod” by General Electric (USA), and “Romod” by Akzo (Ranchi). "Anytel" and so on. (Polyamide-based elastomer) Block copolymers of polyamide and polyether or polyester, or plasticizers such as N-ethyl O, P toluenesulfamide, benzenesulfonbutyramide, and the like with nylon 11 or nylon 12, Phenols such as nonylphenol, carboxylic acid esters such as ethylenehexyl-2-oxyethylphthalate and the like.
About 30% by weight was mixed. Currently, polyamide-based elastomers on the market include "Daiamide PAE" by Daicel Chemical Industries, Ltd. and "Greak A" by Dainippon Ink and Chemicals, Inc. (Polyurethane-based elastomer) Polyether or polyester diol and glycol or the like are polyadded with diisocyanate. In this case, triol, diamine or triamine are also used in combination. It is called ether-based polyurethane or the like. In addition, as a diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, etc., and as glycol, ethylene glycol,
1,4-butylene glycol, 1,4-hexanediol, bishydroxybenzene, and the like. Polyester diols include polyethylene adipate, poly 1,4
-Butylene adipate, poly 1,6-hexane adipate, polycaprolactone, polycarbonate, etc.,
Examples of the polyether diol include polyoxytetramethylene glycol. Currently, polyurethane-based elastomers on the market include "Milactran" of Nippon Milactran Co., Ltd. and "Elastolane" of Takeda Pharmaceutical Co., Ltd. (Polyolefin elastomer) An olefin rubber such as ethylene-propylene rubber is used as a soft segment,
It is a multi-block copolymer having an olefin resin such as polyethylene or polypropylene as a hard segment. Currently, polyolefin-based elastomers on the market include Mitsubishi Yuka's Thermorun,
"Sumitomo TPE" of Sumitomo Chemical Co., Ltd., "Millastomer" of Mitsui Petrochemical Industry Co., Ltd., and "Santoprene" of Monsanto Japan Limited.

As described above, the molten resin 11 extruded from the extrusion head 1 includes the mandrel 5 and the blow mold 6.
The cavity 10 of the small diameter fixing part formed by the fixing part forming die 9 different from the above is filled and the small diameter fixing part 16 is formed first, so that the dimensional accuracy of the inner diameter is high, and the small diameter without resin accumulation is high. The fixing portion 16 is formed. For this reason, the cover boot 13 which is excellent in sealing property and has the small diameter fixing portion 16 with respect to the shaft portion of the constant velocity joint (not shown) is obtained. Also, a parison 12 arranged between the blow molding dies 6 is provided.
Adheres to the surface of the mandrel 5 and hangs down together with the fixed part forming die 9, so that the draw-down due to the weight of the parison 12 arranged between the blow molding dies 6 does not occur. The molten resin 11 extruded from the extrusion head 1
The thickness of the parison 12 can be easily and accurately controlled by adjusting the extrusion speed or the extrusion pressure of the core 4 or by moving the core 4 up and down. The cover boots 13 having a uniform thickness can be formed.

In the above-described embodiment, the mandrel 5 to which the parison 12 is attached has a cylindrical shape that is straight up and down. However, the outer shape of the mandrel 5 has a shape corresponding to the shape of the cover boot 13, for example, the shape of the cover boot 13. If the outer shape of the mandrel 5 corresponding to the bellows-shaped portion of the flexible covering portion 15 is a wave shape, for example, a shape corresponding to the desired thickness of the cover boot 13, accurate control of the thickness is possible. Become. Furthermore, in the above embodiment, the parison 12 was attached to the mandrel 5 and was hung. However, a slight pressure fluid was introduced between the mandrel and the parison 12 in advance, and the parison 12 was formed under positive pressure. It is also possible to hang the parison 12 along the mandrel 5 without attaching it to the mandrel 5. This is preferable because the adverse effect due to the adhesion of the parison 12 can be eliminated when blow molding by introducing a pressure fluid.

[0015]

According to the present invention, in forming a cover boot by blow molding of a thermoplastic elastomer,
By molding the small diameter fixing part using a fixing part molding die different from the blow molding die for blow molding the flexible cover part and the large diameter fixing part of the cover boot, the dimensional accuracy of the inner diameter is high, and the resin pool By forming a small-diameter fixing portion having no seal, a plastic cover boot having excellent sealing properties can be obtained. According to the present invention, the thickness of the parison disposed between the blow molding dies is changed by the weight of the parison disposed between the blow molding dies by attaching and drooping the parison disposed between the blow molding dies and extruded from the extrusion head. In addition, the thickness of the parison can be accurately controlled, and a plastic cover boot having a uniform wall thickness can be obtained in accordance with the blow ratio.

[Brief description of the drawings]

FIG. 1 is a sectional view of a mold for blow molding a plastic cover boot according to the present invention.

FIG. 2 is a sectional view of a mold showing a mode in which a parison is arranged between blow molds.

FIG. 3 is a cross-sectional view of a mold showing a mode in which a pressurized fluid is introduced into a parison and blow-molded.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extrusion head 2 Resin path 3 Die 4 Core 5 Mandrel 6 Blow molding die 7 Cavity for molding large diameter fixing portion 8 Cavity for molding flexible covering portion 9 Fixed portion forming die 10 Cavity for small diameter fixing portion 11 Melting Resin 12 Paris 13 Cover boot 14 Large diameter fixing part 15 Flexible covering part 16 Small diameter fixing part

Claims (1)

(57) [Claims] 1. A method of manufacturing a cover boot, comprising a small-diameter fixed portion at one end, a large-diameter fixed portion at the other end, and a flexible cover portion formed in the middle by blow molding a thermoplastic elastomer. At the lower end of the extrusion head consisting of a die and a mandrel forming a resin path, a fixed part forming mold for forming a small diameter fixed part of the cover boot is arranged, and a mandrel projecting from the extrusion die and a fixed part forming mold are arranged. In the meantime, the cavity of the small diameter fixing portion is formed. First, the molten resin is extruded from the resin path of the extrusion head to fill the cavity of the small diameter fixing portion with the molten resin, and then extruded from the resin path of the extrusion head. While the molten resin is along the surface of the mandrel, the fixed part forming mold is drooped between the blow molding dies together with the mandrel, and the upper end face of the fixed part forming mold is blow molded. Move to a position in contact with the lower end surface of the mold, and arrange a parison along the surface of the mandrel between the blow molding dies, then close the blow molding dies, introduce a pressure fluid into the parison, and A method for manufacturing a plastic cover boot, comprising blow molding a conductive cover portion and a large diameter fixing portion.