JP3331434B2 - How to make 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 boots such as automobile constant velocity joints by blow molding a thermoplastic elastomer.

[0002]

2. Description of the Related Art A boot for a constant velocity joint of an automobile is made of a thermoplastic elastomer, and has a large-diameter fixing portion and a small-diameter fixing portion which are tightly sealed to the outer ring and the shaft of the joint at both ends of a bellows portion. For example, those described in JP-A-2-221766 are known.

[0003] Further, an injection mold cavity for forming a small-diameter fixed portion is formed by a small-diameter fixed portion mold and a core mold, and molten resin is injected from a molten resin path formed by a die and a mandrel. Inject into the cavity, move the small diameter fixing part mold and core mold upward between the opened blow molds to form a parison and arrange them between the blow molds, and close the blow mold to close the paris A method is also known in which a pressurized fluid is introduced into the inside and a boot having a large-diameter fixed portion and a small-diameter fixed portion at both ends of a bellows portion is manufactured by blow molding.

[0004]

A boot such as a constant velocity joint formed by blow molding of a thermoplastic elastomer has a large-diameter fixed portion and a small-diameter fixed portion attached to the outer ring of a joint such as a constant velocity joint and its shaft in order to seal the inside. Each part is tightly fitted and fixed with a tightening band, but in order to maintain high sealing performance, the inner surface of the large-diameter fixed part and the small-diameter fixed part where the mold is fitted has a smooth surface with no irregularities. It is important that it is finished.

By the way, an injection mold cavity for forming the small diameter fixing portion is formed by the small diameter fixing portion mold and the core mold, and the molten resin is injected from the molten resin path formed by the die and the mandrel. Inject into the cavity, move the small diameter fixing part mold and core mold upward between the opened blow molds to form a parison and arrange them between the blow molds, and close the blow mold to close the paris In a method of manufacturing a boot having a large-diameter fixed portion and a small-diameter fixed portion at both ends of a bellows portion by blow molding by introducing a pressure fluid into the inside, a die a and a mandrel b are formed as shown in FIGS. 9 and 10. After the molten resin d is injected into the injection mold cavity e from the molten resin path c formed by the above, when the small-diameter fixing portion mold and the core mold are moved upward, the pressure increased by the injection of the molten resin. Paris Since a bulged portion g is formed at the boundary between f and f, the bulged portion g is formed in the small-diameter fixing portion formed by the blow molding process using the blow molds h, h, and the sealing performance of the small-diameter fixing portion is impaired. There is.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, and a method for manufacturing a boot having blow-molded portions having a large-diameter fixed portion and a small-diameter fixed portion at both ends of a bellows portion, It is an object of the present invention to provide a method of manufacturing a boot capable of obtaining a boot having a high sealing property with respect to a shaft of a joint such as a constant velocity joint by finishing an inner peripheral surface of a small diameter fixing portion to a completely smooth surface.

[0007]

In order to achieve the above object, the present invention has devised the following means. In other words, the method for manufacturing a boot according to the present invention comprises forming an injection mold cavity for forming a small-diameter fixed portion with a small-diameter fixed portion mold and a core mold, and forming a molten resin path formed by a die and a mandrel. More molten resin is injected into the injection mold cavity, and then the parison is formed by moving the small-diameter fixing portion mold and the core mold upward between the opened blow molds, and is disposed between the blow molds. At the same time, the blow mold is closed, a pressure fluid is introduced into the parison, and a boot having a large-diameter fixed portion and a small-diameter fixed portion at both ends of the bellows portion is manufactured by blow molding. A small diameter fixing portion having a concave portion for mounting the fastener is formed, and a boundary between the small diameter fixing portion mold and the blow mold is formed at a base end rising portion from the small diameter fixing portion to the bellows portion, The outer diameter of the recess , The outer diameter of the base end rising portion as A, 1.03 ≦ A
/B≦1.40.

[0008]

According to the method of manufacturing a boot according to the present invention, a small-diameter fixing portion having a concave portion for mounting a fastener is formed in the outer periphery of the injection mold cavity, and a base end from the small-diameter fixing portion to the bellows portion. 1.03 ≦ A / B, where B is the outer diameter of the concave portion and A is the outer diameter of the base-side rising portion. ≤
Because of the relationship of 1.40, even if the bulge is formed in the parison when the small-diameter fixing portion mold and the core mold move upward, the small-diameter fixing portion has the inner peripheral surface of the injection mold cavity. It is properly regulated and formed into a smooth surface, and a recess for mounting the fastener is formed. In the blow molding process using the blow mold, since the boundary between the small-diameter fixing portion mold and the blow mold is formed at the base end side rising portion from the small-diameter fixing portion to the bellows portion, the small-diameter fixing portion and the bellows are formed. A continuous portion with the portion is finished into a smooth curved surface, and the strength and durability against deformation of the portion are improved.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment in which a boot for a constant velocity joint of an automobile is blow molded. 1 and 2, reference numeral 1 denotes a small-diameter fixed portion mold, and 2 denotes a core mold, which forms an injection mold cavity 3 for forming the small-diameter fixed portion. Reference numeral 4 denotes a die and reference numeral 5 denotes a mandrel, which forms a molten resin path 6. Reference numerals 7, 7 denote blow molds, 8 and 8 denote bellows cavities, 9, 9 denote large diameter fixing cavities, and 10 and 10 denote burr cavities.

An injection mold cavity 3 formed by the small-diameter fixed portion mold 1 and the core mold 2 for forming a small-diameter fixed portion is formed by:
The molten resin 11 is connected to the molten resin path 6 formed by the die 4 and the mandrel 5 and injected into the injection mold cavity 3. Next, the paris 12 is formed by moving the small-diameter fixing portion mold 1 and the core mold 2 upward between the opened blow molds 7 and 7 and is disposed between the blow molds 7 and 7. Next, the blow molds 7 and 7 are closed, a pressure fluid is introduced into the parison 12, and a boot having a large-diameter fixing portion and a small-diameter fixing portion at both ends of the bellows portion is blow-molded. In the step of moving the small-diameter fixing portion mold 1 and the core mold 2 upward, the mandrel 5 is moved up and down to adjust the opening degree of the molten resin path 6.
The thickness of the parison 12 can be controlled in its length direction. When closing the blow molds 7, 7, the mandrel 5 is raised to close the resin path 6. 13 is a blow hole.

In the injection mold cavity 3, as shown in detail in FIG. 4, a concave portion 15 for mounting a fastener is formed on the outer peripheral surface of the small diameter fixing portion 14 at the time of injection. Further, as shown in detail in FIG.
Even if a bulge 16 is formed in the parison 12 by forming the boundary between the small-diameter fixing portion mold 1 and the blow mold 7 at the base-side rising portion 17 leading to the bulge 16, details are shown in FIG. As described above, the small-diameter fixing portion 14 and the bellows portion 18 have a smooth curved surface and are continuously formed. Small diameter fixing part 14 and bellows part 1
In order for 8 to be continuously formed with a smooth curved surface,
Assuming that the outer diameter of the concave portion 15 is B and the outer diameter of the base standing portion 17 is A, the condition is that 1.03 ≦ A / B ≦ 1.40. By the way, when the ratio of A to B is too large, as shown in FIG. 5, a concave portion 19 is formed between the small diameter fixing portion 14 and the bellows portion 18, and A to B
Is too small, as shown in FIG.
0 occurs, and in any case, the strength and durability against deformation at the boundary between the small diameter fixing portion 14 and the bellows portion 18 are impaired.

FIGS. 7 and 8 show another embodiment of the present invention. In this embodiment, a concave portion 21 for fitting the core mold 2 is provided on the upper surface of the mandrel 5, and in the step of injecting the molten resin from the molten resin path 6 into the injection mold cavity 3, the molten resin path 6 is formed. The injection mold cavity 3 is reliably and stably communicated so that the injection of the molten resin from the molten resin path 6 to the injection mold cavity 3 is always performed accurately. In particular, since the core mold 2 can be formed as long as to be inserted into the concave portion 21 of the mandrel 5, as shown in FIG. It can be formed on a smooth surface. Other configurations are the same as those shown in FIGS. 1 and 2, and the same components are denoted by the same reference numerals and description thereof will be omitted.

According to the above-described manufacturing method, the small-diameter fixing portion 14 having the concave portion 15 on the outer periphery of which the fastener is mounted is formed in the injection mold cavity 3 and the base end side from the small-diameter fixing portion to the bellows portion. The outer diameter B of the concave portion 15 and the outer diameter A of the base-side rising portion 17 are formed such that the boundary between the small-diameter fixed die and the blow die is located at the rising portion. .4
Since the small diameter fixing portion 14 has a relationship of 0, the small diameter fixing portion 14 is formed into a smooth surface whose inner peripheral surface is properly regulated by the injection mold cavity 1, and the small diameter fixing portion 14 has excellent sealing properties.

As the thermoplastic elastomer constituting the boot 7, a polyester elastomer, a polyurethane elastomer, a polyolefin elastomer, a polyamide 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. (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. At present, polyurethane elastomers on the market include "Elastollan" of Nippon Elastollan 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. (Polyamide-based elastomer) A block copolymer of polyamide and polyether or polyester, or a plasticizer such as Nylon 11 or Nylon 12, sulfonic acid amides such as N-ethyl-O, P toluenesulfamide and benzenesulfonbutyramide And phenols such as noniphenol and carboxylic acid esters such as 2-ethylhexyl-2-oxyethylphthalate, etc., in an amount of about 5 to 30% by weight. Currently, polyamide-based elastomers on the market include "Daiamide PAE" by Daicel Chemical Industries, Ltd. and "Greak A" by Dainippon Ink and Chemicals, Inc.

[0015]

According to the present invention, in a method of manufacturing a boot having a large diameter fixing portion and a small diameter fixing portion at both ends of a bellows portion by blow molding, the inner peripheral surface of the small diameter fixing portion is completely smooth. As a result, a boot having a high sealing property with respect to a joint shaft such as a constant velocity joint can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a step of forming a boot according to the present invention.

FIG. 2 is a sectional view showing a step subsequent to FIG. 1;

FIG. 3 is an enlarged view of a circular portion indicated by a broken line in FIG. 2;

FIG. 4 is a cross-sectional view showing a partially formed aspect of a small diameter fixing portion and a bellows portion.

FIG. 5 is a cross-sectional view showing a partially formed aspect of a small diameter fixing portion and a bellows portion.

FIG. 6 is a cross-sectional view showing a partially formed aspect of the small diameter fixing portion and the bellows portion.

FIG. 7 is a cross-sectional view showing a step of forming a boot according to another embodiment of the present invention.

FIG. 8 is a sectional view showing a step subsequent to FIG. 7;

FIG. 9 is a cross-sectional view showing a step of forming a conventional boot.

FIG. 10 is a sectional view showing a step subsequent to that of FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Small-diameter fixed die 2 Core die 3 Injection die cavity 4 Die 5 Mandrel 6 Molten resin path 7,7 Blow die 8,8 Bellows cavity 9,9 Large-diameter fixed portion cavity 11 Molten resin 12 Paris 14 Small-diameter fixed Part 15 Concave part for mounting fasteners 16 Swelling part 17 Base-end rising part 18 Bellows part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ identification code FI B29L 31:26 B29L 31:26 (58) Field surveyed (Int.Cl. ⁷ , DB name) F16J 3/04 B29C 49/06 B29C 49/48 B29K 21:00 B29L 22:00 B29L 31:26

Claims (1)

(57) [Claims] 1. An injection mold cavity for forming a small diameter fixing portion is formed by a small diameter fixing portion mold and a core mold, and a molten resin is injected from a molten resin path formed by a die and a mandrel. Inject into the cavity, then move the small-diameter fixed part mold and core mold upward between the opened blow molds to form a parison and arrange them between the blow molds, and close the blow molds A pressurized fluid into a parision and blow molding a boot having a large-diameter fixed portion and a small-diameter fixed portion at both ends of a bellows portion. A small diameter fixing portion having a small diameter is formed, and a boundary between the small diameter fixing portion mold and the blow mold is formed at a base end rising portion from the small diameter fixing portion to the bellows portion. , The outer diameter of the above-mentioned proximal end As A, boots manufacturing method characterized by having a relation of 1.03 ≦ A / B ≦ 1.40.