JP2005299692A - Constant velocity joint boot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joint boot made of thermoplastic elastomer resin, attached to an outer case having a non-circular outer peripheral shape, having excellent molding property, and capable of ensuring sufficient strength. <P>SOLUTION: This constant velocity joint boot made of thermoplastic elastomer resin is provided with a large diameter side mounting part attached to the outer case having the non-circular outer peripheral shape, a small diameter side mounting part attached to a shaft, and a bellows part connecting both of them integrally. The large diameter side mounting part has a circular outer peripheral shape, and an inner peripheral side shape has a plurality of projecting parts in the peripheral direction by corresponding to the non-circular outer peripheral shape of the outer case. A ratio of height a on an inner peripheral side of these projecting parts to height b on an outer peripheral side is a/b<0.8. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a constant velocity joint boot made of a thermoplastic elastomer resin, and more particularly to a bellows-like thermoplastic elastomer resin joint boot used for a constant velocity joint of an automobile.

  A triport type joint is known as one of constant velocity joints used for vehicle drive shafts (Patent Document 1).

  The triport type constant velocity joint is provided at the end of the other shaft and the triport formed by projecting three trunnions with rollers on the input side and output side shafts in the direction perpendicular to the axis. It consists of an outer case. The outer case has three sliding grooves in the axial direction corresponding to the tripod on the inner periphery thereof. The constant velocity joint is configured to transmit the rotational torque while allowing the shafts to be angled by fitting the triport roller slidably in the axial direction with respect to the sliding groove. .

  In such a constant velocity joint, a joint boot having an accordion shape is generally mounted so as to cover the portion of the shaft on the triport side from the outer case. In the triport type constant velocity joint, the outer case has an uneven shape in the circumferential direction corresponding to the arrangement of the sliding groove on the inner periphery for weight reduction and the like. That is, the outer case has a non-circular outer peripheral shape having three recessed portions that are equally arranged in the circumferential direction.

Therefore, the large-diameter side attachment portion of the joint boot attached to the outer case has a noncircular shape whose inner peripheral shape corresponds to the outer peripheral shape of the outer case. That is, the inner periphery of the large-diameter side mounting portion protrudes inwardly at three locations in the circumferential direction corresponding to the concave portion of the outer case, and this protruding portion is formed as a thick portion.
JP 2003-329059 A

However, in the above joint boot, since the thick wall portion and the thin wall portion are alternately formed in the circumferential direction of the large diameter side mounting portion, when the thermoplastic elastomer resin is injection molded, the outer peripheral surface of the large diameter side mounting portion. In particular, there is a problem that a weld portion is generated on the outer peripheral surface of the thick portion. This means that when stress is applied to the outer peripheral surface of the large-diameter side attachment portion, the weld portion opens and breaks.
The present invention has been made in view of such points, and in a thermoplastic elastomer resin joint boot attached to a non-circular outer shape outer case like a triport type constant velocity joint, the moldability is improved. An object is to provide an excellent and sufficient strength.

  As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, the present invention is made of a thermoplastic elastomer resin including a large-diameter side attachment portion attached to a non-circular outer peripheral outer case, a small-diameter side attachment portion attached to a shaft, and a bellows portion integrally connecting the two. In the boot for a quick joint, the large-diameter side attachment portion has a circular outer peripheral shape, and the inner peripheral side shape has a plurality of convex portions in the circumferential direction corresponding to the non-circular outer peripheral shape of the outer case. The constant velocity joint boot is characterized in that the ratio of the height a on the inner peripheral side to the height b on the outer peripheral side of these convex portions is a / b <0.8.

  As a preferred embodiment, the present invention relates to a constant velocity joint boot characterized in that there are three convex portions on the inner peripheral side of the large diameter side attaching portion.

  As a preferred embodiment, the present invention relates to a constant velocity joint boot characterized in that the number of peaks of the bellows portion is 3 to 5.

  As a preferred embodiment, the present invention relates to a constant velocity joint boot which is injection-molded by a disk gate from a small diameter side mounting portion.

  As a preferred embodiment, the present invention relates to a constant velocity joint boot characterized by being injection-molded by an injection molding machine having an air hole capable of emitting air to a disk gate of a core mold.

  As a preferred embodiment, the present invention relates to a constant velocity joint boot characterized in that the thermoplastic elastomer resin is made of an acrylic block copolymer.

  A preferred embodiment relates to a constant velocity joint boot, wherein the thermoplastic elastomer resin is a composition comprising an acrylic block copolymer and a polyorganosiloxane graft polymer.

  In a preferred embodiment, the thermoplastic elastomer resin is a composition comprising an acrylic block copolymer, a polyorganosiloxane graft polymer, a thermoplastic resin, a lubricant, and an inorganic filler. Regarding boots.

  According to the present invention, when a thermoplastic elastomer resin is injection-molded, a welded portion is not generated on the outer peripheral surface of the large-diameter side mounting portion, particularly on the outer peripheral surface of the thick-walled portion. You can get fast joint boots.

  Embodiments of the present invention will be described in detail with reference to the drawings based on examples, but the present invention is not limited thereto.

  FIG. 1 is a half sectional view of a joint boot made of thermoplastic elastomer resin according to the present embodiment. This joint boot consists of a large-diameter side mounting part attached to a non-circular outer shape outer case with three recesses like a triport type constant velocity joint, and a small-diameter side mounting part attached to the shaft. A boot for a constant velocity joint made of a thermoplastic elastomer resin, comprising a bellows part connected integrally.

  The large-diameter side mounting portion has a circular outer peripheral shape, and the inner peripheral side shape has a plurality of convex portions in the circumferential direction corresponding to the non-circular outer peripheral shape of the outer case. is there. When there are three concave portions in the outer case, the number of convex portions needs to be three.

  The ratio between the height a on the inner peripheral side of these convex portions and the height b on the outer peripheral side needs to be a / b <0.8, and when a / b is larger than 0.8, In addition, welds may occur on the outer peripheral surface of the large-diameter side mounting portion, particularly on the outer peripheral surface of the thick-walled portion.

  The number of crests of the bellows portion is preferably 3 to 5 from the viewpoints of processability of injection molding and expandability when the bellows rotates. If the number of bellows is less than two, it may be difficult to remove the injection molding. When the number of bellows is more than five, the thickness becomes thin and may expand and break during rotation.

  The injection mold and molding method will be described. The mold is composed of a cavity and a core, and the gate position and shape are preferably injection-molded with a disk gate from the small-diameter side attachment portion side in order to reduce the distortion of the boot shape after molding. Further, it is preferable to have an air hole that can emit air on the disk gate side of the core mold so that the mold can be easily removed from the mold after injection molding. It is preferable that the air hole of the core mold is closed so that the resin does not enter the hole at the time of molding when the resin is injected, and at the time of demolding, the hole is opened at the same time as the mold is opened.

  The thermoplastic elastomer resin is preferably an acrylic block copolymer that is excellent in moldability, heat resistance, oil resistance, and compression set and has a small tensile set. When low temperature characteristics are required, a composition comprising an acrylic block copolymer and a polyorganosiloxane graft polymer is preferable. Furthermore, when the elastic modulus at a high temperature is required, it is preferably a composition comprising an acrylic block copolymer, a polyorganosiloxane graft polymer, a thermoplastic resin, a lubricant and an inorganic filler.

  The acrylic block copolymer will be described. The structure of the acrylic block copolymer is preferably a linear acrylic block copolymer from the viewpoint of cost and ease of polymerization. The linear acrylic block copolymer includes an acrylic polymer block (a) constituting the acrylic block copolymer (hereinafter also referred to as polymer block (a) or block (a)) and methacrylic. From the viewpoint of easy handling at the time of processing and physical properties when the polymer block (b) (hereinafter, also referred to as polymer block (b) or block (b)) is made into a composition, ba-b-b A type of triblock copolymer or a mixture thereof is preferred. In the acrylic block copolymer, the general formula (1):

（式中、Ｒ¹は水素原子またはメチル基で、互いに同一でも異なっていてもよい、ｐは０または１の整数、ｑは０〜３の整数）で表わされる単位（ｃ）を有することが好ましい。単位（ｃ）は、酸無水物基を含有する単位（ｃ１）及び／又はカルボキシル基を含有する単位（ｃ２）からなる単位であり、アクリル系重合体ブロック（ａ）及びメタアクリル系重合体ブロック（ｂ）の少なくとも一方の重合体ブロックあたりに１個以上含まれていればよく、その数が２個以上の場合には、その単量体が重合されている様式はランダム共重合であってもよくブロック共重合であってもよい。

(Wherein R ¹ is a hydrogen atom or a methyl group, which may be the same or different from each other, p is an integer of 0 or 1, q is an integer of 0 to 3) preferable. The unit (c) is a unit composed of a unit (c1) containing an acid anhydride group and / or a unit (c2) containing a carboxyl group, and an acrylic polymer block (a) and a methacrylic polymer block. It is sufficient that at least one polymer block is contained per at least one polymer block of (b). When the number is two or more, the mode in which the monomers are polymerized is random copolymerization. Or block copolymerization.

  The number average molecular weight of the acrylic block copolymer measured by gel permeation chromatography is preferably 30,000 to 500,000, more preferably 40,000 to 400,000, and further 50,000 to 30,000. preferable. If the molecular weight is less than 30,000, sufficient mechanical properties as an elastomer may not be exhibited, and if it exceeds 500,000, the processing properties may deteriorate.

  The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured by gel permeation chromatography of the acrylic block copolymer is preferably 1-2, More preferably, it is .8. If Mw / Mn exceeds 2, the uniformity of the acrylic block copolymer may be lowered. In the present invention, the number average molecular weight and the weight average molecular weight were measured by gel permeation chromatography using chloroform as a mobile phase and determining the molecular weight in terms of polystyrene.

  The composition ratio of the acrylic polymer block (a) and the methacrylic polymer block (b) constituting the acrylic block copolymer is the required physical properties, the moldability required during processing of the composition, and What is necessary is just to determine from the molecular weight etc. which are each required for an acrylic polymer block (a) and a methacrylic polymer block (b). When the range of the composition ratio of a preferable acrylic polymer block (a) and a methacrylic polymer block (b) is illustrated, the acrylic polymer block (a) is 40 to 90% by weight, and further 45 to 80% by weight. In particular, 50 to 70% by weight, methacrylic polymer block (b) is preferably 60 to 10% by weight, more preferably 55 to 20% by weight, and particularly preferably 50 to 30% by weight. When the proportion of the acrylic polymer block (a) is less than 40% by weight, the mechanical properties as an elastomer, particularly the elongation at break may be lowered or the flexibility may be lowered. May decrease the mechanical strength.

The relationship between the glass transition temperatures of the acrylic polymer block (a) and the methacrylic polymer block (b) constituting the acrylic block copolymer is expressed as Tg of the glass transition temperature of the acrylic polymer block (a). It is preferable that the relationship of Tg _a <Tg _b is satisfied when _a and methacrylic polymer block (b) are Tg _b .

  As a polymerization method for producing the acrylic block copolymer, controlled polymerization is preferably used. Examples of the controlled polymerization include living anion polymerization, radical polymerization using a chain transfer agent, and recently developed living radical polymerization. Living radical polymerization is preferable from the viewpoint of controlling the molecular weight and structure of the block copolymer and copolymerizing a monomer having a crosslinkable functional group.

  Living polymerisation, in the narrow sense, indicates that the terminal always has activity, but generally also includes pseudo-living polymerization where the terminal is inactive and the terminal is in equilibrium. The living radical polymerization in the present invention is a radical polymerization in which the polymerization terminal is activated and deactivated is maintained in an equilibrium state, and has been actively studied in various groups in recent years. .

  Examples thereof include those using a chain transfer agent such as polysulfide, those using a radical scavenger such as a cobalt porphyrin complex (Journal of American Chemical Society, 1994, 116, 7943) or a nitroxide compound (Macromolecules, 1994, 27, 7228). ), Atom transfer radical polymerization (ATRP) using an organic halide as an initiator and a transition metal complex as a catalyst. In the present invention, there is no particular limitation as to which of these methods is used, but atom transfer radical polymerization is preferred from the viewpoint of ease of control.

  The polyorganosiloxane graft polymer will be described. The polyorganosiloxane graft polymer is blended and dispersed in an acrylic block copolymer which is a matrix resin of the present composition. Even when the temperature is not higher than the embrittlement temperature of the acrylic block copolymer alone, which is a matrix resin, no breakage due to embrittlement occurs, and it is possible to develop good low-temperature characteristics. Moreover, the improvement effect can be expressed also about low temperature characteristics, such as elastic recovery characteristics (TR characteristics) at low temperature, and it is possible to improve low temperature elastic recovery temperature and tensile permanent strain characteristics at low temperature. Furthermore, various properties that can be inherently exhibited by polyorganosiloxane (molding property such as mold releasability, slidability, flame retardancy, etc.) can be imparted.

  The polyorganosiloxane-based graft polymer is not particularly limited in composition, but in the presence of 40 to 95% by weight of polyorganosiloxane (d1), 0 to 10% by weight of monomer (d2) is polymerized, and A copolymer obtained by polymerizing 5 to 60% by weight of the vinyl monomer (d3) (100% by weight in total of (d1), (d2) and (d3)) is preferable. The monomer (d2) is composed of 50 to 100% by weight of a polyfunctional monomer (x) containing two or more polymerizable unsaturated bonds in the molecule, and other copolymerizable vinyl monomers ( y) A monomer composed of 0 to 50% by weight. Furthermore, it is preferable that the content of the graft component combining the monomer (d2) and the vinyl monomer (d3) is 5 to 40% by weight and the polyorganosiloxane content is 95 to 60% by weight.

  In the acrylic block copolymer composition, a lubricant, an inorganic filler, and a thermoplastic resin can be blended in order to increase the elastic modulus at a high temperature. Regarding the blending amount, 10 to 100 parts by weight of the polyorganosiloxane graft polymer, 0.1 to 10 parts by weight of the lubricant, and 0.1 to 100 parts by weight of the inorganic filler with respect to 100 parts by weight of the acrylic block copolymer. A preferred range is 0.1 to 100 parts by weight of a thermoplastic resin.

  Examples of the lubricant include fatty acids such as stearic acid and palmitic acid, fatty acid metal salts such as calcium stearate, zinc stearate, magnesium stearate, potassium palmitate and sodium palmitate, polyethylene wax, polypropylene wax, and montanic acid wax. Waxes, low molecular weight polyolefins such as low molecular weight polyethylene and low molecular weight polypropylene, polyorganosiloxanes such as dimethylpolysiloxane, octadecylamines, alkyl phosphates, fatty acid esters, amide based lubricants such as ethylene bisstearamide, 4-fluoro Examples thereof include, but are not limited to, fluororesin powder such as fluorinated ethylene resin, molybdenum disulfide powder, silicone resin powder, silicone rubber powder, and silica. These may be used alone or in combination of two or more. Of these, stearic acid, zinc stearate, calcium stearate, magnesium stearate, and stearyl amide are preferred from the viewpoint of low friction and processability on the resin surface.

  Examples of inorganic fillers include titanium oxide, zinc sulfide, zinc oxide, carbon black, calcium carbonate, calcium silicate, clay, kaolin, silica, mica powder, alumina, glass fiber, metal fiber, california titanate, asbestos. , Wollastonite, mica, talc, glass flake, milled fiber, metal powder, and the like, but are not limited thereto. These may be used alone or in combination. Among these, carbon black and titanium oxide are preferable from the viewpoint of high elastic modulus and silica and weather resistance and pigment.

  Examples of the thermoplastic resin include polyvinyl chloride resin, polyethylene resin, polypropylene resin, cyclic olefin copolymer resin, polymethyl methacrylate resin, polystyrene resin, polyphenylene ether resin, polycarbonate resin, polyester resin, Examples thereof include polyamide resins, polyacetal resins, polyphenylene sulfide resins, polysulfone resins, polyimide resins, polyetherimide resins, polyetherketone resins, polyetheretherketone resins, polyamideimide resins, and imidized polymethylmethacrylate resins. These may be used alone or in combination of two or more. Among these, those having good compatibility with the acrylic block copolymer are preferably used, and those having a functional group capable of reacting with an acid anhydride group are more preferably used. Examples of the functional group capable of reacting with the acid anhydride group include an amino group and a hydroxyl group, and examples of the thermoplastic resin having these include polyester resins and polyamide resins. Thermoplastic resins containing functional groups that react with acid anhydride groups other than these can also be suitably used.

  The composition of the present invention further includes a stabilizer (anti-aging agent, light stabilizer, UV absorber, etc.), flexibility imparting agent, mold release agent, compatibilizing agent and other thermoplastic elastomers depending on the required properties. Etc. may be added. These additives may be appropriately selected and used according to the required physical properties, workability, and the like.

  For example, as the compatibilizing agent, Kraton series (manufactured by Shell Japan Co., Ltd.), Tuftec series (manufactured by Asahi Kasei Kogyo Co., Ltd.), Dynalon (manufactured by Nippon Synthetic Rubber Co., Ltd.), Epofriend (Daicel Chemical Industries, Ltd.) ), Septon (manufactured by Kuraray Co., Ltd.), Nofaloy (manufactured by Nippon Oil & Fats Co., Ltd.), Lexpearl (manufactured by Nippon Polyolefin Co., Ltd.), Bond First (manufactured by Sumitomo Chemical Co., Ltd.), Bondine (Sumitomo Chemical) Industrial Co., Ltd.), Admer (Mitsui Chemicals Co., Ltd.), Umex (Sanyo Chemical Industries Co., Ltd.), VMX (Mitsubishi Chemical Co., Ltd.), Modiper (Nippon Yushi Co., Ltd.), Staphyloid Commercial products such as (Takeda Pharmaceutical Co., Ltd.) and Reeta (Toa Gosei Co., Ltd.) can be mentioned.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

(Example 1)
Polymerization is performed at a charging ratio of 33.8 L (235.5 mol) of butyl acrylate, 32.1 L (296 mol) of ethyl acrylate and 18.2 L (141.3 mol) of methoxyethyl acrylate by living radical polymerization, and the conversion rate of butyl acrylate is When the conversion rate of 96%, the conversion rate of ethyl acrylate is 95%, and the conversion rate of 2methoxyethyl acrylate is 96%, tertiary hard butyl methacrylate 40.5L (249.9 mol), methyl methacrylate 17.8L (166 .6 mol) was added. The reaction was terminated when the conversion rate of tertiary butyl methacrylate was 95% and the conversion rate of methyl methacrylate was 92%, and Irganox 1010 (Ciba Specialty Chemicals) was added to 100 parts by weight of the obtained polymer. (Made by Co., Ltd.) 0.3 parts by weight was blended and extruded and kneaded at a temperature of 240 ° C. with a vented twin screw extruder (44 mm, L / D = 42.25) (manufactured by Nippon Steel). A triblock-structured acid anhydride base-containing acrylic block copolymer pellet was obtained.

  A polyorganosiloxane content of 70% by weight by emulsion polymerization is graft copolymerized with 13.5% by weight of butyl methacrylate, 15.6% by weight of methyl methacrylate and 0.9% by weight of ethyl acrylate. A siloxane-based graft polymer powder was obtained.

By hand blending 727 g of the obtained acrylic block copolymer, 472.7 g of polyorganosiloxane graft polymer and 7 g of inorganic filler (Asahi Carbon Co., Ltd./Asahi # 15) were uniformly dispersed. Mix well. The kneading conditions are C1-C4: 50 ° C., C5: 100 ° C., C6: 150 ° C., C7: 200 ° C., die head: 220 ° C., rotation speed: 100 rpm, 100 mesh, 150 mesh, 100 mesh stainless steel wire mesh at the die part. Were melt-kneaded with a vented twin screw extruder “TEX30HSS-25.5PW-2V” (manufactured by Nippon Steel Works) to obtain pellets of an acrylic block copolymer composition. Pellets obtained by drying at 80 ° C. for 3 hours or more were injected on the inner peripheral side of the convex portion of the inner peripheral side with an injection molding machine “J150E-P” (manufactured by Nippon Steel Co., Ltd.) with a clamping pressure of 150 TON. A core mold and a cavity mold that are joint boots with a height of a13 mm and outer height b of 17 mm. The core is injection molded at a nozzle temperature of 240 ° C., an injection pressure of 50%, an injection speed of 10%, and a mold temperature of 80 ° C. The mold was removed at an air pressure of 5 kg / cm ² emitted from the mold to obtain a constant velocity joint boot. Table 1 shows the results of the surface condition on the outer peripheral side (thick part) of the large-diameter side attachment part.

(Comparative Example 1)
Example 1 except that the injection mold is a core mold and a cavity mold that are joint boots having an inner peripheral side height a17 mm and an outer peripheral side height b17 mm of the convex part of the inner peripheral side shape. Under the same conditions, injection molding was performed to obtain a constant velocity joint boot. Table 1 shows the results of the surface condition on the outer peripheral side (thick part) of the large-diameter side attachment part.

表１の結果から明らかのように、ａ／ｂ＜０．８である実施例１において、大径側取付部の外周側の表面状態（肉厚部）にウェルド部が発生していないことがわかる。

As is clear from the results in Table 1, in Example 1 where a / b <0.8, no weld portion is generated in the surface state (thick portion) on the outer peripheral side of the large-diameter side attachment portion. Understand.

It is a half sectional view of a joint boot.

Explanation of symbols

1 Large diameter side mounting part 2 Small diameter side mounting part 3 Bellows part

Claims (8)

  In a boot for a constant velocity joint made of a thermoplastic elastomer resin, comprising a large-diameter side attaching portion attached to a non-circular outer peripheral outer case, a small-diameter side attaching portion attached to a shaft, and a bellows portion integrally connecting the two. The large-diameter side attachment portion has a circular outer peripheral shape, and the inner peripheral side shape has a plurality of convex portions in the circumferential direction corresponding to the non-circular outer peripheral shape of the outer case. A constant velocity joint boot characterized in that the ratio of the height a on the inner peripheral side to the height b on the outer peripheral side of these convex portions is a / b <0.8.   The constant velocity joint boot according to claim 1, wherein the number of convex portions on the inner peripheral side of the large-diameter side attachment portion is three.   3. The constant velocity joint boot according to claim 1, wherein the number of peaks of the bellows portion is 3 to 5. 3.   The constant velocity joint boot according to any one of claims 1 to 3, wherein injection molding is performed by a disk gate from a small diameter side mounting portion.   5. The constant velocity joint boot according to claim 1, wherein injection molding is performed by an injection molding machine having an air hole capable of emitting air to a disk gate of a core mold.   The constant velocity joint boot according to any one of claims 1 to 5, wherein the thermoplastic elastomer resin is made of an acrylic block copolymer.   The constant velocity joint boot according to any one of claims 1 to 6, wherein the thermoplastic elastomer resin is a composition comprising an acrylic block copolymer and a polyorganosiloxane graft polymer.   8. The thermoplastic elastomer resin is a composition comprising an acrylic block copolymer, a polyorganosiloxane graft polymer, a thermoplastic resin, a lubricant, and an inorganic filler. Constant velocity joint boots.

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