JP2644250B2 - Dust boots for constant velocity joints - Google Patents

Description

The present invention relates to a dust boot for a constant velocity joint.

[Conventional technology]

In order to connect two axes with a certain angle without disagreement of axes, a universal joint (universal joint) is usually required. Of these, the angular velocity of the main drive shaft is always changed without change to the driven shaft. 2. Description of the Related Art Constant velocity joints that transmit rotation are often used in drive systems of vehicles and the like. In such an application, a rubber dust boot is used for a main part of the joint. Generally, the properties required as a dust boot material include a swingability of a constant velocity joint and a followability corresponding to a sliding movement. In addition to sealing properties against dust and muddy water entering from the outside world, shock resistance to vibration transmitted from the drive train, oil resistance to grease, low temperature resistance, heat resistance,
Has heat aging resistance and wear resistance. Among these, following ability, sealability, impact resistance, etc. will basically meet the requirements if rubber-like elastic material is selected as the material,
Conventionally, chloroprene rubber, which is one of diene rubbers, has been used in view of cost. In recent years, thermoplastic elastomers have been used for the purpose of improving impact resistance, expanding the service temperature range, and further reducing the weight, especially polyester-based or polyamide-based elastomers in terms of oil resistance and heat aging resistance. is there. However, any of the rubber-like elastic materials has very poor friction characteristics, and causes many problems. For example, when a constant velocity joint rotates at a high speed with a large joint angle, local contact occurs between adjacent bellows of this type of dust boot. That is, the first
A bellows-shaped dust boot 1 having two peaks and two valleys as illustrated in FIG.
Is attached to the outer periphery of the casing 4 by the small-diameter attachment portion 3 and the other large-diameter opening end is attached to the outer periphery of the casing 4 by the large-diameter attachment portion 5.
Can be bent, causing the sides of the adjacent ridges on the compressed side to come into contact with each other, causing frictional wear, resulting in a problem that the life of the boot is significantly shortened.

Therefore, by adding a solid lubricant, lubricating oil or wax to the dust boot rubber material, or by providing a resin layer having good self-lubricating property such as polyamide resin on the surface of the dust boot, Attempts have been made to improve the frictional characteristics of the steel to improve the wear resistance. However, even in these trials, when a solid lubricant is blended, the addition of a small amount is inferior in lubricity, and the addition of a large amount impairs the inherent properties of the rubber-like elastic body such as followability and sealability, and the lubricating oil Or, when waxes are blended, there are many drawbacks such as oil oozing out at the time of use at high temperatures and loss of lubricity, and at the same time, the sliding surface is contaminated with oils and foreign matter is easily attached. there were. Furthermore, in the method of coating the surface with a lubricating resin layer, the coating is applied to a certain degree (at least 10 μm) in order to exhibit effective lubrication performance.
As a result of the above-mentioned thickness being required, there have been problems such as adverse effects on the inherent properties of the rubber-like elastic body, such as excellent sealing properties and conformability, and the peeling of the coating film during use.

[Problems to be solved by the invention]

As described above, in the conventional technology, the function inherent in the dust boot formed of the rubber-like elastic material having the following ability, the sealing property, and the impact resistance is not reduced, and the friction characteristics and the wear resistance are not reduced. There is a problem that a dust boot for a constant velocity joint having improved durability and excellent durability cannot be obtained, and it has been a problem to solve this problem.

[Means for solving the problem]

In order to solve the above-mentioned problems, the present invention is to mix 1 to 80 parts by weight of a urethane-based rubber-like elastic body with 100 parts by weight of a non-urethane-based rubber-like elastic body such as a non-urethane-based rubber or a non-urethane-based thermoplastic elastomer. For a constant velocity joint having a coating made of a fluorinated polyether polymer having a unit containing a polar group showing reactivity or affinity for a urethane rubber-like elastic material on the bellows-like surface formed by It employs a means for forming a dust boot, and details thereof will be described below.

First, the non-urethane rubber elastic body of the present invention includes, for example, various diene rubbers such as natural rubber, butadiene rubber, isoprene rubber, chloroprene rubber, styrene butadiene rubber, acrylonitrile butadiene, ethylene propylene rubber, Non-urethane rubbers usually used by vulcanization with sulfur or peroxide such as olefin rubbers such as ethylene propylene diene rubber, acrylic rubber, and butyl rubber, or various non-urethanes such as polyester, polyamide, polyolefin, and polystyrene And other thermoplastic elastomers.

In addition, the non-urethane rubber-like elastic body, if necessary,
A vulcanizing agent may be added, and the vulcanizing agent is not particularly limited, and examples thereof include a sulfur-based one and an organic peroxide-based one.

Next, the urethane rubber-like elastic material used in the present invention is a polyester polyol, a polyether polyol,
It is a rubber-like elastic material obtained by reacting other polyols with isocyanate. Polyester polyols include polybasic acids (eg, adipic acid,
Succinic acid, sebacic acid, phthalic acid, other aliphatic or aromatic dicarboxylic acids, etc. and polyhydric alcohol polymers (eg, polyethylene glycol, polydiethylene glycol, polypropylene glycol, polydipropylene glycol, polybutylene glycol, other diol polymers) , A triol polymer, etc.) and a ring-opened polymer of a polyester polyol or a cyclic ester as a reaction product. Here, the molecular weight of the above polyhydric alcohol polymer is not particularly limited, but about 1,000 to 3,000 is appropriate in order to be a suitable rubbery elastic body. The polyether polyol is obtained by ring-opening polymerization of epoxide or tetrahydrofuran, and a polyether polyol obtained by adding an epoxide to a compound having at least two hydrogen atoms to which these cyclic ethers can be added is suitable. This epoxide is, for example, ethylene oxide, propylene oxide, butylene oxide, and the compound that provides a hydrogen atom that can be added to the cyclic ether is, for example, the above-mentioned polyhydric alcohol polymer, polyphenol, polyamide, or polyamine. The polyhydric alcohol polymer, that is, the molecular weight is not particularly limited, but polyethylene glycol (molecular weight of about 1,000 to 6,000), polypropylene glycol (molecular weight of about 1,000 to 2,000), polytetramethylene glycol, and the like are preferable. Other polyols include, for example, polybutadiene-based glycols, polyester polyols, and polycarbonate polyols composed of a homopolymer of butadiene or a copolymer with acrylonitrile or styrene. Further, as the isocyanate, a polyisocyanate having two or more aliphatic or aromatic functional groups is required. However, as the number of functional groups increases, crosslinking becomes easier and the rubber elasticity is lost. Since there is a possibility of adversely affecting the rubber elasticity of the elastic body, for example, hexamethylene-1,6-diisocyanate, toluene-2,4
Diisocyanates such as diisocyanate, metaphenylene diisocyanate, naphthalene-1,5-diisocyanate and diphenylmethane-4,4'-diisocyanate are preferred.

Such a urethane rubber-like elastic material forms a prepolymer composed of various polyols and isocyanate, and a crosslinking agent such as 1,4-butanediol, methylenebisdichloroaniline, trimethylolpropane, and triisopropanolamine is added thereto. It may be cross-linked, or may be a urethane-based thermoplastic elastomer such as a bifunctional polyol constituting a soft segment, a block copolymer comprising a combination of three components of a short-chain glycol and a diisocyanate constituting a hard segment. However, this does not cause any trouble to the present invention.

The amount of the urethane-based rubber-like elastic body added is 1 part by weight or more, preferably 5 parts by weight or more and 80 parts by weight or less based on 100 parts by weight of the non-urethane-based rubber-like elastic body. This is because if the amount is less than 1 part by weight, the effect of improving the reactivity or affinity with the polar group of the film coated on the surface of the molded article is insufficient. This is because the free polar groups of the coating that are not involved in the adhesion to the elastic base material adversely affect the lubricity and abrasion resistance. Is inherently inferior in water resistance, which adversely affects the water resistance of the dust boot.

Incidentally, the rubber-like elastic body of the present invention, if necessary,
Various additives commonly used in the rubber industry can be used as appropriate. Examples of the additives include carbon black, silica, clay, calcium carbonate, magnesium carbonate, magnesium hydroxide, aluminum hydroxide, aluminum oxide, talc, mica, kaolinite, bentonite, shirasu, silicon carbide, aramid resin, and phenol resin. Fillers such as powder or fiber, zinc white,
Vulcanization aids such as fatty acids, guanidines, sulfides,
Aldehyde-vulcanization accelerators such as amines, stabilizers such as zinc stearate, lead phosphite, barium phosphite, plasticizers such as dimethyl phthalate and dioctyl phthalate, amines, aging inhibitors such as phenols, Antioxidants such as 2,6-di-t-butyl-p-cresol, ultraviolet absorbers such as acrylonitrile derivatives, flame retardants such as antimony oxide and zircon oxide, coloring agents such as cadmium yellow, phthalocyanine blue, and titanium white Can be mentioned.

The method of mixing the rubber-like elastic material compound in the present invention may be a conventionally well-known method, and is not particularly limited. Examples thereof include a non-urethane rubber-like elastic material and a urethane rubber-like elastic material. Vulcanizing agent for rubber, rubber compounding agent, etc. may be kneaded with an open roll, Banbury mixer, kneader, etc. When using thermoplastic elastomer as a non-urethane rubbery elastic body, kneading with a melt extruder May be.

Pressed, calender roll,
What is necessary is just to shape | mold and vulcanize using an extruder or an injection molding machine.

Next, the polar group showing reactivity or affinity for the urethane rubber-like elastic material of the present invention is, for example, -NC
O, -OH, -COOH, -NHR (where R is hydrogen, an alkyl group or an alkoxy group), -SH, —COOCH ₃ , —SO ₃ H, —SO ₂ F, and the like, and a fluorinated polyether polymer having a unit containing such a polar group is —C _X F _2X —O— (where X is 1 to Is a polymer having an average molecular weight of about 1,000 to 10,000 with a main structural unit of (an integer of 4), a perfluoropolyether group for improving lubricity and abrasion resistance, and a polar group for a fluorinated polyether polymer film. It helps to improve the adhesion between the rubber and the urethane rubber-like elastic material. As described above, the urethane rubber-like elastic body of the present invention is formed based on a urethane bond formed by a reaction between an isocyanate and an active hydrogen group. In addition to such a bond, a urea bond, a burette bond, an allophanate It may also include a bond or the like, or -NCO, -O
H, since often remain functional groups such as -NH _2, urethane bonds in a supra polar groups, active hydrogen urea bond or the like has, reactivity to -OH group or -NH ₂ group -N
CO, Such as -OH, -NMR, -COOH, -SH, etc., which are reactive toward the side chain or terminal -NCO group,
Those in which these groups are located at both terminals of the fluorinated polyether polymer are most effective and particularly preferred. Also,-
Since abrasion resistance is further improved if a fluorinated polyether polymer having a unit containing NCO and a fluorinated polyether polymer having a unit containing -OH are used in combination, a unit containing a different kind of polar group is used. It is also possible to use different kinds of fluorinated polyether polymers in combination. Specific examples of the above-mentioned fluorinated polyether polymer are as follows, and it goes without saying that there is no problem even when these are used alone or in combination. _{That, OCN-C 6 H 3 (} CH 3) -NHCOCF 2 C 2 F 4 O m CF 2 O n CF 2 CONH-C 6 H 3 (CH 3) -NCO, HOOC-CF 2 OC 2 F 4 O m CF ₂ O _n CF ₂ COOH, _{OCH 3 COOC-CF 2 OC 2} F 4 O m CF 2 O n CF 2 COOCH 3, HOOC 2 -CF 2 OC 2 F 4 O m CF 2 O n CH 2 OH, HOCH 2 2 NHCO-CF 2 OC 2 F ₄ O _m CF ₂ O _n CF ₂ CONHCH _{2 2} OH, _{H 2 NCH 2 2 NHCO-CF} 2 OC 2 F 4 O m CF 2 O n CF 2 CONHCH 2 2 NH 2, and the like, further polar group is a hydroxyl group fluorinated polyether polymer and various polyfluoro poly Adopting a method in which an isocyanate containing no ether group is used in combination, or a method in which a fluorinated polyether polymer in which a polar group is an isocyanate group and a diamine, triamine, diol, or triol containing no polyfluoropolyether group are used in combination May be.

The fluorinated polyether polymer of the present invention is reactive with the urethane rubber-like elastic material or the fluorinated polyether polymer as long as it does not adversely affect the properties of the fluorinated polyether polymer such as lubricity, abrasion resistance and adhesion to a substrate. An organopolysiloxane or polyfluoroalkyl polymer having a certain polar group may be appropriately added, but in order to maintain extremely excellent abrasion resistance, the fluorinated polyether polymer may be the main structural unit. desirable.

In order to form such a film of the fluorinated polyether polymer, generally, an organic solvent (for example, ketones such as acetone and methyl ethyl ketone, esters such as methyl acetate, ethyl acetate and isoamyl acetate, diethyl ether and dioxane) are used. Ethers, methyl chloroform, trichloroethylene, tetrachloroethylene, tetrachlorodifluoroethane, 1,1,2-trichloro-1,2,2
-A coating liquid obtained by dissolving or dispersing a fluorinated polyether polymer to an appropriate viscosity in one or a mixture of two or more halogenated hydrocarbons such as trifluoroethane [Freon 113] What is necessary is just to spray on an elastic body or to immerse an elastic body in a coating liquid, but the immersion method is preferable from the viewpoint of saving the consumption of a coating liquid. The concentration of the fluorinated polyether polymer in the coating solution is not particularly limited, but is about 0.3 to 10.0% by weight in terms of cost, and 0.5 in consideration of the characteristics of the formed thin film.
It can be said that about 5.0% by weight is preferable. Further, after the coating film is formed, it is dried, and its surface is polished with a soft cloth or paper to give a gloss. However, such an operation may remove excess fluorinated polyether polymer at the same time. because,
If the coating is too thick, it will contain an excess of fluorinated polyether polymer in the coating, and as a result will have many free reactive groups that are not involved in adhesion to the urethane-based rubber-like elastic material. This is because it has an adverse effect on the lubricity and wear resistance which are indispensable. The main purpose of drying after forming the coating film is to remove the organic solvent.However, in order to increase the reactivity between the polymer in the coating film and the base material, the film may be heated during drying or may be subjected to a heat treatment after drying. May be appropriately inserted.

〔Example〕

The dust boot for a constant velocity joint used in the examples and the comparative rows is a bellows having two peaks and two valleys (grooves) as shown in FIG. 1, and the dust boot 1 has one small-diameter open end. The other end of the large-diameter opening is mounted on the outer periphery of the casing 4 by the large-diameter mounting portion 5.

As shown in FIG. 2, the dust boot 1 is composed of a main body 6 and a coating 7 made of a composition having the mixing ratio (parts by weight) of the raw materials shown in Table 1.

Raw materials used in Examples and Comparative Examples are collectively shown as follows. In addition, abbreviations are shown in [].

A Non-urethane rubber-like elastic material: Chloroprene rubber [CR] (Toyo Soda Kogyo Co., Ltd .: B-11) Polyester thermoplastic elastomer [PE-TPE]
(Toray DuPont: Hytrel 5557), B Urethane rubber-like elastic material: Polyester urethane polymer [URE-R] (West German Bayer: Urethane 600) Urethane thermoplastic elastomer [URE-TPE] (Nippon Cyanamid) Company: Cyanaprene Thermoplastic 1850), Vulcanizing agent for C urethane: (Manufactured by Bayer AG, Desmodur TT, having the above structure), D Various additives: carbon [carbon] (HAF, manufactured by Asahi Carbon Co., Ltd.), talc [talc] (manufactured by Nippon Taishi Seimitsu Co., Ltd.), sulfur [sulfur] (Manufactured by Hosoi Chemical Co., Ltd.), zinc white [vulcanization aid-1] (manufactured by Mitsui Kinzoku Co., Ltd.), stearic acid [vulcanization aid-2], N-cyclohexyl-2-benzothiallylsulfenamide [vulcanization acceleration] Agent-1] (manufactured by Ouchi Shinko Kasei Mining Co., Ltd.), tetramethyltyrium disulfide
2) (manufactured by the same company), dioctyl phthalate [plasticizer-1] (manufactured by Kurokin Oil Co., Ltd.), wax-based antioxidant [aging agent] (manufactured by Ouchi Shinko Chemical Co., Ltd .: Sannock CW), F film forming material : Hydroxyl group-containing polyfluoroether [HO-FCO] (manufactured by Montefluos Italy: Fomblin Z DOL-2000, molecular weight: about 20)
_{00) HOCH 2 -CF 2 OC 2} F 4 O m CF 2- O n CF 2 CH 2 OH free functional groups polyfluoroether [FCO] (ibid Co.: Fo
mblin Z 25, molecular weight about 15000) Hydroxyl-containing organopolysiloxane [HO-SIL] (manufactured by Shin-Etsu Chemical Co., Ltd .: silicone oil diol X-22-160)
C) Hydroxyl-containing polyfluoroalkyl [HO-FC] C ₈ F ₁₇ C ₂ H ₄ OH, Examples 1-3: Dust boots were prepared in the proportions shown in Table 1 (parts by weight, hereinafter the same), [HO-FCO] was used as the fluorinated polyether polymer as the coating forming material. The fluorinated polyether polymer was dissolved in Freon 113 so as to have a concentration of 2.0% to obtain a coating solution for dipping the dust boot. Dust boots immersed in this coating solution are 70 ° C,
After the heat treatment for one hour, it was subjected to a durability test.
The durability test conditions were as follows: ambient temperature -5 ° C, constant angle joint angle 30deg, rotation speed 400rpm, grease was sealed in the dust boot, and continuous operation was performed for 50 hours. The time (h) was determined. In the case where no hole was formed even after 50 hours, the limit was set to 50 hours. The obtained test results are
Also shown in the table.

Comparative Examples 1 to 6: Dust boots were produced by performing the same operations as in Example 1 at the compounding ratios shown in Table 2. As shown in Table 2, [HO-FCO], [FCO], [HO-SI
L], f [HO-FC] and the like. The preparation method of the coating liquid and the durability test method were the same as those in Example 1, and the obtained results were Also shown in the table.

As is clear from Tables 1 and 2, Examples 1 to
Comparative Example 1 and Comparative Example 2 in which the covering portion 7 was not formed while the dust boot of Example 3 had an excellent durability life. Comparative Example 3, which did not include the rubber-based elastic body, and Comparative Examples 4 to 6, in which the coating was other than that specified in the present invention even when the coating 7 was formed, all had a short durability life. It turns out that it is inferior as a dust boot.

〔effect〕

As described above, the dust boot for a constant velocity joint according to the present invention reduces the characteristics inherent to the dust boot made of a rubber-like elastic body, such as followability, sealability, and impact resistance. In addition, not only are the friction characteristics and abrasion resistance excellent, but also the coating layer is excellent in weather resistance, and the durability is further improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an essential part illustrating an embodiment of a dust boot, and FIG. 2 is a partial sectional view of a main body (bellows) of the dust boot of the present invention. DESCRIPTION OF SYMBOLS 1 ... Dust boot, 2 ... Shaft part, 3 ... Small diameter mounting part, 4 ... Casing, 5 ... Large diameter mounting part, 6 ... Body part, 7 ... Cover part.

Claims (1)

(57) [Claims] 1. A bellows-like shape formed by mixing 1 to 80 parts by weight of a urethane rubber-like elastic body with 100 parts by weight of a non-urethane rubber-like elastic body such as a non-urethane rubber or a non-urethane thermoplastic elastomer. For a constant velocity joint, a coating made of a fluorinated polyether polymer having a unit containing a polar group having reactivity or affinity with the urethane rubber-like elastic material is provided on the surface of the dust boot. Dust boots.