JP2002372062A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing with a long service life, provided with a sealing device with excellent sealing performance even in inferior environment and particularly suitable for a wheel. SOLUTION: This rolling bearing is provided with an outer ring having an outer ring raceway track on the inner peripheral surface; an inner ring having an inner ring raceway track on the outer peripheral surface; a plurality of rolling elements rollably provided between the outer ring raceway track and the inner ring raceway track; and a sealing device for closing the axial opening part of a space provided with the rolling elements between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring. An elastic member constituting the sealing device is formed of a vulcanizable rubber composition composed by mixing at least carbon black in carboxylated acrylonitrile-butadiene rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to prevent leakage of encapsulated grease and prevent external
The present invention relates to a rolling bearing provided with a sealing device for preventing water, muddy water and the like from entering the inside of the bearing.

[0002]

2. Description of the Related Art As a rolling bearing for a vehicle wheel, for example, a rolling bearing having the structure shown in FIG. 1 is known. In the illustrated rolling bearing O, an outer ring-equivalent member 1 which is a fixed ring
Is supported and fixed to a suspension device (not shown) by a mounting portion 2 formed on the outer peripheral surface thereof. Therefore, the outer ring equivalent member 1 does not rotate during use. Inside such an outer ring equivalent member 1, an inner ring equivalent member 3 which is a rotating wheel is provided concentrically with the outer ring equivalent member 1, and the inner ring equivalent member 3 is used when used.
Rotates. The inner ring-equivalent member 3 includes a hub 4 and an inner ring 5. A spline groove 6 is formed on the inner peripheral surface of the hub 4, and a mounting flange 7 is formed on the outer peripheral surface (the left end in FIG. 1, which is the outer side in the width direction when assembled to the vehicle).
Each is formed. At the time of assembling to a vehicle, a drive shaft that is rotationally driven via a constant velocity joint is inserted into the spline groove 6, and wheels are fixed to the mounting flange 7.

[0003] Double-row outer ring raceways 8 and 8 are provided on the inner peripheral surface of the outer ring-equivalent member 1, and inner ring raceways 9 and 9 are provided on an outer peripheral surface of an intermediate portion of the hub 4 and an outer peripheral surface of the inner ring 5. Is formed. Rollers 10 are provided between the outer raceways 8 and the inner raceways 9 so that the inner race member 3 can rotate freely inside the outer race member 1. Further, retainers 11 and 11 are provided to hold the rolling elements 10 and 10 in a freely rolling manner. Although balls are used as the rolling elements 10 and 10 in the illustrated example, tapered rollers may be used as the rolling elements in the case of a heavy hub unit for a vehicle. Further, seal devices 12a and 12b are provided between the outer end portion of the outer ring equivalent member 1 and the outer peripheral surface of the intermediate portion of the hub 4, and the inner peripheral surface of the outer ring equivalent member 1 and the inner ring equivalent member 3 are provided. The outer end opening of the space 13 where the rolling elements 10 and 10 are installed is closed between the outer peripheral surfaces of the rolling elements 10 and 10.

[0004] The sealing device 12a includes a cored bar 105, a slinger 106, and an elastic member 107, as shown in an enlarged manner in FIG. Of these, the core 105
It is integrally formed by subjecting a metal plate such as a low carbon steel plate to a punching process such as a press process and a plastic process. Such a cored bar 105 has an outer diameter side cylindrical portion 10 which can be fitted and fixed to the inner peripheral surface of the end portion of the outer ring equivalent member 1 constituting the rolling bearing O.
9 and an inner annular portion 1 bent radially inward from the axially inner edge (left edge in FIG. 2) of the outer diameter side cylindrical portion 109.
10 and is formed in an annular shape with a substantially L-shaped cross section. Further, the slinger 106 is made of a stainless steel plate or the like.
A metal plate having excellent corrosion resistance is also integrally formed by performing a punching process such as a press process and a plastic process. Such a slinger 106 includes an inner cylindrical portion 112 that can be fitted and fixed to the outer peripheral surface of the outer end of the inner ring 5 that constitutes the rolling bearing O, and an outer peripheral edge of the inner cylindrical portion 112 in the axial direction (see FIG. 2). (The right end edge of the outer ring portion) is formed in an annular shape with an L-shaped cross section, the outer ring portion 113 being bent outward in the diameter direction.

The elastic member 107 is made of an elastic material such as rubber or elastomer, and has three outer, middle and inner seal lips 114, 115 and 116.
The base end is fixedly connected to the core metal 105. Then, the leading edge of the outermost seal lip 114 located on the outermost side is connected to the outer annular portion 113 constituting the slinger 106.
And the leading edges of the remaining two seal lips, the intermediate seal lip 115 and the inner seal lip 116, are brought into contact with the inner cylindrical portion 1 of the slinger 106.
Sliding contact with the outer peripheral surface of the seal 12 prevents leakage of the sealed grease and also prevents intrusion of dust, water, muddy water, and the like from the outside into the bearing.

[0006] As shown in an enlarged manner in FIG. 3, a sealing device 12b is provided with a metal core 216 formed in a ring shape.
And an elastic member 217. Core 2 of these
Reference numeral 16 is made of a metal plate, and is internally fitted and fixed to the outer end of the outer ring equivalent member 1. Also, the elastic member 217
Is made of an elastic material such as rubber, elastomer, or the like, and is molded and bonded to the core metal 216 by bonding or the like.
The elastic member 217 includes an outer diameter side, an inner diameter side, two side seal lips 218 and 219, and one radial seal lip 220. By inclining the two side seal lips 218 and 219 in the direction toward the diametrically outward direction (upward in FIG. 3) toward the leading edge (the left edge in FIG. 3), the inside of the space 13 is The function to prevent foreign matter from entering is secured. In addition, the radial seal lip 220 is inclined in a direction toward the inside of the space 13 (the right side in FIG. 3) toward the leading edge (the lower right edge in FIG. 3), thereby ensuring the function of preventing grease leakage. ing.

More specifically, the sealing device 12b
Is composed of a metal core 216 and an elastic member 217 each formed in a ring shape. The core metal 216 of the sealing device 12b is integrally formed by performing a punching process such as a press process and a plastic process on a metal plate such as a low carbon steel plate. The core metal 216 includes an outer cylindrical portion 222 that can be fitted and fixed to the inner peripheral surface of the end portion of the outer ring-equivalent member 1 constituting the rolling bearing O, and an outer edge of the outer cylindrical portion 222 (see FIG. 3).
Support plate 2 bent radially inward from the left edge of the
23. Of these, the outer diameter side cylindrical portion 222 has a large diameter portion 224 near the inner end (rightward in FIG. 3) and the elastic member 21.
7 covers the entire outer side surface (the left side surface in FIG. 3) of the support plate portion 223 constituting the cored bar 216, and makes the outer peripheral edge of the elastic member 217 a sloped portion that is continuous from the fitting tubular portion 222. 227 and the inner peripheral surface of the open end of the outer ring equivalent member 1. With this configuration, the fitting portion between the core metal 216 and the outer ring equivalent member 1 is sealed. The outer diameter of the large diameter portion 224 in the free state is set slightly larger than the inner diameter of the outer end opening of the outer ring equivalent member 1, and the large diameter portion 224 is formed of the outer ring equivalent member 1. The inner end can be freely fixed to the outer end opening by interference fit. Further, the support plate portion 223 has a substantially S-shaped cross-sectional shape, and approaches the rolling elements 10 and 10 installed in the space 13 as it goes inward in the diametrical direction (downward in FIG. 3) (see FIG. 3). (To the right).

On the other hand, the elastic member 217 constituting the sealing device 12b together with the core metal 216 is made of an elastic material such as rubber, elastomer, or the like, and is insert-molded to the core metal 216 and is fixed by bonding or the like. I have. The outer peripheral edge of such an elastic member 217 covers the outer peripheral surface of the inclined portion 227. The outer diameter of the portion of the elastic member 217 covering the outer peripheral surface of the inclined portion 227 in a free state is set to be slightly larger than the inner diameter of the outer end opening of the outer ring equivalent member 1. In a state where the large diameter portion 224 is internally fitted and fixed to the outer end opening, a portion of the elastic member 217 covering the outer peripheral surface of the inclined portion 227 is the outer peripheral surface of the inclined portion 227. And the inner peripheral surface of the outer end opening portion is elastically pressed to ensure the sealing performance of the portion.

Further, the base 226 of the elastic member 217
The outer side surface (the left side surface in FIG. 3) of the support plate portion 223 is
It is completely covered all around. On the outer surface and the inner peripheral edge of the base 226, two outer seal lips 218 and 219 and one radial seal lip 220 are formed. By inclining the seal lips 218 and 219 in the direction toward the diametrically outward direction (upward in FIG. 3) toward the leading edge (left edge in FIG. 3), the function of preventing foreign matter from entering the space 13 is ensured. ing. The radial seal lip 220
Is inclined in the direction toward the inside of the space 13 (to the right in FIG. 3) toward the leading edge (lower right edge in FIG. 3), thereby ensuring the function of preventing grease leakage.

Conventionally, in a sealing device used in the above-mentioned rolling bearing for a wheel, a rubber material composition in which a general nitrile rubber is appropriately compounded with an additive has been used as an elastic member. As is well known, rolling bearings for automobile wheels are used outdoors, sometimes exposed to a large amount of dust, and are further exposed to rainwater or washing water, or in the worst case, immersed in muddy water. . A sealing device using a general nitrile rubber material composition for an elastic member has a sufficient sealing performance even under grease lubrication in a so-called clean environment where relatively little water is applied and there is little dust.
However, in recent years, there has been a demand for a longer life of wheel bearings and a lower torque of wheel bearings for improving the fuel efficiency of automobiles. However, softening and emulsification occur, and grease runs out, and lubrication cannot be maintained sufficiently. In addition, when the lip is abnormally worn and the sealing property of the sealing device is deteriorated, dust and water easily enter the inside of the bearing, and it may be difficult to maintain the bearing performance for a long time. It is also conceivable to increase the interference in order to improve the sealing performance of the sealing device, but in that case, the torque increases,
There is a high possibility that the lip will be worn and the sealing performance will be reduced, and further, the grease will be degraded due to frictional heat generation and the bearing life may be shortened.

[0011]

As described above, a conventional rolling bearing for a wheel provided with a sealing device using a nitrile rubber composition for an elastic member is not sufficient under severe operating conditions as described above. It cannot be said that the bearing life has been obtained. Therefore, an object of the present invention is to provide a long-life rolling bearing that is provided with a sealing device having a good sealing property even in such a bad environment and is particularly suitable for wheels.

[0012]

In order to achieve the above object, the present invention provides an outer ring having an outer raceway on an inner peripheral surface, an inner race having an inner raceway on an outer peripheral surface, the outer raceway and the inner raceway. A plurality of rolling elements rotatably provided between the outer ring and a sealing device for closing an axial opening of a space in which the rolling elements are provided between an inner peripheral surface of the outer ring and an outer peripheral surface of the inner ring. In a rolling bearing comprising: a rolling bearing, wherein the elastic member constituting the sealing device is formed of a vulcanizable rubber composition obtained by blending at least carbon black with carboxylated acrylonitrile butadiene rubber. provide.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

In the present invention, the configuration of the rolling bearing itself is not particularly limited, and a rolling bearing for a vehicle as shown in FIGS. 1 to 3 can be exemplified. Further, the configuration of the sealing device itself is not limited, and the sealing device as shown in FIGS. 1 to 3 can be exemplified. The elastic member is formed of a rubber composition shown below.

That is, in the rolling bearing of the present invention,
The elastic member constituting the sealing device is formed from a vulcanizable rubber composition in which carboxylated acrylonitrile-butadiene rubber is mixed with carbon black at least as a reinforcing filler.

Since the carboxylated acrylonitrile-butadiene rubber has a carboxyl group in the molecule, a crosslinking reaction proceeds even at the carboxyl group due to the presence of a metal oxide such as zinc oxide which is a vulcanization accelerator which is simultaneously compounded. Has a higher tensile strength than ordinary nitrile rubber. Therefore, by using a rubber composition using this carboxylated acrylonitrile butadiene rubber as a raw rubber, a sealing device having excellent wear resistance can be obtained.

The carboxylated acrylonitrile-butadiene rubber is a carboxyl group-containing monomer in addition to acrylonitrile and butadiene, which are ordinary monomers used in the polymerization of acrylonitrile-butadiene rubber during the production of emulsion polymerization and the like. It is synthesized by further adding an ethylenically unsaturated carboxylic acid such as acrylic acid or methacrylic acid or an anhydride thereof. Further, it can be produced by kneading an acrylonitrile butadiene rubber and an ethylenically unsaturated carboxylic acid such as maleic anhydride or an anhydride thereof in a batch-type heat-sealing kneader such as a pressure kneader, a Banbury mixer, and a Brabender. it can.

The amount of carboxyl groups in the carboxylated acrylonitrile-butadiene rubber is not particularly limited, but its acid equivalent is 1 × 10 ⁻⁴ ephr or more, preferably 2 × 10 ⁻³ ephr.
ephr to about 5 × 10 ^-2 ephr. If the acid equivalent is less than 1 × 10 ⁻⁴ ephr, there is no difference between the tensile strength of ordinary acrylonitrile butadiene rubber having a non-carboxylated cross-linking density, and almost no improvement in wear resistance can be expected. The acid equivalent is determined by dissolving the rubber in acetone,
After reprecipitation purification with n-hexane, the reprecipitated purified rubber was redissolved in pyridine, and this rubber solution was titrated with 0.02 N potassium hydroxide in ethanol using thymolphthalein as an indicator. It is a value obtained as an equivalent to 100 g.

Carboxylated acrylonitrile-butadiene rubber, like ordinary acrylonitrile-butadiene rubber, includes low nitrile, medium nitrile, medium high nitrile, high nitrile, and extremely high nitrile, depending on the acrylonitrile content, from the lower side. In consideration of oil resistance, medium nitrile, medium-high nitrile, and high nitrile are preferable, and in that case, the content of acrylonitrile is 20 to 40.
%.

Carboxylated acrylonitrile-butadiene rubber satisfying the above-mentioned preferred acid equivalent and acrylonitrile content is also available on the market. For example, Nipol DN631 (AN: 33.5) and Nipol
1072 (AN: 27).

Carbon black is added to the carboxylated acrylonitrile butadiene rubber as a reinforcing filler. The type of carbon black is not particularly limited, for example, SAF (Super Abrasion Furnace black), I
SAF (Intermediate Super Abrasion Furnace black), HA
F (High Abrasion Furnace black), MAF (Medium Abrasio
n Furnace black), FEF (Fast Extruding Furnace blac
k), GPF (General Purpose Furnace black), SRF (Simi-R
einforcing Furnace black), FT (Fine Thermal Furnace)
black), MT (Medium Thermal Furnace black), etc., more preferably HAF, FEF, GPF, SRF, and
It may be used in combination of more than one kind.

Further, a white filler may be used in combination as a reinforcing filler. As a white filler, hydrous silica,
Examples include clay, talc, calcium carbonate, diatomaceous earth, wollastonite, and the like.

By adding carbon black as a reinforcing filler to the rubber composition, the abrasion resistance of the lip of the sealing device is improved, and as a result, the sealing property is improved. The amount of carbon black added is not particularly limited, but is preferably 15 to 80 parts by weight based on 100 parts by weight of the carboxylated acrylonitrile butadiene rubber. If the amount is less than 15 parts by weight, sufficient reinforcing properties are not exhibited and the wear resistance is not satisfied. Conversely, if it is added in an amount exceeding 80 parts by weight, not only is no further improvement in the reinforcing properties and wear resistance recognized, but also the molding processability is extremely reduced and the production becomes difficult. The hardness is too high and the elongation is low,
The inherent rubber elasticity decreases.

When carbon black and a white filler are used in combination, carbon black is added in an amount of 10 to 70%.
It is preferable that the weight of the white filler be 10 to 120 parts by weight, and the total amount be 20 to 200 parts by weight. If the total added amount is less than 20 parts by weight, sufficient reinforcing properties are not exhibited, and even if the added amount exceeds 200 parts by weight, not only further improvement in reinforcing properties and abrasion resistance is not recognized but also , The moldability becomes extremely low and the production becomes difficult.
The hardness is too high, the elongation is low, and the inherent rubber elasticity is low.

In addition, the above-mentioned rubber composition contains a conventionally known vulcanizing agent, vulcanization accelerator, vulcanization accelerating aid, antioxidant, reinforcing agent, plasticizer, coupling agent, pigment, dye, Mold,
A compounding agent such as a processing aid and a conductivity-imparting agent, and a wear improver and a friction improver can be appropriately added and compounded as required.

For example, examples of the wear improver include polyolefin and spherical carbon fine particles. Examples of the polyolefin include polyethylene, polypropylene, polybutene-1, and poly-4-methylpentene-1. Among them, high-density polyethylene is preferable because it contributes to improvement of friction characteristics. Furthermore, in order to improve the adhesion between the high-density polyethylene and the carboxylated acrylonitrile-butadiene rubber and the dispersibility in the carboxylated acrylonitrile-butadiene rubber, the high-density polyethylene may be modified with an unsaturated carboxylic acid or an anhydride thereof. . Polyethylene, when modified with an unsaturated carboxylic acid or its anhydride, is likely to be adsorbed to various rubbers, oxides, and the like by a carboxyl group in the structure. Further, the carboxyl group present in the carboxylated acrylonitrile-butadiene rubber has the same effect, and therefore, the mechanical properties such as tensile strength and abrasion resistance are further improved by the synergistic effect, which is preferable. Examples of unsaturated carboxylic acids or anhydrides thereof include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, citrate, oleic acid, and unsaturated dicarboxylic acids such as maleic anhydride, itaconic anhydride and citraconic anhydride. Although one or more of these can be used, maleic anhydride is particularly preferred.

The addition amount of the polyolefin is preferably 5 to 60 parts by weight based on 100 parts by weight of the carboxylated acrylonitrile butadiene rubber in view of the balance between the wear resistance of the rubber material composition and other physical properties. If the amount is less than 5 parts by weight, the effect of improving the wear resistance is low. Conversely 60
Even if compounded in excess of parts by weight, not only is the reinforcing property of the rubber material composition and further improvement in abrasion resistance not recognized, but also the molding processability is extremely reduced and the production becomes difficult, and further, The hardness is too high, the elongation is low, and the inherent rubber elasticity is low.

The spherical carbon fine particles are glassy carbon and spherical graphite, which are obtained by carbonizing and firing a phenol / formaldehyde resin in nitrogen at a temperature of 800 to 2000 ° C. 〜40 μm. Such spherical carbon fine particles can be obtained from the market, and examples thereof include Bellpearl C (registered trademark) manufactured by Kanebo and (registered trademark) Univex manufactured by Unitika. Since the spherical carbon fine particles are present on the surface of the rubber composition and receive a load, the wear resistance of the rubber composition is greatly improved. The mixing ratio of the spherical carbon fine particles is not particularly limited, but is preferably 5 to 40 parts by weight based on 100 parts by weight of the carboxylated acrylonitrile butadiene rubber.

As friction modifiers for improving lubricity,
Waxes having a melting point of 40 to 140 ° C. (low melting point fats and oils) are exemplified. Specifically, petroleum wax represented by paraffin wax and microcrystalline wax in the above melting point range, polyethylene wax, montan wax, carnauba wax, ester wax, stearoamide, oxystearoamide, erucylamide, laurylamide, Examples include palmitylamide, behenamide, methylolamide, ethylenebisoleylamide, stearyloleylamide and the like, and among them, polyethylene wax is most preferred. By adding 3 to 30 parts by weight of such waxes to 100 parts by weight of carboxylated acrylonitrile butadiene rubber, the friction characteristics are improved. When the amount is less than 3 parts by weight, sufficient lubricity cannot be obtained. On the contrary, when the amount exceeds 30 parts by weight, sufficient tensile strength and elongation cannot be obtained, and not only rubber elasticity decreases, but also a core constituting a sealing device. Adhesion between gold and the elastic member is extremely reduced.

Liquid substances (lubricating oils) as friction modifiers
Can also be used, for example, mineral oil, ether-based oil, silicone-based oil, poly-α-olefin oil, fluorine oil, fluorine-based surfactant and the like. Among them, silicone-based oils are more preferable. Silicone oil is a liquid substance at room temperature containing polydimethylsiloxane as a main component.In order to enhance compatibility with carboxylated acrylonitrile butadiene rubber, a part of the methyl group or the molecular terminal of the polydimethylsiloxane is an amino group or an alkyl group. It is preferable to use a modified type substituted with a group, an epoxy group, a polyether group, a higher fatty acid ester, or the like. By modifying with such a functional group, the functional group reacts or adsorbs on the main chain of the carboxylated acrylonitrile-butadiene rubber, preventing the oil from blooming on the surface of the rubber composition at once, and gradually making the oil permanent. To bloom.

Since these lubricating oils are liquid, they tend to bloom on the surface of the rubber composition, and the effect is exhibited even when a small amount is added. Specifically, lubricating oil is added in an amount of 1 to 100 parts by weight of carboxylated acrylonitrile butadiene rubber.
Addition of 30 parts by weight improves the lubricity of the rubber composition. When the amount is less than 1 part by weight, sufficient lubricity is not exhibited, and when the amount exceeds 30 parts by weight, not only poor dispersion of the additive occurs during processing of the rubber composition, but also the core metal and the elastic member constituting the sealing device do not have sufficient lubricity. Adhesion is extremely reduced.

The viscosity of the lubricating oil is not particularly limited, and any commercially available one can be used.
The viscosity in the range of ² to 10000 mm ² / s is preferred because it is easily compounded in the rubber composition.

If there is no mechanism for supplying electricity between the axle and the wheel bearing, static electricity generated while the vehicle is running remains on the vehicle, and radio noise or the like is generated when the vehicle starts running. May occur. In order to cope with this, it has been considered to make the elastic member of the sealing device of the rolling bearing for wheels conductive, thereby energizing the bearing and the axle.

[0034] When electrification of the elastic member guide, but are not limited to the resistance value is particularly preferably less 10 ⁵ Ω · cm in volume resistivity, can be sufficiently suppressed radio noise if it less is there. The method for making the elastic member conductive is not particularly limited, but a conductive powder or conductive fiber can be added to the rubber composition. For example, as the conductive powder, brass, aluminum alloy, copper, silver, nickel, steel, and metal powder such as stainless steel, graphite,
Powdered conductive materials such as conductive carbon black, conductive tin oxide with tin oxide doped with antimony, conductive zinc oxide with zinc oxide doped with aluminum, and conductive indium oxide with tin doped in indium oxide And a coating of an insulating material such as mica with a conductive coating. Examples of the conductive fiber include carbon fiber, metal fiber (a fiber made of brass, aluminum alloy, copper, silver, nickel, steel, stainless steel, etc.), and a non-conductive fiber provided with a conductive coating. Can be used.

Above all, conductive carbon black having a highly developed graphite structure is preferable since it has little effect on mechanical properties and workability. Among conductive carbon blacks, acetylene black and Ketjen black are more preferable, since excellent conductivity can be obtained with a small amount. The amount of acetylene black and Ketjen black to be added is not particularly limited, but is preferably 2 to 40 parts by weight based on 100 parts by weight of carboxylated acrylonitrile butadiene rubber. If the amount is less than 2 parts by weight, sufficient conductivity (volume specific resistance value of 10 ⁵ Ω · cm or less) is not exhibited, and radio noise is not satisfied. Conversely, if it is added in an amount exceeding 40 parts by weight, not only does the workability extremely decrease and the production becomes difficult, but also the hardness becomes too high, the elongation becomes low, and the inherent rubber elasticity decreases. I will. Further, it is preferable to use acetylene black or Ketjen black in combination with a so-called conductive whisker in which fine whiskers are provided with a conductive coating, since the conductivity is extremely improved.

The rubber composition contains a vulcanizing additive. The vulcanization-based additive includes a vulcanizing agent (crosslinking agent), a vulcanization accelerator, and a vulcanization accelerator.

The vulcanizing agent (crosslinking agent) is not particularly limited.
Various kinds of sulfur such as powdered sulfur, sulfur, precipitated sulfur and highly dispersible sulfur, morpholine disulfide, alkylphenol disulfide, N, N-dithio-bis (hexahydro-2H
-Azepinone-2), a sulfur compound capable of discharging sulfur such as thiuram polysulfide, dicumyl peroxide, di (t-butylperoxy) diisopropylbenzene,
Peroxides such as 2,5-dimethylhexane and benzoyl peroxide are mentioned. Among these, it is preferable to use highly dispersible sulfur or morpholine disulfide in view of dispersibility, ease of handling and heat resistance.

When a sulfur-based vulcanizing agent is used, guanidine-based, aldehyde-ammonia-based, thiazole-based, sulfenamide-based, thiourea-based, thiuram-based, dithiocarbamate-based, and xanthate-based vulcanizing agents are used. Must be used as an accelerator. Among them, when a small amount of highly dispersible sulfur is blended, thiuram-based tetramethylthiuram disulfide or the like, sulfenamide-based N-cyclobenzyl-2-benzothiazyl-sulfenamide, and thiazole-based 2-mercaptobenzo It is preferable to use thiazole and the like in combination.

Examples of the vulcanization accelerator include metal oxides such as zinc oxide, metal carbonates, metal hydroxides, fatty acids such as stearic acid and derivatives thereof, and amines.
Carboxylated acrylonitrile butadiene rubber is apt to undergo premature vulcanization due to zinc oxide, and therefore a combination of zinc peroxide and stearic acid is preferred. Zinc peroxide is present in the rubber composition as it is at the temperature at the time of kneading of the rubber composition and generates zinc oxide at the time of vulcanization molding, so that early vulcanization does not occur at the time of kneading and storage. .

The antioxidants for preventing oxidative deterioration include:
Amine-ketone condensation products, aromatic secondary amines, monophenol derivatives, bis or polyphenol derivatives,
Hydroquinone derivatives, sulfur-based anti-aging agents, phosphorus-based anti-aging agents and the like can be mentioned. Among these, amine-ketone condensation product system 2,2,4-trimethyl-1,2-dihydroquinoline polymer / condensation reaction product of diphenylamine with acetone, aromatic secondary amine system N, N'- Di-β-naphthyl-p-phenylenediamine, 4,4′-bis-
(Α, α-dimethylbenzyl) diphenylamine, N-
Phenyl-N '-(3-methacryloyloxy-2-hydroxypropyl) -p-phenylenediamine and the like are preferred.

Further, in order to prevent thermal decomposition and improve heat resistance, it is more preferable to use a secondary antioxidant together with the above antioxidant. Examples of the secondary aging inhibitor include sulfur-based 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, and zinc salts thereof. Further, as a sun crack preventing agent for suppressing cracks due to the action of sunlight or ozone, the melting point is 55-7.
About 0.5 to 2 parts by weight of waxes at about 0 ° C. may be added to 100 parts by weight of carboxylated acrylonitrile butadiene rubber.

When it is necessary to further improve the molding processability, a plasticizer is appropriately added as a processing aid in addition to the above additives. However, when there is no particular problem in molding, it is not necessary to particularly add. When added, the amount is 3 to 20 parts by weight based on 100 parts by weight of the carboxylated acrylonitrile butadiene rubber. When added more than necessary, the rubber composition softens and simultaneously bleeds out without being completely mixed. The adhesion between the metal core and the elastic member is extremely reduced. Specific examples of the plasticizer include phthalic acid diesters such as dioctyl phthalate, polyester plasticizers, polyether plasticizers, polyetherester plasticizers, and liquid nitrile rubber.

In terms of physical properties, the hardness of the rubber composition is affected by the amount of a reinforcing filler, an abrasion modifier, etc., but the sealing property when applied to a sealing device for a rolling bearing for wheels is improved. From the followability, the range of 50 to 90 is preferable in the spring hardness A scale described in JIS K6301. If the hardness is less than 50, the frictional resistance of the sealing device increases and the wear resistance decreases. Further, when the hardness exceeds 90, the rubber elasticity is reduced as described above, so that the sealing property and followability of the lip portion of the sealing device are reduced, and the sealing device is used in an environment where there is a lot of dust or where the lip is exposed to muddy water. Then, the life of the rolling bearing for wheels may be shortened.

The method for obtaining the rubber composition using each of the above components is not particularly limited, but a carboxylated acrylonitrile-butadiene rubber and carbon black, and other fillers and additives are mixed with a rubber kneading roll, a pressure kneader, It is possible to uniformly knead using a conventionally known rubber kneading device such as a Banbury mixer. The kneading conditions are not particularly limited, but usually at a temperature of 30 to 80 ° C. However, when a polyolefin is added to the wear improver, the kneading is performed at a temperature higher than its melting point for 5 to 60 minutes so that the various additives can be sufficiently mixed. Variance can be measured.

The method for using the rubber composition as an elastic member of a sealing device is not particularly limited, but it is sufficient to heat the unvulcanized rubber composition while pressing it in a mold.
It can be manufactured by a known rubber molding method such as compression molding, transfer molding, and injection molding. For example, in the case of compression molding, a core metal (forming a core part of a sealing device) coated with an adhesive in advance is inserted into a mold, and a sheet of the unvulcanized rubber composition manufactured by the method described above is inserted. Put, usually 120 ~
It can be produced by pressure vulcanization at 250 ° C. for about 3 minutes to 2 hours.

[0046]

The present invention will be further described below with reference to examples. However, the present invention is not limited at all by the examples.

[Examples 1 to 10 and Comparative Examples 1 to 7] (Rubber composition) As shown in Table 1, a rubber composition was prepared by blending a raw rubber, a reinforcing filler and various additives.

[0048]

[Table 1]

The various raw rubbers and additives (listed in Table 1) used are collectively shown below. 1) Raw material rubber A: Middle and high nitrile rubber (JS manufactured by JSR)
RNBR N230S), acrylonitrile monomer ratio: 35% 2) Raw rubber B: carboxylated medium-high nitrile rubber (Nipol DN631 manufactured by Zeon Corporation), acrylonitrile monomer ratio: 33.5% 3) Raw rubber C : Carboxylated middle nitrile rubber (Nipol 1072J, manufactured by Zeon Corporation), acrylonitrile monomer ratio: 27% 4) Carbon black A: HAF grade carbon black (Diablack H, manufactured by Mitsubishi Chemical Corporation) 5) Carbon black B: FEF grade carbon black (Asahi Carbon Co., Ltd., Asahi 60) 6) Silica: hydrous silica (Nippon Silica Co., Ltd., Nip Seal AQ) 7) Clay: Kaolin clay (Shiraishi Calcium Co., S)
T-301) 8) Wollastonite: (NYCO, NYAD40)
0) 9) Vulcanizing agent: highly dispersible sulfur (Sulfax, manufactured by Tsurumi Chemical Industry Co., Ltd.)
PMC) 10) Vulcanization accelerator A: Tetramethyl thiuram disulfide (Ouchi Shinko Chemical Co., Ltd., Noxeller TT) 11) Vulcanization accelerator B: Tetraethyl thiuram disulfide (Ouchi Shinko Chemical Co., Ltd., Noxeller TET) 12 ) Vulcanization accelerator C: N-cyclohexyl-2-benzothiazyl sulfenamide (Nouchira CZ, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) 13) Vulcanization accelerator A: Stearic acid (Kao Corporation, Lunac)
S-35) 14) Vulcanization accelerating aid B: Zinc oxide (Sakai Chemical Co., French method No. 1) 15) Vulcanization accelerating aid C: Zinc peroxide masterbatch (Zeonet ZP, manufactured by Zeon Corporation) 16 ) Activator: diethylene glycol (manufactured by Nippon Shokubai Co., Ltd.) 17) Plasticizer: di- (2-ethylhexyl) phthalate (manufactured by Daihachi Chemical Co., DOP) 18) Wear modifier: carboxyl-modified polyethylene (manufactured by Mitsubishi Chemical Corporation, Moddick) AP H511) 19) Antioxidant A: 4,4-bis- (α, α-dimethylbenzyl) diphenylamine (manufactured by Ouchi Shinko Chemical Co., Ltd.
Nocrack CD) 20) Antioxidant B: 2-mercaptobenzimidazole (Ouchi Shinko Chemical Co., Ltd., Nocrack MB) 21) Antioxidant C: special wax (Ouchi Shinko Chemical Co., Sunnock) 22) Lubrication Oil: Silicone oil (Shin-Etsu Silicone Co., Ltd.
KF-860) 23) Coupling agent: γ-mercaptopropyltrimethoxysilane (KBM803, manufactured by Shin-Etsu Silicone Co., Ltd.)

(Preparation of Test Sample) Using each of the above-mentioned materials, a test sample was prepared by the following steps. Kneader kneading process Raw rubber and various additives other than the vulcanizing agent and the vulcanization accelerator were charged into a pressure kneader and kneaded at a set temperature of 80 ° C. However, when carboxyl-modified polyethylene was added as a wear improver, the set temperature was 130 ° C. Roll kneading process A vulcanizing agent and a vulcanization accelerator are added to a material kneaded by a kneader, and the mixture is kneaded at a set temperature of 50 ° C. using a 6-inch roll to form a sheet having a thickness of 2.2 mm. . The rotation speed of each roll was 20 rpm and 32 rpm. Vulcanization Molding Step (1) Production of Sealing Device A core made of a cold-rolled steel plate that has been washed, coated with an adhesive, and baked in advance is inserted into a desired sealing device mold. And
An unvulcanized rubber sheet similar to the one used in the above step was placed and heated and pressed at 170 ° C. for 10 minutes to obtain a sealing device (inner diameter 60 mm) shown in FIG. (2) Sheet Forming A 2 mm-thick sheet vulcanizing mold was mounted on a vulcanizing press heated to 170 ° C., and the unvulcanized rubber sheet was placed thereon. Then, heating and pressurizing for 15 minutes, vertical 150mm,
A vulcanized rubber sheet having a width of 150 mm and a thickness of 2 mm was obtained.

(Test for confirming sealing performance) In the test, the sealing device 12a manufactured in the above (1) was incorporated into the shaft 101 of the seal rotation tester 100 shown in FIG. Mud was continuously flowed in through 102. The test conditions are as follows.・ Rotation speed: 1000 rpm ・ Test time: 72 hrs ・ Shaft eccentricity: 0.5 mm TIR ・ Muddy water composition: JIS Class 8 dust 10% ・ Grease: lithium soap, mineral oil ・ Grease application amount: between the outer seal lip and the intermediate seal lip 1.0 g, 0.4 g between the intermediate seal lip and the inner seal lip ・ Injection condition: 2 liters per minute of muddy water is injected from above the sealing device as shown in FIG. 4 ・ Criteria: middle between the outer seal lip and the middle The amount of water in the grease applied between the seal lip and the grease was measured by the Karl Fischer method, and the case where the water amount was 0.5% or less was evaluated as excellent and the case where the water amount was 1% or less. Is indicated as 良好 as good, the case where the moisture content is 2 to 5% is slightly poor as △, and the case where the moisture content is 5% or more is poor as x, and the results are shown in Table 2.

(Measurement of Physical Properties) The physical properties of the sheet prepared in the above (2) were measured. The test conditions were as follows, and the results are shown in Table 2. Hardness test sheet was punched out in the shape of a JIS No. 3 test piece, and three sheets were laminated, and the hardness (spring hardness) was determined based on JIS K6301. A scale) was measured. Tensile test JIS No. 3 test piece was tested by a universal testing machine using JIS.
A tensile test was performed based on SK6301, and tensile strength at break and elongation were measured.

[0053]

[Table 2]

As is evident from the results in Table 2, none of the examples using a rubber composition containing at least carbon black in a carboxylated acrylonitrile butadiene rubber, which is within the scope of the present invention, is an uncarboxylated general rubber. The sealability is superior to the comparative example using nitrile rubber and the comparative example using a reinforcing filler other than carbon black. Further, the results of Examples 7 to 9 show that it is more effective to use a polyolefin as a wear improver and to use a silicone oil as a lubricating oil.

Examples 11 to 22 and Comparative Examples 8 to 12 (Rubber compositions) As shown in Table 3, raw rubber, reinforcing fillers, various additives and conductivity imparting agents (conductive carbon black, conductive carbon black, Whisker) was blended to prepare a rubber composition.

[0056]

[Table 3]

The raw rubber, reinforcing filler and various additives used were the same as those used for preparing the rubber compositions of Examples 1 to 10 and Comparative Examples 1 to 7. The conductivity imparting agents used are as follows. 24) Conductive carbon black A: (Ketjen Black EC, Ketjen Black EC)
-600 JD) 25) Conductive carbon black B: acetylene black (Denka black, manufactured by Denki Kagaku Kogyo Co., Ltd.) 26) Conductive whisker: Conductive potassium titanate whisker (Dentol BK, manufactured by Otsuka Chemical Co., Ltd.)

(Preparation of Test Sample) Examples 1 to 10
In the same manner as in Comparative Examples 1 to 7, a test seal device and a sheet were produced.

(Test for Confirming Sealing Property and Measurement of Physical Properties) Example 1
In the same manner as in Comparative Examples 1 to 7 and Comparative Examples 1 to 7, a sealability confirmation test and measurement of physical properties in a normal state were performed. Table 4 shows the results.

(Conductivity Test) Regarding the prepared sheet,
The volume resistivity was measured based on SRIS 2301. In addition, a volume specific resistance value of 10 ⁵ Ω · cm or less is acceptable. Table 4 shows the measurement results.

[0061]

[Table 4]

As is evident from the results in Table 4, the sealability and the physical properties were obtained by adding a conductivity-imparting agent within the scope of the present invention to the basic composition obtained by mixing carbon black with carboxylated acrylonitrile-butadiene rubber. It can be seen that good conductivity can be imparted while maintaining the above.

[0063]

As described above, the rolling bearing according to the present invention provides a vulcanizable rubber obtained by mixing a carboxylated acrylonitrile-butadiene rubber with at least carbon black as a filler as an elastic member constituting a sealing device. Since it is formed of the composition, even when used in an environment exposed to muddy water, the sealing device has excellent sealing properties and can maintain desired performance for a long period of time. Further, by further adding a conductivity-imparting agent to the rubber composition, good conductivity can be imparted to the elastic member while maintaining sealing performance, and when a rolling bearing for vehicles is used, generation of radio noise is suppressed. can do.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a rolling bearing of the present invention.

FIG. 2 is an enlarged view of one sealing device (12a) of the rolling bearing shown in FIG.

FIG. 3 is an enlarged view of the other sealing device (12b) of the rolling bearing shown in FIG.

FIG. 4 is a schematic cross-sectional view illustrating a seal rotation tester used for a sealability confirmation test.

[Explanation of symbols]

 O Rolling bearing 1 Outer ring equivalent member 4 Inner ring equivalent member 8 Outer ring raceway 9 Inner ring raceway 10 Rolling element 11 Cage 12a Sealing device 12b Sealing device 100 Seal rotation tester

Continuing on the front page (72) Inventor Shunichi Yabe 1-5-50 Kugenuma Shinmei, Fujisawa-shi, Kanagawa Nippon Seiko Co., Ltd. (72) Inventor Shigeaki Aihara 1-150 Kugenuma Shinmei, Fujisawa-shi, Kanagawa Nippon Seiko F term in the company (reference) 3J016 AA02 AA03 BB03 CA02 4J002 AC101 DA036 DA037 FD010 FD016 FD030 FD060 FD110 FD117 FD140 FD150 FD170 FD200 GM05

Claims (4)

[Claims] 1. An outer ring having an outer raceway on an inner peripheral surface, an inner racer having an inner raceway on an outer peripheral surface, and a plurality of rolling elements rotatably provided between the outer raceway and the inner raceway. ,
In a rolling bearing including a seal device that closes an axial opening of a space in which the rolling element is provided between an inner peripheral surface of the outer ring and an outer peripheral surface of the inner ring, an elastic member forming the seal device, A rolling bearing formed of a vulcanizable rubber composition obtained by compounding at least carbon black with a carboxylated acrylonitrile butadiene rubber. 2. The rolling bearing according to claim 1, wherein the compounding amount of carbon black in the rubber composition is 15 to 80 parts by weight based on 100 parts by weight of the carboxylated acrylonitrile butadiene rubber. 3. The rolling bearing according to claim 1, wherein the rubber composition has an electric resistance of 10 ⁵ Ω · cm or less in volume resistivity. 4. The rubber composition according to claim 1, further comprising 2 to 40 parts by weight of conductive carbon black per 100 parts by weight of carboxylated acrylonitrile butadiene rubber. 2. The rolling bearing according to claim 1.