JP2006016441A - Grease composition and rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease composition having excellent water resistance and peel resistance and provide a rolling bearing having excellent water resistance and peel resistance and especially suitable for vehicle use. <P>SOLUTION: The grease composition contains a base oil composed of a mineral oil or a synthetic oil having a kinematic viscosity of 70-250 mm<SP>2</SP>/s at 40°C and containing at least one kind of carboxylic acid-based antirust agent, carboxylic acid salt-based antirust agent and ester-based antirust agent in an amount of 0.1-20 mass%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rolling bearing suitable for supporting an axle of an automobile or a railway vehicle, and a grease composition suitable for the rolling bearing.

  As a bearing for a vehicle such as an automobile or a railway vehicle, for example, a so-called “unit bearing” with a seal as shown in FIG. 1 is frequently used. In the unit bearing shown in the drawing, an outward flange 3 for fixing a wheel (not shown) is provided on the outer peripheral surface (left end portion in the drawing) of the hub 2 constituting the inner ring equivalent member together with the inner ring element 1. The inner ring raceway 4a and the stepped portion 5 are formed on the outer peripheral surface of the intermediate portion. Further, on the outer peripheral surface of the hub 2 near the inner end of the intermediate portion (rightward in the drawing), the inner ring element 1 having the inner ring raceway 4b formed on the outer peripheral surface has a stepped portion on the outer end surface (left end surface in the drawing). 5 is supported by external fitting in a state where it abuts against 5.

  Further, a male screw portion 6 is formed at a portion near the inner end of the hub 2. Then, the inner ring element 1 is fixed to a predetermined portion of the outer peripheral surface of the hub 2 by screwing the nut 7 into the male screw portion 6 and further tightening. On the outer peripheral surface of the intermediate portion of the outer ring 8 arranged around the hub 2, an outward flange-like attachment portion 9 is provided for fixing the outer ring 8 to a suspension device (not shown). Further, outer ring raceways 10a and 10b are formed on the inner peripheral surface of the outer ring 8 so as to face the inner ring raceways 4a and 4b, respectively. A plurality of rolling elements 11, 11 are provided between the inner ring raceways 4 a, 4 b and the pair of outer ring raceways 10 a, 10 b, respectively, so that the hub 2 can freely rotate inside the outer ring 8. Each of the rolling elements 11 and 11 is held by the cages 12 and 12 so as to roll freely for each row.

  A seal ring 13 made of an elastic material typified by a nitrile rubber composition is attached between the inner peripheral surface of the outer end of the outer ring 8 (left end in the figure) and the outer peripheral surface of the hub 2. This seal ring 13 exists between the inner peripheral surface of the outer ring 8 and the outer peripheral surfaces of the hub 2 and the inner ring element 1, and the outer end opening 28 of the space 15 provided with a plurality of rolling elements 11, 11. Is blocking. Furthermore, the inner end (right end in the figure) opening of the outer ring 8 is closed by a cover 14, and foreign matter such as dust and rainwater is prevented from entering the space 15 from the inner end opening. The grease (not shown) filled in is prevented from leaking.

  In a passenger car, a unit bearing of a double row ball bearing as shown in the figure is used. However, in a large automobile, a unit bearing of a double row tapered roller bearing using a tapered roller as the rolling element 11 in FIG. In a vehicle, a unit bearing of a similar double row tapered roller bearing or a unit bearing of a double row cylindrical roller bearing using a cylindrical roller as the rolling element 11 is often used.

  Conventionally, greases that use mineral oil as a base oil and lithium soap as a thickener have been used. However, in a vehicle or the like, water may enter during operation and adhere to the bearing and may be mixed into the grease. As a result, as described in Japanese Patent Application Laid-Open No. 11-72120, hydrogen from the infiltrated moisture causes the same white tissue peeling, and the white tissue peeling is more likely to occur in combination with the hydrogen from the above-described grease. It has become. There is a risk that it will not be possible to handle the operation at a high load that is expected to continue to increase in the future.

  As countermeasures against white tissue peeling, there are many methods using sealed grease. For example, grease containing a passive oxidant such as sodium nitrite (see Patent Document 1), grease containing an organic antimony compound or an organic molybdenum compound (patented) It has been proposed to enclose greases (see Patent Document 3) each containing an inorganic compound having a particle size of 2 μm or less. These prevent the penetration of hydrogen into the bearing material by forming a coating derived from the blend at the rolling contact. However, it is not possible to prevent the ingress of hydrogen until the film is formed, and when the rolling element slips due to vibration or speed fluctuation, the metal film peels off at the rolling contact part and the generated film is destroyed. Hydrogen enters.

  As countermeasures other than encapsulated grease, for example, JP-A-3-173747 proposes a rolling bearing in which the bearing material is stainless steel, and JP-A-4-244624 proposes a rolling bearing in which the rolling element is made of ceramics. is doing. However, these rolling bearings usually increase costs.

  Moreover, in a rolling bearing, if moisture is mixed in the lubricant, the service life is greatly reduced. For example, Furumura et al. Reported that when 6% of water is mixed in lubricating oil (# 180 turbine oil), rolling fatigue life is reduced by a factor of 1 to 20 times compared to the case of no mixing. (Furumura Shinzaburo, Shirota Shinichi, Hirakawa Kiyoshi: NSK Bearing Journal, No. 636, pp. 1-10, 1977). Schattberg et al. Also reported that rolling strength of steel is reduced by 32 to 48% when only 100 ppm of water is mixed in the lubricating oil (P. Schattberg, IM Felsen: Effects of water and oxygen rolling rolling contact, wear, 12, pp.331-342, 1968).

  Therefore, in order to suppress the generation of rust, rust preventive oil is also applied to the inside of the bearing before the grease is sealed. The rust preventive oil is blended with a rust preventive agent in order to enhance the rust preventive effect, and a sulfonic acid metal salt is generally added because of its high rust preventive ability. However, as pointed out in Patent Document 1, the sulfonic acid metal salt promotes the generation of hydrogen and may cause white tissue peeling, and the sulfonic acid metal salt is adsorbed on the metal. Because it is very high in performance and easily forms a sulfonic acid adsorption film on the surface of the bearing member to inhibit the formation of a coating derived from the above compound, it can be applied to rolling bearings used in the above parts. It is not preferable.

Japanese Patent No. 2878749 Japanese Patent Publication No. 6-803565 Japanese Patent Laid-Open No. 9-169989

  This invention is made | formed in view of such a condition, and it aims at providing the grease composition which has the outstanding water resistance and peeling resistance. Another object of the present invention is to provide a rolling bearing that is sealed with the grease composition and has excellent water resistance and peeling resistance, and is particularly suitable for vehicles.

In order to achieve the above object, the present invention provides the following grease composition and rolling bearing.
(1) It consists of a mineral oil or a synthetic oil having a kinematic viscosity at 40 ° C. of 70 to 250 mm ² / s, and at least one of a carboxylic acid-based rust inhibitor, a carboxylate-based rust inhibitor, and an ester-based rust inhibitor is 0.1 A grease composition comprising a base oil contained at a ratio of ˜20 mass%.
(2) The grease composition as described in (1) above, which contains, as a thickener, at least one of metal soap, metal composite soap and urea compound in a proportion of 5 to 35% by mass of the total amount of grease.
(3) A rolling bearing comprising the grease composition as described in (1) or (2) above.
(4) The rolling bearing according to the above (3), comprising a rubber seal.
(5) The rolling bearing according to (3) or (4) above, which is used for supporting an axle.

  Since the grease composition of the present invention uses a base oil containing a specific rust preventive agent, it exhibits excellent water resistance and peel resistance. Therefore, it is suitable for a rolling bearing used in an environment where there is much contact with water, particularly a rolling bearing for supporting an axle of a vehicle, and excellent water resistance and peeling resistance can be imparted to these bearings.

  Hereinafter, the present invention will be described in detail.

The grease composition of the present invention uses mineral oil or synthetic oil having a kinematic viscosity at 40 ° C. of 70 to 250 mm ² / s as the base oil. As the mineral oil, a refined product obtained by appropriately combining mineral oils obtained by distillation under reduced pressure, oil removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, white clay purification, hydrorefining, and the like can be used.

  Further, as the synthetic oil, hydrocarbon oil, aromatic oil, ester oil, ether oil and the like can be used. As the hydrocarbon oil, it is possible to use normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, poly-α-olefin such as 1-decene and ethylene co-oligomer, or hydrides thereof. it can. As the aromatic oil, alkylbenzene such as monoalkylbenzene and dialkylbenzene, alkylnaphthalene such as monoalkylnaphthalene, dialkylnaphthalene and polyalkylnaphthalene can be used. Examples of ester oils include dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, methyl acetyl cinolate, and the like, trioctyl trimellitate, tridecyl Aromatic ester oils such as trimellitate, tetraoctyl pyromellitate, polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, polyvalent A complex ester oil which is an oligoester of alcohol and a mixed fatty acid of dibasic acid / monobasic acid can be used. Examples of ether oils include polyglycols such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, and polypropylene glycol monoether, monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, pentaphenyl ether, tetraphenyl ether, and monoalkyl tetraphenyl. Phenyl ether oils such as ether and dialkyl tetraphenyl ether can be used.

These lubricating oils may be used alone or in appropriate combination, and are adjusted so as to have the above viscosity. Preferably, a base oil containing an ester oil having a kinematic viscosity at 40 ° C. of 120 to 185 mm ² / s in an amount of 50% by mass or more of the total amount of the base oil and having a kinematic viscosity at 40 ° C. of 120 to 185 mm ² / s as a whole is used. Particularly preferably, the base oil is composed only of ester oil having a kinematic viscosity at 40 ° C. of 120 to 185 mm ² / s.

  At least one of a carboxylic acid rust inhibitor, a carboxylate rust inhibitor, and an ester rust inhibitor is added to the base oil. Carboxylic acid-based rust preventives include linear fatty acids such as lauric acid and stearic acid, saturated carboxylic acids having a naphthene nucleus, succinic acid, alkyl succinic acid, alkyl succinic acid half ester, alkenyl succinic acid, and alkenyl succinic acid half ester. And succinic acid derivatives such as succinimide, hydroxy fatty acids, mercapto fatty acids, sarcosine derivatives, and oxidized waxes such as waxes and petrolatum oxides. Examples of the carboxylate-based rust preventive include metal salts such as fatty acid, naphthenic acid, apietic acid, lanolin fatty acid, alkenyl succinic acid, and amino acid derivatives. Examples of the metal element include cobalt, manganese, zinc, aluminum, calcium, barium, lithium, magnesium, copper, and the like. In addition, as ester-based rust inhibitors, partial esters of polyhydric alcohols such as sorbitol, pentaerythritol, sucrose, glycerin and carboxylic acids such as oleic acid, lauric acid, oleyl alcohol, stearyl alcohol, lauryl alcohol, etc. Examples include higher fatty acid alcohols.

  The carboxylic acid rust inhibitor, the carboxylate rust inhibitor, and the ester rust inhibitor are added individually or appropriately in combination so as to be 0.1 to 20% by mass of the total amount of the base oil. If the added amount is less than 0.1% by mass, sufficient rust preventive performance cannot be imparted. If the added amount exceeds 20% by mass, the amount of these rust preventives adsorbed on the surface of the bearing member is too large, and the enclosed grease There is a risk that white tissue peeling may occur due to inhibition of the generation of the derived oxide film or the like. In consideration of ensuring the rust prevention performance and suppressing the occurrence of white structure peeling, the addition amount of these rust prevention agents is preferably 0.25 to 15% by mass.

  In order to suppress the occurrence of white tissue peeling, it becomes more effective if it is easy to form an oxide film at the rolling contact portion in addition to the action of the rust inhibitor. Therefore, it is preferable to use an organic metal salt in combination. Preferable organometallic salts include a dialkyldithiocarbamic acid compound (DTC) represented by the following general formula (1) and a dialkyldithiophosphate compound (DTP) represented by the following general formula (2).

Here, M represents a metal species, and specifically can be selected from Sb, Bi, Sn, Ni, Te, Se, Fe, Cu, Mo, and Zn. R ₁ , R ₂ May be the same group or different groups, and are selected from an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an alkylaryl group, and an arylalkyl group. Particularly preferred groups include 1,1,3,3-tetramethylbutyl group, 1,1,3,3-tetramethylhexyl group, 1,1,3-trimethylhexyl group, 1,3-dimethylbutyl group, 1-methylundecane group, 1-methylhexyl group, 1-methylpentyl group, 2-ethylbutyl group, 2-ethylhexyl group, 2-methylcyclohexyl group, 3-heptyl group, 4-methylcyclohexyl group, n-butyl group, Isobutyl group, isopropyl group, isoheptyl group, isopentyl group, undecyl group, eicosyl group, ethyl group, octadecyl group, octyl group, cyclooctyl group, cyclododecyl group, cyclopentyl group, dimethylcyclohexyl group, decyl group, tetradecyl group, docosyl group , Dodecyl group, tridecyl group, trimethylcyclohexyl group, nonyl group Propyl group, hexadecyl group, hexyl group, henicosyl group, heptadecyl group, heptyl group, pentadecyl group, pentyl group, methyl group, tert-butylcyclohexyl group, tert-butyl group, 2-hexenyl group, 2-methallyl group, allyl group , Undecenyl group, oleyl group, decenyl group, vinyl group, butenyl group, hexenyl group, heptadecenyl group, tolyl group, ethylphenyl group, isopropylphenyl group, tertiary butylphenyl group, secondary pentylphenyl group, n-hexylphenyl group , Tertiary octylphenyl group, isononylphenyl group, n-dodecylphenyl group, phenyl group, benzyl group, 1-phenylethyl group, 2-phenylethyl group, 3-phenylpropyl group, 1,1-dimethylbenzyl group, 2-phenylisopropyl group, 3-phenylhexyl group, Nzuhidoriru group, a biphenyl group and the like, and these groups may be an ether bond.

  Moreover, the organozinc compound shown by the following general formula (3)-(5) can also be used conveniently.

Where R ₃ , R ₄ may be the same group or different groups, and are selected from a hydrocarbon group having 1 to 18 carbon atoms and a hydrogen atom. In particular, R ₃ , R ₄ are both hydrogen atoms mercaptobenzothiazole zinc (general formula (3)), benzamidothiophenol zinc (general formula (4)), mercaptobenzimidazole zinc (general formula (5)) are preferably used. be able to.

  Furthermore, a zinc alkylxanthate represented by the following general formula (6) can also be suitably used.

Here, R < ₅ > is a C1-C18 hydrocarbon group.

  The organometallic salts represented by the general formulas (3) to (6) may be used alone or in combination of two or more. In addition, the combination at the time of mixing and using is not specifically limited. Moreover, the addition amount of these organometallic salts is 0.1-20 mass% with respect to the base oil whole quantity with single use and mixed use. If the addition amount is less than 0.1% by mass, there is no effect in promoting the formation of an oxide film, and if it exceeds 20% by mass, the improvement in the effect corresponding to the increment cannot be obtained, and the acid or reaction with the bearing material becomes abnormal. May accelerate and cause corrosion and abnormal wear. A preferable addition amount is 0.5 to 10% by mass.

  On the other hand, as the thickener, both organic and inorganic materials can be used, but in consideration of the influence on the environment, those containing no heavy metal are preferable. For example, metal soaps such as lithium soap, calcium soap, aluminum soap, magnesium soap, sodium soap, or composite soaps thereof, urea compounds, bentonite, silica, carbon black and the like can be appropriately selected and used. Of these, metal composite soaps and urea compounds are preferred. These may be used alone or in combination.

  The content of these thickeners is not limited as long as the grease can be formed and maintained together with the base oil, but is preferably 5 to 35 mass%, more preferably 5 to 25 mass% of the total amount of the grease composition. In the case of mixed use, the total amount is set as this content.

  In the grease composition of the present invention, other additives that have been conventionally widely added to grease compositions can be appropriately selected and added. This contains other rust preventives. However, when the influence on the environment is taken into consideration, those not containing heavy metals are preferable. Moreover, the addition amount is preferably 0.1 to 15% by mass of the total amount of grease in order to add the effect of the additive to be added while ensuring the above rust prevention performance and peel resistance. Preferably it is 0.1-10 mass%, More preferably, it is 0.1-5 mass%.

  The present invention also includes a rolling bearing in which the grease composition is enclosed. There are no restrictions on the type of rolling bearing, but the above grease composition has excellent rust prevention performance and peeling resistance, so it is used in environments where there is a lot of contact with water, especially for supporting axles of vehicles. Suitable for rolling bearings of

  The rolling bearing for a vehicle is not limited in its structure, and a unit bearing with a seal as shown in FIG. 1 can be exemplified. In this unit bearing with seal, since the seal ring 13 made of an elastic material and the sealed grease are always in contact with each other, the sealed grease is also required not to chemically attack the elastic material. As an elastic material, an acrylic rubber composition in which various reinforcing materials and fillers are blended with an acrylic rubber such as acrylonitrile butadiene rubber is generally used. As will be described later, the grease composition of the present invention includes an acrylic rubber. It does not swell or dissolve, and can be said to be suitable for such a sealed unit bearing.

Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples.
(Examples 1 to 3, Comparative Example 1)
Test greases were prepared with the formulations shown in Table 1. In any test grease, a phenolic antioxidant (2,6-di-t-butylcresol; manufactured by Tokyo Chemical Industry Co., Ltd.), an amine antioxidant (p, p'-dioctyldiphenylamine; Tokyo Kasei) Co., Ltd.), antirust agent (calcium sulfonate; “NasulR1-CA” manufactured by King) and extreme pressure agent (ashless sulfur; “Vanrube 7723” manufactured by Vanderbilt) are each 0.5% by mass. It is added as follows.

  And after filling the above test grease into a tapered roller bearing “HR30205 (inner diameter 25 mm, outer diameter 52 mm, width 16.25 mm)” manufactured by Nippon Seiko Co., Ltd., 120 ° C., It was continuously rotated for 100 hours at a radial load of 98 N, an axial load of 1470 N, and a rotation speed of 3500 rpm. After rotation, the bearing was disassembled, and the presence or absence of rust and peeling was confirmed. The results are also shown in Table 1.

  It can be seen from Table 1 that excellent rust prevention performance and peel resistance can be imparted by adding a carboxylic acid rust inhibitor, a carboxylate rust inhibitor, or an ester rust inhibitor in accordance with the present invention.

It is sectional drawing which shows an example of the unit bearing with a seal | sticker for this invention and the conventional vehicle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner ring element 2 Hub 4a, 4b Inner ring track 5 Step part 6 Male thread part 7 Nut 8 Outer ring 10a, 10b Outer ring track 11 Rolling element 12 Cage 13 Seal ring

Claims (5)

It consists of a mineral oil or synthetic oil having a kinematic viscosity at 40 ° C. of 70 to 250 mm ² / s, and 0.1 to 20 mass of at least one of a carboxylic acid rust inhibitor, a carboxylate rust inhibitor and an ester rust inhibitor. %. A grease composition comprising a base oil contained in a percentage.   2. The grease composition according to claim 1, wherein the thickener contains at least one of a metal soap, a metal composite soap, and a urea compound in a proportion of 5 to 35 mass% of the total amount of grease.   A rolling bearing comprising the grease composition according to claim 1 or 2 enclosed therein.   The rolling bearing according to claim 3, further comprising a rubber seal.   5. The rolling bearing according to claim 3, wherein the rolling bearing is used for supporting an axle.

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