Grease composition for automobile wheel bearing

Abstract

The present invention provides a grease composition for automobile wheel bearings, which contains (a) an urea thickener represented by general formula (1): R₁—NHCONH—R₂—NHCONH—R₃ (wherein R₁ and R₃ may be the same or different from each other and are each independently an aromatic hydrocarbon group having 6 to 12 carbon atoms, and R₂ represents an aromatic hydrocarbon group having 6 to 15 carbon atoms); (b) an organic molybdenum compound; and (c) a base oil. The composition of the present invention can extend the flaking life and lubrication life, and reduce the fretting wear.

Description

TECHNICAL FIELD [0001] The present invention relates to a grease composition used for automobile wheel bearings. BACKGROUND ART [0002] With respect to the automobile wheel bearings, the bearings support the vehicle's weight through the tires, and at the same time, they are operated under comparatively heavy load conditions with the application of radial, thrust and moment loads as well as impact loads from the contact point of the tires with ground depending upon the running conditions of the vehicle (non-patent document 1). This may often cause the problem of flaking as a result of metal fatigue. To extend the flaking life (i.e., fatigue life of the bearing material), a layer of lubricating oil is thickened (namely, by increasing the viscosity of the oil). However, satisfactory grease compositions have not yet been obtained. [0003] Further, while the vehicle carries a freight car, the bearings are subject to slight vibration and the like and eventually worn out to cause a phenomeno...

AI Technical Summary

Benefits of technology

[0013] The grease of the present invention can significantly extend the flaking life of the wheel bearings in the automobiles and the lubrication life, and reduce the fretting wear. In particular, the grease of the present invention can extend the useful life of cars to 10 years and guarantee 1,200,000 kilometers of driving, for example, by preventing the galling at the end of the rollers in the tapered roller bearings.

Problems solved by technology

This may often cause the problem of flaking as a result of metal fatigue.

However, satisfactory grease compositions have not yet been obtained.

Further, while the vehicle carries a freight car, the bearings are subject to slight vibration and the like and eventually worn out to cause a phenomenon called fretting in some cases.

However, there is no grease composition that can meet such requirements satisfactorily.

The grease composition will deteriorate due to oxidation and cannot exhibit its desired performance as the period of service of a car is prolonged or the mileage is accumulated.

In the tapered roller bearings, when oil in the form of a layer runs out around the periphery of the rollers, the end portions of the rollers may be damaged while sliding.

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