ROLLING DEVICE EMPLOYING LUBRICATING GREASE COMPOSITION AND ELECTRIC POWER STEERING APPARATUS EMPLOYING THE ROLLING DEVICE

• Main Authors: KUWABARA, HIROFUMI, ASAKURA, TOSHIHIRO, SUGIMORI, SHIGEYUKI
• Format: Patent
• Language: English; French; German
• Published: 12.09.2012
• Subjects: BEARINGS; BLASTING; CHEMISTRY; ELEMENTS OR CRANKSHAFT MECHANISMS; ENGINEERING ELEMENTS AND UNITS; FLEXIBLE SHAFTS; FUELS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVEFUNCTIONING OF MACHINES OR INSTALLATIONS; HEATING; INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATINGCOMPOSITIONS; LIGHTING; LUBRICANTS; LUBRICATING COMPOSITIONS; MECHANICAL ENGINEERING; METALLURGY; PEAT; PETROLEUM, GAS OR COKE INDUSTRIES; ROTARY BODIES OTHER THAN GEARING ELEMENTS; SHAFTS; TECHNICAL GASES CONTAINING CARBON MONOXIDE; THERMAL INSULATION IN GENERAL; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATINGINGREDIENTS IN A LUBRICATING COMPOSITION; WEAPONS

A rolling device is provided which employs a lubricating grease composition which considerably diminishes irregular friction fluctuations occurring on rolling/sliding friction surfaces, shows stable low-torque characteristics in a wide temperature range, can retain a sufficient oil film even at high temperatures, has a long life, and contains a novel thickener. Also provided is an electric power steering apparatus employing the rolling device. The rolling device is characterized by employing a lubricating grease composition comprising: a thickener which is a mixed thickener comprising a mixture of (a) one or more diurea compounds which are one or more aliphatic diurea compounds having an average molecular weight of 500-750 in which 10-70% by mole of the linear hydrocarbon groups are unsaturated components, the aliphatic diurea compounds having been produced using as a raw material one or more primary amines having a total amine value in the range of 200-400, (b) at least one fatty acid metal salt, and (c) at least one amide compound selected from the group consisting of aliphatic amides and aliphatic bisamides represented by formulae (I) and (II): €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒR 1 CONH 2 €ƒ€ƒ€ƒ€ƒ€ƒ(I) €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒR 1 CONHR 2 NHCOR 1 €ƒ€ƒ€ƒ€ƒ€ƒ(II) (wherein R 1 represents a saturated or unsaturated alkyl group having 15-17 carbon atoms and R 2 represents a methylene group or an ethylene group), the proportions of (a) and of (b) and (c) satisfying the relationship: a / b + c = 0.2 - 10 provided that (1) the proportion of ingredient (a) is 1-10, (2) the proportion of ingredient (b) is 0.5-2.5, and (3) the proportion of ingredient (c) is 0.5-2.5, the amount of the thickener being 2-30% by weight, based on the whole composition; (d) a base oil which is a lube base oil having a pour point of -25°C or lower and comprising a synthetic hydrocarbon oil as the main component; and (e) an additive which is a mixture comprising an organomolybdenum complex, an organozinc compound of a dithiocarbamic acid, and an organozinc compound of dithiophosphoric acid, the amount of the additive being 1-7% by weight, based on the whole composition.