Abstract: A hydrodynamic type oil-impregnated sintered bearing includes a porous bearing body of sintered metal having a bearing surface in which hydrodynamic pressure generating grooves slating against an axial direction are provided. Lubricating oil or the base oil of lubricating grease to be impregnated into the bearing body is selected from among (a) mixtures of poly-?-olefin or hydrogenated compound thereof and ester and (b) ester. The ester is preferably polyol ester. In the cases of the lubricating grease, the thickener of the lubricating grease is preferably composed of urea compound. A plurality of bearing surfaces may be formed on the inner periphery of the bearing body so as to be separated from one another. The hydrodynamic type oil-impregnated sintered bearing may be suitably applied to a spindle motor for information equipment.

Abstract: A hydrodynamic type oil-impregnated sintered bearing includes a porous bearing body of sintered metal having a bearing surface opposed to a sliding surface of a rotating shaft, hydrodynamic pressure generating grooves slanting against an axial direction provided in the bearing surface, and lubricating oil or lubricating grease impregnated in pores inside the bearing body, wherein a rate of area of surface holes on the bearing surface is set within a range of 3%-15%, the surface holes being distributed substantially uniformly over the whole area of the bearing surface including areas of the hydronamic pressure generating grooves, wherein the lubricating oil or a base oil of the lubricating grease forms a lubricating film in a bearing clearance, and wherein the lubricating oil or a base oil of the lubricating grease is a lubricating oil selected from among mixtures of poly-?-olefin or hydrogenated compound thereof and a defined phosphoric ester.

Abstract: A hydrodynamic type oil-impregnated sintered bearing includes a porous bearing body of sintered metal having a bearing surface in which hydrodynamic pressure generating grooves slating against an axial direction are provided. Lubricating oil or the base oil of lubricating grease to be impregnated into the bearing body is selected from among (a) mixtures of poly-?-olefin or hydrogenated compound thereof and ester and (b) ester. The ester is preferably polyol ester. In the cases of the lubricating grease, the thickener of the lubricating grease is preferably composed of urea compound. A plurality of bearing surfaces may be formed on the inner periphery of the bearing body so as to be separated from one another. The hydrodynamic type oil-impregnated sintered bearing may be suitably applied to a spindle motor for information equipment.

Abstract: There is provided a durable low-torque lubricating oil for bearings and fluid dynamic bearings, porous oil-impregnated bearings and hydrodynamic type porous oil-impregnated bearings suitable for use as bearings in small-sized spindle motors for information equipment. The lubricating oil composition comprising (A) a diester of a monovalent aliphatic alcohol containing 6-10 carbon atoms and a saturated aliphatic dicarboxylic acid containing 10 carbon atoms as base oil and (B) 3-20% by weight of a low-viscosity lubricating oil with a kinematic viscosity of less than 11 mm2/s at 40° C., a fluid dynamic pressure bearing unit or a porous oil-impregnated bearing unit containing said lubricating oil composition or a spindle motor provided with said bearing unit.

Abstract: Disclosed is a lubricating composition such as a lubricant, a lubricating grease, or a rust preventive oil for use in a torque limiter and a ball-and-roller bearing; the lubricating composition having chemical attack resistance for a synthetic resin molded product. The lubricating composition comprises as a base oil at least one synthetic saturated hydrocarbon oil selected from the group consisting of a poly-&agr;-olefin, and an ethylene-&agr;-olefin copolymer. When a phosphoric acid ester is used as a compounding agent, or at lease one lubricating grease selected from the group consisting of an urea compound, silica powder, and bentonite powder is mixed therein, the lubricating composition is a rust preventive oil using a metal salt of sulfonic acid and the like. The lubricating composition is suitably used for machine parts of a business machine including the synthetic resin molded product.

Abstract: There is provided a durable low-torque lubricating oil for bearings and fluid dynamic bearings, porous oil-impregnated bearings and hydrodynamic type porous oil-impregnated bearings suitable for use as bearings in small-sized spindle motors for information equipment. The lubricating oil composition comprising (A) a diester of a monovalent aliphatic alcohol containing 6-10 carbon atoms and a saturated aliphatic dicarboxylic acid containing 10 carbon atoms as base oil and (B) 3-20% by weight of a low-viscosity lubricating oil with a kinematic viscosity of less than 11 mm2/s at 40 ° C., a fluid dynamic pressure bearing unit or a porous oil-impregnated bearing unit containing said lubricating oil composition or a spindle motor provided with said bearing unit.

Abstract: Disclosed is a lubricating composition such as a lubricant, a lubricating grease, or a rust preventive oil for use in a torque limiter and a ball-and-roller bearing; the lubricating composition having chemical attack resistance for a synthetic resin molded product. The lubricating composition comprises as a base oil at least one synthetic saturated hydrocarbon oil selected from the group consisting of a poly-&agr;-olefin, and an ethylene-&agr;-olefin copolymer. When a phosphoric acid ester is used as a compounding agent, or at lease one lubricating grease selected from the group consisting of an urea compound, silica powder, and bentonite powder is mixed therein, the lubricating composition is a rust preventive oil using a metal salt of sulfonic acid and the like. The lubricating composition is suitably used for machine parts of a business machine including the synthetic resin molded product.