A hub portion of a fluid dynamic bearing device is formed from a resin composition in which polyphenylene sulfide (PPS) is employed as a base resin and with which carbon fibers are mixed. In this manner, the wear resistance and the conductivity can be improved. Alternatively, both portions of a stationary body and a rotating body of the fluid dynamic bearing device which portions face to each other through a bearing gap are formed from a resin composition in which polyphenylene sulfide (PPS) is employed as the base resin. In this manner, excellent wear resistance can be obtained.
The present invention provides a rolling bearing, for a tenter clip, which is capable of restraining deterioration of a sealing member even though the sealing member contacts ester oil, and is excellent in reliability and durability at high temperatures. A periphery of an outer ring of the rolling bearing for use in the tenter clip of a film-stretching apparatus is lubricated with the ester oil. In the sealing member which covers openings disposed at both axial ends of an inner ring and the outer ring of the rolling bearing, at least a portion of the sealing member which contacts the ester oil is made of (A) a fluororubber molding of a vulcanizable fluororubber composition which comprises a copolymer containing tetrafluoroethylene (TFE), propylene, and a to-be-crosslinked monomer consisting of unsaturated hydrocarbon, having two to four carbon atoms, in which a part of hydrogen atoms is substituted with fluorine atoms or (B) a fluororubber molding of at least one fluororubber composition selected from a vulcanizable fluororubber composition containing a TFE-propylene binary copolymer and a vulcanizable fluororubber composition containing a vinylidene fluoride-TFE-propylene ternary copolymer.
The present invention provides lubricating grease which is excellent in durability at a high temperature, restrains a reaction from occurring between fluorine and steel, and has a long life; and a rolling bearing in which the lubricating grease is enclosed. The lubricating grease contains perfluoropolyether oil as a base oil thereof and fluorocarbon resin powder as a thickener thereof. The lubricating grease further contains an additive containing a substance capable of forming a film on a metal surface. The substance is a diurea compound having an --NH-- bond in a molecular structure thereof, an organic-acid metal salt such as sodium sebacate, molybdate such as potassium molybdate or sodium molybdate, or a bismuth-containing compound such as bismuth sulfate. The rolling bearing has an inner ring and an outer ring disposed concentrically with each other, a plurality of rolling elements interposed between the inner ring and the outer ring, and a retainer dividedly holding the rolling elements. The lubricating grease is enclosed on the periphery of the rolling elements.
A fluid dynamic bearing apparatus with an increased adhesive strength between a component having an adhesion fixing face and a bracket is provided by appropriately controlling the adhesion gap. Materials for a bracket 6 and a housing 7 are selected so that the value obtained by dividing the linear expansion coefficient of the housing 7 fixed to the inner periphery of the bracket 6 by the linear expansion coefficient of the bracket 6 having a portion 6b for mounting a stator coil 4 of a motor is not lower than 0.5 but not higher than 2.0. An adhesion fixing face 7e formed on the outer periphery of the housing 7 is adhesively fixed to the inner circumferential surface 6a of the bracket 6 with an anaerobic adhesive or an epoxy-based adhesive.
The present invention provides a hub bearing, made of carbon steel for machine structural use, which has a long life even in a strict lubricating condition by improving the resistance to peeling starting from the surface. A grease for the hub bearing contains a base oil and a thickener, and in the base oil, the number of naphthenic carbons found by an n-d-M ring analyzing method accounts for 32 to 37% of a whole number of carbon atoms in the base oil. The base oil is a mineral oil or a mixed oil of a mineral oil and a synthetic hydrocarbon oil. The thickener is a urea compound shown by the following formula (1) and is contained at 1 to 40 mass % for the entire grease. The grease for the hub bearing is enclosed in the hub bearing. ##STR00001## (In the formula (1), R.sup.2 indicates an aromatic hydrocarbon group having 6 to 15 carbon atoms, and R.sup.1 and R.sup.3 indicate at least one hydrocarbon group selected from an alicyclic hydrocarbon group and an aromatic hydrocarbon group.)