A grease composition containing base oil, a thickener, and an additive, wherein said additive contains at least one kind selected from among a phosphite ester shown by a chemical formula (1) or a phosphite ester shown by a chemical formula (2); a content of said phosphite ester is 0.5 to 4 parts by weight for 100 parts by weight which is a total of an amount of said base oil and that of said thickener; and said additive contains neither phosphite esters other than said phosphite ester shown by said formula (1) or by said formula (2) nor phosphate esters having organic groups whose carbon number is not less than three:

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Embodiments of the present disclosure are directed to an adhesive layer, bearing including the adhesive layer, and methods of forming. The adhesive layer can include a mixture of a first polymer, a second polymer, and a third polymer, wherein the third polymer is a modified fluoropolymer of the second polymer. In a particular embodiment, a weight ratio of a weight content of the second polymer to a weight content of the third polymer in the mixture can be at least 12:1. In another particular embodiment, the adhesive layer can have a normalized peel strength of at least 4.8 N/in/microns.

A lubricant fluid comprising a base oil, which utilizes carboxylic esters of carboxyl di-end-capped-polyethylene glycols, or a mixture thereof, to have ultra-low viscosity, high flash point, high viscosity index (VI), excellent low temperature properties (viscosity and pour/freeze points), and low elastohydrodynamic (EHD) shear strength, and to enable the production of high efficiency fluids with enhanced temperature properties for machines or machine elements that operate in the elastohydrodynamic regime of lubrication.

Object

To provide a fluid dynamic pressure bearing oil and a fluid dynamic pressure bearing filled with the fluid dynamic pressure bearing oil, and to provide a spindle motor and a disk drive device including the spindle motor in which the fluid dynamic pressure bearing oil and the bearing are used, thereby suppressing adhesion of a volatile component to a magnetic disk or the like even when the fluid dynamic pressure bearing oil is volatilized, so that occurrence of HDD read/write errors can be suppressed.

Solution

A fluid dynamic pressure bearing oil contains at least one compound selected from the group consisting of a monoester compound represented by the following Formula (1) and a diester compound represented by the following Formula (2): R.sub.1C(O)OR.sub.2 (1) (where R.sub.1 is an alkyl group having 10 or more carbon atoms in total, R.sub.2 is an alkyl group having 9 or more carbon atoms in total, and R.sub.3-E.sub.1-R.sub.4-E.sub.2-R.sub.5 (2) (where R.sub.3 and R.sub.5 are each independently an alkyl group having 8 or more carbon atoms in total, R.sub.4 is an alkylene group having 4 or more carbon atoms in total, and E.sub.1 and E.sub.2 are each independently C(O)O or OC(O).

A rotary shaft device includes a housing, a rotary shaft rotatably mounted relative to the housing, a pressurization member radially disposed between a main body of the rotary shaft and the housing, and at least one cooling channel. The pressurization member and the main body of the rotary shaft define between them a pressurization reservoir configured to receive a volume of a cooling fluid. The at least one cooling channel extends between a fluid inlet and a fluid outlet, has at least one component along the axis of rotation, and is in fluid communication, at the fluid inlet, with the pressurization reservoir.

A grease composition for vehicular hub unit bearings is provided, in which a base oil is a synthetic hydrocarbon oil having a kinematic viscosity at 40 C. of 25-50 mm.sup.2/s, a thickener is an alicyclic aliphatic diurea compound, based on a total mass of the composition, 0.1-5% by mass of a carboxylic acid-based corrosion inhibitor, 0.1-5% by mass of a carboxylic acid salt-based corrosion inhibitor, and 0.1-3% by mass of an amine salt of a fatty acid are contained, and a worked penetration is 220-270.

A lubricant fluid comprising a base oil, which utilizes carboxylic esters of carboxyl di-end-capped-polyethylene glycols, or a mixture thereof, to have ultra-low viscosity, high flash point, high viscosity index (VI), excellent low temperature properties (viscosity and pour/freeze points), and low elastohydrodynamic (EHD) shear strength, and to enable the production of high efficiency fluids with enhanced temperature properties for machines or machine elements that operate in the elastohydrodynamic regime of lubrication.

A rolling bearing (1) includes an outer ring (2), an inner ring (4), and a plurality of rolling elements (6) arranged between the outer and inner ring (2, 4). The rolling bearing (1) is provided with lubricant. The outer ring (2) has an outer contact width (b.sub.o) between the outer ring (2) and the rolling elements (6). The inner ring (4) has an inner contact width (b.sub.i) between the inner ring (4) and the rolling elements (6). A ratio =b.sub.i/b.sub.o between the inner and outer contact width (b.sub.i, b.sub.o) is larger than 1.65 or a ratio =b.sub.i/b.sub.o between the inner and outer contact width (b.sub.i, b.sub.o) is larger than 0.97 and smaller than 1.06 or a ratio =b.sub.i/b.sub.o between the inner and outer contact width (b.sub.i, b.sub.o) is smaller than 0.68.