US Patent 7090404 Rolling element bearing for ultra-low viscosity fluids

A rolling element having comprises an inner ring, an outer ring and a series of rolling elements which are in contact with the raceways of the rings, an ultra-low viscosity fluid being present in the contacts having a kinematic viscosity ν=(ηo/ρ) of less than 2 mm2/s, wherein the surfaces of the rings and the rolling elements have asperities which can have solid-to-solid contact during operation of the bearing. A factor <i>Dq</i> is defined which is equal to (I) whereby the solid-to-solid contact of the asperities is reduced by selecting such design parameters and operating conditions of the bearing that <i>Dq</i> is in the range from 8.0×10−6 mrad s1/2 to 1.36×10−4 mrad s1/2.