US Patent 7267488 Rolling bearing and spindle device for machine tools

A grease-lubricated rolling bearing has an outer ring having an outer ring race in an inner peripheral surface thereof, an inner ring having an inner ring race on an outer peripheral surface thereof, rolling elements rollably provided between the outer ring race and the inner ring race, and a grease supply element for supplying an additional grease in the rolling bearing. The amount of the additional grease to be supplied at a time is predetermined to be from 0.1 to 4% of the volume of space in the bearing.