Experimental Analysis and Modeling of the Effects of Oil–Air Lubrication Parameters on Bearings Friction Loss of High-Speed Motorized Spindle

The friction loss of an angular contact ball bearing is a key factor restricting the development of a high-speed motorized spindle. To quantitatively calculate the effects of the oil–air lubrication parameters on the friction loss of high-speed bearings, the drag resistance and the churning resistance generated by the movement of the rolling elements in the lubricant are theoretically modeled and the percentage volume of the lubricant in the bearing cavity (XCAV) is used to characterize the effects. The friction loss of bearings is tested by two novel methods: the free deceleration method and the energy-balance method. The experimental results show that the viscous resistance loss is a major component of bearing friction loss and oil–air lubrication parameters have important influence on it. A comparison of the theoretical calculations and the experimental results is used for deriving the empirical formula of XCAV with respect to the lubricant flow, gas pressure, rotating speed, and pitch diameter. The research results of this study have important significance for the measurement, prediction and reduction of the friction loss of high-speed bearings.