Grease lubrication of miniature ball bearings

Abstract

Estimation of the power loss in miniature ball bearing grease lubricated is a complex problem. Usually the applied loads (radial and axial) have small values and the methodologies recommended by the bearing companies are cannot applied for these conditions. For a ball bearing, some friction processes have differential contribution to the total friction torque and power loss. For very low loads, the lubricant is the most important source for friction torque. In the present paper the authors determined experimentally the friction torque both in a standard 7000C angular contact ball bearing (ACBB) and a modified 7000C ACBB containing only 3 balls without cage, operating with very low axial load and lubricated with lithium soap grease. The experimental values of the friction torque have been correlated with the theoretical Houpert’s IVR model developed for hydrodynamic rolling resistances in ball race contacts considering the viscosity of the base oil of grease.