The Influence of Cage Pocket Lubrication on the Simulation of Deep Groove Ball Bearing Cage Motion

Abstract

A six degrees-of-freedom dynamic bearing model (DBM) was modified to include a novel cage pocket lubrication model. The motion of the cage was determined using the finite difference method to solve for the pressure generation and resultant forces inside of each cage pocket at each time-step of the dynamic model. The computational domain of the finite difference model was designed to reflect the specific cage pocket geometry of four common cage designs. Additionally, a bearing cage friction test rig was utilized to characterize the lubrication state inside of each cage. Experiments were performed that reveal the relationship between cage shape, ball speed, and relative ball—cage position. Specifically, information on the occurrence of kinematic starvation, the speed-dependent evacuation of oil from a cage pocket, was collected for use as an input condition to the dynamic bearing model. An inverse distance weighting scheme was utilized to predict starvation parameters for a general ball position inside of the cage pocket. Results from the dynamic simulation reveal new knowledge on the effect of cage geometry and lubrication on dynamic behavior. The inclusion of lubrication effects inside of the cage pocket reduces the median contact force between the balls and cage pocket and improves the stability of the predicted cage motion.