The Effects of Cage Flexibility on Ball-to-Cage Pocket Contact Forces and Cage Instability in Deep Groove Ball Bearings

Rolling element bearings provide near frictionless relative motion between two rotating parts. Automotive transmissions use various ball and rolling element bearings to accommodate the relative motion between rotating elements. In order to understand changes in bearing performance due to the loads imposed through the transmission, advanced modeling of the bearing is required.

This paper focuses on the effects of cage flexibility on bearing performance. A flexible cage model was developed and incorporated into a six degree-of-freedom dynamic, deep groove ball bearing model. A lumped mass approach was used to represent the cage flexibility and was validated through an ANSYS forced response analyses of the cage. Results from the newly developed Flexible Cage Model (FCM) and an identical numerical model employing a rigid bearing cage were compared to determine the effects of varying ball-to-cage pocket clearance and cage stiffness on cage motion and ball-to-cage pocket contact forces. The rigid cage model predicts larger (up to 70%) average ball-to-cage pocket normal contact forces than those computed using the FCM. Additionally, the FCM predicts a smaller optimal ball-to-cage pocket clearance than that predicted by the rigid cage model in some cases. The dynamics of the cage and the average ball-to-cage pocket contact force were found to be influenced most by the circumferential stiffness of the cage.