Study of mixed-EHL traction coefficient between cam-roller follower interface under different operating conditions

Abstract

In heavy duty vehicles, high power density (power throughput/ weight) is desired to achieve the high fuel efficiency. The increasing demand of high power output results in harsh operating conditions (high load, high surface temperature) in which tribological components such as cam/roller follower are enforced to operate. The traction between cam-roller interface highly depends on the contact conditions between roller-pin interface, and the slippage between roller-pin interface may leads to high friction coefficient between cam/roller follower. In this work, a simplified mixed-EHL model is developed to study the traction between the cam/roller follower interface by considering coupling between roller-pin and cam-roller contacts. The develop mixed-EHL model is validated with published results in order to verify the correctness of the model. It is found that slide-to-roll ratio (SRR) increases with an increase in load torque. The effect of surface roughness on performance parameters is presented. Surface maps of SRR, lambda ratio and asperity load ratio for feasible range of maximum contact load and cam speed are also discussed.