A full numerical solution to the coupled cam–roller and roller–pin contact in heavily loaded cam–roller follower mechanisms

Abstract

In cam–roller follower units two lubricated contacts may be distinguished, namely the cam–roller contact and roller–pin contact. The former is a nonconformal contact while the latter is conformal contact. In an earlier work a detailed transient finite line contact elastohydrodynamic lubrication model for the cam–roller contact was developed. In this work a detailed transient elastohydrodynamic lubrication model for the roller–pin contact is developed and coupled to the earlier developed cam–roller contact elastohydrodynamic lubrication model via a roller friction model. For the transient analysis a heavily loaded cam–roller follower unit is analyzed. It is shown that likewise the cam–roller contact, the roller–pin contact also inhibits typical finite line contact elastohydrodynamic lubrication characteristics at high loads. The importance of including elastic deformation for analyzing lubrication conditions in the roller–pin contact is highlighted here, as it significantly enhances the film thickness and friction coefficient. Other main findings are that for heavily loaded cam–roller follower units, as studied in this work, transient effects and roller slippage are negligible, and the roller–pin contact is associated with the highest power losses. Finally, due to the nontypical elastohydrodynamic lubrication characteristics of both cam–roller and roller–pin contact numerical analysis becomes inevitable for the evaluation of the film thicknesses, power losses, and maximum pressures.