Effect of flash temperature on engine valve train friction

This paper describes the development of a numerical approach based on friction and lubrication analysis to predict the flash temperature and its effects on friction at cam/follower interface. Simulation results showed that the rise in flash temperature resulted in decrease of friction and oil film thickness at cam/tappet contact particularly at high camshaft operating speeds. The flash temperature for direct acting valve train was found significantly higher than roller follower configuration due to higher sliding velocity and friction force. In direct acting valve train, the temperature of lubricant approached the fire point of lubricant and may lead to failure of oil film thereby promoting scuffing and polish wear of tribological components.