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Reduction in friction ensures fuel economy, control on emissions and durability of components in internal combustion engines. A modern gasoline internal combustion engine was instrumented to determine the friction values at the cam–roller interface considering the effects of surface treatment and engine operating state. A series of tests under different operating speeds and lubricant inlet temperatures were undertaken using both an original surface roller and a Wonder Process Craft (WPC) surface-treated engine roller. The results clearly revealed a substantial reduction in friction magnitude for the WPC surface-treated engine roller in comparison to the original roller while operating under similar conditions, indicating their strong potential for employment in engines. An increase in friction with the rise in temperature was also observed for both types of rollers, whereas increased lubricant entraining velocity due to higher operating speed had the opposite impact. A considerable reduction in frictional drive torque ranging from 8% to 28% was observed by employing the WPC-treated roller in comparison to original/untreated roller at various operating conditions, which signifies the strong potential for employment of WPC surface treatment in the roller/follower valve train engines. [ABSTRACT FROM AUTHOR]

Reduction in friction ensures fuel economy, control on emissions and durability of components in internal combustion engines. A modern gasoline internal combustion engine was instrumented to determine the friction values at the cam–roller interface considering the effects of surface treatment and engine operating state. A series of tests under different operating speeds and lubricant inlet temperatures were undertaken using both an original surface roller and a Wonder Process Craft (WPC) surface-treated engine roller. The results clearly revealed a substantial reduction in friction magnitude for the WPC surface-treated engine roller in comparison to the original roller while operating under similar conditions, indicating their strong potential for employment in engines. An increase in friction with the rise in temperature was also observed for both types of rollers, whereas increased lubricant entraining velocity due to higher operating speed had the opposite impact. A considerable reduction in frictional drive torque ranging from 8% to 28% was observed by employing the WPC-treated roller in comparison to original/untreated roller at various operating conditions, which signifies the strong potential for employment of WPC surface treatment in the roller/follower valve train engines.

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. [ABSTRACT FROM AUTHOR]

• An innovative technique has been developed to measure friction in roller follower valve train. • A numerical approach based on mixed lubrication concept is developed to predict the friction. • Rise in camshaft speed resulted in reduction of friction. • Increased asperity interaction at high temperature resulted in higher friction. • Predicted and measured friction has been found in good agreement. Fuel efficiency in automobiles has grown in importance greatly in past few years but it has also raised concerns about friction and durability of components in engines. The valve trains have to operate in harsh and transient operating conditions frequently promoting friction. In this paper, an innovative and effective technique based on strain gauges has been presented which is used to measure the instantaneous friction in roller follower valve train. Instrumentation, friction measurement system, test procedures and results have been explained in detail. A numerical approach based on mixed lubrication concept considering roller sliding has also been presented to predict the friction. Rise in camshaft speed resulted in reduction of friction whereas increased asperity interaction at high operating temperature yielded relatively higher friction magnitude. Predicted and measured friction in roller follower valve train has been found in good agreement. [ABSTRACT FROM AUTHOR]