Parametric Study and Prediction of Lubrication Oil Film Thickness in Sliding and Rolling Interface Valve Trains 2018-01-0931

To achieve acceptable valve train lubrication with low viscosity oil is challenging. Understanding the effect of valve train design parameter on valve train lubrication is important. In this study rocker arm valve train mechanism is analyzed to check the influence of valve train design parameters on lubrication at cam and rocker face interface. In valve train lubrication, lubrication oil film thickness play important role in valve train wear and friction. Main objective is to maintain acceptable oil film thickness at peak valve lift and minimizing the duration of critical minimum oil film thickness at cam flank to avoid wear at cam/ roller rocker follower interface when using low viscosity oil. Cam nose wear effect the engine performance and wear at cam flank change the dynamic characteristics of valve train.

Lubrication oil entrainment velocity is an important parameter controlling the lubrication oil film thickness in elasto hydrodynamic lubrication zone at cam / roller rocker interface. Lubrication oil film thickness is proportional to lubrication entrainment velocity. High entrainment velocity is better for high lubrication oil film thickness. Valve train design parameters including contact geometry at cam rocker interface mainly control the entrainment velocity. Entrainment velocity also increases with engine operating RPM.

This study is done using 1-D multi body dynamics simulation tools to quantify the effect of type of contact at cam / rocker face interface (slider and roller), valve train design parameter (cam base circle radius, roller radius) and different grade lubrication oil on lubrication oil film thickness which influences the friction and wear of valve train. Simulation methodology is developed to predict tribology behavior at cam / rocker face contact point.