Hydraulic Lash Adjuster Dynamic Behavior Prediction Using Multibody Dynamic Simulation and Co-Relation with Testing to Improve Valve Train Design Robustness

<div class="section abstract"><div class="htmlview paragraph">In recent years, world-wide automotive manufacturers have been continuously working to improve the fuel efficiency of Internal Combustion Engine (ICE). Only valve train friction contributes up to 30% of overall friction loss. Oil viscosity plays a significant role in reducing overall engine friction, but it adversely affects the function of valve train in terms of wear and durability.</div><div class="htmlview paragraph">Now a days Hydraulic Lash Adjuster (HLA) /Roller Finger Follower (RFF) (Type-II) type valve trains commonly used in ICE to reduce friction and automatic valve train lash adjustment. HLA plays a crucial role in the RFF/HLA type valvetrain in IC engine. Understanding the valve train dynamic behavior due to HLA is essential for engine designers to improve engine performance and durability.</div><div class="htmlview paragraph">The study aims to accurately predict the behavior of Hydraulic lash adjuster under various operating conditions using multibody dynamic simulation approach. Most significant concern in HLA operation is potential occurrence of “Valve Pump-up” phenomenon, an undesired phenomenon characterized by excessive HLA plunger displacement leading to valve remain open after valve lift duration. Valve Pump-up can lead to engine valve seating issues, engine performance degradation and risk of severe damage to engine due to valve and piston hitting. This paper presents an approach that combines multibody dynamic simulation with experimental correlation to predict the dynamic behavior of hydraulic lash adjuster, specially targeting the detection of Valve Pump-up occurrences. Actual dynamic behavior of valve and HLA under worst case scenario checked in testing and correlation established between multibody dynamic simulation and actual testing.</div></div>