In recent years, world-wide automotive manufacturers have been continuously working to improve the fuel efficiency of IC engine and valve train friction contribute up to 30% of overall friction loss. Oil viscosity plays an important role in reducing overall engine friction, but it adversely affects the function of Valve train in terms of wear and reliability.
Now a days HLA/RFF type (Type-II) valve train is mostly used in Internal Combustion engine to reduce friction and automatic lash adjustment. HLA (hydraulic lash adjuster) 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.
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”, an undesired phenomenon characterized by excessive HLA plunger displacement that can lead to Engine valve seating issues, engine performance degradation and risk of significant damage to engine due to valve and piston hitting.
This paper presents an approach that combines multibody dynamic simulation with experimental correlation to predict and analyze 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 is established between multibody dynamic simulation and actual testing.