Development and validation of a rigid–flexible coupled dynamic valve-train model

Abstract

A rigid–flexible coupled dynamics model has been developed to analyse the dynamic behaviour of a pushrod valve-train system of an internal combustion engine. The elastic vibration mechanism of each flexible component is described in a floating reference frame. The mechanical impacts in a valve-train system at the opening and closing events of the valve are affected by the contact stiffness and damping of contact components. The contact force model for the cam–tappet interface was developed based on the elasto-hydrodynamic lubrication theory of finite line conjunction. The finite-difference method is used to solve the rigid–flexible coupled dynamic equations. The algorithm of finite difference and the boundary conditions have been carefully selected to solve the fourth-order Bernoulli–Euler beam equation. Experiments were conducted on a motor-driven valve-train system from a four-cylinder diesel engine. The measured valve displacement, acceleration, and contact forces showed excellent consistency with the predicted results. The rigid–flexible coupled dynamics model has shown improved accuracy compared to the lumped rigid mass system in analysing the dynamic performance of the valve-train system.