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

摘要

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.