This study treats modeling of a class of OHC-type cam valve train with a fluctuating rocker arm ratio known as finger follower cam system.
The six-DOF model includes the angular motion of the follower and the spring surge motion. The dynamic model also reflects the variation of the contact point between cam and follower and the damping coefficient variation of hydraulic tappet. The valve displacement and velocity and the contact forces associated with the follower are numerically simulated with camshaft speed varied for a cam profile given. Tappet displacement, valve displacement and follower strain are measured and compared with the simulation results in order to verify the validity of the proposed model.