Dynamic analysis of rotationally flexible cam mechanisms

Abstract

A novel mechanism for the actuation of valves in an internal combustion (IC) engine is described. Previous publications are reviewed and it is shown that the mechanism has received very little attention, in particular no dynamic analysis of it has been published. The mechanism features a shaft driving a cam through a coupling of sufficient rotational flexibility to permit significant angular offsets to develop during the cycle. A differential equation of motion of a simplified system is derived and solved using two methods. The theory requires a knowledge of twelve fundamental system dynamic parameters from which a prediction of angular offset of the camlobe throughout the cycle is produced. A dataset was obtained from a purpose built apparatus which recorded the angular offset of the camlobe with respect to the camshaft for a range of rotational speed values. Results graphs are presented and the level of agreement between theory and experiment is discussed. The work demonstrates for the first time that useful predictions of simplified mechanism performance can be obtained from the model developed. Recommendations for further work in this area are made.