Design of the valve train mechanism of an internal combustion engine with four stroks

When designing the cam profiles of an automobile engine, beside the performance of gaz flow, one should consider that the system should have a long life-period, work client and without vibration, generate lesser friction forces and consume lesser power. The higher flow performance requires relatively higher valve displacement. However, for a system having long life-period, working client and without vibration and generating lowest friction forces, a lower valve displacement is required. Design of the cam profile is an optimization satisfying both conditions.In this study the cam profiles of the prototype of an Internal Combustion Engine financially founded by the Gazi University Research Projects Unite, were designed, manufacture and tested. By regarding the statistical values used before, the lifts of valves were selected as 6 mm and using the classical spline method, the cam profiles were designed. While determining the cam profiles, double point contact of the cam surface to the follower surface and higher accelerations causing the followers to jump off the cam were avoided. The minimum spring force possible was obtained by changing cam profiles. Adaptability of valve system of Peugeot-406 engine to the prototype being constructed was investigated from dynamic point of view. Effects of variations of valve lift and valve fall periods on the dynamic behavior of valve system was examined under the same lift condition. It was determined that as long as the speed of the cam shaft remains below 4500 rpm, the followers do not jumps off the cam. Effects of open remaining periods of valves on the engine performance was experimentally investigated by manufacturing four different cam profiles having 120º, 124º, 128º and 130º total open remaining periods.