Abstract
An innovating solution for throttle-free load control for spark-ignition engines is variable valve timing system with continuous valve lift (VVTL System, or VVA - Variable Valve Actuation System). A variable valve timing mechanism which can provide continuous valve lift (VVL System) represents a good solution for internal combustion engines to become (1) more efficient, with an improved dynamic performance, to generate fewer emissions by reducing fuel consumption and, furthermore, allows technologies like gasoline direct injection (GDI), homogeneous charge compression ignition (HCCI) / controlled auto ignition (CAI), etc. to perform an optimized operation. In this paper is presented the cam synthesis and design optimization of a valve timing mechanism with continuous valve lift variation and constant duration (2). The approached optimization objectives are: the minimum value of cam radius of curvature (geometric design parameter), the maximum and minimum valve lift which mechanism must assure (operation parameters). The analytical method used for the cam synthesis of the mechanism, which precedes the optimization procedure, is based on the theory of envelopes (3). It is also presented a numerical example, in which the solving principle is based on a numerical method.
Keywords: Timing Mechanism, Variable Valve Lift, Cam Synthesis, Mechanism Optimization, Analytic Method