Profiles and springs optimization in a VVA distribution system for internal combustion engines

For many decades, compromises inherent with fixed valve lift and event timing solicited engine designers to consider Variable Valve Actuator (VVA) systems as a possible option. In recent years, some relatively basic forms of VVA have been introduced into the market. VVA systems have attracted a lot of attention because of their ability to control valve events independently of crankshaft rotation, providing reduced pumping losses (work required to draw air into the cylinder) during low-load operation, and increased torque performances over a wider range than in conventional spark-ignition engines. VVA also allows control of internal exhaust gas recirculation (by controlling the valve overlap), making possible to control the NOx emissions produced during combustion. The paper describes the EATON VVA system and the optimization process to find the best-contact components profiles and to minimize contact stresses and springs parameters. The successful optimization process, based on a Genetic Algorithm, has been performed using the ESTECO modeFRONTIER software. The simulation of the mathematical model, using MDI ADAMS, demonstrates that loads, accelerations, contact stresses at 6000rpm are lower than the maximum allowable values.