The advantages of Variable Valve Actuation (VVA) in the aspects of improved engine performance, fuel economy and reduced emissions are well known in the industry. However, the design and optimization of such systems is complex and costly. The design process of VVA mechanisms can be greatly accelerated through the use of sophisticated simulation tools. Predictive numerical analysis of systems to address design issues and evaluate design changes can assure the required performance and durability. One notable requirement for the analysis and design of novel mechanically-actuated VVA systems is a general-purpose fast and easy-to-use planar mechanism kinematics analyzer with cam solution/design features, which can be applied to general mechanisms.
This paper introduces a general simulation and design tool, which features general planar kinematics and multi-body dynamics analysis capabilities, as well as integrated hydromechanics and hydraulics to model devices such as lash adjusters and cam phasers. Application of the methodology to various mechanically-driven variable valve actuation systems is discussed, with focus on a specific system. The modeling process is broken down into multiple stages. First, the analysis of kinematic motion of valvetrain components along with the procedure to calculate the cam shape profile required to produce the desired valve lift is described. Second, a constrained-dynamics simulation of a rigid system is carried out in search of nominal (quasi-dynamic), inter-component forces, valve spring margin and cam-follower separation speed. Third, a complete multi-body dynamics analysis, which considers the elasticity of valvetrain components and inter-component contacts, is employed to produce a wide array of detailed dynamic predictions. Ways of rapidly optimizing the key design parameters through the use of dedicated numerical analysis are briefly discussed.