Kinematic Analysis of Continuous Variable Valve Lift Mechanism for SI Engine

Variable valve Actuation (VVA) systems are being increasingly used in IC engine. Recently novel valve actuation mechanism like continuous variable valve lift (CVVL) is being explored to regulate engine output without conventional throttle valve and this reduces the pumping losses especially at part load in SI engines. In this paper numerical model for the kinematic analysis of a CVVL mechanism is presented using MATLAB. It consists of eccentric shaft fitted with a series of intermediate rocker arm, which in turn control the degree of valve lift. The main characteristic of this mechanism is that it uses a general curve contact between the elements, which is determined using theory of envelope curve. The mechanism’s system of equations solving principle is based on the Newton-Raphson numerical method. The kinematic analysis of mechanism results in the family of the valve lift laws offering a continuous variation of valve lift with valve displacement starting from around 1mm lift to maximum around 8mm lift. Kinematic analysis of mechanism is evaluated with Ricardo VALDYN-Kinematics using the contact curve obtained in numerical analysis. Kinematic parameters like valve lift, velocity, acceleration are obtained. The proposed CVVL mechanism has been further integrated on 200cc DOHC single cylinder engine. The experimental results, such as valve lift variation at different operating conditions, valve opening and closing timings, are compared with the simulation model results and are found to be in good agreement under the given set of operating conditions.