Dynamic Characteristics Analysis Of A Continuously Variable Valve Actuation Mechanism

The main purpose of the valve train of the engine is controlling the inlet and exhaust process in cylinders. The valve timing and valve lift of conventional valve train is fixed, which can only guarantee the optimized engine performance for the standard condition and circumstance, and it is hard to juggle all the conditions to match the requirement of the valve timing. However, the variable valve train, which manages to ensure the engine operate under the suitable conditions through controlling the valve timing, valve lift and valve duration and thereby improve the comprehensive performance of the engine, has achieved a wild use.A novel continuously variable valve actuation mechanism is taken as an object to be researched in this paper. The simulation analysis of the dynamic characteristics based on VALDYN has been presented to prove the practicability of the mechanism. Major research work can be summoned up as follows:Understanding the structure characteristic and operating principle of the mechanism profoundly, and establishing the dynamic model in VALDYN. Then kinematic analysis of the model is presented. The analysis results indicate that kinematic curves of valve lift accord well with the dynamic simulation curves of valve lift, which could confirm the accuracy of the model and the parameters of the model.Dynamic characteristics of the mechanism are analyzed under various lift phases and camshaft speeds. The simulation curves of valve lift, valve velocity, valve acceleration and compressive loads on components are researched, and, especially, the loads loss phenomenon of loads curves and the valve spring force is discussed. Then, natural frequency range of the valve train is calculated.Dynamic characteristics of the mechanism based on test data are analyzed with different lift phases and camshaft speeds. Results show that the mechanism sustains proper performance in the valve timing and event control through the whole engine speed range, which confirms the practical value of the mechanism.