Simulation And Design Of A Continuously Variable Valve Lift Mechanism

The study of continuous variable valve lift technology has a great significance on the energy saving of gasoline engine.The continuous variable valve technology allows the engine to acquire the desired the valve lift in the high-speed and low-speed areas,thereby improving the engine high-speed power and low-speed torque,to enhance the overall performance of the engine,especially under partial load conditions,improving the fuel economy greatly.This paper studies a continuous variable valve lift mechanism(EVVTL)which can simultaneously realize the valve lift and valve timing adjustment.This paper detailedly describes the structure and working principle of the mechanism,analyzing the relationship between the valve lift and the valve timing.According to the structural characteristics of EVVTL mechanism,the simplification and assumptions are made,the mathematical model is built,and the corresponding calculation software is developed.The results show that the variable valve timing is delayed with the increase of valve lift under given structural parameters.Starting from the starting point,when the revolution angle of the camshaft axis line is between 0?50 degrees,the intake valve opening time is relatively close.With the revolution angle further increase,the intake valve opens in advance.The maximum valve timing change angel axis is less affected by the value of the revolution radius of the camshaft axis.Using AVL EXCITE Timing Driving software,this paper carries out kinematics and dynamic simulation analysis of the above EVVTL institutions.It's found that the original body fullness coefficient is too low,the spring margin is not enough,there is a rebound valve closed phenomenon.After optimization design,for the newly designed mechanism,the fullness coefficient of the intake valve opening phase reached 0.5611,the fullness coefficient of the intake valve closing phase reached 0.5571,and the force between the components is good.A 1.3L naturally aspirated engine is used as a prototype to build the GT-POWER model and the above model is verified according to the test results.The EVVTL mechanism is simulated and analyzed according to the calibrated GT-POWER model.The simulation results of EVVTL are compared with those of the prototype.The results show that the torque value of EVVTL is increased by 40.1%at 750r/min and the torque value of EVVTL is increased by 20%at 1500r/min.When the load is 2 bar,the specific fuel consumption of the EVVTL mechanism is 11.3%lower than that of the prototype at 750r/min and 6%lower than that of the prototype at 1000r/min.According to the theoretical analysis,for the EVVTL institutions,when the piston goes down,and the cylinder pressure expands to the pressure of the inlet,the intake valve opens,which can minimize the pumping loss.