Study On Fully Variable Hydraulic Valve Mechanism Of Engine

In today’s world,energy and environment problems are increasingly prominent.Therefore,energy saving and emission reduction has become the main direction of traditional engine development.As an important part of engine energy saving technology,variable valve technology has been widely studied in automobile field.Especially the fully variable valve technology,because it can realize the valve lift,valve timing and continuous variable opening duration,more favored by researchers.The fully variable valve technology can adjust the intake through different valve lift curves,so that the throttle can be abandoned and the pump air loss can be greatly reduced under low and medium load.Based on this,this paper designs a fully variable valve mechanism controlled by machinery and hydraulic pressure.The mechanism realizes the valve lift and the valve closing time variable by rotating the fork to change the oil discharge time.In this paper,the motion law of valve and the performance of fully variable valve engine are studied by simulation.The main research contents are as follows:First of all,this paper introduces the working process and working principle of the fully variable valve mechanism.The mechanism drives the piston to compress the hydraulic oil through the cam,thus promoting the valve piston to drive the valve assembly motion.The valve is closed by rotating the fork to control the oil discharge time and the valve is seated smoothly by throttling.Secondly,by analyzing the concrete structure of the fully variable valve mechanism,the kinematic differential equation and fluid continuity equation of the mechanism are listed,and the dynamic relation of the mechanism is clarified.Based on this,the AMESim dynamic simulation model of the mechanism is established.The parameters of each sub-module in the model are set.In the simulation,the effects of different structure parameters and operation parameters on the valve motion are analyzed.Finally,the performance simulation software GT-Power verifies that the fully variable valve engine can realize the adjustment of different charging coefficients,and compares the pump gas loss,power and fuel consumption between the fully variable valve engine and the original engine.The simulation results show that the fully variable valve mechanism designed in this paper can achieve continuous variable valve lift and valve closing time by changing the oil discharge angle.The engine charge coefficient controlled by the mechanism can be adjusted continuously,which verifies that the fully variable valve mechanism can replace the throttle to adjust the intake.The simulation results show that the fully variable valve engine greatly reduces the pump loss under low and medium load,and the power and torque of the fully variable valve engine are slightly larger than that of the original engine,and the fuel consumption is lower than that of the original engine under the premise of equal charge coefficient and speed.Especially at low loads(power 0.85 kw,speed 2000 r/min,power 2.32 kw,speed 4000 r/min),the fuel consumption is reduced by 12.44% and 11.84%.It can be seen that the fully variable valve engine has good fuel economy,and the power performance is also slightly improved.