The Design Of Cam-driven Hydraulic Variable Valve Actuation Mechanism

With the vigorous development of China’s automobile market, the car ownership is continued to increase, more and more people pay attention to the environmental pollution and energy crisis. Because the traditional gasoline engine valve open and close time and valve lift is fixed,the pumping loss is greater and the fuel economy is poor, and the variable valve actuation(VVA)technology has been known as an effective gasoline-saving technology, the VVA can change the valve open and close timing and the valve lift, so it can make the gasoline engine in different conditions achieve the optimal intake efficiency, thereby increasing the thermal efficiency of gasoline engines, reducing fuel consumption and improving emissions performance.Due to the huge advantages of variable valve actuation technology, it has become a hot topic of gasoline energy-saving technologies. In the foreign country, the patents of variable valve actuation had been applied in early 1880, and after the 1990 s, due to the demands of fuel economy of increased and increasingly stringent emissions regulations, variable valve actuation technology has been tremendous developed, many research institutions and automobile manufacturers had launched their respective products and services. Based on this, we use a Suzuki GS125 gasoline engine as a trial prototype, design and develop cam-driven hydraulic variable valve actuation mechanism, which enables the valve lift and valve closing time variable, and by building an engine test bench to verify the cam-driven hydraulic variable valve actuation mechanism is feasible and effective. The main work and conclusions are as follows:(1) This paper analyzes the trends of variable valve actuation technology and the research status at home and abroad, and we propose cam-driven hydraulic variable valve actuation mechanism, namely increasing the hydraulic system in the traditional gasoline engine,which uses the method of cam-driven and electro-hydraulic-driven combine to control the movement of the valve, and it can improve the response characteristic of the valve mechanism; and the design of seated buffer mechanism can optimize the valve seating velocity.(2) By using AMESim simulation software to build a physical model of the cam-driven hydraulic variable valve actuation mechanism, and analyzes the parameters of the various parts of mathematical. And analyzes hydraulic piston group, low pressure oil by the software, and also select and set parameter, and debug the valve seating buffer module.(3) Through the model build by the AMESim simulation software, we can get the valve lift and valve seating velocity image of different open pressures of electro-hydraulic proportional relief valve and different gasoline engine speed.(4) Suzuki GS125 gasoline engine as a prototype trial, the gasoline engine valve cover is modified, and cancel intake valve rocker arm and the rocker arm shaft and its related parts of the original machine, and design and process tappet, hydraulic piston and other components.(5) Set up the cam drive hydraulic variable valve actuation gasoline engine test bench, and carry experiment by the test bench, the measured gasoline engine speed is 2000 r / min, electro-hydraulic proportional relief valve opening pressure is 4, 4.5, 5, 5.5,6,10 MPa,and we can get the valve lift curve image, and is compared with valve lift curve image obtained by simulation software AMESim, in order to verify the feasible and effective of the design of the cam-driven hydraulic variable valve actuation mechanism.