Development And Performance Study Of Full Variable Valve Timing System Powered By Electronic Hydraulic System

Energy and environment protection are the most austere challenges Confronted to the humankind in the 21st century."Energy thrift and environment protection"have become the prime developing strategy all over the world. As the development of automobile industry, that the car amount raises greatly imposes great pressure on environmental protection and energy and this further lead to the improvement of more strict emission legislation since 1970s in the world .Thrift energy and control the poisonous gases emission have been the prime developing direction in the internal-combustion engine (ICE).The valve system is an important part of the engine and its performance has much effect on the ICE performance. Traditional engine's cam valve timing is fixed and the valve timing is determined through varied valve timing experiments with consideration of others operation conditions. Because it's valve timing is fixed and can not adjust during working condition. Therefore engine capability is difficult to be the best working condition under varied operation conditions. Along with the request of the fuel economy and lower harmful emissions become more and more strict, the traditional valve system is hardly meet these requests.Full variable valve timing system without cam has been paid much attention as the fast development of electronics technology. The system can realize the adjustment of the valve timing, valve lift, valve open period and other parameters according to the respective operation conditions .And these further lead to the improvement of the ICE performance.By analyzing and comparing several kinds of domestic and international advanced electronically controlled variable valve system , A full variable valvetiming system powered by electronic hydraulic system were developed based on ZS1105 single cylinder diesel engine without any modifications to substitute the traditional valve timing system. This system is made up of hydraulic power system, valve actuator and corresponding control system. In this system, pressed oil is used as the working medium. The operation of the valve is drove by the pressure of the oil cylinder which is controlled by electromagnetism valve. When the electromagnetism valve connects the pipeline between oil cylinder and intake vitta, the high pressure oil enters into the oil cylinder and the pressure raises to overcome the valve resistance and the valve opens. when the electromagnetism valve cut the pipeline between oil cylinder and intake vitta and connects the pipeline between oil cylinder and low -pressure vitta ,then the valve spring drive the valve go back and push the oil out of the oil cylinder and the valve close .The design of this system were introduced in this paper in detail , including the hydraulic pressure pump, accumulator and valve actuator and so on .It contain the how to select the hydraulic pressure pump,accumulator and electromagnetism valve of hydraulically actuating, the design of parts of electronically controlled variable valve actuator and the design of soft hardware of control system . According to the work of the team, an experimental engine is set up which fueled with ethanol. The originally valve system were canceled and the Electro-Hydraulic variable valve timing system was equipped on the cylinder head .The compress ratio is dropped to11.8 according to the physics and chemistry characteristic of ethanol The fuel system is changed to electric control inject system .An electricity control ignition system was equipped on the engine and provide the basis of future work.The performance experiments of the system indicate that the valve timing ,valve duration and lift can be controlled in real time and the full variable valve timing system shows great stability and credibility .so the anticipative aim has been attained .By the research toward the system dynamic state characteristic ,The impact of some parameters on the system dynamics were determined through investigation of system dynamics and The shock when the valve closes were solved and the problems needed to solve further were elaborated and the corresponding fixing methods were also put forward.The following conclusions can be made according to the experimental results.1 There is delay during the operation because of the working medium transmission and the response of the electromagnetism valve when the corresponding instructions were send to execute the actions of valve opening and closure, the delay time is fixed, hence, the delay can be compensated to improve the operation precision when the system operates in ICE .2 The valve displacement profile which controlled by Electro-Hydraulic variable valve timing has a better area of circulate section than quondam engine. so the engine equipped Electro-Hydraulic variable valve timing system has a larger potential in improving the combustion,dynamic and so on.3 The system is credible and stable and can meet the engine requests under different operation conditions, so the design of the system attain the request.4 The speed and lift of the valve can be changed by controlling the drive of the hydraulic pressure system.5 The system can control the valve timing and duration continually.The phenomenon of valve return after arriving the maximum lift exists during the operation of the valve. So the problems need to be solved in the future work. And the corresponding resolutions were elaborated in this paper in detail to provide directions to solve the existing problems further.