| With the development of automobile industry,increasing environmental pollution and reducing oil resources become a must face the problem.To develop high efficiency,low energy consumption and low emission engine technology is very important.Recent research has been found technology of Variable Valve Timing is an effective measure to improve the economy and emission of the engine.The intake state parameters of the engine can be affected by valve timing which can affect the combustion process of the engine’s cylinder,resulting in differences of engine performance.The fixed Valve Timing of traditional engine can’t guarantee the performance of economy,power and emission in different conditions,therefore,in order to ensure the engine performance always in the best states,an Electro-Hydraulic Variable Valve System was developed based on a diesel engine,and then establish the test bench so as to study the characteristics of Electro-Hydraulic Variable Valve System.In order to research work characteristics of the electro-hydraulic variable valve more specific,Six working ranges which include solenoid valve open delay(t1),the line delay(t2)caused by different pipe length,valve inertial delay(t3),the time of the hydraulic chamber oil filled(t4),the time of hydraulic chamber oil drainage(t5),solenoid valve close delay(t6)are defined according to the working order of the electro-hydraulic variable valve and analyze the running time and proportion of each interval in one cycle,At the same time the pressure fluctuation of each interval is be researched.Research on the movement of the running time and proportion of each interval in one cycle of the electro-hydraulic variable valve system showe the running time and proportion of the hydraulic chamber oil filled(t4)and the hydraulic chamber oil drainage(t5)are more larger than the other four working ranges,the oil pressure play a critical role in the hydraulic chamber oil filled(t4),with the increase of oil pressure,the time of hydraulic chamber oil filled(t4)gradually is reduced,but the control pulse play a little role in the hydraulic chamber oil filled(t4)and hydraulic chamber oil drainage(t5),with the increase of control pulse,the time of the hydraulic chamber oil filled(t4)and hydraulic chamber oil drainage(t5)do not change significantly.Research on the pressure fluctuation characteristics of each interval of electro-hydraulic variable valve system showe there will be fierce pressure fluctuation in the pipeline when solenoid valve open and the load suddenly changed of hydraulic chamber,the pressure dropping(△P1)is caused by the solenoid valve suddenly open is about 20% of oil pressure;when the acceleration of the hydraulic piston is zero,the hydraulic chamber will appear a sharply pressure rising(△P2)which will affect the pressure fluctuation of the solenoid valve,the moment of the load changed of hydraulic chamber will be brought forward with the rise of oil pressure;the oil pressure play a critical role in the pressure mutation rate(△P/△t)which will be happened when solenoid valve open and the load suddenly changed of hydraulic chamber,with the increase of oil pressure,the pressure mutation rate(△P/△t)gradually is increased,but the control pulse play a little role in the pressure mutation rate(△P/△t),with the increase of control pulse,the amplitude of the pressure mutation rate(△P/△t)do not change significantly.Finally,the evaluation standard which contains two sides are the time about the oil filled and drainage of the hydraulic chamber and the pressure mutation rate of the hydraulic chamber is put forward.By using the GT-power to build the computable mode to research about the influence of structural parameters on the electro-hydraulic variable valve system.The results show that the time of the hydraulic chamber oil filled is mainly decided by the diameter of oil hole,with the increase of the diameter of oil hole,the time of the hydraulic chamber oil filled will be reduced,at the same time,the pressure mutation rate(△P/△t)will be increased;the time of the hydraulic chamber oil drainage is mainly decided by the diameter of hydraulic piston,with the increase of the diameter about hydraulic piston,the time of the hydraulic chamber oil drainage will be increased,especially,when the diameter of hydraulic piston is 50 mm,the oil of the hydraulic chamber unable flow out completely,at the same time,the pressure mutation rate(△P/△t)will be increased also,but the increasing is not obviously.The time of the hydraulic chamber oil filled and hydraulic chamber oil drainage will not change with the increasing speed of the engine,but the maximal displacement of the hydraulic piston will be reduced.the valve spring stiffness(K)and pre-tightening force(F0)play a little role in the hydraulic chamber oil filled and drainage,with the increase of the valve spring stiffness(K)and pre-tightening force(F0),the pressure mutation rate(△P/△t)will be increased firstly then decreased. |
