电液式可变气门系统的仿真与实验优化

Simulation and Experimental Optimization for Electro-hydraulic Variable Valve System

利用AMESIM软件建立电液可变气门机构模型,以研究关键参数如电磁阀特性、液压缸直径、供油压力、油泵流量、蓄能器容积和进回油管直径等对气门升程特性的影响,结果表明,液压缸直径与进回油管直径存在最优值,分别为16和6mm。在此基础上建造了电液可变气门系统试验平台,对气门落座速度进行优化。结果表明,采用多脉冲信号控制使落座速度由1.43降至0.82m/s时,其所对应发动机转速由2 370降至1 497r/min,难以满足要求。利用单向节流阀进行节流可以使落座速度降至0.3m/s,但因回落过程一直存在节流损失,回落时间较长,与此对应发动机转速为1 130r/min。采用开关电磁阀与单向节流阀并联策略,可在有效降低落座速度的同时,缩短气门回落时间,在供油压力为15MPa,落座速度为0.3m/s条件下,该系统可满足柴油机2 500r/min工况的需求。

A model for electro-hydraulic variable valve mechanism is built with AMESIM software to investigate the effects of key parameters such as solenoid valve characteristic,hydraulic cylinder diameter,oil pressure,oil pump flow rate,accumulator volume and oil pipe diameter on valve lift characteristics. The results show that the diameters of hydraulic cylinder and oil pipes both have the optimal values of 16 mm and 6 mm respectively. Then on this basis,a test platform for electro-hydraulic variable valve timing system is constructed to optimize the valve seating velocity by experiments. The results indicate that though multiple pulse signal control can lower the valve seating velocity from 1. 43 to 0. 82 m / s,but the corresponding engine speed is also decreased from 2 370 to 1 497 r / min,not being able to meet the requirements. Using one-way valve to throttle the air flow can reduce valve seating velocity to0. 3m / s,but it takes a long time for valve to fall back due to throttling losses and the corresponding engine speed is1 130 r / min. However,the one-way throttle valve connected in parallel with an electromagnetic switching valve can effectively reduce the valve seating velocity meanwhile with the fall-back time of valve shortened. Finally the system can meet the requirements of diesel engine working condition at 2 500 r / min with a valve seating velocity of 0. 3m / s and an oil pressure of 15 MPa.