基于发动机配气机构的液压可变气门驱动系统研究

Research on Hydraulic Variable Valve Driving System Based on Engine Valve Mechanism

为提高气门开启和关闭反应速度,降低气门升程实际输出误差,采用液压可变气门驱动系统,并对跟踪效果进行仿真验证。创建发动机气门系统简图模型,根据牛顿第二定律推导出活塞动力学方程式;对无凸轮气门机构进行改进,设计新型液压可变气门驱动系统,利用旋转阀打开和关闭液压缸和高、低压液压源之间的流动连接,从而控制液压缸的进油和出油。设计了2个反馈PID控制器,用于精确控制气门开启和关闭正时以及气门升程。采用MATLAB软件对气门开启和关闭角度及气门升程进行仿真,并与改进前进行比较。结果表明:改进前,发动机气门开启和关闭角度突然变化时,波动幅度较大,控制系统反应速度较慢,气门升程跟踪误差较大;改进后,发动机气门开启和关闭角度突然变化时,波动幅度较小,控制系统反应速度较快,气门升程跟踪误差较小。采用液压可变气门驱动系统,可以提高气门正时和升程的灵活性,控制系统输出精度较高,效果较好。

In order to improve the reaction speed of the valve opening and closing and reduce the actual output error of valve lift,a hydraulic variable valve driving system was adopted,and the tracking effect was simulated and verified.A sketch model of engine valve system was established.According to Newton’s second law,the dynamic equation of the piston was deduced.The camless valve mechanism was improved,and a new hydraulic variable valve driving system was designed.The flow connection between the hydraulic cylinder and the high and low pressure hydraulic source was opened and closed by the rotary valve,so the inlet and outlet of the hydraulic cylinder were controlled.Two feedback PID controllers are designed to precisely control valve opening and closing timing and valve lift.The valve opening and closing angle and valve lift were simulated by using MATLAB software,and compared with those before improvement.The results show that before the improvement,when the valve opening and closing angles suddenly change,the fluctuation range is larger,the response speed of the control system is slower,and the tracking error of valve lift is larger;after the improvement,when the valve opening and closing angles suddenly change,the fluctuation range is smaller,the response speed of the control system is faster,and the tracking error of valve lift is smaller.Adopting hydraulic variable valve driving system,the flexibility of valve timing and lift is improved,the output precision of control system is higher,and the effect is better,the output precision of the control system is higher and the effect is better.