Based on the requirements of improving fuel economy ,the traditional Otto-cycle engine was changed into Atkinson-cycle engine .The design of valve train mechanism was very important for cycle modification .The model of valve train mechanism for gasoline engine was built ,the kinematics and dynamics analysis were conducted ,the cam profile was optimized and the valve timing was rede-signed .By using DVVT of intake and exhaust camshaft ,the optimal control design of DVVT for the optimized engine was conducted under different loads and speeds .Finally ,the bench test results showed that the modification of engine cycle was successful .The opti-mal specific fuel consumption of original engine decreased from 250 g/(kW · h) to 232 g/(kW · h) and low fuel consumption area moved to the normal working area of the engine ,which verified the accuracy and effectiveness of the design method of valve train .%基于发动机燃油经济性升级需求,将传统的Otto循环发动机改为阿特金森(Atkinson)循环发动机,其中,配气机构的改进是完成循环改型的关键.对某汽油机配气机构建立模型,并进行运动学和动力学计算分析,进而对凸轮型线进行优化设计,对配气正时进行再设计研究.利用进排气凸轮轴的双VVT机构,在不同转速和负荷下对改型后的发动机进行了双VVT的优化控制设计.台架试验结果表明,发动机成功地完成了Atkinson循环的转换,最低燃油消耗率由原机的250 g/(kW·h)降低到232 g/(kW·h),且低油耗区向常用发动机工况移动,验证了配气机构设计方法的正确性和有效性.
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