可变气门正时机构特殊模式控制策略的仿真研究

Simulative study of control strategy of special modes for the mechanism of variable valve timing

针对发动机可变气门正时(variable valve timing,VVT)控制系统凸轮轴调节过程中可能出现的特殊工作模式,文章建立了相应的控制策略,并计算对应的凸轮轴目标相位。当机油温度过高、发动机转速下降太快导致机油压力降低时,为了防止凸轮轴调节速度明显降低,提出停调排气凸轮轴的控制策略;为了预防发动机工作中产生的碎屑阻塞相位器和机油控制阀,提出预防性清洗策略;根据这2种控制策略对凸轮轴调节效果的影响,对其进行了优先级划分。在ASCET-MD环境中建立了控制模型,通过仿真实验验证了控制逻辑,结果表明,凸轮轴目标位置完全适合相应的控制策略。

For some special operating modes that may occur during the adjustment of camshaft in the engine with variable valve timing（VVT）, the corresponding control systems are established and the corresponding target positions are calculated. Low oil pressure may occur when the oil temperature is too high and the engine speed drops too quickly, and in order to prevent the adjustment rate of cam- shaft dropping too significantly, the strategy of stopping the adjustment of exhaust camshaft is established; in order to prevent the dirt deposits generated in the engine blocking the camshaft phaser and oil control valve, the strategy of preventive cleaning is established; then the two control strategies are prioritized based on their effects on the adjustment of camshaft. Finally, the models of control systems are established and some simulation experiments are done in ASCET-MD. The experimental results verify the control logic and indicate that the target positions of camshaft are completely fit for the corresponding control strategy.