可变气门驱动机构电磁阀驱动波形设计

Driving Waveform Design of Variable Valve Actuation Solenoid Valve

基于磁场基尔霍夫定律,分析了电磁铁电流变化率随气隙的变化规律,结论表明气隙最小时电流变化率激增,在电流波形上有明显的突变特征点;开关电磁阀通常采用Peak&Hold电流驱动波形,保证电磁阀快速落座的同时降低能耗,在此基础上,可变气门驱动机构(VVA)电磁阀驱动电流采用"闭环-开环-闭环"的设计思路,电流达到峰值之后采用固定占空比的脉宽调制(PWM)波控制,从而电流波形会出现明显的拐点;VVA电磁阀的动态试验结果表明,电流波形上拐点与电磁阀落座的时刻完全一致,因此电控单元(ECU)通过对该点的检测判断,可以将驱动电流作为检测电磁阀落座时刻的传感器使用。

Based on Kirchhoff Voltage law,the relationship between the electric current change rate and electromagnet air gap is analyzed.The result shows that current change rate will increase sharply when air gap reaches the minimum value. A remarkable feature point will be found on the current waveform. The switch electromagnetic valve is usually controlled through Peak Hold current waveform,which guarantees solenoid valve closing quickly and reduces power consumption at the same time. Design scheme of＂Closed loop-open loop-closed loop＂is adopted on VVA solenoid valve. Constant duty ratio PWM voltage controls the waveform after the current reaching the peak value. And then inflection point appears on current waveform. Finally,the result of VVA solenoid valve dynamic test indicates that the moment of valve closing coincide exactly with the feature point appears,so the current waveform can be used to identify the valve closing point.