Abstract: High speed solenoid is a key component of electronically controlled diesel fuel injection system. Accurate evaluation of the solenoid closure time has direct influence on the control precision of both injection timing and quantity. The electronically controlled combination pump solenoid is taken as the research object. A solenoid mechanism model composed of dynamic models of magnetic circuit, electric circuit and spool is built for the research of the solenoid closing process. The electric circuit driving logic suitable for detecting the solenoid closure instant is designed by utilizing the mutation characteristic of magnetoresistance change rate before and after the solenoid closure, so that the solenoid driving current curve shows an obvious turning point. On this basis, the start point recognition algorithm, through the monitoring on driving current, extracts in real time the information on solenoid closure instant. Based on the information, the fuel injection control strategy carries out real-time feedback control on the fuel injection, corrects the actual solenoid control timing and pulse width, so as to eliminate injection variance caused by the solenoid characteristic. The test result shows that the improved circuit driving logic can make the solenoid closure start-point show the characteristic clearly on its driving current. Based on this, the start-point recognition algorithm can accurately detect the solenoid closure instant, and in coordination with the feedback control strategy, can solve the problem of uneven fuel injection from the cylinders, thus improving the control precision of fuel injection.

Key words: Diesel engine, Electronically controlled combination pump, Injection feedback control, Solenoid valve closure start-point