A Novel Closed Loop Control based on Ionization Current in Combustion Cycle at Cold Start in a GDI Engine

As the invalidation of the oxygen sensor in the initial cycles at cold start, the engine can not operate based on the closed loop control based on oxygen sensor. And it may result in the misfire events and higher hydrocarbon (HC) emissions during this period. To solve this problem, a novel closed loop control based on ionization current in combustion cycle is proposed. The in-cylinder combustion quality is monitored by means of the ion current detection technique; meanwhile, if the misfire event is detected in the combustion cycle, the spark re-ignition is made in the current combustion cycle. In addition, to optimize the combustion and reduce HC emissions during cold start, the fuel injection quantity and ignition timing in the next cycle are adjusted based on the current ion current signal. The results show that, it is feasible that the closed loop control in current combustion cycle based on ion current of gasoline direct injection (GDI) engine at cold start is completed by means of the ionization detection technique. Also, the combustion process is optimized, resulting in the decrease both in misfire events and engine-out HC emissions.