Exhaust gas recirculation control system for internal combustion engines

摘要

An exhaust gas recirculation control system for an internal combustion engine includes an exhaust gas recirculation passage extending between the intake system of the engine and the exhaust system thereof, and an exhaust gas recirculation control valve for controlling the flow rate of exhaust gases to be recirculated through the exhaust gas recirculation passage. The system further includes an ECU which calculates a desired air-fuel ratio of a mixture supplied to the engine, based on engine operating conditions detected by engine operating parameter sensors, and also a desired valve opening of the exhaust gas recirculation control valve, based on engine operating conditions detected by the operating parameter sensors and the calculated desired air-fuel ratio. The ECU modifies the calculated desired valve opening by a first predetermined amount, and starts the controlling of the flow rate of exhaust gases to be recirculated by the exhaust gas recirculation control valve, by the use of the modified desired valve opening, when it is determined that the desired air-fuel ratio has been changed from a lean state to a rich state or vice versa.