A control system for an internal combustion engine, which is capable of optimally controlling fuel injection by an injector even in a transient state of the engine. An ECU 2 of the engine provided with an EGR system (14) controls the amount (Fa) of air drawn into cylinders (3a) via an intake system (4). An air flow sensor (27) detects the intake air amount (Fa). The ECU 2 estimates a flow rate (Fe_hat) of EGR gases according to response delay of recirculation of the EGR gases by the EGR system (14), estimates the amount (mo2) of oxygen existing in the cylinder (3a), based on the detected intake air amount (Fa) and the estimated flow rate (Fe_hat) of the EGR gases, determines a fuel injection parameter (Q*) based on the engine speed (Ne) and the estimated in-cylinder oxygen amount (mo2), and controls an injector (6) based on the determined fuel injection parameter (Q*).
Shizuo Sasaki; Junmin Wang; Gary D. Neely