Patent ID: 7201138

Claim:
A control system for an internal combustion engine having fuel injection means provided in a combustion chamber of the engine for injecting fuel into the combustion chamber, and an exhaust gas recirculation mechanism for recirculating exhaust gases of the engine to an intake system of the engine, the control system comprising: operating condition detecting means for detecting an operating condition of the engine; fuel injection control means for determining a fuel injection timing according to the detected engine operating condition, and executing a fuel injection through the fuel injection means; ignition timing storing means for storing at least one target compression ignition timing of the fuel injected into the combustion chamber, each target compression ignition timing being set according to the operating condition of the engine; ignition timing detecting means for detecting an actual compression ignition timing of the fuel injected into the combustion chamber; cetane number estimating means for calculating an ignition delay of the actual compression ignition timing with respect to the target compression ignition timing, and estimating a cetane number of the fuel according to the calculated ignition delay; exhaust gas recirculation control value storing means for storing control values of a recirculation amount of exhaust gases through the exhaust gas recirculation mechanism, the control values being set according to the operating condition of the engine; exhaust gas recirculation control means for retrieving the control value stored in the exhaust gas recirculation control value storing means according to the detected engine operating condition, and controlling the recirculation amount of exhaust gases using the retrieved control value; and correcting means for calculating a correction amount of the recirculation amount of exhaust gases according to the estimated cetane number, and correcting the control value retrieved from the exhaust gas recirculation control value storing means, wherein the exhaust gas recirculation control means controls the recirculation amount of exhaust gases using the control value corrected by the correcting means.