Control system for engine

A control system for an engine, comprising:

• an engine body formed with a cylinder;
• a NOx catalyst provided in an exhaust passage through which exhaust gas discharged from the engine body flows, and configured to store NOx within the exhaust gas when an air-fuel ratio of the exhaust gas is lean, and reduce and release the stored NOx when the air-fuel ratio of the exhaust gas is close to a stoichiometric air-fuel ratio or rich;
• an oxidation catalyst provided integrally with the NOx catalyst or in the exhaust passage upstream of the NOx catalyst and configured to oxidize unburned fuel within the exhaust gas;
• a particulate matter (PM) filter provided in the exhaust passage downstream of the oxidation catalyst and configured to capture particulate matter within the exhaust gas;
• a fuel injector configured to perform a main injection in which fuel is injected into the cylinder to obtain an engine torque and a post injection in which fuel is injected into the cylinder at a timing later than the main injection;
• and
• a controller including a processor configured to execute:
• a DeNOx control in which the fuel injector is controlled to perform the main injection and the post injection so that the air-fuel ratio of the exhaust gas is brought close to the stoichiometric air-fuel ratio or becomes rich and the fuel supplied into the cylinder by the post injection combusts therein, and
• a filter regenerating control in which the fuel injector is controlled to perform the main injection and the post injection so that the air-fuel ratio of the exhaust gas becomes lean and the fuel supplied into the cylinder by the post injection causes no combustion therein, the controller executing the DeNOx control and the filter regenerating control consecutively in this order.