EXHAUST EMISSION CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To improve fuel consumption by controlling temperature rise of a catalyst suitable for an operation state and reducing fuel to be added by executing S poisoning recovery of an NOX catalyst when intake air quantity is little at the time of speed reduction or at the time of idling. SOLUTION: This device is provided with the catalyst 4 for purifying exhaust, an engine operation state detection means 15 for detecting an engine operation state of an internal combustion engine 1, a plurality of catalyst temperature raising means for raising the temperature of the catalyst 4 and a catalyst temperature rise selection means 11 for selecting one of the plurality of catalyst temperature raising means based on a detected value of the engine operation state detection means 15 when the temperature of the catalyst 4 is raised. The catalyst temperature raising means increases main injection of fuel supplied to the internal combustion engine 1, makes an air-fuel ratio close to a theoretical air-fuel ratio and adds fuel to an exhaust passage 3 in a small load area, injects additional fuel after the main injection and adds fuel in the exhaust passage 3 in a middle load area and adds fuel to the exhaust passage 3 in a large load area.