Air-fuel ratio control system for internal combustion engine

摘要

An air-fuel ratio control system for an internal combustion engine (8) is comprised of an engine condition detecting unit (16, 17, 18, 19, 21, 31, 41) and a control unit (20). The control unit is arranged to calculate a target engine torque on the basis of an engine operating condition, to calculate a target EGR ratio, a target excess air ratio and a target intake air quantity on the basis of the engine operating condition and the target engine torque, to calculate a target equivalence ratio on the basis of the target EGR ratio and the target excess air ratio, to calculate a target injection quantity on the basis of the engine operating condition and the target equivalence ratio, and to control an air-fuel ratio by bringing a real intake air quantity to the target intake air quantity and by bringing a real fuel injection quantity to the target fuel injection quantity.