Air-fuel ratio control apparatus and method for internal combustion engine

摘要

In air-fuel ratio control apparatus and method for an internal combustion engine having an EGR valve interposed in an EGR passage between an intake manifold and an exhaust manifold, a target EGR quantity is calculated, a determination is made which of air-fuel ratio feedback controls through an EGR control and through an intake-air quantity is to be executed according to the target EGR quantity, and one of the air-fuel ratio feedback controls is selectively made according to a result of a determination of which of the air-fuel feedback controls is to be executed. During an execution of a rich spike control, the feedback control through the intake-air quantity control is unconditionally executed.