| 摘要 |
A control apparatus for an internal combustion engine includes an upstream air-fuel ratio sensor 66, an upstream catalyst 53, a particulate collection filter 54, a downstream air-fuel ratio sensor 67, and a downstream catalyst 55 successively disposed in an exhaust passage of an internal combustion engine 10 from the upstream side toward the downstream side. In a period after completion of fuel cut operation, the control apparatus controls the averaged air-fuel ratio of the engine to a first air-fuel ratio which falls within a window of the downstream catalyst 55 and is shifted toward the rich side from the stoichiometric air-fuel ratio. When the downstream catalyst is determined to have reached a reduced state in which the downstream catalyst can remove a predetermined amount of nitrogen oxides, the control apparatus controls the averaged air-fuel ratio of the engine to a second air-fuel ratio shifted toward the lean side from the stoichiometric air-fuel ratio. With this operation, oxygen is supplied to the particulate collection filter, whereby particulates therein are burned, and nitrogen oxides are removed by the downstream catalyst.
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