INTERNAL COMBUSTION ENGINE

摘要

An internal combustion engine comprises an upstream side air-fuel ratio sensor, a downstream side air-fuel ratio sensor, an air-fuel ratio control means, a learning means and an abnormality judging means. When the air-fuel ratio control means sets the target air-fuel ratio to a first side of a rich side or a lean side, if it is judged that the air-fuel ratio of the outflowing exhaust gas is maintained at a second side at an opposite side to the first side for a predetermined air-fuel ratio maintenance judgment time or more, the learning means corrects a parameter relating to the feedback control so that the air-fuel ratio of the inflowing exhaust gas changes to the first side. A correction amount of the parameter at the stuck learning is made small when the abnormality judging means judges that the downstream side air-fuel ratio sensor exhibits abnormal response delay.

主权项

1. An internal combustion engine comprising:
an exhaust purification catalyst arranged in an exhaust passage and able to store oxygen, an upstream side air-fuel ratio sensor arranged at an upstream side of the exhaust purification catalyst in a direction of exhaust flow and detecting an air-fuel ratio of inflowing exhaust gas flowing into the exhaust purification catalyst, a downstream side air-fuel ratio sensor arranged at a downstream side of the exhaust purification catalyst in the direction of exhaust flow and detecting an air-fuel ratio of outflowing exhaust gas flowing out from the exhaust purification catalyst, an air-fuel ratio control means for setting a target air-fuel ratio of the inflowing exhaust gas and controlling by feedback an amount of fuel fed to a combustion chamber so that an air-fuel ratio detected by the upstream side air-fuel ratio sensor matches the target air-fuel ratio, a learning means for correcting a parameter relating to the feedback control based on the air-fuel ratio detected by the downstream side air-fuel ratio sensor so that a deviation in the feedback control between the target air-fuel ratio and an actual air-fuel ratio of the inflowing exhaust gas becomes small, and an abnormality judging means for judging if the downstream side air-fuel ratio sensor exhibits abnormal response delay, wherein when the air-fuel ratio control means sets the target air-fuel ratio to a first side of either of a rich side and lean side from a stoichiometric air-fuel ratio, if it is judged that the air-fuel ratio of the outflowing exhaust gas is maintained at a second side at an opposite side to the first side from the stoichiometric air-fuel ratio for a predetermined air-fuel ratio maintenance judgment time or more, the learning means corrects a parameter so that the actual air-fuel ratio of the inflowing exhaust gas changes to the first side as stuck learning, and a correction amount of the parameter at the stuck learning when the abnormality judging means judges that the downstream side air-fuel ratio sensor exhibits abnormal response delay is made smaller than a correction amount of the parameter in the stuck learning when it judges that the downstream side air-fuel ratio sensor does not exhibit abnormal response delay.