Patent ID: 7707822

Claim:
A control apparatus for an internal combustion engine comprising: an air-fuel ratio detection means for estimating or measuring a cylinder air-fuel ratio of each cylinder on the basis of an output of an air-fuel ratio sensor detecting an air-fuel ratio of exhaust gas of the internal combustion engine; a catalyst disposed downstream of the air-fuel ratio sensor and cleaning the exhaust gas; an abnormal cylinder determination means for determining on the basis of the cylinder air-fuel ratio whether an abnormal cylinder in which an air-fuel ratio is abnormal exists; a catalyst overheat determination means for determining whether the catalyst is likely to be overheated when the abnormal cylinder determination means determines that the abnormal cylinder exists; and a catalyst overheat prevention means for controlling an air-fuel ratio of a normal cylinder other than the abnormal cylinder in such a way that an air-fuel ratio of the exhaust gas flowing into the catalyst becomes close to a stoichiometric air-fuel ratio or a rich air-fuel ratio when the catalyst overheat determination means determines that the catalyst is likely to be overheated, wherein the catalyst overheat determination means determines that the catalyst is likely to be overheated when an air-fuel ratio of the abnormal cylinder is lean.