Patent ID: 8297266

Claim:
A control apparatus for an internal combustion engine, comprising: a fuel supply device for supplying fuel in a fuel tank to the internal combustion engine; air-fuel ratio detecting means that is set in an exhaust system of the internal combustion engine, for detecting an air-fuel ratio in exhaust gas from the internal combustion engine; air-fuel ratio correction amount calculating means for calculating, based on a detection value of the air-fuel ratio detecting means, an air-fuel ratio correction amount for correcting a fuel injection amount to the internal combustion engine; concentration estimating means for calculating a concentration estimation value of a single composition of the fuel based on the air-fuel ratio correction amount calculated by the air-fuel ratio correction amount calculating means; and fuel injection amount calculating means for correcting the fuel injection amount based on the air-fuel ratio correction amount and the concentration estimation value, wherein the concentration estimating means comprises: fueling determining means for detecting that the fuel has been supplied to the fuel tank; concentration change period setting means for starting a concentration change period when it is determined by the fueling determining means that fueling has been performed and the fueling is in a period other than the concentration change period, and ending the concentration change period when an integrated fuel injection amount after start of the concentration change period reaches a first determination value; concentration change period extending means for increasing, when it is determined by the fueling determining means that the fueling has been performed and the fueling is in the concentration change period, the first determination value by an integrated fuel injection amount from a start time point of the concentration change period until a time point when it is determined that the fueling has been performed; and concentration update permitting means for permitting concentration update in the concentration change period; and the concentration estimating means extends a concentration estimation period when it is determined that refueling has been performed during concentration change.