US Patent 7302941 Air-fuel ratio control apparatus for internal combustion engine

An air-fuel ratio control apparatus for an internal combustion engine according to the invention includes a control unit that makes a correction to the fuel injection amount using the air-fuel ratio learned value when calculating the fuel injection amount, and that changes the guard value that places a limitation on the degree of correction to the fuel injection amount made by using the air-fuel ratio learned value, based on the degree to which lubricating oil has been diluted with fuel.