Patent attributes
A control apparatus for an internal combustion engine prevents variation of an air fuel ratio even upon introduction of purge air. A delay time occurring until the intake air detected, after having arrived at the combustion chamber through a surge tank, influences an air fuel ratio sensor, a delay time occurring until purge air containing evaporated fuel generated upon purging a canister, after having arrived at the combustion chamber through the surge tank, influences the air fuel ratio sensor, and a delay time occurring until fuel supplied by an injector, after having arrived at the combustion chamber, influences the air fuel ratio sensor, are represented by simplified physical models. A purge rate in the combustion chamber or in the neighborhood of the air fuel ratio sensor is calculated by using the physical models, and a purge air concentration and a fuel correction amount are calculated based on the purge rate thus obtained.
