Patent ID: 10125708

Abstract:
An air-fuel ratio control device switches a target air-fuel ratio from a lean set air-fuel ratio to a rich set air-fuel ratio after judging that an air-fuel ratio of an outflowing exhaust gas has become a stoichiometric air-fuel ratio and an oxygen storage amount of an exhaust purification catalyst has become a switching reference storage amount, and makes an average value of the target air-fuel ratio the stoichiometric air-fuel ratio to less than the lean set air-fuel ratio, from after the estimated value of the oxygen storage amount has become the switching reference storage amount or more until judging that the air-fuel ratio of the outflowing exhaust gas has become the stoichiometric air-fuel ratio if the estimated value of the oxygen storage amount becomes the switching reference storage amount or more before judging that the air-fuel ratio of the outflowing exhaust gas has become the stoichiometric air-fuel ratio.