AIR-FUEL RATIO CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE

PROBLEM TO BE SOLVED: To rapidly converge an air-fuel ratio on a stoichiometric air-fuel ratio after switching the operating state of an internal combustion engine from transient operation to steady operation. SOLUTION: An air-fuel ratio control device for an internal combustion engine is provided with a catalytic converter 12, a catalyst upper reaches side O2 sensor 13, a lower reaches side O2 sensor 15, a main air-fuel ratio control means for increasing/decreasing the value of an air-fuel ratio correction factor FAF on the basis of a detection value of the upper reaches side O2 sensor 13, and an auxiliary air-fuel ratio control means for increasing/decreasing the value of skip quantities RSR, RSL concerned in an air-fuel ratio correction factor FAF, on the basis of the detection value of the lower reaches side O2 sensor 15. At the time of switching from steady operation where main and auxiliary air-fuel ratio control are executed to transient operation where only main air-fuel ratio control is executed, a value of the skip quantities RSR, RSL is increased/decreased to the specified value, and succeedingly at the time of switching from transient operation to steady operation, the value of the skip quantities RSR, RSL is made the value of the skip quantities RSR, RSL immediately before switching from steady operation to transient operation.