Patent ID: 7159388

Claim:
An air-fuel ratio control device for an internal-combustion engine, the air-fuel ratio control device comprising: a catalyst positioned in an exhaust path of the internal combustion engine; an upstream exhaust gas sensor positioned upstream of said catalyst; a downstream exhaust gas sensor positioned downstream of said catalyst; main feedback means for feeding back the output of said upstream exhaust gas sensor to fuel injection quantity so that the air-fuel ratio of an exhaust gas flowing into said catalyst coincides with a target air-fuel ratio; sub-feedback means for feeding back the output of said downstream exhaust gas sensor to the fuel injection quantity so that the air-fuel ratio of an exhaust gas flowing out of said catalyst coincides with a theoretical air-fuel ratio; intake air quantity detection means for detecting the intake air quantity of the internal-combustion engine; and injection quantity correction means for correcting the fuel injection quantity to always ensure that the larger said intake air quantity becomes, the richer the air-fuel ratio of an exhaust gas flowing into said catalyst is.