Patent ID: 6324836
Filing Date: 2001-12-04
Classification: F02D

Abstract:
An air-to-fuel ratio control apparatus comprising:a catalyst unit for purifying exhaust gas from an engine;air-to-fuel ratio-detection means for detecting at least an air-to-fuel ratio downstream of said catalyst unit;first control means for controlling at least one of an amount of fuel and an amount of air to be fed to said engine by using a feed-back control based on at least one of air-to-fuel ratios upstream of, downstream of, and in said catalyst unit; andsecond control means for controlling an air-to-fuel ratio upstream of said catalyst unit so as to be within a predetermined purification-efficiency range after over-correcting said air-to-fuel ratio upstream of said catalyst unit so as to be a richer value beyond said predetermined purification-efficiency range, if an output of said air-to-fuel ratio-detection means deviates from a predetermined range, and an air-to-fuel ratio downstream of said catalyst unit is lean.