JPS6436942A - Control device for air-fuel ratio of internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent over-correcting to a lean side by starting a feedback control according to a feedback controlling constant based on the output of an O2 sensor on the lower course side of a catalyst and a correcting quantity in accordance with the output of an O2 sensor on the upper course side of the catalyst after a delay time corresponding to the duration of a condition for making rich. CONSTITUTION:The detected values of an air flow meter 3, crank angle sensors 5, 6, a water temperature sensor 9, a first O2 sensor 13 on the upper course side of a catalyst converter 12, a second O2 sensor 15 on its lower course side, an idling switch 17, etc. are inputted into a control circuit 10. As a condition for making rich as at the time of warming up or accelerating, etc. is satisfied, the control circuit 10 stops an air-fuel ratio feedback control based on the detected values of the O2 sensors 13, 15, to carry out an operation for making rich. At the time of judging to be shifting from the condition of making rich to an air-fuel ratio feedback control condition, after a delay time corresponding to the duration of the condition of making rich, a feedback control constant is set based on the detected value of the second O2 sensor 15, while setting an air-fuel ratio feedback correcting quantity in accordance with the output of the first O2 sensor 13.