Air-fuel ratio controller for an internal-combustion engine

摘要

Even when a reaction delay time of an A/F ratio detection device changes, an A/F ratio controller prevents an A/F ratio feedback control from being disturbed. The controller is programmed to calculate an A/F ratio feedback coefficient by proportional term control and integration term control, and to set length of time for said integration term to be carried out in accordance with an operating state of the engine. It is programmed to calculate the integration term based on the set time and to set a proportional term for shifting said A/F ratio feedback coefficient. It is further programmed to detect a deviation between a first A/F ratio feedback coefficient before the integration term is carried out and a second A/F ratio feedback coefficient after the integration term is carried out and the coefficient is shifted by the proportional term set by said means for setting the proportional term. Based on the detected deviation, the length of time for the integration term to be carried out is corrected.