AIR-FUEL RATIO CONTROL DEVICE AND AIR-FUEL RATIO CONTROL METHOD FOR INTERNAL COMBUSTION ENGINE

摘要

An air-fuel ratio control device includes an air-fuel ratio sensor provided upstream from a three-way catalyst, and an oxygen sensor provided downstream from the three-way catalyst. The air-fuel ratio control device controls the fuel supply amount based on the output from the air-fuel ratio sensor, and compensates for errors in the air-fuel ratio sensor by correcting the fuel supply amount based on the output from the oxygen sensor. The fuel supply correction amount is calculated based on an integral term that integrates the deviation between the output from the downstream air-fuel ratio sensor and the target air-fuel ratio. When a fuel supply adjustment control is executed, the value of the integral term in the sub-feedback control is not updated for a predetermined period after the fuel supply adjustment control ends. The actual air-fuel ratio is thus brought to the target air-fuel ratio in an appropriate manner.