Patent ID: 9255532
Filing Date: 2016-02-09
CPC Classification: F01N,F02D,F02M

Claim Text:
1. An air-fuel ratio control system of an internal combustion engine, the air-fuel ration control system comprising: an electronic control unit operatively connected to the internal combustion engine, the electronic control unit configured to perform air-fuel ratio feedback control through main feedback control based on a concentration of oxygen in exhaust gas upstream of a catalyst and sub feedback control based on the concentration of oxygen in exhaust gas downstream of the catalyst, the electronic control unit configured to store a constant component of a sub feedback correction value of the sub feedback control as a sub feedback learned value, and the electronic control unit is configured to set a feedback target value of the main feedback control to values that are different depending on whether or not exhaust gas is recirculated into intake air, the electronic control unit is configured to correct the feedback target value of the main feedback control when the recirculation of exhaust gas is not conducted when the constant component of the sub feedback correction value obtained when an amount of recirculated exhaust gas is short of a required amount thereof is stored as the sub feedback learned value, the electronic control unit configured to operate the internal combustion engine in response to the corrected feedback target value of the main feedback control.