Patent ID: 6775608
Filing Date: 2004-08-10
Classification: F01N,F02D

Abstract:
An air-fuel ratio controller of an internal combustion engine, the air-fuel ratio controller comprising:an exhaust gas sensor provided between an upstream catalyst and a downstream catalyst that are disposed in an exhaust manifold, the upstream catalyst being disposed upstream of the exhaust gas sensor and the downstream catalyst being disposed downstream of the exhaust gas sensor; a virtual exhaust gas sensor virtually provided downstream of the downstream catalyst; and a control unit configured to estimate an estimated output of the virtual exhaust gas sensor based on a gas amount that contributes to reduction of the upstream and downstream catalysts and a detected output of the exhaust gas sensor provided between the upstream and downstream catalysts after an operating condition in which an air-fuel ratio is lean is cancelled, or after a fuel cut is cancelled, and to perform first air-fuel ratio control for controlling the air-fuel ratio of the engine in accordance with the estimated output.