Patent ID: 7497210
Filing Date: 2009-03-03
Classification: F01L,F01N,F02D,Y02T

Abstract:
1. A cylinder air-fuel ratio control apparatus of an internal combustion engine, comprising: an air-fuel ratio sensor for detecting an air-fuel ratio of exhaust gas, the air-fuel ratio sensor being disposed in an exhaust collecting portion where exhaust gas of each cylinder of the internal combustion engine collects and flows, a cylinder air-fuel-ratio estimation means for estimating the air-fuel ratio of each cylinder on the basis of a model of relating a detected value of the air-fuel sensor to the air-fuel ratio of each cylinder as a state variable; a determination means for determining whether an engine operating state is an operating state in which correct estimation of the air-fuel ratio of each cylinder is difficult, the correct estimation being performed by the cylinder air-fuel ratio estimation means; and a state variable reset means for resetting the state variable when it is determined by the determination means that the engine operating state is the operating state in which estimation of a cylinder air-fuel ratio is difficult.