Patent ID: 9512795
Filing Date: 2016-12-06
CPC Classification: F02D,G01M

Claim Text:
1. An inter-cylinder air-fuel ratio variation abnormality detection apparatus including: an air-fuel ratio sensor installed in an exhaust passage common to a plurality of cylinders in a multicylinder internal combustion engine; and a control apparatus configured to calculate a parameter correlated with a degree of variation in output from the air-fuel ratio sensor and to detect an inter-cylinder air-fuel ratio variation abnormality based on the calculated parameter, wherein the control apparatus is configured to calculate a division crank angle that bisects an area of a region present in at least one of a rich and a lean sides with respect to a mean value of an output waveform from the air-fuel ratio sensor during one cycle of the internal combustion engine or such a predetermined constant value as corresponds to a center of fluctuation in the output waveform, the region being enclosed by an output waveform from the air-fuel ratio sensor and the mean value or the constant value, and to identify an abnormal cylinder with a deviation of the air-fuel ratio based on the division crank angle.