Patent ID: 9026341
Filing Date: 2015-05-05
Classification: F02D

Abstract:
1. An apparatus for detecting an abnormal air-fuel ratio variation among cylinders of a multi-cylinder internal combustion engine, comprising: a fuel injection amount changing control unit that executes fuel injection amount changing control for changing a fuel injection amount of at least one predetermined target cylinder among the cylinders by a predetermined amount; an air-fuel ratio control unit that executes air-fuel ratio feedback control for causing an air-fuel ratio detected on the basis of a signal output from an air-fuel ratio detecting unit provided in an exhaust passage to follow a predetermined target air-fuel ratio, and that includes a target air-fuel ratio changing unit that, when the fuel injection amount changing control is executed, shifts a target air-fuel ratio in the air-fuel ratio feedback control from the predetermined target air-fuel ratio by an amount corresponding to an amount of change of the fuel injection amount of the at least one predetermined target cylinder in the fuel injection amount changing control; and a detecting unit that detects an abnormal air-fuel ratio variation among the cylinders on the basis of output fluctuations of the at least one predetermined target cylinder that occur when the fuel injection amount changing control is executed on the at least one predetermined target cylinder.