| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust emission control device allowing calibration of a downstream air-fuel ratio sensor of an electro motive force type, in the exhaust emission control device feedback-controlling an air-fuel ratio of an engine based on output values of air-fuel sensors upstream and downstream of a catalyst. SOLUTION: In this exhaust emission control device, sub-feedback controlled variables vafsfb are calculated so that steady-state deviation of an output value Voxs of the downstream air-fuel ratio sensor 67 of the electro motive force type from a downstream target value Voxsref corresponding to a stoichiometric air-fuel ratio becomes zero, and the air-fuel ratio of the engine is feedback-controlled so that steady-state deviation of a virtual air-fuel ratio abyfs based on the sum of the sub-feedback controlled variables vafsfb and an output value vabyfs of an upstream air-fuel ratio sensor 66 of a limiting current type after the calibration using characteristics in an inert state from an upstream target valve abyfr as a stoichiometric air-fuel ratio becomes zero. In the steady state, calibration of the downstream air-fuel ratio sensor 67 is performed so that the sub-feedback controlled variables vafsfb become zero. COPYRIGHT: (C)2004,JPO&NCIPI
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