AIR0-FUEL RATIO CONTROL METHOD OF ENGINE AND AIR-FUEL RATIO CONTROL DEVICE OF ENGINE

摘要

PROBLEM TO BE SOLVED: To provide an air fuel ratio control method by which an optimum amount of a reducing agent can be supplied even through O2remaining in a three way catalyst and having a slow desorption speed is desorbed all at once for some reason after the rich spike processing. SOLUTION: The method includes the step of executing a first rich spike processing, the step of executing a first stoichiometric operation after the first rich spike processing, the step of estimating a stoichiometric operation amount during the first stoichiometric operation as a first stoichiometric operation amount, the step of executing a second rich spike processing again after completion of the first rich spike processing, the step of executing a second stoichiometric operation immediately after the second rich spike processing and rich shift steps (S48, 49, 54, 55) of making a shift to a rich air-fuel ratio during second stoichiometric operation in accordance with the estimated value of the first stoichiometric operation amount. COPYRIGHT: (C)2007,JPO&INPIT