| 摘要 |
PROBLEM TO BE SOLVED: To keep exhaust gas cleaning ability of a catalyst device as long as possible, by quickly changing an air-fuel ratio from a rich state to a lean state, or from the lean state to the rich state when the same air-fuel ratio state is continued. SOLUTION: An oxygen sensor outputs a binary signal indicating whether or not the concentration of the oxygen contained in exhaust gas exceeds a predetermined threshold. A control apparatus performs an integral control for cumulatively increasing or decreasing the air-fuel ratio by a predetermined correction amount based on the binary signal output from the oxygen sensor, so that the air-fuel ratio is controlled to go back and forth between a rich state and a lean state. In the air-fuel ratio control, if the binary signals of the oxygen sensor shows that the rich state or the lean state is continued more than the predetermined engine cycle, a correction amount is increased. COPYRIGHT: (C)2006,JPO&NCIPI
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