| 摘要 |
PROBLEM TO BE SOLVED: To provide an air fuel ratio control device which keeps purification efficiency of harmful substances HC, CO, NOby means of catalyst high and reduces exhaust amount of the harmful substances furthermore.SOLUTION: A target value to be compared with an output of an air fuel ratio sensor on the upstream of catalyst is caused to rise and fall in accordance with an index value FACF which represents the degree of the air fuel ratio based on the output of the air fuel ratio sensor on the downstream of catalyst. Further, when the index value FACF falls into the range around a theoretical air fuel ratio, the ratio of change amount of the target value to the change amount of the index value FACF is set to be smaller and, when the target value FACF is biased to the lean side or the rich side from the range around the theoretical air fuel ratio, the ratio of change amount is set to be larger. |
