| 摘要 |
PROBLEM TO BE SOLVED: To control air-fuel ratio effectively using two sensors in a system equipped with air-fuel ratio sensor or oxygen sensor installed upstream and downstream of catalyst. SOLUTION: At decelerating in a conventional system, the downstream air- fuel ratio feedback control based upon an oxygen sensor output VOX2 situated downstream is stopped, and only the downstream air-fuel ratio feedback control based upon the output of an air-fuel ratio sensor located upstream is performed. According to this control device, the downstream air-fuel ratio feedback control is not stopped even during deceleration, and the execution of the downstream air-fuel ratio feedback control is continued in the condition that the feedback gain is made smaller than that in constant speed running. This allows the downstream air-fuel ratio feedback correction amount FAF2 to vary mildly, and the deviation of the downstream air-fuel ratio can be lessened to result in reduction of the amount of CO and HC emissions, compared with the conventional system in which FAF2 is fixed at decelerating.
|
