| 摘要 |
PROBLEM TO BE SOLVED: To prevent the deterioration in an air-fuel ratio control owing to change with time. SOLUTION: A response time constantτof an air-fuel ratio control model is calculated corresponding to an engine operating condition (ex. suction air quantity) to calculate a control gainωof an air-fuel ratio F/B control corresponding to the response time constantτof the air-fuel ratio control model (steps 101 and 102). Then, a deterioration index value of response in an air-fuel ratio sensor is calculated as a model errorΔERR (parameter indicating a degree in an aged deterioration of an air-fuel ratio control system) to obtain a final control gainωby correcting the control gainωwith a correction coefficient f (ΔERR) corresponding to the model errorΔERR (steps 103 and 104). Thereafter, an air-fuel ratio F/B correction quantity FAF is calculated so as to conform the detected air-fuel ratio to the target air-fuel ratio using the response time constantτof the air-fuel ratio control model, the control gainω, a difference between a detected air-fuel ratio and a target air-fuel ratio, etc., according to an equation for calculation of the air-fuel ratio F/B correction quantity FAF introduced from the air-fuel ratio control model.(step 105). COPYRIGHT: (C)2004,JPO&NCIPI
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