| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust gas recirculation system equipped with precise controllability for EGR(exhaust gas recirculation) by presuming the EGR rate of flow accurately from the differential pressure between in front of and after an EGR valve and the degree of opening of the EGR valve. SOLUTION: The target excess air ratio (target λ) is set, and the intra- cylinder EGR amount of an internal combustion engine is derived from the sensed differential pressure between in front of and after an EGR valve, and the intra-cylinder actual excess air ratio (actual λ) is presumed using the obtained EGR amount, and a target EGR amount setting means 45 sets the target EGR amount on the basis of the target and actual excess air ratios while an EGR valve opening controlling means 46 drives the EGR valve on the basis of the set target EGR amount. At the time of presuming the actual excess air ratio, a differential pressure increasing means 49 increases the differential pressure about the EGR valve 25 if it lies under the specified level on the basis of the EGR calculated by a differential pressure calculating means 47. |
