EXHAUST EMISSION REFLUXING DEVICE OF INTERNAL COMBUSTION ENGINE

PROBLEM TO BE SOLVED: To determine deterioration in EGR cooler without preparing a special sensor for determining the deterioration. SOLUTION: An exhaust emission reflux device is equipped with: a refluxing gas cooling means 17; a bypass channel 16 for bypassing the refluxing gas cooling means 17; a switching means 19 for allowing one of the refluxing gas cooling means 17 and a bypass channel 16 to alternatively communicate; a refluxing gas volume regulating means 18, a detecting means 20 for detecting a production volume of NOx in an exhaust gas discharged from an engine; and an NOx production volume difference calculating means 21 for calculating a difference in NOx production volume between the cases of selecting the refluxing gas cooling means 17 and the bypass means 16. A difference in NOx production volume when the refluxing gas cooling means 17 is in its initial state is defined as an initial value ΔN1, and further a difference between the initial value ΔN1 and a difference in NOx production volume in an operational state at the same target exhaust emission refluxing rate as that in the state where the initial value ΔN1 has been calculated is defined as ΔN2. Then, a difference between the differences ΔN1 and the initial value ΔN2 is defined as a deterioration level D. When the deterioration level D becomes larger than a threshold m, the refluxing gas cooling means 17 is determined to have been deteriorated. COPYRIGHT: (C)2009,JPO&INPIT