DETERIORATION DIAGNOSIS DEVICE AND DETERIORATION DIAGNOSIS METHOD FOR EXHAUST EMISSION CONTROL CATALYST

摘要

PROBLEM TO BE SOLVED: To prevent erroneous determination of deterioration of an exhaust emission control catalyst by addition of oxidation reaction heat by HC discharged from a HC adsorption part, in a deterioration diagnosis of an exhaust emission control catalyst including the HC adsorption part.SOLUTION: A deterioration diagnosis device includes: exhaust emission control catalyst actual temperature parameter detection means 80 for detecting a parameter correlated to an actual temperature of an exhaust emission control catalyst; deterioration determination means 100 for receiving a detection value of the exhaust emission control catalyst actual temperature parameter detection means 80 when a predetermined diagnosis execution condition is established, and for determining that the exhaust emission control catalyst is in a deterioration state when the detection value is on a low temperature side further than a predetermined diagnosis temperature parameter threshold value 100; HC discharge amount calculation means 90 for calculating the amount of HC discharge from a HC adsorption part; and deterioration erroneous determination prevention means for receiving a signal from the HC discharge amount calculation means 90 and preventing the deterioration determination means from performing erroneous determination by the increase of the exhaust emission control catalyst actual temperature parameter according to the increase of the amount of HC discharge.