CATALYST DETERIORATION DETERMINATION DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To provide a catalyst deterioration determination device which can determine deterioration degree of a catalyst with high accuracy. SOLUTION: An exhaust emission control device 13 arranged on an exhaust pipe 12 of an engine 1 is prepared by housing an upstream side housing part 13a and a downstream side housing part 13b respectively housing catalyst are housed in one vessel. An O2 sensor 15 is arranged between the upstream side housing part 13a and the downstream side housing part 13b. An air-fuel ratio feedback control is performed according to an output of the O2 sensor 15. A deterioration degree is determined in whole of the catalyst in the exhaust emission control device 13 based on a determination time TCHK corresponding to an inversion frequency of the output of the O2 sensor 15. A volume of the upstream side housing part 13a ranges between 30 and 60% of a total volume.