CATALYST DETERIORATION DETECTING DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To provide a catalyst deterioration detecting device capable of detecting the degree the deterioration of each catalyst, respectively, in a catalytic converter provided with two catalysts or more arranged in series. SOLUTION: This catalyst deterioration detecting device for an internal combustion engine provided with a lower shift type catalyst provided in the upstream of an exhaust system of the internal combustion engine and purifying exhaust gas and an underfloor catalyst provided in the downstream of the exhaust system and purifying exhaust gas is provided with an oxygen concentration detection means provided in the downstream of the underfloor catalyst and a deterioration detection means for detecting the degree of the deterioration of the lower shift type catalyst based on an output of the oxygen concentration detection means. In one embodiment of this invention, the catalyst deterioration detection device is constituted such that the deterioration detection means detects the degree of the deterioration of the underlfoor catalyst based on the previously detected degree of the deterioration of the lower shift type catalyst.