CATALYST DETERIORATION DETERMINATION DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To enhance accuracy of deterioration determination of a catalyst when a temperature of the catalyst varies.

SOLUTION: A catalyst deterioration determination device for internal combustion engine includes: a purification rate calculator for calculating a purification rate of NOx on the basis of NOx concentration on upstream and downstream sides of a NOx catalyst; a purification rate corrector for correcting the purification rate to a value in a predetermined normal state, assuming that a proportion of an amount of ammonia which the NOx catalyst adsorbs to an amount of ammonia which the NOx catalyst can adsorb at a maximum is a determined value; and a determiner for determining the deterioration determination of a selective reduction NOx catalyst on the basis of the purification rate after corrected by the purification rate corrector during reduction of the temperature of the NOx catalyst.

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