CATALYST DEGRADATION DETECTION APPARATUS

摘要

PROBLEM TO BE SOLVED: To remove the error resulted from response delay time of a signal of a catalyst downstream sensor from an oxygen storage amount of a catalyst for determining existence and nonexistence of degradation of the catalyst and keep the necessary storage capacity of a memory low.

SOLUTION: A determination oxygen storage amount OSC used for determining existence and nonexistence of degradation of the catalyst is the value obtained by applying the correction of a correction amount H for removing the error resulted from the response delay time Tr of the output signal VO of the oxygen sensor 18 to the oxygen storage amount OSA calculated every minimal time ▵t. The correction amount H is a value that is calculated using slopes θn stored in the memory 21a, i.e., the slopes θn (n=1 to K) for the number (k times) of storage cycles T (>▵t) corresponding to the response delay time Tr, or the like, and becomes more accurate as a value corresponding to the error as the storage cycle T becomes relatively shorter with respect to the response delay time Tr and the number K of the slopes θn stored in the memory 21a increases. The necessary storage capacity of the memory 21a is inhibited from increasing excessively even if the number k increases.

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