Catalyst deterioration detecting system and catalyst deterioration detecting method of internal combustion engine

Abstract

A catalyst deterioration detecting system of an internal combustion engine includes a measuring unit that measures the oxygen storage capacity of a catalyst, a detector that detects or estimates the temperature of the catalyst, and a detector that detects poisoning of the catalyst based on the relationship between a change in the catalyst temperature and a change in the oxygen storage capacity corresponding to the change in the catalyst temperature. The change in the oxygen storage capacity corresponding to the change in the catalyst temperature varies depending on the presence or absence of poisoning of the catalyst. Thus, the catalyst deterioration detecting system is able to favorably detect poisoning of the catalyst by utilizing this relationship, and distinguish temporary deterioration due to catalyst poisoning from permanent deterioration. A method of detecting deterioration of the catalyst is also provided.

Description

INCORPORATION BY REFERENCE[0001]The disclosure of Japanese Patent Application No. 2007-011247 filed on Jan. 22, 2007, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The invention relates to a catalyst deterioration detecting system that detects deterioration of a catalyst disposed in an exhaust passage of an internal combustion engine, and also relates to a catalyst deterioration detecting method.[0004]2. Description of the Related Art[0005]Generally, a catalyst is disposed in an exhaust passage of an internal combustion engine so as to treat or clean exhaust gas. One type of the catalyst is, for example, a three-way catalyst that has an O2 storage function of adsorbing and releasing oxygen depending on the air / fuel ratio of exhaust gas entering the catalyst. More specifically, the catalyst adsorbs and stores excessive oxygen present in the exhaust gas when the ai...

AI Technical Summary

Benefits of technology

[0014]It is found from experiments and research carried out by the inventors that a change in the catalyst temperature and a change in the oxygen storage capacity corresponding to the change in the catalyst temperature has a certain relationship, namely, the value of the oxygen storage capacity changes to a larger value as the catalyst temperature changes to a higher temperature level. It is also found that the change in the oxygen storage capacity corresponding to the change in the catalyst temperature is relatively large if the catalyst is free from poisoning, and is relatively small if the catalyst suffers poisoning. The catalyst deterioration detecting system and method of the internal combustion engine as described above are able to favorably determine the presence or absence of poisoning of the catalyst by utilizing the relationships as described above. It is thus possible to detect deterioration of the catalyst while distinguishing permanent deterioration to be detected from temporary deterioration due to poisoning of the catalyst.

[0028]The catalyst deterioration detecting system or method according to this invention provides an excellent effect that it can detect permanent deterioration of a catalyst while distinguishing it from temporary deterioration due to poisoning.

Problems solved by technology

Where such a fuel is supplied to the engine, poisoning (e.g., S (sulfur) poisoning) may occur to the catalyst, namely, the poisoning substance may be accumulated in the catalyst, resulting in reduction of the performance of the catalyst.

If the poisoning occurs, catalytic reactions to adsorb and release oxygen are impeded or hampered, and the oxygen storage capacity of the catalyst is reduced.

Thus, unless a controller of the engine detects catalyst deterioration while distinguishing from temporary deterioration due to poisoning, there is a possibility of erroneously determining that a catalyst whose exhaust treatment performance is temporarily reduced due to poisoning is deteriorated even though this catalyst should be regarded as being normal.

No suitable system has been found which effectively utilizes this fact when detecting catalyst deterioration, and is able to detect deterioration of a catalyst while distinguishing permanent deterioration from temporary deterioration due to poisoning.

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