Device for determining deterioration of a catalyst for an engine

Details Device for determining deterioration of a catalyst for an engine Device for determining deterioration of a catalyst for an engine

1997-08-07

1999-11-16

Denion, Thomas E.

Power plants

Internal combustion engine with treatment or handling of...

Having means analyzing composition of exhaust gas

60286, 60285, 60277, F01N 300

Patent

active

059836296

ABSTRACT:
A device for determining deterioration of a catalyst having an O.sub.2 storage capability and disposed in an exhaust passage of an engine comprises: upstream and downstream air-fuel ratio sensors disposed in the exhaust passage upstream and downstream of the catalyst respectively for detecting air-fuel ratios of exhaust gas upstream and downstream of the catalyst. The air-fuel ratio of the exhaust gas flowing into the catalyst is controlled on the basis of the output of the upstream air-fuel ratio sensor to make the air-fuel ratio flowing into the catalyst a target air-fuel ratio. A ratio of the length of the response curve of the output of the downstream air-fuel ratio sensor to the length of the response curve of the output of the upstream air-fuel ratio sensor is calculated. A ratio of the frequency of the output of the downstream air-fuel ratio sensor to the frequency of the output of the upstream air-fuel ratio sensor is calculated. It is determined that the catalyst has deteriorated when the length ratio is greater than a first predetermined ratio, or when the length ratio is greater than a second predetermined ratio which is smaller than the first predetermined ratio and the frequency ratio is greater than a third predetermined ratio.

REFERENCES:
patent: 5279116 (1994-01-01), Shimizu et al.
patent: 5301501 (1994-04-01), Shimizu et al.
patent: 5363646 (1994-11-01), Orzel et al.
patent: 5412941 (1995-05-01), Suzuki et al.
patent: 5640847 (1997-06-01), Nakajima et al.
patent: 5758491 (1998-06-01), Agustin et al.

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