Exhaust gas purification device for an internal combustion engin

Details Exhaust gas purification device for an internal combustion engin Exhaust gas purification device for an internal combustion engin

1998-09-09

1999-10-26

Look, Edward K.

Power plants

Internal combustion engine with treatment or handling of...

Having sensor or indicator of malfunction, unsafeness, or...

60285, 60276, 123691, F01N 300

Patent

active

059707070

ABSTRACT:
In an exhaust gas purification device for an internal combustion engine, a three-way catalyst and a NO.sub.X occluding and reducing catalyst (a NORC) are disposed in the exhaust gas passage of an engine in this order from the upstream side. A first air-fuel ratio sensor is disposed in the exhaust gas passage between the three-way catalyst and the NORC, and a second air-fuel ratio sensor is disposed in the exhaust gas passage downstream of the NORC. An engine electronic control unit (ECU) changes the operating air-fuel ratio of the engine from a lean air-fuel ratio to a rich air-fuel ratio and a rich air-fuel ratio to a lean air-fuel ratio in order to evaluate the abilities of the three-way catalyst and the NORC. The ECU evaluates the catalytic abilities based on the output of the first air-fuel ratio sensor when the engine air-fuel ratio is changed. Further, the ECU evaluates the catalytic ability and the NO.sub.X absorbing capacity of the NORC based on the outputs of the first and the second air-fuel ratio sensor when the engine operating air-fuel ratio is changed. The evaluation of the abilities of both the three-way catalyst and the NORC in one successive changing operation of the engine operating air-fuel ratio is based on only the outputs of the first and the second air-fuel ratio sensor.

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Copending U.S. Application S.N. 974,843, filed Nov. 10, 1992.
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Copending U.S. Application S.N. 620,623, filed Mar. 22, 1996.
Copending U.S. Application S.N. 624,034, filed Mar. 27, 1996.

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