Apparatus and method for engine exhaust purification
AssigneeNissan Motor Co., Ltd.
InventorsAtsushi Sakai, Hajime Oguma
Life of this patent
Estimating the term…
Abstract
An oxygen storage amount of a catalyst is estimated by a controller in accordance with a sensed air-fuel ratio of an inflowing exhaust gas mixture flowing into the catalyst, and a sensed intake air amount of the engine, to control the air-fuel ratio of the engine. The estimated oxygen storage amount is corrected to reduce an error in computing the estimated oxygen storage amount when a downstream exhaust condition sensed by an exhaust sensor disposed on the downstream of the catalyst becomes equal to a predetermined threshold, which is modified in accordance with the intake air amount for better emission control performance.
Claims16
An engine exhaust purifying apparatus comprising:
- an air flow sensor arranged to sense an engine intake air amount;
- a catalyst disposed in an engine exhaust passage;
- an upstream exhaust sensor disposed in the engine exhaust passage on an upstream side of the catalyst, and arranged to sense an upstream exhaust condition representing an air-fuel ratio of an inflowing exhaust gas mixture flowing into the catalyst;
- a downstream exhaust sensor disposed on a downstream side of the catalyst and arranged to sense a downstream exhaust condition representing an air-fuel ratio of an outflowing exhaust gas mixture flowing out of the catalyst;
- and
- a controller configured;
- to compute an estimated oxygen storage amount of the catalyst in accordance with the air-fuel ratio of the inflowing exhaust gas mixture and the engine intake air amount;
- to control an air-fuel ratio of the engine in accordance with the estimated oxygen storage amount so as to bring an actual oxygen storage amount of the catalyst to a desired value;
- to correct the estimated oxygen storage amount to reduce an error in computing the estimated oxygen storage amount when the downstream exhaust condition sensed by the downstream exhaust sensor becomes equal to a predetermined threshold;
- and
- to modify the threshold in accordance with the intake air amount.
An engine exhaust purifying process for an engine equipped with a catalyst disposed in an engine exhaust passage, the engine exhaust purifying process comprising:
- computing an estimated oxygen storage amount of the catalyst in accordance with a sensed upstream exhaust condition representing an air-fuel ratio of an inflowing exhaust gas mixture flowing into the catalyst and a sensed engine intake air amount;
- controlling an air-fuel ratio of the engine in accordance with the estimated oxygen storage amount;
- correcting the estimated oxygen storage amount to reduce an error in computing the estimated oxygen storage amount when a downstream exhaust condition representing an air-fuel ratio of an outflowing exhaust gas mixture flowing out of the catalyst becomes equal to a predetermined threshold;
- and
- modifying the threshold in accordance with the sensed engine intake air amount.
An engine exhaust purifying apparatus for an engine equipped with a catalyst, the engine exhaust purifying apparatus comprising:
- means for sensing an engine intake air amount;
- means for sensing an upstream exhaust condition representing an air-fuel ratio of an inflowing exhaust gas mixture flowing into the catalyst;
- means for sensing an downstream exhaust condition representing an air-fuel ratio of an outflowing exhaust gas mixture flowing out of the catalyst;
- and
- means for computing an estimated oxygen storage amount of the catalyst in accordance with the upstream exhaust condition of the inflowing exhaust gas mixture and the engine intake air amount;
- means for controlling an air fuel ratio of the engine in accordance with the oxygen storage amount;
- means for correcting the estimated oxygen storage amount to reduce an error in computing the estimated oxygen storage amount when the downstream exhaust condition sensed by said means for sensing the downstream exhaust condition becomes equal to a predetermined threshold;
- and
- means for modifying the threshold in accordance with the intake air amount.
Dependencies are inferred from the claim text.