Power plants – Internal combustion engine with treatment or handling of... – Having sensor or indicator of malfunction – unsafeness – or...
Reexamination Certificate
2000-07-20
2002-06-25
Denion, Thomas (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
Having sensor or indicator of malfunction, unsafeness, or...
C060S274000, C060S286000
Reexamination Certificate
active
06408616
ABSTRACT:
TECHNICAL FIELD
This invention relates to on-board diagnostics and, more particularly, to an on-board diagnostic method and system for diesel vehicles that determines the current hydrocarbon (HC) conversion based on the exotherm generated by a reductant injection strategy and a theoretical exotherm assuming complete conversion of the injected hydrocarbon and provides an indication if the current HC tailpipe emittance exceeds a target threshold.
BACKGROUND ART
It is desirable to add reductant to the lean environment of diesel exhaust to reduce NO
x
emissions. When injecting reductant into the engine exhaust, the burning of hydrocarbons across the catalyst releases heat, which increases the post-catalyst temperature. This resulting rise in temperature is directly related to catalyst efficiency, the concentration of HC in the exhaust, and is a time dependent function of engine exhaust flow. As shown in
FIG. 1
, as the catalyst ages catalyst efficiency degrades, and HC light-off is delayed to higher catalyst temperatures. For a new vehicle, the catalyst is fresh and the secondary fuel injection system is fully functional, the catalyst efficiency is expected to be high, and the fuel injection quantity correct. Under these conditions, the degree of temperature rise, DT, should be at its maximum possible value. As the vehicle mileage increases and the catalyst ages, HC conversion efficiency decreases accordingly. This reduction in efficiency will reduce the degree of temperature rise, DT, from the fresh value. Monitoring the degree of temperature rise, DT, provides a means to estimate catalyst efficiency, which in turn can be used to infer whether required emission levels are being met. While temperature sensors have been used in the past to monitor catalyst activity (e.g., U.S. Pat. Nos. 5,201,802 and 5,706,652), the prior art approaches have not used an injected reductant quantity specifically for and sized to enhance catalyst performance monitoring.
DISCLOSURE OF INVENTION
In accordance with the present invention, a method is proposed for evaluating catalyst efficiency by monitoring catalyst exotherm level. More particularly, a diesel diagnostic strategy for evaluating catalyst efficiency is proposed that includes injection of a sufficient amount of HC into the engine exhaust stream to maintain a constant concentration of reductant into the catalyst under variable engine exhaust flow conditions thereby permitting the calculation of a theoretical exotherm. The ratio of the actual to theoretical exotherm is calculated to provide an indication of the actual HC conversion by the catalyst. The actual conversion is compared to data for a catalyst aged to threshold emittance levels to determine whether the vehicle is meeting emission regulations.
REFERENCES:
patent: 5177463 (1993-01-01), Bradshaw et al.
patent: 5201802 (1993-04-01), Hirota et al.
patent: 5625750 (1997-04-01), Puskorius et al.
patent: 5626014 (1997-05-01), Hepburn et al.
patent: 5628186 (1997-05-01), Schmelz
patent: 5630315 (1997-05-01), Theis
patent: 5649420 (1997-07-01), Mukaihira et al.
patent: 5675967 (1997-10-01), Ries-Mueller
patent: 5706652 (1998-01-01), Sultan
patent: 5752382 (1998-05-01), Hanafusa et al.
patent: 5806310 (1998-09-01), Daidou et al.
patent: 5822979 (1998-10-01), Hamburg et al.
patent: 5842341 (1998-12-01), Kibe
patent: 5845487 (1998-12-01), Fraenkle et al.
patent: 5860277 (1999-01-01), Schnaibel et al.
patent: 5916294 (1999-06-01), Naber et al.
patent: 5930993 (1999-08-01), Kammann et al.
patent: 5938715 (1999-08-01), Zhang et al.
patent: 5950422 (1999-09-01), Dolling
patent: 6003307 (1999-12-01), Naber et al.
patent: 6079203 (2000-06-01), Wakamoto
patent: 6119448 (2000-09-01), Emmerling et al.
patent: 6145302 (2000-11-01), Zhang et al.
patent: 6202406 (2001-03-01), Griffin et al.
patent: 6295809 (2001-10-01), Hammerle et al.
Hammerle Robert Henry
Laing Paul Matthew
Mazur Christopher John
Denion Thomas
Ford Global Technologies Inc.
Hanze Carlos
Nguyen Tu M.
LandOfFree
Diesel OBD-II system for detection of degradation of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Diesel OBD-II system for detection of degradation of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Diesel OBD-II system for detection of degradation of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2959388