Method and apparatus for controlling lean operation of an internal combustion engine
Number of patents in Portfolio can not be more than 2000
United States of America Patent
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-
Aug 20, 2002
Grant Date -
N/A
app pub date -
Mar 17, 2000
filing date -
Mar 17, 2000
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A method and system for controlling the operation of 'lean-burn' internal combustion engines determines a current rate of vehicle NO.sub.x emissions, and determines a threshold value for permissible vehicle NO.sub.x emissions based on at least one current value for the intake air-fuel ratio, engine speed, engine load (e.g., brake torque, manifold air pressure, or throttle position), and/or vehicle speed. A differential NO.sub.x emissions rate is calculated as the difference between the current rate and the threshold rate, and the differential rate is accumulated over time to obtain a differential measure representing the amount by which cumulative NO.sub.x emissions have fallen below permissible levels therefor. Lean engine operation is disabled when the differential NO.sub.x emissions measure exceeds a predetermined excess vehicle NO.sub.x emission value. In this manner, vehicle NO.sub.x emissions are favorably controlled even when the engine is operated 'off-cycle,' i.e., under operating conditions falling outside of the FTP driving cycles.
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