Patent ID: 6672053
Filing Date: 2004-01-06
Classification: F01N,F02D

Abstract:
A method for controlling an internal combustion engine coupled to an emission control device with an exhaust sensor coupled downstream of the emission control device, the method comprising:operating the engine at a lean air-fuel ratio wherein NOx is stored in the emission control device; monitoring at least two conditions which include: (1) whether an actual fuel amount supplied to the emission control device is greater than an estimate of fuel required to purge the emission control device of stored NOx; and (2) whether an indication is provided by the sensor; operating the engine at a first rich air-fuel ratio to remove said stored NOx, said operation at said first rich air-fuel ratio ending when either of said monitored conditions is detected; and when operation at said first rich air-fuel ratio is ended based on said actual fuel supplied being greater than said estimate, operating the engine at a second rich air-fuel ratio after operating at said first rich air-fuel ratio at least until an indication is provided by the downstream sensor.