Patent ID: 6490855
Filing Date: 2002-12-10
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 during a first interval; determining an estimate of fuel required to reduce NOx stored in the device; operating the engine at a first rich air-fuel ratio during a second interval following said first interval; during said second interval, determining an actual amount of fuel used to reduce NOx stored in the device, and repeatedly monitoring whether said actual amount of fuel used is greater than a percentage of said estimate of fuel required; and operating the engine at a second rich air-fuel ratio during a third interval following said second interval when said monitoring indicates that said actual amount of fuel used is greater than a percentage of said estimate of fuel required, and ending said third interval based on the downstream sensor.