Patent ID: 6434930
Filing Date: 2002-08-20
Classification: F01N,F02D,Y02T

Abstract:
A method for controlling the operation of an internal combustion engine in a motor vehicle, wherein the engine generates exhaust gas including NOx, and wherein exhaust gas is directed through an exhaust gas purification system including a NOx trap before being exhausted to the atmosphere, the method comprising:determining a current rate at which NOx is being exhausted to the atmosphere; determining a threshold rate representing a maximum instantaneous rate at which NOx is permitted to be exhausted to the atmosphere, the threshold rate being based on at least one of the group consisting of an engine speed, a vehicle speed, an engine brake torque, an engine manifold air pressure, and a throttle position; determining a differential rate based on the current rate and the threshold rate; and selecting a restricted range of engine operating conditions based on the differential rate, wherein the restricted range of engine operating conditions is characterized by a plurality of air-fuel ratios, each of the plurality of air-fuel ratios being not leaner than a near-stoichiometric air-fuel ratio.