Patent ID: 7181902
Filing Date: 2007-02-27
Classification: F01N,F02D

Abstract:
1. Method for controlling a direct-injection gasoline engine during regeneration of a lean NOx trap disposed in an exhaust path of the engine, the regeneration characterized by a transition from lean stratified engine operation to rich homogeneous engine operation, comprising: upon initiation of a lean NOx trap regeneration event, determining a current air-fuel ratio and comparing the current air-fuel ratio to a lean limit air-fuel ratio; delaying the transition from lean stratified engine operation to rich homogeneous engine operation until the current air-fuel ratio reaches the lean limit air-fuel ratio; initiating transition from lean stratified engine operation to rich homogeneous engine operation when the current air-fuel ratio reaches the lean limit air-fuel ratio; and disabling an air-fuel feedback control for a period of time following the transition into and out of the lean NOx trap regeneration event.