Patent ID: 7401462
Filing Date: 2008-07-22
Classification: F02D

Abstract:
1. Method for controlling regeneration of a NOx trap comprising: estimating an accumulated NOx in a NOx trap located in the exhaust path of an engine; estimating a temperature of the NOx trap; determining whether the temperature of the NOx trap exceeds a threshold temperature; determining whether the estimated NOx in the NOx trap exceeds a second threshold value greater than a first threshold value, the second predetermined threshold comprising a fraction of capacity of the NOx trap; determining a desired air-fuel ratio for initiating regeneration of the NOx trap, the desired air-fuel ratio being determined based upon one or a combination of the estimated NOx stored within the NOx trap and the temperature of the NOx trap; initiating regeneration of the NOx trap when the estimated NOx in the NOx trap exceeds the second threshold value or when the estimated temperature of the NOx trap exceeds the threshold temperature by forcing homogenous operation of the engine at the desired air-fuel ratio; hastening regeneration of the NOx trap by reducing the size of a stratified charge operating region of the engine when the estimated NOx in the NOx trap exceeds the first threshold value and initiating regeneration when the stratified charge operating region of the engine is exited; and wherein reducing the stratified charge operating region comprises reducing engine speed and engine load at which to operate the engine in stratified charge operating mode.