Closed loop control for desulphating a NOx trap

摘要

A system for desulphating a NOx trap 18 utilizes a closed loop control 26 of the air-to-fuel (A/F) ratio in order to accurately maintain a precise A/F ratio during desulphation. An oxygen sensor 30 is positioned in the middle of the trap 18 to provide an actual A/F ratio measurement, which is subsequently compared to a target A/F ratio in order to generate a correction signal, which is used to adjust the operation of the engine's fuel injector(s) 22. The trap oxygen sensor 30 can also be used to adaptively update engine state conditions for a more precise switch-over to a trap regeneration phase. A further oxygen sensor 28 is provided for controlling the A/F ratio of the engine exhaust during normal operation of the engine, such as during the stoichiometric phase of the lean burn operation.