REDUCING NOx EMISSION FROM AN ENGINE

摘要

An internal combustion engine (10) has an exhaust system (26) that includes an NOx trap (24) and an exhaust gas oxygen sensor (22), and a management system (18) for selectively operating the engine in a lean burn mode, during which NOx gases produced by the engine are stored in the NOx trap (24) and a closed loop mode in which the mixture strength is oscillated about stoichiometry in dependence upon the output signal of an exhaust gas oxygen sensor located in the engine exhaust system. The response of the management system to the output signal of the exhaust gas oxygen sensor (22) when operating in closed loop mode is biased to create a slightly lean condition in the exhaust system to prevent the release of the NOx gases stored in the trap (24).