Exhaust gas purifier for an IC engine comprises a nitrogen oxides catalyst arranged in the exhaust gas channel of the engine, and an air-fuel ratio regulator

摘要

Exhaust gas purifier for an IC engine (1) comprises a NOx catalyst (14) arranged in the exhaust gas channel (12) of the engine, and an air-fuel ratio regulator (21) in which the operating state of the engine is searched. The air-fuel ratio regulator has a device for the engine operation with rich air-fuel ratio to switch the engine operation to the operation with a stoichiometric air-fuel ratio. After the engine is operated with a rich air-fuel ratio, the operational state is switched from one with lean air-fuel ratio to one with stoichiometric air-fuel ratio. Preferred Features: A time period in which the device is set in operation for the rich air-fuel ratio state depends on the extent of the enrichment. The air-fuel ratio in the rich air-fuel ratio operational state is established so that it lies within the region of 13.2-14.2.