EXHAUST EMISSION CONTROL DEVICE FOR DIESEL ENGINE

摘要

PROBLEM TO BE SOLVED: To efficiently purify exhaust by controlling an exhaust temperature to a temperature area having high conversion efficiency of a NOx catalyst. SOLUTION: This diesel engine is provided with a nitrogen oxide reduction catalyst 15 on an engine exhaust path 12. A detection means 36, 37 detecting an operation state and a variable valve system 14 variably control the expansion ratio of an engine are provided, and the open timing of an exhaust valve is advanced and delayed so as to obtain a predetermined exhaust temperature in response to the engine operation state.