NOx CLEANING DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To provide a NOx cleaning device for an internal combustion engine for holding a NOx catalyst durable while avoiding its continuous operation with the NOx catalyst at an excessive temperature.

SOLUTION: The NOx cleaning device comprises a SCR catalyst (the NOx catalyst) provided in an exhaust system 2 for the engine 1 for selectively reducing NOx in exhaust gas, a urea water supply device (reducer supply means) for supplying urea water as a reducer to the exhaust system 2 upstream from the SCR catalyst 17, a catalyst temperature sensor 22 for detecting a catalyst temperature tg, urea water supply amount setting means for setting an addition amount DNH3of the urea water in accordance with the catalyst temperature tg, and addition amount correcting means for correcting the addition amount DNH3set by the urea water supply amount setting means with an increment value ΔD in accordance with the addition amount DNH3set by the urea water supply amount setting means and the catalyst temperature tg when the catalyst temperature tg is an excessive rising temperature (a preset temperature) tgβ or higher.

COPYRIGHT: (C)2004,JPO