NOx PURIFYING DEVICE OF INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To prevent reduction of durability of an air compressor and prevent fuel economy from being low due to driving of the air compressor.

SOLUTION: This NOx purifying device comprises: a SCR catalyst 23 provided to an exhaust system 2 of an engine 1; a urea water supply device 22 which supplies a urea water via a supply passage r1 communicating with the exhaust system in an upstream of the SCR catalyst 23; a boost pressure air pipe 31 driven by the engine 1 or an electric motor and supplying a pressurized air to the supply passage r1 in the upstream of a region of supply of the urea water supplied from the urea water supply device 22; a turbocharger 6 arranged in the upstream of the SCR catalyst 23 of the exhaust system; and an assist air switching control means B1 which supply the supply passage r1 with any one of boost pressure air from a suction passage I in the downstream of the turbocharger 6 and the pressurized air from a compression air pump in accordance with a supply amount of the urea water corresponding to an operating condition.

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