Device for purifying the exhaust gases of diesel engines

摘要

In a diesel engine provided with a diesel particulate filter 81 and an exhaust throttle valve 9, noise is decreased that is produced when the exhaust throttle valve is returned back to the fully opened state after a diesel particulate filter 81 has been regenerated by oxidizing and removing the particulate matter deposited thereon. The exhaust system of the diesel engine is equipped with the diesel particulate filter 81 and a catalyst 82 on the upstream thereof, and is further equipped with the exhaust throttle valve 9 on the downstream. The diesel particulate filter 81 is regenerated by operating the diesel engine in a state where the exhaust throttle valve 9 is opened to a small degree. When the regeneration has finished, the diesel engine is run at a decreased rotational speed and, thereafter, the exhaust throttle valve 9 is returned back to the fully opened state. When the engine is run at a decreased rotational speed, the pressure in the exhaust system decreases making it possible to greatly decrease the noise that generates at the time of the opening of the exhaust throttle valve 9.