PURPOSE: To obtain the optimum EGR gas reflux pressure for decreasing a quantity of NOx by providing a soot trap and a gas cooler, and also providing an exhaust pressure control valve on the way of an EGR gas reflux circuit which forces exhaust gas downstream of an exhaust turbine supercharger to flow back to the intake side.
CONSTITUTION: The inlet part of an EGR gas pipe 13 which constitutes an EGR gas reflux circuit 12 is connected to the middle of an exhaust pipe 6, in a diesel engine equipped with an exhaust turbine supercharger 4, and the outlet side of the EGR gas pipe 13 is connected to the middle of an intake pipe 2 via a soot trap 14 and an EGR gas cooler 21 on the way thereof. Consequently, the exhaust gas in the exhaust gas pipe 6 is forced to flow back to an intake pipe 8 in front of a blower 7 as the EGR gas. A variable exhaust pressure control valve 15 which can vary continuously a quantity of the exhaust gas which flows through the exhaust pipe 6, is provided on the way of the exhaust pipe 6 located downstream from the connection part of the EGR pipe 13, and the exhaust gas pressure forced to flow back to the EGR gas pipe 13 is controlled by adjusting the valve 15.
YURI MAKOTO
YOSHIKAWA SHIGERU
