EXHAUST GAS REFLUX DEVICE FOR ENGINE WITH MECHANICAL TYPE SUPERCHARGER

摘要

PURPOSE:To perform reflux of exhaust gas even when an intake air pressure on the downstream of a mechanical supercharger is increased and to improve scanning ability and filling efficiency in a high load region by providing an exhaust gas pressure varying means to boost an exhaust pressure exerted on an EGR passage. CONSTITUTION:An engine-driven mechanical supercharger 24 and an intercooler 25 are disposed on the downstream side of a throttle valve 23 of a common intake air passage 11. An intake air passage 2 on the downstream side of the intercooler 25 is divided into two passages 11c, which are connected to respective independent intake air passages 11a at respective banks. An EGR passage 35 in which an EGR valve 36 is located is run between an exhaust gas passage 12 and an intake air passage 11 on the downstream of a supercharger 24. A variable silencer 40 serving as an exhaust gas pressure varying means is located in the exhaust gas 12 and functioned such that an exhaust gas pressure exerted on the EGR passage 35 is boosted by closing a shutter valve 45 with the aid of an actuator 44. The shutter valve 45 is closed in a supercharge region and an operation region on the side where a load is lower than a set load in a low ration area.