EGR GAS COOLING DEVICE AND ITS COOLING METHOD

摘要

PROBLEM TO BE SOLVED: To obtain an EGR gas cooling device capable of suppressing thermal stress of a heat exchanging part performing exchange between EGR gas and cooling medium liquid; to prevent condensate and soot from attaching to a heat transfer surface; to obtain products excellent in durability and heat exchanging efficiency at a low price. SOLUTION: An EGR gas cooler 1 for high temperature equipped with a connection port to EGR piping and an EGR gas cooler 3 for low temperature are connected in series. An inlet 7 is connected between the EGR gas cooler 1 for high temperature and the connection port, an outlet 8 is connected between the EGR gas cooler 1 for high temperature and the EGR gas cooler 3 for low temperature, and bypass piping 6 for circulating low temperature EGR gas is arranged. A selector valve 10 introducing high temperature EGR gas into the EGR gas cooler 1 for high temperature and introducing the low temperature EGR gas through the bypass piping 6 into the EGR gas cooler 3 for low temperature, is installed at the inlet 7 of the bypass piping 6. COPYRIGHT: (C)2004,JPO