| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an EGR system which reduces a temperature of an EGR gas to below the temperature of engine cooling water in an appropriate operation state without discharging white smoke or HC and CO, thereby improving NO<SB POS="POST">X</SB>reduction effect. <P>SOLUTION: This EGR system includes: an EGR pipe 11 which extracts part of an exhaust gas 8 from the exhaust side to recirculate it to the intake side as an EGR gas 8'; a water-cooled EGR cooler 13 arranged in the middle of the EGR pipe 11; an air-cooled EGR cooler 19 arranged in the EGR pipe 11 on the downstream side of the water-cooled EGR cooler 13; a first bypass pipe 20 for supplying the EGR gas 8' while avoiding the air-cooled EGR cooler 19; a second bypass pipe 21 for supplying the EGR gas 8' while avoiding the water-cooled EGR cooler 13; and switching valves 22 and 23 (flow path switching means) for causing the EGR gas 8' flowing in the EGR pipe 11 to flow through the first bypass pipe 20 or the second bypass pipe 21. <P>COPYRIGHT: (C)2013,JPO&INPIT |
