| 摘要 |
PROBLEM TO BE SOLVED: To remove soot and prevent pressure loss from increasing, by providing a path switching means which connects an exhaust gas circulating path with one of an intake path and an exhaust path downstream of cooling means which has oxidation catalyst on the inner surface of an exhaust gas flowing passage and providing a controller which controls the cooling means and the passage switching means. SOLUTION: Because cooling water is not supplied to an EGR cooler 16 when exhaust gas is exhausted to an exhausting tube 5 through an exhaust gas returning tube 11, exhaust gas which passes through the EGR cooler 16 is not cooled and temperature of the exhaust gas is kept high. This temperature of the exhaust gas is enough to activate oxidation catalyst. Therefore, when high temperature of exhaust gas passes through the EGR cooler 16 oxidation catalyst is activated. Thus, soot which is adhered onto the inner surface of an exhaust gas flowing path in the EGR cooler 16 is burned again and removed, the inner surface of an exhaust gas flowing path is kept in initial condition, and therefore pressure loss of the EGR cooler 16 is prevented from increasing. |
