| 摘要 |
An engine 1 includes: a urea water injector 40 which is provided in an exhaust pipe 30 of the engine 1 mounted on a vehicle and which injects and supplies urea water into the exhaust pipe 30; a selective reduction catalyst 34 which is provided in the exhaust pipe 30 on a downstream side of the urea water injector 40, and which reduces and purifies nitrogen oxide contained in an exhaust gas inside the exhaust pipe 30 by the urea water supplied from the urea water injector 40; and a low-pressure exhaust gas recirculation passage 45 which introduces the exhaust gas from the exhaust pipe 30 on an upstream side of the selective reduction catalyst 34 and recirculates the exhaust gas into an intake pipe 20 of the engine 1, in which when an exhaust gas recirculation valve 48 for opening and closing the low-pressure exhaust gas recirculation passage 45 is switched from a closed state to an open state, the urea water injector 40 stops injection and supply of the urea water. |
