| 摘要 |
PROBLEM TO BE SOLVED: To efficiently occlude NOx within an exhaust emission gas by a catalyst, and convert the NOx occluded in the catalyst into a harmless N2, water or the like to regenerate the catalyst, without complicating structure of an exhaust system. SOLUTION: A catalyst 13 provided in an exhaust passage 12 of an diesel engine 11 occludes NOx in an exhaust gas flowing in the exhaust passage 12, and is regenerated by discharging the occluded NOx when a concentration of oxygen in the exhaust gas is decreased. An EGR valve 16 is provided in an EGR pipe 14 which connects the exhaust passage 12 with an intake passage 18 through the diesel engine 11. An exhaust throttle valve 17 is disposed in the exhaust passage 12 at an exhaust gas downstream side compared with a connecting point of the EGR pipe 14, and an intake throttle valve 19 is disposed in the intake passage 18 at an exhaust gas upstream side compared with the connecting point of the EGR pipe 14. A controller 22 controls the EGR valve 16, the exhaust throttle valve 17, and the intake throttle valve 19 based on an output detected by a regeneration start detection sensor 21 which detects a regeneration start timing of the catalyst. |
