| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve problem of a conventional urea SCR system wherein exhaust resistance is increased due to the adhesion of the crystal of a compound derived from urea to a mixing member for sufficiently dispersing urea water in an exhaust passage, and output performance is lowered due to the increase. <P>SOLUTION: A mixing member 15 for promoting the mixing of urea water supplied by a urea water supply means 13 with exhaust gas is installed between the urea water supply means 13 of an exhaust passage 3 and a selective reduction catalyst 16. The exhaust emission control device comprises a second differential pressure sensor 22 for detecting the pressure difference between the immediate upstream side and the immediate downstream side of the mixing member 15. The temperature of the exhaust gas is increased when the differential pressure detected by the sensor 22 is equal to or higher than a predetermined value. Since the crystal of the compound adhered to the mixing member 15 is fused and removed, the opening of the mixing member 15 is re-increased, and an increase in exhaust resistance in the exhaust passage 3 is suppressed, the problem of the torque performance of an engine 1, accordingly, the problem of lowering of output performance is eliminated. <P>COPYRIGHT: (C)2009,JPO&INPIT |
