EXHAUST PURIFICATION DEVICE

摘要

An exhaust purification device in which the difference in thermal expansion between the particulate filter side and the selective reduction type catalyst side can be reliably absorbed without causing deposition of urea. An exhaust purification device has a communication flow path (9) having an S-shaped structure and is constructed so that an aqueous urea solution can be added to the upstream of the communication flow path (9). The communication flow path (9) has a particulate filter (5) and a selective reduction type catalyst arranged parallel to each other such that the entrance ends of the filter and the catalyst face the same direction and such that exhaust gas (3) discharged from the exit end of the particulate filter (5) is turned back in the opposite direction to lead the gas to the entrance end of the adjacent selective reduction type catalyst. The middle of a mixing pipe (10) forming a straight portion of the communication flow path (9) is constructed as a double-walled tube portion (18) where an inner tube (16) and an outer tube (17) are overlapped on each other in an insertable and extractable manner. The tail end of the outer tube (17) is secured to the outer periphery of the inner tube (16), a bellows (19) stretchable and retractable in the axial direction is formed at an appropriate position of the outer tube (17), and a seal ring (20) is fitted on the outer periphery of the tail end of the inner tube (16).