EXHAUST EMISSION CONTROL DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an exhaust emission control device enhancing activation of a NOx catalyst device by assuring a sufficient time for contact between a reducing agent and a high temperature exhaust gas to promote partial oxidation of the reducing agent. SOLUTION: The exhaust emission control device includes a bypass passage 7 branching from an exhaust passage 5 upstream of the control device 6 and connected again to the exhaust passage upstream of the control device; a reducing agent ejection device 11 for ejecting the reducing agent into the bypass passage; a bypass flow control valve 8 for controlling the flow of exhaust gas in the bypass passage; an aperture setting means 16 for the bypass flow control valve whose aperture is preset according to the operating condition of the engine so that the time needed for the reducing agent ejected from the ejection device to reach the control device is equal to or longer than a predetermined time; and a control means 16 for driving the ejection device to eject the reducing agent according to information from operating condition detecting means 17 and 18 when the temperature detected by a bypass temperature detecting means 14 is equal to or higher than a predetermined value and for controlling the bypass flow control valve in accordance with the information of the aperture setting means.