| 摘要 |
<p>PROBLEM TO BE SOLVED: To eliminate the poisoning of SOx of a catalyst in the downstream side by effectively raising temperature of the catalyst in the downstream side while avoiding temperature rise of a catalyst of the upstream side. SOLUTION: This exhaust emission control device is provided with a first front three-dimensional catalyst 21 of a first exhaust passage 5a connected to a first air- cylinder group, a second front three-dimensional catalyst 22 of a second exhaust passage 5b connected to a second air-cylinder group, and the rear three-dimensional catalyst 23 installed in an exhaust passage 5c for collecting the exhaust of both the exhaust passages. In the condition for raising temperature of the rear three-dimensional catalyst 23, a control unit 11 sets the air-fuel ratio of the exhaust at one front catalyst side close to a rich side in comparison with the theoretical air-fuel ratio, and sets the air-fuel ratio of the exhaust at the other front catalyst side close to a lean side in comparison with the theoretical air-fuel ratio. The unburned fuel passed through the front catalysts 21, 22 and the oxygen flow into the rear three-dimensional catalyst 23 so as to activate the reaction of the rear three-dimensional catalyst 23 of temperature rise thereof, and discharge and reduction of SOx is thereby performed.</p> |
