| 摘要 |
A NOx occlusion and reduction catalyst 7 is arranged in an exhaust path 2 of an engine 1 to purify NOx in the exhaust gas. An electronic control unit (ECU) 30 of the engine operates the engine in an operating mode in which the exhaust gas increases in temperature with the air-fuel ratio thereof kept rich each time a predetermined amount of SOx is occluded in the catalyst 7, and executes the SOx poisoning restoration process for releasing SOx from the catalyst 7. The ECU controls the engine air-fuel ratio in such a manner that the H2 concentration in the exhaust gas detected by the H2 sensor arranged in the exhaust path upstream of the catalyst 7 is in a predetermined range. As a result, an appropriate amount of hydrogen is supplied to the catalyst 7 during the SOx poisoning restoration process. Thus, an appropriate amount of hydrogen is supplied to the catalyst 7 during the SOx poisoning restoration process, so that the H2S generation is suppressed while at the same time executing the SOx poisoning restoration process efficiently. |
