EXHAUST EMISSION CONTROL DEVICE FOR ENGINE

摘要

PROBLEM TO BE SOLVED: To efficiently purify NOx by preventing excessive temperature increase of a catalyst due to CO and HC slips and HC adsorption while preventing degradation of fuel economy by prohibiting rich spike which produces no effect.

SOLUTION: The device is provided to an exhaust passage 30 of a diesel engine 20, and equipped with an NOx occlusion catalyst 41 which occludes NOx in exhaust gas flowing into the exhaust passage 30 and which is reduced when a rich air-fuel ratio is attained, a rich spike control part 70 in which rich spike control for provisionally controlling the air-fuel ratio to a rich side is executed every specified time, and an inlet temperature sensor 71 and outlet temperature sensor 72 for measuring temperature of the NOx occlusion catalyst 41. The rich spike control part 70 prohibits the rich spike control on the basis of temperatures measured by temperature sensors 71, 72.

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