| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine, which can accurately estimate the poisonous substance mass occluded in NOx occlusion reduction catalyst. SOLUTION: This device is equipped with NOx occlusion reduction catalyst occluding NOx and poisonous substance when exhaust gas is in a lean condition, and with an occluded quantity estimating means (step 509) which computes (step 503) the absorbing quantity per hour of poisonous substance into NOx occlusion reduction catalyst and the emitting quantity per hour of poisonous substance out of the catalyst, at least based on the condition of exhaust gas, and estimates the occluded quantity of poisonous substance of the catalyst. And until the specified period of time elapses since the start of restoring treatment for emitting the poisonous substance out of occlusion reduction catalyst, the computed emitting quantity per hour of poisonous substance can thereby be reduced to a great extent (step 504 through 508).</p> |
