Exhaust emission control device of internal combustion engine

摘要

An exhaust gas purification device of an internal combustion engine arranging a catalyst (22) suitable for reduction of NOx in exhaust gas by ammonia in the presence of excess oxygen in an engine exhaust passage (21), said device comprising: feeding means (31,32,33) for feeding a liquid (30) containing an ammonia generating compound to the catalyst; feed control means (40) for controlling the amount of feed of the liquid, decision means (40) for deciding if the temperature of the catalyst is in an ammonia generating compound storage region, or if the temperature of the catalyst is in an ammonia release region which causes the ammonia to be released a little at a time from the stored ammonia generating compound; calculating means (40) for calculating the amount of the ammonia generating compound stored in the catalyst per unit time and the amount of the ammonia released from the catalyst per unit time; estimating means (40) for estimating the amount of storage of the ammonia generating compound stored in the catalyst on the basis of a result of calculations by said calculating means; wherein said feed control means (40) stops the of feed of the liquid when the estimated amount of storage of the ammonia generating compound exceeds a predetermined maximum amount of storage.