Patent ID: 6959540

Claim:
An exhaust gas purification device of an internal combustion engine arranging a catalyst suitable for reduction of NOx in exhaust gas by ammonia in the presence of excess oxygen in an engine exhaust passage, said device comprising: feeding means for feeding a liquid containing an ammonia generating compound to the catalyst; feed control means for controlling the amount of feed of the liquid, the catalyst storing inside it at least part of the ammonia generating compound contained in the liquid fed to the catalyst and having the function of causing the release of ammonia a little at a time from the ammonia generating compound stored in the catalyst along with the rise of temperature of the catalyst and reducing the NOx in the exhaust gas by the ammonia released, decision means for deciding if the temperature of the catalyst is in an ammonia generating compound storage region which stores the ammonia generating compound contained in the liquid fed to the catalyst inside the catalyst and releases almost no ammonia from the stored generating compound, 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, the feed control means feeding a sufficient amount of the liquid required to the catalyst in the form of pulses at time intervals when the temperature of the catalyst is in the ammonia generating compound storage region, said sufficient amount of the liquid being necessary to store in the catalyst in advance enough of the ammonia generating compound for releasing the amount of ammonia required when the temperature of the catalyst becomes the ammonia release region, the feed control means feeding the liquid continuously into the catalyst when the temperature of the catalyst is in a state where ammonia is released all at once from the catalyst.