Patent ID: 7086222

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 urea 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 urea 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 urea stored in the catalyst along with the rise if 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 urea contained in the liquid fed to the catalyst inside the catalyst and releases almost no ammonia from the stored urea, 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 urea; said feed control means controlling the amount of feed of the liquid so that the amount of the urea fed is made more that the equivalent ratio=1 when the temperature of the catalyst is in the ammonia release region at the time of the steady operating state of the engine.