Patent ID: 8133444

Claim:
An exhaust gas purification system for an internal combustion engine comprising: an NOx selective catalytic reduction catalyst that is provided in an exhaust passage of the internal combustion engine to reduce NOx in exhaust gas using ammonia as a reducing agent; urea supply unit for supplying urea to said NOx selective catalytic reduction catalyst; a particulate filter that is provided in said exhaust passage to trap particulate matter in the exhaust gas; and filter temperature raising unit for executing a filter temperature raising control to raise the temperature of said particulate filter; and an adsorbed urea quantity estimation unit for estimating the quantity of urea adsorbed in said NOx selective catalytic reduction catalyst, wherein when the quantity of urea adsorbed in said NOx selective catalytic reduction catalyst estimated by said adsorbed urea quantity estimation unit at a time when the condition for executing said filter temperature raising control is satisfied is equal to or larger than a first specific adsorption quantity, supply of urea to said NOx selective catalytic reduction catalyst by said urea supply unit is stopped, and said filter temperature raising control is executed by said filter temperature raising unit after a specific period of time has elapsed since the time of stoppage of supply of urea to said NOx selective catalytic reduction catalyst by said urea supply unit.