EXHAUST PURIFICATION DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To provide an exhaust purification device for an internal combustion engine capable of curbing an increase in an ammonia concentration in exhaust when performing an exhaust heating-up process.SOLUTION: An exhaust passage 28 of an engine 1 has an SCR catalyst 41 which reduces NOx by using ammonia derived from urea water and a urea water addition valve 230 which adds the urea water. A control device 80 performs a heating-up process to increase a temperature of exhaust to a predetermined temperature by supplying engine fuel to a flow of the exhaust at an upstream side of the SCR catalyst. The control device 80 also performs a heating-up restraining process, during a period when the temperature of a wall surface of the exhaust passage 28 is lower than the predetermined temperature making urea deposit easy to be accumulated, in a manner that makes a temperature increase in the exhaust during the heating-up process slower than the period when the temperature of the wall surface of the exhaust passage is higher than the predetermined temperature making the urea deposit difficult to be accumulated.