Patent ID: 8555619

Claim:
A method of controlling an exhaust system, comprising steps of: determining whether a regeneration condition of a nitrogen oxide purification catalyst or a regeneration condition of a trapping filter is satisfied or not; injecting a predetermined amount of fuel for a predetermined time period as a reducing agent when either or both of the regeneration conditions are satisfied; determining whether a first temperature difference between a front side and a rear side of a fuel cracking catalyst is larger than or equal to a first predetermined value; determining whether a second temperature difference between a front side and a rear side of the nitrogen oxide purification catalyst is larger than or equal to a second predetermined value; determining whether an oxygen concentration difference between an upstream of the fuel cracking catalyst and a downstream of the nitrogen oxide purification catalyst is larger than a third predetermined value; and changing a regeneration target temperature of the trapping filter when the first temperature difference is smaller than the first predetermined value, the second temperature difference is larger than or equal to the second predetermined value, the oxygen concentration difference is larger than the third predetermined value, and a purification ratio of the nitrogen oxide purification catalyst is larger than or equal to a fourth predetermined value, wherein the trapping filter is disposed at an exhaust line; the nitrogen oxide purification catalyst is disposed at a downstream side of the trapping filter; and the fuel cracking catalyst is disposed between the injector and the trapping filter at the exhaust line.