Patent ID: 7716918
Filing Date: 2010-05-18
Classification: B01D,F01N,F02B,F02D,Y02T

Abstract:
1. In a regeneration control of purification system for nitrogen oxides in exhaust gas, having a catalyst unit carrying a nitrogen oxides occlusion-reduction type catalyst, which occludes nitrogen oxides when an air/fuel ratio in exhaust gas is in a lean condition, and releases and reduces the occluded nitrogen oxides when an air/fuel ratio in exhaust gas is in a rich condition, and performing the regeneration control to restore a capacity of the catalyst unit for occluding nitrogen oxides when it is determined that an estimated amount of nitrogen oxides occluded in the catalyst unit reaches a predetermined determination value: a method of exhaust gas purification comprising: determining completion of the oxygen release on the basis of an oxygen concentration in a downstream of the catalyst unit in said first rich control; and performing a second rich control such that an amount of reductant supplied in order to reduce the nitrogen oxides released from a nitrogen oxides occlusion-reduction type catalyst is calculated and an air/fuel ratio in the exhaust gas becomes a second target air/fuel ratio determined on the basis of the calculated amount of the reductant, when the oxygen release is determined to have been completed.