Patent ID: 7114328

Claim:
A control method for an exhaust gas purifying system in which a NOx occlusion reduction type catalyst, including a catalytic metal and an NOx occluding substance, is installed in an exhaust passage of an engine, comprising: executing a restore processing against a sulfur poisoning of said NOx occlusion reduction type catalyst, by performing a lax rich control for controlling an air/fuel ratio of the exhaust gas to a theoretical air/fuel ratio or to a value slightly lower than the theoretical air/fuel ratio, when said NOx occlusion reduction type catalyst is heated to a sulfur purge temperature or above; setting an excess air factor of the exhaust gas of 0.95 to 1.0; and performing regeneration of the NOx occlusion reduction type catalyst when the excess air factor of 0.8 to 0.95 is maintained at the catalyst inlet.