Control method and control device for exhaust gas control apparatus

Abstract: It is an object of the invention to provide a technology for appropriately recovering a decreased HC oxidizing ability of rhodium (Rh), in an exhaust gas control apparatus including a catalyst that contains rhodium (Rh) and a particulate filter (5). In this exhaust gas control apparatus, rich-spike control is prohibited and a NOx storage reduction catalyst is placed in a reduction atmosphere during a period in which a temperature of the NOx storage reduction catalyst is equal to or higher than a predetermined temperature, in a course of decreasing the temperature of the NOx storage reduction catalyst after a PM trapping ability forcible recovery process of the particulate filter (5) is completed. Thus, the decreased HC oxidizing ability of rhodium (Rh) is recovered. (end of abstract)