EXHAUST PURIFICATION METHOD AND EXHAUST PURIFICATION APPARATUS OF INTERNAL COMBUSTION ENGINE

摘要

In an internal combustion engine, an exhaust passage is provided with a NO_x storing and decomposing catalyst ( 20 ). When burning fuel under a lean air-fuel ratio, the nitrogen monoxide is adsorbed by the NO_x storing and decomposing catalyst ( 20 ) and disassociated. At this time, the disassociated oxygen is held in the form of oxygen ions O^- on the NO_x storing and decomposing catalyst ( 20 ). By making the air-fuel ratio rich and purging part of these oxygen ions O^-, the remaining oxygen ions O^- are also purged. Due to this, the NO_x purification performance of the NO_x storing and decomposing catalyst ( 20 ) is restored.