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.