Exhaust purifying device of internal combustion engine

An exhaust purifying device for an internal combustion engine, comprising:

• an upstream catalyst and a downstream catalyst arranged in series with each other and housed in a common casing disposed in an engine exhaust passage, wherein:
• the upstream catalyst comprises a NOx storage-reduction catalyst that absorbs NOx contained in incoming exhaust gas when the air-fuel ratio of the incoming exhaust gas is lean, and releases and reduces the absorbed NOx when the air-fuel ratio of the incoming exhaust gas becomes rich, and the downstream catalyst comprises one of a three-way catalyst and a NOx storage-reduction catalyst;
• the upstream catalyst has a higher oxidizing capability than the downstream catalyst, and the downstream catalyst has a higher reducing capability than the upstream catalyst;
• the upstream catalyst achieves a higher oxidizing capability than the downstream catalyst and achieves a lower reducing capability than the downstream catalyst by a multi-layer structure including an upper layer and a lower layer, each of the upper layer and the lower layer of the upstream catalyst contains both of a noble-metal catalyst and a NOx absorbent comprising at least one selected from alkali metals, alkaline earths, and rare earths,
• the upper layer of the upstream catalyst contains, as the noble-metal catalyst, at least one selected from platinum (Pt), palladium (Pd), osmium (Os), and gold (Au);
• the lower layer of the upstream catalyst contains, as the noble-metal catalyst, at least one selected from rhodium (Rh), iridium (Ir), and ruthenium (Ru),
• the downstream catalyst has a multi-layer structure including an upper layer and a lower layer, and the upper layer has a higher reducing capability than the lower layer, and the lower layer has a higher oxidizing capability than the upper layer:
• rhodium (Rh) is used as a noble-metal component of the upper layer of the downstream catalyst;
• and
• platinum (Pt) is used as a noble-metal component of the lower layer of the downstream catalyst.