US Patent 7908844 Exhaust purification device of internal combustion engine

In an internal combustion engine, a first exhaust passage and second exhaust passage branched from an exhaust passage are provided. An NOx storing reduction catalyst and a particulate filter are arranged in each exhaust passage. For example, when NOx should be released from the NOx storing reduction catalyst in the first exhaust passage, fuel is added from a fuel addition valve in the state with exhaust gas allowed to flow into only the first exhaust passage, while when the added fuel sticks to the NOx storing reduction catalyst, the first exhaust control valve is temporarily closed and the exhaust gas is made a rich air-fuel ratio.