to recover the NOx absorbing ability of the NOx catalyst.
Thus, in the exhaust gas purifying apparatus using a lean NOx catalyst, the oxygen concentration of the exhaust gas needs to be decreased intermittently for purifying the NOx. As an example of a method of decreasing the oxygen concentration of the exhaust gas intermittently, a fuel supply into the exhaust gas can be adopted.
Sulfur oxides (SOx) produced by burning of a sulfur component, which is contained in the fuel, is also absorbed in the occlusion-reduction type NOx catalyst according to the same mechanism as in the case of NOx. The SOx thus absorbed in the catalyst is not easily emitted as compared to NOx, and is accumulated in the NOx catalyst. This is called sulfur poisoning (SOx poisoning). Inthe catalysts independently of the reducing agent supply device, a flow amount adjusting device that adjusts an amount of the exhaust gas flowing in the exhaust passages, and a temperature estimating device that estimates the temperatures of the catalysts. Further, the exhaust gas purifying apparatus for an internal combustion engine according to the first aspect of the invention includes a control device. In a case where the temperatures of the catalysts need to be raised, the control device selects a catalyst (the first catalyst) in which the exhaust gas flows, and allows a larger amount of the exhaust gas to flow in the selected catalyst than in the other catalysts (e.g. the second catalyst) by the flow amount adjusting device. In addition, the control device raises the temperature