EXHAUST GAS PURIFICATION CONTROL APPARATUS

In an exhaust gas purification control apparatus that includes a NOx storage reduction catalyst (NSR catalyst, or the like) provided in an exhaust system of an internal combustion engine and that carries out rich spike operation in the case where a NOx storage amount in the catalyst exceeds a first threshold, the rich spike operation is started at an exhaust gas air-fuel ratio that is leaner when the NOx storage amount in the catalyst exceeds a second threshold (M2) larger than the first threshold (M1) than when the NOx storage amount is smaller than or equal to the second threshold (M2). With the above configuration, it is possible to suppress the amount of NOx that is released from the catalyst, and it is possible to reduce the amount of flow of untreated NOx, with the result that it is possible to suppress deterioration of exhaust emission.