Patent ID: 8302382

Claim:
An exhaust gas purification system for an internal combustion engine, comprising: a NOx storage reduction catalyst provided in an exhaust passage for the internal combustion engine; a reducing agent supply device that supplies a reducing agent to the NOx storage reduction catalyst from a position upstream of the NOx storage reduction catalyst; an EGR apparatus that recirculates part of exhaust gas containing the reducing agent to the internal combustion engine, wherein the EGR apparatus includes an EGR passage through which exhaust gas flown out from the NOx storage reduction catalyst flows into an intake passage of the internal combustion engine; a rich spike control device that executes a rich spike control that recovers exhaust gas purification performance of the NOx storage reduction catalyst, by controlling the reducing agent supply device so that the reducing agent supply device supplies the reducing agent to temporarily decrease an air-fuel ratio of the exhaust gas that flows into the NOx storage reduction catalyst to a predetermined target inflow air-fuel ratio; and a base air-fuel ratio control device that decreases a base air-fuel ratio in the internal combustion engine to a predetermined spike base air-fuel ratio, when the EGR apparatus recirculates the exhaust gas, and the rich spike control is executed, wherein the predetermined spike base air-fuel ratio is lower than the base air-fuel ratio when the rich spike control is not executed and is higher than the predetermined target inflow air-fuel ratio.