Exhaust gas purification system and method for internal combustion engine

摘要

An exhaust gas purification system for an internal combustion engine includes rich spike execution means for executing rich spike control in which the air-fuel ratio of an exhaust gas flowing into an NOx storage reduction catalyst is lowered to a target rich air-fuel ratio by supplying fuel to the exhaust gas while reducing oxides stored in the NOx storage reduction catalyst. The rich spike execution means executes the rich spike control (S 108) when the fuel injection amount has increased at a predetermined fuel increase rate or more by a predetermined fuel increase amount or more (S102, S105). It is possible to restrict the excessive amount of fuel to be supplied to the exhaust gas in rich spike control, and to sufficiently reduce oxides stored in the NOx storage reduction catalyst.