| 摘要 |
An exhaust gas purification apparatus for an internal combustion engine comprises a NOx trap catalyst disposed in an exhaust passage of the internal combustion engine and a control unit. At a purification timing, the control unit determines a space velocity of exhaust gas and selectively switches between a first air-fuel ratio control mode for controlling the air-fuel ratio of the exhaust gas to a rich air-fuel ratio with no need to decrease a concentration of oxygen in the exhaust gas when the determined space velocity is lower than or equal to a threshold value, and selects a second air-fuel ratio control mode for not only controlling the air-fuel ratio of the exhaust gas to a rich air-fuel ratio but also making the concentration of oxygen in the exhaust gas lower than that of the first air-fuel ratio control mode when the determined space velocity is higher than the threshold value.
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