EXHAUST GAS PURIFICATION METHOD AND EXHAUST GAS PURIFICATION SYSTEM

摘要

An exhaust gas purification system has a NOx purification catalyst (22), and the catalyst (22) purifies NOx when the air-fuel ratio of exhaust gas of an internal combustion engine (E) mounted on a vehicle is in a lean state and recovers purification ability when the air-fuel ratio is in a rich state. The system performs recovery control for setting the exhaust gas to a rich air-fuel ratio state in order to recover the NOx purification ability of the NOx purification catalyst (22), and at the time of retardation of the vehicle, both fuel system rich control and air-intake system rich control are used in the recovery control. The recovery control can be performed without worsening of drive comfort of the vehicle and with deterioration of fuel consumption involved in the recovery control suppressed.