| 摘要 |
It is intended to maintain the purification ability as a whole. For this purpose, an exhaust gas purification apparatus comprises a three-way catalyst; an NH3-producing catalyst; and a selective catalytic reduction NOx catalyst; the catalysts being provided in this order at an exhaust gas passage; and the exhaust gas purification apparatus further comprising a control device which carries out rich spike for lowering an air-fuel ratio of an exhaust gas from a lean air-fuel ratio to a predetermined rich air-fuel ratio; wherein the control device lengthens an interval of the rich spike if a temperature of the three-way catalyst is lower than a threshold value as a lower limit value of a temperature of activation as compared with if the temperature of the three-way catalyst is not less than the threshold value. |
