| 主权项 |
1. An exhaust purification system of an internal combustion engine in which an exhaust purification catalyst is arranged in an engine exhaust passage, a hydrocarbon feed valve is arranged in the engine exhaust passage upstream of the exhaust purification catalyst, precious metal catalysts are carried on an exhaust gas flow surface of the exhaust purification catalyst, basic exhaust gas flow surface parts are formed around the precious metal catalysts, the exhaust purification catalyst has a property of reducing NOx which is contained in an exhaust gas if making a concentration of hydrocarbons which flow into the exhaust purification catalyst vibrate by within a predetermined range of amplitude and by within a predetermined range of period and has a property of being increased in storage amount of NOx which is contained in the exhaust gas if making a vibration period of the hydrocarbon concentration longer than the predetermined range, wherein, as rich control for making an air-fuel ratio of the exhaust gas which flows into the exhaust purification catalyst rich, cylinder rich control for generating rich air-fuel ratio combustion gas in a cylinder and exhaust rich control for feeding hydrocarbons from the hydrocarbon feed valve to make air-fuel ratio of the exhaust gas rich can be used, if a speed of a vehicle is lower than a predetermined speed when the air-fuel ratio of the exhaust gas which flows into the exhaust purification catalyst should be made rich, the exhaust rich control is performed if the exhaust rich control is possible, and, if the speed of the vehicle is larger than the predetermined speed when the air-fuel ratio of the exhaust gas which flows into the exhaust purification catalyst should be made rich, the cylinder rich control is performed if the cylinder rich control is possible. |
