EXHAUST PURIFICATION SYSTEM OF INTERNAL COMBUSTION ENGINE

摘要

An exhaust purification system of an internal combustion engine is provided with an exhaust purification catalyst where NOX which is contained in exhaust gas and modified hydrocarbons react. The exhaust purification catalyst carries precious metal catalysts and is formed with a basic exhaust gas flow surface part. The exhaust purification catalyst has the property of reducing NOX if making the concentration of hydrocarbons which flow into the exhaust purification catalyst vibrate by within a predetermined range of amplitude and within a predetermined range of period. The system estimates the holding ability by which the NOX in the exhaust gas is held on the basic exhaust gas flow surface part of the exhaust purification catalyst and, when the holding ability becomes less than a predetermined judgment value of the holding ability, makes the concentration of hydrocarbons which flow into the exhaust purification catalyst rise.