EXHAUST GAS PURIFICATION SYSTEM FOR INTERNAL COMBUSTION ENGINE

摘要

This exhaust gas purification system for an internal combustion engine is provided with an exhaust gas purifying catalyst that reacts NOX with modified hydrocarbons contained in exhaust gas. The exhaust gas purifying catalyst is supported by a noble metal catalyst, and has a basic exhaust flow surface section formed thereon. The exhaust gas purifying catalyst has the characteristic of reducing NOX when the concentration of hydrocarbons that are to flow into the exhaust gas purifying catalyst is oscillated at an amplitude within a predetermined range and a cycle within a predetermined range. The retention capacity at which the NOX in exhaust gas is kept above the basic exhaust flow surface section of the exhaust gas purifying catalyst is estimated, and when the retention capacity is less than a predetermined retention capacity determination value, the concentration of hydrocarbons that are to flow into the exhaust gas purifying catalyst is increased.