Exhaust gas purification method for an internal combustion engine

Exhaust gas purifying method for an internal combustion engine for cleaning the exhaust gases of the internal combustion engine by means of an exhaust gas purification unit, which is disposed in an exhaust system of the internal combustion engine, with a filter provided in the exhaust system for collecting contained in the exhaust solids and a NOx absorbent catalyst on the inflow side is mounted on the filter for absorbing contained in the exhaust NOx at the time of lean operation and releasing and reducing the absorbed NOx when a rich operation is performed, the method comprising a step of varying the exhaust gas air / fuel ratio of the engine between rich and lean at intervals of a predetermined period when the temperature of the exhaust gas cleaning unit reaches a predetermined temperature, characterized in that: the predetermined temperature is a necessary for the regeneration of the filter temperature and when festges tellt is that, based on the exhaust gas temperature downstream of the filter, a rate of combustion of the solids on the filter is too high, a time period, the exhaust gas air / fuel ratio in a predetermined ... in the