EXHAUST EMISSION PURIFIER OF INTERNAL COMBUSTION ENGINE

摘要

An electronic controller (6) estimates the quantity of sulfur deposited in a filter (35) for purifying PM and NOx based on the operating state of an engine. On condition that an estimation value Sx is above a judgment value Smax, first regeneration processing for raising the temperature of the filter (35) up to a temperature a and discharging sulfur from the filter (35) by lowering the exhaust air fuel ratio is executed. When the number N of execution times of the first regeneration processing after execution of second regeneration processing is a judgment number of times A or more, the second regeneration processing for raising the temperature of the filter (35) up to a temperature ß(>a) and discharging sulfur from the filter (35) completely by lowering the exhaust air fuel ratio is executed separately from the first regeneration processing. The estimation value Sx is reset upon completion of the second regeneration processing. Even if separation between the actual quantity of deposited sulfur and its estimation value increases, it can be corrected and worsening of emission can be suppressed.