Fuel Addition Control Method Applied to Exhaust Emission Purifier of Internal Combustion Engine and Exhaust Emission Purifier

摘要

An exhaust emission purifier able to suppress overheats of an exhaust emission purifying catalyst and execute fuel addition promptly when fuel addition to the exhaust emission purifying catalyst is requested is provided. In the exhaust emission purifier of an internal combustion engine including exhaust emission purifying catalyst of purifying exhaust emission of an internal combustion engine and a fuel addition valve of adding fuel from upstream of the exhaust emission purifying catalyst, cycles are repeated in order that the exhaust emission purifying catalyst is to be regulated at a target temperature, the cycle being a combination of an addition period during which fuel is added from the fuel addition valve and a halt period during which fuel addition is halted, and the fuel addition valve is manipulated such that the halt period is disposed so as to sandwich the addition period in the cycle. The length of the pre-addition halt period disposed before the addition period is varied in accordance with the temperature of the exhaust emission purifying catalyst at the start point of the cycle.