Method for controlling fluid injected quantity in a NOx reduction system employing a SCR catalyst

An internal combustion engine, comprising:

• a NOx reduction system employing a Selective Catalytic Reduction (SCR) catalyst;
• an Emission Fluid (EF) injector adapted to inject said EF to reach said SCR catalyst;
• and
• a control unit configured to:
• determine a required quantity of EF for the SCR catalyst at a given time;
• activate an EF injection if the required quantity of EF is at least equal to a threshold quantity, wherein said threshold quantity is a minimum injected fluid quantity that provides a substantially linear behavior for a given EF injector;
• store in memory of the control unit the required quantity of EF if the required quantity of EF is less than said threshold quantity and after a period determining a further required quantity of EF to be added to the required quantity of EF to determine a new required quantity of EF;
• continuously update the new required quantity of EF until the new required quantity of EF is at least equal to said threshold quantity;
• and
• activate the EF injection of the new required quantity of EF.

A non-transitory computer readable medium embodying a computer program product, said computer program product comprising:

• a program, for controlling Diesel Emission Fluid (DEF) injected quantity in a NOx reduction system employing a Selective Catalytic Reduction (SCR) catalyst, and a DEF injector adapted to inject said DEF to reach said SCR catalyst, the program configured to:
• determine a required quantity of DEF for the SCR catalyst at a given time;
• activate a DEF injection if the required quantity of DEF is at least equal to a threshold quantity, wherein said threshold quantity is a minimum injected fluid quantity that provides a substantially linear behavior for given DEF injector;
• store, in memory of an Electronic Control Unit (ECU), the required quantity of DEF if the required quantity of DEF is less than said threshold quantity and after a period determining a further required quantity of DEF to be added to the required quantity of DEF to determine a new required quantity of DEF;
• continuously update the new required quantity of DEF until the new required quantity of DEF is at least equal to said threshold quantity;
• and
• activate the DEF injection of the new required quantity of DEF.