Method for regulating a pump of an SCR system

A method for regulating a motor-driven pump of an SCR system having an injection mode and a purge mode, the method comprising:

• delivering a pressure with the pump, the pump being subjected to a hydraulic torque in relation to this pressure and also to a resistive torque and being driven by an electric motor comprising coils supplied with a current and developing a torque in relation to this current;
• and
• regulating the pump speed in the injection mode, by using a means for measuring the current in the coils of the motor, a regulator of the overall current consumed by the motor, and a model of the relation between the overall current, the part Cr of said resistive torque due to dry frictions, and the pressure, wherein said model uses the equation K1·I=K2·p+Cr, wherein K1 and K2 are constants, I is the overall current, p is the pressure, and Cr is an estimate of said part of the resistive torque due to dry frictions obtained by rotating the pump under no-load conditions at different speeds and by measuring the associated current;
• and
• regulating the motor-driven pump based on the model using the equation.