Method for monitoring an SCR system

摘要

A method for detecting whether an injector with a valve controlled by a PWM signal of an SCR system is at least partially clogged, the system including a pump, or a positive-displacement pump, driven by a motor and pressure of which is controlled by a controller that continuously measures the pressure and/or another parameter characteristic of energy transmitted by the motor to the pump. According to the method, during normal operation of the SCR system, specific portions of one of the measurements are compared with equivalent portions stored in a memory.

主权项

1. A method for detecting whether an injector with a valve controlled by a pulse width modulation (PWM) signal of a selective catalytic reduction (SCR) system is at least partially clogged, the system including a pump driven by a motor and pressure of the pump is controlled by a controller that continuously measures the pressure and/or another parameter characteristic of energy transmitted by the motor to the pump, the method comprising:
during normal operation of the SCR system, comparing specific portions of one of the measurements with equivalent portions stored in a memory; and deducing whether the injector is at least partially clogged from the comparing, wherein the controller measures an average value of speed, if the pump is pressure regulated, or of the pressure if the pump is speed regulated under given operating conditions, compares this value with an average value stored previously in the memory, and deduces whether the injector is at least partially clogged therefrom, and wherein the controller first measures the average value of speed or the pressure with a closed injector and for a given setpoint pressure or speed; next, measures an increase in speed or in pressure obtained by opening the injector at a given metering rate; and then compares this value with an average value stored previously in the memory and deduces whether the injector is at least partially clogged therefrom.