Purge phase control strategy for a selected catalytic reduction system

Abstract

The method according to the invention is a method for controlling the purging of a sélective catalytic réduction System ( 1 ) for a vehicle. The sélective catalytic réduction System ( 1 ) has a pump ( 4 ) for reducing agent ( 3 ), at least one supply line ( 5 ) supplying reducing agent ( 3 ) to an exhaust line ( 10 ) of the vehicle, and a purge fluid suction device. The method is characterized in that it involves determining a purge duration as a fonction of a state of fill of the supply line ( 5 ) prior to activation of the purge phase, and in that the method forther comprises the updating of the purge duration during purging.

1 . A purge control method for a selective catalytic reduction system for a vehicle, the selective catalytic reduction system having a pump for a reducing agent, at least one line for supplying reducing agent to an exhaust line of the vehicle, and a device for suctioning purge fluid, the method comprising
 determining a purge duration as a function of a filling state of the supply line before the activation of a purge of the selective catalytic reduction system, and updating of the purge duration during the purge.   
     
     
         2 . The method according to  claim 1 , wherein the filling state of the supply line is determined by the percentage or the volume of reducing agent contained in the supply line for the reducing agent. 
     
     
         3 . The method according to  claim 1 , wherein the updating of the purge duration is a function of the state of contact of the pump with the air and/or of the pressure at the outlet of the pump. 
     
     
         4 . The method according to  claim 3 , wherein the state of contact of the pump with the air is determined using a measurement of the current consumed by the pump. 
     
     
         5 . The method according to  claim 4 , wherein the method additionally includes:
 determining the consistency between two of three pieces of data, the data comprising the purge duration, the measurement of the current consumed by the pump, and the measurement of the pressure at the outlet of the pump, and   performing a diagnosis on the state of operation of the elements of the selective catalytic reduction system.   
     
     
         6 . The method according to  claim 1 , wherein the step of determining the purge duration is also a function of the pressure at the device for suctioning purge fluid. 
     
     
         7 . The method according to  claim 1 , wherein the purge of the selective catalytic reduction system is activated as a function of at least one of the parameters selected from the temperature in the exhaust line of the vehicle or the filling level of a reservoir of reducing agent. 
     
     
         8 . The method according to  claim 1 , wherein the method additionally includes of calculating the filling state of the supply line throughout the entire purge, and recording of the filling state of the line when the purge is deactivated. 
     
     
         9 . The method according to  claim 1 , wherein an activation of the purge includes the sequential activation of the pump and of the suction device. 
     
     
         10 . The method according to  claim 1 , wherein a deactivation of the purge includes the sequential deactivation of the pump and of the suction device. 
     
     
         11 . The method according to  claim 9 , wherein the activation or deactivation sequence of the pump and of the suction device is predetermined. 
     
     
         12 . The method according to  claim 1 , wherein the suction device is an injector for the reducing agent or a valve. 
     
     
         13 . A selective catalytic reduction system for a vehicle, the selective catalytic reduction system including a pump for a reducing agent, at least one line for supplying the reducing agent to an exhaust line of the vehicle, a device for suctioning purge fluid, and; the controller being adapted to determine a purge duration as a function of a filling state of the supply line before the activation of a purge of the selective catalytic reduction system, and to update the purge duration during the purge. 
     
     
         14 . The selective catalytic reduction system according to  claim 13 , wherein the selective catalytic reduction system is incorporated in a vehicle.