Method for Operating a Reducing Agent Supply System

Abstract

A method for operating a reducing agent supply system for supplying an exhaust aftertreatment system of a motor vehicle is provided. In normal metering operation of the reducing agent supply system an at least approximately continuous air stream and a pulsed reducing agent stream are produced and are released at least partially via the nozzle into the exhaust line. In a cleaning operation for cleaning the reducing agent supply system an air stream formed from a number of air stream pulses and a reducing agent stream formed from a number of reducing agent stream pulses are produced and supplied to the nozzle means. The method can be used in particular in supply systems in which aqueous urea solution is used as reducing agent.

1 - 10 . (canceled) 
     
     
         11 . A method for operating a reducing agent supply system for supplying an exhaust aftertreatment system of a motor vehicle with a reducing agent for emission control, in which an air stream and a reducing agent stream are supplied to a nozzle opening into an exhaust line, the method comprising:
 in normal metering operation of the reducing agent supply system, producing an approximately continuous air stream and a pulsed reducing agent stream at least partially releasing the produced approximately continuous air stream and the pulsed reducing agent stream via the nozzle into the exhaust line; and   in a cleaning operation for cleaning the reducing agent supply system, producing an air stream formed from a number of air stream pulses and a reducing agent stream formed from a number of reducing agent stream pulses and supplying the produced air stream and reducing agent stream to the nozzle.   
     
     
         12 . The method as claimed in  claim 11 , further comprising:
 determining a back pressure in a line of the reducing agent supply system for transporting the air stream to the nozzle; and   activating the cleaning operation upon exceeding a pre-settable, first upper pressure threshold value.   
     
     
         13 . The method as claimed in  claim 11 , further comprising:
 deactivating an activated cleaning operation when
 a back pressure in a line of the reducing agent supply system for transporting the air stream to the nozzle drops below a pre-settable lower pressure threshold value, 
 after exceeding a pre-settable total value of amount of reducing agent of the reducing agent stream formed from reducing agent stream pulses, or 
 after exceeding a pre-settable duration from a beginning of the cleaning operation. 
   
     
     
         14 . The method as claimed in  claim 12 , further comprising:
 deactivating an activated cleaning operation when
 a back pressure in a line of the reducing agent supply system for transporting the air stream to the nozzle drops below a pre-settable lower pressure threshold value, 
 after exceeding a pre-settable total value of amount of reducing agent of the reducing agent stream formed from reducing agent stream pulses, or 
 after exceeding a pre-settable duration from the beginning of the cleaning operation. 
   
     
     
         15 . The method as claimed in  claim 11 , wherein the cleaning operation includes a first operating mode in which a sequence of reducing agent stream pulses and air stream pulses is produced such that a particular reducing agent stream pulse overlaps in time with a particular air stream pulse. 
     
     
         16 . The method as claimed in  claim 12 , wherein the cleaning operation includes a first operating mode in which a sequence of reducing agent stream pulses and air stream pulses is produced such that a particular reducing agent stream pulse overlaps in time with a particular air stream pulse. 
     
     
         17 . The method as claimed in  claim 13 , wherein the cleaning operation includes a first operating mode in which a sequence of reducing agent stream pulses and air stream pulses is produced such that a particular reducing agent stream pulse overlaps in time with a particular air stream pulse. 
     
     
         18 . The method as claimed in  claim 15 , wherein one of a rising or a falling edge of a reducing agent stream pulse occurs during an air stream pulse. 
     
     
         19 . The method as claimed in  claim 16 , wherein one of a rising or a falling edge of a reducing agent stream pulse occurs during an air stream pulse. 
     
     
         20 . The method as claimed in  claim 17 , wherein one of a rising or a falling edge of a reducing agent stream pulse occurs during an air stream pulse. 
     
     
         21 . The method as claimed in  claim 15 , wherein an air stream pulse occurs completely during a reducing agent stream pulse. 
     
     
         22 . The method as claimed in  claim 16 , wherein an air stream pulse occurs completely during a reducing agent stream pulse. 
     
     
         23 . The method as claimed in  claim 17 , wherein an air stream pulse occurs completely during a reducing agent stream pulse. 
     
     
         24 . The method as claimed in  claim 11 , wherein the cleaning operation includes a second operating mode in which a number of successive reducing agent stream pulses is produced when the air stream is switched off and a number of successive air stream pulses is produced when the reducing agent stream is switched off. 
     
     
         25 . The method as claimed in  claim 12 , wherein the cleaning operation includes a second operating mode in which a number of successive reducing agent stream pulses is produced when the air stream is switched off and a number of successive air stream pulses is produced when the reducing agent stream is switched off. 
     
     
         26 . The method as claimed in  claim 13 , wherein the cleaning operation includes a second operating mode in which a number of successive reducing agent stream pulses is produced when the air stream is switched off and a number of successive air stream pulses is produced when the reducing agent stream is switched off. 
     
     
         27 . The method as claimed in  claim 15 , further comprising:
 determining a back pressure in a line of the reducing agent supply system for transporting the air stream to the nozzle;   activating the first operating mode of the cleaning operation upon exceeding a pre-settable first upper pressure threshold value;   activating a second operating mode of the cleaning operation upon exceeding a pre-settable second upper pressure threshold value, the second upper pressure threshold value being higher than the first upper pressure threshold value,   wherein when the air stream is switched off in the second operating mode of the cleaning operation a number of successive reducing agent stream pulses is produced and when the reducing agent stream is switched off in the second operating mode of the cleaning operation a number of successive air stream pulses is produced.   
     
     
         28 . The method as claimed in  claim 16 , further comprising:
 determining a back pressure in a line of the reducing agent supply system for transporting the air stream to the nozzle;   activating the first operating mode of the cleaning operation upon exceeding a pre-settable first upper pressure threshold value;   activating a second operating mode of the cleaning operation upon exceeding a pre-settable second upper pressure threshold value, the second upper pressure threshold value being higher than the first upper pressure threshold value,   wherein when the air stream is switched off in the second operating mode of the cleaning operation a number of successive reducing agent stream pulses is produced and when the reducing agent stream is switched off in the second operating mode of the cleaning operation a number of successive air stream pulses is produced.   
     
     
         29 . The method as claimed in  claim 27 , wherein a cleaning operation of the first operating mode succeeds a cleaning operation of the second operating mode. 
     
     
         30 . The method as claimed in  claim 28 , wherein a cleaning operation of the first operating mode succeeds a cleaning operation of the second operating mode.