Metering apparatus and method for operating it

Abstract

In a metering apparatus for the metered introduction of a first medium into an exhaust gas system of an internal combustion engine, which includes a conditioning apparatus in which also a second medium is introduced via a dispensing apparatus which is connected to the conditioning apparatus and via which the first medium and the second medium are introduced into the exhaust gas system, a supply unit for supplying a third medium, which is different from the second medium in its physical properties and/or its chemical composition, is connected to the conditioning apparatus for cleaning of the conditioning apparatus and the dispensing apparatus from constituent parts of the first medium by the third medium or a mixture of the second and the third medium.

1 . A metering apparatus for the metered dispensing of a first medium into an exhaust gas system of an internal combustion engine, comprising
 a conditioning apparatus ( 2 ) to which a first medium (HWL) and a second medium can be supplied,   a dispensing apparatus ( 3 ) which is connected to the conditioning apparatus ( 2 ) and via which at least one of the first medium (HWL) and the second medium can be introduced into the exhaust gas system for cleaning at least one of the conditioning apparatus ( 2 ) and the dispensing apparatus ( 3 ) from constituent parts of the first medium (HWL) by the second medium, and   means for supplying a third medium to the conditioning apparatus ( 2 ) for cleaning of the conditioning apparatus ( 2 ) and the dispensing apparatus ( 3 ) from constituent parts of the first medium by the third medium or mixtures of the second and the third medium   the third medium differing from the second medium in its physical properties or its chemical composition.   
     
     
         2 . The metering apparatus as claimed in  claim 1 , wherein the second medium is a gas and the third medium is a solvent, in which at least constituent parts of the first medium (HWL) can be dissolved. 
     
     
         3 . The metering apparatus as claimed in  claim 1 , wherein a metering element ( 12 ) is arranged in a main line ( 10 ) of the conditioning apparatus ( 2 ), and the feed of the third medium is provided upstream of the metering element ( 12 ). 
     
     
         4 . The metering apparatus as claimed in  claim 3 , wherein a sensor apparatus ( 20 ) for sensing a measured variable is arranged in the main line ( 10 ) of the conditioning apparatus ( 2 ), and a feeder unit of the third medium is activated if the measured variable deviates from a reference value or when a threshold value is reached. 
     
     
         5 . A method for operating a metering apparatus for the metered dispensing of a first medium into an exhaust gas system of an internal combustion engine, comprising
 a conditioning apparatus ( 2 ) to which a first medium (HWL) and a second medium can be supplied,   a dispensing apparatus ( 3 ) which is connected to the conditioning apparatus ( 2 ) and via which at least one of the first medium (HWL) and the second medium can be introduced into the exhaust gas system for cleaning at least one of the conditioning apparatus ( 2 ) and the dispensing apparatus ( 3 ) from constituent parts of the first medium (HWL) by the second medium, and   means for supplying a third medium to the conditioning apparatus ( 2 ) for cleaning of the conditioning apparatus ( 2 ) and the dispensing apparatus ( 3 ) from constituent parts of the first medium by the third medium or mixtures of the second and the third medium   the third medium differing from the second medium in its physical properties or its chemical composition.   said method comprising the step of feeding the third medium to the conditioning apparatus ( 2 ) intermittently from time to time.   
     
     
         6 . The method as claimed in  claim 5 , wherein a feed of the third medium is introduced into the conditioning apparatus ( 2 ) upstream of a metering element ( 12 ) which is arranged in a main line ( 10 ) of the conditioning apparatus ( 2 ). 
     
     
         7 . The method as claimed in  claim 6 , wherein a measured variable is monitored in the main line ( 10 ) of the conditioning apparatus ( 2 ) or the dispensing apparatus ( 3 ) and the third medium is introduced in the event of at least one of a change with respect to a reference value by a predefinable amount and the reaching of a predefined threshold value. 
     
     
         8 . The method as claimed in  claim 5 , wherein the second medium and the third medium are alternately introduce within a predetermined time period. 
     
     
         9 . The method as claimed in  claim 5 , wherein a feed of the first medium (HWL) is reduced when at least one of the second medium and the third medium is supplied to the metering apparatus.