Exhaust gas treatment unit and measuring instrument for ascertaining a concentration of a urea-water solution

Abstract

An exhaust gas treatment unit for conversion and in particular reduction of nitrogen oxide compounds in an exhaust gas stream of a combustion system, in particular a Diesel internal combustion engine, having a storage unit for storing a urea-water solution and a metering unit for metering the urea-water solution into the exhaust gas stream, and at least one measuring instrument for ascertaining a concentration of the urea-water solution in the storage unit with an electronic evaluation unit with which the concentration of the urea-water solution can be ascertained without major effort and economically favorably, so that an exact metering of urea into the exhaust gas stream can be achieved. At least one measuring instrument is provided in the treatment unit, for ascertaining a concentration of the urea-water solution in the storage unit with an electronic evaluation unit, and the storage unit of the measuring instrument includes at least one pressure sensor for ascertaining a pressure.

I claim:  
     
         1 . A measuring instrument for ascertaining a concentration of a urea-water solution ( 5 ) in a storage unit ( 6 ) comprising an electronic evaluation unit ( 15 ), the storage unit ( 6 ) including at least one pressure sensor ( 14 ) for ascertaining a pressure.  
     
     
         2 . The measuring instrument of  claim 1  wherein the storage unit ( 6 ) further comprises at least one temperature sensor ( 16 ) for ascertaining a temperature.  
     
     
         3 . The measuring instrument of  claim 1  wherein the evaluation unit ( 15 ) further comprises at least one timer for ascertaining the time.  
     
     
         4 . The measuring instrument of  claim 2  wherein the evaluation unit ( 15 ) further comprises at least one timer for ascertaining the time.  
     
     
         5 . The measuring instrument of  claim 1  wherein the evaluation unit ( 15 ) has an electronically stored characteristic curve of pressure.  
     
     
         6 . The measuring instrument of  claim 2  wherein the evaluation unit ( 15 ) has an electronically stored characteristic curve of pressure, and curve of temperature.  
     
     
         7 . The measuring instrument of  claim 4  wherein the evaluation unit ( 15 ) has an electronically stored characteristic curve of pressure, and curve of time.  
     
     
         8 . The measuring instrument of  claim 1  wherein the evaluation unit ( 15 ) further comprises a volume measuring element ( 9 ), disposed on an outflow element of the storage unit ( 6 ), for measuring the volume of the urea-water solution ( 5 ) removed from the storage unit ( 6 ).  
     
     
         9 . The measuring instrument of  claim 1  wherein the storage unit ( 6 ) has at least one regulatable, closable opening for pressure compensation.  
     
     
         10 . The measuring instrument of  claim 9  wherein the elevation unit  15  further comprises at least one timer, and wherein the timer ascertains at least one duration of an opening phase of the opening.  
     
     
         11 . The measuring instrument of  claim 9  wherein the opening includes at least one overpressure and/or underpressure valve.  
     
     
         12 . The measuring instrument of  claim 1  wherein the storage unit ( 6 ) has at least one fill level sensor ( 17 ) for ascertaining a fill level.  
     
     
         13 . The measuring instrument of  claim 1  wherein at least the pressure sensor ( 14 ) is embodied as a fill level sensor ( 17 ).  
     
     
         14 . An exhaust gas treatment unit for conversion and in particular reduction of nitrogen oxide compounds in an exhaust gas stream ( 1 ) of a combustion system, in particular a Diesel internal combustion engine, comprising 
 a storage unit ( 6 ) for storing a urea-water solution ( 5 )    a metering unit ( 7 ,  8 ,  9 ,  10 ,  11 ,  12 ,  13 ,  15 ) for metering the urea-water solution ( 5 ) into the exhaust gas stream ( 1 ),    an electronic evaluation unit ( 15 ), and    at least one measuring instrument for ascertaining a concentration of the urea-water solution ( 5 ) in the storage unit ( 6 ) with the electronic evaluation unit ( 15 ).    
     
     
         15 . The exhaust gas treatment unit of  claim 14  wherein the measuring instrument comprises at least one pressure sensor ( 14 ) for ascertaining a pressure.  
     
     
         16 . The exhaust gas treatment unit of  claim 14  wherein the measuring instrument comprises at least one pressure sensor ( 14 ) for ascertaining a pressure, but at least one temperature sensor for ascertaining a temperature.  
     
     
         17 . The exhaust gas treatment unit of  claim 14  wherein the measuring instrument comprises at least one pressure sensor ( 14 ) for ascertaining a pressure, but at least one timer for ascertaining the time.  
     
     
         18 . The exhaust gas treatment unit of  claim 14  further comprising a flowthrough element for delivering a gaseous fluid to the exhaust gas stream ( 1 ) disposed at a regulatable, closable opening of the storage unit ( 6 ).  
     
     
         19 . A vehicle having an exhaust gas treatment unit for conversion and in particular reduction of nitrogen oxide compounds in an exhaust gas stream ( 1 ) of a combustion system, in particular a Diesel internal combustion engine, wherein the exhaust gas treatment unit is the exhaust gas treatment unit defined in  claim 14 .  
     
     
         20 . A method for ascertaining a concentration of a urea-water solution ( 5 ) in a storage unit ( 6 ) with an electronic evaluation unit ( 15 ), and at least one measuring instrument in the storage unit ( 6 ).