Device for metering a urea soulution

Abstract

A device for metering urea solutions permitting a reliable reduction of nitrogen oxides in the exhaust gas of an internal combustion engine is provided. This is achieved by the fact that the device for metering the urea solution includes a sensor unit for monitoring one or more physical state variables of an enzyme-free Urea solution.

1 . A device for metering a urea solution, in particular for spraying the urea solution into the exhaust gas stream of an internal combustion engine, 
 wherein a sensor unit is provided for monitoring one or more physical state variables of an enzyme-free urea solution using a physical measuring sensor ( 3 ,  6 ,  9 ).    
   
   
       2 . The device as recited in  claim 1 , 
 wherein the measuring sensor ( 3 ,  6 ) is designed for detecting an electric state variable.    
   
   
       3 . The device as recited in one of the preceding claims, wherein the measuring sensor ( 3 ,  6 ,  7 ) is designed for detecting the pH, the dielectric constant, and/or the conductance of the enzyme-free urea solution.  
   
   
       4 . The device as recited in one of the preceding claims, wherein the measuring sensor ( 3 ,  6 ,  7 ) includes at least two electrodes.  
   
   
       5 . The device as recited in one of the preceding claims, wherein at least one electrode ( 3 ,  6 ,  7 ) has a structure for increasing the surface area.  
   
   
       6 . The device as recited in one of the preceding claims, wherein two electrodes ( 3 ,  6 ) have an intermeshing comb-like structure.  
   
   
       7 . The device as recited in one of the preceding claims, wherein at least one third electrode ( 7 ) is provided for detecting at least one second electric state variable.  
   
   
       8 . The device as recited in one of the preceding claims, wherein the measuring sensor ( 9 ) is designed for detecting a physicomechanical state variable.  
   
   
       9 . The device as recited in one of the preceding claims, wherein the measuring sensor ( 9 ) is designed for measuring the viscosity and/or density of the enzyme-free urea solution.  
   
   
       10 . The device as recited in one of the preceding claims, wherein a vibration generator ( 9 ) is provided.  
   
   
       11 . The device as recited in one of the preceding claims, wherein the vibration generator includes a quartz oscillator ( 9 ) and/or a piezoelectric crystal.  
   
   
       12 . The device as recited in one of the preceding claims, wherein a sensor unit ( 1 ) having a measuring sensor ( 3 ,  6 ,  7 ) for an electric state variable of the urea solution and having a measuring sensor ( 9 ) for a physicomechanical state variable is provided, an analyzer unit being provided for determining the urea concentration from the two measured values.  
   
   
       13 . The device as recited in one of the preceding claims, wherein a temperature sensor is provided.  
   
   
       14 . The device as recited in one of the preceding claims, wherein a filling level sensor is provided for a storage container.  
   
   
       15 . The device as recited in one of the preceding claims, wherein the filling level sensor is a measuring sensor according to one of the preceding claims.  
   
   
       16 . The device as recited in one of the preceding claims, wherein a plurality of filling level sensors is provided.  
   
   
       17 . An internal combustion engine having catalytic exhaust gas treatment, 
 wherein a device for metering a urea solution according to one of the preceding claims is provided.