Device for supplying ammonia to a reduction catalyst arranged in an exhaust system of an internal combustion engine

Abstract

In a device for supplying ammonia (NH 3 ) to a reduction catalytic converter arranged in an exhaust system of an internal combustion engine comprising a container for storing a precursor body capable of generating ammonia when heated by a heating device disposed in the container for the thermolytic decomposition of the precursor material, the heating device includes a heating surface arranged adjacent the precursor body and means are provided for biasing the precursor material body in firm contact with the heating device surface for direct heat transfer to the precursor body, and the heating device is connected to a control unit for controlling the energization of the heating device depending on the NH 3 requirements of the reduction catalytic convertor.

1 . A device ( 1 ;  30 ;  38 ) for supplying ammonia (NH 3 ) to a reduction catalyst arranged in an exhaust duct of an exhaust system of an internal combustion engine, said device comprising a container ( 2 ;  31 ,  31 ′;  33 ;  44 ) for storing a precursor body ( 3 ,  3 ′,  3 ″;  39 ) capable of generating ammonia (NH 3 ) when subjected to heat, said container ( 2 ;  31 ;  31 ′;  33 ;  44 ) having an outlet ( 10 ;  35 ;  48 ) connected to a supply line ( 12 ;  49 ) extending to said exhaust duct and a heating device ( 4 ,  42 ) for heating areas of said precursor body ( 3 ,  3 ′,  3 ″;  39 ) for the thermolytic decomposition thereof resulting in the generation of an NH 3  containing gas, said heating device ( 4 ,  42 ) having a heating surface ( 6 ) arranged adjacent said precursor body ( 3 ,  3 ′,  3 ″;  39 ) for a direct heat transfer to said precursor body ( 3 ,  3 ′,  3 ″;  39 ) and said heating device ( 4 ,  42 ) being connected to a control unit for controlling the energization of the heating device ( 4 ,  42 ).  
   
   
       2 . A device according to  claim 1 , wherein said precursor body ( 3 ,  3 ′,  3 ″;  39 ) contained in the container is in the form of a solid, pressed rod-shaped body.  
   
   
       3 . A device according to  claim 2 , wherein biasing means ( 19 ,  20 ,  21 , D) are provided for biasing the body ( 3 ,  3 ′,  3 ″;  39 ) into firm contact with the heating surface ( 6 ) of the heating device ( 4 ,  42 ).  
   
   
       4 . A device according to  claim 3 , wherein the container ( 2 ) is divided by a piston ( 15 ) into two sections ( 16 ,  17 ) which are separated from each other by the piston ( 15 ) in a gas-tight manner, one of the container sections ( 16 ) including the NH 3  precursor ( 3 ,  3 ′,  3 ″) and the heating device ( 4 ) and the other container section ( 17 ) including said biasing means which comprises a mechanical pressure generator device ( 18 ).  
   
   
       5 . A device according to  claim 4 , wherein said biasing means includes an activator ( 23 ) which is arranged outside the container ( 2 ) and coupled to the biasing structure ( 18 ) disposed within the container ( 2 ).  
   
   
       6 . A device according to  claim 3 , wherein the container ( 2 ) is divided by a piston ( 15 ) into two sections ( 16 ,  17 ) which are separated from each other in a gas-tight manner, one of the container sections ( 16 ) including the NH 3  precursor ( 3 ,  3 ′,  3 ″) and the heating device ( 4 ) and the other container section ( 17 ) including a gas under pressure for biasing the NH 3  precursor in contact with the heating device.  
   
   
       7 . A device according to  claim 3 , wherein said container is divided into two sections ( 16 ,  17 ) by a rolling piston ( 15 ).  
   
   
       8 . A device according to  claim 1 , wherein said heating device ( 4 ,  42 ) comprises a heating plate ( 5 ,  46 ) arranged in the area of the outlet ( 10 ;  35 ;  48 ) of the container ( 2 ;  31 ,  31 ′;  33 ;  44 ) and the precursor body ( 3 ,  3 ′,  3 ″;  39 ) is biased into firm contact with the heating plate ( 5 ,  46 ).  
   
   
       9 . A device according to  claim 8 , wherein on the side of the heating plate ( 46 ) remote from the precursor body ( 39 ) an electric radiation heating device ( 43 ,  43 ′,  43 ″) is arranged.  
   
   
       10 . A device according to  claim 9 , wherein the side of the heating plate ( 46 ) adjacent the NH 3  precursor ( 39 ) is provided with a nep-structured surface.  
   
   
       11 . A device according to  claim 9 , the heating plate ( 46 ) consists of a transparent glass-ceramic material.  
   
   
       12 . A device according to  claim 1 , wherein the container ( 2 ;  31 ,  31 ′;  33 ) with its content of components of the device ( 1 ,  30 ) is removably supported and the outlet ( 10 ;  35 ) of the container ( 2 ;  31 ,  31 ′;  33 ) is connected to the supply line ( 12 ) leading to the exhaust duct by a coupling structure ( 13 ,  13 ′).  
   
   
       13 . A device according to  claim 1 , wherein the heating device comprises several independently controllable heating elements, each being provided with its own NH 3  precursor storage structure.  
   
   
       14 . A device according to  claim 1 , wherein the ammonia supply device ( 30 ) comprises several containers ( 31 ,  31 ″), each including its own heating device.  
   
   
       15 . A device according to  claim 1 , wherein the NH 3  supply line ( 49 ) extending from the device includes a controllable valve ( 50 ).  
   
   
       16 . A device according to  claim 15 , wherein the controllable valve ( 50 ) includes a stationary valve part ( 57 ) forming a valve seat and a movable valve plate ( 54 ) which forms the heat exchange surface of a Peltier element ( 51 ) for cooling and, respectively heating the movable valve plate ( 54 ).