Piping for an scr circuit of a motor vehicle

Abstract

A piping for an SCR circuit of a motor vehicle comprising a pipe to feed a solution comprising urea, an electrical resistor surrounding the pipe to heat the solution containing urea, and a layer of a material having a flexural stiffness higher than that of the pipe, in which the layer is tubular and houses at least partially the electrical resistor and the pipe.

1 . A piping for an SCR circuit of a motor vehicle comprising a pipe ( 10 ) to feed a solution containing urea, an electrical resistor ( 11 ) surrounding said pipe ( 10 ) to heat the solution containing urea, and a layer ( 12 ) of a material having a flexural stiffness higher than that of said pipe ( 10 ), characterised in that said layer ( 12 ) is tubular, pre-formed and houses at least partially with radial play said electrical resistor ( 11 ) and said pipe ( 10 ). 
     
     
         2 . The piping according to  claim 1 , characterised in that the ratio between the flexural stiffness of said layer ( 12 ) and that of the unit comprising said pipe ( 10 ) and said electrical resistor ( 11 ) is greater than  20 . 
     
     
         3 . The piping according to  claim 1 , characterised in that said radial play is not constant. 
     
     
         4 . The piping according to  claim 1 , characterised in that an axis of said layer ( 12 ) tends to maintain a two-dimensional or three-dimensional path after it has been preformed. 
     
     
         5 . The piping according to  claim 1 , characterised by comprising a first and a second connector (C) comprising a body and respective electrical terminals at least partially embedded in the body, said terminals being electrically connected to said electrical resistor ( 11 ). 
     
     
         6 . The piping according to  claim 1 , characterised in that said pipe ( 10 ) is multilayer and comprises an external layer of an electrically and thermically conductive polymeric material having a surface resistivity lower than 10̂6 Ohm/square. 
     
     
         7 . The piping according to  claim 1 , characterised in that said pipe ( 10 ) is formed by a single layer made of a polyamide material. 
     
     
         8 . The piping according to  claim 7 , characterised in that said layer ( 12 ) is a single layer made of a PA12. 
     
     
         9 . The piping according to  claim 1 , characterised in that said electrical resistor ( 11 ) comprises at least one filament ( 14 ;  15 ) of an electrically conductive material and a plurality of yarns made of an electrically insulating material woven with said at least one filament ( 14 ;  15 ). 
     
     
         10 . The piping according to  claim 9 , characterised in that said at least one filament ( 14 ;  15 ) is covered with a sheath made of an electrically insulating material. 
     
     
         11 . A method for manufacturing a piping according to  claim 1 , comprising the following steps:
 preforming said tubular layer ( 12 );   producing a preassembled assembly comprising said pipe ( 10 ) and said electrical resistor ( 11 );   inserting with radial play said preassembled assembly in said tubular layer ( 12 ) after said layer ( 12 ) has been preformed.   
     
     
         12 . The method according to  claim 11 , characterised in that, after said step of inserting, said radial play is not constant. 
     
     
         13 . The method according to  claim 12 , characterised in that, after said step of inserting, said preassembled assembly ( 10 ,  11 ) is floating within said layer ( 12 ).