Abstract:
A system for storing an additive solution for a vehicle engine, said system comprising a tank for storing said additive solution, a pumping module for pumping said additive solution in the tank and an electrical heating device for heating the additive solution inside the tank when freezing conditions are detected, said electrical heating device being associated with electrical connecting lines for electrical supply of the heating device, wherein the heating device comprises at least an heating module provided in a blind pocket integral with the lower wall of the tank, said pocket opening outside the tank and projecting inside the internal volume of the tank from the lower wall and said electrical connecting lines for electrical supplying of the heating device being fully provided on the outside of the tank.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of EP Application Serial No. 12305424.9 filed Apr. 11, 2012. 
       TECHNICAL FIELD 
       [0002]    The disclosure relates to an additive tank system for a vehicle exhaust gas handling system. 
       BACKGROUND 
       [0003]    New legislation that targets the reduction of pollutant emissions from motor vehicles lead to systems for eliminating nitrogen oxides NO x  from exhaust gases of vehicles. One of the technologies developed, known as SCR for “Selective Catalytic Reduction”, consists in injecting into the exhaust circuit, a solution containing a precursor of ammonia (generally urea) which chemically reduces the NO x  to nitrogen. The vehicles are therefore provided with an additive tank and a pump for injecting the precursor when needed. 
       SUMMARY 
       [0004]    A system for storing an additive solution for a vehicle engine includes a tank for storing the additive solution, a pump for pumping the additive in the tank and an electrical heating device for heating the additive solution inside the tank, at least when freezing conditions are detected. The electrical heating device may be associated with electrical connecting lines for electrical supply of the heating device, and the heating device may include a heating module provided in a pocket carried by the tank, such as on or in a lower wall of the tank. The pocket may open outside the tank and project inside the internal volume of the tank, for example from the lower wall, and the electrical connecting lines for electrical supplying of the heating device may be fully provided on the outside of the tank. 
         [0005]    According to at least some implementations, the device may comprise a plurality of heating modules, the heating modules may include PTC heaters, and the device may comprise a reserve pot with the pump provided inside the reserve pot and wherein the heating modules cover at least a portion of the wall of the reserve pot. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The following detailed description of exemplary embodiments and best mode will be set forth with reference to the accompanying drawings, in which: 
           [0007]      FIG. 1  is a perspective view of the outside of one implementation of an additive tank; 
           [0008]      FIG. 2  is a perspective view of a lower portion of the tank of  FIG. 1 ; 
           [0009]      FIG. 3  is a partial sectional view of the bottom part of the tank; 
           [0010]      FIGS. 4 and 5  are fragmentary exploded views of heating modules before insertion in corresponding pockets of the tank; 
           [0011]      FIG. 6  is a fragmentary external view of a lower wall of the tank; 
           [0012]      FIG. 7  is a graph illustrating the current applied to the heating device and the evolution of temperature respectively at the bottom of a pot in the tank, in the mid height of the pot and outside the pot; 
           [0013]      FIG. 8  is a fragmentary, external bottom view of an implementations of an additive tank; 
           [0014]      FIG. 9  is a partial sectional and exploded view of the bottom part of the tank; 
           [0015]      FIG. 10  is a partial vertical sectional view of the same bottom part of the tank; and 
           [0016]      FIG. 11  is another partial sectional view of the bottom part of an implementation of a tank. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0017]    Referring in more detail to the drawings,  FIG. 1  illustrates a tank system  10  that includes an additive tank  100 , a module  200  for pumping the additive, a heating device  300 , and electrical connecting lines  400  for supplying the heating device  300 . The tank  100  can be made from a great number of technologies. Preferentially the tank  100  is made from two injection molded half shells, an upper one  102  and a lower one  104 , welded or otherwise connected together on their adjacent parts or seam  106 . The tank  100 , after welding of the two shells  102  and  104 , may be considered to have an upper wall  110 , a lower wall  112  and a side wall  114  connecting the upper wall  110  and the lower wall  112 . In use the upper and the lower walls  110  and  112  are horizontal while the side wall  114  is vertical. 
         [0018]    The upper wall  110  may be provided with a filling interface through which liquid is added to the tank  100 , and which may include a screw cap  120 , a vent  130  and a flange  140  which supports the module  200  for pumping the additive. The filling interface  120  and vent  130  may be of conventional construction and will not be described in detail. 
         [0019]    The module  200  for pumping the additive may include a pump  210  located inside the tank  100  and may include the flange  140  that supports the module. The pump  210  for pumping the additive may include any kind of pump compatible with urea. For example, the pump  210  may be formed by an electrically driven rotating pump or a solenoid dosing pump. Such a solenoid dosing pump comprises generally a piston which is moved by a magnetic force issued by the solenoid so as to alternatively draw additive into a pumping chamber and expel the additive outside said pumping chamber. 
         [0020]    The flange  140  is provided both with one or more electrical connector(s)  142  for electrically supplying the pump  210  and one or more hydraulic connection(s)  144  in connection with the output of the pump. More precisely the pump  210  may be located inside a reserve pot  160  that may be formed integral with and in the lower wall  112  of the tank. Thus the pump  210  is vertically integrated in the tank in this implementation, although other orientations may be utilized. The coil or solenoid of the pump  210  (when a solenoid pump is used) may be used as an additional heating device for cavitation prevention. The flange  140  may also integrate an electronic dosing module suitable for controlling the operation of the solenoid dosing pump  210 . 
         [0021]    According to the specific embodiment illustrated on the enclosed figures, the pot  160  is made by a generally cylindrical wall  161  so that the horizontal cross section of the pot  160  is about circular. The inside volume of the pot  160  is in communication with the volume of the tank  100  outside the pot  160  by any controlling means suitable for allowing free filling up of the pot  160  from the tank (i.e. free transfer of additive from the tank  100  towards inside the pot  160 ), while limiting draining of the pot  160  (i.e. limiting transfer of additive form inside the pot  160  towards the tank  100 ). For example such controlling means may be a cylindrical labyrinth  162  integral with the wall  161  and in connection on a one side with the inside volume of the pot  160  and in connection on the other side with the volume of the tank outside said pot  160 . 
         [0022]    The first embodiment illustrated on  FIGS. 3 to 6  will be first described. This embodiment is intended to be representative of at least certain concepts but is not intended to limit the scope of the disclosure. 
         [0023]    As indicated above, the heating device  300  may include at least a heating module  310  provided in a blind pocket  170  carried by or integral with (i.e. integrally formed in) the lower wall  112  of the tank  100 . In this implementations, the pocket  170  projects inside the internal volume of the tank  100  from the lower wall of the tank as illustrated on  FIG. 3  and opens outside the tank on the bottom side of the tank. The heating device  300  may be placed inside blind pockets which do not open inside the tank  300 , so that the heating device is fully isolated from urea and consequently there is no risk of corrosion of the heating device  300  by the urea and no specific anti-corrosion sheathing is needed. Instead of being formed in the lower wall, the blind pocket may be provided in another structure sealed to or otherwise carried by the lower wall, for example, on a flange that supports the pump and is coupled to the bottom wall of the tank, as opposed to (or in addition to) the upper wall. In addition, the pocket may project toward or near the bottom wall of the tank from, for example, the upper wall  110  or side wall  114  of the tank. 
         [0024]    The heating device  300 , in at least certain implementations, may include a plurality of heating modules  310 ,  320 ,  330  and  340  dispatched on the lower wall  112  of the tank so as to generally cover the wall  161  of the pot  160 . According to the specific embodiment illustrated on the enclosed figures, the heating device  300  comprises a plurality of heating modules ( 310 ,  320 ,  330 ) regularly angularly dispatched around the lateral wall  161  of the pot  160  and one or more additional heating modules  340  provided on the outside surface of the bottom wall of the pot  160 . More precisely according to the specific embodiment illustrated on the enclosed  FIGS. 3 to 6 , the heating device  300  comprises 3 heating modules  310 ,  320 ,  330  angularly dispatched around the wall  161  of the pot  160  and an additional heating module  340  provided on the outside surface of the bottom wall of the pot  160 . 
         [0025]    The heating modules  310 ,  320  and  330  are provided in respective blind pockets  170 ,  172 ,  174  that may be integral with the wall  161  of the pot  160  (see  FIG. 3 ). Said pockets  170 ,  172 ,  174  project inside the tank  100  from the bottom wall  112 . Each pocket defines a generally parallelepiped internal chamber receiving a heating module  310 ,  320  or  330 . 
         [0026]    In one form, the heating modules  310 ,  320 ,  330  and  340  comprise Positive Temperature Coefficient (PTC) heaters  314 ,  324 ,  334  and  344 . PTC heating means are well-known. PTC heating elements may be made from ceramic, such as ceramic based on barium titanate. When a voltage is placed across a PTC, current will flow and begin to heat the PTC. Initially, the resistance drops, allowing more current to flow and thus begins to heat more quickly. PTC heaters are effective low cost solutions providing highly efficient source of heat in a very small enclosure.  FIG. 7  illustrates one representative heating arrangement which shows the temperature of a mid height of the pot, the pot bottom and an area outside the pot, over time. The chart shows, among other things, that the pot bottom heats very quickly to facilitate melting urea near the bottom of the tank and the inlet of the pump  210 . 
         [0027]    As illustrated on the enclosed  FIGS. 2 to 6  the PTC heaters  314 ,  324 ,  334  and  344  may each be provided between two metal electrodes  312 ,  316 ;  322 ,  326 ;  332 ,  336 ;  342 ,  346 , such as aluminum or copper electrodes. One of said electrodes  312 ,  322 ;  332  is directly in contact with the outside surface of the wall  161  of the pot  160 . The electrode  342  is in contact with the outside surface of the bottom wall of the pot  160 . A resilient spring  318 ,  328 ,  338 , is provided between the other electrode  316 ,  326   336  and the internal surface of the receiving pocket so as to exert a pressure upon the stacks of electrodes and PTC heaters. 
         [0028]    The electrodes  312 ,  316 ;  322 ,  326 ;  332 ,  336  may generally have a parallelepiped shape. The electrodes  342 ,  346  are generally circular although other shapes may be used. As illustrated on the enclosed figures, electrodes  312 ,  316 ;  322 ,  326 ;  332 ,  336 ;  342 ,  346  have a cross section larger than the PTC heaters  314 ,  324 ,  334  and  344 . 
         [0029]    A cover may be fixed on a circular rib  113  that may be formed integral with the lower surface of the lower wall  112 , after electrical connection of the heating modules  300  so as to protect the heating device  300 . Such a cover is not illustrated on the enclosed figures. A spring similar to the springs  318 ,  328 ,  338  may be inserted between the PTC heater  344  and the cover. 
         [0030]    Moreover, as indicated above, the electrical connecting lines  400  for electrical supplying of the heating device  300  are, in at least some implementations, fully provided on the outside of the tank  100  so that they are not exposed to the urea within the tank. Such connecting lines  400  extend from a connector  142  provided on the flange  140  and each one of the PTC modules  310 ,  320 ,  330  and  340 . Said connecting lines  400  being placed outside the tank  300 , they are fully isolated from urea and consequently there is no risk of corrosion of said connecting lines  400  by the urea, without needing any specific anti-corrosion sheathing. 
         [0031]    The second embodiment illustrated in  FIGS. 8 to 11  will be now described. According to the second embodiment illustrated on  FIGS. 8 to 11 , the heater device  300  is provided in a bottom chamber  150  formed on or near the external surface of the lower wall  112 , as well as in a plurality of blind pockets  170  in communication with said chamber  150 , and provided around the wall  161  of the pot  160 . The chamber  150  is preferentially inside a circular rib  113  integral with the lower surface of the lower wall  112  and a cover  190 . An annular seal  194  is provided between a collar  192  of the cover  190  and the lower wall  112  of the tank  100 . 
         [0032]    The heater device  300  in this implementation comprises a plurality of PTC heaters  354 , such as 3 PTC heaters  354 , provided inside the chamber  150  between a bottom contact plate  356  and an heater plate  352 . The heater plate  352  is adjacent the lower wall  112 . In at least some forms, the heater plate  352  has a circular shape and is made from aluminum or copper or other suitably thermally conductive material. 
         [0033]    The contact plate  356  is adjacent the cover  190 . The contact plate  356  may be a ring including stamped parts  357  forming an elastic or biasing mechanism(s) which urges the PTC heaters  354  and the heater plate  352  against the lower surface of the lower wall  112  so as to optimize the heat transfer from the heater plate  352  to the lower wall  112 . Contact plate  356  and parallel heater plate  352  are electrodes for electrical supplying of the PTC heaters  354  from the connecting lines  400 . 
         [0034]    Moreover the heater device illustrated in  FIGS. 8 to 11  includes heat sinks  360  linked with the heater plate  352  and inserted in the pockets  170  provided around the wall  161  of the pot  160 . The heat sinks  360  may be made from parallelepiped blocks connected by any means, such as screwing or welding, to the heater plate  352 . The heat sinks  360  extend vertically and transversely to the horizontal heater plate  352 . The heat sinks  360  are provided in the pockets around the wall  161  of the pot  160  so as to cover as far as possible a majority of the surface of the wall  161 . The heat sinks  360  may be urged against the outside surface of the wall  161  of the pot  160  by respective resilient springs  362  inserted in the pockets  170 . 
         [0035]    According to a specific and not limiting embodiment, the heater device comprises 6 pockets  170  regularly spaced around the wall  161  of the pot  160  and 6 heat sinks  360  with 6 springs  362  inserted respectively in each of said pockets  170 . According to the embodiment illustrated on  FIGS. 8 to 11 , preferentially each PTC heater  354  is provided in a cradle  370  linked to two respective spacers  372 ,  374 . 
         [0036]    The spacers  372 ,  374  define the distance between the contact plate  356  and the heater plate  352 . The cradle  370  is suitable to authorize a displacement of the PTC heaters  354  transversely to the contact plate  356  so as to warrant contact between said PTC heaters  354  and the heater plate  352 . The spacers  372 ,  374  are preferentially made from thermoplastic material so as to form an electric insulation between the contact plate  356  and the heater plate  352 . 
         [0037]    Preferentially the contact plate  356  is an open ring so as to clear a zone wherein is implemented a level sensor  145  and a temperature sensor  146 . 
         [0038]    The system provides an additive tank wherein no metallic part of the heating devices, neither the heating elements themselves nor the electrical wires for the heating elements, is inside the tank. This provides a high level of robustness and low risk of failure which may otherwise occur due to corrosion. The system may be cost effective, such as by using aluminum simple shapes instead of either stainless steel parts or overmolded aluminum heater. Further, with the heating device components not located within the tank, assembly of the heating devices is simplified. Very good thermal conduction to the tank may be easily achieved with aluminum or other materials of suitable thermal conductivity. Further, the heather may be self thermally regulated by use of, for example, PTC heating elements. With the components outside of the tank and not corroding within the tank, there is no risk of altering the urea quality. Optimization of the blind pockets using an injection molded tank enables automatic optimized shapes for the insertion of heater components, without needing any kind of additional machining 
         [0039]    While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. It is not intended herein to mention all the possible equivalent forms or ramifications of the invention. It is understood that the terms used herein are merely descriptive, rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention.