Abstract:
A container for a liquid has a container wall and at least one inner chamber for receiving the liquid. The container has at least one discharge line for discharging liquid located in the at least one inner chamber. The at least one discharge line at least reduces relative movements of regions of the container wall spaced apart from each other.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation, under 35 U.S.C. §120, of copending international application No. PCT/EP2011/050119, filed Jan. 6, 2011, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German patent application No. DE 10 2010 005 056.3, filed Jan. 20, 2010; the prior applications are herewith incorporated by reference in their entireties. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a vessel for a liquid, in particular a tank for a reducing agent such as for example an aqueous urea solution. Such vessels are used for storing a liquid in an automobile in order to supply the liquid according to demand to a consumer, in particular the exhaust line. 
         [0004]    It is known for such vessels or tanks to be provided with plastic and/or metal. For the continuous use of such vessels, it must however be taken into consideration that, aside from a low weight, a high degree of dimensional accuracy must also be maintained. The dimensional accuracy must be maintained because, in this way, it can be ensured that “bubble-free” delivery of liquid is possible when the tank is relatively empty. There are also a number of fill level monitoring components which realize a liquid level in relation to the bottom of the vessel. A change in the relative position of the fill level sensors in relation to the vessel bottom accordingly leads to an inaccurate measurement result. Such a change in the relative position can be prevented by a high degree of dimensional accuracy. 
         [0005]    With regard to the dimensional accuracy, however, it must be taken into consideration that such vessels are subject to ageing, which results in particular in deformation of the vessel, in particular bulges in the region of the tank bottom. 
       SUMMARY OF THE INVENTION 
       [0006]    Taking this as a starting point, it is an object of the present invention to specify a vessel which at least partially solves the problems highlighted with regard to the prior art. In particular, it is sought to specify a vessel which is lightweight and which likewise ensures a reliable extraction of liquid and/or a precise measurement of the (possibly very small) liquid quantity in the vessel. 
         [0007]    The vessel according to the invention for a liquid has a vessel wall and at least one interior space for accommodating the liquid. Furthermore, the vessel has at least one extraction line for extracting liquid situated in the at least one interior space, wherein the at least one extraction line at least reduces relative movements of spaced-apart regions of the vessel wall. 
         [0008]    The vessel is in particular a vessel for an aqueous liquid, in particular an aqueous urea solution. A vessel of this type may basically have a single interior space. It is however also possible for the interior space to be divided into a multiplicity of chambers, wherein here, the liquid can at least partially be exchanged between the chambers. The vessel now contains at least one extraction line which extends into the interior space and through the interior space. For this purpose, the at least one extraction line is connected directly and/or indirectly to at least one region of the vessel wall, but preferably to two regions of the vessel wall. The at least one extraction line is now arranged such that the freedom of movement of the two spaced-apart regions of the vessel wall is reduced or even substantially eliminated owing to the arrangement of the at least one extraction line. This also means, in other words, that those regions of the vessel wall which deform for example during the course of operation are fixed and supported by the at least one extraction line. For this purpose, the at least one extraction line may for example brace the two spaced-apart end regions against one another or, as a reinforcement, position the two spaced-apart regions relative to one another. For this purpose, the at least one extraction line extends for example between the two spaced-apart regions through the interior space of the vessel, so as to form an internal support. 
         [0009]    The extraction of liquid from the vessel takes place usually in a region of the vessel wall in the vicinity of the vessel bottom, because it is here that an extraction of liquid is possible even when there is a low liquid fill level in the vessel. Such a region of the vessel wall is preferably stabilized in the vessel according to the invention. The extraction pipe normally extends from such an extraction region of the vessel wall to an opening of the vessel or to a dosing unit arranged in the vessel or on the vessel. Relative movements between the extraction region of the vessel wall and an opening or a dosing unit for the liquid are thus reduced. 
         [0010]    With the solution proposed here, it is firstly possible for the vessel to be of relatively thin-walled design, which has considerable advantages with regard to the weight of a vessel of the type. At the same time, the at least one extraction line acts as a stabilizing element in order to permanently maintain the dimensional accuracy of the vessel. The conflict of aims highlighted in the introduction is resolved in a simple manner in this way. 
         [0011]    According to a refinement, it is also proposed that the at least one extraction line has a direction of extent and relative movements of spaced-apart regions of the vessel wall in the direction of extent are compensated. In this way, the at least one extraction line serves in particular for accommodating compressive forces or tensile forces, which arise owing to a deformation of the vessel, in particular with regard to the spaced-apart regions. In particularly preferred embodiments, the at least one extraction line may also be arranged such that it can accommodate or compensate forces and movements perpendicular to the direction of extent. 
         [0012]    It is also considered to be advantageous for the vessel wall to be formed with plastic and for the at least one extraction line to be formed with metal. With regard to the plastic, it must be noted that the plastic must in particular be suitable for accommodating aqueous urea solution. Considerable weight savings can be attained with a vessel wall composed of plastic. By contrast, the at least one extraction line is in this case composed of metal, such that the extraction line has greater strength and/or stiffness than the vessel wall and fixes the spaced-apart regions of the vessel wall with respect to one another. 
         [0013]    Furthermore, a vessel wall composed of plastic normally exhibits a considerably more pronounced thermal expansion movement than an extraction line composed of metal. The extent and the volume of the interior space of the vessel thus vary relatively significantly in the event of fluctuating temperatures. A (stable) metallic extraction pipe which defines the spacing between different regions of the vessel wall makes it possible to at least partially limit or prevent the change in the volume of the interior of the vessel. In particular, the extent of the vessel in a direction in which a fill level measurement is to take place can be reduced. 
         [0014]    According to a refinement of the invention, it is provided that a first region of the vessel wall and a second region of the vessel wall are formed opposite one another and a tubular extraction line supports the first region against the second region. The first region of the vessel wall is for example a vessel roof, whereas the second region of the vessel wall is the vessel bottom. The tubular form of the extraction line leads to a particularly dimensionally rigid form of the extraction line, and permits an integration of sensors, liquid lines, electric heaters or the like. 
         [0015]    Here, it is advantageous for the vessel wall to be fixed relative to the extraction line if at least one sensor for fill level determination is fastened to the extraction line. In this way, the relative position of the at least one sensor for fill level measurement with respect to the vessel bottom is precisely predefined. The fixing of the relative position is of crucial significance for the accuracy of the fill level measurement, because the fill level volume measured by the at least one sensor is situated between the vessel bottom and the sensor. A drop of the tank bottom thus does not have an effect on the measured fill level volume because the extraction pipe and the fill level sensor on the extraction pipe drop to the same extent. 
         [0016]    It is furthermore considered to be advantageous for the vessel wall to have a first receptacle and a second receptacle for fastening the at least one extraction line. Under some circumstances, it is advantageous for at least the receptacle to have fixing elements which are likewise more dimensionally rigid than the regions of the vessel wall. It is for example possible for metallic inserts to be provided on or in the vessel wall, which inserts interact with the extraction line. The metallic inserts may for example be jointly cast into a vessel wall formed from plastic, though may also be retroactively attached to a vessel wall of this type. The inserts may for example be of annular form and have closure elements. 
         [0017]    It is also proposed that the at least one extraction line be arranged in a lockable and unlockable manner in the vessel wall. This facilitates in particular servicing or repair of the vessel. Such a lockable and unlockable arrangement may be realized by releasable connecting devices or closure systems. A preferred closure element is for example a so-called bayonet closure. 
         [0018]    In another refinement, at least one flexible zone is provided at least adjacent to one of the regions of the vessel. The flexible zone is in particular formed so as to permit a relative movement between the at least one extraction line and the vessel only above a predefined internal pressure in the interior space. This applies in particular to a situation in which the stored liquid is exposed to extreme temperatures, such that an elevated gas pressure or ice pressure can hereby be compensated. Here, the flexible zones are preferably formed symmetrically with respect to the spaced-apart regions, for example in a circular arrangement around those regions of the vessel wall which are spaced apart from one another and which are fixed by the at least one extraction line. It is particularly preferable for the flexible zones to be formed from the same material as the vessel wall. 
         [0019]    It is preferable for a flexible zone to be formed adjacent to only one of the fixed regions. It is furthermore particularly preferable for the opposite fixed region to be of particularly rigid form, for example with reinforcements. The rigid region thus defines the position of the extraction pipe, and the oppositely arranged region with the flexible zone adapts its position to the position of the rigid region. The relative position of the two spaced-apart regions with respect to one another can thus be predefined particularly precisely even if for example thermal expansions or ageing of the vessel occurs. 
         [0020]    In this connection, it is particularly preferable for the at least one flexible zone to be formed concentrically around the at least one extraction line. It is accordingly also very particularly preferable for in each case one flexible zone, which runs (in closed form) concentrically around the extraction line, to be provided in those parts (regions) of the tank in or on which the extraction line is supported. This refers in particular to regions of the tank bottom and/or of the tank roof. 
         [0021]    In one refinement, it is also proposed that a resilient element be provided in the region of the first receptacle or in the region of the second receptacle. The resilient element may for example be metallic. The resilient element is preferably a metallic plate spring. The resilient element is arranged such that it braces the extraction pipe between the spaced-apart regions of the vessel wall. The tank is thus also braced, and relative movements between the spaced-apart regions of the vessel wall are reduced. The plate spring may preferably be of disc-shaped form and arranged around the extraction pipe. The resilient element may also be jointly integrated into the vessel wall. It is particularly advantageous for the extraction pipe to be pressed with a defined force against the tank bottom. The force may be dimensioned such that the extraction pipe does not detach from the tank bottom under the action of accelerations and forces arising during operation of a motor vehicle. This is advantageous because the fill level measurement and the extraction are carried out in each case in relation to the tank bottom. 
         [0022]    Furthermore, it is also proposed that at least one translucent portion be provided in the vessel wall. Through the translucent portion in the vessel wall it is possible to look into the interior space of the vessel from the outside. This is advantageous in particular if the at least one extraction line must be fixed in an internal receptacle during assembly. It can thus be realized firstly that a flat tank bottom is provided but also at the same time that assembly in the interior space of the vessel can be carried out in a simple manner via a single opening. Here, the translucent portion may be provided with a different material, wherein plastic is preferable, though if necessary it is also possible for the translucent portion to be realized by virtue of the rest of the vessel wall being covered or painted. In general, the provision of a single translucent portion will be adequate, though this is not imperatively necessary. 
         [0023]    The invention can be used in particular in a motor vehicle having a vessel, configured according to the invention, for a liquid, wherein a dosing unit is provided for extracting the liquid via the at least one extraction line. A motor vehicle of this type is in particular one in which a reducing agent (aqueous urea solution) is supplied into the exhaust system of the motor vehicle. For this purpose, the dosing unit may be provided with corresponding controllers in order to deliver the liquid out of the vessel as required. 
         [0024]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0025]    Although the invention is illustrated and described herein as embodied in a vessel for a liquid, in particular a reducing agent, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
         [0026]    The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0027]      FIG. 1  is a diagrammatic, sectional view of a first embodiment of a vessel according to the invention; 
           [0028]      FIG. 2  is a diagrammatic, sectional view of a second embodiment of the vessel; 
           [0029]      FIG. 3  is an illustration showing a third embodiment of the vessel; 
           [0030]      FIG. 4  is an illustration showing a motor vehicle having a vessel and a dosing unit; 
           [0031]      FIG. 5  is an illustration showing a fourth embodiment of the vessel; 
           [0032]      FIG. 6  is an illustration showing a fifth embodiment of the vessel; and 
           [0033]      FIG. 7  is an illustration showing a sixth embodiment of the vessel. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    Referring now to the figures of the drawing in detail and first, particularly, to  FIG. 1  thereof, there is shown a vessel  1  which forms a single interior space  4  in which liquid  2  is stored. The vessel  1  is in particular a tank for aqueous urea solution. The interior space  4  is formed by a closed vessel wall  3 . It is clear that the shape of the vessel wall  3  is in this case shown highly schematically, and possibly has a shape with numerous inward and outward protuberances. Here, the vessel wall  3  is for example formed with plastic, wherein in the lower left region there is provided a translucent portion  14  through which a fitter can see into the interior space  4 . The vessel wall forms in particular an upper tank roof, a lower tank bottom and interposed tank side walls. 
         [0035]    Here, a single extraction line  5  extends through the interior space  4 , the extraction line  5  being in the form of a tube and forming a direction of extent  6 . Here, the liquid  2  situated in the vessel  1  is conveyed via openings  15  in the extraction line  5  to the dosing unit  13 , which in this case is arranged on the top of the vessel  1  (vessel roof). The extraction line  5  is arranged or positioned on the vessel wall  3  so as to impart a stiffening action. For this purpose, the extraction line  5  extends between a first region and a second region  8  of the vessel wall, the regions being formed spaced apart, that is to say opposite one another. Here, the first region  7  is provided with a first receptacle  9  and the second region  8  is provided with a second receptacle  10 . Here, both receptacles are integrated into the vessel wall  3 , for example in the form of a cast-in bayonet closure. The second receptacle  10  is preferably a cast-in bayonet closure of the type. The first receptacle  9  may for example be realized as a cutout into which the dosing unit  13  with the extraction line  5  can be inserted. The dosing unit  13  is preferably formed with a circular (metallic) housing. The extraction line  5  may then be arranged eccentrically on the dosing unit  13 . This permits a suitable embodiment of the second receptacle  10  in which the extraction line  5  can be locked to the second receptacle  10  by a rotational movement of the dosing unit  13 , and can be unlocked by a further or opposite rotational movement. 
         [0036]    There has hitherto been the risk of the vessel  1  deforming, in particular bulging, in particular in the region of the bottom illustrated at the bottom, under the weight of the liquid  2 . This would cause the openings  15  of the extraction line  5  to move away from the bottom, and delivery of liquid would be a problem in the near-empty state. This is prevented here in that the extraction line  5  reduces or prevents relative movements of the first region  7  with respect to the second region  8 . For this purpose, the extraction line is fixedly connected to the first region  7  and to the second region  8 . 
         [0037]      FIG. 2  shows basically the same configuration of the vessel  1 , such that here, identical parts are provided with the same reference numerals. In contrast to  FIG. 1 , it is the case here that the dosing unit  13  is integrated into the interior space  4  of the vessel  1 . In this case, the extraction line  5  is fixed via the dosing unit  13  to the first region  7  of the vessel wall  3 . Spaced apart therefrom there is provided, as a second region  8 , a separately formed reservoir  17  from which the liquid  2  is extracted. Here, too, stiffening of the vessel structure is realized by corresponding fixing of the extraction line  5  to the reservoir  17 . In this case, the extraction line is arranged obliquely in the interior space  4  of the vessel  1 . 
         [0038]      FIG. 3  shows the provision of a flexible zone  11  which is formed circularly around the second region  8  with the second receptacle  10  of the vessel wall  3 . Here, the flexible zone  11  is in the form of a corrugation (if appropriate with a smaller wall thickness) in the vessel wall  3 . It is alternatively or additionally also possible for a flexible zone  11  to be formed around the first region  7  with the first receptacle  9  of the vessel wall  3 . By the flexible zone  11 , the volume of the interior space  4  of the vessel  1  is fixed, such that the volume varies to a lesser extent owing to thermal expansions and owing to ageing. 
         [0039]      FIG. 4  finally shows a motor vehicle  12  equipped with the corresponding vessel  1 . It can be seen in the vessel  1  that the vessel wall  3  forms an interior space  4  in which liquid  2  is stored. In the situation illustrated here, the vessel  1  has a heater  19  by which the vessel wall  3  and/or the liquid  2  in the vessel  1  can be heated as required. Again, the vessel bottom is braced with respect to the vessel roof by the extraction line  5 , such that the first region  7  is supported with respect to the second region  8 . Corresponding first receptacles  9  and second receptacles  10  are provided for this purpose. In the design variant of the extraction line  5  (composed of metal), an additional fill level sensor  18  and an integrated extraction pipe heater  26  are provided. The dosing unit  13 , which may be positioned in the interior space  4  of the vessel  1 , contains, in a separate housing, a pump  23 , a filter  24  and a valve  25 , which the liquid flows through in this sequence when it is being delivered. By use of the valve  25 , it is possible to regulate whether liquid  2  is conducted back into the interior space  4  via the return line  20  or supplied to an injector  21  via a feed line  22 . In this way, it is possible for the liquid  2 , in particular aqueous urea solution, to be supplied as required to an exhaust line  27  via the injector  21 . The liquid which is metered into the exhaust line  27  is entrained by the exhaust gas in the exhaust-gas flow direction  29 , wherein an evaporation and/or conversion of the liquid may take place. The mixture of exhaust gas and liquid may then be supplied to an exhaust-gas treatment unit  28 , for example a hydrolysis catalytic converter or a so-called SCR catalytic converter. 
         [0040]      FIG. 5  shows the provision of a plate spring  30  which presses the extraction pipe  5  in the vessel  1  against a second region  8  of the vessel wall  3 , and thereby braces a first region  7  of the vessel wall  3  and the second region  8  against one another. The extraction pipe  5  extends through the interior space  4  of the vessel  1 . A first receptacle  9  and a second receptacle  10  may be provided on the vessel wall  3  for the extraction pipe  5 . The plate spring  30  may be circular. Shoulders  31  may be provided which fix the plate spring  30  in its position. The shoulders  31  are in this case illustrated on the extraction pipe  5 . The shoulders may also be provided on the first receptacle  9  or on the vessel wall  3 . It is preferable for the plate spring  30  for bracing the extraction pipe  5  to be provided on the upper end of the extraction pipe  5 , because in this way, a fixed arrangement of the extraction pipe  5  with respect to the bottom of the vessel  3  is possible. It is however also possible for the plate spring  30  to be provided on the lower end of the extraction pipe  5  at the second receptacle  10 . The features explained above for the arrangement of the plate spring  30  on the top of the extraction pipe  5  can be correspondingly applied thereto. 
         [0041]      FIG. 6  shows a fifth embodiment of the vessel  1  according to the invention, the design variant having a special form of a flexible zone  11  which is formed circularly around the second region  8  with the second receptacle  10  of the vessel wall  3 . Here, the flexible zone  11  is in the form of a corrugated wall of a sump  33  arranged in a bottom  32  of the vessel  1 . The vessel wall  3  of the sump  33  may if appropriate be formed so as to have a smaller wall thickness in the region of the flexible zone  11  than in other regions. Owing to the flexible zone  11 , the bottom  32  of the vessel  1  is at least partially movable independently of the sump  33 . The sump  33  forms the second region  8  of the vessel  1  with the second receptacle  10 . The sump  33  is positioned fixedly in relation to the first region  7  of the vessel  1  with the first receptacle  9  by the extraction line  5 . 
         [0042]      FIG. 7  shows a sixth embodiment of the vessel  1  according to the invention, in which the flexible zone  11  is formed circularly around the second region  8  with the second receptacle  10  of the vessel wall  3 . Here, the flexible zone  11  is in the form of an encircling indentation  35  which rises proceeding from the bottom  32  of the vessel  1  and falls into the sump  33 . The vessel wall  3  may if appropriate be formed with a relatively small wall thickness in the region of the indentation  35 . Increased flexibility of the indentation  35  is attained in this way. Owing to the indentation  35 , the bottom  32  of the vessel  1  is at least partially movable independently of the sump  33 . The sump  33  forms the second region  8  of the vessel  1  with the second receptacle  10 . The sump  33  is positioned fixedly in relation to the first region  7  of the vessel with the first receptacle  9  by the extraction line  5 . The indentation  35  constitutes a flow resistance between the rest of the bottom  32  and the sump  33 . The indentation  35  may be shaped such that, in the case of particularly low fill levels in the vessel  1 , liquid  2  passes from the bottom  32  into the sump  33  as a result of sloshing movements, but a return flow of liquid from the sump  33  to the rest of the bottom  32  of the vessel  1  is hindered.  FIG. 7  shows such a design of the indentation  35 . In the direction of the sump  33 , the indentation  35  is formed with a steeply rising flank, whereas the indentation  35  slopes down at a shallow angle to the rest of the bottom  32  of the vessel  1 .  FIG. 7  shows an elevated fill level of liquid  2  within the sump  33  as a result of sloshing movements. 
         [0043]    Furthermore,  FIG. 7  illustrates a special variant of the second receptacle  10  for fastening the extraction line  5  to the vessel wall  3 . Fastened to the extraction line  5  is an anchor  34  which engages into a corresponding cutout  36  of the vessel wall  3 . By a second receptacle  10  of the type, it is possible to attain secure fixing of the extraction line  5  to the vessel wall  3 , via which fixing both axial forces (in the direction of the extraction line  5 ) and also transverse forces (perpendicular to the extraction line  5 ) can be transmitted.