Abstract:
A fuel tank and a method for producing a fuel tank for a motor vehicle. The fuel tank is designed as a blow-molded hollow plastic member, into the interior of which a functional component support is introduced. The support, to which functional components, such as a fuel pump, a level indicator or valves can be secured, includes at least one supporting leg to be supported on an inner face of the hollow plastic member delimiting the interior thereof. The supporting leg of the functional component support is designed to include a connection point to which a functional component can be connected.

Description:
[0001]    This nonprovisional application is a continuation of International Application No. PCT/EP2015/071812, which was filed on Sep. 23, 2015, and which claims priority to German Patent Application No. 10 2014 222 142.0, which was filed in Germany on Oct. 30, 2014, and German Patent Application No. 10 2015 207 835.3, which was filed in Germany on Apr. 28, 2015, and which are all herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Field of the Invention 
         [0003]    The invention relates to a fuel tank for a motor vehicle and to a method for producing such a fuel tank. 
         [0004]    Description of the Background Art 
         [0005]    According to conventional practice, such fuel tanks can be produced from a thermoplastic resin, for example by extrusion blow molding or by welding injection-molded half-shells made of thermoplastic resin. In the interior of such a fuel tank, functional components of the fuel system can be accommodated, as a result of which the space requirement outside the fuel tank is reduced and, in addition, the number of required tank openings is reduced, which is advantageous with regard to emissions from the fuel tank. 
         [0006]    DE 102 60 953 A1, which corresponds to US 2004/0129708, and which discloses a generic fuel tank which is designed as a blow-molded hollow plastic member, into the interior of which a functional component support is inserted. Various functional components, such as a fuel pump, a level indicator or valves, can be attached to the functional component support. In addition, the functional component support has supporting legs, by means of which the carrier is supported on opposite sides on the inside of the fuel tank. 
         [0007]    In the production of the fuel tank, the functional component support is first fitted with the functional components by forming a pre-assembly unit, which is separate from the fuel tank. The assembled functional component support is then inserted into the interior of a tubular fuel tank preform made of thermoplastic resin. Subsequently, a blow molding process takes place, in which the preform is expanded to its final outer contour in a blow molding tool using blown air and application of heat. During the blow molding process, the functional component support is also welded or glued to the inside of the fuel tank in the region of its supporting legs. Accordingly, at least the supporting legs of the functional component support are made of a plastic material which is compatible with the plastic material of the fuel tank with regard to weldability. 
         [0008]    The precisely positioned arrangement of the functional components in the interior of the fuel tank is of great importance in order to ensure the functional reliability of the fuel tank even in extreme driving situations, such as an extreme curve position or an extreme acceleration. The functional component support must therefore be rigidly connected to the plastic container by means of the supporting legs so as to ensure a torsion-proof, tilt-proof and non-slip positioning in the fuel tank. 
         [0009]    As mentioned above, the functional component support is manufactured in common practice from a thermoplastic resin with a comparatively low material thickness. The functional component support is thus designed to be elastically compliant (i.e., with low inherent stiffness), so that overall a relatively compliant arrangement of the functional component support is achieved, which can be disadvantageous with regard to a secure positioning of the functional components. 
       SUMMARY OF THE INVENTION 
       [0010]    It is therefore an object of the invention to provide a fuel tank and a method for producing such a fuel tank, in which a secure positioning in the interior of the fuel tank is ensured in a simple manner. 
         [0011]    In an exemplary embodiment a functional component support is rigidly connected to the inner wall of the fuel tank via its supporting legs. The transition from the supporting leg of the functional component support into the fuel tank wall thus forms a node location which is dimensionally stable and through which forces are transferred. Therefore, the node location is designed with an increased component stiffness in comparison to adjacent, elastically compliant regions. By utilizing this fact, the supporting leg of the functional component support is formed according to the characterizing part of claim  1  with a connection point to which a functional component can be connected. The functional component is thus fastened directly to the supporting leg. The supporting leg of the functional component support, which defines the component-rigid node location, is thus also used in a double function for the correct positioning of the functional component. 
         [0012]    The functional component support can be, for example, a baffle wall, which reduces the fuel surge movements and which extends transversely through the interior of the fuel tank and divides the latter into compartments. The baffle wall is supported with supporting legs on opposite sides on the inside of the fuel tank so that the otherwise resiliently flexible fuel tank wall is dimensionally stabilized. 
         [0013]    The supporting leg can be a flat, plate-shaped wall section with a contact surface, which is in contact with the fuel tank interior, for example, in a welded connection. The contact surface can have a knob-shaped surface structure with which the heat capacity at the contact surface is reduced in order to improve weldability. 
         [0014]    On a side of the wall section facing away from the contact surface, the connection point of the functional component can be provided. In this way, the connection point of the functional component is positioned directly on the supporting leg, which together with the inner wall of the fuel tank defines the above-specified component-rigid node location. 
         [0015]    With a view to simple assembly, it is advantageous if the functional component is mountable at the connection point without tools. For this reason, the connection point can have at least one latching element which can be brought into latching engagement with a corresponding counter-contour on the functional component. 
         [0016]    The baffle wall acting as a functional component support can be formed from a flat material with a thin wall thickness. For further stiffening, an assembly space with a stiffening effect can be formed in the baffle wall in which the connection point is positioned. The assembly space can be covered on the upper side by the supporting leg wall section which merges into a half-shell-shaped circumferential wall angled therefrom. The circumferential wall can partly surround the connection point. At the bottom, the above-mentioned assembly space can be limited by a mounting base. In a preferred technical implementation, the above-mentioned latching element can have a latching web, which is formed on the supporting leg wall section and projects into the assembly space. At the free end of the latching web, a latching lug can be formed which engages behind the counter-contour on the functional component. 
         [0017]    The assembly space can be open to the outside via an access opening. During assembly, the functional component can be inserted into the assembly space through the access opening. The access opening may extend between the upper supporting leg wall region and the mounting base, and may be laterally bounded by the edges of the half-shell-shaped circumferential wall. 
         [0018]    In the production of the fuel tank, the functional component support is initially fitted with the at least one functional component by forming a pre-assembly unit which is separate from the fuel tank. When the functional component support is fitted, in a first assembly step, the functional component can be inserted into the assembly space in an insertion direction through the access opening, and pre-positioned therein. In a second assembly step, the pre-positioned functional component can be connected in an assembly direction to the connection point of the supporting leg. 
         [0019]    In order to simplify the assembly process, the assembly space can have an insertion section with a large access cross-section on its side that is spaced apart from the connection point. In this way, the insertion as well as the pre-positioning of the functional component in the assembly space is simplified. In addition, the insertion section of the assembly space can transition in the direction of the connection point, into a positioning section, which has a reduced cross-section as compared to the insertion section, while forming a positioning slope. In this way, in the second assembly step, the functional component, which is moved in the assembly direction, is automatically aligned with respect to the connection point in the supporting leg. 
         [0020]    The assembled functional component support is then inserted into the interior of a fuel tank preform made of plastic material. In a subsequent blow molding operation, blown air is introduced into the preform, which is arranged in a blow molding tool, and the preform is expanded to its final outer contour under internal pressure and under application of heat. During the blow molding process, the welding of the supporting legs to the inner wall of the fuel tank is simultaneously carried out. 
         [0021]    After the functional component support has been fitted with, for example, the operating ventilation and refueling valves, the blow molding process is carried out, in which the fitted functional component support is initially inserted into the interior of the tubular fuel tank preform made of a thermoplastic resin. This takes place in an insertion direction along a tube longitudinal axis of the tubular fuel tank preform. After the insertion, the fuel tank preform is expanded to its final component contour in a blow molding tool by means of blow air and under application of heat. 
         [0022]    During the insertion of the functional component support into the tubular fuel tank preform, there is a risk that the functional component support will collide with the inner wall of the tubular fuel tank preform. This can possibly lead to damage to the thermoplastic resin or it can affect the correct positioning of the operating ventilation and refueling valves in the fuel tank. 
         [0023]    The connection points formed on the functional component supports for the above-mentioned valves, as well as the supporting legs as viewed in the direction of insertion, can be arranged at a longitudinal distance from one another, and arranged one behind the other. In this way, the insertion cross-section of the functional component support can be reduced, whereby during the insertion process, disadvantageous collisions of the functional component support with the inner wall of the tubular plastic container preform can be avoided. In order to further reduce the insertion cross-section of the functional component support, the connection points and/or the supporting legs, as viewed in the insertion direction, can be arranged at least partially in alignment one behind the other. 
         [0024]    For further stiffening of the finished plastic container, the functional component support can have strut arrangements spaced apart from each other in the direction of insertion. Each of the strut arrangements is supported across the supporting legs transversely to the direction of insertion on opposite fuel tank inner surfaces to form component-rigid node locations with the aid of which the fuel tank is improved in terms of dimensional stability. 
         [0025]    The functional component support can, for example, be inserted into the fuel tank preform by means of a retaining mandrel (pin). A stable mounting of the functional component support on the retaining mandrel is of great importance with regard to process reliability. For this purpose, the functional component support can have at least one or more retaining mandrel passage openings, through which the retaining mandrel can be inserted up to a movement stop. The connection points for the operating ventilation and refueling valves can be positioned in the retaining mandrel, which is inserted in the functional component support, without or only with a small transverse offset. 
         [0026]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes, combinations and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein: 
           [0028]      FIG. 1  is a perspective view of a plastic fuel tank, in the interior of which a baffle acting as a functional component support is arranged; 
           [0029]      FIG. 2  is a perspective detailed view of an upper supporting leg of the baffle with an as yet still disassembled venting valve; 
           [0030]      FIG. 3  illustrates the supporting leg of the baffle with a venting valve mounted thereon; and 
           [0031]      FIGS. 4 to 8  are respective views, each showing the process steps for producing the fuel tank shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0032]      FIG. 1  is a perspective view of a fuel tank made from a thermoplastic resin, which is designed as a blow-molded plastic hollow member. In the interior of the fuel tank, an elongated baffle wall  1  is arranged, which divides the interior of the tank. The baffle wall  1  is also manufactured from a thermoplastic resin, for example in an injection-molding process. As can be seen from  FIG. 1 , a total of three mutually spaced vertical, columnar strut arrangements  3 , which are supported in a vertical direction between the upper and lower fuel tank inner sides, are integrated in the baffle wall  1 . For this purpose, each of the strut arrangements  3  of the baffle wall  1  has lower supporting legs  4  and upper supporting legs  5 , which are supported on the respective fuel tank interior side, under the formation of node locations K. The node locations K are designed to be rigid to provide the fuel tank and the baffle wall  1  arranged therein with sufficient dimensional stability. 
         [0033]    In  FIG. 1 , each of the upper supporting legs  5  of the strut arrangements  3  is formed with an additional connection point  7 , in which functional components, such as a fuel pump or venting valves  8 ,  9 , are connected. The venting valves  8 ,  9  are connected to a vent line  11 , which can be guided outwards via a tank connector  15 . 
         [0034]      FIGS. 2 and 3  show the construction of one of the upper supporting legs  5 . Accordingly, the supporting leg  5  has a plate-shaped wall section  17 , on the upper side of which a knob-like structured contact surface  19  is formed. In the assembly position, the supporting leg wall section  17  is welded at its contact surface  19  to the fuel tank interior. In  FIGS. 2 and 3 , the connection point  7  has latching elements, the latching webs  21  of which are formed on the underside of the supporting leg wall section  17 , facing away from the contact surface  19 . 
         [0035]    The latching webs  21  of the connection point  7  project vertically downwards into an assembly space  23 . At their free lower ends, the latching webs  21  each have a latching lug  24 , which, in the assembly position ( FIG. 3 ), engage behind a corresponding counter-contour  25  on the housing  27  of the venting valve  9 . 
         [0036]    In  FIGS. 2 and 3 , the above-mentioned assembly space  23  is covered on the upper side by the supporting leg wall section  17 , which merges into an angled, half-shell circumferential wall  29 , which is arranged vertically and surrounds the connection point  7 . 
         [0037]    At the bottom, the assembly space  23  is bounded by a mounting base  31 . Between the two vertically extending edges of the half-shell-shaped circumferential wall  29 , an access opening  33  is defined, which extends in the vertical direction from the mounting base  31  to the lower side of the supporting leg wall section  17 . 
         [0038]    In the production of the fuel tank, firstly, the baffle wall  1  acting as a functional component support is fitted with the functional components  8 ,  9 , under formation of a pre-assembly unit, which is separate from the fuel tank. The fitted baffle wall  1  is then inserted into the interior of a tubular fuel tank preform made of plastic. Subsequently, a blowing operation is carried out in which the preform is expanded into the final tank outer contour and, at the same time, the upper and lower supporting legs  4 ,  5  of the baffle wall are also welded at their contact surfaces  19  to the material of the plastic tank wall. 
         [0039]    The assembly process is illustrated in  FIGS. 2 and 3 , in which the venting valve  9  is connected to the connection point  7  of the upper supporting leg  5 . Accordingly, in a first assembly step, the venting valve  9  is inserted into the assembly space  23  through the access opening  33  in an insertion direction I ( FIG. 2 ), and is pre-positioned there on the mounting base  31 . Subsequently, in a second assembly step, the already pre-positioned venting valve  9  is displaced vertically upwards in an assembly direction II and locked with the connection point  7 , as shown in  FIG. 3 . As a result of the latching process, a clicking sound is produced which confirms, as an acoustic feedback signal, a perfect connection of the venting valve  9  to the supporting leg  5 . According to  FIG. 3 , the venting valve  9  is fastened in the locked state at a distance from the mounting base  31 , on the underside of the supporting leg wall section  17 . 
         [0040]    For ease of assembly, the assembly space  23  has, on its side facing away from the connection point  7 , an insertion section  35  with a large access cross-section, which allows for a simple pre-positioning of the venting valve  9  in the assembly space  23 . The insertion section  35  of the assembly space  23  merges into an upper positioning section  39 , in the upward direction to the connection point  7 , to form a positioning slope  31 , which has a reduced cross-section as compared to the insertion section  35 . Due to the cross-section tapering, a precisely positioned alignment is made in the second assembly step (i.e., when the venting valve  9  is displaced onto the latching elements of the connection point  7 ) in the assembly direction II upwards. 
         [0041]    The upper supporting legs  5  of the strut arrangements  3  shown in  FIG. 1  are essentially identical to the supporting leg  5  shown in detail in  FIGS. 2 and 3 , but, if appropriate, are conformed to the respective functional component to be integrated therein. 
         [0042]    Below,  FIGS. 4 to 8  describe the basic process steps for the production of the fuel tank shown in  FIG. 1 : according to  FIG. 4 , initially, a tubular fuel tank preform  41  made of a thermoplastic resin is provided, the inner wall of which defines a free cross-section q i . The preassembled functional component support  1  is inserted ( FIG. 5 ) into the interior of the tubular fuel tank preform  41  in an insertion direction E along a longitudinal axis S. In  FIG. 5 , the fuel tank preform  41  with the functional component support  1  inserted therein is located between two mold halves of a blow molding tool  43 . This is closed for carrying out a blow molding operation. Blown air is then introduced into the preform  41 , as a result of which the preform  41  is expanded under application of internal pressure and heat to its final component contour ( FIG. 6 ). 
         [0043]    As can be seen in  FIG. 4 , the operating ventilation and refueling valves  8 ,  9 ,  10  as well as the supporting legs  4 ,  5  are arranged one behind the other at longitudinal intervals a, as viewed in the direction of insertion E. In addition, the two operating ventilation valves  8 ,  9  are arranged one after the other, as viewed in the direction of insertion E, while the middle refueling valve  10  is offset only laterally outwards by a small transverse displacement. Overall, an insertion cross-section q, which is substantially smaller than the interior cross-section q i  provided by the tubular fuel tank preform  41 , is thus obtained. As a result, a process-reliable insertion movement of the functional component support  1  is achieved in a simple manner without collision with the preform inner wall. 
         [0044]    The insertion operation is performed according to  FIG. 4 or 7  by means of a retaining mandrel  45 . As can be seen in  FIG. 7 , the rod-shaped retaining mandrel  45  is inserted through passage openings  47  of the functional component support  1  up to a movement stop  49 , which is located upstream in the insertion direction E. As shown in  FIG. 8 , the operating ventilation and refueling valves  8 ,  9 ,  10  are positioned on the functional component support  1 , without or with only a small transverse offset to the retaining mandrel  45 , in order to further reduce the insertion cross-section q F . 
         [0045]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.