Abstract:
In a fuel tank of plastic material with functional components contained therein for implementing functions such as operational venting, refuelling, refuelling venting and drawing off fuel, the functional components are pre-mounted on a carrier which equipped therewith was fitted into the tank or which was already integrated into the tank upon shaping thereof. The carrier is in the form of a hollow body through which fuel can circulate within the tank.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
         [0001]    This application claims the priority of German patent application Serial No 102 60 953.5 filed Dec. 20th 2002, the subject matter of which is incorporated herein by reference.  
         FIELD OF THE INVENTION  
         [0002]    The invention concerns a fuel tank, for example for a motor vehicle, comprising various functional components contained therein for implementing operational functions of the tank.  
           [0003]    The invention further concerns a carrier for functional components of a motor vehicle fuel tank.  
           [0004]    In this specification the term functional component is used to denote any component which is involved in operation of the tank in its various aspects, such components including for example devices for operational venting of the tank for venting it during operation of a motor vehicle in which the tank is disposed, refuelling, refuelling venting for venting the tank during a refuelling procedure, and drawing off fuel from the tank, valves, pumps, senders and conduits.  
         BACKGROUND OF THE INVENTION  
         [0005]    Particularly in the case of fuel tanks for motor vehicles, which are produced in one piece from plastic material for example by an extrusion blow molding procedure, many functional components such as for example pumps, senders, operational and refuelling venting valves, conduits and the like, are introduced into the tank after the tank has been finally manufactured. One reason for this is that many components have to assume a given position or arrangement within the tank and accordingly have to be fixed in that position. Such functional components are therefore frequently only disposed in the tank after it has been finished. To do that however it is often necessary for comparatively large openings to be provided in the fuel tank. In the case of complicated tank geometries, for example when dealing with saddle tanks which are comparatively frequently encountered in rear wheel-drive motor vehicles, it is frequently necessary for mounting or final adjustment and inspection openings to be provided in each of the two halves of the saddle tank, to ensure that the functional components are properly disposed therein. Finally, in most cases it is necessary to provide openings for operational and refuelling venting valves and optionally for a roll-over valve and venting conduits. The venting conduits are then usually routed or fixed at the outside of the tank.  
           [0006]    It will be appreciated that openings in the wall of the fuel tank represent potential emission sources for hydrocarbons. The wall of the tank is usually in the form of a multi-layer co-extrudate which includes hydrocarbon barrier layers so that the outer skin of the fuel tank is very substantially impermeable in relation to hydrocarbons. However, in the region of passages and openings through the wall of the tank, which are welded closed by means of cover caps, it is not always possible to guarantee that a completely gas-impermeable sealing integrity is achieved. It will be appreciated that connection nipples and hoses on the tank are also potential emission sources.  
           [0007]    The endeavour therefore is for the wall of the fuel tank to have as few openings as possible and for as many functional components as possible to be disposed in the interior of the tank.  
           [0008]    In terms of hydrocarbon permeation, a complex tank geometry such as a saddle tank with only one single opening, apart that is from the filler pipe, is viewed as being the ideal.  
           [0009]    A fuel tank of plastic material comprising various functional components, which is optimised in regard to the above-indicated problems, is described for example in DE 101 07 075 A1. That disclosure constitutes a fuel tank with functional components which are disposed in the interior of the tank and which are integrated into the tank when the tank is produced as by a molding process. The functional components are disposed on a carrier element and are introduced together with the carrier element into a preform which subsequently, to form the fuel tank, is shaped around the carrier element and the functional components disposed thereon. That fuel tank structure provides that all connecting lines and conduits which extend out of the tank are passed through a single opening in the wall of the tank in order thereby to minimise the number of openings in the body of the tank.  
           [0010]    The carrier element in that arrangement is in the form of a flat element extending substantially transversely with respect to the longitudinal extent of the tank, with the functional components being fixed thereto displaceably in a dovetail-shaped guide arrangement. The carrier element is welded to the inside surface of the wall of the fuel tank and serves at the same time as an element for breaking up the surge movements of fuel within the tank. For that reason it is preferable for the carrier element also to be arranged transversely with respect to the longitudinal extent of the tank.  
           [0011]    It will be noted here however that the structure described in DE 101 07 075 A1 is disadvantageous in regard to the stiffness of the tank. More specifically the carrier structure introduced into the fuel tank may under some circumstances stiffen the fuel tank to such a degree that the resistance thereof to impact-induced shocks thereon is adversely affected. On the other hand, it is desirable for the carrier element to be in a fixed position within the fuel tank in order to be able to guarantee suitable positional accuracy in terms of mounting of the functional components within the tank.  
           [0012]    Depending on the material of which the carrier element consists, generally involving an injection molding, the operation of fitting it during the procedure for shaping the tank may also give rise to problems due to shrinkage stresses which may occur upon cooling of the fuel tank in the mold. In general the material of the carrier, due to the method of manufacture thereof, for example by injection molding, will differ in respect of its properties from that of the fuel tank.  
         SUMMARY OF THE INVENTION  
         [0013]    An object of the present invention is to provide a fuel tank of plastic material and including various functional components, which affords improved load-carrying capacity in relation to shock loadings thereon and thus in relation to impact against the tank.  
           [0014]    Yet another object of the present invention is to provide a fuel tank for example for a motor vehicle which includes a plurality of functional components, the design being such that the functional components are capable of being arranged within the tank in a flexible fashion.  
           [0015]    In accordance with the principles of the present invention the foregoing and other objects are attained by a fuel tank of plastic material comprising a plurality of functional components contained therein, for implementing operational functions of the tank. The functional components are pre-mounted on a carrier which, equipped therewith, was introduced into the tank or was already integrated into the tank upon shaping thereof, for example by molding. The functional component carrier is in the form of a hollow body through which fuel can flow within the tank.  
           [0016]    As will be apparent from the description hereinafter of preferred embodiments of a fuel tank and a carrier according to the invention, the hollow body constituting the functional component carrier can be of a comparatively thin-walled structure and can be easily produced in a spatially complex contour so that the tank enjoys a high degree of flexibility in terms of the arrangement of the functional components in the tank and the fixing of the carrier within the tank.  
           [0017]    In accordance with a preferred feature of the invention the functional component carrier is supported yieldingly in relation to the inside wall surface of the tank body, thus affording a comparatively high load-carrying capacity for the tank in relation to impact-induced shock loadings. This already arises out of the fact that the carrier itself is in the form of a hollow body, thus giving a certain degree of flexibility and yielding resilience due to the nature and structure of the carrier. It is particularly advantageous in this respect however if the component has resiliently yielding support feet or legs which are formed integrally in the wall of the carrier.  
           [0018]    In a preferred feature of the invention the support legs can be for example in the form of bellows-shaped outwardly formed portions of the carrier.  
           [0019]    By virtue of the fact that the carrier extends in the form of a hollow body within the tank, it is possible for those outwardly formed portions of the carrier to be provided at any appropriate location at the periphery of the carrier, thus making it possible to particularly advantageously adapt the position of the carrier fixing points to the geometry of the tank.  
           [0020]    It will be appreciated that the carrier will comprise a material which is compatible in terms of weldability with the inside wall surface of the tank and that, in the region of the support feet, a weld can be produced between the carrier and the inside wall surface of the tank in the operation of shaping the tank.  
           [0021]    In a preferred feature of the invention, the wall of the functional component carrier is provided with openings for receiving the functional components.  
           [0022]    Preferably, the openings are at least partially turned out in a collar-like shape or they are provided with fixing collars which are formed integrally thereon. That makes it easily possible for valve housings or other functional devices to be inserted into and welded in such openings. The openings can be provided for example in manufacture of the carrier in the form of generally dome-shaped outwardly pressed portions or raised portions in the external contour of the carrier. Cutting open the ‘bumps’ produced by the outwardly pressed or raised portions on the carrier makes it easily possible to provide fixing and mounting seats for valves or other devices.  
           [0023]    In addition, in a preferred feature of the invention, the wall of the carrier can be provided with one or more orifices operable to reduce the stiffness thereof.  
           [0024]    Another preferred feature of the invention provides that the carrier advantageously forms a means for dividing the free volume of the interior of the tank into a plurality of intercommunicating sub-volumes. That provides that fuel surge movements produced in the tank as a consequence of a motor vehicle in which the tank is fitted assuming different positions or operating conditions are suitably damped and restrained within the tank.  
           [0025]    In accordance with another preferred feature of the invention the carrier is produced from recycled material from the production of the fuel tank, such material usually being referred to as re-grind. That automatically guarantees that the carrier material can be welded to the wall of the tank.  
           [0026]    The carrier can be produced for example by a deep drawing process, but it is particularly preferable for it to be in the form of a hollow body produced by an extrusion blow molding procedure, with the above-mentioned openings and/or orifices thereof being produced after it has been shaped.  
           [0027]    Further objects, features and advantages of the invention will be apparent from the description hereinafter of preferred embodiments. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]    [0028]FIG. 1 is a diagrammatic view showing the manufacture of a functional component carrier in accordance with the invention by extrusion blow molding,  
         [0029]    [0029]FIG. 2 shows a view of the functional component carrier in FIG. 1, in which the wall of the hollow body forming the carrier has been partially opened to accommodate functional components,  
         [0030]    [0030]FIG. 3 shows the carrier equipped with functional components,  
         [0031]    [0031]FIG. 4 shows a diagrammatic view illustrating the introduction of the functional component carrier into a preform for a fuel tank to be produced by extrusion blow molding,  
         [0032]    [0032]FIG. 5 shows the finally shaped fuel tank according to the invention,  
         [0033]    [0033]FIG. 6 shows a further view of the finished fuel tank according to the invention,  
         [0034]    [0034]FIG. 7 is a perspective view of an alternative form of the functional component carrier before being equipped with functional components, and  
         [0035]    [0035]FIG. 8 shows an alternative form of the fuel tank according to the invention with the functional component carrier shown in FIG. 6, accommodated within the tank. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0036]    Reference will firstly be made to FIGS. 1 and 2 to illustrate the manner of manufacture of the functional component carrier  1  according to the invention. This involves a member which, as described above, is designed to receive and exactly position various functional components of a fuel tank as generally indicated at  2  for example in FIG. 5. Reference will be made thereto in greater detail hereinafter.  
         [0037]    The functional component carrier  1  illustrated herein is in the form of a hollow plastic body produced by extrusion blow molding. As is diagrammatically shown in FIG. 1 which illustrates the procedure involved in shaping the hollow body from a suitable preform, the procedure firstly involves extruding a tubular preform of plasticised material between two halves  3   a,    3   b  of a blow molding mold  3 , the mold thus being in the opened condition as shown. The preform is then expanded in the mold  3  by means of a blowing pipe  4  inserted therein, to constitute the finished component. It will be appreciated that the carrier  1  can also be produced by a deep drawing process but the extrusion blow molding procedure is preferred here for various reasons. That manner of manufacture has proven to be particularly advantageous from the cost point of view, especially as the fuel tank  2  which is to be described hereinafter is generally also produced by extrusion blow molding. In this case the carrier  1  can be produced from the recycled material or re-grind which is produced in manufacture of the fuel tank  2 . In that case, this ensures at the same time that the plastic material of the carrier  1  is compatible in terms of weldability with the plastic material of the fuel tank  2 .  
         [0038]    As is readily apparent from FIGS. 1 and 2, the blank for producing the functional component carrier  1  is produced with hump-shaped or domed raised portions indicated for example at  5  in FIG. 7 and recessed portions  6  in the form of circular rings.  
         [0039]    In a further working operation which is indicated in FIG. 2, the functional component carrier  1  is then provided with mounting openings  7  and apertures  7   a  for example for receiving functional components to be mounted thereto.  
         [0040]    Cutting off the top of the domed raised portions  5  affords for example outwardly shaped portions  8  in the form of collars which can serve as fixing seats for receiving for example valve housings. It is possible for example for the valve housings to be welded in position against the end face of each respective portion  8 . The portions  8  are particularly suitable for carrying the contact pressure forces required for welding the valve seats in position thereon, without experiencing serious deformation.  
         [0041]    In a further working operation the carrier  1  is equipped with the appropriate functional components. Looking at FIG. 3, provided here as the functional components in this arrangement are a fuel delivery unit  9  consisting of a surge or swirl pot and a fuel pump, a filling level sender  10 , an operational venting valve  11  for venting of the tank during ordinary operation thereof, a refuelling venting valve  12  for venting of the tank during a refuelling operation, and lines  13  connecting same. The term line  13  in accordance with the invention is used herein to denote both electrical lines, fuel-carrying lines and also air-infeed and venting lines. Further functional components such as for example suction jet pumps, roll-over valves and bead removal containers can also be mounted on the carrier  1 . Reference  14  in FIG. 3 denotes partitioning wall elements which are fitted into the carrier  1  as surge-prevention components. They extend substantially transversely with respect to the longitudinal extent of the carrier  1  and in the position of installation within the fuel tank  2  also substantially transversely with respect to the longitudinal extent thereof, as will be described in greater detail hereinafter.  
         [0042]    Reference will now be made to FIG. 4 showing production of the fuel tank  2  according to the invention. FIG. 4 shows the production procedure in the phase in which a preform  16  which has been expelled from an extrusion head diagrammatically indicated at  15  has been extruded to its full length which approximately corresponds to the length of the desired finished fuel tank  2 . In that phase the preform  16  which subsequently forms the external contour of the finished fuel tank  2  is possibly stabilised from below by the use of supporting air. The functional component carrier  1  equipped with the functional components mounted thereto is now introduced from below into the opened preform  16  which is extruded between the open mold halves, by way of a holding bar  17 . The mold halves of the mold  3  then close around the entire arrangement consisting of the fuel tank  2  and the carrier  1  with its functional components thereon. The preform  16  is expanded by means of blowing air in the mold  3  to its definitive contour which is predetermined by the mold cavity defined by the mold  3 . In that procedure the material of the carrier  1  is welded in the region of pad-shaped support feet  18  to the inside wall surface  19  of the fuel tank  2 . The support feet  18  have a certain degree of elasticity, as will be described in greater detail hereinafter. In addition, by virtue of the fact that the carrier  1  is in the form of a thin-walled hollow plastic body, the carrier  1  is elastic in itself, thereby overall providing a comparatively yielding arrangement for the carrier  1  in the fuel tank  2 . The carrier is thus supported yieldingly against the inside wall surface of the tank body by virtue of the resiliently yielding support feet  18  formed integrally in the wall thereof.  
         [0043]    It should be emphasised once again at this juncture that the carrier  1  does not involve a completely closed external contour so that, in the position of installation thereof in the fuel tank  2 , fuel essentially flows or can flow through the hollow body constituting the carrier  1 . By means of the generally bellows-shaped outwardly formed portions on the carrier, which constitute the support feet  18 , the carrier  1  can be positioned in a non-rotatably, slip-free and non-tilting condition in the fuel tank  2 , such as to ensure exact positioning of the functional components in their definitive position of installation within the tank, this being something which is generally important in terms of operational reliability of the fuel tank  2 , more specifically in extreme travel situations of a motor vehicle in which the fuel tank  2  is fitted such as the position adopted by the vehicle when negotiating an extreme bend, or under extreme acceleration or extreme deceleration.  
         [0044]    Reference will now be made to FIG. 6 showing the carrier  1  in its installation position in a fuel tank  2 , wherein reference  20  denotes the filler pipe which opens at its end within the tank  2  immediately in the interior of the carrier  1 .  
         [0045]    It will be appreciated that, in the embodiment illustrated in FIGS. 1 through 6, the geometry of the fuel tank  2  and also that of the carrier  1  are comparatively simple. In addition it is assumed that the functional component carrier  1  fills approximately the entire internal volume of the fuel tank  2  so that the fuel tank  2  ultimately only forms a peripheral surface or outer casing which embraces the carrier  1 .  
         [0046]    The invention however is to be interpreted in such a way that both the fuel tank  2  and also the carrier  1  can involve a comparatively complex contour, which is quite frequently the case in a practical context. It is precisely then that it is particularly important that the carrier  1  is adapted yieldingly within certain limits precisely to the internal contour of the fuel tank  2  and is exactly and reliably placed within the tank  2 , in the sense of affording the above-described operational reliability under extreme travel conditions.  
         [0047]    Attention will now be directed to FIGS. 7 and 8 to describe a further embodiment of the fuel tank according to the invention, which is in the form of a saddle tank. This alternative form of the fuel tank  2  is encountered comparatively frequently in motor vehicles which have rear wheel drive. The relatively complicated contour of the saddle tank takes account of the positioning of the rear drive shaft of the motor vehicle in the region of the position of installation of the tank.  
         [0048]    The fuel tank which is shown generally in FIG. 8, like moreover also the fuel tank  2  illustrated in the other Figures, has only one adjustment and inspection opening  21 , referred to as a service flange opening, more specifically by virtue of the configuration and arrangement of the carrier  1 , in accordance with the invention. The carrier  1  is shown in FIG. 7.  
         [0049]    In particular the benefit of the carrier  1  according to the invention will be clearly apparent by reference to the example of the saddle tank. It can easily be envisaged that functional components must be provided in the two intercommunicating chambers indicated at  22  in FIG. 8 of the fuel tank  2 . For example, the chambers  22  must communicate with each other by way of at least one communicating duct or conduit. Usually, a suction jet pump will be arranged in that chamber  22  in which the fuel delivery unit  9  with fuel pump is not disposed. In addition, the two chambers  22  will usually communicate with each other by way of a kind of balancing line or conduit, so as to ensure equalisation of the filling levels in the two chambers  22 . The relatively severely curved spatial arrangement and the greatly increased height of the saddle portion  23  of the fuel tank  2  means that it is not possible for all functional components to be fitted into the fuel tank  2  by way of an opening as indicated at  21 . For that reason, openings  21  are provided in each of the communicating chambers  22  in conventional fuel tanks  2  of this kind.  
         [0050]    Now, by virtue of the configuration and fitment of the carrier  1  according to the invention within the fuel tank  2 , the fuel tank  2  as shown in FIG. 8 has only one opening  21  and the two chambers  22  communicate with each other substantially by way of the carrier  1  which is thus in the form of a hollow body. By virtue of the fact that the carrier  1  is desirably in the form of an extrusion blow-molded member, tubes and chambers of the carrier  1  can be in the form of an integral constituent part thereof. The carrier  1  was fitted into the fuel tank  2  in the operation of shaping same, in the manner described hereinbefore. By way of a total of five pad-shaped support feet  18 , of which only three are visible in FIG. 8, the functional component carrier  1  is supported yieldingly in relation to the inside wall surface  19  of the fuel tank  2 , in the chamber  22  which is at the left in FIG. 8 and in the region of the saddle portion  23  of the fuel tank  2 , with the support feet  18  being welded to the inside wall surface  19  of the fuel tank body in that region. In that region in which it is of a comparatively large volume, the carrier  1  is additionally provided with a fitment or mounting opening  24  through which for example a filling level sender indicated at  25  in FIG. 8 was fitted into the carrier  1 . The domed raised portions  5  of the carrier  1 , which are shown in FIG. 7, have been cut open by trimming off the top thereof, and fitted with the valves indicated at  26   a,    26   b  and  26   c  in FIG. 8. Reference numeral  27  in FIG. 8 denotes a suction jet pump which is arranged in the left-hand chamber  22  in FIG. 8 within the carrier  1  and which is connected to the fuel delivery unit  9  by way of a connecting conduit or line  28 . In this embodiment the carrier  1  in part performs the function of the balancing duct which is otherwise required, by way of the end thereof which is open and curved in a tubular configuration and which communicates with the right-hand chamber  22  of the fuel tank  2  in FIG. 8.  
         [0051]    As has been noted hereinbefore the support feet  18  are outwardly extending portions of a pad-shaped or cushion-shaped configuration. The wall of the carrier  1  is of a concentrically wavy configuration at the edges around the support feet  18 , so that this configuration provides that the support feet  18  are of a resiliently yielding nature with a bellows-like capacity for resilient movement, thereby ultimately ensuring that the carrier  1  when fitted into the fuel tank  2  does not damagingly stabilise the fuel tank  2 , which would be harmful in particular in the case of impact-induced shock loadings on the fuel tank  2 .  
         [0052]    It will be appreciated that the above-described embodiments of the fuel tanks  2  and the carriers  1  in accordance with the principles of the present invention have been set forth solely by way of example and illustration thereof and that various modifications and alterations may be made therein without thereby departing from the spirit and scope of the present invention.