Abstract:
A fuel tank has a cavity ( 2 ) with a reinforcement device ( 5; 45 ) to provide support. The reinforcement device ( 5 ) is configured to absorb both compressive forces and tensile forces.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority under 35 USC 119 to German Patent Application No. 10 2010 036 683.8 filed on Jul. 28, 2010, the entire disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a fuel tank having a cavity with a reinforcement device to provide support. 
         [0004]    2. Description of the Related Art 
         [0005]    Generic fuel tanks are shown in U.S. Pat. No. 7,455,190, U.S. Pat. No. 6,338,420, U.S. Pat. No. 6,135,306, German laid-open patent application DE 10 2008 009 829 A1 and published British patent application GB 2 236 288 A. 
         [0006]    The object of the invention is to provide a fuel tank with a reinforcement device that has a high degree of stability and can be manufactured cost-effectively. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention relates to a fuel tank with a cavity and a reinforcement device arranged in the cavity to provide support. The reinforcement device is configured to absorb both compressive forces and tensile forces. The cavity in the fuel tank functions to hold fuel. For operationally conditioned reasons and owing to ambient influences, the pressure in the cavity can change to a greater or lesser extent due to temperature fluctuations. The fuel tank preferably is a pressurized tank made of plastic and is arranged, for example, in a pressurized tank system of a hybrid vehicle. The reinforcement device can significantly improve the stability of the fuel tank both in the case of underpressure and in the case of overpressure in the cavity. 
         [0008]    The reinforcement device preferably comprises at least one tension/compression strut arranged between two opposite wall regions of the fuel tank. The tension/compression strut may extend through the two opposite wall regions of the fuel tank. 
         [0009]    The tension/compression strut may be clamped in between the two opposite wall regions of the fuel tank with the aid of a spring device. The spring device prestresses the two opposite wall regions away from one another. Thus, a predefined distance between the two wall regions of the fuel tank remains unchanged even in the case of an underpressure in the cavity. 
         [0010]    The spring device may comprise at least one compression spring, for example, a helical compression spring. A plurality of compression springs can also be connected in parallel and/or in series. 
         [0011]    The spring device may be clamped between two inner plates. The inner plates function to support the spring device and to apply the spring force to the fuel tank over a surface. The inner plates can be formed from the same plastic material as the fuel tank. 
         [0012]    The two opposite wall regions of the fuel tank each may be arranged between an inner plate and an outer plate. The inner and outer plates function, inter alia, to protect the fuel tank and can be formed from the same material as the fuel tank or from different materials than the fuel tank. 
         [0013]    An axial securing means may be provided at each end of the tension/compression strut. The axial securing means prevents the two opposite wall regions from moving away from one another if an overpressure occurs in the cavity. Tensile forces are applied to the tension/compression strut via the axial securing means. 
         [0014]    The two opposite wall regions of the fuel tank may be sealed off on the outside by a lid in a region where the tension/compression strut passes through. The lid preferably is formed from plastic and preferably is connected in a materially joined fashion to the wall regions of the fuel tank. 
         [0015]    The tension/compression strut preferably is formed from metal. As a result, a high degree of stability of the fuel tank can be achieved easily. 
         [0016]    The fuel tank preferably is a plastic pressurized tank. The plastic pressurized tank may be blow molded. 
         [0017]    Further advantages and details of the invention emerge from the following description of an exemplary embodiments are described with respect to the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a highly simplified illustration of a fuel tank of the invention in section. 
           [0019]      FIG. 2  is a detailed illustration of a detail from  FIG. 1  in section. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]      FIG. 1  is a highly simplified cross-sectional view of a fuel tank  1  with a cavity  2  for holding fuel. The fuel tank  1  comprises a plastic container  4  with a reinforcement device  5  in the cavity  2 . The plastic container  4  preferably is manufactured by blow molding. 
         [0021]    The reinforcement device  5  is arranged between two opposite wall regions  8 ,  9 , of the plastic container  4  or fuel tank  1 , and comprises a tension/compression strut  10 . The tension/compression strut  10  extends through the two wall regions  8 ,  9  so that the free ends of the tension/compression strut  10  are arranged outside the plastic container  4 . 
         [0022]    The free ends of the tension/compression strut  10  preferably are arranged in trough-like depressions formed in the wall regions  8 ,  9  of the fuel tank  1 . The wall regions  8 ,  9  are curved convexly inward to form the depressions. 
         [0023]    The reinforcement device  5  also comprises a spring device  14  that is clamped between two inner plates  18 ,  19  that define spring plates. The inner plate  18  and  19  bear respectively on the insides of the wall regions  8  and  9 . 
         [0024]    The wall regions  8 ,  9  each are arranged between the assigned inner plate  18 ,  19  and a corresponding outer plate  21 ,  22 . The outer plates  21 ,  22  have essentially the same form as the inner plates  18 ,  19 . The tension/compression strut  10  extends through the inner plates  18 ,  19 , the wall regions  8 ,  9  and the outer plates  21 ,  22 . 
         [0025]    An axial securing means  23 ,  24 , such as a cotter pin, is provided on each of the free ends of the tension/compression strut  10  projecting out of the cavity  2 . The axial securing means  23 ,  24  prevents the wall regions  8 ,  9  from moving away from one another if an overpressure occurs in the cavity  2  of the fuel tank  1 . 
         [0026]    The spring device  14 , which may be a helical compression spring, is clamped between the two wall regions  8 ,  9  in such a way that the two wall regions  8 ,  9  do not move toward one another if an underpressure occurs in the cavity  2  of the fuel tank  1 . 
         [0027]    The reinforcement device  5  holds the wall regions  8 ,  9  at a constant distance both in the case of an underpressure and an overpressure in the cavity  2  of the fuel tank  1 . 
         [0028]    Lids  31 ,  32  are welded onto the outside of the wall regions  8 ,  9  to seal off the fuel tank  1 . The lids  31 ,  32  surround the free ends of the tension/compression strut  10  and the regions thereof that pass through the plastic container  4  and the outer plates  21 ,  22 . 
         [0029]      FIG. 2  illustrates a detail of a fuel tank  41  in section. The fuel tank  41  is embodied, similar to the fuel tank  1  in  FIG. 1 , as a plastic pressurized tank with a plastic pressurized tank container  44 . A reinforcement device  45  is arranged in the fuel tank  41 . 
         [0030]    One end of the reinforcement device  45  is illustrated in  FIG. 2  at a wall region  48  of the plastic pressurized tank container  44 . The reinforcement device  45  comprises a tension/compression strut  50  and a spring device  54 . The spring device  54  comprises a helical compression spring  55  that is supported on an inner plate  58 . 
         [0031]    The spring device  54  alternatively or additionally may comprises a second helical compression spring  56  that is prestressed against the inner plate  58 . The helical compression spring  55  is arranged inside the helical compression spring  56  and the two helical compression springs  55  and  56  extend around the tension/compression strut  50 . 
         [0032]    The inner plate  58  defines a spring plate for the spring device  54 . The wall region  48  is arranged between the inner plate  58  and an outer plate  61 . The end of the tension/compression strut  50  illustrated in  FIG. 2  extends out through the inner plate  58 , the wall region  48  and the outer plate  61 . 
         [0033]    An axial securing means  63  is provided at the free end of the tension/compression strut  50 . The wall region  48  is clamped, together with the inner and outer plates  58  and  61 , between the axial securing means  63  and the spring device  54 . 
         [0034]    The outwardly projecting free end of the tension/compression strut  50  is arranged, together with the outer plate  61  and the axial securing means  63 , in a depression in the plastic container  44 . The depression is covered by a lid  71  with a seal-forming effect. The lid  71  preferably is connected in a materially joined fashion, in particular welded, to the plastic container  44 . 
         [0035]    The plastic container  44 , the inner plate  58 , the outer plate  61  and/or the lid  71  may be manufactured, for example, from a high density polyethylene. The plastic container  44  preferably is a multiple layer structure. The outer plate  61  advantageously can be prepressed to avoid undesired noises or undesired wear. 
         [0036]    The spring device  54  presses the inner plates  18 ,  19 ;  58  against the wall regions  8 ,  9 ;  48  in the event of an underpressure. As a result, undesired clattering noises are prevented. Maintaining the defined distance between the wall regions  8 ,  9 ;  48  prevents undesired wear of the plastic container  4 ;  44  that otherwise could be caused by a relative movement of the wall regions  8 ,  9 ;  48 . The lids  31 ,  32 ;  71  prevent undesired leakage. 
         [0037]    The reinforcement device  5 ,  45  does not significantly or adversely affect the ability of the plastic container  4 ;  44  to deform in the case of an accident.