Abstract:
A joint part includes a connection part weldable on the tank and a tube part including an inner circumferential face. An inner tube is fitted in the inner circumferential face and in contact with the inner circumferential face. The tube and the inner tube include materials having different swelling rates against a fuel to be stored in the tank. An end of the tube and a corresponding end of the inner tube in an axial direction of the tube and the inner tube include slopes therearound in contact with each other. The slopes are inclined from the axial direction. When the tube and the inner tube swell due to wet with the fuel, the slopes have relative displacement in the axial direction and a radial direction of the tube and the inner tube with contact therebetween.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a connection tube for a fuel tank and particularly to a fuel tank mounted on a vehicle for filling fuel.  
         [0003]     2. Description of the Related Art  
         [0004]     Recently, fuel tanks which are made of plastic by blow molding become a trend as fuel tanks mounted on vehicles from a viewpoint of rust prevention and a lightweight requirement. Generally, to the fuel tank are attached various structural parts such as a vent valve for maintaining an internal pressure of the fuel tank by introducing a fuel vapor gas at a space above a liquid level to the outside of the fuel tank and a fuel service valve (backflow valve) connected to a filler tube. In a case of the plastic fuel tank, these structural parts are generally attached to the fuel tank by a heat welding method from a viewpoint of simplifying a production process.  
         [0005]     U.S. Pat. No. 6,808,209 discloses a connection tube for a plastic fuel tank as an attachment. The connection tube has an outer tube connectable to a filler tube and an inner tube, formed of an HC (hydrocarbon) barrier material which is different from a material of the outer tube, for receiving and feeding fuel to the fuel tank.  
       SUMMARY OF THE INVENTION  
       [0006]     An aspect of the present invention provides a connection tube for a fuel tank having an opening, comprising: a joint part including an weldable part weldable on the fuel tank at the opening and a connection tube part including an inner circumferential face; and an inner tube, fitted in the inner circumferential face, contacting the inner circumferential face, the connection tube part and the inner tube comprising materials having different swelling rates against a fuel to be stored in the tank, wherein one end of the connection tube part and one end of the inner tube include slopes therearound in contact with each other, respectively, the slopes being inclined from the axial direction of the connection tube part and the inner tube, wherein when the connection tube part and the inner tube swell due to wet with the fuel, the slopes have relative displacement in the axial direction and a radial direction of the connection tube part and the inner tube with contact therebetween. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The object and features of the present invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings in which:  
         [0008]      FIG. 1  is a partially cross-sectional side elevation view of a connection tube according to the present invention and a fuel tank;  
         [0009]      FIG. 2  is a cross-sectional enlarged side elevation view of the connection tube of a first embodiment according to the present invention to show a part indicated by “A” shown in  FIG. 1 ;  
         [0010]      FIG. 3  is a cross-sectional enlarged side elevation view of a part indicated by “B” shown in  FIG. 2 ; and  
         [0011]      FIG. 4  is a cross-sectional enlarged side elevation view of the connection tube of a second embodiment according to the present invention. 
     
    
       [0012]     The same or corresponding elements or parts are designated with like references throughout the drawings.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0013]     Prior to describing an embodiment of the present invention, the related art mentioned above will be further described. In U.S. Pat. No. 6,808,209, the inner tube formed of the HC (hydrocarbon) barrier material has a different swelling rate regarding fuel from the outer tube, so that deformation or a stress may occur when the connection tube is wet with the fuel because the HC barrier material has a higher selling rate than the outer tube. Further, there is no evacuation space of the inner tube made of the HC barrier material without protrusion toward a fuel passage thereof when the connection tube is wet with fuel. The inventors have developed a connection tube to eliminate these problems.  
       FIRST EMBODIMENT  
       [0014]     Will be described a first embodiment according to the present invention, wherein the present invention is applied to a fuel filling valve as a connection tube, connected to a filler tube, in a fuel tank made of plastic mounted on a vehicle.  
         [0015]      FIG. 1  shows a fuel tank T in a partially cross-sectional view. The fuel tank T includes a tank body  1  made of plastic for storing gasoline  8  as a fuel. The tank body  1  has an opening  1   c  at a side of the tank  1  to which a fuel filling valve  2  is attached by welding. The fuel filling valve  2  includes, as the connection tube, a joint part  3  having a flange  3   a  weldable on an outside edge of the opening  1   c  and a connection tube part  3   b  extending outwardly from the flange  3   a . The fuel filing valve  2  further includes an inner tube  4  having one end (at the left in  FIG. 1 ) that includes a valve mechanism (not shown) built therein and extends to the other end thereof inside the joint part  3  with a hook  4   a  (see  FIG. 2 ). In other words, the inner tube  4  extends from the one end inside the tank body  1  through the joint part  3  and exposed to the outside as the hook  4   a . The valve mechanism has a function for preventing the fuel from reversely flowing to the filler tube H.  
         [0016]      FIG. 2  shows an enlarged cross-sectional elevation view of the filling valve  2  fixed to the tank body  1 . The tank body  1  has a sectional structure, in which an HC barrier material layer  1   b  made of EVOH (Ethylene vinyl alcohol copolymer) excellent in impermeability against HC (hydrocarbon) and the like is sandwiched between heat welding layers la made of a material which can be heat-welded such as PE (polyethylene).  
         [0017]     The joint part  3  of the fuel filling valve  2  includes the flange  3   a  attachable by heat-welding to the outside edge of the opening  1   c  and the connection tube part  3   b , extending from the flange  3   a  outwardly from the tank body  1 , to which the filler tube H (see  FIG. 1 ) externally fits. The flange  3   a  and an outer circumferential face of the connection tube part  3   b  are made of, for example, PE (polyethylene), which can be heat-welded, as a heat welding layer  3   c  which can be heat-welded on the tank body  1 . On the other hand, a part continuously formed from a side exposed to the inside of the tank body  1  and across inner circumferential face of the connection tube part  3   b  is made of the material excellent in impermeability against HC (hydrocarbon) such EVOH (Ethylene vinyl alcohol copolymer) as an HC barrier material layer  3   d . A permeability of HC (hydrocarbon) in the tank body  1  to outside of the tank body  1  is suppressed by this HC barrier material layer  3   d . The heat-welding layer  3   c  and the HC barrier material layer  3   d  are formed by coinjection molding to provide an integrated joint part  3 .  
         [0018]      FIG. 3  shows a further enlarged cross-sectional side elevation view of a part “B” of the filling valve  2  shown in  FIG. 2 . The inner tube  4  is formed to contact an inner circumferential face of the joint part  3 , namely, an inner circumferential face of the connection tube part  3   b  (the HC barrier material layer  3   d ). At a tip of the inner tube outside the tank body  1  is formed the hook  4   a  radially outwardly protruding from the tip. The hook  4   a  has a wall, radially extending from the inner tube  4 , which contacts with a tip of the connection tube part  3   b  to stop an outward movement in an axial direction of the connection tube part  3   b  (fuel filling valve). The inner tube  4  is formed of a material that cannot be welded such as POM (polyacetal). In this embodiment, the joint part  3  and the inner tube  4  are integrally formed. More specifically, the fuel filling valve  2  is integrally formed by a so-called insert molding, in which the part of POM is inserted into the joint part  3 .  
         [0019]     Here, the EVOH, which is the material of the HC barrier material layer  3   d , and the POM, which is a material of the inner tube  4 , have different swelling rates against gasoline, wherein the EVOH has a greater swelling rate than the POM. Thus, the joint part  3  and the inner tube  4  have different swelling rates around the contact faces  5   a  and  5   b  against the fuel, respectively.  
         [0020]     In consideration of this, in the present invention, at least one pair of the ends of the contact faces  5   a  and  5   b  with respect to the axial direction of the fuel filling valve  2  are made to contact with each other at slopes  6 - 1   a  and  6 - 1   b  that incline from the axial direction to provide relative displacement in the axial direction and radial direction of the fuel filling valve  2  to have hermetically, slidingly contact with each other when the joint part  3  and the inner tube  4  contact the fuel (gasoline  8 ) and thus swell differently.  
         [0021]      FIG. 3  shows a case where, as the at least one pair of ends of the contact faces  5   a  and  5   b , the ends exposed in the tank body  1  are formed to have the slopes  6 - 1   a  and  6 - 1   b . In this case, the slopes  6 - 1   a  and  6 - 1   b  radially outwardly displaces as points thereat move toward the inside of the tank body  1  (a wall of the tank body  1 ) and formed around the circumference of the inner tube  4 .  
         [0022]     As mentioned above, in the structure where the joint part  3  and the inner tube  4  are intervened with the slopes  6 - 1   a  and  6 - 1   b , if the HC barrier material layer  3   d  made of EVOH having a higher swelling rate than the POM of the inner tube  4 , deformation can be absorbed by the relative displacement between both the slopes  6 - 1   a  and  6 - 1   b  in the axial direction and the radial direction. More specifically, the slope  6 - 1   b  relatively shifts to the left in  FIG. 3  along the slope  6 - 1   a  of the inner tube  4 . In other words, the deformation of the joint part  3  caused by the difference in the swelling rate is relived between the slopes  6 - 1   a  and  6 - 1   b . In that event, the slope  6 - 1   b  pushes the slope  6 - 1   a  as it slidingly shifts, so that the slopes  6 - 1   a  and  6 - 1   b  hermetically contact. This provides a sealing characteristic at the contact faces  5   a  and  5   b . In addition, the slope  6 - 1   a  and  6 - 1   b  function as a stopper for preventing the joint part  3  from coming out of the inner tube  4 .  
         [0023]     According to this structure, the displacement is allowed in the axial direction at the slopes  6 - 1   a  and  6 - 1   b  at one end of the HC barrier material layer  3   d , although the joint part  3  (HC barrier material layer  3   d ) is limited in displacement at the other end of the HC barrier material layer  3   d . As a result, no excessive load is generated in the joint part  3  and the inner tube  4 . In addition, provided at the end of the HC barrier material layer  3   d  inside the tank body  1  (near the slopes  6 - 1   a  and  6 - 1   b ) is a relief space  7   a , so that the swelled HC barrier material layer  3   d  extends to the relief space  7   a , which allows the slopes  6 - 1   a  and  6 - 1   b  to surely relieve the deformation.  
       SECOND EMBODIMENT  
       [0024]      FIG. 4  shows a second embodiment in a case where, as the at least one pair of ends of the contact faces  5   a  and  5   b , the ends at the outside of the tank body  1  are formed to have the slopes  6 - 2   a  and  6 - 2   b . In this embodiment, the slopes  6 - 2   a  and  6 - 2   b  are formed to have radial, outward displacement as places at the slopes  6 - 2   a  and  6 - 2   b  move outwardly from the tank body  1 . The HC barrier material layer  3   d  swells relative to the inner tube  4 , so that the slope  6 - 2   b  of the HC barrier material layer  3   d  slidingly and hermetically climbs the slope  6 - 2   a  of the inner tube  4 , which relieves the stress at the slope  6 - 2   a  and the  6 - 2   b.    
         [0025]     In addition, provided above a tip of the heat-welding layer  3  and a space between the tip of the heat-welding layer  3  and the hook  4   a  outside the tank body  1  is a relief space  7   b , so that the swelled HC barrier material layer  3   d  extends to the relief space  7   b , which allows the slopes  6 - 2   a  and  6 - 2   b , and a corresponding slope  6 - 2   c  of the connection tube  3   b  to surely relieve the deformation.  
         [0026]     In the first and second embodiments, the joint part  3  and the inner tube  4  are integrally formed. However, the present invention is applicable to a case where the joint part  3  and the inner tube  4  are separately formed. Further, the slopes  6 - 1   a ,  6 - 1   b ,  6 - 2   a , and  6 - 2   b  may be formed at the both ends of the fuel filling tube  2 .  
         [0027]     Further, in the above-described embodiment, the fuel tank T is used in the automobile. However, the present invention is applicable to fuel tanks for other vehicle, ships, and aircraft and for an apparatus that stores a fuel.  
         [0028]     In the first embodiment, the inner tube  4  has a wall perpendicular to the axial direction at the one end of the inner tube  4  (at the hook  4   a ), outwardly extending from the inner tube  4 , to stop an outward movement (rightward in  FIG. 3 ) of the connection tube part  3   b . The hook  4   a  includes a taper, connected to the wall, extending in the axial direction to a tip of the inner tube  4  to receive and hook the external filler tube H.  
         [0029]     In the first embodiment, the connection tube part  3   b  extends from the flange  3   a  along the inner tube  4  to cover the inner tube  4  as an outer tube that sandwiches the slope  6 - 1   b  of the HC barrier material layer with the slope  6 - 1   a  to generate a pressure from the slope  6 - 1   b  to the slope  6 - 1   a  to provide hermetical sealing with a pressure between the slopes  6 - 1   a  and  6 - 1   b . In the first embodiment, the connection tube part  3   b  extends from the flange  3   a  along the inner tube  4  to cover the inner tube  4  as an outer tube that sandwiches the slope  6 - 1   b  of the HC barrier material layer  3   d  with the slope  6 - 1   a  to generate a pressure from the slope  6 - 1   b  to the slope  6 - 1   a  to provide hermetical sealing between the slopes  6 - 1   a  and  6 - 1   b.    
         [0030]     In the first and second embodiments, the inner tube  4  comprises a non-weldable layer which is not weldable on the fuel tank body  1 , wherein the non-weldable layer comprises polyacetal.  
         [0031]     In the second embodiment, the connection part  3   b  extends along the inner tube  4  to cover the inner tube  4  as the outer tube that sandwiches the slope  6 - 2   b  of the HC barrier material layer  3   d  with the slope  6 - 2   a  to generate a pressure from the slope  6 - 2   b  to the slope  6 - 2   a  to provide hermetical sealing with a pressure between the slopes  6 - 1   a  and  6 - 1   b.