Opening structure of a fuel tank

Abstract

The present invention is directed to an opening structure of a fuel tank having a fuel tank wall made of a plurality of plastic layers with an opening portion formed to be integral with the fuel tank wall. The opening structure includes a cylindrical portion extended from the opening portion outward of the fuel tank wall, an overlapping portion extended from an end of the cylindrical portion to enlarge the diameter of the opening portion and bent at a bent portion to form an outer surface parallel with an opening end surface of the opening portion, and a compressed portion with at least a portion of the overlapping portion compressed in a direction perpendicular to the opening end surface of the opening portion. The opening structure may further include an annular member which is disposed around the opening portion to be in contact with the overlapping portion and the cylindrical portion. The plastic layers may include at least an outer layer, an inner layer and an intermediate layer, and the outermost end of the intermediate layer may be positioned at the compressed portion.

What is claimed is:  
     
         1 . An opening structure of a fuel tank having a fuel tank wall made of a plurality of plastic layers, with an opening portion formed to be integral with said fuel tank wall, comprising: 
 a cylindrical portion extended from said opening portion outward of said fuel tank wall;    an overlapping portion extended from an end of said cylindrical portion to enlarge the diameter of said opening portion and bent at a bent portion to form an outer surface parallel with an opening end surface of said opening portion; and    a compressed portion with at least a portion of said overlapping portion compressed in a direction perpendicular to the opening end surface of said opening portion.    
     
     
         2 . The opening structure of the fuel tank according to  claim 1 , further comprising an annular member disposed around said opening portion to be in contact with said overlapping portion and said cylindrical portion.  
     
     
         3 . The opening structure of the fuel tank according to  claim 1 , wherein said compressed portion provides an annular groove placed outward of said opening portion in a radial direction of said cylindrical portion.  
     
     
         4 . The opening structure of the fuel tank according to  claim 1 , wherein said compressed portion provides an annular groove placed inward of said opening portion in a radial direction of said cylindrical portion.  
     
     
         5 . The opening structure of the fuel tank according to  claim 1 , wherein said plastic layers includes at least an outer layer, an inner layer and an intermediate layer, and wherein the outermost end of said intermediate layer is positioned at said compressed portion.  
     
     
         6 . The opening structure of the fuel tank according to  claim 5 , further comprising an annular member disposed around said opening portion, said annular member having a step portion formed inward of said annular member in a radial direction thereof to contact with at least said compressed portion.  
     
     
         7 . The opening structure of the fuel tank according to  claim 6 , wherein said bent portion is formed with a lifted wall portion extending parallel with the side surface of said cylindrical portion.  
     
     
         8 . The opening structure of the fuel tank according to  claim 5 , wherein said bent portion is formed with a lifted wall portion extending parallel with the side surface of said cylindrical portion.  
     
     
         9 . A method for producing a fuel tank by forming a fuel tank wall with a plurality of plastic layers through blow molding, and forming an opening portion to be integral with said fuel tank wall, comprising: 
 forming a cylindrical portion extended from said opening portion outward of said fuel tank wall, when said fuel tank wall is formed by blow molding;    forming at least a potion of said cylindrical portion to be bulged outward thereof in a radial direction thereof, to provide a bulged portion;    pressing said bulged portion to form a bent portion bent at the outward of said opening portion in a radial direction thereof, to form an overlapping portion extended from an end of said cylindrical portion to form an outer surface parallel with an opening end surface of said opening portion; and    compressing at least a portion of said overlapping portion to be compressed, to produce a compressed portion.    
     
     
         10 . The method according to  claim 9 , wherein said compressed portion is formed outward of said opening portion in a radial direction of said cylindrical portion.  
     
     
         11 . The method according to  claim 9 , wherein said compressed portion is formed inward of said opening portion in a radial direction of said cylindrical portion.  
     
     
         12 . The method according to  claim 9 , wherein the blow molding is performed, with an annular member placed around said opening portion, to form said cylindrical member inside of said annular member.  
     
     
         13 . The method according to  claim 12 , wherein said compressed portion is formed outward of said opening portion in a radial direction of said cylindrical portion.  
     
     
         14 . The method according to  claim 12 , wherein said compressed portion is formed inward of said opening portion in a radial direction of said cylindrical portion.  
     
     
         15 . The method according to  claim 9 , wherein said plastic layers includes at least an outer layer, an inner layer and an intermediate layer, and wherein the outermost end of said intermediate layer is positioned at said compressed portion.  
     
     
         16 . The method according to  claim 15 , wherein an annular member disposed around said opening portion, said annular member having a step portion formed inward of said annular member in a radial direction thereof to contact with at least said compressed portion.  
     
     
         17 . The method according to  claim 16 , wherein said bent portion is formed with a lifted wall portion extending parallel with the side surface of said cylindrical portion.  
     
     
         18 . The method according to  claim 15 , wherein said bent portion is formed with a lifted wall portion extending parallel with the side surface of said cylindrical portion.