Patent Publication Number: US-2021188082-A1

Title: Resin filler tube and manufacturing method for the same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority based on Japanese Patent Application No. 2019-231091 filed on Dec. 23, 2019, the entire contents of which are incorporated by reference herein. 
     1. TECHNICAL FIELD 
     The present invention relates to a resin filler tube and a manufacturing method for the resin filler tube. 
     2. BACKGROUND ART 
     WO2010015295A1 discloses that an outer circumferential edge of an opening hole of a fuel tank and a flange of a filler tube are fixed to each other by a clamp ring. An O-ring for sealing is disposed between an inner circumferential surface of the opening hole of the fuel tank and an outer circumferential surface of the filler tube. 
     JP2018-118498A discloses that an outer circumferential edge of an opening hole of a resin fuel tank and an axial end face of a flange of a resin filler tube are joined to each other by welding. The outer face of the resin filler tube has an outermost layer formed by an outermost layer material over the entire length. The outermost layer of the flange is welded to the fuel tank. Furthermore, a material having preferable weldability is used as the outermost layer material, whereby performance such as a welding strength of a weld surface is enhanced. 
     JP2018-69786A also discloses that an outer circumferential edge of an opening hole of a fuel tank and an axial end face of a flange of a filler tube are joined to each other by welding. 
     SUMMARY 
     JP2018-118498A discloses that a tubular material is extrusion-molded by an extruder and brought into close contact with inner faces of a plurality of split molds to mold the outer face of the flange with the outermost layer material over the entire length. The thickness of the flange is made greater than the thickness of a tubular body (a tubular portion adjacent to the flange in the axial direction) of the resin filler tube in order to assure a sufficient welding strength. 
     In this manufacturing method, for example, a speed at which the split molds are moved is reduced during molding of the flange portion, whereby the thickness of the flange is made greater than the thickness of the tubular body. That is, the speed at which the split molds are moved needs to be reduced from a speed for molding the tubular body to a speed for molding the flange portion, or the speed at which the split molds are moved needs to be increased from the speed for molding the flange portion to the speed for molding the tubular body. 
     In this manufacturing method, the thickness of the resin filler tube is not abruptly changed but is gradually changed. Therefore, the thickness is gradually changed at positions of the tubular body on the flange side. In a case where the thickness is increased at a portion at which the thickness of the tubular body is gradually changed, the thickness is increased inward in the radial direction at the portion at which the thickness of the tubular body is gradually changed, so that the inner diameter is reduced at the portion at which the thickness of the tubular body is gradually changed. The inner diameter of the tubular body is of importance because the inner diameter of the tubular body affects fuel flow performance. Therefore, the flange needs to be molded in consideration of the inner diameter of the tubular body. 
     An object of the present invention is to provide a resin filler tube that has, near a flange, an inner diameter that is not less than an inner diameter of a tubular body as a reference, and a manufacturing method for manufacturing the resin filler tube. 
     (1. Resin Filler Tube) 
     A resin filler tube is directed to a resin filler tube to be welded to an outer circumferential edge of an opening hole of a fuel tank. The resin filler tube includes: a tubular body having an outermost layer formed by using an outermost layer material, and one or more inner layers each formed by using an inner layer material; a flange having a plurality of layers that are of same kinds as those of the tubular body, the flange having a diameter greater than an outer diameter of the tubular body, a thickness greater than a thickness of the tubular body, and a predetermined width in an axial direction, the flange having a first axial end face forming a weld surface to be welded to the outer circumferential edge of the opening hole of the fuel tank; and a base-end-side reverse tapered portion having a plurality of layers that are of same kinds as those of the tubular body, the base-end-side reverse tapered portion connecting between an end of the tubular body on the fuel tank side and an end of an outer circumferential surface of the flange on a side opposite to the fuel tank side, the base-end-side reverse tapered portion being reversely tapered so as to increase a diameter toward the flange. The base-end-side reverse tapered portion is formed so as to have an inner diameter that is not less than an inner diameter of the tubular body over an entire range in the axial direction. 
     The resin filler tube described above includes the base-end-side reverse tapered portion. The base-end-side reverse tapered portion functions as a region in which the thickness is gradually changed between the tubular body and the flange in the axial direction. Accordingly, the base-end-side reverse tapered portion is formed so as to have the inner diameter that is not less than the inner diameter of the tubular body over the entire range in the axial direction. As a result, the inner diameter is inhibited, near the flange, from becoming less than the reference inner diameter (the inner diameter of the tubular body) in a range from the tubular body to the flange. Accordingly, fuel flow performance is prevented from being affected near the flange, and fuel flow performance exhibited by the resin filler tube indicates a desired value. 
     (2. Manufacturing Method for Resin Filler Tube) 
     A resin filler tube manufacturing method is directed to a manufacturing method for manufacturing the above-described resin filler tube. The manufacturing method includes: extruding a tubular material having a plurality of layers by an extruder; and forming the resin filler tube by bringing the tubular material into close contact with an inner face formed by a plurality of split molds while sequentiallymoving each of the plurality of split molds in a direction in which the tubular material is extruded, such that the resin filler tube has an outer face corresponding to the inner face. 
     In the forming of the resin filler tube, the tubular body has a predetermined thickness by setting moving speeds of the split molds to a first speed when the tubular material is brought into close contact with a portion of the split molds for forming the tubular body. In the forming of the resin filler tube, the flange has the thickness greater than the thickness of the tubular body by setting moving speeds of the split molds to a second speed lower than the first speed when the tubular material is brought into close contact with a portion of the split molds for forming the flange. In the forming of the resin filler tube, a thickness of the base-end-side reverse tapered portion is increased by reducing moving speeds of the split molds from the first speed to the second speed when the tubular material is brought into close contact with a portion of the split molds for forming the base-end-side reverse tapered portion. 
     The above-described resin filler tube is manufactured by the manufacturing method. As a result, the above-described effect is exhibited. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates a fuel line; 
         FIG. 2  is an axial cross-sectional view of a filler tube shown in  FIG. 1  in a linearly extending state; 
         FIG. 3  illustrates a first example of a second end portion of the filler tube, illustrates an enlarged cross-section of a portion III in  FIG. 2 , and also illustrates a state where a flange of the filler tube is welded to an outer circumferential edge of an opening hole of a fuel tank; 
         FIG. 4  illustrates a second example of the second end portion of the filler tube, illustrates an enlarged cross-section of the portion III in  FIG. 2 , and also illustrates a state where the flange of the filler tube is welded to the outer circumferential edge of the opening hole of the fuel tank; 
         FIG. 5  is a flow chart showing a method for manufacturing a tank unit (fuel tank, filler tube, check valve); 
         FIG. 6  is a plan view of a manufacturing apparatus for manufacturing the filler tube; and 
         FIG. 7  is a cross-sectional view taken along a line VII-VII in  FIG. 6 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     (1. Structure of Fuel Line  1 ) 
     A structure of a fuel line  1  will be described with reference to  FIG. 1 . The fuel line  1  is a path extending from an oil filler port  10  through a fuel tank  20  to an internal combustion engine (not shown) in an automobile. In the present embodiment, a portion of the fuel line  1  from the oil filler port  10  to the fuel tank  20  will be described. 
     The fuel line  1  includes at least the oil filler port  10 , the fuel tank  20 , a resin filler tube  30 , and a check valve  40 . In the present embodiment, the fuel line  1  further includes a breather line  50 . 
     The oil filler port  10  is disposed near the outer face of an automobile, and allows an oil supply nozzle (not shown) to be inserted therein. The oil filler port  10  is made of resin or metal. The oil filler port  10  is either an oil filler port type having an oil filler cap attached thereto, or a capless oil filler port type which does not have an oil filler cap attached thereto. 
     The fuel tank  20  is molded by using thermoplastic resin, and stores liquid fuel such as gasoline. The fuel tank  20  includes, for example, a plurality of kinds of resin layers. The liquid fuel stored in the fuel tank  20  is fed to the not-illustrated internal combustion engine, and is used for driving the internal combustion engine. The fuel tank  20  has an opening hole  21  for feeding fuel. The opening hole  21  for feeding fuel is formed in, for example, the upper face or the side face of the fuel tank  20 . 
     The filler tube  30  is molded by using thermoplastic resin, and connects between the oil filler port  10  and the fuel tank  20 . The filler tube  30  has one or more bent portions for routing, in general. The filler tube  30  is formed by one member or is formed by a plurality of members joined to each other. In the present embodiment, an example in which the filler tube  30  is integrally formed by one member over the entire length, will be described. 
     A first end portion  31  of the filler tube  30  is press-fitted to a tubular portion  11  of the oil filler port  10 . A second end portion  32  of the filler tube  30  is welded to the outer circumferential edge of the opening hole  21  in the outer face of the fuel tank  20 . In the present embodiment, a part of the second end portion  32  is inserted in the opening hole  21  of the fuel tank  20 . 
     The oil supply nozzle is inserted in the oil filler port  10  and liquid fuel is fed through the oil supply nozzle, whereby the liquid fuel passes through the filler tube  30  and is stored in the fuel tank  20 . In a case where the fuel tank  20  has been filled with liquid fuel, liquid fuel is stored in the filler tube  30 , and the liquid fuel comes into contact with the tip of the oil supply nozzle to automatically stop feeding liquid fuel through the oil supply nozzle. 
     The check valve  40  is disposed near the opening hole  21  of the fuel tank  20 . The check valve  40  is fixed to the second end portion  32  of the filler tube  30 , or fixed between the filler tube  30  and the opening hole  21  of the fuel tank  20 . When liquid fuel is fed from the filler tube  30  into the fuel tank  20 , the liquid fuel passes through the check valve  40 . In this case, in a case where liquid fuel is fed from the filler tube  30  into the fuel tank  20 , backflow of the liquid fuel in the fuel tank  20  toward the filler tube  30  is prevented. 
     The breather line  50  connects between the oil filler port  10  and the fuel tank  20 , and is disposed parallel to the filler tube  30 . The breather line  50  is a line for discharging fuel vapor in the fuel tank  20  to the outside of the fuel tank  20  when liquid fuel is fed through the filler tube  30  into the fuel tank  20 . 
     (2. Schematic Structure of Filler Tube  30 ) 
     The schematic structure of the filler tube  30  will be described with reference to  FIG. 2 . The filler tube  30  is structured to have a plurality of layers made of different kinds of thermoplastic resins. As shown in  FIG. 2 , the filler tube  30  includes the first end portion  31  formed at one end portion in the tube axis direction, the second end portion  32  formed at the other end portion in the tube axis direction, and an intermediate portion  33  connecting between the first end portion  31  and the second end portion  32 . 
     The first end portion  31  is formed in a cylindrical shape, and fitted to the outer face of the tubular portion  11  of the oil filler port  10 . The first end portion  31  is formed so as to be deformed more easily than the tubular portion  11  of the oil filler port  10 . Therefore, the first end portion  31  is fitted to the tubular portion  11  of the oil filler port  10  in a state where the first end portion  31  is deformed to increase the diameter. 
     The second end portion  32  is formed in a tubular shape, and is welded to the outer circumferential edge of the opening hole  21  of the fuel tank  20 . The second end portion  32  includes a flange  32   b  that protrudes radially outward from a tubular body  32   a  over the entire circumference. The flange  32   b  is welded to the fuel tank  20 . That is, the flange  32   b  of the second end portion  32  functions so as to assure a sufficient weld area for welding to the fuel tank  20 . The second end portion  32  further includes a leading end tubular portion  32   d  extending to be closer to the leading end side of the filler tube  30  than the flange  32   b . Apart of the leading end tubular portion  32   d  is inserted in the opening hole  21  of the fuel tank  20 . The check valve  40  is attached to the inner circumferential surface of the leading end tubular portion  32   d.    
     The intermediate portion  33  is designed as appropriate so as to form a path according to relative positions of the oil filler port  10  and the fuel tank  20  and a distance therebetween, a layout of peripheral devices, and the like. In the present embodiment, the intermediate portion  33  includes a first tubular portion  33   a  that does not have a bellows-like shape, a bellows portion  33   b , and a second tubular portion  33   c  that does not have a bellows-like shape. The first tubular portion  33   a  is connected to the first end portion  31 , and is previously bent in a mid-portion in the tube axis direction. The bellows portion  33   b  is connected to the first tubular portion  33   a , and formed in a bellows-like tubular shape so as to be bendable as appropriate. The second tubular portion  33   c  is connected to the bellows portion  33   b , and is also connected to the second end portion  32 . The second tubular portion  33   c  is substantially formed in a cylindrical shape. 
     In an example other than the above-described example, the intermediate portion  33  of the filler tube  30  includes, for example, a plurality of the bellows portions, the entirety of the intermediate portion  33  is formed of the bellows portion, or the intermediate portion  33  includes no bellows portions. The first tubular portion  33   a  does not have a bellows-like shape and is bent. However, in another example, the first tubular portion  33   a  linearly extends. 
     (3. Layer Structure of Filler Tube  30 ) 
     A layer structure of the filler tube  30  will be described with reference to  FIG. 3  and  FIG. 4 .  FIG. 3  and  FIG. 4  are each an enlarged cross-sectional view of a portion III in  FIG. 2 , and are axial cross-sectional views of the second end portions  32  of the filler tube  30  according to a first example and a second example. The filler tube  30  has a uniform layer structure over the entire length. Therefore, portions other than the second end portion  32  of the filler tube  30  have the same layer structure. That is, in the filler tube  30 , all of the first end portion  31 , the second end portion  32 , and the intermediate portion  33  have the same layer structure. 
     As shown in  FIG. 3  and  FIG. 4 , the filler tube  30  is structured to have a plurality of layers made of different kinds of thermoplastic resins. The filler tube  30  includes, for example, an innermost layer  61 , an inner adhesive layer  62 , an intermediate layer  63 , an outer adhesive layer  64 , and an outermost layer  65  in order, respectively, from the inner layer side. The filler tube  30  is structured to have the plurality of layers over the entire length. The structure of the filler tube  30  is not limited to the five layer structure. In another example, the number of the layers of the filler tube  30  is not greater than four or not less than six. 
     The layers  61  to  64  other than the outermost layer  65  are collectively referred to as inner layers. The inner layers  61  to  64  are formed of inner layer materials. The outermost layer  65  is formed of an outermost layer material. The number of the inner layers  61  to  64  is not less than one. In the present embodiment, the filler tube  30  includes the four inner layers  61  to  64 . Each layer will be described below. 
     The innermost layer  61  comes into contact with liquid fuel (gasoline), and a gasoline-resistant material is thus used as the innermost layer material (one of the inner layer materials) of the innermost layer  61 . The innermost layer  61  preferably has a catching force (disengagement preventing force) for catching the tubular portion  11  of the oil filler port  10  in the axial direction in a state where the first end portion  31  is press-fitted to the tubular portion  11  of the oil filler port  10 . In this case, a material having sealability is used as the innermost layer material of the innermost layer  61 . The innermost layer material of the innermost layer  61  essentially contains, for example, high density polyethylene (HDPE). However, another material is allowed to be used for the innermost layer  61  as long as the material exhibits the above-described performance. 
     The intermediate layer  63  is disposed on the outer circumference side of the innermost layer  6   l . The intermediate layer material (one of the inner layer materials) of the intermediate layer is, for example, resistant to fuel permeation. For the intermediate layer  63 , for example, a material that essentially contains either ethylene-vinyl alcohol copolymer (EVOH) or polyamide (PA) is preferably used as the intermediate layer material resistant to fuel permeation. However, another material is allowed to be used for the intermediate layer  63  as long as the material exhibits the above-described performance. 
     The outermost layer  65  is disposed on the outer circumference side of the intermediate layer  63 . The outermost layer  65  protects the intermediate layer  63 . The outermost layer  65  forms the outermost surface of the filler tube  30 . Therefore, for example, a material having impact resistance, weather resistance, and chemical resistance is preferably used as the outermost layer material of the outermost layer  65 . In this case, for the outermost layer  65 , a material that essentially contains either high density polyethylene (HDPE) or polyamide (PA) is used as the outermost layer material. 
     Furthermore, in the present embodiment, the outermost layer  65  forms a layer to be welded to the fuel tank  20 . Therefore, a material having preferable weldability with respect to a material of the outer face of the fuel tank  20  is preferably used for the outermost layer material of the outermost layer  65 . Particularly, the outermost layer material of the outermost layer  65  and the material of the outer face of the fuel tank  20  are preferably of the same kind. However, another material is allowed to be used for the outermost layer  65  as long as the material exhibits the above-described performance. 
     The inner adhesive layer  62  is a layer for adhering the outer circumferential surface of the innermost layer  61  and the inner circumferential surface of the intermediate layer  63  to each other. The outer adhesive layer  64  is a layer for adhering the outer circumferential surface of the intermediate layer  63  and the inner circumferential surface of the outermost layer  65  to each other. For example, a material that essentially contains modified polyethylene (modified PE) is preferably used as the inner adhesive layer material (one of the inner layer materials) of the inner adhesive layer  62  and the outer adhesive layer material (one of the inner layer materials) of the outer adhesive layer  64 . However, in a case where at least one of the innermost layer  61  and the intermediate layer  63  has adhesiveness to the other thereof, the inner adhesive layer  62  is unnecessary. In a case where at least one of the intermediate layer  63  and the outermost layer  65  has adhesiveness to the other thereof, the outer adhesive layer  64  is unnecessary. 
     (4. Layer Structure of Fuel Tank  20 ) 
     The layer structure of the fuel tank  20  will be described with reference to  FIG. 3  and  FIG. 4 .  FIG. 3  and  FIG. 4  are each a cross-sectional view of a portion near the opening hole  21  of the fuel tank  20 . The fuel tank  20  is structured to have a plurality of layers made of different kinds of thermoplastic resins. The fuel tank  20  may be structured to have, for example, five layers (innermost layer, inner adhesive layer, intermediate layer, outer adhesive layer, and outermost layer), similarly to the filler tube  30 . 
     In  FIG. 3  and  FIG. 4 , the fuel tank  20  has a three layer structure, that is, includes an innermost layer  20   a , an intermediate layer  20   b , and an outermost layer  20   c . The innermost layer  20   a , the intermediate layer  20   b , and the outermost layer  20   c  are, for example, formed in manners similar to manners in which the innermost layer  61 , the intermediate layer  63 , and the outermost layer  65 , respectively, of the filler tube  30  are formed. The structure of the fuel tank  20  is not limited to the three layer structure. In another example, the number of the layers of the fuel tank  20  may be two or not less than four. 
     (5. First Example of Second End Portion  32  of Filler Tube  30 ) 
     Next, a first example of the second end portion  32  of the filler tube  30  will be described with reference to  FIG. 3 . The second end portion  32  includes the tubular body  32   a , the flange  32   b , a base-end-side reverse tapered portion  32   c , the leading end tubular portion  32   d , and a leading-end-side tapered portion  32   e.    
     The tubular body  32   a  is formed in a tubular shape, and forms a portion of the second end portion  32  on the first end portion  31  side and the intermediate portion  33  side. That is, one end (not shown, the end portion located rightward of the region in  FIG. 3 ) of the tubular body  32   a  is connected to the intermediate portion  33  of the filler tube  30 . At least a portion of the tubular body  32   a  on the leading end side (the fuel tank  20  side) of the second end portion  32  is formed in a cylindrical shape. Needless to say, the tubular body  32   a  is allowed to be formed in a cylindrical shape having a constant diameter over the entire length. The tubular body  32   a  is a portion in a range rightward of a position P 1  on the inner circumferential surface in  FIG. 3 . 
     The tubular body  32   a  is structured to have the plurality of layers ( 61  to  65 ) described above, from the inner face toward the outer face. The tubular body  32   a  has an outer diameter Doa and an inner diameter Dia. In the description herein, in the second end portion  32 , the inner diameter Dia of the tubular body  32   a  is a reference inner diameter for determining fuel flow performance. That is, the inner diameter of the second end portion  32  needs to be not less than the reference inner diameter Dia over the entire length. 
     The flange  32   b  is disposed on the fuel tank  20  side than the tubular body  32   a . The flange  32   b  protrudes radially outward relative to the tubular body  32   a  over the entire circumference. The outer face of the flange  32   b  includes a first end face  32   b   1  in the axial direction and an outer circumferential surface  32   b   2 . In the present embodiment, the flange  32   b  is included in an axial range B. That is, in  FIG. 3 , the flange  32   b  is a portion in a range between a position P 3  and a position P 4  on the inner circumferential surface. 
     The first end face  32   b   1  of the flange  32   b  forms a weld surface to be welded to the outer circumferential edge of the opening hole  21  of the fuel tank  20 . The first end face  32   b   1  is formed in a flat surface that is substantially orthogonal to the center axis of the second end portion  32  of the filler tube  30 . The outer circumferential surface  32   b   2  of the flange  32   b  has a substantially cylindrical shape. 
     The flange  32   b  is structured to have the plurality of layers ( 61  to  65 ) that are of the same kinds as those of the tubular body  32   a , from the inner face toward the outer face. Accordingly, the first end face  32   b   1  and the outer circumferential surface  32   b   2  that form the flange  32   b  are all molded by using the outermost layer material only. That is, a melted portion of the first end face  32   b   1  by welding is formed of the outermost layer material only. 
     The outer circumferential surface  32   b   2  of the flange  32   b  has an outer diameter Dob greater than the outer diameter Doa of the tubular body  32   a . The flange  32   b  is filled over the entire range, in a radial range of the first end face  32   b   1  that is welded to the fuel tank  20 . The flange  32   b  is formed to be thicker than the tubular body  32   a.    
     Dib represents a maximum inner diameter of the flange  32   b . In the present embodiment, the maximum inner diameter Dib of the flange  32   b  is less than an inner diameter Dit of the opening hole  21  of the fuel tank  20 . However, the present invention is not limited thereto as long as the most of the radial range in which the to-be-welded first end face  32   b   1  of the flange  32   b  is welded to the fuel tank  20 , is filled. In this case, the maximum inner diameter Dib of the flange  32   b  is allowed to be slightly greater than the inner diameter Dit of the opening hole  21  of the fuel tank  20 . 
     A minimum thickness of the flange  32   b  is □ (Dob-Dib)/2□, and is greater than a thickness □ (Doa-Dia)/2□ of the tubular body  32   a . The flange  32   b  has a predetermined width (length of the axial range B) in the axial direction. The width of the flange  32   b  is less than the minimum thickness □ (Dob-Dib)/2□. 
     The base-end-side reverse tapered portion  32   c  connects between the tubular body  32   a  and the flange  32   b . More specifically, the base-end-side reverse tapered portion  32   c  connects between the end of the tubular body  32   a  on the fuel tank  20  side (leading end side of the second end portion  32 ) and the end of the outer circumferential surface  32   b   2  of the flange  32   b  on the side opposite to the fuel tank  20  side. In the present embodiment, the base-end-side reverse tapered portion  32   c  is included in an axial range C. That is, in  FIG. 3 , the base-end-side reverse tapered portion  32   c  is a portion in a range between the position P 1  and a position P 3  on the inner circumferential surface. 
     The length of the axial range C of the base-end-side reverse tapered portion  32   c  is greater than the length of the axial range B of the flange  32   b . The base-end-side reverse tapered portion  32   c  is structured to have the plurality of layers ( 61  to  65 ) that are of the same kinds as those of the tubular body  32   a , from the inner face toward the outer face. 
     The base-end-side reverse tapered portion  32   c  is reversely tapered so as to increase the diameter toward the flange  32   b . More specifically, the outer circumferential surface of the base-end-side reverse tapered portion  32   c  is reversely tapered over the entire range in the axial direction so as to increase the diameter from the tubular body  32   a  toward the flange  32   b . The thickness of the base-end-side reverse tapered portion  32   c  is increased from the tubular body  32   a  toward the flange  32   b.    
     The base-end-side reverse tapered portion  32   c  is formed so as to have an inner diameter that is not less than the inner diameter Dia of the tubular body  32   a  over the entire range in the axial direction. The inner circumferential surface of the base-end-side reverse tapered portion  32   c  has reverse tapered portions Ti 1 , Ti 2  so as to increase the diameter from the tubular body  32   a  toward the flange  32   b . Accordingly, a diameter increase start position Ps 1  of the reverse tapered portion Ti 1  on the inner circumferential surface is included in the range of the base-end-side reverse tapered portion  32   c  in the axial direction, and is closer to the tubular body  32   a  than the flange  32   b.    
     The base-end-side reverse tapered portion  32   c  includes a plurality of reverse tapered portions. In the present embodiment, the base-end-side reverse tapered portion  32   c  includes a first-stage reverse tapered portion  32   c   1  and a second-stage reverse tapered portion  32   c   2 . The first-stage reverse tapered portion  32   c   1  and the second-stage reverse tapered portion  32   c   2  are disposed in order, respectively, from the tubular body  32   a  side. In another example, the base-end-side reverse tapered portion  32   c  includes three or more reverse tapered portions. 
     The first-stage reverse tapered portion  32   c   1  is connected to the end of the tubular body  32   a  on the fuel tank  20  side, and has a diameter increased toward the flange  32   b . The first-stage reverse tapered portion  32   c   1  is included in an axial range C 1 . That is, in  FIG. 3 , the first-stage reverse tapered portion  32   c   1  is a portion in a range between the position P 1  and a position P 2  on the inner circumferential surface. The length of the axial range C 1  of the first-stage reverse tapered portion  32   c   1  is greater than the length of the axial range B of the flange  32   b . The diameter increase start position Ps 1  on the inner circumferential surface is in the axial range C 1  of the first-stage reverse tapered portion  32   cl . That is, a portion of the first-stage reverse tapered portion  32   c   1  from the position P 1  to the diameter increase start position Ps 1  is formed so as to have the same inner diameter as the inner diameter Dia of the tubular body  32   a.    
     A taper angle fc 1  of the outer circumferential surface of the first-stage reverse tapered portion  32   c   1  is set such that an angle (acute angle) of the outer circumferential surface of the first-stage reverse tapered portion  32   cl  relative to the center axis of the tubular body  32   a  is not greater than 45°. Particularly, the taper angle fc 1  of the outer circumferential surface of the first-stage reverse tapered portion  32   c   1  is preferably not greater than 30° and more preferably not greater than 20°. A taper angle of the reverse tapered portion Ti 1  on the inner circumferential surface of the first-stage reverse tapered portion  32   c   1  is slightly less than the taper angle fc 1  of the outer circumferential surface. Accordingly, the thickness of the first-stage reverse tapered portion  32   c   1  is increased from the tubular body  32   a  toward the flange  32   b.    
     The second-stage reverse tapered portion  32   c   2  connects between the end of the first-stage reverse tapered portion  32   c   1  and the end of the outer circumferential surface of the flange  32   b  on the side opposite to the fuel tank  20  side. The second-stage reverse tapered portion  32   c   2  is included in an axial range C 2 . That is, in  FIG. 3 , the second-stage reverse tapered portion  32   c   2  is a portion in a range between the position P 2  and the position P 3  on the inner circumferential surface. The length of the axial range C 2  of the second-stage reverse tapered portion  32   c   2  is approximately equal to the length of the axial range B of the flange  32   b  or slightly greater than the length of the axial range B. 
     The second-stage reverse tapered portion  32   c   2  has a diameter increased toward the flange  32   b . Furthermore, the second-stage reverse tapered portion  32   c   2  includes the outer circumferential surface having a taper angle fc 2  greater than the taper angle fc 1  of the outer circumferential surface of the first-stage reverse tapered portion  32   c   1 . The taper angle fc 2  of the outer circumferential surface of the second-stage reverse tapered portion  32   c   2  is set such that an angle (acute angle) of the outer circumferential surface of the second-stage reverse tapered portion  32   c   2  relative to the center axis of the tubular body  32   a  is not less than 45°. Particularly, the taper angle fc 2  of the outer circumferential surface of the second-stage reverse tapered portion  32   c   2  is preferably not less than 50° and more preferably not less than 55°. 
     A taper angle of the reverse tapered portion Ti 2  on the inner circumferential surface of the second-stage reverse tapered portion  32   c   2  is slightly less than the taper angle fc 2  of the outer circumferential surface. Accordingly, the thickness of the second-stage reverse tapered portion  32   c   2  is increased toward the flange  32   b.    
     The leading end tubular portion  32   d  is located on the leading end side of the filler tube  30 . The check valve  40  is attached to the inner circumferential surface of the leading end tubular portion  32   d . The leading end tubular portion  32   d  is structured to have the plurality of layers ( 61  to  65 ) that are of the same kinds as those of the tubular body  32   a , from the inner face toward the outer face. 
     The leading end tubular portion  32   d  is formed so as to have an outer diameter Dod that is less than the inner diameter Dit of the inner circumferential surface of the opening hole  21  of the fuel tank  20  over the entire length. That is, a gap is formed between the outer circumferential surface of the leading end tubular portion  32   d  and the inner circumferential surface of the opening hole  21  over the entire circumference. 
     The leading end tubular portion  32   d  is formed in a cylindrical shape having a constant diameter over the entire length, a tubular shape having a plurality of diameters, or a tubular shape having a tapered portion. In the present embodiment, the leading end tubular portion  32   d  is formed in a cylindrical shape having a constant diameter. An inner diameter Did of the leading end tubular portion  32   d  is equal to the inner diameter Dia (reference inner diameter) of the tubular body  32   a . The outer diameter Dod of the leading end tubular portion  32   d  is equal to the outer diameter Doa of the tubular body  32   a.    
     The leading end tubular portion  32   d  is located radially inward of the opening hole  21  of the fuel tank  20 , or located inward of the inner wall surface of the fuel tank  20 .  FIG. 3  shows a case where the leading end tubular portion  32   d  is located inward of the inner wall surface of the fuel tank  20 . 
     The leading-end-side tapered portion  32   e  connects between a radially inner portion of the flange  32   b  and the end of the leading end tubular portion  32   d  on the tubular body  32   a  side. In the present embodiment, the leading-end-side tapered portion  32   e  is included in an axial range E. That is, in  FIG. 3 , the leading-end-side tapered portion  32   e  is a portion in a range between the position P 4  and a position P 5  on the inner circumferential surface. 
     The length of the axial range E of the leading-end-side tapered portion  32   e  is greater than the length of the axial range B of the flange  32   b . The leading-end-side tapered portion  32   e  is structured to have the plurality of layers ( 61  to  65 ) that are of the same kinds as those of the tubular body  32   a , from the inner face toward the outer face. 
     The leading-end-side tapered portion  32   e  is tapered so as to increase the diameter toward the flange  32   b  side. More specifically, the outer circumferential surface of the leading-end-side tapered portion  32   e  is tapered so as to increase the diameter from the leading end tubular portion  32   d  toward the flange  32   b  over the entire range in the axial direction. The leading-end-side tapered portion  32   e  is formed so as to have one tapered portion, or two or more stages of tapered portions. 
     The leading-end-side tapered portion  32   e  is formed so as to have an inner diameter that is not less than the inner diameter Did of the leading end tubular portion  32   d  over the entire range in the axial direction. The inner circumferential surface of the leading-end-side tapered portion  32   e  has a tapered portion Ti 3  having a diameter increased from the leading end tubular portion  32   d  toward the flange  32   b . Accordingly, a diameter increase start position Ps 3  of the tapered portion Ti 3  on the inner circumferential surface is included in a range of the leading-end-side tapered portion  32   e  in the axial direction, and is closer to the leading end tubular portion  32   d  than the flange  32   b.    
     A taper angle fe of the outer circumferential surface of the leading-end-side tapered portion  32   e  is set such that an angle (acute angle) of the outer circumferential surface of the leading-end-side tapered portion  32   e  relative to the center axis of the tubular body  32   a  is not greater than 45°. Particularly, the taper angle fe of the outer circumferential surface of the leading-end-side tapered portion  32   e  is preferably not greater than 35° and more preferably not greater than 30°. For example, the taper angle fe of the outer circumferential surface of the leading-end-side tapered portion  32   e  is equal to the taper angle fc 1  of the first-stage reverse tapered portion  32   c   1  of the base-end-side reverse tapered portion  32   c . Alternatively, the taper angle fe of the outer circumferential surface of the leading-end-side tapered portion  32   e  is less than the taper angle fc 1 , fc 2  of the outer circumferential surface of the base-end-side reverse tapered portion  32   c  over the entire range. 
     A taper angle of the tapered portion Ti 3  on the inner circumferential surface of the leading-end-side tapered portion  32   e  is slightly less than the taper angle fe of the outer circumferential surface. Accordingly, the thickness of the leading-end-side tapered portion  32   e  is increased from the leading end tubular portion  32   d  toward the flange  32   b.    
     (6. Effect of Second End portion  32  According to First Example) 
     As described above, the second end portion  32  of the filler tube  30  includes the base-end-side reverse tapered portion  32   c . The base-end-side reverse tapered portion  32   c  functions as a region in which the thickness is gradually changed between the tubular body  32   a  and the flange  32   b  in the axial direction. Accordingly, the base-end-side reverse tapered portion  32   c  is formed so as to have the inner diameter that is not less than the inner diameter Dia of the tubular body  32   a  over the entire range in the axial direction. In a range from the tubular body  32   a  to the flange  32   b , the inner diameter is inhibited, near the flange  32   b , from becoming less than the reference inner diameter Dia (the inner diameter Dia of the tubular body  32   a ). Accordingly, fuel flow performance is prevented from being affected near the flange  32   b , and fuel flow performance exhibited by the filler tube  30  indicates a desired value. 
     The base-end-side reverse tapered portion  32   c  has a plurality of stages of reverse tapered portions  32   c   1 ,  32   c   2 . In a case where a plurality of stages of the reverse tapered portions  32   c   1 ,  32   c   2  are thus provided, change of an angle from the tubular body  32   a  to the first-stage reverse tapered portion  32   c   1  is reduced, and change of an angle from the first-stage reverse tapered portion  32   c   1  to the second-stage reverse tapered portion  32   c   2  is reduced. As a result, contribution to gradual change of a thickness is made. Particularly, in a case where change of an angle from the tubular body  32   a  to the first-stage reverse tapered portion  32   c   1  is reduced, the first-stage reverse tapered portion  32   c   1  is more likely to have an inner diameter that is not less than the inner diameter Dia of the tubular body  32   a.    
     Furthermore, the second end portion  32  includes the leading-end-side tapered portion  32   e . The leading-end-side tapered portion  32   e  functions as a region in which the thickness is gradually changed between the flange  32   b  and the leading end tubular portion  32   d  in the axial direction. Accordingly, the leading-end-side tapered portion  32   e  is formed so as to have an inner diameter that is not less than the inner diameter Did of the leading end tubular portion  32   d  over the entire range in the axial direction. The inner diameter is inhibited from becoming less than the inner diameter Did of the leading end tubular portion  32   d  in a range from the flange  32   b  to the leading end tubular portion  32   d . Particularly, in a case where the inner diameter Did of the leading end tubular portion  32   d  is equal to the inner diameter Dia of the tubular body  32   a , the inner diameter is inhibited, near the flange  32   b , from becoming less than the reference inner diameter Dia (the inner diameter Dia of the tubular body  32   a ). 
     (7. Second Example of Second End Portion  32  of Filler Tube  30 ) 
     Next, a second example of the second end portion  32  will be described with reference to  FIG. 4 . The second end portion  32  includes the tubular body  32   a , the flange  32   b , a base-end-side reverse tapered portion  132   c , the leading end tubular portion  32   d , and the leading-end-side tapered portion  32   e . In the second example, the tubular body  32   a , the flange  32   b , the leading end tubular portion  32   d , and the leading-end-side tapered portion  32   e  have the same structures as those of the first example, and the base-end-side reverse tapered portion  132   c  is different from the base-end-side reverse tapered portion  32   c  of the first example. Difference of the second example from the first example will be described below. 
     As shown in  FIG. 4 , the base-end-side reverse tapered portion  132   c  connects between the tubular body  32   a  and the flange  32   b . More specifically, the base-end-side reverse tapered portion  132   c  is formed so as to have one predetermined taper angle in a range from the end of the tubular body  32   a  on the fuel tank  20  side to the end of the outer circumferential surface of the flange  32   b  on the side opposite to the fuel tank  20  side. In the present embodiment, the base-end-side reverse tapered portion  132   c  is included in the axial range C. That is, in  FIG. 4 , the base-end-side reverse tapered portion  132   c  is a portion in a range between the position P 1  and the position P 3  on the inner circumferential surface. 
     The length of the axial range C of the base-end-side reverse tapered portion  132   c  is greater than the length of the axial range B of the flange  32   b . Furthermore, the base-end-side reverse tapered portion  132   c  is structured to have the plurality of layers ( 61  to  65 ) that are of the same kinds as those of the tubular body  32   a , from the inner face toward the outer face. 
     The base-end-side reverse tapered portion  132   c  is reversely tapered so as to increase the diameter toward the flange  32   b . More specifically, the outer circumferential surface of the base-end-side reverse tapered portion  132   c  is reversely tapered at one taper angle so as to increase the diameter from the tubular body  32   a  toward the flange  32   b  in the entire range (the main portion excluding connection portions on both ends) in the axial direction. However, the base-end-side reverse tapered portion  132   c  is smoothly connected at a portion connecting to the tubular body  32   a  and at a portion connecting to the flange  32   b.    
     A taper angle fc 11  of the outer circumferential surface of the base-end-side reverse tapered portion  132   c  is set such that an angle (acute angle) of the outer circumferential surface of the base-end-side reverse tapered portion  132   c  relative to the center axis of the tubular body  32   a  is not greater than 45°. Particularly, the taper angle fc 11  of the outer circumferential surface of the base-end-side reverse tapered portion  132   c  is preferably not greater than 40° and more preferably not greater than 35°. The taper angle fc 11  of the outer circumferential surface of the base-end-side reverse tapered portion  132   c  is preferably not less than 20° and particularly preferably not less than 25°. 
     A taper angle of a reverse tapered portion Ti 11  of the inner circumferential surface of the base-end-side reverse tapered portion  132   c  is slightly less than the taper angle fc 11  of the outer circumferential surface. Accordingly, the thickness of the base-end-side reverse tapered portion  132   c  is increased from the tubular body  32   a  toward the flange  32   b . The taper angle fe of the outer circumferential surface of the leading-end-side tapered portion  32   e  is less than the taper angle fc 11  of the outer circumferential surface of the base-end-side reverse tapered portion  132   c  over the entire range. 
     The base-end-side reverse tapered portion  132   c  is formed so as to have an inner diameter that is not less than the inner diameter Dia of the tubular body  32   a  over the entire range in the axial direction. The inner circumferential surface of the base-end-side reverse tapered portion  132   c  has the reverse tapered portion Ti 11  so as to increase the diameter from the tubular body  32   a  toward the flange  32   b . Accordingly, a diameter increase start position Ps 1  of the reverse tapered portion Ti 11  on the inner circumferential surface is included in a range of the base-end-side reverse tapered portion  132   c  in the axial direction, and is closer to the tubular body  32   a  than the flange  32   b . That is, a portion of the base-end-side reverse tapered portion  132   c  from the position P 1  to the diameter increase start position Ps 1  is formed so as to have the inner diameter equal to the inner diameter Dia of the tubular body  32   a.    
     (8. Effect of Second End Portion  32  According to Second Example) 
     As described above, the second end portion  32  of the filler tube  30  includes the base-end-side reverse tapered portion  132   c . The base-end-side reverse tapered portion  132   c  functions as a region in which the thickness is gradually changed between the tubular body  32   a  and the flange  32   b  in the axial direction. Accordingly, the base-end-side reverse tapered portion  132   c  is formed so as to have the inner diameter that is not less than the inner diameter Dia of the tubular body  32   a  over the entire range in the axial direction. The inner diameter is inhibited, near the flange  32   b , from becoming less than the reference inner diameter Dia (the inner diameter Dia of the tubular body  32   a ) in a range from the tubular body  32   a  to the flange  32   b . Accordingly, fuel flow performance is prevented from being affected near the flange  32   b , and fuel flow performance exhibited by the filler tube  30  indicates a desired value. 
     (9. Method for Manufacturing Tank Unit ( 20 ,  30 ,  40 )) 
     Next, a method for manufacturing the tank unit ( 20 ,  30 ,  40 ) that includes the fuel tank  20 , the filler tube  30 , and the check valve  40  will be described with reference to  FIG. 5 . 
     Firstly, the filler tube  30  is manufactured (S 1 : □filler tube manufacturing step□). The filler tube  30  is formed by extrusion molding. Accordingly, in the filler tube manufacturing step S 1 , a primary material  30   a  (shown in  FIG. 6 ) is formed by extrusion molding (S 11 ), and a secondary material  30   b  (shown in  FIG. 6 ) is formed by corrugation forming (S 12 ), and the secondary material  30   b  is finally cut, thereby forming the filler tube  30  (S 13 ). The method for manufacturing the filler tube  30  will be described below in more detail. 
     The fuel tank  20  is prepared (manufactured) (S 2 : □fuel tank preparing step□). The check valve  40  is prepared (S 3 : □check valve preparing step□). Subsequently, the check valve  40  is attached to the second end portion  32  of the filler tube  30  (S 4 : □check valve attaching step□). Subsequently, the second end portion  32  of the filler tube  30  is disposed at the position (welding initial position) of the opening hole  21  of the fuel tank  20  (S 5 : □initial position disposition step□). Subsequently, the flange  32   b  of the second end portion  32  of the filler tube  30  and the outer circumferential edge of the opening hole  21  of the fuel tank  20  are welded to each other (S 6 : □welding step□). In a case where the check valve  40  can be attached after the welding, step S 4  may be performed after step S 6 . 
     (10. Structure of Manufacturing Apparatus  100  for Filler Tube  30 ) 
     Next, the structure of a manufacturing apparatus  100  for manufacturing the filler tube  30  will be described with reference to  FIG. 6  and  FIG. 7 . The filler tube  30  is manufactured by the manufacturing apparatus  100  shown in  FIG. 6 . The manufacturing apparatus  100  includes an extruder  110 , a corrugation molding machine  120  arranged continuously with the extruder  110 , and a cutting machine  130  arranged continuously with the corrugation molding machine  120 . 
     That is, the tubular primary material  30   a  (tubular material) is formed by the extruder  110  (S 11  in  FIG. 5 ), the tubular secondary material  30   b  is formed by the corrugation molding machine  120  (S 12  in  FIG. 5 ), and the filler tube  30  is formed by the cutting machine  130  (S 13  in  FIG. 5 ). 
     The extruder  110  performs extrusion molding to form the tubular primary material  30   a . The primary material  30   a  is structured to have a plurality of layers ( 61  to  65 ) as shown in  FIG. 3  and  FIG. 4 , and is formed in a cylindrical shape having a constant inner diameter and a constant outer diameter in the axial direction. That is, the primary material  30   a  is formed so as to have a constant thickness in the radial direction as a whole, and each layer is also formed so as to have a constant thickness in the radial direction. An extruding speed of the extruder  110  is adjustable to any speed. 
     While sequentially moving each of a plurality of split molds  123 ,  124  in the direction in which the primary material  30   a  is extruded, the corrugation molding machine  120  brings the primary material  30   a  into close contact with an inner face formed by the plurality of split molds  123 ,  124  to form the secondary material  30   b  that corresponds to the filler tube  30  having an outer face corresponding to the inner face. 
     The corrugation molding machine  120  is used for a portion at which the shape of the primary material  30   a  formed through extrusion molding by the extruder  110  is changed. In the present embodiment, the corrugation molding machine  120  is mainly used for forming the bellows portion  33   b  and forming the second end portion  32 . The corrugation molding machine  120  is used for changing the outer diameter of the primary material  30   a  also in a portion having a cylindrical shape. 
     The corrugation molding machine  120  includes a guide table  121 , a suctioning device  122 , a plurality of the split molds  123 ,  124 , and a drive gear  125 . An ellipsoidal first guide groove  121   a  and a second guide groove  121   b  which has the same shape as the first guide groove  121   a  and which is disposed adjacent to the first guide groove  121   a  are formed in the upper face of the guide table  121 . Furthermore, communication holes  121   c  that communicate with the first guide groove  121   a  and the second guide groove  121   b  are formed in the guide table  121 , as shown in  FIG. 7 . As shown in  FIG. 7 , the suctioning device  122  is connected to the communication holes  121   c  in the guide table  121 , and suctions air in a space communicating with the communication holes  121   c.    
     A plurality of first split molds  123  are molds for shaping one of two portions into which the filler tube  30  is divided along the axial direction. The plurality of first split molds  123  are sequentially moved on and along the first guide groove  121   a  of the guide table  121 . That is, each of the plurality of first split molds  123  is sequentially moved to form a half part of the filler tube  30 . Each of the plurality of first split molds  123  has a rack gear on the upper face. 
     A plurality of second split molds  124  are molds for shaping the other of the two portions into which the filler tube  30  is divided along the axial direction. The plurality of second split molds  124  are sequentially moved on and along the second guide groove  121   b  of the guide table  121 . That is, each of the plurality of second split molds  124  is sequentially moved to form a remaining half part of the filler tube  30 . Each of the plurality of second split molds  124  has a rack gear on the upper face. 
     A portion of the first split molds  123  and a portion of the second split molds  124  each have a shaping surface corresponding to the bellows portion  33   b . Another portion of the first split molds  123  and another portion of the second split molds  124  each have a shaping surface corresponding to the second end portion  32 . 
     A discharge opening of a nozzle  111  of the extruder  110  is disposed at a position, on the extruder  110  side, of a pair of molds formed by combining the plurality of first split molds  123  and the plurality of second split molds  124  with each other. That is, the primary material  30   a  is suctioned onto the inner circumferential surfaces of the pair of molds  123 ,  124  located at the position and thus shaped. 
     The drive gear  125  is a pinion gear for moving the plurality of first split molds  123  and the plurality of second split molds  124 . The drive gear  125  is disposed on the extruder  110  side of the pair of molds formed by combining the plurality of first split molds  123  and the plurality of second split molds  124  with each other. The drive gear  125  meshes with the first split molds  123  and the second split molds  124 , and is driven to rotate, whereby the plurality of first split molds  123  and the plurality of second split molds  124  are sequentially moved. 
     Furthermore, moving speeds of the plurality of split molds  123 ,  124  are changed by changing a rotation speed of the drive gear  125 . Increase of the moving speeds of the plurality of split molds  123 ,  124  causes the filler tube  30  to have a thickness reduced in the radial direction at portions corresponding to the split molds  123 ,  124  located near the nozzle  111  of the extruder  110 . Meanwhile, reduction of the moving speeds of the plurality of split molds  123 ,  124  causes the filler tube  30  to have a thickness increased in the radial direction at portions corresponding to the split molds  123 ,  124  located near the nozzle  111  of the extruder  110 . 
     Specifically, in a case where the moving speeds of the split molds  123 ,  124  are set as a first speed, the tubular body  32   a  has a predetermined thickness. In a case where the moving speeds of the split molds  123 ,  124  are set as a second speed that is lower than the first speed, the thickness of the flange  32   b  becomes greater than the thickness of the tubular body  32   a . Furthermore, in a case where the moving speeds of the split molds  123 ,  124  are gradually reduced from the first speed to the second speed, the thickness of the base-end-side reverse tapered portion  32   c ,  132   c  is gradually increased. 
     In a case where the moving speeds of the split molds  123 ,  124  are set as a third speed that is higher than the second speed, the thickness of the leading end tubular portion  32   d  becomes less than the thickness of the flange  32   b . Furthermore, in a case where the moving speeds of the split molds  123 ,  124  are gradually increased from the second speed to the third speed, the thickness of the leading-end-side tapered portion  32   e  is gradually reduced. 
     The secondary material  30   b  discharged from the corrugation molding machine  120  has a shape continuous in the axial direction. That is, the continuous secondary material  30   b  has such a shape that a plurality of the filler tubes  30  connect to each other. Therefore, the continuous secondary material  30   b  shaped by the corrugation molding machine  120  is cut, by the cutting machine  130 , so as to have a predetermined length, thereby forming each filler tube  30 . 
     The filler tube  30  described above is manufactured by the manufacturing method. Particularly, the primary material  30   a  formed by extrusion molding is shaped by the split molds  123 ,  124 , thereby forming the secondary material  30   b.    
     In the manufacturing method, the thickness of the filler tube  30  is not abruptly changed but is gradually changed. Therefore, the thickness is gradually increased from the tubular body  32   a  toward the flange  32   b . The base-end-side reverse tapered portion  32   c ,  132   c  is located at the gradually changed portion. Accordingly, in a case where the base-end-side reverse tapered portion  32   c ,  132   c  is provided, the thickness is gradually increased, and the thickness is also prevented from being increased in the radially inward direction between the tubular body  32   a  and the flange  32   b . Accordingly, the inner diameter of the base-end-side reverse tapered portion  32   c ,  132   c  is not less than the inner diameter Dia of the tubular body  32   a.    
     The thickness is gradually reduced from the flange  32   b  toward the leading end tubular portion  32   d . The leading-end-side tapered portion  32   e  is located at the gradually changed portion. Accordingly, in a case where the leading-end-side tapered portion  32   e  is provided, the thickness is gradually reduced, and the thickness is also prevented from being increased in the radially inward direction between the flange  32   b  and the leading end tubular portion  32   d . Accordingly, the inner diameter of the leading-end-side tapered portion  32   e  is not less than the inner diameter Did of the leading end tubular portion  32   d.