Abstract:
A structure for a fuel filling opening of an automobile is configure such that, when fuel supplied from a fuel supply nozzle flows back to the fuel filling opening side, the fuel flowed back can be slowly discharged to the outside from the fuel filling opening. The structure is provided with ring recesses formed in a ring opening of an operation ring, and also with partitioning recesses formed in an opening in an outer tube partition. The recesses are arranged offset in the circumferential direction to form a labyrinth.

Description:
TECHNICAL FIELD 
     The present invention relates generally to an automobile fuel filler opening structure and, more particularly, to an automobile fuel filler opening structure wherein a shutter for opening/closing a filler pipe is provided and held in an open state by being pushed in by a fuel filler nozzle. 
     BACKGROUND ART 
     Among fuel filler opening structures of automobiles, there are those in which a shutter is provided in an openable and closeable manner in the vicinity of a fuel filler opening through which a fuel filler nozzle can be inserted, and an annular operating ring is provided above the shutter. With this fuel filler opening structure for an automobile, when the fuel filler nozzle has been inserted through the fuel filler opening, the operating ring is enlarged in diameter by the inserted nozzle, and a lock on the shutter is released in conjunction with the enlarging of the operating ring. 
     With the lock on the shutter released, the fuel filler nozzle is inserted toward the shutter, whereby the shutter is pushed down and opened by the nozzle. There is a known technique whereby the fuel filler nozzle is inserted up to a fuel filling position while the shutter is in an opened state and fuel is supplied from the inserted nozzle to a fuel tank, as is disclosed in Patent Document 1, for example. 
     However, with the fuel filler opening structure of Patent Document 1, fuel could mistakenly be supplied from the fuel filler nozzle in a state in which the shutter has not been opened by the fuel filler nozzle. In this case, there is a danger that fuel supplied from the fuel filler nozzle will flow (backward) to the fuel filler opening, and the back-flowing fuel will strongly discharge to the outside from the fuel filler opening and come in contact with the user. 
     The fuel filler nozzle is commonly provided with a liquid level detection sensor in the distal end in the nozzle. When the liquid level of the fuel has risen to the liquid level detection sensor while the fuel is being supplied by the fuel filler nozzle, the liquid level of the fuel is detected by the liquid level detection sensor. When the liquid level of the fuel is detected by the liquid level detection sensor, the supply of fuel is stopped based on a detection signal of the sensor. 
     However, if the detection sensor fails, it becomes impossible for the liquid level of the fuel to be detected by the detection sensor and for the supply of fuel to be stopped. Therefore, the fuel supplied from the fuel filler nozzle flows back toward the fuel filler opening, the back-flowing fuel strongly discharges to the outside from the fuel filler opening, and the discharged fuel comes in contact with the user. 
     PRIOR ART LITERATURE 
     Patent Document 
     
         
         Patent Document 1: JP 2007-518619 A 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     An object of the present invention is to provide a fuel filler opening structure for an automobile whereby back-flowing fuel is slowly discharged to the outside through a fuel filler opening, and the discharged fuel is prevented from coming in contact with the user when fuel supplied from a fuel filler nozzle flows back to the fuel filler opening. 
     Solution to Problem 
     According to one aspect of the present invention, there is provided an automobile fuel filler opening structure comprising: a filler pipe having a fuel filler opening that allows insertion of a fuel filler nozzle therethrough; and a shutter for opening/closing the filler pipe, the shutter being adapted to be held in an opened state by pushing in the fuel filler nozzle so as to allow insertion of the fuel filler nozzle up to a fuel filling position, wherein the structure further comprises first and second partitioning parts provided at a predetermined interval between the shutter and the fuel filler opening for allowing passage of the fuel filler nozzle therethrough, the first partitioning part having a first opening for allowing passage of the fuel filler nozzle, the second partitioning part having a second opening for allowing passage of the fuel filler nozzle, the first opening having at least one first hollow part of a predetermined circumferential width, the second opening having at least one second hollow part of a predetermined circumferential width, the first and second hollow parts being provided in a circumferentially offset relation to each other to thereby form a labyrinth between the shutter and the fuel filler opening. 
     Preferably, the first partitioning part comprises an operating ring whereby the locking of the shutter is released by the first opening enlarging when the fuel filler nozzle is inserted into the first opening. 
     According to another aspect of the present invention, there is provided an automobile fuel filler opening structure comprising: a filler pipe having a fuel filler opening that allows insertion of a fuel filler nozzle therethrough; and a shutter for opening/closing the filler pipe, the shutter being adapted to be held in an opened state by pushing in the fuel filler nozzle so as to allow insertion of the fuel filler nozzle up to a fuel filling position, wherein the structure further comprises a partitioning part provided between the shutter and the fuel filler opening for allowing passage of the fuel filler nozzle, the partitioning part has an opening for allowing passage of the fuel filler nozzle, and the opening has chamfered parts in corners thereof so that a rate of fuel flowing from the shutter to the fuel filler opening via gaps between the opening and the fuel filler nozzle is minimized. 
     Preferably, the chamfered parts are formed in an internal peripheral edge of the opening. 
     In a preferred form, the chamfered parts comprise inclined surfaces. 
     The chamfered parts may be convex curved surfaces. 
     Advantageous Effects of Invention 
     In one aspect, the inventive arrangement has first and second partitioning parts through which a fuel filler nozzle can be inserted, and these first and second partitioning parts are provided at a predetermined interval from each other between the shutter and the fuel filler opening. Furthermore, a first opening is formed in the first partitioning part, and at least one first hollow part having a predetermined width in the circumferential direction is formed in the first opening. Furthermore, a second opening is formed in the second partitioning part, and at least one second hollow part having a predetermined width in the circumferential direction is formed in the second opening. The first and second hollow parts are disposed at an offset in the circumferential direction, forming a labyrinth between the shutter and the fuel filler opening. Accordingly, in cases in which fuel supplied from the fuel filler nozzle flows (backward) from the shutter to the fuel filler opening, the flow rate of the back-flowing fuel can be minimized by the labyrinth. The back-flowing fuel can thereby be slowly discharged to the outside from the fuel filler opening, and the discharged fuel can be prevented from coming in contact with the user. 
     The first partitioning part is configured from an operating ring. The operating ring is an existing member for releasing the locking of the shutter when the fuel filler nozzle is inserted into the first opening. Thus, by using an existing operating ring as the first partitioning part, the configuration can be simplified because there is no need to provide a new member as the first partitioning part. 
     In the inventive arrangement in another aspect, a partitioning part is provided through which the fuel filler nozzle can be inserted, and chamfered parts are formed in corners of the opening in this partitioning part. Accordingly, it is possible to minimize the flow rate of fuel flowing (backward) from the shutter to the fuel filler opening via the gaps between the opening of the partitioning part and the fuel filler nozzle. Back-flowing fuel can thereby be more slowly discharged to the outside from the fuel filler opening, and the discharged fuel can be prevented from coming in contact with the user. 
     The chamfered parts are formed in the internal peripheral edge of the opening and are comprised of inclined surfaces or convex curved surfaces. Therefore, it is possible to minimize the flow rate of fuel flowing between the internal peripheral edge and the fuel filler nozzle. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       A preferred embodiment of the present invention will be described in detail below, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of an automobile provided with the fuel filler opening structure for an automobile according to the present invention; 
         FIG. 2  is an enlarged cross-sectional view taken along line  2 - 2  of  FIG. 1 ; 
         FIG. 3  is a perspective view of the fuel filler opening structure of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view showing the outside cylinder partitioning opening of the outside cylinder partitioning wall of  FIG. 2 ; 
         FIG. 5  is a perspective view in which a labyrinth is formed by the outside cylinder partitioning opening of the outside cylinder partitioning wall and the ring opening of the operating ring of  FIG. 3 ; 
         FIG. 6  is a view showing a state in which the fuel filler nozzle has been inserted partway into the fuel filler opening structure shown in  FIG. 2 ; 
         FIG. 7  is a view showing a state in which the fuel filler nozzle has been inserted up to the fuel filling position in the fuel filler opening structure of  FIG. 2 ; 
         FIGS. 8A-8B  are views showing a manner in which fuel flows when the fuel filler nozzle has been inserted up to the second shutter of the fuel filler opening structure; wherein  FIG. 8A  is a view showing the fuel filler nozzle of a fuel filler gun inserted through the fuel filler opening, and  FIG. 8B  is a view showing the fuel supplied from a distal end of the fuel filler nozzle coming in contact with a pipe shutter; 
         FIGS. 9A-9B  are views showing a state in which fuel slowly overflows from the fuel opening, wherein  FIG. 9A  is a view of fuel overflow from the fuel opening in which the fuel filler nozzle is omitted, and  FIG. 9B  is a view showing inclined surfaces formed in an internal peripheral edge of the outside cylinder partitioning opening; 
         FIGS. 10A-10B  are views showing a state in which the fuel filler nozzle has been inserted up to the fuel filling position of the fuel filler opening structure, wherein  FIG. 10A  is a view showing the fuel filler nozzle of the fuel filler gun being inserted through the fuel filler opening, and  FIG. 10B  is a view showing an outside cylinder partitioning opening having spaces formed between an internal peripheral edge and the fuel filler nozzle; 
         FIGS. 11A-11B  are views showing a state in which fuel slowly overflows from the fuel filler opening of the fuel filler opening structure, wherein  FIG. 11A  is a view showing an outside cylinder partitioning opening having a plurality of partitioning concavities formed in internal peripheral parts thereof, and  FIG. 11B  is a view showing inclined surfaces formed in the internal peripheral edge of the outside cylinder partitioning opening; 
         FIG. 12  is a view showing a modification of the chamfered parts in  FIG. 5 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In an automobile  10  shown in  FIG. 1 , a fuel tank  12  is provided underneath the floor of a vehicle frame  11 , a pipe proximal end  14   a  of a filler pipe  14  is provided to the left rear part  12   a  of the fuel tank  12 , a fuel filler opening structure  20  for an automobile is provided to a pipe head  14   b  of the filler pipe  14 , and a fuel lid  16  for covering the fuel filler opening structure  20  for an automobile is attached to the vehicle frame  11  in an openable and closeable manner. 
     The fuel filler opening structure  20  for an automobile is configured so that a fuel filler nozzle  23  ( FIG. 7 ) of a fuel filler gun  22  provided at a fuelling station can be inserted, and the inserted fuel filler nozzle  23  can be guided into the filler pipe  14 . The fuel filler opening structure  20  for an automobile is described hereinbelow. 
     The fuel filler opening structure  20  for an automobile has an inside cylinder  25  provided in the pipe head  14   b  of the filler pipe  14 , an outside cylinder  27  provided to the inside cylinder  25 , an operating ring (first partitioning part)  28  and a nozzle guide  29  provided in the outside cylinder  27 , and a fuel filler opening ring  31  provided to an outside cylinder head  27   a  of the outside cylinder  27 , as shown in  FIGS. 2 and 3 . 
     A fuel filler opening  73  of the fuel filler opening ring  31  is provided with a fuel filler opening shutter (not shown) which serves as a first shutter. A pipe shutter (a shutter)  26  which serves as a second shutter is provided in the inside cylinder  25 . 
     The fuel filler opening structure  20  for an automobile has a so-called capless type of fuel filler opening structure in which the inclusion of the fuel filler opening shutter and the pipe shutter  26  allows the fuel filler opening cap to be removed from the fuel filler opening  73 . 
     In the filler pipe  14 , the pipe proximal end  14   a  is provided to the left rear part  12   a  of the fuel tank  12  as shown in  FIG. 1 , and a pipe flange  33  ( FIG. 3 ) is formed in the pipe head  14   b . The inside cylinder  25  is inserted into the opening of the pipe head  14   b.    
     The inside cylinder  25  has a cylindrical inside cylinder wall  35  coaxially inserted into the opening of the pipe head  14   b , and an inside cylinder partitioning wall  36  and an inside cylinder flange  37  formed at the end  35   a  of the inside cylinder wall  35 . 
     The inside cylinder wall  35  of the inside cylinder  25  is inserted into the opening of the pipe head  14   b , and the inside cylinder flange  37  is brought into contact with the pipe flange  33 . An inside cylinder partitioning opening  38  through which the fuel filler nozzle  23  shown in  FIG. 7  can be inserted is formed in the inside cylinder partitioning wall  36 . The pipe shutter  26  is provided to an inside cylinder internal space  41  of the inside cylinder  25 . 
     The pipe shutter  26  is provided in an openable and closeable manner across a predetermined gap L 1  ( FIG. 2 ) toward the filler pipe  14  away from the fuel filler opening  73 , described hereinafter. This pipe shutter  26  is supported to be capable of swinging about a support pin  43  between a closed position P 1  and an open position P 2  ( FIG. 7 ), and an annular seal member  44  is provided to an external periphery  26   a . The support pin  43  is provided to a support member  45 . The support member  45  is provided to the inside cylinder wall  35  in a state of being disposed in the inside cylinder internal space  41  of the inside cylinder  25 . 
     The pipe shutter  26  is held in the closed position P 1  by the urging force of a return coil spring  46 , and is locked in the closed position P 1  by a lock mechanism (not shown). The coil spring  46  is provided to the support pin  43 . The lock mechanism is configured so that the lock is released when the operating ring  28  enlarges in diameter. 
     The pipe shutter  26  is held in the closed position P 1  by the urging force of the coil spring  46 . The pipe shutter  26  is locked in this state by the lock mechanism. The annular seal member  44  comes in contact with the peripheral edge of the inside cylinder partitioning opening  38  due to the pipe shutter  26  being held in the closed position P 1 . The inside cylinder partitioning opening  38  is thereby closed off by the pipe shutter  26 . 
     While the lock of the lock mechanism is in a released state, the pipe shutter  26  is capable of swinging to the open position P 2  against the urging force of the coil spring  46 . The inside cylinder partitioning opening  38  is opened by the swinging of the pipe shutter  26  to the open position P 2 . 
     The outside cylinder  27  has a cylindrical outside cylinder wall  51  provided along the same axis as the inside cylinder  25 , and an outside cylinder partitioning wall (second partitioning part)  52  formed in the outside cylinder wall  51 . 
     The outside cylinder wall  51  has a fitting peripheral wall  54  enlarged in diameter to be capable of fitting into the inside cylinder flange  37  of the inside cylinder  25  and the pipe flange  33 , and an accommodating peripheral wall  55  formed integrally in the fitting peripheral wall  54  and capable of accommodating the operating ring  28 . The outside cylinder  27  is provided along the same axis as the inside cylinder  25  in a state in which the inside cylinder flange  37  and the pipe flange  33  are fitted into the fitting peripheral wall  54 . 
     The outside cylinder partitioning wall  52  is provided between the pipe shutter  26  and the fuel filler opening  73 , i.e., between the pipe shutter  26  and the operating ring  28 . The outside cylinder partitioning wall  52  is a partitioning wall for partitioning a fitting internal space  57  in the fitting peripheral wall  54  and an accommodating internal space  58  in the accommodating peripheral wall  55 , and an outside cylinder partitioning opening (a second opening, an opening)  61  is formed along the same axis as the outside cylinder wall  51 . The outside cylinder partitioning opening  61  of the outside cylinder partitioning wall  52  is described in detail in  FIGS. 4 and 5 . 
     The operating ring  28  is provided between the outside cylinder partitioning wall  52  and the fuel filler opening  73 , i.e., between the outside cylinder partitioning wall  52  and the fuel filler opening  73 . Specifically, the operating ring  28  is provided in the accommodating internal space  58  along the same axis as the outside cylinder partitioning opening  61 , and is also provided at a predetermined gap L 2  from the outside cylinder partitioning wall  52  in the direction in which the fuel filler nozzle  23  is inserted and removed. 
     The operating ring  28  has an annular ring main body  63  provided along the same axis as the outside cylinder partitioning opening  61 , and a plurality of insertion guides  64  provided at constant intervals in the circumferential direction of the ring main body  63 . Each of the insertion guides  64  is a member formed from an elastic and deformable resinous material, and each has a guide piece  64   a  provided in a shape curving toward the internal peripheral wall of the ring main body  63 . 
     By providing the insertion guides  64  to the ring main body  63  at constant intervals, a ring opening (first opening)  65  is formed by the guide pieces  64   a . The ring opening  65  is formed with a hole diameter D 2  smaller than the outside diameter D 1  ( FIG. 7 ) of the fuel filler nozzle  23 , allowing the fuel filler nozzle  23  to be inserted (made insertable). 
     The fuel filler nozzle  23  (see  FIG. 7 ) is inserted into the ring opening  65  of the operating ring  28 , whereby the guide pieces  64   a  are elastically deformed outward in the radial direction by the fuel filler nozzle  23 . Accordingly, the hole diameter D 2  of the ring opening  65  is enlarged to the same dimension as the outside diameter D 1  of the fuel filler nozzle  23 . 
     The locked state of the lock mechanism (not shown) of the pipe shutter  26  is released by the elastic deformation of the guide pieces  64   a  in the direction in which the diameter is increased. The ring opening  65  of the operating ring  28  is described in detail in  FIGS. 4 and 5 . 
     In the accommodating internal space  58  of the accommodating peripheral wall  55 , the nozzle guide  29  is provided adjacent to, and along the same axis as, the operating ring  28 . The nozzle guide  29  is formed into a substantially cylindrical shape, and is a member whereby a peripheral wall  71  (particularly a top wall  71   a ) guides the fuel filler nozzle  23  ( FIG. 7 ) into the ring opening  65  of the operating ring  28 . The fuel filler nozzle  23  can be easily inserted into the ring opening  65  by the fuel filler nozzle  23  being guided into the ring opening  65  by the nozzle guide  29 . 
     The fuel filler opening ring  31  is a member having a fuel filler opening  73  into which the fuel filler nozzle  23  can be inserted, and is provided to the outside cylinder head  27   a  of the outside cylinder  27 . The fuel filler opening  73  is the opening into which the fuel filler nozzle  23  shown in  FIG. 7  is inserted. 
     The fuel filler opening shutter (not shown) is provided in an openable and closeable manner to the fuel filler opening ring  31 . The fuel filler opening shutter is configured so as to be pushed open by a distal end  23   a  ( FIG. 7 ) of the fuel filler nozzle  23  inserted through the fuel filler opening  73 , and to be held in the closed position by the spring force of a return spring (not shown) when the fuel filler nozzle  23  has been removed from the fuel filler opening  73 . 
     The outside cylinder partitioning opening  61  is formed having a hole diameter D 3  slightly larger than the outside diameter D 1  of the fuel filler nozzle  23 , as shown in  FIGS. 4 and 5 . Specifically, the outside cylinder partitioning opening  61  is formed to allow the fuel filler nozzle  23  to be inserted through (to be insertable). Furthermore, the outside cylinder partitioning opening  61  is formed so that the space between an internal peripheral edge  61   a  of the outside cylinder partitioning opening  61  and the fuel filler nozzle  23  (the space between the opening and the fuel filler nozzle) is S 1 . 
     The outside cylinder partitioning opening  61  has inclined surfaces (chamfered parts)  75  formed in each pair of corners of the internal peripheral edge  61   a . Accordingly, the spaces S 2  between the inclined surfaces  75  and the fuel filler nozzle  23  are formed larger than the spaces S 1  between the internal peripheral edge  61   a  and the fuel filler nozzle  23 . The flow rate of fuel flowing between the internal peripheral edge  61   a  and the fuel filler nozzle  23  can thereby be minimized. By forming the spaces S 2  larger than the spaces S 1 , the fuel filler nozzle  23  can be smoothly guided during insertion. 
     Furthermore, in the outside cylinder partitioning opening  61 , a plurality of partitioning concavities (second hollow parts)  76  having predetermined widths are formed at predetermined intervals in the circumferential direction of internal peripheral parts  61   b . The reasons for forming the partitioning concavities  76  in the outside cylinder partitioning opening  61  are described hereinafter. 
     The operating ring  28  is provided with a plurality of insertion guides  64  at constant intervals in the circumferential direction of the ring main body  63 , as shown in  FIG. 5 , whereby a plurality of ring concavities (first hollow parts)  68  is formed by the guide pieces  64   a  and the ring main body  63 . In other words, in the ring opening  65 , a plurality of ring concavities  68  having predetermined widths is formed at predetermined intervals in the circumferential direction. 
     The ring concavities  68  are disposed at an offset (in different positions) in the circumferential direction from the partitioning concavities  76  of the outside cylinder partitioning opening  61 . By disposing the ring concavities  68  at an offset (in different positions) in the circumferential direction from the partitioning concavities  76 , a labyrinth  81  is formed by the ring concavities  68  and the partitioning concavities  76 . The flow rate of fuel flowing from the pipe shutter  26  shown in  FIG. 2  toward the fuel filler opening  73  can thereby be minimized by the labyrinth  81  formed by the ring concavities  68  and the partitioning concavities  76 . The width dimensions of the ring concavities  68  and the width dimensions of the partitioning concavities  76  do not need to be equal to each other and can be set arbitrarily. 
     The operating ring  28  is an existing member used in common fuel filler opening structures. Thus, by using an existing operating ring  28  and forming the labyrinth  81 , there is no need to provide new members. It is thereby possible to form a labyrinth  81  for minimizing the fuel flow rate with a simple configuration, and the configuration can be simplified. 
     Next, an example in which fuel  83  is supplied from the fuel filler opening structure  20  for an automobile will be described based on  FIGS. 6 and 7 . 
     The fuel filler nozzle  23  of the fuel filler gun  22  is inserted as shown by arrow A through the fuel filler opening  73 , as shown in  FIG. 6 . The distal end  23   a  of the fuel filler nozzle  23  is inserted into the ring opening  65  of the operating ring  28  via the fuel filler opening  73  and the nozzle guide  29 . 
     By insertion of the distal end  23   a  of the fuel filler nozzle  23  into the ring opening  65 , each of the guide pieces  64   a  of the insertion guides  64  is elastically deformed by the fuel filler nozzle  23  in an outward radial direction. Accordingly, the hole diameter D 2  ( FIG. 2 ) of the ring opening  65  is enlarged to the same dimension as the outside diameter D 1  of the fuel filler nozzle  23 . 
     The lock of the lock mechanism (not shown) of the pipe shutter  26  is released by the elastic deformation of the guide pieces  64   a  in the direction in which the diameter is increased. In this state, the fuel filler nozzle  23  continues to be inserted as shown by arrow A, whereby the distal end  23   a  of the fuel filler nozzle  23  comes in contact with the pipe shutter  26  via the outside cylinder partitioning opening  61 . 
     The pipe shutter  26  is pushed in by the distal end  23   a  of the fuel filler nozzle  23 . The pipe shutter  26  is swung from the closed position P 1  to the open position P 2 , as shown by arrow B, against the urging force of the coil spring  46 . 
     The pipe shutter  26  is opened to the open position P 2  by the pipe shutter  26  being pushed in by the fuel filler nozzle  23 , as shown in  FIG. 7 . Accordingly, the fuel filler nozzle  23  can be inserted into a fuel filling position P 3  as shown by arrow A. With the fuel filler nozzle  23  having been inserted into the fuel filling position P 3 , the fuel filler gun  22  is operated and fuel  83  is supplied from the distal end  23   a  of the fuel filler nozzle  23  to the filler pipe  14 . 
     Fuel  83  is supplied to the fuel tank  12 , and the fuel  83  rises to a FULL position (full tank position) P 4  of the filler pipe  14 . The liquid level  83   a  of the fuel  83  reaches a fuel detection sensor  85  provided to the distal end  23   a  of the fuel filler nozzle  23 . The fuel detection sensor  85  detects the fuel  83 , and the supply of fuel  83  is stopped based on a detection signal of the fuel detection sensor  85 . 
     Next, an example is described with reference to  FIGS. 8A-8B  and  9 A- 9 B in which fuel  83  is supplied without inserting the fuel filler nozzle  23  of the fuel filler gun  22  up to the fuel filling position P 3 . 
     In  FIG. 8A , the fuel filler nozzle  23  of the fuel filler gun  22  is inserted through the fuel filler opening  73  as shown by arrow A. The distal end  23   a  of the fuel filler nozzle  23  reaches the pipe shutter  26  via the outside cylinder partitioning opening  61 . In this state, the user mistakenly attempts to supply fuel  83  from the fuel filler nozzle  23  of the fuel filler gun  22  to the filler pipe  14 . 
     In  FIG. 8B , the fuel  83  supplied from the distal end  23   a  of the fuel filler nozzle  23  comes in contact with the pipe shutter  26  and flows back to the outside cylinder partitioning opening  61  as shown by arrows C. The outside cylinder partitioning opening  61  has spaces S 1  formed between the internal peripheral edge  61   a  and the fuel filler nozzle  23 . Accordingly, part of the fuel  83  in the fuel  83  flowing back as shown by arrows C flows as shown by arrows D through the spaces S 1  between the internal peripheral edge  61   a  and the fuel filler nozzle  23 . The remaining fuel  83  is described in detail in  FIG. 9A . 
     The inclined surfaces (chamfered parts)  75  are formed in the internal peripheral edge  61   a  of the outside cylinder partitioning opening  61 . Accordingly, large spaces S 2  are ensured between the inclined surfaces  75  and the fuel filler nozzle  23 . The flow rate of the back-flowing fuel  83  can be minimized when the fuel  83  flowing back as shown by arrows C flows between the internal peripheral edge  61   a  and the fuel filler nozzle  23  as shown by arrows D. 
       FIGS. 9A and 9B  show a state in which fuel slowly overflows from the fuel filler opening. The fuel filler nozzle  23  is omitted from  FIG. 9A  in order to make it easier to understand the flow rate of the fuel  83 . 
     In  FIG. 9A , the outside cylinder partitioning opening  61  has a plurality of partitioning concavities  76  formed in the internal peripheral parts  61   b . Accordingly, the remaining fuel  83  in the fuel  83  flowing back as shown by arrows C flows as shown by arrow E through the partitioning concavities  76 . 
     Some of the remaining fuel  83  is blocked from flowing through by the internal peripheral parts  61   b . Accordingly, some of the remaining fuel  83  circumvents the internal peripheral parts  61   b  and flows to the partitioning concavities  76  as shown by arrows F. The flow rate can thereby be minimized when the remaining fuel  83  flows through the partitioning concavities  76  as shown by arrows E and F. 
     A plurality of ring concavities  68  is formed in the ring opening  65  of the operating ring  28 . By disposing the ring concavities  68  at an offset (in different positions) in the circumferential direction from the plurality of partitioning concavities  76 , a labyrinth  81  is formed by the ring concavities  68  and the partitioning concavities  76 . Accordingly, the flow of fuel  83  through the partitioning concavities  76  as shown by arrows E and F is blocked by the guide pieces  64   a  of the insertion guides  64 . The fuel  83  flowing as shown by arrows E and F thereby circumvents the guide pieces  64   a  and flows into the ring concavities  68  as shown by arrows G. Therefore, the flow rate of the fuel  83  flowing as shown by arrows E and F via the ring concavities  68  can be minimized as shown by arrows G. Thus, by forming a labyrinth  81  from the ring concavities  68  and the partitioning concavities  76 , the flow rate can be minimized in the remaining fuel  83 , which is part of the fuel  83  flowing back as shown by arrows C. 
     In  FIG. 9B , inclined surfaces (chamfered parts)  75  are formed in the internal peripheral edge  61   a  of the outside cylinder partitioning opening  61 , and the labyrinth  81  ( FIG. 9A ) is formed by the ring concavities  68  and the partitioning concavities  76 , whereby the flow rate of fuel  83  flowing back against the pipe shutter  26  can be minimized. Accordingly, the back-flowing fuel  83  can be slowly discharged through the fuel filler opening  73  as shown by arrows H to the outside of the fuel filler opening structure  20  for an automobile. The discharged fuel  83  can thereby be prevented from coming in contact with the user. 
     Additionally, fuel  83  can be stored in the distal end  23   a  of the fuel filler nozzle  23  by the back-flowing fuel  83  being smoothly discharged to the outside from the fuel filler opening  73 . Accordingly, the liquid level  83   a  of the stored fuel  83  reaches the fuel detection sensor  85 . The fuel detection sensor  85  detects the fuel  83 , and the supply of fuel  83  can be stopped based on a detection signal of the fuel detection sensor  85 . 
     Next, an example in which a failure occurs in the fuel detection sensor  85  of the fuel filler gun  22  will be described based on  FIGS. 10A-10B  and  11 A- 11 B.  FIGS. 10A and 10B  show a state in which the fuel filler nozzle  23  has been inserted up to the fuel filling position. 
     In  FIG. 10A , the fuel filler nozzle  23  of the fuel filler gun  22  is inserted through the fuel filler opening  73  as shown by arrow A. The pipe shutter  26  is pushed in and opened to the open position P 2  by the fuel filler nozzle  23 , and the fuel filler nozzle  23  is inserted up to the fuel filling position P 3 . In this state, the fuel  83  is supplied from the fuel filler nozzle  23  of the fuel filler gun  22  to the filler pipe  14 . 
     The fuel  83  is supplied to the fuel tank  12  shown in  FIG. 1 , and the fuel  83  rises up to the FULL position (full tank position) P 4  of the filler pipe  14 . The liquid level  83   a  of the fuel  83  reaches the fuel detection sensor  85  of the fuel filler nozzle  23 . When such a state has occurred, a failure will possibly occur in the fuel detection sensor  85 . 
     When a failure has occurred in the fuel detection sensor  85 , the fuel  83  is supplied past the FULL position (full tank position) P 4 . At this time, the supplied fuel  83  overflows from the filler pipe  14  and flows back to the outside cylinder partitioning opening  61 . 
     In  FIG. 10B , the outside cylinder partitioning opening  61  has spaces S 1   10  formed between the internal peripheral edge  61   a  and the fuel filler nozzle  23 . Accordingly, some of the fuel  83  in the back-flowing fuel  83  flows as shown by arrows I through the spaces S 1  between the internal peripheral edge  61   a  and the fuel filler nozzle  23 . The remaining fuel  83  is described in detail in  FIG. 11A . 
     Inclined surfaces (chamfered parts)  75  are formed in the internal peripheral edge  61   a  of the outside cylinder partitioning opening  61 . Accordingly, large spaces S 2  are ensured between the inclined surfaces  75  and the fuel filler nozzle  23 . When fuel  83  flowing back from the filler pipe  14  ( FIG. 10A ) flows as shown by arrows I between the internal peripheral edge  61   a  and the fuel filler nozzle  23 , the flow rate of the back-flowing fuel  83  can thereby be minimized. 
       FIGS. 11A and 11B  show a state in which fuel slowly overflows from the fuel filler opening. The fuel filler nozzle  23  has been omitted from  FIG. 11A  in order to make the flow rate of fuel  83  easier to understand. 
     In  FIG. 11A , the outside cylinder partitioning opening  61  has a plurality of partitioning concavities  76  formed in the internal peripheral parts  61   b . Accordingly, the remaining fuel  83  in the fuel  83  that has flowed back from the filler pipe  14  ( FIG. 10A ) flows through the partitioning concavities  76  as shown by arrow J. 
     At this time, some of the remaining fuel  83  is blocked from flowing through by the internal peripheral parts  61   b . Accordingly, some of the remaining fuel  83  circumvents the internal peripheral parts  61   b  and flows into the partitioning concavities  76  as shown by arrows K. The flow rate can thereby be minimized when the remaining fuel  83  flows through the partitioning concavities  76  as shown by arrows J and K. 
     A plurality of ring concavities  68  are formed in the ring opening  65  of the operating ring  28 . By disposing the ring concavities  68  at an offset (in different positions) in the circumferential direction from the partitioning concavities  76 , a labyrinth  81  is formed by the ring concavities  68  and the partitioning concavities  76 . Accordingly, the fuel  83  flowing through the partitioning concavities  76  as shown by arrows J and K is blocked from flowing through by the guide pieces  64   a  of the insertion guides  64 . The fuel  83  flowing as shown by arrows J and K thereby circumvents the guide pieces  64   a  and flows to the ring concavities  68  as shown by arrows L. Therefore, the flow rate can be minimized when the fuel  83  flowing as shown by arrows J and K flows through the ring concavities  68  as shown by arrows L. Thus, the flow rate of the remaining fuel  83  in the fuel  83  flowing back from the filler pipe  14  can be minimized by the labyrinth  81  being formed by the ring concavities  68  and the partitioning concavities  76 . 
     In  FIG. 11B , inclined surfaces (chamfered parts)  75  are formed in the internal peripheral edge  61   a  of the outside cylinder partitioning opening  61 , and a labyrinth  81  ( FIG. 11A  is formed by the ring concavities  68  and the partitioning concavities  76 , whereby the flow rate of the fuel  83  flowing back from the filler pipe  14  can be minimized. Accordingly, the fuel  83  flowing back from the filler pipe  14  can be slowly discharged from the fuel filler opening  73  to the outside of the fuel filler opening structure  20  for an automobile, as shown by arrows M. The discharged fuel  83  can thereby be prevented from coming in contact with the user. 
       FIG. 12  shows a modification of the chamfered parts  75  shown in  FIG. 5 . In the example shown in  FIG. 5 , an example was shown of chamfered parts  75  in which the corners of the internal peripheral edge  61   a  forming the outside cylinder partitioning opening  61  were comprised of inclined surfaces, but the same action and effect as inclined surfaces can be exhibited even when the chamfered parts  75  are convex curved surfaces as shown in  FIG. 12 . 
     In the present example, an example was described in which the operating ring  28  was used as the first partitioning part, but the present invention is not limited to this option alone, and a new member can also be provided as the first partitioning part. 
     In the present example, an example was described in which a plurality of ring concavities  68  were included as the first hollow parts and a plurality of partitioning concavities  76  were included as the second hollow parts, but the present invention is not limited to this option alone, and a labyrinth can be formed by offsetting one ring concavity  68  and one partitioning concavity  76  in the circumferential direction. 
     Furthermore, in the present example, the ring concavities  68  and the partitioning concavities  76  (i.e., concavities) were used as examples of the first and second hollow parts, but the present invention is not limited to this option alone, and openings (holes) or other hollow parts can also be used. 
     Furthermore, in the present example, an example was described in which the fuel filler opening structure  20  for an automobile included a labyrinth  81 , and inclined surfaces  75  were formed in the internal peripheral edge  61   a  of the outside cylinder partitioning opening  61 , but the present invention is not limited to this option alone, and either one of the labyrinth  81  and the inclined surfaces  75  alone can be applied. 
     In the present example, an example applied to a so-called capless type of fuel filler opening structure  20  was described, but the present invention is not limited to this option alone, and can also be applied to a fuel filler opening structure having a fuel filler opening cap in the fuel filler opening. 
     Furthermore, the shapes of the filler pipe  14 , the pipe shutter  26 , the operating ring  28 , the outside cylinder partitioning wall  52 , the ring concavities  68 , the partitioning concavities  76 , and the other components shown in the present example are not limited to those described herein and can be suitably varied. 
     INDUSTRIAL APPLICABILITY 
     The present invention is preferably applied to an automobile provided with a fuel filler opening structure in which a shutter for opening and closing a filler pipe is provided, and the shutter is held in the open state by being pushed in by a fuel filler nozzle. 
     LEGEND 
       10  . . . automobile:  11  . . . vehicle frame;  14  . . . filler pipe;  20  . . . automobile fuel filler opening structure;  23  . . . fuel filler nozzle;  26  . . . pipe shutter;  28  . . . operating ring (first partitioning part);  52  . . . outside cylinder partitioning wall (second partitioning part);  61  . . . outside cylinder partitioning opening (a second opening, an opening);  65  . . . ring opening (first opening);  68  . . . ring concavities (first hollow parts);  73  . . . fuel filler opening;  75  . . . inclined surfaces (chamfered parts);  76  . . . partitioning concavities (second hollow parts);  81  . . . labyrinth;  83  . . . fuel; P 3  . . . fuel filling position; S 1  . . . space between the internal peripheral edge of the outside cylinder partitioning opening and the fuel filler nozzle (space between the opening and the fuel filler nozzle); S 2  . . . space between the inclined surfaces and the fuel filler nozzle.