Abstract:
A fuel tank includes fuel pipes which are configured to resist bubble disruption of the fuel pump, minimizing the risk of fuel running out when the tank level becomes low. The fuel tank includes a fuel tank body with a fuel feed conduit operatively attached thereto, for feeding fuel to a fuel injection system. The fuel feed conduit has a pickup inlet which opens into the fuel tank body, allowing fuel to be drawn outwardly by a fuel pump of the fuel injection system. The fuel tank also includes a fuel return conduit with a return port inside the fuel tank body, for returning unused fuel therethrough to the fuel tank body. The return port of the fuel return conduit is directed toward the pickup inlet of the fuel feed conduit. The fuel feed and return conduits may be fixed to the fuel tank body using a plate-shaped member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present invention claims priority under 35 USC 119 based on Japanese patent application No. 2003-307016, filed Aug. 29, 2003. 
   1. Field of the Invention 
   The present invention relates to fuel tanks and related hardware for vehicle use. More specifically, the present invention relates to a fuel routing apparatus for a fuel tank, and to a fuel tank which enables improved fuel management using the improved fuel routing apparatus. 
   2. Description of the Background Art 
   Many different types of fuel tanks are known for vehicles. A vehicular fuel tank is known which includes a fuel tank body, with a fuel feed pipe having an inlet opening into the fuel tank body for supplying fuel to a fuel injection system. A fuel tank of this known type also includes a fuel return pipe, operatively attached to the fuel tank body, for returning unused fuel from the fuel injection system back into the fuel tank body. The fuel return pipe includes a return port, disposed inside of the fuel tank, for releasing fuel back into the tank. 
   There is a fuel tank of this known type in which the fuel feed pipe and the fuel return pipe are disposed side by side on the bottom part of the fuel tank body, and both inlet of the fuel feed pipe and return port of the fuel return pipe are arranged extending upwardly. 
   For example, Japanese Utility Model Application Laid-open Patent No. 56-143185 and Japanese Utility Model Application Laid-open Patent No. 54-97626 each disclose a fuel tank of this type. 
   Regarding the examples cited above, in the conventional structure in which the fuel feed pipe and the fuel return conduit are disposed side by side on the bottom part of the fuel tank body, and both the pickup inlet of the fuel feed conduit and the return port of the fuel return conduit are arranged extending upwardly, the two passages are arranged side by side, but no particular consideration is given for efficient feeding of the returned fuel. 
   SUMMARY OF THE INVENTION 
   Therefore, it is an object of the present invention to provide a fuel routing apparatus and fuel tank which promotes efficient circulation of returned fuel from the return pipe to the feed pipe. 
   It is another object of the present invention to provide a fuel routing apparatus and fuel tank which helps to resist fuel pump bubble disruption. 
   It is still another object of the present invention to provide a fuel routing apparatus and fuel tank designed to minimize the likelihood of the engine running out of fuel. 
   In order to achieve the objects stated above, a first aspect of the present invention provides a fuel tank with a fuel tank body and a fuel feed pipe operatively attached to the fuel tank body, the fuel feed pipe having a pickup inlet opening into the fuel tank body. The feed pipe allows fuel to flow outwardly from the tank body to a fuel pump of a fuel injection system. 
   The fuel tank and routing apparatus according to the first aspect hereof also includes a fuel return pipe operatively attached to the tank body, for recycling unused fuel from the fuel injection system back into the fuel tank body. The fuel return pipe includes a return port, located inside the fuel tank body, for expelling the recycled fuel. The fuel tank and routing apparatus according to the present invention is characterized in that the return port of the fuel return conduit is oriented facing toward the pickup inlet of the fuel feed conduit. 
   The invention as it pertains to a second aspect hereof is characterized in that, in the invention as described above, the fuel feed conduit and the fuel return conduit are disposed in the bottom part of the fuel tank body, and the fuel return conduit, after rising from the bottom part, bends convexly upward, with the return port directed toward the pickup inlet of the feed pipe. 
   The invention as it pertains to a third aspect hereof is characterized in the fuel feed conduit and the fuel return conduit are disposed on a common plate-shaped member, and are fitted to the fuel tank body via the plate-shaped member. 
   The invention as it pertains to a fourth aspect hereof is characterized in that, in the invention as described above, the pickup inlet of the fuel feed conduit is provided with a filter thereon. 
   The invention as it pertains to a fifth aspect hereof is characterized in that, in the invention as described above, the fuel tank is adapted to be installed on a saddle-riding type four-wheeled vehicle. 
   According to the first aspect of the invention, since the return port of the fuel return conduit is oriented facing toward the pickup inlet of the fuel feed conduit, when there is only a little fuel remaining in the fuel tank body, fuel returned from the fuel injection system into the fuel tank body, via the fuel return pipe, is discharged from the return port of the fuel return pipe toward the pickup inlet of the fuel feed conduit. 
   Therefore, the fuel returned from the fuel injection system into the fuel tank body via the fuel return conduit is quickly and effectively accepted through the pickup inlet, and fed to the fuel pump via the fuel feed conduit. Accordingly, the risk of the fuel pump experiencing bubble disruption and running out of fuel, which would occur when the quantity of fuel remaining in the fuel tank body has become small, can be minimized. Moreover, as these features can be realized with a simple structure, there are advantages in weight and cost aspects. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of an all-terrain vehicle incorporating a fuel tank and fuel routing apparatus according to an illustrative embodiment of the present invention. 
       FIG. 2  is a schematic diagram of the fuel tank and a fuel injection system according to a first illustrative embodiment of the present invention. 
       FIG. 3  is a partially enlarged sectional view of a portion of the fuel tank of  FIG. 2 , according to the first illustrative embodiment of the invention. 
       FIG. 4  is a partially enlarged sectional view of a portion of a fuel tank and fuel routing apparatus according to a second illustrative embodiment of the invention; and 
       FIG. 5  is a partially enlarged sectional view of a portion of a fuel tank and fuel routing apparatus according to a third illustrative embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   It should be understood that only structures considered necessary for clarifying the present invention are described herein. Other conventional structures, and those of auxiliary components of the system, are assumed to be known and understood by those in the art. 
   A fuel tank and fuel routing apparatus according to a number of selected illustrative embodiments of the present invention will be described below, with reference to the drawings. It should be noted that the left and right and the forward and backward directions, respectively, as referred to in the following description, refer to these directions as considered from the vantage point of a driver seated in the vehicle and facing forwardly. 
     FIG. 1  shows a perspective view of a vehicle  11  incorporating a fuel tank and fuel routing apparatus according to a selected illustrative embodiment of the present invention. The vehicle  11  is a saddle-riding type of four-wheeled all-terrain vehicle (ATV) which is capable of operating off-road on irregular ground. 
   This saddle-riding type vehicle  11  has four wheels  12 , arranged at the four corners of the vehicle body. The vehicle  11  is also provided with a powertrain  15  including an engine  13  and a transmission  14  arranged in a substantially central position of the vehicle body, and a steering bar  16  for steering the front wheels. The steering bar  16  extends in the left-and-right direction at the upper front part of the vehicle body, as shown. 
   The vehicle  11  also includes a head lamp unit  17  supported by the steering bar  16 , and a body cover  20 , constituting the outer shell of the vehicle body. In addition, this saddle-riding type vehicle  11  may have a so-called longitudinal crankshaft (not shown), extending in the back-and-forth direction, for the engine  13 . 
   The body cover  20  includes a front cover  22  shielding the front part of the vehicle body including the front wheels  12 , left and right sub-fenders  23  disposed behind the front cover  22  and shielding the rear part of the front wheels  12 , and a center cover  24  disposed behind the front cover  22  and shielding the upper part of the vehicle body. 
   The body cover  20  also includes a rear cover  25  disposed behind the center cover  24  and shielding the rear part of the vehicle body, left and right mud guards  26  disposed behind the sub-fenders  23  and shielding the flanks of the vehicle body, and left and right engine sub-covers  27  disposed between the rear end side of the center cover  24  and the mud guards  26  and shielding the flanks of the vehicle body. 
   The front part of the center cover  24 , in the middle in the direction of the body width, serves as a fuel tank covering portion  31  for shielding a fuel tank  30 , and a seat  32  is centrally provided on the rear part of the center cover  24 . 
   As noted above, in the depicted embodiment, the fuel tank  30  is disposed underneath the fuel tank covering portion  31  of the center cover  24 . 
   As shown in  FIG. 2 , the fuel tank  30  in this embodiment is provided with a fuel tank body  36  having a filler neck  35  formed integrally thereon and protruding upwardly through an opening provided in the fuel tank covering portion  31 . Fuel supplied through this filler neck  35  is stored in the tank body  36 . The filler neck  35  is covered by a tank cap  37  when not in use, and the tank cap  37  is provided for opening and closing the fuel filler neck  35 . 
   The fuel tank  30  is also provided with a fuel system feed line  41  in fluid communication with a fuel feed pipe  61 , which extends through a lower wall of the tank body  36 . The fuel feed pipe  61  is a hollow, tubular conduit and has a pickup inlet  39  formed in an upper end thereof, opening into the fuel tank body  36 . 
   The vehicle  11  is also provided with a fuel pump  46  which draws fuel inwardly through the pickup inlet  39  of the fuel feed pipe  61 , and supplies it to other parts of a fuel injection system  40 , to be described subsequently. 
   The fuel tank  30  is also provided with a fuel return line  44  in fluid communication with a fuel return pipe  62  attached to the upper end thereof. The fuel return pipe  62  extends through a lower wall of the tank body  36 , and terminates to form a return port  43  opening inside the fuel tank body  36 . The fuel return line  44  returns recycled fuel from the fuel injection system  40  back into the fuel tank body  36 , through the return port  43 . 
   The fuel injection system  40  according to the illustrated embodiment is an electronically controlled fuel injection system, which provides a fuel flow circuit  45  for continuously circulating fuel therethrough while the vehicle&#39;s ignition is on. The fuel pump  46  is disposed midway on the fuel feed line  41 , and the fuel pump  46  draws fuel from the fuel tank body  36  via the fuel feed line  41 , and pressure-feeds the drawn fuel further along the fuel feed line  41 . 
   The fuel injection system  40  also includes an injector feed line  47  which branches off of the main fuel feed line  41 , and an electronically-controlled fuel injection valve, also referred to as a fuel injector  48 . The fuel injector  48  injects fuel, which has been pressure-fed by the fuel pump  46  via the fuel feed lines  41  and  47 , into an intake manifold (not shown) of the engine  13 , and this fuel is burned to power the engine  14 . 
   The fuel flow circuit  45  of the fuel injection system  40  also includes a return branch passage  49  which extends from the main fuel feed line  41  and branches off of the injector feed line  47  downstream of the fuel pump  46 . The fuel injection system  40  also includes a fuel pressure regulating valve  50  disposed in-line on this return branch passage  49 . The aforementioned fuel return line  44  is connected to the fuel pressure regulating valve  50  on the downstream side. Accordingly, it will be understood that unused fuel from the fuel feed line  41 , which is not expelled through the fuel injector  48  or retained in the fuel line, is routed back to the fuel tank body  36  through the return line  44 , via the fuel pressure regulating valve  50 . 
   As shown in  FIGS. 2-3 , in a first embodiment of the invention, a concave bowl portion  53 , having a central region depressed to a lower level than its circumference, is formed substantially centrally in the bottom part  52  of the fuel tank body  36 . This concave bowl portion  53  has a substantially tapered shape resembling a truncated cone, with its bottom part  54  arranged substantially horizontally, and with its wall face  55  inclined at an angle relative to the bottom part, and positioned facing more inward in the horizontal direction in the lower portion. It will be understood that other shapes may be used for the bowl portion  53  besides that shown, as long as the bowl portion forms a reservoir disposed below the remainder of the fuel tank body  36 . 
   In this first embodiment, the fuel feed pipe  61  and the fuel return pipe  62  extend, in a fluid-sealed manner, through apertures formed in the bottom part  54  of the concave bowl portion  53  in the bottom part  52  of the fuel tank body  36 . The fuel feed pipe  61  has a terminal fuel feed passage  41  defined therein to permit fuel flow therethrough, and the fuel return pipe  62  has a terminal fuel return passage  44  defined therein to permit fuel flow therethrough. 
   The upper tip end of the fuel feed pipe  61  is embedded in the bottom part  54  of the concave bowl portion  53 , and the pickup inlet  39  disposed at the upper tip end is directed perpendicularly upwardly toward the tank body  30 , so as to be aligned with the upper face of the bottom part  54 . 
   On the other hand, the fuel return pipe  62  passes through the bottom part  54  of the concave bowl portion  53 , with the tip end thereof disposed inside of the fuel tank body  36 . In the embodiment of  FIGS. 2-3 , the fuel return pipe  62  is formed in an inverted J-shape, including a linear portion  62 A rising perpendicularly in a linear configuration from the bottom part  54  of the concave bowl portion  53 . The fuel return pipe  62  also has a curved portion  62 B, with the upper surface thereof bending convexly upwardly from the upper end of the linear portion  62 A in a semi-circular form so as to position the return port  43 , at the outlet end thereof, over the fuel feed pipe  61 . 
   The fuel return pipe  62  is configured and arranged to direct the return port  43 , disposed at the terminal end of the curved portion  62 B, substantially perpendicularly downwardly and toward the pickup inlet of the fuel feed pipe  61 . 
   The pickup inlet  39  of the fuel feed pipe  61  is situated directly beneath and spaced apart from the return port  43  of the fuel return pipe  62 . This means that fuel flowing outwardly from the return port  43  will be directed towards the pickup inlet  39  of the fuel feed pipe. 
   Specifically, the pickup inlet  39 , whose diameter is smaller than that of the return port  43 , is positioned below, and arranged horizontally within a vertical extension of the diameter of the return port  43 , such that the inlet  39  and the vertical extension of the return port  43  are generally concentric and coaxial, and the vertical extension of the return port  43  overlaps the pickup inlet  39  in the horizontal direction. 
   In other words, the outlet of the fuel return line  44 , namely the return port  43  of the fuel return pipe  62 , is directed toward the fuel feed pipe  61 , namely the pickup inlet  39  of the fuel feed line  41 . The return port  43  and the pickup inlet  39  here are arranged in the hollow space within the concave bowl portion  53  in both the horizontal direction and the vertical direction. 
   In the embodiment so far described, as the return port  43  of the fuel return line  44  is directed toward the pickup inlet  39  of the fuel feed line  41 , fuel returned through the flow circuit  45  from the fuel pressure regulating valve  50  of the fuel injection system  40  to the fuel tank body  36  via the fuel return line  44  is discharged from the return port  43  of the fuel return line  44  toward the pickup inlet  39  of the fuel feed line  41 . 
   Therefore, when the quantity of fuel in the fuel tank body  36  has become small, fuel returned from the fuel pressure regulating valve  50  of the fuel injection system  40  into the fuel tank body  36 , via the fuel return line  44 , is rapidly and effectively drawn into the pickup inlet  39  and fed to the fuel pump  46  of the fuel injection system  40 , via the fuel feed line  41 . 
   As a result of the above-described arrangement of parts, bubble disruption of the fuel pump  46 , which could otherwise occur when the quantity of fuel in the fuel tank body  36  has become small, can be resisted, and the risk of fuel running out can be minimized. Moreover, as these features can be realized in a simple structure, there are advantages in weight and cost aspects. 
   Also, it is sufficient for the return port  43  only to be directed in a non-vertical stream toward the vicinity of the pickup inlet  39 , and variations are permitted in the curvature of the fuel return pipe  62 B, within the range of being directed toward the wall face  55  of the concave bowl portion  53  (see alternative phantom outlines shown in FIG.  3 ). As the bend of the return port  43  need not be great in that case, manufacturing and assembly are facilitated. 
   In addition, although the return port  43  of the fuel return line  44  is situated vertically opposite the pickup inlet  39  of the fuel feed line  41  in the specific example of the embodiment described above, their relative positions may be shifted in the horizontal direction if the return port  43  is moved closer to the pickup inlet  39 . However, the advantage noted above can be greater if the return port  43  is located vertically opposite and aligned with the pickup inlet  39 . 
   Further, it is possible to modify the above-described mode of implementation in the following way. 
   For instance, in a modified alternative embodiment of the invention, it is possible to connect the inlet and return pipes  161 ,  162  together with a plate-shaped member  164  to form a separate fuel routing apparatus  100 , as shown in FIG.  4 . The fuel routing apparatus of  FIG. 4  is usable to form the bottom part  154  of a modified concave bowl portion  153  of the fuel tank body  136 . In this second embodiment of the invention, the plate-shaped member  164  is made separate from the fuel tank body  136 , and the fuel feed pipe  161  and the fuel return pipe  162 , respectively define the fuel feed passage  141  and the fuel return passage  144  therein. The plate-shaped member  164 , in this embodiment, is sealably fit to the fuel tank body  136 . 
   In other words, the fuel feed line  141  and the fuel return line  144  form part of the fuel routing apparatus  100 , which may be fixed to the fuel tank body  136  via the plate-shaped member  164 . In this way, the arrangement of the fuel feed line  41  and the fuel return line  44  in the fuel tank body  36  is facilitated, and access to the fuel pipes for service and replacement is facilitated. In addition, in this case an embedded nut  165  is disposed in the fuel tank body  136  in advance, and the plate-shaped member  164  of the apparatus  100  is fitted to the fuel tank body  136  with a bolt  166  screwed into this embedded nut  165 . 
   In another alternative embodiment of the invention, as shown in  FIG. 5 , a modified version of a fuel routing apparatus  200  may be provided, in which a fuel filter  268  may be integrally fitted to the pickup inlet  239  of the fuel feed pipe  261 , to filter fuel entering the fuel feed passage  241  from the fuel tank body  236 . In this embodiment, as, shown in  FIG. 5 , the filter  268  may be installed in advance on the plate-shaped member  264 , together with the fuel feed pipe  261  and the fuel return pipe  262 . 
   The plate-shaped member  264 , in this embodiment, may be used to attach the fuel routing apparatus  200  to the fuel tank body  236 . Further in this case, if the return port  243  is directed toward the pickup inlet  239 , these elements may be shifted in position, apart or together, in the horizontal direction as shown in  FIG. 5 , but the return port  243  may, alternatively, be directed opposite the pickup inlet  239  in the perpendicular vertical direction, in the same way as described above in connection with the first embodiment. 
   While a limited number of illustrative embodiments of the present invention has been described, the present invention is not limited to the embodiments described above, but can be modified in various manners without departing from the spirit and scope of the present invention as set forth in the claims.