Patent Publication Number: US-2009223973-A1

Title: Fuel tank apparatus

Description:
TECHNICAL FIELD 
     The present invention generally relates to a fuel tank apparatus and, more specifically, to a fuel tank apparatus having a sub-cup for holding fuel near a filter provided in the fuel tank. 
     Background Art 
     In connection with a conventional fuel tank apparatus, Japanese Patent Laying-Open No. 07-148405 discloses a fuel filter aimed at suppressing wear of a filter caused by friction with a frame. In this reference, a fuel filter is arranged in a chamber provided in the fuel tank, and connected to a fuel pump through a suction pipe. When the fuel pump is driven, the fuel in the fuel tank is filtered by the fuel filter and thereafter fed to an engine through the suction pipe. 
     Further, Japanese Patent Laying-Open No. 2003-28019 discloses a fuel filter device aimed at improving oil/water separation function. 
     Water entering from a filler opening or moisture in the air condensed in the fuel tank may possibly be mixed in the fuel in the fuel tank. Therefore, the fuel tank disclosed in Japanese Patent Laying-Open No. 07-148405 has a fuel filter in order to prevent supply of the water mixed in the fuel to the engine. 
     Assume that a vehicle having the fuel tank mounted is kept stopped for a long period of time and the fuel and water are separated from each other. In that case, the fuel filter might possibly be submerged below the water level, if the amount of water mixed in the fuel were too large. In such a case, it becomes impossible to feed the fuel to the engine, and hence, the vehicle can not be re-started. Similar problem might occur in the fuel filter device disclosed in Japanese Patent Laying-Open No. 2003-28019. 
     DISCLOSURE OF THE INVENTION 
     An object of the present invention is to prevent the above-described problem and to provide a fuel tank apparatus enabling more reliable fuel supply even when a large amount of water is retained in the tank. 
     The fuel tank apparatus in accordance with the present invention includes a container having a bottom portion and a side portion erected on the bottom portion and provided in a fuel tank and a fuel filter arranged in a space surrounded by the side portion above the bottom portion and connected to a fuel pump. Maximum height of the fuel filter is higher than the minimum height of the side portion. 
     In the fuel tank apparatus structured as described above, when the fuel and water are separated in the fuel tank, the water having relatively high density forms a lower layer and the fuel having relatively low density forms an upper layer. Here, even if the water should be retained in the container, the fuel at the upper portion of the container can be sucked in through the fuel filter to the fuel pump, as the fuel filter is formed to a position higher than the side portion of the container. Thus, the tolerable amount of water retention in the fuel tank can be increased, and the fuel in the fuel tank can more reliably be sucked in through the fuel filter. 
     The fuel tank apparatus further includes a tube for feeding part of the fuel emitted from the fuel pump through the fuel filter back to the fuel tank. The side portion includes a partition wall partitioning the space into a main chamber in which the fuel filter is arranged and a sub-chamber. In the sub-chamber, the fuel is fed from the fuel tank, by a negative pressure generated by the fuel flow in the tube. The fuel fed to the sub-chamber goes over the partition wall into the main chamber. Preferably, the maximum height of the fuel filter is higher than the height of the partition wall. 
     In the fuel tank apparatus structured as described above, even when water is retained in the main chamber of the container, the water that exceeds the height of the partition wall flows to the sub-chamber. Therefore, the level of water retained in the main chamber is not higher than the height of the partition wall. Accordingly, by arranging the fuel filter to a position higher than the partition wall, it becomes possible to suck in the fuel above the partition wall through the fuel filter to the fuel pump. 
     Preferably, the fuel filter is water-repellent. In the fuel tank apparatus structured as described above, the amount of water sucked in through the fuel filter can be reduced. Thus, the normal operation of the engine fed by the fuel becomes more reliable. 
     As described above, according to the present invention, a fuel tank apparatus can be provided that enables more reliable fuel supply even when a large amount of water is retained in the tank. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view showing a fuel tank apparatus in accordance with Embodiment 1 of the present invention. 
         FIG. 2  is a cross-sectional view showing, in greater detail, the portion surrounded by two-dotted line II of  FIG. 1 . 
         FIG. 3  is a cross-sectional view of the fuel tank apparatus along the line III-III of  FIG. 2 . 
         FIG. 4  is a cross-sectional view of the fuel tank apparatus when the fuel pump is stopped. 
         FIG. 5  is a cross-sectional view showing a fuel tank apparatus in accordance with Embodiment 2 of the present invention. 
     
    
    
     BEST MODES FOR CARRYING OUT THE INVENTION 
     Embodiments of the present invention will be described with reference to the figures. In the figures referred to in the following, the same or corresponding components are denoted by the same reference characters. 
     Embodiment 1 
       FIG. 1  is a cross-sectional view showing a fuel tank apparatus in accordance with Embodiment 1 of the present invention. 
     Referring to  FIG. 1 , a fuel tank apparatus  10  in accordance with the present embodiment is mounted on a vehicle, and supplies fuel to an engine as a power source of the vehicle. 
     Fuel tank apparatus includes: a fuel tank  12  having a bottom surface  12   c  and an opening  14 ; a sub-cup  21  inserted through opening  14  into fuel tank  12  and arranged on bottom surface  12   c;  and a suction filter  31  and a fuel pump  41  provided inside the sub-cup  21 . Fuel tank  12  is formed of resin. Fuel tank  12  maybe formed of metal such as iron. 
     To fuel tank  12 , a filler tube communicated with a filler inlet  17  for supplying fuel to the tank is connected. A lid  13  is provided on fuel tank  12  to close opening  14 . Sub-cup  21  is connected to lid  13  with a spring  15  inserted therebetween. Sub-cup  21  is urged to bottom surface  12   c  by the elastic force of spring  15 . Thus, sub-cup  21  follows deformation of fuel tank  12  and is always kept placed on bottom surface  12   c.    
     The fuel in fuel tank  12  is first fed to sub-cup  21  and then sucked in by suction filter  31 . Therefore, even when the vehicle is inclined with only a little fuel left in fuel tank  12  and the fuel is collected at one corner of the tank, the fuel that has been fed to sub-cup  21  can be held around suction filter  31 . Therefore, air-suction by suction filter  31  can be prevented. 
       FIG. 2  is a cross-sectional view showing, in greater detail, the portion surrounded by two-dotted line II of  FIG. 1 . In the figure, the fuel tank apparatus when fuel pump  41  of  FIG. 1  is in operation is depicted.  FIG. 3  is a cross-sectional view of the fuel tank apparatus along the line III-III of  FIG. 2 . 
     Referring to  FIGS. 2 and 3 , sub-cup  21  is formed of a bottom portion  22  extending over bottom surface  12   c,  and a side portion  23  continuous from bottom portion  22 . Side portion  23  includes a side wall  23   m  erected vertically upward from a circumferential edge of bottom portion  22  and forming a space above bottom portion  22 , and a partition wall  23   n  erected vertically upward from the surface of bottom portion  22  and partitioning the space formed by sidewall  23   m  into a main chamber  28  and sub-chamber  29 . 
     Partition wall  23   n  has a constant height H 2 . Height H 2  refers to the length of partition wall  23   n  in the vertical direction measured from the bottom portion  22 . Height H 2  is lower than the height of sidewall  23   m  from the bottom portion  22 , and it is the minimum height of side portion  23  from bottom portion  22 . 
     Suction filter  31  is arranged on bottom portion  22  in main chamber  28 . Suction filter  31  is formed to extend parallel to bottom portion  22  and then bent on bottom portion  22  in a direction apart from bottom portion  22 . Suction filter  31  has a portion extending vertically upward from the bottom portion  22 . 
     Suction filter  31  is formed of a water-repellent filter material having a contact angle with water of 90° or larger, such as polypropylene, polytetrafluoroethylene or polyethylene. Water may possibly be mixed in the fuel in fuel tank  12 , as water may accidentally enter from filler inlet  17  of  FIG. 1  at the time of filling, or moisture in the air in fuel tank  12  may be condensed. Suction filter  31  formed of water-repellent filter material suppresses supply of water to the engine. 
     In the present embodiment, suction filter  31  is formed by bending unwoven fabric of the material mentioned above and by heat-welding an end portion where the unwoven fabrics are overlapped. Suction filter  31  has a welded portion  31   d  where the unwoven fabrics are heat-welded. Suction filter  31  has a height H 1 . Height H 1  represents length of suction filter  31  in the vertical direction measured from bottom portion  22 . Height H 1  represents the maximum height of suction filter  31  that can suck in the fuel, that is, the height of suction filter  31  except for the welded portion  31   d . Suction filter  31  is formed such that height H 1  becomes larger than height H 2  of partition wall  23   n.  In the present embodiment, height H 1  of suction filter  31  is lower than the height of sidewall  23   m.    
     Here, bottom portion  22  as a reference position of measuring heights H 1  and H 2  extends in the horizontal direction for mounting on a vehicle. It is not limiting, and the heights H 1  and H 2  maybe measured each from the reference position of the same height. 
     To suction filter  31 , fuel pump  41  is connected. Fuel pump  41  is positioned in main chamber  28 . Fuel pump  41  is further connected through a fuel flow path  44  to engine  18 . 
     Sub-cup  21  is provided with an inlet tube  26  for communication between sub-chamber  29  and the inside of fuel tank  12 . Inlet tube  26  is arranged on bottom portion  22 . At the position where inlet tube  26  opens into sub-chamber  29 , a flapper valve  27 , which can be opened/closed, is provided. Flapper valve  27  allows fuel flow from fuel tank  12  to sub-chamber  29 , and regulates fuel flow from sub-chamber  29  to fuel tank  12 . 
     Sealing of inlet tube  26  by flapper valve  27  is not very tight, and therefore, when fuel pump  41  is kept stopped for a long period of time, the fuel in sub-cup  21  moves through inlet tube  26  to fuel tank  12 . Therefore, if the vehicle is kept parked for a long period of time in an inclined state with only a small amount of fuel left in fuel tank  12 , suction filter  31  may possibly be exposed out of the fuel. in the present embodiment, however, suction filter  31  is arranged in main chamber  28  partitioned from inlet tube  26 , and therefore, the fuel retained in main chamber  28  as the fuel used for starting the vehicle next time can reliably be held around suction filter  31 . 
     At a position of fuel tank  12  adjacent to inlet tube  26 , a jet pump  47  is arranged. Jet pump  47  is connected through a return flow path  45  to fuel flow path  44 . On the passage of return flow path  45 , a pressure regulator  46  is provided for maintaining constant the pressure of fuel fed to engine  18 . 
     When fuel pump  41  is operated, the fuel fed through suction filter  31  to fuel flow path  44  is supplied to engine  18 . Part of the fuel passing through fuel flow path  44  is fed through return flow path  45  to jet pump  47 . At this time, because of the fuel flow through return flow path  45 , a negative pressure generates in jet pump  47 , and by the negative pressure, the fuel in fuel tank  12  is drawn into jet pump  47 . The fuel is emitted from jet pump  47  to inlet tube  26 , and enters sub-chamber  29 . The fuel that exceeded the height of partition wall  23   n  of sub-chamber  29  flows into main chamber  28 . The fuel pooled in this manner in main chamber  28  is sucked in by suction filter  31 . 
       FIG. 4  is a cross-sectional view of the fuel tank apparatus when the fuel pump is stopped. Referring to  FIG. 4 , if the fuel pump is kept stopped for a long period of time, the fuel in sub-cup  21  gradually moves through inlet tube  26  to fuel tank  12 , and therefore, the level of fuel in sub-cup  21  comes to be approximately equal to the level of fuel in fuel tank  12 . On the other hand, in fuel tank  12 , water that has been mixed in the fuel comes to be separated from the fuel, and the water forms a lower layer and the fuel forms an upper layer. 
     The fuel in fuel tank  12  is collected to main chamber  28  in sub-cup  21 , and then, because of the water-repellent suction filter  31 , supply to engine  18  is prevented. Therefore, if a large amount of water is mixed in the fuel, it follows that the amount of water  100  retained in main chamber  28  would be increased when the water is separated from the fuel. If the level  101  of water  100  exceeds the height of partition wall  23   n , however, the water flows over partition wall  23   n  into sub-chamber  29 , and further through inlet tube  26  to be retained on bottom surface  12   c  of fuel tank  12 . Therefore, it is expected that, when the largest amount of water is retained in sub-cup  21 , main chamber  28  is filled with water. In the present embodiment, suction filter  31  is formed to a position higher than partition wall  23   n  and, therefore, the fuel at a position higher than partition wall  23   n  can be sucked in through suction filter  31 . 
     Fuel tank apparatus  10  in accordance with Embodiment 1 of the present invention includes sub-cup  21  as a container having bottom portion  22  and side portion  23  erected from bottom portion  22  and provided in fuel tank  12  and suction filter  31  as a fuel filter arranged in a space surrounded by side portion  23  above bottom portion  22  and connected to fuel pump  41 . The maximum height H 1  of suction filter  31  is higher than the minimum height H 2  of side portion  23 . 
     Fuel tank apparatus  10  further includes return flow path  45  as a pipe for returning part of the fuel emitted from fuel pump  41  through suction filter  31  back to fuel tank  12 . Side portion  23  includes partition wall  23   n  partitioning the space into main chamber  28  in which suction filter  31  is arranged, and a sub-chamber  29  adjacent to main chamber  28 . To sub-chamber  29 , the fuel is fed from fuel tank  12 , because of a negative pressures generated by the fuel flow in return flow path  45 . The fuel fed to sub-chamber  29  flows over partition wall  23   n  into main chamber  28 . The maximum height H 1  of suction filter  31  is higher than the height H 2  of partition wall  23   n.    
     By fuel tank apparatus  10  in accordance with Embodiment 1 having the above-described structure, when engine  18  is to be started after the vehicle has been parked for a long period of time, the fuel can more reliably be supplied to engine  18 . Thus, it is possible to start normal running of the vehicle without causing malfunction or failure of the engine. 
     Though an example in which fuel tank  12  has bottom surface  12   c  that extends flat has been described, fuel tank  12  may be formed in a saddle shape, to avoid a propeller shaft. Further, separate from return flow path  45  having pressure regulator  46  provided therein, a flow path branched from fuel flow path  44  may be provided, and jet pump  47  may be arranged in the flow path. 
     Embodiment 2 
       FIG. 5  is a cross-sectional view showing a fuel tank apparatus in accordance with Embodiment 2 of the present invention.  FIG. 5  corresponds to  FIG. 4  of Embodiment 1. The fuel tank apparatus in accordance with the present embodiment basically has a similar structure as fuel tank apparatus  10  in accordance with Embodiment 1. In the following, description of overlapping components will not be repeated. 
     Referring to  FIG. 5 , in the present embodiment, partition wall  23   n  shown in  FIG. 2  is not provided, and side portion  23  of Embodiment 1 includes sidewall  23   m  only. Sidewall  23   m  has a constant height H 3 . Height H 3  represents length of sidewall  23   m  measured from bottom portion  22 . Suction filter  31  is formed such that height H 1  is higher than height H 2  of sidewall  23   m.    
     In the fuel tank apparatus of Embodiment 2 structured as described above, even when a large amount of water is mixed in the fuel in fuel tank  12  and sub-cup  21  should be filled with water, the fuel at a position higher than sub-cup  21  can be sucked in through suction filter  31 . Thus, effects similar to those attained by Embodiment 1 can be attained. 
     It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. 
     INDUSTRIAL APPLICABILITY 
     The present invention is mainly applicable to a fuel tank apparatus mounted on a vehicle and supplying fuel to an engine as a power source of the vehicle.