Abstract:
A wave absorbing member including a cage-shaped container housing a sponge that imparts resistance to the passing of fuel is arranged inside a tank body. Therefore, an impact by collision of the fuel can be absorbed, noise caused by undulation of the fuel can be reduced, and violent undulation of a fuel level can be effectively suppressed by the wave absorbing member. The wave absorbing member is supported by a pipe that is arranged inside the tank body and passes through a through hole formed in the container. A movement restricting member is provided on the pipe to limit movement of the wave absorbing member along the pipe. Therefore, the wave absorbing member is reliably positioned along the pipe and within the tank body with a simple structure.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a wave absorbing structure for a fuel tank that is arranged inside a fuel tank body, the wave absorbing structure including a wave absorbing member having a resistance member through which fuel can pass and which imparts resistance to the passage of the fuel. 
     2. Description of the Related Art 
     Japanese Patent Application Laid-open No. 2005-335436 discloses a technique in which the inside of a tank body formed by blow molding of a synthetic resin is sectioned into a first compartment and a second compartment by a narrow path, thereby allowing the path to exert a wave absorbing effect similar to a baffle plate. 
     In the technique disclosed in the JP 2005-335436 publication, however, the path is integrally formed inside the tank body. Thus, the tank body has a low degree of design freedom, and it is difficult to provide a wave absorbing effect in an existing tank body wherein the path is not provided. 
     To solve the problems, a wave absorbing structure for a fuel tank has been proposed in which a wave absorbing member including a cage-shaped container having a porous member for imparting resistance to passage of fuel is housed is arranged inside a tank body, and the wave absorbing member is supported by a pipe arranged inside the tank body that passes through a through hole formed in the container. Such a wave absorbing structure is disclosed in Japanese Patent Application No. 2008-175537. 
     The structure proposed in Japanese Patent Application No. 2008-175537 has a problem that since the pipe arranged inside the tank body passes through the through hole formed in the container of the wave absorbing member, the wave absorbing member moves along the pipe and is thus difficult to position. 
     Therefore, there exists a need in the art for a wave absorbing structure that has a simple structure and that may be reliably positioned along a pipe arranged inside the tank body. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished in light of such circumstances, and it is an object thereof to provide a simple structure to reliably position a wave absorbing member relative to a pipe arranged inside a tank body. 
     In accordance with the present invention, a wave absorbing structure for a fuel tank includes a wave absorbing member having a resistance member through which fuel can pass and which imparts resistance to the passage of the fuel. Within the tank body, the wave absorbing member is supported by a pipe that is arranged inside the tank body and passes through a through hole formed in the wave absorbing member. A movement restricting member for restricting movement of the wave absorbing member by abutting against a wall surrounding an opening portion of the through hole is also provided. 
     The wave absorbing member having the resistance member that resists the passage of fuel is arranged inside the tank body. Therefore, the wave absorbing member can absorb an impact by collision of the fuel, reduce noise caused by undulation of the fuel, and effectively suppress violent oscillation of the fuel level. The pipe is arranged inside the tank body and extends through the through hole formed in the wave absorbing member and thereby supports the wave absorbing member. The movement restricting member is arranged on the pipe and is brought into abutment with the wall surrounding the opening portion of the through hole. Accordingly, the wave absorbing member is prevented from moving along the pipe. 
     In accordance with another aspect of the present invention, the wave absorbing member includes a cage-shaped container for housing the resistance member. Therefore, the resistance member, which may be a porous member, can be easily and reliably supported by the cage-shaped container. 
     In further accordance with another aspect of the present invention, the pipe has a smooth portion located inside the wave absorbing member, and a bellows portion formed to have a larger diameter than that of the smooth portion and exposed outside the wave absorbing member. The bellows portion serves as the movement restricting member that prevents movement of the wave absorbing member. As such, movement of the wave absorbing member can be reliably restricted with a simple and inexpensive structure. Moreover, the bellows portion allows the pipe shape to be changed to any shape, so that the degree of layout freedom inside the tank body can be increased. 
     In accordance with an alternative movement restricting member of the present invention, the pipe includes a flange portion expanded in diameter by bulge forming, the flange portion serving as the movement restricting member. Therefore, movement of the wave absorbing member can be reliably restricted with a simple and inexpensive structure. 
     In accordance with a further alternative movement restricting member of the present invention, there is provided the wave absorbing structure for a fuel tank, further comprising a collar fitted around an outer periphery of the pipe outside the wave absorbing member, the collar serving as the movement restricting member. Therefore, movement of the wave absorbing member can be reliably restricted with a simple and inexpensive structure. 
     In accordance with a still further alternative movement restricting member of the present invention, there is provided the wave absorbing structure for a fuel tank, further comprising a clip locked onto an outer periphery of the pipe, the clip serving as the movement restricting member. Therefore, movement of the wave absorbing member can be reliably restricted with a simple and inexpensive structure. 
     According to the present invention, the pipe is a fuel transfer pipe. Therefore, a special member for supporting the wave absorbing member is not required, and the number of components can be reduced. 
     The above description, other objects, characteristics and advantages of the present invention will be clear from detailed descriptions which will be provided for the preferred embodiment referring to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal cross-sectional view of a vehicular fuel tank according to a first embodiment of the present invention; 
         FIG. 2  is an enlarged view of part  2  in  FIG. 1 ; 
         FIG. 3  a view from a direction of arrow  3  in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view taken along line  4 - 4  in  FIG. 3 ; 
         FIG. 5  is a view showing movement restricting means according to a second embodiment of the present invention; 
         FIG. 6  is a view showing movement restricting means according to a third embodiment of the present invention; 
         FIG. 7  is a view showing movement restricting means according to a fourth embodiment of the present invention; and, 
         FIG. 8  is an enlarged cross-sectional view taken along a line  8 - 8  in  FIG. 7 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now embodiments of the present invention will be described below with reference to the attached drawings. Initially, it is noted that a fuel suction pipe  36  corresponds to a pipe of the present invention; a sponge  39  corresponds to a resistance member of the present invention; and a bellows portion  36   a , a flange  36   c , a collar  42  and a clip  43  correspond to a movement restricting member of the present invention. As shown in FIG.  1 , a fuel tank T mounted on the bottom surface of a floor panel at a vehicle body rear portion of an automobile includes a tank body  11  formed by blow molding of a resin. A propeller shaft  12  for transmitting a driving force of an engine to rear wheels, and an exhaust pipe  13  for guiding an exhaust gas of the engine to the vehicle body rear portion are arranged in a groove-shaped concave portion  11   a  that extends in a front-and-rear direction through the center portion in the lateral direction of the bottom surface of the tank body  11 . The tank body  11  is sectioned into a first tank compartment  14  on the right side and a second tank compartment  15  on the left side by the concave portion  11   a . The first and second tank compartments  14  and  15  communicate with each other through a communicating portion  11   b  above the concave portion  11   a.    
     A first opening  11   d  having a male thread on its outer periphery is formed in an upper wall  11   c  of the first tank compartment  14 . A first lid body  16  for closing the first opening  11   d  is fixed while maintaining air tightness by a cap  17  having a female thread that is screwed with the male thread. A plurality of guide rods  18  are supported in a slidable manner in an up-and-down direction on the bottom surface of the first lid body  16 . An upper portion of a first chamber  19  whose upper surface opens is fixed to the plurality of guide rods  18 . The first chamber  19  is urged downward by resilient forces of coil springs  20  provided around the guide rods  18 . A lower surface of the first chamber  19  abuts against an upper surface of a bottom wall of the first tank compartment  14 . 
     A pump module  25  including a fuel pump  21 , a suction filter  22 , a pressure regulator  23  and a jet pump  24  is provided inside the first chamber  19 . The fuel pump  21  supplies fuel, which is drawn or sucked through the suction filter  22  arranged at the bottom portion of the first chamber  19 , to the engine through a fuel supply pipe  26 . The fuel supply pipe  26  penetrates through the first lid body  16  and extends to the outside of the tank body  11 . A fuel return pipe  27  branches away from the fuel supply pipe  26 , and the pressure regulator  23  is provided in the fuel return pipe  27 . The jet pump  24  is provided at a lower or tip end of the fuel return pipe  27 . The pressure regulator  23  keeps the pressure of the fuel supplied to the engine at a constant level, and returns excess fuel to the inside of the first chamber  19  via the jet pump  24 . The inside of first chamber  19  is thereby always filled with fuel. 
     On the other hand, a second opening  11   f  formed in an upper wall  11   e  of the second tank compartment  15  is closed by a second lid body  31  welded thereto by vibration welding or the like. A plurality of guide rods  32  are supported in a slidable manner in an up-and-down direction on a lower surface of the second lid body  31 . An upper portion of a second chamber  33  is fixed to lower portions of the guide rods  32 . The second chamber  33  is urged downward by resilient forces of coil springs  34  provided around the guide rods  32 . A lower surface of the second chamber  33  abuts against an upper surface of a bottom wall of the second tank compartment  15 . A flap or check valve (not shown), which allows fuel to flow into the second chamber  33  while preventing fuel from flowing out of the second chamber, is provided in the second chamber  33 . The inside of the second chamber  33  is thereby always filled with fuel. 
     A fuel suction pipe  36  extends from a suction filter  35 , which is arranged at the bottom portion of the second chamber  33 , to the first tank compartment  14 . The fuel suction pipe  36  extends through the communicating portion  11   b  between the first and second tank compartments  14 ,  15 , and is connected to the jet pump  24  inside the first chamber  19 . 
     Therefore, when the fuel pump  21  of the pump module  25  is operated during engine operation, fuel inside the first chamber  19  of the first tank compartment  14  is drawn or sucked up through the suction filter  22  and supplied to the engine via the fuel supply pipe  26 . Excess fuel is returned to the first chamber  19  through the jet pump  24  and the pressure regulator  23  of the fuel return pipe  27 . Fuel inside the second chamber  33  of the second tank compartment  15  is drawn or sucked up through the suction filter  35  by a negative pressure generated by the jet pump  24  and drawn into the first chamber  19  of the first tank compartment  14  through the fuel suction pipe  36  and the jet pump  24 . 
     When the fuel level inside the tank body  11  is higher than the upper end of the concave portion  11   a , the fuel levels in the first and second tank compartments  14  and  15  become equal to each other via the communicating portion  11   b . Thus, the above-described suction of the fuel by the jet pump  24  is meaningless. However, when the fuel level inside the tank body  11  is lower than the upper end of the concave portion  11   a , fuel inside the second tank compartment  15  cannot move to the first tank compartment  14  through the communicating portion  11   b . Thus, only the fuel in the first tank compartment  14  is consumed with the fuel in the second tank compartment  15  not being consumed. Accordingly, the fuel level in the first tank compartment  14  may be reduced and the fuel supply to the engine may be stopped early. 
     However, since fuel in the second tank compartment  15  is supplied to the first tank compartment  14  by the jet pump  24 , as described above, the fuel level in the second tank compartment  15  is always maintained at a high level, and the fuel in the tank body  11  can be used up to the end. 
     Three wave absorbing members  37  are provided on the fuel suction pipe  36 . When the fuel level inside the tank body  11  violently undulates due to turning movement or oscillation of a vehicle, the wave absorbing members  37  function to stabilize the fuel level by suppressing the movement of the fuel. 
     As shown in  FIGS. 2 to 4 , each of the wave absorbing members  37  includes a cage-shaped container  38  having a cylindrical shape. The container  38  is formed by first and second half bodies  38 L and  38 R, which are preferably identical to one another, and that are integrated by bonding or welding to form the cage-shaped container. For example, the first half body  38 L includes a coupling rib  38   a  coupled to the second half body  38 R and having a square frame shape, four arc-shaped lateral ribs  38   b  for connecting the coupling rib  38   a  in a peripheral direction, six square U-shaped vertical ribs  38   c  for connecting the coupling rib  38   a  in an axial direction, boss portions  38   d  provided at the opposite ends of the coupling rib  38   a  in the axial direction, and support portions  38   e  formed in the centers of the boss portions  38   d  such that the fuel suction pipe  36  can extend therethrough. 
     A sponge  39 , which is a porous member having a large open space, is received or housed in the container  38 . After the sponge  39  is disposed in the container  38 , the first and second half bodies  38 L and  38 R of the container  38  are bonded or welded to each other at or along the coupling ribs  38   a  and  38   a . A diameter D 1  of the cylindrical container  38  is set to be smaller than a diameter D 2  of each of the first and second openings  11   d  and  11   f  of the tank body  11  (see  FIG. 1 ). Accordingly, the wave absorbing members  37  can be inserted into the tank body  11  through the first or second openings  11   d  and  11   f , which are also used for inserting the pump module  25  or the suction filter  35 . Therefore, the wave absorbing members do not require special openings to permit insertion of the wave absorbing members  37  into the tank body  11 . Since the sponge  39  is housed in the container  38 , the sponge  39 , which has an unstable shape, can be easily and reliably supported. 
     The resin fuel suction pipe  36  includes a bellows portion  36   a  having a bellows-shaped pipe, and a smooth portion  36   b  having a simple smooth-sided pipe. The maximum outer diameter of the bellows portion  36   a  is larger than the outer diameter of the smooth portion  36   b . The smooth portion  36   b  is received in the wave absorbing member  37 . The opposite end portions of the smooth portion  36   b  are fitted into through holes  38   f  and  38   f  formed in the support portions  38   e  and  38   e  of the container  38 . An intermediate portion of the smooth portion  36   b  extends through the sponge  39 . The bellows portion  36   a  of the fuel suction pipe  36  is disposed outside the wave absorbing member  37 . The end portions of the bellows portion  36   a  having a larger diameter than the smooth portion  36   b  abut against the wall surrounding the opening ends of the through holes  38   f  and  38   f  of the support portions  38   e  and  38   e  of the container  38 . 
     The wave absorbing member  37  is thereby held on the outer periphery of the smooth portion  36   b  of the fuel suction pipe  36 , and is prevented from moving along the fuel suction pipe  36  by engagement with the bellows portions  36   a . Accordingly, the wave absorbing members  37  are held in position relative to one another and are reliably prevented from violently moving or colliding with each other inside the tank body  11 . 
     Also, since the wave absorbing members  37  are supported by using the fuel suction pipe  36  provided inside the tank body  11 , a special support member for supporting the wave absorbing members  37  is not required, so that the structure is simplified. Furthermore, since the bellows portions  36   a  of the fuel suction pipe  36  are freely bendable, a high degree of layout freedom of the fuel suction pipe  36  inside the tank body  11  is provided. 
     As will be appreciated by those skilled in the art, the wave absorbing member  37  can be assembled on or over the smooth portion  36   b  of the fuel suction pipe  36  by coupling the divided first and second half bodies  38 L and  38 R of the container  38  with the smooth portion  36   b  held therebetween. The bellows portions  36   a  serve as movement restricting members to limit movement of the wave absorbing member  37  along the fuel suction pipe  36 . 
     Accordingly, due to the provision of the wave absorbing members  37  within the fuel tank body  11 , even when the fuel level inside the tank body  11  violently undulates during operation of the vehicle, the movement of the fuel is suppressed by the wave absorbing members  37  to stabilize the fuel level and permit fuel to be stably supplied to the engine. Further, since the sponge  39  housed in the container  38  is a porous member, the sponge  39  does not completely block the passage of fuel. Any load experienced from the moving fuel is thereby reduced to prevent the fuel suction pipe  36  from being deformed. Furthermore, although the porous member (sponge  39 ) has an unstable shape, the porous member is housed in the cage-shaped container  38 , thereby stabilizing the shape and avoiding interference with other members received within the fuel tank body  11 . 
     A second embodiment of the present invention will be described with reference to  FIG. 5 , in which an alternative movement restricting member is provided. 
     A fuel suction pipe  36 ′ according to the second embodiment is a pipe having a circular shape in section basically with a constant diameter. The fuel suction pipe  36 ′ is expanded in diameter at appropriate positions by bulge forming to form flange portions  36   c . When a wave absorbing member  37  is mounted on the fuel suction pipe  36 ′, a pair of flange portions  36   c  and  36   c  of the fuel suction pipe  36 ′ abuts against walls surrounding opening ends of through holes  38   f  and  38   f  of support portions  38   e  and  38   e  of a container  38 , and thereby immovably hold the wave absorbing member  37  at a predetermined position on the fuel suction pipe  36 ′. The flange portions  36   c ,  36   c  serve as movement restricting members to limit movement of the wave absorbing member  37  along the fuel suction pipe  36 ′. 
     A third embodiment of the present invention will be described with reference to  FIG. 6 , in which an alternative movement restricting member is provided. 
     The fuel suction pipe  36 ″ according to the third embodiment is a pipe having a circular shape in section with a constant diameter. A plurality of collars  42  having a larger diameter than that of the fuel suction pipe  36 ″ and a plurality of wave absorbing members  37  are alternately fitted around the outer periphery of the fuel suction pipe  36 ″. The outer ends of the two collars  42  and  42  at the opposite ends of the fuel suction pipe  36 ″ immovably abut against first and second chambers  19  and  33  (see  FIG. 1 ), thereby immovably holding each of the wave absorbing members  37  at a predetermined position on the fuel suction pipe  36 ″ via the collars  42  and  42  at the opposite ends. 
     A fourth embodiment of the present invention will be described with reference to  FIGS. 7 and 8 , in which a further alternative movement restricting member is provided. 
     A fuel suction pipe  36 ″′ according to the fourth embodiment is a pipe having a circular shape in section with a constant diameter. Removable clips  43  and  43  are mounted at appropriate positions on the fuel suction pipe  36 ″′. Each of the clips  43  bendably couples one end of a pair of arc-shaped body portions  43   a  and  43   a  by a hinge portion  43   b . Each of the clips  43  also forms a locking projection  43   e  at one of coupling portions  43   c  and  43   d  provided on the other end of the body portions  43   a  and  43   a  and forms a locking hole  43   f  at the other of the coupling portions  43   c  and  43   d . The locking projection  43   e  is fitted into the locking hole  43   f  with the pair of arc-shaped body portions  43   a  and  43   a  being positioned on the outer periphery of the fuel suction pipe  36 ′. The clips are thereby fixed to the fuel suction pipe  36 . The clips  43  and  43  exert a similar function to that of the flange portions  36   c  and  36   c  according to the second embodiment, thereby immovably holding each of wave absorbing members  37  at a predetermined position on the fuel suction pipe  36 ′. As such, the clips  43 ,  43  limit movement of the wave absorbing members  37  along the fuel suction pipe  36 ′. 
     Accordingly, movement of the wave absorbing members  37  can be reliably restricted with a simple and inexpensive movement restricting members according to the first to fourth embodiments. 
     The embodiments of the present invention provide alternative movement restricting members, and are described above in detail, but various design changes may be made therein without departing from the scope of the present invention. 
     For example, although the fuel tank T in the embodiments includes the first and second tank compartments  14  and  15 , the fuel tank T may include only a single tank compartment. 
     Also, in the embodiments, the resistance member (the sponge  39  in the embodiments) and the container  38  constitute the wave absorbing member  37 . However, only the resistance member may constitute the wave absorbing member  37  by omitting the container  38 . In this case, the through hole is formed in the resistance member itself.