Abstract:
A fitting structure for attaching a fuel pump in a fuel tank, which includes a gasket surrounding a pump insertion hole of the fuel tank. The gasket is collapsed by a presser ring through a flange portion of the fuel pump, thus enabling the gasket to provide an effective seal between the fuel pump and the fuel tank. A nut fastened onto a bolt is used to bring a second valley portion of the presser ring into close contact with a first mount portion of a fixed side ring that has been preliminarily welded to the fuel tank, thus securely fitting the fuel pump to the fuel tank. As compared with a conventional fitting structure using a bayonet or snap fit connection, wherein the fitting structure must be turned against the gasket to be fitted into a secure position, this new fitting structure presses the gasket into place, thus avoiding the turning motion and the resulting damage that may be caused to the gasket. In addition, the new structure eliminates the possibility of applying excessive compression force to the flange portion of the fuel pump, thus preventing the possibility of causing creep distortion to the flange portion, even when the flange portion is made of a light-weight resin.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an improvement in a tank fitting structure for a fuel pump. 
     2. Description of Background Art 
     FIG. 4 of Japanese Pre-examination Patent Publication (KOKAI) No. 8-232792 (1996) “In-tank Type Fuel Pump Device” shows an in-tank type fuel pump 2 fitted to a fuel tank 1 (the symbols and the numerals used in the No. 8-232792 publication are the same as those used in disclosure of the present invention that follows). A fitting structure consisting of flange 24 of in-tank type fuel pump 2 is shown in detail in FIG. 31 of the publication. FIG. 31 of this publication is reprinted as FIG. 14 herein. The structure shown is described in detail below. 
     FIGS.  14 ( a ) to  14 ( c ) reprints FIG. 31 of the Japanese Pre-examination Patent Publication (KOKAI) No. 8-232792 (1996), in which  14 ( c ) coincides with FIG. 31, and  14 ( a ) and  14 ( b ) are illustrations of mounting to obtain  14 ( c ). 
     In FIG.  14 ( a ), presser claw  102  is preliminarily fitted to an edge of pump insertion hole  101  of fuel tank  100 , and gasket  103  is positioned on the edge of the pump insertion hole  101 . Earth minus terminal  106  is fitted to rib  105  which droops down from flange  104  of the pump. Flange  104  is positioned on the gasket  103  (arrow {circle around ( 1 )}). 
     FIG.  14 ( b ) shows the condition where flange  104  is positioned on gasket  103 , and, while pushing flange  104  as indicated by the downward arrow, stopper metal  107  is lowered to a side of presser claw  102  as indicated by arrow {circle around ( 2 )}. The stopper metal  107  is turned as indicated by arrow {circle around ( 3 )}, whereby stopper metal  107  is hooked under presser claw  102 . 
     FIG.  14 ( c ) shows completion of mounting, in which gasket  103  causes a pushing up force on flange  104 . By pressing flange  104  against stopper metal  107 , flange  104  is fitted and sealed to fuel tank  100 . 
     The connecting structure created as described above by turning and hooking the stopper metal  107  onto the presser claw  102  on the fixed side is called a snap fit or a bayonet connection. Snap fit and bayonet connections are simple connecting methods and are widely adopted. 
     However, as is clear from FIG.  14 ( c ), the simple structure leads to dispersion in the collapsing amount of gasket  103 . Furthermore, problems exist with snap fit and bayonet connections in the case of, for example, autobicycles which are subject to large vibrations. 
     One way to address the above issues, may be to consider increasing the size of gasket  103  to increase the collapsing allowance, or to form gasket  103  from a hard material to enhance the spring coefficient. However, with this approach, the pressing force indicated by the downward arrow in FIG.  14 ( b ) would have to be increased, requiring presser claw  102  and stopper metal  107  to be made more rigid, leading to an increase in parts cost. In addition, the turning torque of stopper metal  107  indicated by arrow {circle around ( 3 )} in FIG.  14 ( b ) would have to be increased, making the work of fitting the fuel pump to the tank more difficult. 
     Further, for lightness in weight and corrosion resistance, flange  104  may sometimes be made of a resin. Resins suffer from deformation called creep when being compressed by a high pressure for a long time. Therefore, increasing the pressing force is not desirable. 
     Also, when designing a fuel tank for an autobicycle, in many cases the pump unit is inserted into a tank bottom upwards from the lower side, and then fixed to the tank. In such a case, the center of gravity of the pump unit is above the flange, causing a large force to be exerted on the flange at the time of lateral turning. Thus, snap fit or bayonet connections are generally not suitable for such use. 
     As described above, pump fitting structures according to the prior art are not suitable for vehicles receiving large vibrations such as an autobicycle. Thus, it is the object of the present invention to provide a fitting structure for a fuel pump which replaces the snap fit or bayonet connection. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     In order to attain the above object, the present invention includes a gasket that is positioned on an edge of a pump insertion hole provided in a fuel tank. A fixed side ring is preliminarily fitted to the fuel tank at a position for surrounding the gasket, and major part of a pump unit, is inserted into the fuel tank through the pump insertion hole while placing a flange portion projected from the pump unit on the gasket. The inside surface of a presser ring is positioned on the flange portion, and the outside surface of the presser ring faces the fixed side ring. Further, the outside surface of the presser ring is brought into close contact with the fixed side ring by a fastening member, thus fitting the pump unit to the fuel tank. 
     The gasket is positioned on the flange portion, and the flange portion is pressed by an inside surface of the presser ring thereby collapsing the gasket. The collapsing amount is determined by the position at which the presser ring comes into contact with the fixed side ring. As such, the collapsing amount of the gasket is constant even if the fastening force of the fastening member is increased. When the fastening force of the fastening member is increased, only the connection between the fixed side ring and the presser ring is increased. A compressing force acting on the flange portion coincides with the springy force of the gasket. According to the present invention, the springy force of the gasket is fixed, thus preventing a situation where a compressing force beyond a certain level would be exerted on the flange portion. As such, generation of creep in the flange portion can be obviated, even when the flange portion is made of a resin. 
     As a result, sealing performance is stabilized, and a good seal can be maintained even under conditions of heavy vibration. 
     The present invention further includes a fixed side ring formed with first valley portions and first mount portions alternately provided by bending a steel sheet. The first valley portions are connected to the fuel tank, and the first mount portions are used as receiving surfaces for the presser ring. The presser ring is formed with second valley portions and second mount portions alternately provided by bending a steel sheet. These second valley portions are brought into contact with the first mount portions, and the flange portion of the pump unit is held by inside surfaces of the second mount portions. 
     In order to bring the presser ring into close contact with the fixed side ring and to appropriately press the flange portion by the presser ring, desired shapes are arranged by bending a sheet. Since the rings are formed from a sheet, a reduction in weight of the fixed side ring and the presser ring is possible. 
     The present invention further includes a flange portion of the pump unit made of a resin. As a result, a reduction of both the weight and the cost of the pump unit is accomplished. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a conceptual illustration of a fuel tank and a pump unit according to the present invention; 
     FIG. 2 is an exploded view of a tank fitting structure for a pump unit according to the present invention (First Embodiment); 
     FIG. 3 is a plan view of a fixed side ring according to the present invention (First Embodiment); 
     FIG. 4 is a view taken along arrow  4  of FIG. 3; 
     FIG. 5 is a plan view of a presser ring according to the present invention (First Embodiment); 
     FIG. 6 is a view taken along arrow  6  of FIG. 5; 
     FIG. 7 is a view showing a tank fitting procedure for a fuel pump according to the present invention (First Embodiment); 
     FIG. 8 is a view taken along arrow  8  of FIG. 7; 
     FIG. 9 is a view showing a tank fitting structure for a fuel tank according to the present invention (First Embodiment); 
     FIG. 10 is a perspective view of a fixed side ring and a presser ring according to Second Embodiment of the present invention; 
     FIGS.  11 ( a ) and  11 ( b ) are views showing a tank fitting procedure for a fuel pump according to the present invention (Second Embodiment); 
     FIG. 12 is a perspective view of a fixed side ring and a presser ring according to Third Embodiment of the present invention; 
     FIGS.  13 ( a ) and  13 ( b ) are views showing a tank fitting procedure for a fuel tank according to the present invention (Third Embodiment); and 
     FIGS.  14 ( a )- 14 ( c ) are reprints of FIG. 31 of Japanese Pre-examination Patent Publication (KOKAI) No. 8-232792 (1996) and an illustration of mounting. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Next, a mode for carrying out the present invention will be described referring to the attached drawings. 
     FIG. 1 is a conceptual illustration of a fuel tank for an autobicycle and a pump unit according to the present invention, in which pump unit  20  is fitted, as indicated by arrow {circle around ( 3 )}, to fuel tank  10  provided with fuel feed cap  11  at an upper portion. With flange portion  21  directed downwards, pump unit  20  is inserted upwards thereby fitting pump unit  20  to fuel tank  10 . By this arrangement, the design of fuel tank  10  can be maintained. 
     In the following figures and description, pump unit  20  is inverted upside down for convenience. 
     FIG. 2 is an exploded view of a tank fitting structure for a pump unit according to the present invention (First Embodiment). The tank fitting structure for the pump unit includes a pump insertion hole  12  provided in fuel tank  10 , fixed side ring  30  fitted to fuel tank  10  in the manner so as to surround pump insertion hole  12 , and bolts  31  . . . ( . . . means a plurality, here and hereinafter) as part of the fastening member fitted by welding to fixed side ring  30 . The tank fitting structure also includes gasket  35 , pump unit  20  provided with flange portion  21 , presser ring  40 , and nuts  50  . . . as the remainder of the fastening member. 
     Describing pump unit  20  briefly, a motor pump and a strainer (both not shown) are incorporated in resin-made pump case  22  provided integrally with flange portion  21 , and a fuel is drawn in through port  23 , is pressurized by the motor pump, is filtered through the strainer, and then is ejected through discharge port  24 . Numeral  25  denotes a cover, and  26  denotes a connector fitting port. 
     FIG. 3 is a plan view of the fixed side ring according to the present invention (First Embodiment), and FIG. 4 is a view taken along arrow  4  of FIG.  3 . 
     Fixed side ring  30  comprises a plurality (for example, 6) of first valley portions  32  . . . and first mount portions  33  . . . alternately provided by press punching and bending of a steel sheet. Inside diameter D 1  of fixed ring  30  is greater than the outside diameter of the gasket  35  (See FIG.  2 ). Each of first mount portions  33  is provided with a bolt hole  34 , and bolt  31  is inserted in bolt hole  34  from the lower side. Head  31   a  of bolt  31  is preliminarily provided with a small projection for projection welding. An electric current is passed through the small projection while it is kept in contact with the lower side of first mount portion  33 , concentrating the current to the small projection, thereby welding the two together. Welding by this method is called projection welding. 
     FIG. 5 is a plan view of a presser ring according to the present invention (First Embodiment), and FIG. 6 is a view taken along arrow  6  of FIG.  5 . 
     Presser ring  40  is a formed product comprising pluralities (for example, 6) of second valley portions  41  . . . and second mount portions  42  . . . alternately provided by punching and bending a steel sheet, with presser piece portion  43  projected toward the center from each of the second mount portions  42 . The second valley portions  41  . . . are provided with bolt holes  44  . . . . The minimum inside diameter D 2  is smaller than the diameter of the flange portion  21  (See FIG. 2) of pump unit  20 , and inside diameter D 3  between second valley portions  41 ,  41  is slightly greater than the diameter of flange portion  21  (See FIG.  2 ). 
     While six presser piece portions  43  are intermittently shown in FIG. 5, presser piece portions  43  . . . may be contiguous with each other so that presser ring  40  has a uniform inside diameter D 2 . However, when presser piece portions  43  are intermittently provided as shown in FIG. 5, it is possible to prevent the generation of wrinkles at the time of press working. Thus, press forming is facilitated, and production cost can be reduced. 
     The purpose of the fixed side ring and the presser ring according to First Embodiment will be described referring to FIGS. 7 to  9 . 
     FIG. 7 is a tank fitting procedure of a fuel pump according to the present invention (First Embodiment). Gasket  35  is positioned on an edge of pump insertion hole  12  of fuel tank  10 , but fixed side ring  30  is preliminarily fitted to fuel tank  10  at a position surrounding gasket  35 . A major part of pump unit  20  is inserted into fuel tank  10  through pump insertion hole  12  while placing flange portion  21  projected from pump unit  20  on gasket  35 . 
     Next, while the inside surface  45  (corresponding to the lower surface of the presser piece portions  43 ) of presser ring  40  is caused to face flange portion  21 , bolt hole  44  of presser ring  40  is fitted to bolt  31 . This causes the outside surface  46  of presser ring  40  to face fixed side ring  30 . 
     FIG. 8 is a view taken along arrow  8  of FIG. 7, and shows the condition where first valley portions  32 ,  32  of fixed side ring  30  are preliminarily welded to fuel tank  10 , and where second valley portion  41  of presser ring  40  faces first mount portion  33  of fixed side ring  30 . 
     FIG. 9 is a view showing the tank fitting structure for the fuel tank according to the present invention (First Embodiment), and shows the condition where the second valley portion  41  is brought into close contact with first mount portion  33  by fastening nut  50  onto bolt  31 . At this time, gasket  35  is appropriately collapsed by presser piece portion  43  of presser ring  40  through flange portion  21 , so that sealing performance of gasket  35  can be effectively achieved. 
     Here, it is important that even when nut  50  is tightened further, the collapsing amount of gasket  35  is not substantially changed. This is because second valley portion  41  is in contact with first mount portion  33 . Accordingly, when a further tightening of nut  50  is necessary for increasing the fastening force between fixed side ring  30  and presser ring  40 , the collapsing amount of gasket  35  is not affected by this further tightening force. 
     The collapsing amount of gasket  35  has an optimum value determined according to the material and cross-sectional shape. If the collapsing amount is deviated from the optimum value by more than a certain value, reduction of the sealing performance or breakage of the gasket will occur. In view of this, according to the present invention, the collapsing amount of gasket  35  can be maintained at a fixed level, so that a good sealing performance can be maintained. Since the collapsing amount of gasket  35  is fixed, the compressing force acting on flange portion  21  is also fixed. Since there is no possibility that the compressing force will be abruptly increased, flange portion  21  can be made from a resin. 
     In addition, presser ring  40  can be securely fastened to fixed side ring  30  by bolt  31  and nut  50  as fastening members, and, as such, there is no possibility that the fastening members will become loosened, even under conditions with heavy vibrations. Therefore, the fitting structure according to the present invention is suitable for a tank fitting structure for a fuel pump in an autobicycle subject to receiving large vibrations. The structure is particularly suitable where pump unit  20  is inserted into fuel tank  10  from the lower side as shown in FIG.  1 . This fitting structure may also be applied to three- or four-wheel vehicles. 
     Another embodiment of the present invention will be described next. 
     FIG. 10 is a perspective view of a fixed side ring and a presser ring according to Second Embodiment of the present invention. Fixed side ring  30  is a steel plate ring with bolts  31  . . . fitted thereto in an upward pose. Presser ring  40  is a steel plate ring having bolt holes  44  . . . and presser piece portion  43 . 
     FIGS.  11 ( a ) and  11 ( b ) are views of a tank fitting procedure for a fuel tank according to the present invention (Second Embodiment). 
     In FIG.  11 ( a ), gasket  35  is placed on an edge of pump insertion hole  12  provided in fuel tank  10 . Fixed side ring  30  is preliminarily fitted to fuel tank  10  at a position surrounding gasket  35 . A major part of pump unit  20  is inserted into fuel tank  10  through pump insertion hole  12  while placing flange portion  21  projected from pump unit  20  on the gasket  35 . 
     Next, bolt hole  44  of presser ring  40  is fitted to bolt  31 . This causes inside surface  45  (corresponding to the lower surface of the presser piece portion  43 ) of presser ring  40  to face flange portion  21 , and causes outside surface  46  of presser ring  40  to face fixed side ring  30 . 
     In FIG.  11 ( b ), nut  50  is fastened onto bolt  31 , whereby presser ring  40  is brought into close contact with fixed side ring  30 . As a result, gasket  35  is appropriately collapsed by presser ring  40  through flange portion  21 , causing the sealing performance of gasket  35  to be effectively achieved. 
     FIG. 12 is a perspective view of a fixed side ring and a presser ring according to Third Embodiment of the present invention. Fixed side ring  30  is a steel plate ring provided with legs  37  . . . , and bolts  31  . . . fitted thereto in an upward pose. Presser ring  40  is a steel plate ring having bolt holes  44  . . . and a presser piece portion  43 . Since fixed side ring  30  is provided with legs  37  . . . , reductions in material thickness and weight of fixed side ring  30  can be achieved. 
     FIGS.  13 ( a ) and  13 ( b ) are views showing the tank fitting procedure of a fuel pump according to the present invention (Third Embodiment). 
     In FIG.  13 ( a ), gasket  35  is put on an edge of pump insertion hole  12  provided in fuel tank  10 , and fixed side ring  30  is preliminarily fitted to fuel tank  10  at a position so as to surround gasket  35 . A major part of pump unit  20  is inserted into fuel tank  10  through pump insertion hole  12  while placing flange portion  21  projected from pump unit  20  on gasket  35 . 
     Next, bolt hole  44  of presser ring  40  is fitted to bolt  31  while causing the inside surface  45  (corresponding to the lower surface of the presser piece portion  43 ) of presser ring  40  to face flange portion  21 . This causes outside surface  46  of presser ring  40  to face fixed side ring  30 . 
     In FIG.  13 ( b ), nut  50  is fastened onto bolt  31 , whereby the presser ring  40  is brought into close contact with fixed side ring  30 . As a result, gasket  35  is appropriately collapsed by presser ring  40  through flange portion  21 , so that sealing performance of gasket  35  can be achieved. 
     The fastening member exemplified by bolt  31  and nut  50  may be any member of any kind that can display an action of pressing the presser ring against the fixed side ring. 
     The fitting structure according to the present invention can be applied to any of a system in which the pump unit is inserted into the fuel tank downwards from the upper side, a system in which the pump unit is inserted into the fuel tank upwards from the lower side, and a system in which the pump unit is inserted into the fuel tank in a lateral direction. 
     The present invention, with the above constitution, displays the following effects. 
     According to the present invention, a flange portion is placed on a gasket positioned on an edge of a pump insertion hole of a fuel tank. The gasket is collapsed by pressing the flange portion by the inside surface of a presser ring, wherein the collapsing amount is determined by a position at which presser ring comes into contact with a fixed side ring. Thus, even if the tightening force to the fastening member is increased so as to further tighten the presser ring to the fixed side ring, the collapsing amount of the gasket is not changed. The compressing force exerted on the flange portion coincides with the springy force of the gasket. Thus, the springy force of the gasket is fixed, such that a compressing force more than a certain level cannot be exerted on the flange portion. As such, it is possible to prevent the generation of creep deformation to the flange, even when the flange portion is made from a resin. Moreover, sealing performance is stabilized, and a good sealing performance can be achieved even under conditions of heavy vibrations. 
     The present invention also includes a fixed side ring formed having first valley portions and first mount portions alternately provided by bending a steel sheet. The first valley portions are connected to the fuel tank, and the first mount portions are used as receiving surfaces for the presser ring. The presser ring is formed to have second valley portions and second mount portions alternately provided by bending a steel sheet. The second valley portions are brought into contact with the first mount portions, and the flange portion of the pump unit is held by inside surfaces of the second mount portions. In order to bring the presser ring into close contact with the fixed side ring and to appropriately hold the flange portion by the presser ring, desired shapes are adjusted by bending a sheet. Since the fixed side ring and the presser ring are each made from a sheet plate, a reduction in weight of rings can be achieved. 
     In addition, the present invention includes a flange portion of the pump unit formed from a resin. As a result, a reduction in both the weight and the cost of the pump unit can be achieved. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.