Patent Publication Number: US-6216671-B1

Title: Modular fuel reservoir for motor vehicle

Description:
TECHNICAL FIELD 
     This invention relates to a modular fuel reservoir in a motor vehicle fuel tank. 
     BACKGROUND OF THE INVENTION 
     A typical motor vehicle fuel system includes an element commonly referred to as a “modular fuel reservoir” (MFR) in a fuel tank of the motor vehicle. The MFR includes a tank cover, a cup-shaped plastic reservoir, a plurality of struts on the tank cover slidably connected to the reservoir, and a spring urging relative separation between the tank cover and the reservoir. The MFR is inserted into the fuel tank through an access port in the top of the fuel tank which is sealed closed by the tank cover. The spring biases the reservoir against the bottom of the fuel tank. A plastic retainer on the top of the plastic reservoir supports a fuel pump including an electric motor and a pump. The electric motor of the fuel pump is turned on and off through a wiring harness of the motor vehicle. When the electric motor is on, the pump pumps fuel at elevated pressure from the reservoir through a high pressure loop which includes a fuel rail of a fuel injection system of the motor vehicle and a fuel pressure regulator on the reservoir or on the retainer of the MFR. The pressure regulator releases fuel from the high pressure loop to the reservoir through a return loop and commonly includes a metal housing which is electrically insulated by the plastic reservoir or the plastic retainer and which, therefore, becomes a capacitor-like electrical storage device as ions stripped away from the fuel collect on the metal housing. To maintain the metal housing of the pressure regulator at the same potential as the negative terminal of the motor vehicle&#39;s battery, it is known to “ground” the metal housing through a terminal clip clipped onto the metal housing and a conductor attached to the terminal clip and spliced into a negative conductor of the wiring harness of the motor vehicle. Such extra wires and terminal clips, and the installation thereof, however, contribute to the manufacturing expense of the MFR. 
     SUMMARY OF THE INVENTION 
     This invention is a new and improved modular fuel reservoir (MFR) including a cup-shaped plastic reservoir, a tank cover, a plurality of struts on the tank cover slidably connected to the reservoir, a spring urging relative separation between the tank cover and the reservoir, and a pressure regulator supported on the reservoir. A fuel pump is supported in a tubular chamber of a retainer on top of the plastic reservoir and includes an exposed metal shell bearing against a wall of the tubular chamber and an electric motor turned on and off through a positive contact terminal and a negative contact terminal on a plastic end housing of the fuel pump. The retainer is made of an electrically conductive polymer having a surface resistivity less than or equal to 1×10 3  Ohms and/or a volumetric resistivity less than or equal to 600 Ohms/cm 3  as measured per ASTM D257 or equivalent test method and includes an integral resilient fin self-biased against a metal housing of the pressure regulator. Ions stripped from the fuel and collected on the metal housing of the pressure regulator are conducted to the negative terminal on the end housing of the fuel pump through the electrically conductive retainer, the exposed metal shell of the fuel pump, and an internal conductor in the fuel pump between the metal shell and the negative terminal. The wall of the tubular chamber of the electrically conductive retainer constitutes a shield around the fuel pump which reduces radiated electrical emissions attributable to commutation in the electric motor of the fuel pump. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of a modular fuel reservoir according to this invention in a motor vehicle fuel tank; 
     FIG. 2 is an exploded perspective view of the modular fuel reservoir according to this invention; and 
     FIG. 3 is a fragmentary sectional view taken generally along the plane indicated by lines  3 — 3  in FIG.  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A seen best in FIGS. 1-2, a modular fuel reservoir (MFR)  10  according to this invention is disposed in a motor vehicle fuel tank  12  and includes a cup-shaped plastic reservoir  14 , a tank cover  16 , a plurality of vertical struts  18  on the tank cover slidably connected to the reservoir, and a spring  20  urging relative separation between the tank cover and the reservoir. The tank cover  16  seals closed an access port  22  in a top  24  of the fuel tank through which the MFR is inserted into the tank. The spring  20  biases the reservoir  14  against a bottom  26  of the fuel tank. A discharge fluid connector  28  and a return fluid connector  30  on the tank cover  16  are linked by external fluid conduits, not shown, to a fuel rail of a fuel injection system of the motor vehicle. A vapor connector  32  on the tank cover is linked by an external conduit, not shown, to a vapor storage device, not shown. 
     A cylindrical wall  34  of the reservoir  14  is closed by a bottom  36 , open at a top edge  38  thereof, and flattened on a side  40 . The reservoir has an integral vertical return tube  42  and an integral vertical fill tube  44  each open through the bottom  36  of the reservoir. A jet pump  46  below the bottom of the reservoir has an orifice, not shown, aimed at the fill tube  44  and a motive fluid inlet  48  connected to the return tube  42 . 
     A fluid pressure regulator  50 , FIGS. 2-3, of the MFR  10  includes a metal housing  52 , an internal flexible diaphragm  54  dividing the metal housing into a pressure chamber  56  and a spring chamber  58 , a valve element  60  on the flexible diaphragm, and a spring  62  in the spring chamber biasing the valve element  60  against the bottom of the metal housing  52  over a passage  64  in a stem of the metal housing. The metal housing  52  is seated in a plastic support  66  on top of the vertical return tube  42  on the reservoir and cooperates with the support in defining an annular chamber  68  below the metal housing in fluid communication with the pressure chamber  56  through orifices, not shown, in the metal housing. The pressure chamber  56  communicates with the motive fluid inlet  48  of the jet pump  46  through the passage  64  in the stem of the metal housing and through the return tube  42 . Dislodgment of the metal housing  52  from the plastic support  66  is prevented by a metal clip  70 . The annular chamber  68  communicates with the return fluid connector  30  on the tank cover through a flexible plastic hose  72 . The spring chamber  58  is exposed to the pressure prevailing in the fuel tank through an aperture  74  in the metal housing  52 . 
     A molded plastic retainer  76  of the MFR  10  includes a vertical side wall  78  matching the shape of the cylindrical wall  34  of the reservoir  14 , a vertical tubular chamber  80 , and a vertical mounting pad  82 . The retainer  76  seats on and covers the reservoir  14  at the top edge  38  of the cylindrical wall  34  with the pressure regulator support  66  separated from the retainer by a clearance aperture  84  in the retainer. Dislodgment of the retainer  76  from the reservoir  14  is prevented by a plurality of barbs  86 , FIG. 3, on the retainer which resiliently snap into sockets in the reservoir. A fuel level transducer  88  is mounted on the vertical mounting pad  82  and connected to a wiring harness, not shown, of the motor vehicle. Importantly, the retainer  76  is molded from an electrically conductive material such as Celcon EC90PLUS, an acetal copolymer available commercially from Ticona, having a surface resistivity less than or equal to 1×10 3  Ohms and/or a volumetric resistivity less than or equal to 600 Ohms/cm 3  as measured per ASTM D257 or equivalent test method. 
     A fuel pump  90  of the MFR  10  includes an exposed tubular shell  92  made of an electrically conductive material, e.g. steel or aluminum, an end housing  94  made of an electrically non-conductive material, e.g. plastic, closing an end of the metal shell, and an electric motor  96  in the metal shell. The electric motor  96  includes an armature  98  rotatable about a longitudinal centerline of the fuel pump and connected to an impeller, not shown, of a schematically represented pump  100  at the other end of the shell  92  from the end housing  94 . A positive contact terminal, not shown, of the electric motor  96  on the end housing  94  is connected to the wiring harness of the motor vehicle through a positive conductor  102  between the fuel pump and the tank cover  16 . A negative contact terminal  104  of the electric motor  96  on the end housing  94  is electrically insulated from the positive contact terminal and connected to the wiring harness of the motor vehicle through a negative conductor  106  between the fuel pump and the tank cover  16 . The negative contact terminal  104  is in electrical communication with the metal shell  92  of the fuel pump through a schematically represented internal conductor  108 , FIG. 3, in the fuel pump. 
     The fuel pump  90  is supported on the retainer  76  in the tubular chamber  80  thereof with the wall of tubular chamber surrounding and bearing directly against the metal shell of the fuel pump and establishing an electrically conductive interface between the metal shell the retainer. An inlet, not shown, of the pump  100  is exposed to the plastic reservoir  14  through a filter  110 , FIG. 2, outside of the tubular chamber  80 . A resiliently flexible, integral contact fin  112  on the retainer  76  is self-biased against the metal housing  52  of the pressure regulator to establish an electrically conductive interface between the metal housing and the retainer. The metal clip  70  securing the pressure regulator to the support  66  may also function as an electrical conductor between the metal housing  52  and the retainer  76 . A discharge passage  114  on the end housing  94  of the fuel pump is connected to the discharge connector  28  on the tank cover  16  through a flexible plastic hose  116 . 
     When the electric motor  96  of the fuel pump  90  is on, the armature  98  of the electric motor rotates the aforesaid pump impeller to pump fuel from the reservoir  14  to the high pressure loop through the discharge passage  114 , the flexible hose  116 , and the discharge connector  28  on the tank cover. Fuel in the high pressure loop circulates back to the pressure chamber  56  of the pressure regulator  50  through the return fluid connector  30  on the tank cover, the flexible hose  72 , and the annular chamber  68  below the metal housing  52  of the pressure regulator. When the pressure force on the flexible diaphragm  54  exceeds the thrust of the spring  62 , the valve element  60  separates from the bottom of the metal housing  52  to divert a fraction of the discharge of the fuel pump into the return tube  42  through the passage  64 . The diverted fuel in the return tube enters the motive fluid inlet  48  of the jet pump and is discharged into the fill tube  44  as a jet which aspirates fuel from the fuel tank into the reservoir  14  to maintain the reservoir filled with fuel until the fuel tank is completely depleted. 
     When fuel is flowing in the high pressure loop and the return loop, the metal housing  52 , which is electrically insulated by the plastic support  66 , constitutes a charging-storing element of the MFR as ions stripped from the fuel collect on the metal housing. The ions which thus collect on the metal housing are conducted to the negative terminal  104  on the end housing  94  of the fuel pump through the retainer  76  in contact with the metal housing at the fin  112 , the metal shell  92  of the fuel pump  90  in contact with the retainer at the wall of the tubular chamber  80 , and the internal conductor  108  in the fuel pump. Since the negative terminal  104  is “grounded”, i.e. connected to and maintained at the electrical potential of the negative terminal of a battery of the motor vehicle, through the aforesaid wiring harness, the ions which collect on the metal housing  52 , or on any other metal element in contact with the retainer  76 , are harmlessly conducted to the negative terminal of the battery without resort to external contact clips and wires characteristic of prior MFR&#39;s. In addition, because the wall of the tubular chamber  80  of the retainer  76  surrounds the electric motor  96  of the fuel pump and is likewise “grounded” through the metal shell  92  and the internal conductor  108 , the wall of the tubular chamber constitutes a shield which reduces radiated electrical emissions attributable to commutation in the electric motor  96  for improved reception and transmission of radio equipment on the motor vehicle.