Patent Publication Number: US-5427074-A

Title: Vented fuel module reservoir

Description:
FIELD OF THE INVENTION 
     A fuel reservoir in a main vehicle fuel tank with a power driven pump in the reservoir which receives fuel from a return line in the vehicle fuel system. 
     BACKGROUND OF THE INVENTION 
     In vehicle fuel systems, an electrically driven fuel pump is mounted in a fuel reservoir which, in turn, is located in the main vehicle fuel tank. The pump has an outlet leading to a fuel rail which distributes operating fuel to fuel injection units in a fuel rail at the engine. In some fuel systems, the pump has a capacity greater than that required by the engine and a pressure relief valve discharges over-capacity fuel to a return line which dumps into the reservoir. 
     Also, in some systems, the fuel pump has a main outlet directed to the engine and a diversion outlet directed to a jet pump at the base of the reservoir. The jet pump has a fuel tank inlet, independent of the main pump inlet, which, in connection with a venturi passage, moves fuel into the reservoir to maintain a supply of fuel in the reservoir, independent of fuel in the main tank of the vehicle. 
     Some systems have provided for over flow of fuel from the reservoir to the main tank. However, the reservoir fuel may be hot due to the return flow and it is not desirable that hot fuel reach the main tank. Also, it is desirable that the reservoir be closed at the top to create a back pressure on the jet pump and accordingly increase the pressure at the main fuel inlet to provide a force feed to the main pump. 
     SUMMARY OF THE INVENTION 
     A main fuel tank in an automotive vehicle contains a reservoir holding an electrically operated pump. The pump has a main fuel outlet at the top of the reservoir directing fuel to the vehicle engine, and a secondary outlet directing fuel under pressure to a jet pump which moves fuel from an inlet at the base of the reservoir to the interior of the reservoir. A fuel return passage from the fuel system dumps into the top of the reservoir. In some existing fuel systems, fuel in the reservoir is overflowed into the main tank. In the present invention, the reservoir is selectively closed to overflow by either a calibrated vent at the top or a float valve, which will close when the fuel level in the reservoir reaches the top of the reservoir. This closure will cause pressure from the jet pump to increase in the reservoir and essentially shut down the jet pump out flow. The increased pressure in the reservoir will act on fuel entering the main pump inlet and force feed fuel into the pump thereby increasing the efficiency of the system. 
     Another feature of the invention lies in the fact that hot fuel returning to the reservoir will not heat the fuel in the main tank. Still another feature is the reduction in fuel flow through the primary filter at the base of the reservoir. 
     It is therefore an object of the invention to provide a top closure in a fuel tank reservoir which will prevent overflow of hot fuel into a main tank. Another object is a scheduled closure of the reservoir dependent on fuel level to develop back pressure against a jet pump outlet thereby stemming flow into the reservoir and effecting a pressure build-up to increase fuel inlet flow to the main pump inlet. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above recited objects and features of the invention as well as other objects, features and advantages will be apparent in the following detailed description of the preferred embodiments and best mode, appended claims and accompanying drawings in which: 
     FIG. 1 is a sectional view of an in-tank reservoir with the included fuel pump; 
     FIG. 2 is a fragmental view of the top of the reservoir with an optional control vent; and 
     FIG. 3 is a sectional view of the lower end of a reservoir showing the jet pump. 
    
    
     DETAILED DESCRIPTION 
     In FIG. 1 of the drawings, the main fuel tank of a vehicle is exemplified by a bottom wall 20 and a top wall 22, the top wall having an opening 24 defined by a depressed annular flange 26. A sealing closure cover 30 has a peripheral flange 32 resting in a sealing ring 34. 
     An in-tank fuel reservoir 40 has a narrowed lower end terminating in a boss 42 which is received in a collar 44 in the top of a sock filter 46 resting on the tank bottom 20. The boss 42 has axially spaced annular ribs 48 and 50 between which is a foot valve plate 52. The opening in rib 48 provides a fuel inlet 49. An annular seal 54 fits into the top of the boss 42 and rests against the rib 50, and extending into this seal is a tube 56, the interior of which forms a chamber 58 (FIG. 3) open to the base 60 of an electrically driven pump 62 within the reservoir 40. The pump 62 may be an electrically powered turbine pump as described in a U.S. Pat. No. 5,257,916 (Nov. 2, 1993) to C. H. Tuckey. Extending into the pump base 60 is a venturi tube 64 (FIG. 3), the inner end terminating in chamber 58 and the outer end opening to the interior of the reservoir 40. As shown in FIG. 3, a pump outlet 65 has a jet port 66 which discharges into the inner end of venturi tube 64. FIG. 3 shows a section of the pump base 60 enlarged from the depiction in FIG. 1. The function of the jet pump will be later described. 
     As shown in FIGS. 1 and 3, an annular fuel filter ring 70 is sealed at inner and outer peripheries by collars 72 and 74 respectively. With reference to FIG. 1, a main pump fuel inlet is illustrated at 80 and fuel from the interior of reservoir 40 will flow through the filter 70 and into the inlet 80. 
     Turning now to the top of the pump and reservoir, the pump has electrical connections 82 and 84, and a pump outlet tube 86 has a sealed relationship to a hollow outlet conduit 88 depending from a top cover plate 90 on reservoir 40. A conventional wiring system (not shown) initiates operation of the pump when the vehicle ignition system is turned on. Conduit 88 terminates above cover plate 80 in a nipple connection 92 which is attached by a flexible coupling 94 to a fuel passage 96 projecting through the cover 30 and leading to a vehicle engine (not shown). 
     The top cover plate 90 has also a depending passage 97 and an upstanding passage 98 forming a through passage 100. A flexible coupling 102 connects passage 100 to a system conduit 104 which passes through cover 30. The system conduit 104 is a fuel return passage in a fuel system in which fuel under pressure from the pump delivers fuel to an engine but a pressure regulator valve in the outlet line by-passes fuel above a predetermined pressure back to the reservoir. This is described in U.S. Pat. No. 4,747,388 (May 31, 1988) issued to C. H. Tuckey. At the end of the depending passage 97 is clamped a one-way duckbill valve 110 which admits return fuel to the interior of the reservoir but blocks any outward flow. 
     The present invention is directed to venting at the top of the reservoir. It will be appreciated that, if fuel is to enter the reservoir, there must be a means of venting air above the fuel. In FIG. 1, an upstanding valve chamber 120 is provided with a valve seat opening 122. A valve stem 124 has a loose fit in the chamber 120 and is supported on a float block 126, which is retained in a lowest position by a short shelf 130. Accordingly, when the reservoir is filling, air can escape around the valve stem 124. When the liquid fuel level reaches the top, the float will raise the valve stem so that the tapered end will close the valve opening 122 and pressure will build up in the reservoir. 
     In FIG. 2, a vent is illustrated in the form of a small calibrated port 140. This port will vent air from the reservoir while it is filling. When liquid reaches the port it will not pass readily through the port and pressure will build up in the reservoir. 
     OPERATION OF THE SYSTEM 
     Assuming that there is fuel in the reservoir 40, a start-up of the pump 62 will draw fuel through the filter 70 into the main pump inlet 80 and out of the main outlet 86 (FIG. 1). At the same time, a secondary diversionary pump outlet 65 (FIG. 3) delivers fuel under pressure to the jet orifice 66 and into the venturi passage 64. The drop in pressure due to the venturi action will pull fuel from the main fuel tank through the fuel inlet 49 into the chamber 58 where it will be discharged through the venturi to the interior of the reservoir. The reservoir will be receiving liquid fuel, and air will be vented through port 122 until the fuel level reaches the float 126 illustrated in FIG. 1. The lifting of the float will cause the valve stem 124 to close the port 122. This will cause pressure in the reservoir to build up and create back pressure at the outlet end of the venturi tube, thus effectively stopping the entrance of fuel into the reservoir. This back pressure in the reservoir will also cause a force feed of fuel from the reservoir into the main pump inlet 80 and thus increase the efficiency of the main pump delivering fuel to a vehicle engine. 
     In FIG. 2, the valve 124, shown in FIG. 1, is eliminated and the calibrated vent 140 allows air to escape as the reservoir fills. When liquid fuel reaches the vent 140, the additional viscosity of the fuel slows any significant escape of fuel through the vent and pressure builds up in the reservoir to create back pressure in the reservoir and a consequent reduction of fuel exiting the venturi tube. Again, this pressure build up will increase pressure on fuel entering the main pump inlet and increase the efficiency of the main fuel pump. 
     The fuel return passage 104 will direct excess fuel at a low pressure from a pressure regulator (not shown) into the reservoir through duck bill valve 110 which is a one-way valve into the reservoir.