Abstract:
In a fuel tank having an electric fuel pump therein, the fuel pump is connected to discharge into a venturi with a throat pressure tap line connected to the bottom of a vapor vent valve fed by spider tubes to the tank vapor dome areas. Venturi throat suction pumps liquid accumulated in the vent valve for discharge through the venturi into the tank. A one way valve prevents back flow in the throat pressure tap line to the vent valve. Float operated valves are provided on the ends of the spider tubes to restrict fluid flow to the vapor vent valve.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to venting fuel vapor from a tank to a storage device and particularly for controlling the emission of fuel vapor from a motor vehicle fuel tank during periods of engine operation, shutdown and during refueling.  
           [0002]    The invention particularly relates to current production passenger car and light truck vehicles which employ fuel injected engines with the injectors being electrically controlled and supplied fuel at a positive gauge pressure from an electric pump located in the fuel tank.  
           [0003]    In motor vehicle fuel tank vapor vent control systems a float operated vent valve is disposed in the tank and located within the vapor dome above the liquid level. The vent valve controls venting of the fuel vapor from the tank during refueling such that the vent outlet to the storage device is closed upon the fuel rising to a predetermined fill level. Also, it is necessary to prevent liquid fuel from entering the vent line to the storage device in the event of sloshing of liquid fuel in the tank during vehicle operation and to provide protection for closing the vent in the event of vehicle rollover to prevent escape of liquid fuel.  
           [0004]    Where a float operated fuel vapor vent valve is employed in the fuel tank it is usually located at the undersurface of the top wall of the tank; and, outrigger vent tubes are connected to the vent valve and the tubes extend to the extremities of the tank so that a vent is always located in the vapor dome to insure venting when the tank is tilted upon the vehicle encountering grades either during operation or when parked.  
           [0005]    In operation, it has been experienced that sloshing of the liquid fuel in the tank has caused liquid fuel to enter and be trapped in the vent valve and vapor vent lines and thereby prevent proper venting of vapor from the tank.  
           [0006]    It has therefore been desired to provide a way or means of draining liquid fuel from the fuel vapor vent valve and venting system in order to insure that fuel vapor can be vented to the storage device remotely connected to the tank for storing vapors.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    The present invention provides a unique and novel system and method for controlling the venting of fuel vapor from a tank with an electric fuel pump in the fuel tank for providing fuel at a positive pressure to the engine fuel injector system. The outlet of the fuel pump is connected to discharge fuel not only through a line to the injectors externally of the tank, but also to the inlet of a venturi disposed in the tank. A dynamic pressure tap at the throat of the venturi is connected via a conduit to the outlet of a one way drain valve provided in the bottom of a float operated vent valve for controlling draining of liquid fuel from the venting system. The outlet of the venturi discharges to the liquid fuel in the tank; and, the reduced pressure in the venturi throat effects aspiration of liquid fuel trapped in the drain valve. A one-way valve is provided in the conduit from the venturi throat to the valving chamber of the vent valve to prevent liquid fuel from entering the drain valve from the venturi throat tap in the event the venturi discharge becomes blocked and from the hydrostatic pressure of the fuel when the engine is shut down. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a pictorial schematic of the system of the present invention;  
         [0009]    [0009]FIG. 2 is a cross-section of the vapor vent valve of the system of FIG. 1;  
         [0010]    [0010]FIG. 3 is an enlarged cross-section of a portion of FIG. 2 showing the drain valve pilot in the open position;  
         [0011]    [0011]FIG. 4 is a view similar to FIG. 2 of another embodiment of the vent valve;  
         [0012]    [0012]FIG. 5 is a section view taken along section indicating lines  5 - 5  of FIG. 4;  
         [0013]    [0013]FIG. 6 is a cross-section of an alternate embodiment of the valve of FIG. 4;  
         [0014]    [0014]FIG. 7 is a top view of a float operated restrictor valve for the system of FIG. 1; and,  
         [0015]    [0015]FIG. 8 is a front elevation view with portions broken away of the restrictor valve of FIG. 7. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    Referring to FIG. 1, the system of the present invention is indicated generally at  10  and includes a fuel tank  12  having a filler tube  14  attached thereto for refueling from a nozzle (not shown) and with a fuel vapor vent valve indicated generally at  16  disposed within the tank and adjacent the undersurface of the upper wall  18  of the tank  12 . The vent valve  16  has an outlet or connector tube  20  extending through the upper wall  18  of the tank  12  and outlet  20  is connected by conduit  22  which may be a flexible hose to the inlet of a storage device  24  such as a canister filled with granulated carbon material. The storage device  24  has its inlet  26  connected via a conduit  28  to the inlet of an electrically operated valve  30  which has its outlet connected through a conduit  32  to the engine air inlet at  34 . The valve  30  may be controlled by an electronic control unit  36  which may be part of the engine control system (not shown).  
         [0017]    An electrically operated fuel pump  38  is disposed in the tank and immersed in the liquid as indicated by the reference character L and the pump  38  has the discharge side thereof connected through conduit  40  through the wall of the fuel tank as indicated by the fitting  42  in the upper wall  18  and through external conduit  44  to the engine fuel injectors  46 . The discharge side of the fuel pump is also connected to the inlet of a venturi  48  disposed in the tank  12 , with the outlet thereof discharging to the interior of the tank. The throat region  50  of the venturi  48  is tapped and connected through conduit  52 , which may be a flexible hose, to the outlet of a one-way drain valve  54  which will be described hereinafter in greater detail. In the presently preferred practice of the invention, the venturi throat is sized to create a dynamic depression (vacuum) of about 20-25 inches (50.8-63.5 cm) of H 2 O column; however, it will be understood that for exceptionally large or small fuel tank systems more or less vacuum at the venturi respectively may be required.  
         [0018]    The vent valve  16  has at least one and preferably a plurality of vapor vent lines  56  each connected at one end thereof to the valve  16 , as will hereinafter be described, with the distal end of each of the tubes  56  extending to the extremities of the vapor dome in the tank above the fuel level denoted by reference character L. Each of the vent lines  56  has a float operated restrictor valve  58  provided thereon as will hereinafter be described in greater detail.  
         [0019]    Referring to FIG. 2, the vapor vent valve  16  has a body  60  defining a valving chamber  62  therein and has liquid fuel entry ports  64  formed in the body to permit the liquid fuel in the tank to enter the valving chamber  62 . The vapor vent tubes  56  have one end thereof connected to the valve body  60 . The valving chamber  62  includes a cage  66  which retains therein a float  68  which has a valve member  70  in the form of a flexible strip attached to the upper surface of the float  68 . In the presently preferred practice, the valving member  70  is formed of elastomeric material and is engaged over a projection  72  formed on the upper surface of the float  68  for attaching one end of the strip to the float  68 . The end of member  70  opposite the one end is attached to the body  60  by any convenient technique; as, for example stretch or snap engagement over mounting projections.  
         [0020]    The lower end of the float  68  has a camming surface  74  formed thereon with an inertial mass  76  disposed therewith and captured by the lower end of the float. A second or lower float  78  is disposed within the cage  66  which also has a similar camming surface  80  formed on the upper end thereof which cooperates with the cam surface  74  to cause the float  68  to move upwards upon tilting of the tank and the contact of the inertial mass  76  with the cam surfaces  74 ,  80 . The upward movement of the float  68  either by the rising level of the liquid in the tank, or by contact of the inertial mass against the cam surfaces  74 ,  80  moves the valve member  70  into contact with valve seat  82  formed on the end of the conduit  20  entering the valving chamber  62 . Alternatively valve member  70  could be spring biased.  
         [0021]    A drain valve float  84  is disposed within the body  60  at the lower end thereof below cage  66 ; and, drain valve float  84  has an annular valve seat  86  formed on the lower surface thereof. A flexible valving member  88  is attached about the lower end of the float valve member  84 ; and, the flexible valve member  88  has a pilot hole  90  formed centrally therein. In the presently preferred practice of the invention, the valve member  88  is formed of elastomeric material.  
         [0022]    The tube or hose  52  from the venturi throat  50  has its upper end connected to a suitable fitting  53  extending through the bottom of the valve housing  60  and has an annular valve seat  92  formed thereabout on the interior of the valve body  60 . The elastomeric valve member  88 , upon downward movement of drain valve float  84  contacts the valve seat  92  with its lower surface; and, the valve seat  86  on the drain valve float  84  contacts the upper surface of the elastomeric valve member  88  to seal about the pilot hole  90 .  
         [0023]    Referring to FIG. 3, the drain valve float  84  is shown slightly lifted from the position of FIG. 2 wherein the pilot hole  90  is closed by the valve seat  86  to a position where valve seat  86  is raised from the upper surface of elastomeric valve member  88  to open the pilot hole  90  and permit flow therethrough to the conduit  52 . The limited flow through pilot hole  90  thus reduces the pressure forces acting on the valve member  88  caused by the reduced pressure in the conduit  52  from the venturi throat tap and permits the drain valve float member  84  to rise further with increasing fuel level in the valve body  60 , thereby lifting the lower surface of valve member  88  from the valve seat  92  to permit full drain flow.  
         [0024]    Referring to FIG. 4, an alternate embodiment of the vent valve is illustrated generally at  100  and is connected to vent outlet  20 ′ and vent lines  56 ′ in a manner similar to the valve  16  of FIG. 2. The valve assembly  100  includes a float  68 ′ and flexible strip valve member  70 ′ which seals about an annular valve seat  82 ′ formed in the interior of the valving chamber  62 ′ formed inside the valve body  60 ′ and functions in a manner identical to that of the float operated valve in the embodiment of FIG. 2.  
         [0025]    The valve  100  includes a drain valve assembly indicated generally at  102  which includes an auxiliary valve housing  104  formed on the bottom of the vent valve housing  60 ′ and which has attached thereto by any suitable technique the upper end of a conduit  52 ′ which has its other end connected to the venturi throat  50 .  
         [0026]    Valve housing  104  forms a valving chamber  106  which communicates with a drain hole  108  formed in the bottom of the body  60 ′; and, an annular valve seat  110  is formed about the opening in the chamber  104  to the interior of the tube  53 ′ connecting to the venturi tap. A moveable valve member  112  preferably having a generally flat disk configuration is disposed in the chamber  106  for movement with respect to the valve seat  110  and the undersurface of the valve body  60 ′ in the region around the drain hole  108 .  
         [0027]    Referring to FIG. 5, the valve seat  110  has a plurality of grooves  114  formed therein to form a castellated surface to prevent the valve member  112  from completely closing the interior  111  of the tube  53 ′.  
         [0028]    In the event of positive pressurization in the tube  53 ′, the force of the fluid raises valve member  112  to close drain hole  108  to prevent the pump from filling the interior of the body  60 ′.  
         [0029]    Referring to FIG. 6, an alternate embodiment of the drain valve is indicated generally at  116  and has an auxiliary valve housing  1   18  formed on the bottom of the main valve housing  60 ″ and forms a valve chamber  106 ′ which communicates with the interior  111 ′ of tube  52 ″ which connects to the venturi throat  50 . A drain hole  108 ′ is formed in the bottom of the valve housing  60 ″. A button or rivet type poppet valve member is moveably received in the drain hole  108 ′. In the presently preferred practice the valve member comprises a mushroom-shaped member indicated generally at  120  which has a plurality of radial grooves  122  formed in the upper head or flanged portion  123  thereof disposed on the interior of the housing  60 ″. The lower head portion of valve member  120  disposed in the chamber  106 ′ comprises an enlarged flanged portion  124  which extends outwardly over the drain hole  108 ′. Upper head  123  and lower head  124  or connected by a stem  125  passing through drain hole  108 . It will be understood that stem  125  has a diameter or transverse dimension significantly less than the diameter of drain hole  108 ″ to permit liquid fuel passing through grooves  122  to drain around stem  125  and through drain hole  125 .  
         [0030]    As shown in FIG. 6, the grooves or slots  122  permit liquid in the interior of the body  60 ″ to drain through drain hole  108 ′. In the event that the venturi discharge becomes blocked or engine is shut down and positive pressure from the pump or hydrostatic head is experienced in the throat and chamber  108 ′, the flanged portion  124  is raised in a vertical direction from the position shown in FIG. 6 and is forced against the undersurface of the body  60 ″ and seals about the drain hole preventing liquid from entering the body  60 ″. If desired valve  120  may be biased upwardly by the elastomer or a separate spring.  
         [0031]    Referring to FIGS. 7 and 8, the restrictor valve  58  is shown in enlarged, detail wherein the region proximate end of the tube  56  has diametrally opposed apertures  126 ,  128  formed therein, each of which has received pivotally therein a trunnion  130 ,  132  respectively, the trunnions extending inwardly respectively from a pair of parallel arms  134 ,  136  respectively extending along the sides of tube  56  and beyond the end thereof with the ends of the arms  134 ,  136  attached to the float  138  on opposite sides thereof. Float  138  has a lug or projection  140  extending horizontally outwardly therefrom and into the end of the tube  56 . The edge of the float  142  adjacent the end of the tube  56  is closely spaced therefrom such that when the float is in the fully upward position, as shown in solid outline in FIGS. 7 and 8, the edge of the float severely restricts the flow of liquid from the tank into the tube as is shown clearly in FIG. 8. Upward movement of the float is limited by contact of the pin  140  with the undersurface of the upper portion of the wall of the tube  56 .  
         [0032]    Referring to FIG. 8, the float  138  is shown in dashed outline in its lowered position caused by a decrease in the liquid level L in the tank; and, downward movement of the float  138  is limited by contact of the pin  140  with the lower portion of the inner surface of the wall of the tube  56 . In the position shown in dashed outline, the edge  142  of the float is moved to a position so as to further open the end of tube  56  and permit greater fluid entry therein. In the present practice of the invention, the float  138  and arms  134 ,  136  and trunnions  130 , 132  are formed integrally as a one-piece unit such as for example by molding from engineered resinous material.  
         [0033]    The present invention thus provides for utilizing a reduced dynamic pressure or suction created by connecting the output of a submersed fuel pump through a venturi and tapping the venturi throat to a one way drain valve provided in the bottom of a float operated fuel vapor vent valve, provided in the fuel tank. The one way valve prevents any fluid under positive pressure from the venturi from entering the vapor vent valve.  
         [0034]    Although the invention has hereinabove been described with respect to the illustrated embodiments, it will be understood that the invention is capable of modification and variation and is limited only by the following claims.