Abstract:
A fuel storage system for a transportation or recreational vehicle has a fuel tank that carries a vapor assembly that seeks out vapor pockets and controllably removes fuel vapor from the tank without releasing hydrocarbons to the surrounding environment. Preferably, a vent manifold attaches to a flange that sealably covers an access hole of the tank. At least one flexible tentacle extends from the manifold in the tank to a respective vapor vent valve that floats upon the surface of fuel at a vapor dome. When freely floating, the vent valve is open thus communicates the vapor dome through the tentacle and preferably with a filtering carbon canister. As fuel surface levels change or the vehicle tilts, changing the vapor dome size or location in the tank, the floating vapor vent valve is free to move generally with the vapor dome and as permitted by the flexibility of the trailing tentacle. With tank orientations where the vapor vent valve falls below the surface of fuel, the vent valve automatically closes to prevent flooding of the respective tentacle and remote vapor canister.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a fuel storage system for a vehicle and more particularly to a fuel level vapor assembly of the fuel storage system.  
       BACKGROUND OF THE INVENTION  
       [0002]     Environmental concerns and governmental regulations require reduced emissions of volatile hydrocarbon fuel vapors into the atmosphere. One source of hydrocarbon fuel vapors is the fuel tanks of vehicles using gasoline or other hydrocarbon fuels with high volatility. Fuel vapor can escape to the atmosphere during the filling of the tanks and usually even after the tanks are filled.  
         [0003]     The use of an onboard vapor recovery system to remove excess fuel vapor from the fuel tank is one solution to the problem. Typically, a canister with activated charcoal therein receives fuel vapors through a vent valve mounted in the top of the fuel tank or within a flange of an in-tank fuel pump module for communication with a vapor dome in the tank. The vent valve is usually responsive to the level of fuel in the tank and will generally stay open provided the fuel level within the tank is sufficiently low. When open, fuel vapors flow freely from the fuel tank into the canister. Some vent valves are referred to as fill-limit vent valves or FLVV, because when the fuel tank of the vehicle is being refueled by a automatic shut-off fuel pump nozzle, the fuel level rises until a predetermined maximum level is reached. This maximum level generally preserves a minimum size vapor dome above the fuel.  
         [0004]     For refueling purposes of the fuel tank, a filler tube generally extends substantially downward to the tank and communicates directly with the tank at an opening. When following common government regulatory requirements that a vehicle must generally sit within about a plus or minus three degree angle to a horizontal plane, the filler tube opening at the tank is commonly located above the maximum fuel level and communicates with the minimum size vapor dome. This relationship assures that when nearing maximum fuel level and before the FLVV closes, a backpressure is not created in the filler tube at the opening, because such a backpressure would cause liquid fuel to gurgle or backup in the filler tube. Such a backup could cause the automatic shut-off fuel pump nozzle to prematurely shut-off before maximum fuel level is reached.  
         [0005]     During refueling of the vehicle and as the fuel level rises to a predetermined maximum level, a float of the vent valve rises with the fuel level to close the valve thus preventing liquid fuel from flowing through the vent valve and into the vapor receiving canister. Two such vent valves are disclosed in U.S. Pat. Nos. 6,145,532 and 6,848,463, and incorporated herein by reference in their entirety.  
         [0006]     Known vapor vent valves are typically mounted rigidly to the fuel tank at substantially the highest elevation to vent away most of the fuel vapor to the canister during refueling when the tank or vehicle is generally at a horizontal position to thereby control the minimum volume of the vapor dome. Regardless of whether the combustion engine is running, the open vent valves allow air and fuel vapor, but not liquid fuel, to flow from the tank and to the canister. When the combustion engine is running and fuel is being displaced from the tank, a one-way venting check valve preferably vents fresh air to the enlarging vapor dome in the tank while air and fuel vapor may continue to flow through the open vent valve(s), then through the canister and to the running engine to maintain substantially constant pressure in the fuel tank.  
         [0007]     Unfortunately, if the tank has two vapor domes or two high elevation points, known fuel storage systems having only one fixed vent valve can vent only one of the vapor domes. Because the vapor in the other vapor dome can not be displaced with fuel, the storage capacity of the tank is undesirably limited. Moreover, if the vehicle is traveling down or up a steep embankment, the tank is no longer generally horizontal and a substantially full tank of fuel could submerge the float of the fixed vent valve thus closing the vent valve while the engine is operating. With the vent valve closed and the engine consuming fuel or with the fuel being heated by a return loop fuel system, constant internal pressure of the tank is disrupted and engine performance may be degraded.  
         [0008]     Moreover, for off-road vehicle applications that require gravity fed manual refueling operations (i.e. from a portable five gallon gas can), the vehicle may not be sitting within a plus or minus three degree angle from a horizontal plane as required for automatic shut-off pump refueling operations. Instead, the vehicle could be tilted at a much greater angle causing the FLVV to close considerably before the vapor dome is reduced to a minimum volume. Although premature closure of the FLVV on its own may not pose a filler tube backup problem during a manual refueling operation because supply fuel typically flows through the filler tube at a much slower rate, trapped air and fuel vapor in the tank can greatly reduce it&#39;s liquid fuel storage capacity when the tank is orientated at excessive angles away from the horizontal plane. That is, with the FLVV closed, and once the filler tube opening at the tank is immersed in liquid fuel, and air and vapor remaining in the tank is trapped. The volume of this trapped air and vapor may greatly exceed the minimum required volume of the vapor dome.  
       SUMMARY OF THE INVENTION  
       [0009]     A fuel storage system for a passenger, transportation or recreational vehicle has an on-board fuel tank that carries a self-referencing vapor assembly for seeking out vapor pockets and controllably removing fuel vapor from the tank. Preferably, a vent manifold attaches to a flange that sealably covers an access hole of the tank. At least one flexible vapor line extends from the manifold in the tank to a vapor vent valve that floats upon the surface of fuel. When floating upon the fuel surface, the vapor vent valve is open to communicate the vapor dome through the vapor line and preferably with a carbon canister for hydrocarbon storage. As fuel surface levels change or the vehicle tilts, changing the vapor dome size or location in the tank, the floating vapor vent valve is sufficiently free to move generally with the vapor dome and as permitted by the flexibility of the vapor line. In tank orientations where the vapor vent valve falls below the surface of fuel, the vent valve automatically closes to prevent flooding of the respective vapor line and remote vapor canister or other downstream component.  
         [0010]     Objects, features, and advantages of this invention include the ability of a vehicle to travel over substantially sloped terrain for prolonged periods of time without degrading the performance of the combustion engine, greater flexibility in the shape of vehicle fuel tanks to conform to available space while maximizing liquid fuel storage volume, the ability to vent multiple vapor domes in a fuel tank simultaneously, improved fuel tank pressure control, reduced hydrocarbon emission into the environment by reducing the number of required tank penetrations and greater flexibility in the location of a fuel tank penetration for routing a vapor line to the vapor canister. Furthermore, the fuel storage system is relatively light weight, relatively simple in design, reliable, durable, rugged and in service has a long useful life. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     These and other objects, features and advantages of this invention will be apparent from the following detailed description of preferred embodiments, appended claims and accompanying drawings in which:  
         [0012]      FIG. 1  is a diagrammatic view of one presently preferred embodiment of a fuel storage system illustrated in an automotive vehicle at a front-to-back angle of forty-five degrees to a horizontal plane;  
         [0013]      FIG. 2  is a diagrammatic view of the fuel storage system when the vehicle is level with the horizontal plane;  
         [0014]      FIG. 3  is a diagrammatic view of the fuel storage system when the vehicle is at a back-to-front angle of forty-five degrees to a horizontal plane;  
         [0015]      FIG. 4  is a cross section of the fuel tank assembly illustrating the fuel storage system at a low fuel level;  
         [0016]      FIG. 5  is a cross section of the fuel tank assembly at an intermediate fuel level;  
         [0017]      FIG. 6  is a cross section of a fuel tank assembly illustrating the fuel storage system at a high fuel level;  
         [0018]      FIG. 7  is a cross section of a buoyant vapor vent valve of the fuel tank assembly in an open position; and  
         [0019]      FIG. 8  is a cross section of the buoyant vapor vent valve of the fuel tank assembly in a closed position. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0020]     As best illustrated in  FIGS. 1-5 , a fuel storage system  20  according to one embodiment of the present invention generally stores on-board fuel for use in a combustion engine  22  of a vehicle  24 . During normal refueling operations of the vehicle  24  when typically at a refueling station, a remote fuel pump having an automatic shut-off fuel pump nozzle is designed to quickly and conveniently refuel a tank  26  of the fuel storage system  20 . When refueling at the station, government regulatory requirements dictate that an incline  48  of the vehicle  24 , and thus generally the on-board fuel tank  26 , falls within an approximate angular range of plus and minus three degrees with reference to an imaginary horizontal plane  27  (herein referred to as on-road refueling and best illustrated in  FIG. 2 ). When refueling the tank  26  within this angular range, the fuel storage system  20  must receive the supply fuel at a predetermined high volumetric flow rate through a fill tube  30  without creating spit-back or a back pressure in the tube that would inhibit the supply fuel flow or release hydrocarbons to the surrounding environment. Moreover, when the fuel tank  26  becomes full, a back pressure of fuel is created in the fill tube  30  that is sensed by the fill nozzle which automatically shuts off the remote fill pump. This automatic shut-off occurs while maintaining a minimum or primary fuel vapor dome  46  in the tank that is vented by a vapor assembly  36 .  
         [0021]     During less frequent off-road refueling operations of the fuel tank  26 , the automatic shut-off fuel pump of a fuel station is not available and the tank  26  most be filled manually typically by the vehicle operator and commonly by dispensing liquid fuel from at least one portable fuel can often having a storage capacity of about five gallons (herein referred to as off-road refueling, and best illustrated in  FIGS. 1 and 3 ). During off-road refueling and engine operation, the incline  48  of the vehicle  24  may fall considerably outside of the angular range of plus and minus three degrees from the horizontal plane  27 . This greater angular orientation could effect the flow performance of the fill tube  30  creating a back pressure in the tube, however, because the supply fuel is gravity fed into the fill tube  30  and because of flow inhibiting characteristics of portable fuel cans, the flow rate into the tank is considerably less than that from a remote fuel pump, therefore spit back of fuel out of the vehicle is unlikely and any surges of back pressure while filling the tank  26  will not operate to cut-off supply fuel manually flowing into the tank.  
         [0022]     When manually refilling the tank  26 , it is the operator&#39;s responsibility to stop the filling operation before fuel overflows out of the filler tube  30 . Preferably, however, the vapor assembly  36  is constructed and arranged to maintain the minimum vapor dome  46  volume during off-road refueling while maximizing the fuel storage capacity of the tank  24  regardless of incline  48 . Preferably then, an inlet  32  at one end of the fill tube  30  is located at a sufficient height above an opening  35  in a top wall or ceiling  34  of the tank and at an opposite end of the fill tube  30  to enable off-road refueling of the tank  26  to its maximum liquid fuel storage capacity at a maximum predetermined incline  48  of the vehicle  24  from the imaginary horizontal plane  27  that is generally parallel to an upper fuel surface  42 .  
         [0023]     Referring to  FIGS. 4 and 5 , the fuel tank  26  has the primary vapor dome or pocket  46  and preferably at least one secondary vapor dome or pocket  44 . The vapor domes  44 ,  46  are defined between the fuel surface  42  and the tank wall  34 . The combined volume of the vapor domes  44 ,  46  when the tank  24  is filled with liquid fuel to a maximum capacity preferably meets the predetermined minimum vapor dome volume to compensate for thermal expansion of the stored liquid fuel  28  provided both domes are vented. If any one vapor dome is vapor locked or un-vented, its volume generally does not contribute toward the minimum volume required for the vapor domes. Preferably, for smooth engine operation, the vapor assembly  36  is capable of venting at least dome  44  or dome  46  when incline  48  is at least plus or minus thirty degrees and preferably as high as plus or minus forty-five degrees.  
         [0024]     The quantity, size and placement of the vapor domes  44 ,  46  in the tank  26  is dependent upon the shape of the tank  26 , the angular position or incline  48  of the tank  26  relative to the imaginary horizontal plane  27  at any given time and the quantity of fuel stored in the tank. Preferably, during on-road refueling, the primary vapor dome  46  is in communication with the fill tube opening  35  throughout the refueling operation. This assures that a back pressure of fuel is not created at the opening  35  during the high flow rate of fuel coming from the refueling pump nozzle that could cause premature automatic shut-off of the remote fuel pump. Preferably, when the tank reaches maximum capacity during on-road refueling, the primary vapor dome  46  of the fuel storage system  20  is the only remaining vapor dome and consequently, alone, comprises the minimum vapor dome volume. Such a relationship has the benefits of substantially alleviating any premature fuel backup concerns in the filler tube  30  and maximizing the fuel storage capacity of the tank  26  while minimizing its size for packaging to the vehicle  24 .  
         [0025]     The fuel storage system  20  also has a self-referencing vapor assembly  36  that generally allows vapor and air to exit the tank  26  as supply fuel  28  enters, and generally allows the tank  26  to breathe during normal vehicle use at a prescribed internal pressure that may or may not be atmospheric. The vapor assembly  36  has one and preferably a plurality of buoyant vapor vent valves  38 ,  40  that generally float with limited freedom upon the fuel surface  42  in the tank  26  and in the associated at least one vapor dome or pocket  44 ,  46 . The vapor vent valves  38 ,  40  are in an open position when not otherwise submerged to a sufficient degree against their own buoyant force. Preferably, any one vent valve is capable of permitting a sufficient flow rate of vapor and air out of the tank  26  to prevent the filler tube  30  from prematurely backing-up with liquid fuel that could prematurely shut-off the remote fuel pump and nozzle during on-road refueling, and/or to displace sufficient vapor from the vapor domes with fuel to maximize tank storage capacity. In-other-words, during on-road refueling with the primary vapor dome  46  in communication with the opening  35  of the filler tube  30  and provided at least one of the plurality of vapor vent valves  38 ,  40  is open, additional supply fuel can be added through the filler tube  30  without premature actuation of the automatic shut-off of the remote refueling pump nozzle.  
         [0026]     The free floating movement of the vapor vent valves  38 ,  40  is generally limited by flexible vapor lines or tentacles  50 ,  52  that generally extend from a vapor manifold  54  and to each respective one of the vapor vent valves  38 ,  40 . When a vapor vent valve is in its open position, vapor can flow from the respective vapor dome  44 ,  46 , through the respective tentacle  50 ,  52 , out of the tank  26  via the manifold  54  and through a common conduit  56  that extends to a vapor canister  58 . Preferably, the manifold  54  is in the tank and is formed as one unitary piece with a flange  76  that covers and seals an access hole in the tank  26 . The canister  58  is preferably filled with an activated charcoal to absorb the hydrocarbon vapors received from the vapor vent valves  38 ,  40  and discharges the vapor through an outlet port  60  into the intake manifold  62  of the operating engine  22 . The interior of the canister  58  may be directly vented to the atmosphere through a port in the canister (not shown) or indirectly through a vent to the interior of the fuel tank and preferably to a vapor dome area. The canister  58  may be mounted in the vehicle  24  adjacent or spaced from the fuel tank  26  or in the fuel tank and the conduit  56  and the ‘intake manifold connection’ can be made by suitable flexible hoses.  
         [0027]     As best illustrated in  FIGS. 4-6 , the vapor assembly  36  has at least one and preferably two buoyant vapor vent valves  38 ,  40 , one located in a first portion  64  of the fuel tank  26  and one located in a second portion  66  spaced from the first portion  64 . The tentacles  50 ,  52  are flexible enough to allow the vapor vent valves  38 ,  40  to relatively freely float in the liquid fuel and move up and down with the changing level of the liquid fuel through a distance that is generally equivalent to the height of the respective portions  64 ,  66  of the fuel tank  26 . Preferably, each vapor vent valve  38 ,  40  is also free to float laterally (from side-to-side) with respect to the fuel tank  26 . This degree of freedom allows each vapor vent valve  38 ,  40  to seek out an associated vapor dome  44 ,  46  that may generally shift within the tank  26  and with changing road angles of inclination  48  and camber that the vehicle  24  is subject to. Depending upon the shape of the fuel chamber  25 , the extent of flexibility of the tentacles may vary. As illustrated, each tentacle  50 ,  52  has corrugated flexible end portions  68 ,  70  and a rigid mid portion  72 . The rigid mid portion  72  connects to each of the corrugated end portions  68 ,  70  preferably by flow-through swivel joints  74  (see  FIG. 4 ). However, if the corrugated end portions  68 ,  70  provide sufficient flexibility one or both of the swivel joints  74  can be fixed.  
         [0028]     In  FIGS. 4-6  the fuel tank  26  is shown substantially level or horizontal reflecting a vehicle  24  sitting at an incline  48  of about zero degrees (see  FIG. 2 ). The wall  34  of the tank  26  is contoured to achieve a close fit to the undercarriage of the vehicle  24  while maximizing fuel storage capability. Referring to  FIG. 4 , the fuel tank  26  is substantially empty of fuel  28 , thus one large, continuous vapor dome  46  that far exceeds the predetermined minimum volume is defined over the fuel surface  42 . The vapor dome  46  communicates directly with the fill tube opening  35  and the vapor vent valves  38 ,  40  generally bob or float near the bottom of the tank  24  in an open position for venting air and fuel vapor to the canister  58 . Each vapor vent valve  38 ,  40  preferably has a bottom bumper  82  to dampen any noise created when the valves rest on or impact the bottom  78  of the tank  26 .  
         [0029]     Referring to  FIG. 5 , the fuel tank  26  is almost but not quite full. Due to the contour of the tank wall  34 , two separate vapor domes  44 , 46  are defined in the fuel tank  26 . The primary vapor dome  46  communicates with the fill tube opening  35  and because both respective vapor vent valves  38 ,  40  are still open (see  FIG. 7 ), the air and fuel vapor in each dome is not trapped and can be vented from the tank. Since the vapor vent valves  38 ,  40  are still open, the fuel tank  26  is still capable of receiving more supply fuel without significantly, if at all, increasing the pressure within the tank. This reduces or eliminates the likelihood that fuel will backup in the filler tube  30 .  
         [0030]     Referring to  FIG. 6 , the fuel tank  26  is full. In this particular illustration, the secondary vapor dome  44  has essentially been vented away by the now closed vent valve  38  and the primary vapor dome  46  is approximately at the predetermined minimum volume hence the second vapor vent valve  40  is also closed. Preferably, and particularly for on-road refueling, the second vent valve  40  located in the primary vapor dome  46  closes after the first vent valve  38  because closure of the second vent valve  40  first could create a back pressure at the opening  35  adjacent to the primary vapor dome  46  causing fuel to backup in the filler tube  30  and the remote fuel supply pump to prematurely shut-off automatically.  
         [0031]     Referring to  FIG. 2 , the fuel tank  26  is shown in the environment of the vehicle  24  being substantially level and the tank  26  almost full as previously described and shown in  FIG. 5 . Both the forward and rearward vapor domes  44 ,  46  are generally below the fill tube  30  and are vented by their respective vapor vent valves  38 ,  40 . As illustrated in  FIG. 1 , with the same amount of fuel, and with the vehicle  24  driving down, or parked on, about a forty-five degree incline  48 , the forward vapor dome  44  is gone (filled with liquid fuel) and all the air and vapor in the tank has collected in the rearward portion  66 , thus enlarging the vapor dome  46  of the tank  26 . The forward vapor vent valve  38  being restricted in movement to the forward portion  64  is submerged in liquid fuel and thus closed, however the rearward vapor vent valve  40  remains floating and thus open. With the vent valve  40  open, the fuel storage system  20  is able to maintain substantially constant or a suitable range of tank pressure and thus, the steep incline  48  will not adversely effect engine performance. Similarly,  FIG. 3  illustrates the vehicle  24  on an upward incline  48  of about forty-five degrees with the same amount of fuel as in  FIG. 2 . On the upward forty-five degrees incline  48 , the rearward or primary vapor dome  46  is gone (filled with liquid fuel) and all the air and vapor in the tank has collected in the forward portion  64  of the tank  26  thus enlarging vapor dome  44 . The rearward vapor vent valve  40  being generally restricted in movement to the rearward portion  66  is submerged in liquid fuel and thus closed, however the forward vapor vent valve  38  remains floating and thus open to the vapor dome  44 .  
         [0032]     As best illustrated in  FIG. 7-8 , the housing  80  of each vent valve  38 ,  40  is preferably of closed cell foam construction thus providing the necessary buoyancy. However, a buoyancy jacket could be used over a non-buoyant housing, a housing with a closed chamber or “float” therein could be used, or the like. An optional ballast  84  may be provided at a lower end of the housing  80  along with the bumper  82 . Preferably, each valve  38 ,  40  has a submergible compartment  86  of the housing  80  that contains a float  90 , a seat  96 , and a head valve  92  between the float and seat. Preferably the head  92  is pivotally carried by the housing and underlies the seat  96  so that the head is movably biased by gravity to an open position as shown in  FIG. 7 . When the vapor vent valve  38 ,  40  is open, the float  90  generally rests upon a bottom  94  of the compartment  86 . In operation, when the vapor vent valve  38 ,  40  is submerged in liquid fuel and the fuel surface  42  rises above the ports  98  of the compartment  86 , the float  90  also rises with respect to the housing and moves the valve head  92  with it until the head sealably contacts the valve seat  96  thereby closing the valve  38 ,  40  and preventing liquid fuel from entering the vapor tentacle  52 , as best shown in  FIG. 8 .  
         [0033]     As best illustrated in  FIGS. 7 and 8 , the minimum required vapor dome volume, whether it is located in the primary vapor dome  46  or migrates over to the secondary vapor dome  44 , or both, is maintained by restricting buoyancy movement of the valves  38 ,  40 . For instance,  FIG. 8  illustrates the tank wall  34  resisting the natural buoyant force of valve  40  causing the compartment  86  to partially fill with fuel, and the float  90  to rise thereby closing the valve. In this illustration the minimum vapor dome volume is represented by the height between fuel surface  42  and overhead wall  34  (designated by arrow  100  in  FIG. 8 ). Height  100  is generally the difference between the height of the valve  40  above the fuel surface  42  when unobstructively floating (see arrow  102  in  FIG. 7 ) minus the vertical throw of float  90  (see arrow  104  in  FIG. 8 ). Other ways to preserve a minimum vapor dome in the tank  26  include use of a tether  106  extended generally between the bumper  82  or lower end of the valve  40  and the bottom  78  of the tank  26 , or the tentacles  50 ,  52  can be constructed to generally limit vertical valve movement.  
         [0034]     Each valve  38 ,  40  is roll-over protected or responsive because should the vehicle  24  and tank  26  overturn, the tentacles  52  restrain the vapor vent valves  38 ,  40  from rotating thus resisting the movement of inertia created by ballasts  84 . With the vapor vent valve  38 ,  40  thus inverted, the valve head  92  closes by gravity with the pressure head of any fuel above it acting upon. If no fuel enters compartment  86  (through holes  98 ) the float  90  also bears on the head  92  and if liquid fuel enters the compartment the float buoyancy causes the float  90  to press against the now inverted bottom  94  of the submerged compartment  86 , thus the float  90  does not act upon the valve head  92 .  
         [0035]     While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. For instance, if the vent valves  38 ,  40  do not require a roll-over protection feature, the valve head  92  could be buoyant and the float  90  would not be required at all. It is not intended herein to mention all the possible equivalent forms or ramifications of the invention. It is understood that the terms used herein are merely descriptive, rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention.