Abstract:
A valve assembly is provided that permits adjustable vent flow from the fuel tank vapor space through a bypass vent opening based on a condition in the vapor space after nozzle shutoff. The valve assembly including a first valve, also referred to as a main float, that provides rollover protection and controls venting of the vapor space prior to nozzle shutoff. A secondary closure device, also referred to as a second valve, moves independently of the first valve to control venting of the vapor space after nozzle shutoff through a bypass vent opening formed in the valve housing in response to at least one operating condition in the fuel tank outside of a chamber defined by the valve housing in which a main float moves.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates to a valve assembly with a device configured to adjust vent flow from a fuel tank. 
       BACKGROUND OF THE INVENTION 
       [0002]    Fuel tank valve assemblies that function to provide fuel nozzle shutoff once liquid reaches a predetermined level are known. A float device is often provided to accommodate shutoff by interfering with a vent passage once fuel reaches the predetermined level. Furthermore, these valve assemblies often provide rollover protection by closing liquid escape paths upon inversion of the tank. It is desirable to vent the fuel tank vapor space when the fuel level is at or above the shutoff level. 
       SUMMARY OF THE INVENTION 
       [0003]    A valve assembly is provided that permits adjustable vent flow from the fuel tank vapor space through a bypass vent opening based on a condition in the fuel tank after nozzle shutoff. The valve assembly also provides rollover protection. Specifically, a valve assembly for controlling fluid communication between a vapor space of a fuel tank and a vapor outlet includes a housing defining a chamber configured to be open to the fuel tank when at least a portion of the housing is placed in the fuel tank, and further defining a vapor vent passage in fluid communication with the chamber. The chamber is in selective fluid communication with the vapor outlet through the vapor vent passage. A first valve, which may be a float-type valve referred to as a main float, is disposed in the chamber and operable for restricting venting through the vapor vent passage when fuel in the chamber reaches a predetermined level. The housing defines a bypass vent opening above the predetermined level for fluidly communicating the vapor space with the vapor vent passage. 
         [0004]    A secondary closure device, also referred to as a second valve, is configured to move independently of the first valve to control venting of the vapor space through the bypass vent opening in response to at least one operating condition in the fuel tank outside of the chamber. The secondary closure device may be of any suitable type, such as a pressure-sensitive diaphragm responsive to a pressure differential between the vapor space and the vapor outlet, a secondary float responsive to a fuel level in the tank outside of the chamber, or both, or a motion sensitive valve. The control or adjustment of venting afforded by the secondary closure device may be proportional (i.e., the adjustment in venting is in proportion to the operating condition in the fuel tank) or binary (i.e., a first amount of venting in the absence of the operating condition, which may include a complete closure and therefore absence of venting, and a second amount of venting when the operating condition occurs). Because the secondary closure device moves independently of the first valve, the movement is directly in response to the operating condition, rather than in response to movement of the first valve. This permits the secondary control device to provide a more precise degree of control as well as flexibility of control than if the secondary control device moved indirectly, via the first valve, in response to the operating condition. 
         [0005]    Thus, the first valve is movable in the chamber toward the vapor vent passage in response to liquid fuel in the tank (and in the chamber), whether due to filling of the tank, sloshing of fuel, orienting the tank at a grade, or due to inversion of the tank. The first valve is configured to reduce vapor flow from the tank through the vapor vent passage when the first valve moves toward the vapor vent passage. The second valve outside of the chamber is configured to move with respect to the bypass passage to vary flow through the bypass passage in response to at least one operating condition in the fuel tank outside of the chamber at which the first valve has moved to reduce vapor flow through the vapor vent passage. 
         [0006]    The configuration of the valve assembly with first and second valves enables multiple stages of operation, with the first valve configured to permit venting from the chamber under a first set of operating conditions in the chamber, thereby establishing a first stage of the valve, and to restrict venting from the chamber under a second set of operating conditions in the chamber, thereby establishing a second stage of the valve. The second valve is configured to adjust vapor flow from the tank through the bypass vent opening in response to a different set of operating conditions in the tank outside of the chamber, thereby establishing another stage of the valve. The different operating conditions may be different fuel levels within the tank, different pressure differentials between the tank vapor space and the vapor outlet, or a combination of these conditions. 
         [0007]    The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a schematic cross-sectional illustration of a valve assembly mounted to a fuel tank showing a first stage of operation; 
           [0009]      FIG. 2  is a schematic cross-sectional illustration of the valve assembly of  FIG. 1  in a second stage of operation; 
           [0010]      FIG. 3  is a schematic cross-sectional illustration of the valve assembly of  FIG. 1  in a third stage of operation; 
           [0011]      FIG. 4  is a schematic cross-sectional illustration of the valve assembly of  FIG. 1  in a fourth stage of operation; 
           [0012]      FIG. 5  is a schematic cross-sectional illustration of a second embodiment of a valve assembly; 
           [0013]      FIG. 6  is a schematic cross-sectional illustration of a third embodiment of a valve assembly; 
           [0014]      FIG. 7  is a plot of vapor vent flow (liters per minute) versus tank vapor space pressure (kilopascals) through a valve assembly similar to that of  FIGS. 1-4 , but having an open bottom rather than a vent window at various fuel levels; 
           [0015]      FIG. 8  is a plot of vapor vent flow (liters per minute) versus tank vapor space pressure (kilopascals) through a valve assembly having a bypass opening but no secondary closure device at various liquid heights above an initial shutoff level; and 
           [0016]      FIG. 9  is a schematic cross-sectional illustration of a fourth embodiment of a valve assembly. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    Referring to the drawings, wherein like reference numbers refer to like components,  FIG. 1  shows a multi-stage valve assembly  10  mounted to a fuel tank  12 . The valve assembly  10  has a housing  14  with interior walls  15  defining an interior chamber  16 . The housing  14  also defines a vapor vent passage  18 , also referred to as a vent opening, which is in fluid communication with a vapor outlet  20 . The vapor outlet  20  leads to a vapor recovery canister (not shown) or other destination outside of the tank  12 . The housing  14  also defines a bypass vent opening  22 , also referred to as a bypass passage. The bypass vent opening  22  is open to vapor space  24  in the tank  12  above a fuel level  26  of fuel  27  within the tank  12 . The housing  14  also defines a vent window  28  generally near the bottom of the valve assembly  10  when the valve assembly  10  is mounted in the tank  12 . The vent window  28  is positioned to admit fuel in the tank  12  into the chamber  16  when the fuel level rises below the bottom surface  32  of the housing  14  and at least to the level of the window  28 , such as when fuel is added to the tank  12  or during sloshing, positioning the tank  12  on a grade, or during inversion of the tank  12 . The housing  14  has small drain holes (not shown) extending through the depression  30  to the bottom surface  32 . Although shown as a unitary molded component, the housing  12  may be several integrated components, and may be made of any suitable material, such as plastic or aluminum. 
         [0018]    The valve assembly  10  includes a main float  34 , also referred to as a first valve, disposed in the chamber  16 . The main float  34  is buoyant in liquid fuel  27 , and includes a cavity  36  that is normally filled with vapor, and may fill with liquid fuel when the tank  12  is inverted. The cavity  36  is also part of the chamber  16 . A spring  38  positioned between the main float  34  and the housing  14  biases the main float  34  toward the vapor vent passage  18 . A ribbon seal  39  is secured on one end to the interior wall  15  of the housing  14  and at another end to the main float  34 . As the main float  34  rises in the chamber  16  due to contact with liquid fuel, the main float  34  pushes the ribbon seal  39  against the vapor vent passage  18  to restrict venting of vapor or leakage of fuel through the vapor vent passage  18 . This scenario is illustrated with respect to  FIG. 2 , and is discussed further below. It should be appreciated that the construction of the ribbon seal  39 , the main float  34 , and the housing  14  may be designed to control the amount of venting, if any, through the vapor vent passage  18  when the float  34  pushes the seal  39  against the passage  18 . For example, the float  34  may be designed to toggle between the closed position of  FIG. 2  and a slightly opened position due to motion of the fuel, allowing limited venting past the vapor vent passage  18 , as illustrated by arrow V 5  of  FIG. 3 , even when the diaphragm  40 , discussed below, is closed. Alternatively, the seal  39 , float  34  and housing  14  could be designed to substantially prevent any venting through passage  18  when the seal  39  is pressed against the housing  14 . 
         [0019]    The valve assembly  10  further includes a secondary closure device  40 , also referred to as a second valve, which in this embodiment is a pressure-sensitive diaphragm, and will be referred to as such. The pressure-sensitive diaphragm  40  has a fixed outer diameter seal portion  42  sealed to a portion  43  of the housing  14 . A dynamic inner diameter seal portion  44  is selectively sealed to the portion  43  to prevent vapor flow from the vapor space  24  through the bypass vent opening  22  to the chamber  16  through the central opening  46 . One side  48  of the diaphragm  40  is exposed to the vapor space  24  via the bypass vent opening  22 . The other side  50  of the diaphragm  40  is exposed to pressure in the vapor outlet  20 , which is substantially atmospheric or ambient pressure. A spring  52  biases the diaphragm  40  to a closed position, and is configured with a spring force that is overcome by an opposing force on the diaphragm  40  resulting from a preselected pressure differential between the vapor space  24  and the vapor outlet  20 . 
         [0020]    In  FIG. 1 , the relationship of the fuel level in the tank  14  relative to the housing  14  establishes a first set of operating conditions affecting the position of the main float valve  34  and the pressure-sensitive diaphragm  40 . The operation of the valve assembly  10  in response to these conditions may be considered a first stage of the valve assembly  10 . Specifically, fuel level  26  is a first fuel level below the window  28  of the housing  14 , and represents a fuel level at less than full, such as before or during filling. At such a fuel level, the vapor space  24  is in direct fluid communication with the window  28 . The main float  34  is not restricting flow through the vapor vent passage  18 . The pressure-sensitive diaphragm  40  is likely closed, as a predetermined pressure differential between the vapor space  28  and the vapor outlet  20  may not be present. Thus, as represented by arrow V 1 , vapor can vent from the vapor space  24  through the window  28 , and through the annulus  54  between the outer walls of housing  14  and inner walls  15 . Baffles (not shown) formed by the housing  14  and interior walls  15  may be positioned throughout the annulus  54  to separate any entrained liquid fuel from the vapor. The annulus  54  is open to the upper portion of the chamber  16  above the main float  34 , through another window, not shown, in the inner walls  15 . Thus, the vapor vents through the vapor vent passage  18 , as represented by arrow V 2 , and out through the vapor outlet  20 , as represented by arrow V 3 . 
         [0021]    Referring to  FIG. 2 , the relationship of the fuel level in the tank  12  relative to the housing  14  establishes a second set of operating conditions affecting the position of the main float valve  34  and the pressure-sensitive diaphragm  40 . The operation of the valve assembly  10  in response to these conditions may be considered a second stage of the valve assembly  10 . Specifically, fuel level  26 A has risen due to filling of the tank  12  to cover the window  28 . With no vapor vent flow through the window  28 , the vapor pressure in the vapor space  24  of the tank  12  causes fuel to rise inside the chamber  16  (through window  28 ) to fuel level  26 B, elevating the main float  34 , which presses the ribbon seal  39  against the vapor vent passage  18 . 
         [0022]    Referring to  FIG. 3 , the fuel level  26 C in the tank  12  has risen slightly above the shutoff level  26 A of  FIG. 2 . Fuel level in the chamber is fuel level  26 B, the same as in  FIG. 2 . The main float  34  is elevated, pressing the ribbon seal  39  against the vapor vent passage  18 .  FIG. 3  represents a third set of operating conditions in which pressure in the vapor space  24  has risen above pressure levels associated with the second set of operating conditions, such as due to continued filling of the tank beyond nozzle shutoff. The pressure in the vapor space  24  is not high enough to establish the predetermined pressure differential at which the diaphragm  40  opens. However, the housing  14  is formed with a slight notch  60  that permits some venting from the vapor space  24 , through the central aperture  46 , as represented by arrow V 4 . Thus, some restricted, low pressure venting of the vapor space  24  is accomplished during the third set of operating conditions, establishing a third stage of the valve assembly  10 . For example, if the pressure in the vapor space  24  is approximately 2 kPa at nozzle shutoff, the third stage may allow the restricted venting until a predetermined pressure differential, which may be at about 4 kPa pressure in the vapor space, causes the diaphragm  40  to open. Alternatively, the housing  14  could be designed without the notch  60 , in which case no venting of the vapor space  24  through the valve assembly  10  would occur during the third set of operating conditions. 
         [0023]    Referring to  FIG. 4 , the fuel level in the tank is fuel level  26 C, the same as in  FIGS. 2 and 3 .  FIG. 4  represents a fourth set of operating conditions in which pressure in the vapor space  24  has risen above pressure levels associated with the second and third sets of operating conditions, and the predetermined pressure differential between the vapor space  24  and the vent outlet  20  is reached, causing the diaphragm  40  to lift to an opened position in which it is indicated as  40 A. The predetermined pressure differential may be associated with pressures in the tank  12  above a certain pressure, such as 4 kPa. Thus, substantial venting of the vapor space  24  is accomplished through the bypass vent opening  22 , as represented by arrow V 6 , past the lifted diaphragm  40 A and through central opening  46 , as represented by arrow V 7 . The opening of the diaphragm valve  40  allows pressure to increase within the chamber  16 , causing the fuel level in the chamber  16  to drop slightly to level  26 D, and the main float  34  to therefore also drop slightly, permitting the vented vapor that passed through the bypass opening  22  to also pass through the vapor vent passage  18  and the outlet  20 , as illustrated by arrows V 8 , V 9  and V 10 . 
         [0024]    Referring to  FIG. 5 , an alternative second embodiment of a multi-stage valve assembly  10 A is shown. The multi-stage valve assembly  10 A has many components and features identical to those of valve assembly  10 , and identical reference numbers are used to refer to identical components and features. The valve assembly  10 A includes a housing  14 A formed with an extension  61  defining an auxiliary chamber  62 . The extension  61  has a side opening  64  in communication with vapor space  24  and a bottom opening  66  open to fuel in the tank  12 . A secondary float  68  is supported in the auxiliary chamber  62  and includes a needle valve portion  70  configured to selectively interfere with a float opening  72  within the chamber  62 . 
         [0025]    When fuel is at fuel level  26 , the main float  34  is in the position shown, with the ribbon valve  39  not blocking vapor venting through window  28  and vapor vent passage  18 . The secondary float  68  is in the position shown, with the needle valve portion  70  substantially or completely restricting vent flow through the side opening  64  and bypass vent opening  22 . Thus, the vapor space  24  is substantially or completely prevented from venting through the bypass opening  22  via the diaphragm  40 . 
         [0026]    When fuel level in the tank  12  rises to levels above the window  28  and up to fuel level  26 E, fuel within the chamber  16  rises even higher, causing the main float  34  to rise to the position shown in  FIGS. 2 and 3 , and the secondary float  68  stays in the position shown in  FIG. 5 . If fuel level in the tank  12  outside of the chamber  16  rises above the predetermined fuel level  26 E, such as to fuel level  26 F, the secondary float  68  is buoyed upward to the position shown in phantom indicated as  68 A. The tapered nature of the needle valve portion  70  thus allows venting of the vapor space  24  through float opening  72  and bypass opening  22 . The vapor passes the diaphragm  40  either via a notch  60  as described above, or if the pressure differential is sufficient, by lifting the diaphragm  40  to position  40 A of  FIG. 4 , and then past the main float  34  and ribbon seal  39 , if the float  34  is biased downward to the position shown in  FIG. 4  via the vapor pressure. Thus, the secondary float  68  with needle valve portion  70  and the diaphragm  40  acts in series with one another to affect venting of the vapor space  24  through the bypass opening  22  as represented by arrows V 11 , V 12 , V 13 , V 14 , V 15  and V 16 . 
         [0027]    Referring to  FIG. 6 , another alternative third embodiment of a multi-stage valve assembly  10 B is shown. The multi-stage valve assembly  10 B has many components and features identical to those of valve assemblies  10  and  10 A, and identical reference numbers are used to refer to identical components and features. The valve assembly  10 B includes main float  34 B with a seal  39 B that may be a ribbon seal such as ribbon seal  39  of  FIGS. 1-5 , or a seal secured at both ends to the float  34 B for movement with the float  34 . The valve assembly  10 B includes a housing  14 B defining a main chamber  16 B and formed with an extension  61 B defining an auxiliary chamber  62 B. The main chamber  16 B is directly open to the fuel level in the tank  12  at bottom depression  30 B. When fuel level rises above the bottom depression  30 B, venting of the vapor space  24  through the bottom depression  30 B ceases. The extension  61 B has a side opening  64 B in communication with vapor space  24  and a bottom opening  66 B open to fuel in the tank  12 . A secondary float  68  is supported in the auxiliary chamber  62 B and includes a needle valve portion  70  configured to selectively interfere with float opening  72  within the chamber  62 B. 
         [0028]    The housing  14 B includes a separate opening  78  communicating pressure in vapor space  24  with the diaphragm  40 . The secondary float  68 , needle valve  70  and diaphragm  40  operate as described with respect to  FIG. 5 , except that rather than being in series with one another, they operate in parallel to affect vent flow through the vent opening  22 B. Venting of the vapor space  24  past the diaphragm  40  is in response to a predetermined pressure differential between the pressure of the vapor space  24  and the pressure at the vapor vent outlet  20 , which act on opposite sides of the diaphragm  40 . Venting of the vapor space  24  past the secondary float  68  and needle valve portion  70  through opening  64 B and past float opening  72  is in response to fuel level in the tank  12  outside of the chamber  16 B. Thus, venting of the vapor space  24  past the diaphragm  40 , as represented by arrow V 17 , is independent of venting of vapor space  24  past the secondary float  68  with needle valve portion  70 , as represented by arrow V 18 , with either or both sources of vapor venting combining at the bypass vent opening  22 B to vent past the vapor vent passage  18 B and out through the vapor outlet  20 B, as represented by arrow V 19 . 
         [0029]    Referring to  FIG. 7 , vapor vent flow in liters per minute (lpm) versus pressure (kPa) through a valve assembly similar to the valve assembly  10 A of  FIGS. 1-4  but having an open bottom to permit fuel into a chamber that houses the main valve, rather than having a vent window like window  28  and a depression like depression  30  with drain openings a relatively large fuel inlet opening. The vapor vent flow in the valve tested is via vapor flow from a vapor space like the vapor space  24  past a bypass opening like the bypass opening  22  and a diaphragm like diaphragm  40 . The flow is shown for various levels of fuel in the tank  12  above the bottom opening of the housing. A first curve  80  represents performance of the valve assembly with fuel level in the tank at 2.5 mm above the bottom opening. Curve  82  represents performance of the valve assembly with fuel level in the tank at 17.5 mm above the bottom opening. The curves  80  and  82  indicate that the diaphragm opens to adjust vapor vent flow from the vapor space at about 4 kPa in the vapor space, which corresponds with the predetermined pressure differential between the vapor space and the vapor outlet at which the diaphragm is configured to open. With the addition of the diaphragm, venting from the vapor space  24  is made to increase as pressure increases (i.e., venting is greater at or above 4 kPa than when pressure is below 4 kPa). The valve assembly  10 A of  FIGS. 1-4  is expected to provide vapor vent flow in a generally similar manner as illustrated by curves  80 ,  82 . 
         [0030]      FIG. 8  illustrates the performance of a valve assembly substantially identical to valve assembly  10 , having a bypass vent opening, but not having a secondary closure device. Venting of the vapor space through the bypass opening occurs without control or adjustment by a secondary closure device. A first curve  86  represents performance of the valve assembly with fuel level in the tank level with a bottom opening in the valve assembly, i.e., generally at the point of nozzle shutoff. Second curve  88  represents performance of the valve assembly with fuel level in the tank at 10 mm above the bottom opening in the valve assembly. Third curve  90  represents performance of the valve assembly with fuel level in the tank at 20 mm above the bottom opening in the valve assembly. Curves  86 ,  88  and  90  generally illustrate the phenomena of steady state vapor vent flow from the vapor space after nozzle shutoff through a constantly open bypass opening. These types of curves are generally flat, but may have a slight positive or negative slope depending on the precise conditions required to maintain flow equilibrium at each pressure. The curves indicate that flow is not constrained prior to reaching a threshold pressure, unlike curves  80  and  82  of  FIG. 7 . Curves  80  and  82  described above with respect to  FIG. 7  constrain vapor vent flow prior to the predetermined pressure differential at 4 kPa. Thus, a secondary closure device as described herein, such as diaphragm  40 , modifies the vapor vent flow performance relative to a valve assembly with no secondary closure device and therefore no bypass venting adjustment or control. 
         [0031]    Referring to  FIG. 9 , another embodiment of a multi-stage valve assembly  10 C is shown. Valve assembly  10 C is alike in all aspects to valve assembly  10 B of  FIG. 6 , and functions the same as valve assembly  10 B, with the exception that the secondary float  68  with needle valve portion  70  is replaced by a motion sensitive valve  92 . The motion sensitive valve  92  is depicted as a simple ball valve that rests atop the opening  72 A. When fuel tank  12  is in motion (i.e., when a vehicle to which tank  12  is mounted is in motion), the ball  90  moves off of the opening  72 , permitting flow through opening  72 A and bypass vent opening  22 B. 
         [0032]    While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.