Abstract:
A fuel vapor vent valve assembly is provided that may include a float valve and an isolation valve arranged in series with each other. Bypass openings in the valve assembly create multiple flow paths as the float valve and the isolation valve respond to changes in fuel tank pressure and fuel level. The control valve assembly may include a housing defining a chamber with a main opening configured to open the chamber to the tank, a vapor vent passage and a first bypass vent opening. A float in the chamber closes the vapor vent passage when fuel in the chamber is at or above a predetermined level. The first bypass vent opening vents the tank to the chamber even when the fuel covers the main opening. A feature on the float provides a metered opening of the vapor vent passage between closed and fully open based on float position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application 61/025,418, filed Feb. 1, 2008, which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to vapor vent valves for fuel tanks and more particularly to a vapor vent valve that is float-operated to control fuel vapor flow from the fuel tank to a storage device, such as a canister. 
       BACKGROUND OF THE INVENTION 
       [0003]    Float-operated vapor vent valves are often used in fuel tanks to control fuel vapor flow from the fuel tank to a vapor storage device, such as a canister filled with granulated carbonaceous material. Vapor may be controlled by attaching vapor management valves, such as a fuel limit vent valve and grade vent valves to the fuel tank. Typically, each valve is installed separately to the fuel tank by forming an opening in the fuel tank, inserting the valve into the opening, and sealing the valve to the opening to prevent leakage of fuel or fuel vapor. 
         [0004]    To reduce fuel vapor permeation and the number of openings in the fuel tank, multi-function vapor valve assemblies are known to provide the functions of two or more valves in a common assembly to be attached to the fuel tank through a single access opening, or otherwise mounted in the fuel tank. Such multi-function control valves often include multiple float operated valves that open and close different sized vent ports at different liquid fuel levels in the tank during refueling and in response to fuel sloshing in the tank during vehicle operation. 
         [0005]    An additional valve may be included to provide a first orifice that restricts vapor flow from the fuel tank during running conditions. This minimizes abrupt changes in vapor flow and allows more aggressive vapor purging, preventing tail pipe emissions caused by spikes in the fuel vapor level down a purge line. The valve assembly may also include a second orifice that manages vapor recirculation during refueling. The many functions required by the multi-function valve assemblies and the number of valves and flow paths resulting from the functions tend to increase both the size and the complexity of the valve assembly. The way in which the valves communicate with each other and operate relative to different fuel levels and vapor pressures in the fuel tank often requires complicated routing of fuel vapors around and through the various valves to obtain the desired functions. 
       SUMMARY OF THE INVENTION 
       [0006]    There is a desire to simplify the structure of the multi-function control valve assemblies while preserving its functionalities. Accordingly, a fuel vapor vent valve assembly is provided having multiple functions and a simpler configuration than currently known multi-function valve assemblies. One embodiment includes a float valve and an isolation valve arranged in series with each other. Bypass openings in the valve assembly create multiple flow paths as the float valve and the isolation valve respond to changes in fuel tank pressure. 
         [0007]    In one embodiment, the assembly includes a float valve in fluid communication with the fuel tank and operable to shut off fill at a selected fill level. The float valve includes a float, and a housing that has both a vapor vent passage and a bypass opening from the tank into the housing that bypasses the main opening(s) (e.g., an opening at the bottom of the housing and, optionally, one or more additional windows in the side of the housing). 
         [0008]    An isolation valve is fluidically coupled in series with the float valve upstream of the float valve and is operable to selectively cover and uncover a vapor vent passage in the housing. A vapor recovery passage is fluidically coupled to the float valve and the isolation valve. A recirculation passage is fluidically coupled to the float valve and the isolation valve. The float valve and isolation valve form a first flow path through the bypass opening to the vapor recovery passage to vent the fuel tank after the float closes the vapor vent passage. The float valve and isolation valve also form a second flow path through the vapor vent passage to the recirculation passage during tank fill when the float does not close the vapor vent passage. The float valve and isolation valve also form a third flow path through the vapor vent passage to the vapor recovery passage during vehicle operation when the float does not close the vapor vent passage. 
         [0009]    The control valve assembly may be for venting a vapor space of a fuel tank to a recirculation line and to a vapor recovery passage (e.g., a passage leading to a vapor recovery canister), and may include a housing defining a chamber with a main opening configured to open the chamber to the tank when at least a portion of the housing is placed in the fuel tank. The housing further defines a vapor vent passage and a first bypass vent opening. A float is disposed in the chamber and is operable for closing the vapor vent passage when fuel in the chamber is at or above a predetermined level. The first bypass vent opening is operable for venting the tank to the chamber even when the fuel covers the main opening. 
         [0010]    A feature on the float is operable to provide a metered opening of the vapor vent passage between closed and fully open based on float position to permit venting therethrough. The feature may be a peel-away feature connected to the float that is urged away from the vapor vent passage by the float when flow through the bypass opening equalizes pressures across the housing, reducing buoyancy of the float, tugging on the feature to induce peel away. Because the feature opens in a gradual, metered fashion, it opens under higher pressures than would a relatively large float. The need for a supplemental float that opens to allow venting after closure of the main opening (e.g., by fuel covering the bottom of the valve housing after filling the tank) is avoided. Therefore, only one float controls venting from the chamber, reducing required components necessary for vent-after-closure functioning. 
         [0011]    A cover is secured to the housing and defines a first passage for vapor flow to the recirculation line and a second passage for vapor flow to the canister. An isolation valve, which may be a diaphragm valve, is disposed in series with the float and is configured to control venting from the vapor vent passage to the cover by moving upon a predetermined pressure differential acting on the isolation valve to permit venting from the vapor vent passage to the recirculation line and the second passage. The cover defines a second bypass vent opening configured to permit venting of the vapor vent passage to the second passage. The control valve assembly is configured with an orifice configured to permit venting of the vapor vent passage to the recirculation line regardless of whether the isolation valve has moved. 
         [0012]    By creating multiple flow paths and functions all of which are affected by the position of a single float valve, the inventive structure removes the bulk of multiple float valves and simplifies the overall configuration of the multi-function valve while still responding to fuel level and vapor pressure as desired. 
         [0013]    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 
         [0014]      FIG. 1  is a representative partially cross-sectional diagram of one embodiment of a multi-function fuel vapor vent valve assembly; 
           [0015]      FIG. 2  is a schematic cross-sectional view of another embodiment of a multi-function fuel vapor vent valve assembly indicating a vapor recovery path occurring with an isolation valve lifted and a fill cap off, and with a run-loss flow path indicated in phantom with the fill cap on, as shown in phantom, and the isolation valve closed, as shown in phantom; 
           [0016]      FIG. 3  is a schematic fragmentary cross-sectional view of the valve assembly of  FIG. 2  showing a main float in a closed position; 
           [0017]      FIG. 4  is a schematic fragmentary cross-sectional view of the valve assembly of  FIGS. 2 and 3  showing a peel-away feature in operation enabling metered flow through a vapor vent passage as the main float moves to an open position in a first stage of grade vent flow; 
           [0018]      FIG. 5  is a schematic cross-sectional view of the valve assembly of  FIGS. 2-4  with the main float in a lower position than in  FIG. 4  during a second stage of grade vent flow; 
           [0019]      FIG. 6  is a schematic cross-sectional illustration of another embodiment of a multi-function fuel vapor vent valve having a vapor discriminating valve during recirculation flow and during run/loss flow (shown in phantom); and 
           [0020]      FIG. 7  is a schematic cross-sectional illustration of the valve assembly of  FIG. 6 , with the main float removed, illustrating the vapor discriminating valve providing secondary protection from liquid entering the vapor vent passages when at a grade angle or under a failure of the main float. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]      FIG. 1  is a representative diagram illustrating a multi-function valve assembly  10  according to one embodiment of the invention. The configuration of the valve assembly  10  is shown diagrammatically in order to provide an explanation of the assembly in general terms. Based on these teachings and the additional teachings set forth below, one of ordinary skill in the art would be able to devise various embodiments of the disclosed structure using various valve assemblies without departing from the scope of the invention. 
         [0022]    The multi-function valve assembly  10  has a first valve  12  and a second valve  14 . The valve assembly  10  also includes a recirculation passage  18  for directing fuel vapor toward a recirculation tube  17 , also referred to as a fill tube, and a vapor recovery passage  20  for directing fuel vapor toward a canister  19 . A fill cap indicated with reference number  21  is normally secured to the fill tube  17  except during filling of the tank  23 , and accordingly is operatively connected to the recirculation passage  18  to close the recirculation passage  18  from the atmosphere except during filling. The first valve  12  has an opening  22 , which in this embodiment is a drain opening disposed at a bottom of the first valve  12  and that drains into a fuel tank  23 . The first valve  12  also has a bypass opening  24  that is also open to the tank. The opening  22  could alternatively be in the side of the first valve  12 , but below the bypass opening  24 . The first valve  12  and the second valve  14  are fluidically coupled together in series through a vapor vent passage  15  to control vapor flow from the tank  23  through passages  22  and  24  to either the recirculation passage  18  or the vapor recovery passage  20 , depending on the operating state of the valve assembly  10  (e.g., pressure and liquid level, whether a fill cap is on or off, etc.). The second valve  14  will manage flow through a relatively large opening  39  to the vapor recovery passage  20 . Regardless of the relationship between the second valve  14  and opening  38 , flow is permitted from the vapor vent passage  15  to the vapor recovery passage  20  through a smaller bypass opening  38 . An orifice  40  permits flow to the recirculation passage  18  regardless of the relationship between the second valve  14  and opening  38 . 
         [0023]      FIGS. 2 through 5  are various section views of one embodiment of the invention. These figures show the valve assembly  10  in more detail, and illustrate the different vapor flow paths that are possible in the valve assembly  10  to carry out various functions. In these figures, the first valve  12  is a float valve  30  having a float  32  disposed in a chamber  31  formed by a housing  34 . The second valve  14  is an isolation valve, such as a diaphragm valve  36 , shown in an open, lifted position consistent with tank filling, and shown in phantom as  36 A in a closed, lowered position consistent with vehicle operation when a fill cap  21  is on to close a fill tube  17  fluidly communicating with the recirculation passage  18 , whether in run-loss flow or in vent-after-closure flow, as further discussed below. In other embodiments, the valve assembly  10  may be configured so that the second valve  14  moves downward or otherwise, rather than lifts, to an open position during tank filling, and moves to a closed position during vehicle operation when the fill cap  21  closes the fill tube  17 . A spring  43  biases the float  32  toward a lifted position, with additional force required to lift the float  32  provided by fuel reaching the float  32 . When the float  32  is lowered as in  FIG. 2 , fuel vapor may pass from the chamber  31  through the vapor vent passage  15 , also referred to as a float valve opening, into an upper chamber  29 . A peel-away feature  33  is connected to the float  32  at  35  (see  FIGS. 3 and 4 ). The peel-away feature  33  may be a flexible ribbon, or may pivot at  35  (also shown in  FIG. 4 ). A cover  37  is attached to the housing  34  and has the recirculation passage  18  and the vapor recovery passage  20  incorporated therein, as well as an accessory vent passage  46  that may provide vapor flow to an accessory port, such as to a separate rollover valve. The cover  37  is configured such that flow in a passage  39  communicates with upper chamber  29  and also with passage  20 . The housing  34  of the float valve  30  has the drain passage  22  at the bottom and the bypass opening  24  on its side. Both the drain passage  22  and the bypass opening  24  open into the fuel tank  23 . Alternatively or in addition, one or more windows could be provided in the side of housing  34 , above the bottom, to provide flow to the chamber  31 , with optional baffles in the flow path to remove entrained liquid. 
         [0024]    The cover  37  has a second bypass opening  38  that opens into the vapor recovery passage  20 , allowing venting of vapor that has passed through the vapor vent passage  15  and into the upper chamber  29  to the vapor recovery passage  20 , even though the diaphragm  36 A is not lifted. The valve assembly  10  may have a third bypass opening  40 , also referred to as an orifice, which allows vapor to pass into the recirculation passage  18 , both when the diaphragm  36  is lifted (as shown in solid in  FIG. 2 ) and when it is not lifted (shown in phantom as  36 A). The third bypass opening  40  may be through the diaphragm  36 A. Alternatively, the third bypass opening  40  may be elsewhere in the assembly  10 , such as in the housing walls and/or cap  37  to allow flow around the diaphragm  36 A. Note that the relative sizes of the drain  22  and the bypass openings  24 ,  38 ,  40  help control valve operation by controlling the rate at which liquid fuel and/or fuel vapor passes from one region into the next. 
         [0025]      FIG. 3  shows a portion of the assembly  10  during a shut off condition when fuel in the fuel tank  23  has been filled to a predetermined level A indicated in  FIGS. 2 and 5  (e.g., a full level). When fuel in the fuel tank  23  reaches the predetermined level, liquid fuel rises through the drain passage  22  even higher than the level A, causing the float  32  to rise and seat against the vapor vent passage  15  to close the float valve  30 , as shown in  FIG. 3 . The liquid within the housing  34  will rise faster than the liquid in the tank once the drain passage  22  of  FIG. 2  is closed off because of the differential between the pressure of the vapor space  25  and the pressure within the chambers  29 ,  31 . 
         [0026]    Once the float valve  30  closes to induce a nozzle shutoff, the liquid fuel slowly flows out of the drain passage  22  back into the fuel tank  23 . This is partially due to the pressure equalization of the tank vapor space  25  and the chamber  31  achieved in a first stage of vent-after-closure flow by flow through the bypass opening  24  and by action of the peel-away feature  33 , as described below and shown in  FIG. 4 , thereby dropping the float  32  and opening the float valve  30  to allow flow through the vent opening  15 . However, the liquid fuel level will still be high enough to cover the drain passage  22 , preventing vapor flow up through the drain passage  22 . 
         [0027]    The valve assembly  10  includes an optional secondary closure device, also referred to as a metering valve  44  that blocks vapor flow into the chamber  31  from the tank vapor space  25  through the bypass opening  24  unless the float  32  rises high enough so that shoulder  50  interferes with the metering valve  44 , pushing it off of seat  47  to allow bypass vapor flow through opening  48  into the chamber  31 . 
       Recirculation Flow Path and Primary Vapor Recovery Flow Path 
       [0028]    Referring to  FIG. 2 , a recirculation flow path is indicated by arrow B. Recirculation flow path B occurs during filling (i.e., refueling) of the tank  23 , with the fill level below the predetermined level A. When the fill cap  21  is off during refueling, the upper surface of the diaphragm  36  is exposed to atmospheric pressure. The higher fuel vapor pressure within the tank vapor space  25  acts on the lower surface of the diaphragm  36 . This pressure differential forces the diaphragm  36  upward. A recirculation flow pathway is formed along flow path B, from tank vapor space  25  to chamber  31 , then to chamber  29  and through orifice  40  to recirculation passage  18 . The vapors are then recirculated into the tank  23  with the entering fuel, thus limiting the amount of fresh air drawn into the tank  23 . 
         [0029]    At the same time, during tank fill, with the diaphragm  36  lifted, vapor flows along a primary flow path C from the vapor space  25  through opening  22  to chamber  31 , through vapor vent passage  15  to chamber  29 , underneath the lifted diaphragm  36  to an opening  39  larger than bypass opening  38  and formed within the cover  37  behind the housing  41  of the metered orifice  44  in the view shown, and in direct fluid communication with the vapor recovery passage  20 , and then on to canister  19 . 
       Vent After Closure/Grade Vent Flow Paths 
       [0030]    At the end of fill, nozzle shutoff occurs, the float  32  closes the vapor vent passage  15 , and the cap  21  is placed on the fill pipe, closing off flow out of the vapor recirculation passage  18 . Initially, fuel in the tank  23  still covers the bottom of the valve  30  including opening  22 , i.e., fuel is at or above the predetermined level A. With the cap  21  on, pressure on either side of the diaphragm  36 A equalizes, i.e., the pressure acting on the upper surface of the diaphragm  36 A is the same as the pressure acting on the lower surface, and the diaphragm  36 A is in the lowered, closed position shown in phantom in  FIG. 2 . After shutoff, the float  32  is initially in the position shown in  FIG. 3 , causing the metering valve  44  to rise by interference with a shoulder  50  of the float  32 , and allowing vapor from the vapor space  25  to flow through bypass opening  24  and opening  48 . With the float  32  in the upward position, flow through bypass opening  24  causes pressures across the housing  34  (between vapor space  35  and chamber  31 ) to equalize, which in turn causes the fuel inside the housing  34  to drop. The reduction of buoyancy causes the float  32  to tug on the peel-away feature  33 , inducing peel-away and thereby allowing the vapor into the upper chamber  29  and out through the second bypass opening  38  to the vapor recovery passage  20 , establishing a vent-after-closure flow path D 1 , shown partially in  FIG. 4 . This vent-after-closure path D 1  may also be established when a vehicle with the tank  23  is parked on a grade, so that fuel covers the bottom of the housing  34  (i.e., is at level A or higher). 
         [0031]    At another fuel level still at or above predetermined level A, the float  32  drops to a level in which the peel-away feature  33  is not in contact with the housing  34  at opening  15 , as shown in  FIG. 5 , which is taken at a different cross-section than  FIGS. 3 and 4 . The metering valve  44  only partially blocks bypass opening  24 . Vapor flows from vapor space  25  through bypass opening  24  and opening  48  to chambers  31  and  29 , and out through orifice  38  to vapor recovery passage  20  and canister  19 . Flow path D 2  may be referred to as a second grade vent flow path or a second vent-after-closure flow path, occurring after the peel-away feature  33  has completely peeled away from the opening  15 . Flow path D 2  may occur when the tank  23  is on a grade, or anytime the fuel level covers the bottom opening  22  and the fill cap  21  is on. The first grade path D 1  is the same as second grade path D 2 , except that the opening  15  is only partly uncovered by the peel-away feature  33  during venting along flow path D 1 . 
         [0032]    The peel-away feature  33  permits vent-after-closure venting at much higher tank pressures. With the lever affect of the peel-away feature  33 , a higher tank pressure can cause peel-away of the float  32  but could not move a like-size float without a peel-away feature away from opening  15 . Those skilled in the art readily understand the function and operation of a peel-away feature. Other types of float-mounted flow metering features may be used to establish vent-after-closure venting at the same higher pressure and more gradual opening. 
       Run/Loss Flow Path 
       [0033]    Referring again to  FIG. 2 , during vehicle operation with cap  21  on, as fuel level in the tank  23  lowers, the bottom of the housing  34  is eventually uncovered, i.e., fuel falls below predetermined level A to level AA. The float  32  is lowered to the position of  FIG. 2 , and the metering valve  44  thereby closes off the bypass opening  24 . The diaphragm is in the lowered position  36 A. Vapor flows along run/loss flow path E from the tank vapor space  25  through the opening  22  in the bottom of the housing  34 , and up through vapor vent opening  15 . With the diaphragm in the lowered position  36 A, the vapor can only exit through the bypass opening  38  to the vapor recovery passage  20  and on to the canister  19 . 
       Second Embodiment with Vapor Discriminating Feature 
       [0034]    Referring to  FIGS. 6 and 7 , another embodiment of a multi-function control valve assembly  110  is shown (only partially shown in  FIG. 7 ). The valve assembly  110  has many of the same components as valve  10 , and such are numbered in like manner and perform according to the functions described with respect to valve assembly  10 . In particular, a partial tube  158  with an orifice  160  is added between the diaphragm  36 A and the opening  15 . An additional vapor-discriminating float  162  rests on the housing  134  and is added within tube  158  and supported within the housing  134  above the vapor vent opening  15 . During normal run/loss flow, the discriminating float  162  rests on the housing  134  and does not block flow through the orifice  160 . Flow from the vapor space  25  thereby proceeds along flow path F through drain opening  22 , vapor vent passage  15 , opening  160  and opening  39  in the housing  134  to vapor recovery passage  20 . When the diaphragm  36 A is in the lowered position, all venting to passage  20  is through the opening  160 . The tube  158  has an opening  161  (best shown in  FIG. 7 ) larger than opening  160  that is in communication with the lower surface of the diaphragm  36 A and the orifice  40 . Thus, the opening  160  does not affect the recirculation flow to passage  18 , or flow to the vapor recovery passage  20  when the diaphragm is lifted to position  36  (shown with respect to the embodiment of  FIG. 2 ). Should liquid fuel rise above the chamber  131  into chamber  129 , the liquid discriminating valve  162  functions as a cup to cause the liquid to drain back down into chamber  131 . If liquid fills chamber  129 , the valve  162  will close off orifice  160 , as shown in  FIG. 7 , ensuring that no liquid can make it to the vapor recovery passage  20 . 
         [0035]    Thus, the first grade vent flow path occurs with fuel level above the opening  22  and fill cap  21  on, during peel-away of feature  33  from vapor space  25 , through bypass opening  24 , through vent passage  15 , around float  162  and through opening  160  to passage  20 . The second grade vent flow path occurs after the float  32  has dropped and the peel-away feature  33  has completed the peel to open vent passage  15 , and is the same as the first grade vent flow path, with the vent passage  15  completely opened. The recirculation flow path occurring with the fuel level below opening  22  and fill cap on is through opening  22  and chamber  131  through vent passage  15 , through opening  161  of  FIG. 7  and orifice  40  to passage  18 . Primary flow to the canister  19  during filling with the fill cap  21  off and fuel level below the opening  22  is along the same path except under the lifted diaphragm  36  (shown with respect to the embodiment of  FIG. 2 ) to opening  39  and on to passage  20 , instead of through orifice  40 . A run-loss flow path occurring with liquid level below the opening  22  and the fill cap  21  on is through opening  22 , chamber  131 , vapor vent passage  15 , opening  160  and passage  20 . 
         [0036]    The multi-function valve assemblies  10 ,  110  therefore create multiple flow pathways to handle vapor during multiple operating conditions without requiring more than one float valve to control venting from chamber  31  to the upper chamber  29 ,  129 . The metered opening feature, such as peel-away feature  33 , enables the single float  32  to be opened at relatively high pressures to accommodate vent-after-closure/grade vent flow. This reduces the size and complexity of the assembly without sacrificing functionality. 
         [0037]    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.