Abstract:
A Natural Vacuum Leak Detection (NVLD) device having an articulated poppet to allow the sealing surface of the poppet portion to articulate, or wobble, on the end of a poppet pin, where the poppet pin is mounted to the end of the flange portion. The flange portion has the friction spring, and poppet spring pushing on it. The seal surface of the flange portion is able to move to evenly apply force to the lip seal, and provide a full seal. Because the seal surface of the flange portion is able to articulate, or wobble, the flange portion is able to compensate for misalignment between the poppet stem portion and lip seal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to Provisional Patent Application No. 61/506,519, filed Jul. 11, 2011. The disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to an articulating poppet used with a Natural Vacuum Leak Detector (NLVD) device. 
       BACKGROUND OF THE INVENTION 
       [0003]    A known fuel system for vehicles with internal combustion engines includes a canister that accumulates fuel vapor from a headspace of a fuel tank. If there is a leak in the fuel tank, the canister, or any other component of the fuel system, fuel vapor could escape through the leak and be released into the atmosphere instead of being accumulated in the canister. Various government regulatory agencies, e.g., the U.S. Environmental Protection Agency and the Air Resources Board of the California Environmental Protection Agency, have promulgated standards related to limiting fuel vapor releases into the atmosphere. Thus, it is believed that there is a need to avoid releasing fuel vapors into the atmosphere, and to provide an apparatus and a method for performing a leak diagnostic, so as to comply with these standards. 
         [0004]    An automotive leak detection on-board diagnostic (OBD) determines if there is a leak in the vapor management system of an automobile. The vapor management system can include the fuel tank headspace, the canister that collects volatile fuel vapors from the headspace, a purge valve and all associated hoses. A pressure/vacuum sensor or switch allows the engine computer to monitor the vacuum that is caused by the system cooling after the engine has been turned off and thereby performs the leak detection diagnostic. A vacuum relief function provides fail-safe operation of the purge flow system and guarantees that vacuum levels in the fuel tank do not endanger the integrity of the tank both with the engine on and off. 
         [0005]    A pressure relief function is desired in order to “blow off” any excessive fuel vapor immediately after engine shutdown and to facilitate the desired vacuum generation. Another benefit of the pressure relief function is to allow air to exit the tank at high flow rates during tank refueling. This function is commonly known as Onboard Refueling Vapor Recovery (ORVR). 
         [0006]    The pressure relief function is typically achieved through the use of a Natural Vacuum Leak Detector (NLVD), which includes a pressure relief valve having a poppet mounted on the end of a shaft, and a diaphragm. The NLVD functions to relieve excessive negative pressure (vacuum). The poppet and shaft move to change the valve between an open and closed position. The poppet and shaft contact a lip seal when the valve is in the closed position. 
         [0007]    However, there are instances when the poppet may be misaligned relative to the lip seal, potentially causing a leak in the NLVD device. Accordingly, there exists a need for an improved NVLD device that compensates for misalignment between the poppet and the lip seal. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention is an articulated valve for preventing leaks in a natural vacuum leak detection (NLVD) device. The articulated valve includes a poppet stem portion which has a flange portion, and the flange portion has a lower surface and a support surface. The flange portion and an enlarged diameter portion are integrally formed as part of the poppet stem portion, and a lower stem portion is integrally formed with the enlarged diameter portion. A plurality of ribs is integrally formed on the outer surface of the lower stem portion, and a poppet pin is integrally formed with and extending away from the flange portion. The articulated valve also includes a poppet portion. The poppet portion includes a poppet flange selectively in contact with and supported by the flange portion, and a hollowed extension integrally formed with the poppet flange. The flange portion includes a sealing surface, which contacts a seal when the articulated valve is in a closed position. The poppet pin is slidably received into the hollowed extension, allowing the poppet stem portion to articulate relative to the poppet portion. 
         [0009]    It is an object of the present invention to provide an NVLD device having an articulated poppet design to allow the sealing surface of the poppet portion to articulate, or wobble, on the end of a poppet pin, where the poppet pin is mounted to the end of the flange portion. The movement of the flange portion is at least partially controlled by a friction spring, and a poppet spring. The seal surface of the flange portion is able to move to evenly apply force to the lip seal, and provide a full seal. Because the seal surface of the flange portion is able to articulate, or wobble, the flange portion is able to compensate for misalignment between the poppet stem portion and lip seal. 
         [0010]    In an alternate embodiment, a spherical-shaped articulating poppet is used having a spherical-shaped poppet portion, which allows for the poppet portion to articulate relative to the poppet stem portion and achieve an adequate seal between the poppet flange and the lip seal. 
         [0011]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0013]      FIG. 1  is a schematic of a fuel system including an NVLD device having an articulating poppet, according to embodiments of the present invention; 
           [0014]      FIG. 2  is a first sectional side view of an NVLD device having an articulating poppet, according to embodiments of the present invention; 
           [0015]      FIG. 3  is a second sectional side view of an NVLD device having an articulating poppet, according to embodiments of the present invention; 
           [0016]      FIG. 4  is a side view of an articulating poppet, according to embodiments of the present invention; 
           [0017]      FIG. 5A  is a side view of a poppet stem portion, which is part of an articulating poppet, according to embodiments of the present invention; 
           [0018]      FIG. 5B  is a side view of a poppet portion, which is part of an articulating poppet, according to embodiments of the present invention; 
           [0019]      FIG. 6  is a side view of an articulating poppet, where the poppet stem portion is articulated relative to the poppet portion, according to embodiments of the present invention; 
           [0020]      FIG. 7  is a sectional side view of an alternate embodiment of an articulating poppet, according to embodiments of the present invention; 
           [0021]      FIG. 8  is a first perspective view of an alternate embodiment of an articulating poppet, according to embodiments of the present invention; and 
           [0022]      FIG. 9  is a second perspective view of an alternate embodiment of an articulating poppet, according to embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
         [0024]    Referring now to the Figures generally, a Natural Vacuum Leak Detection (NLVD) device having an articulated poppet according to the present invention is part of a fuel system shown generally at  10 . The system  10  includes the NLVD device  12 , a vacuum source  14 , which in this embodiment is an intake of an engine, a purge valve  16 , a charcoal canister  18 , and a fuel tank  20 . 
         [0025]    The NLVD device  12  performs a plurality of functions including signaling  22  that a first predetermined pressure (vacuum) level exists in the headspace of the fuel system  10 , relieving pressure  24  (also referred to as relieving excess vacuum) in the headspace of the fuel system  10  at a value below the first predetermined pressure level, and relieving pressure  26  (also referred to as pressure blow-off) in the headspace of the fuel system  10  above a second pressure level. Relieving pressure  24 , 26  refers to the relieving pressure in the fuel vapor collection canister  18  and throughout the headspace of the fuel system  10  relative to the ambient atmospheric pressure A. 
         [0026]    In the course of cooling that is experienced by the fuel system  10 , e.g., after the engine is turned off, a vacuum is created in the fuel vapor collection canister  18 . The existence of a vacuum at the first predetermined pressure level indicates that the integrity of the fuel system  10  is satisfactory. Thus, signaling  22  is used for indicating the integrity of the fuel system  10 , i.e., that there are no appreciable leaks. Subsequently relieving pressure  24  at a pressure level below the first predetermined pressure level protects the integrity of the fuel tank  20 , i.e., prevents it from collapsing due to vacuum in the fuel system  10 . 
         [0027]    Immediately after the engine is turned off, relieving pressure  26  allows excess pressure due to fuel vaporization to blow off, thereby facilitating the desired vacuum generation that occurs during cooling. During pressure blow-off, air within the fuel system  10  is released while fuel molecules are retained in the fuel vapor collection canister  18 . Similarly, in the course of refueling the fuel tank  20 , relieving pressure  26  allows air to exit the fuel tank  20  at high flow. 
         [0028]    While the engine is turned on, controllably connecting  28  the fuel vapor collection canister  18  to the ambient air A allows confirmation of the purge flow and allows confirmation of the signaling  22  performance. While the engine is turned off, controllably connecting  28  allows a computer for the engine to monitor the vacuum generated during cooling. 
         [0029]      FIGS. 2-6  show an embodiment of the NVLD  12  constructed and arranged to be associated with the charcoal canister  18 . The NVLD  12  includes a housing  30  that can be connected to the body of the charcoal canister  18 . The NVLD  12  provides a configuration having an articulated poppet which improves the sealing function of the poppet, further described below. 
         [0030]    Signaling  22  occurs when vacuum at the first predetermined pressure level is present in the charcoal canister  18 . A pressure operable device, shown generally at  36 , separates an interior chamber in the housing  30 . The pressure operable device  36  includes a diaphragm  38  that is operatively interconnected to a poppet or valve, shown generally at  40 , separates the interior chamber of the housing  30  into a first portion  42  and a second portion  44 . The diaphragm  38  is surrounded by a flexible outer seal  52 , which allows the diaphragm  38  (which is substantially rigid) to move and keep the first portion  42  separate from the separate portion  44 A. The flexible outer seal  52  is connected between an upper half  30 A and a lower half  30 B of the housing  30 . The valve includes two main parts, a plastic poppet stem portion  40 A and a metal poppet portion  40 B. 
         [0031]    The first portion  42  is in fluid communication with the ambient atmospheric pressure through a first port  46 . The second portion  44  is in fluid communication with a second port  48  between housing  30  the charcoal canister  18 . The second portion  44  is also in fluid communication with a separate portion  44 A via signal passageway  50 . Disposed in the signal passageway  50  is a cinter pill  32 , which is a type of filter used for filtering air passing through the signal passageway  50 . 
         [0032]    The force created as a result of vacuum in the separate portion  44 A causes the diaphragm  38  to be displaced upwardly in  FIGS. 2-3 . This displacement is opposed by a resilient element  54 , e.g., a leaf spring. The bias of the resilient element  54  can be adjusted by a calibrating screw  56  such that a desired level of vacuum, e.g., one inch of water, depresses a switch  58  which is electrically connected to an outlet terminal  64  thought the use of a circuit board  34 . As vacuum is released, i.e., the pressure in the portions  44 , 44 A rises, the resilient element  54  pushes the diaphragm  38  away from the switch  58 , whereby the switch  58  resets. 
         [0033]    Pressure relieving  24  occurs as vacuum in the portions  44 , 44 A increases, i.e., the pressure decreases below the calibration level for actuating the switch  58 . Vacuum in the charcoal canister  18  and the second portion  44  continually acts on the valve  40  inasmuch as the first portion  42  is always at or near the ambient atmospheric pressure A. At some value of vacuum below the first predetermined level, e.g., three inches of water, this vacuum overcomes the opposing force of a second resilient element  68  and displaces the valve  40  away from a lip seal  70 . The second resilient element  68  is disposed between a lower surface  60  of the plastic poppet stem portion  40 A, and a bottom surface  62  of the second portion  44 . This displacement opens the valve  40  from a closed position, thus allowing ambient air to be drawn through the first portion  42  into the second portion  44 . Therefore, in an open position of the valve  40 , the first and second ports  46 , 48  are in fluid communication. In this way, vacuum in the fuel system  10  can be regulated. 
         [0034]    A portion of the second resilient element  68  also surrounds an enlarged diameter portion  66 , which provides proper alignment for the resilient element  68 . The poppet stem portion  40 A also includes a lower stem portion  80  integrally formed with the enlarged diameter portion  66 . The lower stem portion  80  is slideably disposed in a restraining tube  78 , and the restraining tube  78  is integrally formed as part of the lower half  30 B of the housing  30 , and extends into the second portion  44 . The restraining tube  78  does not completely surround the lower stem portion  80 , but surrounds approximately two-hundred-seventy degrees (270°) of the lower stem portion  80 . This allows for a friction spring  90  to be in sliding contact with a plurality of ribs  92  formed as part of the lower stem portion  80 . 
         [0035]    The poppet stem portion  40 A also has flange portion  82  which is integrally formed with the enlarged diameter portion  66 . The flange portion  82  includes the lower surface  60  and a support surface  84 . Extending upwardly from the support surface  84  is a poppet pin  86 , and the poppet pin  86  is slidably received into a hollowed extension  88 , formed as part of the metal poppet portion  40 B. Also formed as part of the metal poppet portion  40 B, and surrounding the hollowed extension  88  is a poppet flange  94 , which selectively contacts the lip seal  70  when the valve  40  is in the closed position. The poppet stem portion  40 A and metal poppet portion  40 B are not rigidly connected to each other, but rather the poppet flange  94  is supported by the flange portion  82 , and is selectively in contact with the support surface  84 . The non-rigid connection between the poppet pin  86  and the hollowed extension  88  allows for the metal poppet portion  40 B to articulate relative to the poppet stem portion  40 A, the function of which will be described later. 
         [0036]    According to one embodiment of the present invention, the poppet stem portion  40 A is formed of injection molded plastic and is normally biased toward the lip seal  70  due to the force of the second resilient element  68 . To minimize resonance of the valve  40 , particularly during pressure relieving  24 , a damping movement effect is provided. 
         [0037]    The damping is created via friction between an outer surface  74  of the lower stem portion  80  of the valve  40  and an inner surface  76  of the restraining tube  78  fixed to the housing  30 . To control the force against the inner surface  76  of the restraining tube  78 , the friction spring  90  applies a predetermined amount of force to the lower stem portion  80  of the valve. More specifically, the friction spring  90  and the inner surface  76  of the restraining tube  78  contact the ribs  92  formed as part of the lower stem portion  80 . This provides a desired amount of contact area, which along with the force applied by the friction spring  90 , provides the desired amount of friction. The friction force dampens the motion of the poppet stem portion  40 , which has the effect of stopping resonance during the pressure relieving  24 ,  26 . 
         [0038]    Relieving pressure  26  is provided when there is a positive pressure in the second portion  44 , e.g., when the tank  12  is being refueled. Specifically, the valve  40  is displaced to its open position to provide a very low restriction path for escaping air from the tank  12 . When the charcoal canister  18 , and hence the second portion  44 , experience positive pressure above ambient atmospheric pressure, the signal passageway  50  communicates this positive pressure to the separate portion  44 A. In turn, this positive pressure displaces the diaphragm  38  downward toward the valve  40 . A diaphragm pin  38 A transfers the displacement of the diaphragm  38  to the valve  40 , thereby displacing the valve  40  to its open position with respect to the lip seal  70 . Thus, pressure in the charcoal canister  18  due to refueling is allowed to escape through the lower portion  44 , past the lip seal  70 , through the first portion  42 , and through the second port  46 . 
         [0039]    Relieving pressure  26  is also useful for regulating the pressure in fuel tank  20  during any situation in which the engine is turned off. By limiting the amount of positive pressure in the fuel tank  20 , the cool-down vacuum effect takes place sooner. 
         [0040]    Due to various manufacturing tolerances, and variations which may occur during the manufacturing process, the restraining tube  78 , and more particularly the inner surface  76  of the restraining tube  78 , may not be oriented to provide proper alignment between the valve  40  and the lip seal  70 . The non-rigid or articulating connection between the metal poppet portion  40 B and the poppet stem portion  40 A allows for the metal poppet portion  40 B to provide a complete seal between the poppet flange  94  and the lip seal  70 , completely closing the valve  40 . This compensates for any misalignment between the valve  40  and the lip seal  70  caused by the restraining tube  78  being formed improperly. An example of the articulation between the poppet stem portion  40 A and the metal poppet portion  40 B is shown in  FIGS. 4 and 6 . The diameter of the poppet pin  86  is smaller than the inner diameter of the hollowed extension  88 , which facilitates the articulation between the poppet stem portion  40 A and the metal poppet portion  40 B, but still allows for a full seal connection between the poppet flange  94  and the lip seal  70 , as well as allowing the lower stem portion  80  to be in full sliding contact with the inner surface  76  of the restraining tube  78 . 
         [0041]    Another embodiment of the present invention is shown in  FIGS. 7-9 , with like numbers referring to like elements. However, in this embodiment, the poppet flange  94  is a spherical poppet flange  94 , which is selectively in contact with the lip seal  70 . The spherical poppet flange  94  compensates for various changes in position of the poppet stem portion  40 A and metal poppet portion  40 B relative to the lip seal  70 . The poppet stem portion  40 A may be located at various angles, but because of the spherically shaped spherical poppet flange  94 , the spherical poppet flange  94  remains in contact with the lip seal  70  such as to form a complete seal when the valve  40  is in a closed position. 
         [0042]    Although the substantially flat poppet flange  94  and spherical poppet flange  94  have been described in the various embodiments, it is within the scope of the invention that the poppet flange  94  may be other shapes as well, and still provide an adequate sealing function with the lip seal  70 . 
         [0043]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.