Abstract:
A valve assembly providing flow control between a fuel tank and a carbon canister, which includes two valves providing two different flow paths, where the first valve provides active vacuum relief along the first flow path, and the second valve provides passive vacuum relief along the second flow path. A reservoir is added to the cap which is common for both flow paths. The second valve has a sealing valve member and a biasable member that passively relieves fuel tank vacuum pressure at a predetermined vacuum level.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/988,619 filed May 5, 2014. The disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates generally to a valve assembly having at least two valves located in parallel to provide two flow paths for air and fuel vapor, where one of the valves provides passive relief of vacuum pressure in one direction. 
       BACKGROUND OF THE INVENTION 
       [0003]    Carbon canisters are generally known, and are used for capturing and storing vapor from a fuel tank, which is transferred to the engine through a canister purge valve. Typically, these fuel tanks are open to atmosphere via the carbon canister, thereby keeping the tank pressure near atmospheric pressure at all times. In newer, sealed tank systems, the fuel tank is isolated from the canister, and is capable of storing vapor under pressure, or vacuum, to a set pressure/vacuum level. The amount of fuel in the fuel tank varies as the fuel is consumed during vehicle travel, and during refueling at a service station. During vehicle travel, the amount of fuel in the fuel tank is decreased, creating vacuum pressure in the fuel tank. In a sealed tank system, this vacuum pressure must be relieved to eliminate the possibility of collapsing the tank. Approaches to relieving this vacuum pressure have included a solenoid having a valve which controls the amount of air flow back into the tank under vacuum pressure conditions, and the flow of fuel vapor to the carbon canister. 
         [0004]    Some of these canister purge valves use short pulses to open and close the valve rapidly to keep the vapors contained in the tank as much as possible, while also providing vacuum relief. While this approach provides controlled vacuum relief, it does not provide for passive (uncontrolled) vacuum relief, separately from the flow control. 
         [0005]    Accordingly, there exists a need for a valve assembly which is able to provide active and passive relief of vacuum pressure in a fuel tank. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is a valve assembly which includes an additional valve and flow path to allow for vacuum relief to be performed separately from the flow control, which improves control of flow and the pressure level where vacuum is relieved. 
         [0007]    The present invention uses a valve assembly for flow control, and adds a second flow path with a second valve having a sealing disk and spring assembly that relieves fuel tank vacuum pressure at a predetermined vacuum level. A reservoir is added to the cap which is common for both flow paths. The second flow path for vacuum relief provides good control of armature travel and thus flow. The valve design of the present invention uses a second flow path to provide precise vacuum relief. 
         [0008]    In one embodiment, the present invention is a valve assembly, which includes an overmold assembly having an overmold assembly cavity, a cap having a cap aperture, the cap being connected to the overmold assembly, and a reservoir having a reservoir cavity, where the reservoir is connected to the cap. A first valve is mounted in the overmold assembly and selectively places the overmold assembly cavity in fluid communication with the reservoir cavity. A second valve is mounted to the cap and selectively places the overmold assembly cavity in fluid communication with the reservoir cavity. The first valve and the second valve provide parallel flow paths between the overmold assembly cavity and the reservoir cavity, such that the first valve provides active vacuum relief of the overmold assembly cavity, and the second valve provides passive vacuum relief of the overmold assembly cavity. 
         [0009]    The first valve includes an armature and a valve seat. The valve seat is formed as part of the cap such that the valve seat substantially surrounds the cap aperture. The armature is selectively in contact with the valve seat to actively control the flow of air and purge vapor through the cap aperture between the overmold assembly cavity and the reservoir cavity. 
         [0010]    The second valve includes a valve plate selectively in contact with a valve seat, and a guide member integrally formed with the valve plate. The guide member has a notch, and the guide member is slidably disposed within an aperture formed as part of the cap. A spring is in contact with the guide member and the cap, and a portion of the spring is located in the notch such that the spring applies force to the cap and the notch, biasing the valve plate to towards the valve seat. The valve plate is in contact with the valve seat when the vacuum pressure in the overmold assembly cavity is less than the force applied to the notch by the spring, and when the vacuum pressure in the overmold assembly cavity is greater than the force applied to the notch by the spring, the valve plate moves away from the valve seat, placing the second valve in the open position, reliving the vacuum pressure in the overmold assembly cavity. 
         [0011]    At least one flange is formed as part of the guide member, and an aperture is formed as part of the cap. However, multiple flanges circumscribing the guide member function to guide the movement of the valve plate. The guide member moves through the aperture as the valve is moved towards and away from the valve seat. When the valve is moved away from the valve seat, air and purge vapor are able to flow through the aperture and around the flanges between the overmold assembly cavity and the reservoir cavity. 
         [0012]    In one embodiment, the overmold assembly cavity is in fluid communication with a gas tank, and the first valve and the second valve provide vacuum relief to the gas tank. The second valve provides passive vacuum relief such that when the vacuum pressure in the overmold assembly cavity is less than the force applied to the notch by the spring, the second valve is in the closed position. When the vacuum pressure in the overmold assembly cavity is greater than the force applied to the notch by the spring, the valve plate moves away from the valve seat, placing the second valve in the open position, relieving the vacuum pressure in the overmold assembly cavity. 
         [0013]    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 
         [0014]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0015]      FIG. 1  is a diagram of an air flow system having a valve assembly, according to embodiments of the present invention; 
           [0016]      FIG. 2  is a sectional side view of a valve assembly, according to embodiments of the present invention; and 
           [0017]      FIG. 3  is partial cutaway view of a valve assembly, according to embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    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. 
         [0019]    A diagram of a portion of an airflow system of a vehicle having a valve assembly according to the present invention is shown generally at  10 . The system  10  includes a carbon canister  12  in fluid communication with the atmosphere through the use of a first conduit  20   a . The system  10  also includes a second conduit  20   b  which is in fluid communication with the carbon canister  12 , and also a refueling valve  14  and a TPC valve assembly  16 . There is a third conduit  20   c  which is connected to and provides fluid communication between a fuel tank  18  and both the refueling valve  14  and the valve assembly  16 . There is also a fourth conduit  20   d , which is connected to the carbon canister  12  and provides fluid communication between the carbon canister  12  and the remaining components of the air flow system  10 , represented at  22 . 
         [0020]    Referring to  FIGS. 2-3 , the valve assembly  16  includes a first port  24  connected to the third conduit  20   c . The valve assembly  16  also includes an overmold assembly  26 , and disposed within the overmold assembly  26  is a first valve, shown generally at  28 , which in this embodiment is a solenoid assembly. The solenoid assembly  28  is disposed within a cavity, shown generally at  30 , formed as part of the overmold assembly  26 , and the cavity  30  includes an inner wall portion  32 , and also forming part of the cavity  30  is an outer wall portion  34  of the overmold assembly  26 . 
         [0021]    The solenoid assembly  28  includes a stator insert  36  which surrounds a support  38  formed as part of the overmold assembly  26 . The overmold assembly  26  has an upper wall  42 , and in contact with the upper wall  42  is a bobbin  44 . The bobbin  44  is surrounded by a coil  46 , and two straps (not shown) surround the coil  46 . There is a sleeve  50  which is surrounded by the bobbin  44 , and the sleeve  50  partially surrounds a moveable armature  52 . The armature  52  includes a cavity, shown generally at  54 , and located in the cavity  54  is a spring  56 , which is in contact with an inner surface  58  of the cavity  54 . The spring  56  is also mounted on a narrow diameter portion  60  of the support  38 . Disposed between part of the armature  52  and the bobbin  44  is a second washer  62 . Connected to the overmold assembly  26  is a cap  64 , and formed as part of the cap  64  is a valve seat  66  and a cap aperture  68 , where purge vapor is able to flow from an overmold assembly cavity, shown generally at  70 , formed as part of the overmold assembly  26 , and through the cap aperture  68 . The first port  24  provides fluid communication between the overmold assembly cavity  70  and the third conduit  20   c.    
         [0022]    The armature  52  includes a stopper portion  72  which is made of a rubber or other flexible material. The stopper portion  72  includes a contact surface  74  which contacts the valve seat  66  when the armature  52  is in the closed position. The stopper portion  72  includes a plurality of post members  76 , which are of the same durometer, but are of different sizes, and therefore have different levels of stiffness. The largest post members  76  are in contact with the bottom surface of the washer  62  when the armature  52  is in the closed position, as shown in  FIG. 2 . The smaller post members  76  contact the bottom surface of the washer  62  when the armature  52  moves to the open position. The more the coil  46  is energized, the further the armature  52  moves away from the valve seat  66 , and the greater number of post members  76  contact the bottom surface of the washer  62 . The movement of the armature  52  to open and close the solenoid assembly  28  controls the amount of air allowed to pass through the valve assembly  16 , and into the fuel tank  18 . 
         [0023]    Because the post members  76  are made of rubber, the post members  76  are able to deform as the armature  52  is moved further away from the valve seat  66 . The largest post members  76  in contact with the bottom surface of the washer  62  deform first when the armature  52  moves away from the valve seat  66 . As the armature  52  moves further away from the valve seat  66 , more of the post members  76  contact the bottom surface of the washer  62 , and then begin to deform as the armature  52  moves even further away from the valve seat  66 . The deformation of the post members  76  (when the armature  52  is moved to the open position away from the valve seat  66 ) functions to dampen the movement of the armature  52 , eliminating noise, and preventing metal-to-metal contact between the armature  52  and the stator insert  36 . 
         [0024]    Disposed between the bottom surface of the washer  62  and an inside surface  78  of the cap  64  is a filter  80 . The filter  80  is made of several blades of plastic which are adjacent one another. The filter  80  is designed to limit the size of debris and particles passing through the blades of plastic to less than 0.7 millimeters. The distance between the armature  52  and the stator insert  36  is about 1.0 millimeter when the armature  52  is in the closed position, and is the maximum allowable distance between the contact surface  74  of the stopper portion  72  and the valve seat  66 . The filter  80  ensures that no particles may pass through the filter  80  that are too large to affect the functionality of the solenoid assembly  28  (the particles being too large to fit between the valve seat  66  and the stopper portion  72 ) when the armature  52  is in the open position. 
         [0025]    The aperture  68  is also in fluid communication with a reservoir cavity, shown generally at  82 , formed as part of a reservoir  84 . The reservoir  84  is connected to the cap  64 , and a second port  86  is formed as part of the reservoir  84 . The second port  86  places the reservoir cavity  82  in fluid communication with the second conduit  20   b . Connected to the cap  64  is a second valve, shown generally at  88 , which is located in the overmold assembly cavity  70 . The second valve  88  includes a valve member  90 , which in this embodiment is a valve plate  90 , selectively in contact with a valve seat  92 . The valve plate  90  is integrally formed with a guide member  94 , and the guide member  94  includes a notch  96 , and the first end of a spring  98  is located in the notch  96 , and the second end of the spring  98  is in contact with a flange portion  100  formed as part of the cap  64 , such that the spring  98  biases the valve plate  90  towards the valve seat  92 . 
         [0026]    The valve seat  92  is formed as part of the flange portion  100 , and also formed as part of the flange portion  100  is an aperture  102 , where the guide member  94  moves through the aperture  102  as the plate  90  moves towards and away from the valve seat  92 . The guide member  94  includes a plurality of flanges  104 , which allow for the passing of air and purge vapor when the valve plate  90  is not in contact with the valve seat  92 . 
         [0027]    Both the first valve  28  and the second valve  88  are in fluid communication with the overmold assembly cavity  70  and the reservoir cavity  82 . The first valve  28  is used to provide controlled flow of air and purge vapor through the valve assembly  16 , and therefore provide active vacuum relief, and the second valve  88  is used to provide passive vacuum relief. 
         [0028]    In operation, the refueling valve  14  is opened when the fuel tank  18  is being refueled, and closed during other times of the operation of the vehicle. During operation of the vehicle, as fuel is consumed by the engine, the fuel level in the fuel tank  18  decreases, creating vacuum pressure in the fuel tank  18 , which also results in vacuum pressure in the third conduit  20   c  and the overmold assembly cavity  70 . During one mode of operation, the solenoid assembly  28  moves the armature  52  and stopper portion  72  away from the valve seat  66 , such that air passes from the second port  86 , through the reservoir cavity  82 , the cap aperture  68 , into the overmold assembly cavity  40 , the first port  24 , the third conduit  20   c , and into the fuel tank  18 . 
         [0029]    As mentioned above, the second valve  88  is able to provide passive vacuum relief. When there is vacuum pressure in the fuel tank  18 , the third conduit  20   c  and the overmold assembly cavity  70  are also under vacuum pressure as well. If the vacuum pressure reaches a predetermined level, the vacuum pressure applied to the valve plate  90  overcomes the force of the spring  98  applied to the valve plate  90 , and moves the valve plate  90  away from the valve seat  92 , placing the second valve  88  in an open position. When the second valve  88  is in the open position, air is allowed to pass from the reservoir cavity  82 , through the second valve  88 , the overmold assembly cavity  70 , through the first port  24 , the third conduit  20   c , and into the fuel tank  18 . The air passes through the second valve  88  by flowing between the flanges  104  and through the aperture  102  when the valve plate  90  is not in contact with the valve seat  92 . The air reaches the reservoir cavity  82  by flowing into the first conduit  20   a  from the atmosphere, through the carbon canister  12 , the fourth conduit  20   d , and through the second port  86 . 
         [0030]    Another function of the valve assembly  16  is the relief of vacuum pressure in the canister  12  and the fuel tank  18  of the vehicle after the vehicle is shut off. Due to fuel consumption over time, the fuel flows out of the fuel tank to the engine, creating vacuum pressure in the fuel tank  18  and the canister  12 . The valve assembly  16  is capable of relieving this vacuum pressure. To relieve the vacuum pressure, the solenoid assembly  28  is pulsated after the vehicle is shut off. In one embodiment, the solenoid assembly  28  is pulsated at 10 Hz, but it is within the scope of the invention that the solenoid assembly  28  may be pulsated at other frequencies. This pulsation allows for air to flow from the second port  86  through the reservoir cavity  82 , the cap aperture  68 , into the overmold assembly cavity  40 , the first port  24 , the third conduit  20   c , and into the fuel tank  18 . 
         [0031]    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.