Abstract:
An isolation valve includes a flow restrictor disposed in a passage and having a piston with a first orifice and a depressurization valve with a second orifice. The valve also includes a solenoid valve assembly having a coil that is selectively energized by a signal from a controller and an armature that is moveable between first and second positions to open and close the first orifice and/or the second orifice. When the coil is energized, the armature moves to the second position to allow vapor to flow through the first orifice, the depressurization valve selectively opens to allow vapor to flow through the first orifice, the second orifice, or both. The two orifices work together to provide controlled vapor flow.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 12/749,924 filed on Mar. 30, 2010. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a valve assembly for controlling fluid flow to and from a high-pressure fuel tank, and more particularly to such a valve assembly that can be depressurized quickly. 
       BACKGROUND OF THE INVENTION 
       [0003]    High-pressure fuel tanks may use an isolation valve to open and close a vapor path between the fuel tank and a purge canister. In a typical evaporative emissions system, vented vapors from the fuel system are sent to a purge canister containing activated charcoal, which adsorbs fuel vapors. During certain engine operational modes, with the help of specifically designed control valves (e.g., vapor vent valves), the fuel vapors are adsorbed within the canister. Subsequently, during other engine operational modes, and with the help of additional control valves, fresh air is drawn through the canister, pulling the fuel vapor into the engine where it is burned. 
         [0004]    For high-pressure fuel tank systems, an isolation valve may be used to isolate fuel tank emissions and prevent them from overloading the canister and vapor lines. The isolation valve itself may be a normally closed valve that is opened to allow vapor flow for tank depressurization or any other event where vapor release is desired. The vapor flow rate may be controlled to, for example, prevent corking of vent valves elsewhere in the emissions system. 
         [0005]    There is a desire for an isolation valve that can be used in high-pressure fuel tanks and that can depressurize quickly in a controlled manner to allow user access to the fuel tank within a reasonable amount of time. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    An isolation valve according to one embodiment includes a flow restrictor disposed in a passage and having a piston with a first orifice and a depressurization valve with a second orifice. The valve also includes a solenoid valve assembly having a coil that is selectively energized by a signal from a controller and an armature that is moveable between first and second positions to open and close the first orifice and/or the second orifice. When the coil is energized, the armature moves to the second position to allow vapor to flow through the first orifice, and the depressurization valve selectively opens to allow vapor to flow through the first orifice, the second orifice, or both. The two orifices work together to provide controlled vapor flow. 
         [0007]    An isolation valve according to another embodiment includes a flow restrictor disposed in a passage having sloped sides and having an orifice. A flow restrictor spring applies a biasing force on the flow restrictor to bias the flow restrictor to an open position. The valve also includes a solenoid valve assembly having a coil that is selectively energized by a signal from a controller, and an armature that is moveable between an extended position that overcomes the biasing force of the restrictor spring to move the flow restrictor to a closed position and to close the second orifice and a retracted position to open the orifice. When the coil is energized, the armature moves to the retracted position to allow vapor to flow through the orifice until the biasing force of the flow restrictor spring overcomes a vapor pressure. The depressurization valve opens to allow vapor to flow through the orifice and/or a space between the flow restrictor and the passage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a cross-sectional view of a valve assembly configured for controlling fuel vapor flow between a fuel tank and a purge canister, with the valve shown in a completely closed state, according to one embodiment of the invention; 
           [0009]      FIG. 1A  is a magnified cross-sectional view of a depressurizing valve according one embodiment of the invention; 
           [0010]      FIG. 2  is a cross-sectional view of the valve assembly shown in  FIG. 1  when a solenoid in the valve assembly is energized during a start of a depressurization process conducted before refueling of the fuel tank; 
           [0011]      FIG. 3  is a cross-sectional view of the valve assembly shown in  FIG. 1  when the solenoid is energized and the depressurizing valve is in an open position while the flow restrictor is in a closed position; 
           [0012]      FIG. 4  is a cross-sectional view of the valve assembly shown in  FIG. 1  where both the depressurizing valve and the flow restrictor are both in an open position; 
           [0013]      FIG. 5  is a cross-sectional view of a valve assembly according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]      FIG. 1  illustrates a fuel system, schematically represented by numeral  10 . The system  10  includes a fuel tank  12  and a controller  14  that may regulate the operation of an engine (not shown) and its fuel delivery system (not shown). Fuel tank  12  is operatively connected to an evaporative emissions control system that includes a purge canister  18  that may collect fuel vapor from the fuel tank  12  and subsequently release the fuel vapor to the engine. In addition, controller  14  may regulate the operation of a valve assembly  20  to selectively open and close the valve assembly  20 , providing over-pressure relief and vacuum relief for the fuel tank  12   
         [0015]    The valve assembly  20  itself may control fuel vapor flow between the fuel tank  12  and the purge canister  18 . Although the valve assembly  20  shown in the figures is located between the fuel tank  12  and the purge canister  18 , nothing precludes locating the valve assembly  20  from being located elsewhere, such as between the purge canister  18  and the engine. 
         [0016]    The valve assembly  20  may include a housing  22  that retains internal components of the valve assembly  20  in a compact manner. The valve assembly  20  may include a relief valve  28 . The relief valve  28  may includes a piston  30 , which may be formed from a suitable chemically-resistant material such as an appropriate plastic or aluminum. The relief valve  28  may also include a compliant seal  32 , which may be formed from a suitable chemically-resistant elastomeric material. During operation, the seal  32  makes initial contact with the housing  22  along the seal&#39;s outer edge. After the initial contact with housing  22 , the outer edge of seal  32  deflects to conform to the housing and seal a passage  34 . 
         [0017]    The piston  30  and the seal  32  may be combined into a unitary piston assembly via an appropriate manufacturing process, such as overmolding, as understood by those skilled in the art. The piston  30  and the seal  32  may be biased to close the passage  34 . A spring  36  or other resilient member may bias the piston and the seal  32 . The relief valve  28  may generally be used to open a vapor path between the fuel tank  12  and the purge canister  18  to relieve an extreme or over-pressure condition in the fuel tank  12 . Additional details of the operation of the relief valve  28  in conjunction with the rest of the valve assembly  20  are described in commonly-assigned, co-pending U.S. patent application Ser. No. 12/749,924 filed on Mar. 30, 2010, the disclosure of which is incorporated by reference herein in its entirety. For purpose of the present application, the relief valve  28  and its operation are for illustrative purposes only and are not considered part of the present invention. 
         [0018]    The description below will now focus on operation of the valve assembly  20 , and particularly a solenoid assembly  40  and components that operate in conjunction with it, during a depressurization operation prior to refueling. 
         [0019]    The solenoid assembly  40  includes an armature  42 , a solenoid spring  44 , and a coil  46 . The energization and de-energization of the coil  46  may be controlled by a signal from the controller  14 . The solenoid spring  44  may generate a force sufficient to urge the armature  42  out of the solenoid assembly  40  when the coil  46  is not energized. When the coil  46  is energized, the resulting magnetic forces overcome the biasing force of the solenoid spring  44  and pull the armature  42  into the solenoid assembly  40 , exposing a small orifice  49  in a flow restrictor  50  to allow vapor flow through the orifice  49  ( FIG. 2 ). 
         [0020]    In one embodiment, the flow restrictor  50  is arranged inside the housing  22  and includes a piston portion  52 , which may be formed from a suitable chemically-resistant material such as an appropriate plastic or aluminum. The flow restrictor  50  may also include a compliant seal  55 , which may be formed from a suitable chemically-resistant rubber. During valve operation, the seal  55  may initially contact the housing  22  along the seal&#39;s outer edge. After initial contact with the housing  22 , the outer edge of seal  55  may deflect to conform to the housing  22  and hermetically close a passage  56  leading to the canister connector  26 . 
         [0021]    In one embodiment, the size of the small orifice  49  in the flow restrictor  50  is selected to allow only a selected amount of flow at a maximum specified tank pressure because the size of the passage  56  is too large to prevent “corking.” More particularly, without the small orifice  49  slowing vapor flow through the passage  56 , the force from rushing fuel vapors may force other valves in the system  10 , such as a fuel limit vent valve (not shown) in the fuel tank  12 , to “cork” into a closed position. Thus, the reduced size of the small orifice  49  in the flow restrictor  50  controls the vapor flow to a level that prevents corking. Note that vapor control may be desired for other purposes as well without 
         [0022]    Referring again to  FIG. 2 , when a user wishes to refuel the tank, the user may wish to depressurize the fuel tank first so that the potentially high pressure in the tank  12  is lowered to a specified acceptable level. However, the size of the small orifice  49  may restrict the vapor flow rate to a level that is not high enough to depressurize the tank in a reasonable amount of time. On the other hand, allowing unrestricted vapor flow through the isolation valve  10  may cause other valves in the system to cork, as explained above. 
         [0023]    To provide closer control over vapor flow, the flow restrictor  50  may include a depressurization valve  50   a,  as shown in  FIG. 1A , to allow faster tank depressurization. The depressurization valve  50   a  may be a poppet valve, wherein the small orifice  49  is in the poppet valve rather than the piston  52 . The depressurization valve  50   a  may have its own associated seal  57  that seats against the piston  52 . In this embodiment, the depressurization valve  50   a  is disposed in an intermediate orifice  50   b  in the piston  52 . In one embodiment, the size of the intermediate orifice  50   b  is selected to allow increased vapor flow while still limiting the flow enough to prevent corking of fuel venting valves. The depressurization valve  50   b  is biased toward an open position by a depressurization spring  50   c  supported by the piston  52 . In one embodiment, the spring  50   c  has a biasing force that is greater than the spring  54  biasing the flow restrictor  50  itself. 
         [0024]    As a result, the flow restrictor  50  has two effective orifice sizes that may be opened when the solenoid assembly  40  is energized: (1) a small orifice  49  in the depressurization valve  50   a  that ensures vapor flow rate between the tank and the canister is less than a maximum flow rate to prevent corking of fuel tank venting valves during normal valve operation and (2) an intermediate orifice  50   b  in the piston  52  that, in combination with the small orifice  49 , allows faster tank depressurization before a refueling operation. Also, the difference in biasing forces between the springs  54 ,  50   c  allows the depressurization valve  50   b  to open at a given vapor pressure while the flow restrictor  50  remains in a closed position, thereby allowing vapor to flow simultaneously through the small orifice  49  and the intermediate orifice  50   b.  The specific application of these features will be explained in greater detail below. 
         [0025]    In one embodiment of the invention, a user may depressurize the tank by, for example, pushing a button on the interior of the vehicle to send a control signal from the controller  14 . The signal energizes the coil  46 , creating a magnetic force that withdraws the armature  42  to open the small orifice  49  and create a flow path through the flow restrictor  50  and the passage  56 . Due to the high vapor flow rate created by the high tank pressure, there is enough initial force generated by the vapor flow to compress both springs  54 ,  50   c,  keeping the piston  52  and the depressurization valve  50   a  pushed downward against the large passage  56  and restricting flow only through the small orifice  49 . 
         [0026]    Referring to  FIG. 3 , since the spring force of the depressurization spring  50   c  biasing the depressurization valve  50   a  to an open position is larger than the spring force of the restrictor spring  54  biasing the flow restrictor  50  to an open position, and since the vapor pressure drops soon after a small amount of vapor escapes through the small orifice  49 , the depressurization spring  50   c  forces the depressurization valve  50   a  to an open position, increasing the amount of vapor flow by creating two flow paths, one through the small orifice  49  and one through the intermediate orifice  50   b  (in the space between the depressurization valve  50   a  and the piston  52 ), out of the tank. The larger size of the intermediate orifice  50   b  allows an increased flow rate out of the tank, thereby allowing the tank to depressurize to a desired level quicker than through the small orifice  49  alone. 
         [0027]    Referring to  FIG. 4 , the vapor pressure may drop low enough so that the restrictor spring  54  overcomes the vapor pressure from the tank and pushes the flow restrictor  50  open as well, opening a flow path through the large passage  56 . As shown in  FIG. 4 , the large passage  56  is exposed when armature  42  is withdrawn into solenoid assembly  40  in response to a tank depressurization signal noted above. This combination of lower tank pressure and withdrawn armature  42  allows the restrictor spring  54  to extend, pushing the flow restrictor  50  upward against the armature  42  to close the small orifice  49  and intermediate orifice  50   b  and open the large passage  56 . At this point, there is no danger of corking in the fuel vent valves because the tank pressure is low enough to keep the vapor flow at a lower level during the final stages of the tank depressurization process. 
         [0028]    As a result, the varying opening sizes  49 ,  50   b,    56 , used both alone and in combination, and the different biasing forces of the springs  44 ,  50   c  provide fast, yet controlled, tank depressurization while still keeping the vapor flow rate low enough to prevent corking of fuel vent valves in the emissions system. 
         [0029]      FIG. 5  shows an alternative embodiment for increasing the vapor flow rate through the valve assembly  20 . This embodiment omits a separate depressurization valve and additional orifice sizes. Instead, this embodiment modifies the configuration of the passage  56  and the characteristics of the restrictor spring  54  to allow the vapor flow to increase gradually through the passage  56 . 
         [0030]    More particularly, the passage  56  may be funnel-shaped. When the coil  46  is initially energized to initiate tank depressurization, the armature  42  withdraws into the solenoid assembly  40 , allowing vapor to initially flow through the small orifice  49 . As the vapor pressure drops, the biasing force of the restrictor spring  54  lifts the piston  52  from the passage  56  to allow some of the vapor to bypass the flow restrictor  50  directly into the passage  56 . However, the funnel shape of the passage  56  restricts the amount of vapor flowing through the passage  56 , thereby preventing corking of the fuel vent valves. The restrictor spring  54  gradually forces the flow restrictor  50  up the funnel-shaped passage  56  to a wider point, which allows even more vapor to flow under the flow restrictor  50  into the passage. 
         [0031]    In other words, the shape of the passage itself, in combination with the piston  52  diameter, naturally creates a passage with a variable size to control vapor flow. Thus, the combination of the funnel-shaped passage  56  and the selected biasing force of the restrictor spring  54  against the piston  52  gradually adjusts the amount of vapor released from the fuel tank while adjusting the vapor flow rate via the position of the flow restrictor  50  in the funnel-shaped passage to prevent corking of fuel vent valves in the emissions system. 
         [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.