Abstract:
An integrated valve assembly, which integrates two check valves and a solenoid assembly which functions as a purge valve. When the solenoid assembly is in an open position, during a first mode of operation, vacuum pressure places the first check valve in an open position and the second check valve in a closed position, and during a second mode of operation, pressurized air places the first check valve in a closed position, and vacuum pressure generated by a venturi valve member places the second check valve in an open position. Each check valve utilizes a nylon insert along with an over molded rubber seal. The design of the check valves prevents actuation at low vacuums and flows when the vehicle is shut off. The integrated valve assembly eliminates the need for an OBD relief valve, and simplifies the EVAP system, saving costs, complexity, and eliminates several possible leak connections.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/815,079 filed Apr. 23, 2013. The disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates generally to an integrated valve assembly which is capable of providing venting from a carbon canister, as well as providing venting from the fuel EVAP system during on-board diagnostic testing. 
     BACKGROUND OF THE INVENTION 
     Purge systems are generally known and are used in different types of vehicles. Some types of turbo purge systems in vehicles equipped with turbocharging units use two check valves located remotely from a turbo purge valve to control turbo pressure and intake vacuum respectively to supply a source vacuum to a canister purge valve. The pressurized air generated by the turbocharger is forced into the engine to increase combustion pressure, and therefore increase the power generated by the engine. With some tubocharging systems, a portion of the pressurized air is bled off to create a vacuum and induce flow of purge vapor. The vacuum created is used as part of a purge system, where the purge system directs purge vapors from a fuel tank through various conduits to redirect the vapors into the intake manifold of the engine, and burn off these vapors through combustion. 
     The types of check valves used in these systems commonly check at very low vacuum pressure levels. Because these check valves check at such low vacuum pressure, it is difficult to use these valves to vent the fuel tank system and stabilize to atmospheric conditions prior to initiating the small leak test for on-board diagnostic (OBD) compliance. 
     To overcome this issue, these types of systems typically require a separate OBD relief valve to vent the fuel evaporative emissions (EVAP) system when the vehicle is shut off. The valve is necessary to conduct the OBD test. However, the inclusion of this valve adds complexity and cost to the system. 
     Accordingly, there exists a need for a valve assembly which is able to vent the fuel tank system, and allow the fuel tank system to stabilize to atmospheric conditions, as well as perform an OBD test, and control turbo pressure and intake vacuum pressure supplied to a turbo purge valve. 
     SUMMARY OF THE INVENTION 
     The present invention is an integrated valve assembly, which integrates two check valves and a purge valve. Each check valve utilizes a nylon insert along with an over molded rubber seal. The added mass and design of the check valves prevents actuation at low vacuums and flows when the vehicle is shut off. 
     To further accelerate EVAP system bleed down, drive software pulses the purge valve to create a pressure differential across the purge valve, and the resulting pressure pulses provide momentum to the check valves because of the increased mass and design of the check valves, which prevents checking. 
     The integrated valve assembly of the present invention eliminates the need for an OBD relief valve, and simplifies the EVAP system, saving costs, complexity, and eliminates several possible leak connections. 
     In one embodiment, the present invention is a turbo purge valve assembly which includes an overmold assembly having an overmold assembly cavity, a solenoid assembly located in the overmold assembly adjacent the overmold assembly cavity, a cap connected to the overmold assembly, a reservoir connected to the cap, and a reservoir cavity formed as part of the reservoir. A cap aperture is formed as part of the cap, such that the cap aperture provides fluid communication between the overmold assembly cavity and the reservoir cavity when the solenoid assembly is in an open position. The turbo purge valve assembly also includes a first check valve connected to the reservoir and in fluid communication with an intake manifold and the reservoir cavity, and a second check valve connected to the reservoir and in fluid communication with a venturi valve member and the reservoir cavity. 
     During a first mode of operation and when the solenoid assembly is in an open position, vacuum pressure places the first check valve in an open position and the second check valve in a closed position. During a second mode of operation and when the solenoid assembly is in an open position, pressurized air places the first check valve in a closed position, and vacuum pressure generated by the venturi valve member places the second check valve in an open position. 
     The first check valve includes a first valve plate moveable between an open position and a closed position, a first seal member connected to and circumscribing the first valve plate, and a first valve seat selectively in contact with the first seal member. A first check valve aperture is in fluid communication with the reservoir cavity, and the first check valve aperture is at least partially surrounded by the first valve seat. The first check valve also includes a first base portion, a first inner wall formed as part of the first base portion, and the first seal member is selectively in contact with the first inner wall. The first check valve also has a first plurality of vents formed as part of the first base portion, and a first check valve cavity, the first plurality of vents and the first check valve aperture are in fluid communication with the first check valve cavity. A first vent port is integrally formed with the first base portion, and a first guide member at least partially extends into the reservoir cavity and partially extends into the first vent port, and the first valve plate is integrally formed with the guide member. 
     The first valve plate is located in the first check valve cavity, and during the first mode of operation, the first valve plate is exposed to vacuum pressure from the intake manifold, which causes the first valve plate to move toward and contact the first inner wall, placing the first check valve is in the open position, allowing purge vapor to flow from the reservoir cavity through the first check valve aperture, through the first check valve cavity, and through the first plurality of vents and out of the first vent port. During the second mode of operation, pressurized air places the first valve plate in contact with the first valve seat, preventing purge vapor from entering the first check valve cavity from the reservoir cavity. 
     The second check valve is constructed similarly to the first check valve, and the second check valve includes a second valve plate moveable between an open position and a closed position, a second seal member connected to and circumscribing the second valve plate, and a second valve seat selectively in contact with the second seal member. A second check valve aperture is in fluid communication with the reservoir cavity, and the second check valve aperture surrounded by the second valve seat. The second check valve also includes a second base portion, a second inner wall formed as part of the second base portion, and the second seal member is selectively in contact with the second inner wall. The second check valve also includes a second plurality of vents formed as part of the second base portion, and a second check valve cavity, the second plurality of vents and the second check valve aperture are in fluid communication with the second check valve cavity. A second vent port is integrally formed with the base portion, and a second guide member at least partially extends into the reservoir cavity and partially extends into the second vent port, and the second valve plate integrally formed with the second guide member. 
     The second valve plate is located in the second check valve cavity, and during the first mode of operation, the second valve plate is exposed to vacuum pressure in the reservoir cavity, which places the second valve plate in contact with the second valve seat, preventing purge vapor from entering the second check valve cavity from the reservoir cavity. During the second mode of operation, the second valve plate is exposed to vacuum pressure from the venturi valve assembly, which moves the second valve plate toward and in contact with the second inner wall, placing the second check valve in the open position, allowing purge vapor to flow from the reservoir cavity through the second check valve aperture, through the second check valve cavity, and through the second plurality of vents and out of the second vent port. 
     In one embodiment, the turbo purge valve assembly of the present invention is used with an air flow system for a vehicle. The air flow system includes a turbocharger unit for generating the pressurized air such that a portion of the pressurized air flows into the first check valve of the turbo purge valve assembly during the second mode of operation. The air flow system also includes a canister containing purge vapor, which is in fluid communication with the turbo purge valve assembly. A pressure sensor is used for detecting a change in pressure in the canister. The turbo purge valve assembly is part of the air flow system, and performs an on-board diagnostic test for detecting a malfunction in the air flow system. During the on-board diagnostic test, the air flow system is in the second mode of operation, and the turbocharger unit is generating pressurized air, the solenoid assembly is placed in the closed position. If the system is functioning properly, there is no change in pressure in the canister when the solenoid assembly is changed to the closed position because the canister and the turbo purge valve assembly are sealed components. If the pressure sensor detects change in pressure in the canister, this is an indication of a malfunction, such as a leak, in the canister, the turbo purge valve assembly, or some other component, when a change of pressure occurs. 
     In one embodiment, the turbo purge valve assembly also includes a canister vacuum relief function, where the solenoid assembly is pulsated after the vehicle is shut off. The pulsation of the solenoid assembly generates an air pulsation in the reservoir cavity, opening one of the first check valve or the second check valve, allowing air to pass from either of the first vent port or the second vent port into the reservoir cavity, through the solenoid assembly, through the overmold assembly cavity, and into the canister to relieve vacuum pressure in the canister. 
     The turbo purge valve assembly also includes the features having the ability to reduce or eliminate turbo lag which occurs during the initial activation of the turbocharger unit. The first check valve is unbiased towards the open position or the closed position, and the second check valve is also unbiased towards the open position or closed position, allowing both the first check valve and the second check valve to transition between open and closed positions from the application of the pressurized air or vacuum pressure, reducing turbo lag as the turbocharger is activated and deactivated. 
     In other embodiments, the turbo purge valve assembly is oriented such that gravity biases the first check valve to the open position, or the turbo purge valve assembly is oriented such that gravity biases the first check valve to the closed position. In yet other alternate embodiments, the turbo purge valve assembly is oriented such that gravity biases the second check valve to the open position, or the turbo purge valve assembly is oriented such that gravity biases the second check valve to the closed position. 
     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 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a diagram of an air flow system having a turbo purge valve assembly, according to embodiments of the present invention; 
         FIG. 2  is a perspective view of a turbo purge valve assembly, according to embodiments of the present invention; 
         FIG. 3  is a sectional side view of a turbo purge valve assembly, according to embodiments of the present invention; and 
         FIG. 4  is an exploded view of a turbo purge valve assembly, according to embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     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. 
     A diagram of an airflow system of a vehicle having a turbo purge valve assembly according to the present invention is shown generally in  FIG. 1  at  10 . The system  10  includes an air box  12  which intakes air from the atmosphere. Located downstream of and in fluid communication with the air box  12  is a turbocharger unit  14 , and located downstream of and in fluid communication with the turbocharger unit  14  is a throttle assembly  16 . The throttle assembly  16  controls the amount of air flow into an intake manifold  18 , which is part of an engine. 
     A plurality of conduits also provides fluid communication between the various components. Air flows through the conduits between the various components, and the direction of airflow through the conduits varies, depending on the mode of operation of each component. More specifically, there is a first conduit  20   a  providing fluid communication between the air box  12  and the turbocharger  14 , a second conduit  20   b  providing fluid communication between the turbocharger  14  and the throttle assembly  16 , and there is also a third conduit  20   c  providing fluid communication between the throttle assembly  16  and the intake manifold  18 . 
     A fourth conduit  20   d  is in fluid communication with the third conduit  20   c  and a turbo purge valve assembly  22 , and a fifth conduit  20   e  places the turbo purge valve assembly  22  in fluid communication with a venturi valve assembly  24 . The turbo purge valve assembly  22  includes a first check valve  60  in fluid communication with the fourth conduit  20   d , and a second check valve  62  in fluid communication with the fifth conduit  20   e . There is also a carbon canister  30  in fluid communication with the turbo purge valve assembly  22  through the use of a sixth conduit  20   f.    
     A seventh conduit  20   g  provides fluid communication between the venturi valve assembly  24  and the second conduit  20   b , such that pressurized air is able to flow from the second conduit  20   b , through the seventh conduit  20   g  and to the venturi valve assembly  24 . An eighth conduit  20   h  provides fluid communication between the venturi valve assembly  24  and the air box  12 . 
     Referring to  FIGS. 2-4 , the turbo purge valve assembly  22  includes an overmold assembly  36 , and disposed within the overmold assembly  36  is a solenoid assembly, shown generally at  68 , and the solenoid assembly  68  is disposed within a cavity, shown generally at  70 , formed as part of the overmold assembly  36 , and the cavity includes an inner wall portion  72 , and also forming part of the cavity  70  is an outer wall portion  74  of the overmold assembly  36 . 
     The solenoid assembly  68  includes a stator insert  38  which surrounds a support  78  formed as part of the overmold assembly  36 . A first washer  40  is disposed between an upper wall  80  of the overmold assembly  36  and a bobbin  42 . The bobbin  42  is surrounded by a coil  48 , and two straps  44  surround the coil  48 . There is a sleeve  46  which is surrounded by the bobbin  42 , and the sleeve  46  partially surrounds a moveable armature  54 . The armature  54  includes a cavity, shown generally at  82 , and located in the cavity  82  is a spring  52 , which is in contact with an inner surface  84  of the cavity  82 . The spring  52  is also mounted on a narrow diameter portion  86  of the support  78 . Disposed between part of the armature  54  and the bobbin  42  is a second washer  50 . Connected to the overmold assembly  36  is a cap  56 , and formed as part of the cap  56  is a valve seat  88  and a cap aperture  90 , where purge vapor is able to flow from an overmold assembly cavity, shown generally at  92 , formed as part of the overmold assembly  36  and through the cap aperture  90 . 
     The armature  54  includes a stopper portion  54   a  which is made of a rubber or other flexible material. The stopper portion  54   a  includes a contact surface  96  which contacts the valve seat  88  when the armature  54  is in the closed position. The stopper portion  54   a  includes a plurality of post members  98  are of the same durometer, but are of different sizes, and therefore have different levels of stiffness. The largest post members  98  are in contact with the bottom surface of the washer  50  when the armature  54  is in the closed position, as shown in  FIG. 3 . The smaller post members  98  contact the bottom surface of the washer  50  when the armature  54  moves to the open position. The more the coil  48  is energized, the further the armature  54  moves away from the valve seat  88 , and the greater number of post members  98  contact the bottom surface of the washer  50 . The movement of the armature  54  to open and close the solenoid assembly  68  controls the amount of purge vapor allows to pass through the turbo purge valve assembly  22 , and into the intake manifold  18 . 
     Because the post members  98  are made of rubber, the post members  98  are able to deform as the armature  54  is moved further away from the valve seat  88 . The largest post members  98  in contact with the bottom surface of the washer  50  deform first when the armature  54  moves away from the valve seat  88 . As the armature  54  moves further away from the valve seat  88 , more of the post members  98  contact the bottom surface of the washer  50 , and then begin to deform as the armature  54  moves even further away from the valve seat  88 . The deformation of the post members  98  (when the armature  54  is moved to the open position away from the valve seat  88 ) functions to dampen the movement of the armature  54 , eliminating noise, and preventing metal-to-metal contact between the armature  54  and the stator insert  38 . 
     Disposed between the bottom surface of the washer  50  and an inside surface  100  of the cap  56  is a filter  102 . The filter  102  is made of several blades of plastic which are adjacent one another. The filter  102  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  54  and the stator insert  38  is about 1.0 millimeters, and is the maximum allowable distance between the contact surface  96  of the stopper portion  54   a  and the valve seat  88 . The filter  102  ensures that no particles may pass through the filter  102  that are too large to affect the functionality of the solenoid assembly  68  (the particles being too large to fit between the valve seat  88  and the stopper portion  54   a ) when the armature  54  is in the open position. 
     The aperture  90  is also in fluid communication with a reservoir cavity, shown generally at  94 , formed as part of a reservoir  58 . The cavity  94  is also in fluid communication with a first check valve  60  and a second check valve  62 . The first check valve  60  includes a first vent port  64 , and the second check valve  62  includes a second vent port  66 . The check valves  60 , 62  and the vent ports  64 , 66  are substantially similar. 
     The first vent port  64  of the first check valve  60  includes a first cap portion  104  which is connected to a first flange portion  106  formed as part of the reservoir  58 . The connection between the cap portion  104  and the flange portion  106  may be any suitable connection, such as snap-fitting, welding, an adhesive, or the like. The connection between the cap portion  104  and the flange portion  106  forms a first check valve cavity, shown generally at  108 , and formed as part of a first side wall  110  of the reservoir  58  is a first check valve aperture  112 , which allows for fluid communication between the cavity  108  and the cavity  94  when the first check valve  60  is in an open position. 
     The first check valve  60  also includes a first valve member  114 , which in this embodiment is a first valve plate  114 , located in the first check valve cavity  108 , and includes a first seal member  116  that selectively contacts a first valve seat  118  and a first inner wall  120  of the cap portion  104 . The valve seat  118  at least partially surrounds the aperture  112 , and no air passes around the valve plate  114  when the seal member  116  is in contact with the valve seat  118 , where the first check valve  60  is in the closed position. The inner wall  120  is part of a first base portion  122 , and formed as part of the base portion  122  is a first plurality of vents  124  which are in fluid communication with the cavity  108 , such that when the seal member  116  is not in contact with the valve seat  118 , purge vapor is able to flow from the cavity  94  through the aperture  112  into the cavity  108 , and through the vents  124  and into the first vent port  64 . 
     Formed with the valve plate  114  is a first guide member  126 , which is cylindrical in shape, and partially extends into an aperture  128  formed as part of the side wall  110 , and also partially extends into another aperture  130  formed as part of the base portion  122 . The first guide member  126  is able to slide freely in the apertures  128 , 130 , and does not bias the valve plate  114  in a particular direction. The guide member  126  is able to slide freely in the apertures  128 , 130  because there is a clearance between the outer diameter of the guide member  126  and the diameter of each of the apertures  128 , 130 , and this clearance allows for some of the purge vapor to pass through the apertures  128 , 130 . However, when the seal member  116  is in contact with the valve seat  118 , purge vapor flowing through the clearance around the guide member  126  in the aperture  128  or through the aperture  112  does not flow around the valve plate  114  or the seal member  116 . 
     The second check valve  62  includes similar components to the first check valve  60 , and functions in a similar manner. The components of the second check valve  62  includes a second cap portion  104   a  connected to the second flange portion  106   a  of the reservoir  58 , and a second check valve cavity, shown generally at  108   a , formed by the connection of the cap portion  104   a  to the second flange portion  106   a . A second side wall  110   a  is also formed as part of the reservoir  58 , and a second check valve aperture  112   a  is formed as part of the second side wall  110   a  to provide fluid communication between the cavity  94  and the second check valve cavity  108   a . The second valve member  114   a  having a second seal member  116   a  is located in the second check valve cavity  108   a  and selectively contacts the valve seat  118   a  formed as part of the side wall  110   a  and the inner wall  120   a  formed as part of the a base portion  122   a . The base portion  122   a  and the second cap portion  104   a  are part of the second vent port  66 . Similarly to the first base portion  122 , there is a second plurality of vents  124   a  formed as part of the second base portion  122   a . A second guide member  126   a  is integrally formed with the valve plate  114   a , and the second guide member extends into the aperture  128   a  formed as part of the second side wall  110   a  and the aperture  130   a  formed as part of the second base portion  122   a.    
     The air flow system  10  has multiple modes of operation. In a first mode of operation, when the turbocharger  14  is not active, air flows through the air box  12 , the turbocharger  14 , the throttle  16 , and into the intake manifold  18 . There is vacuum pressure in the intake manifold  18  created by the engine during the first mode of operation, drawing air into the intake manifold  18 . This vacuum pressure is also in the fourth conduit  20   d , and when the solenoid assembly  68  is in the open position, the vacuum causes the first check valve  60  to open, where during the first mode of operation, the vacuum pressure draws the valve plate  114  away from the valve seat  118  and toward the inner wall  120 , such that the seal member  116  contacts the inner wall  120 , allowing purge vapor to pass from canister  30 , through the sixth conduit  20   f , the cavity  92  of the overmold assembly  36  from an inlet port  132  connected to the sixth conduit  20   f , the aperture  90 , the cavity  94  of the reservoir  58 , through the aperture  112 , the valve cavity  108 , through the vents  124 , the first vent port  64  and into the fourth conduit  20   d . The purge vapor from flows through the fourth conduit  20   d , through the third conduit  20   c  where the purge vapor mixes with air and flows into the intake manifold  18 . This same vacuum pressure also causes the second check valve  62  to close, where the vacuum pressure in the cavity  94  of the reservoir  58  draws the second valve plate  114   a  towards the second valve seat  118   a , such that the second seal member  116   a  contacts the valve seat  118   a , and the purge vapor does not pass through the second check valve  62 . 
     The air flow system also has a second mode of operation, where the turbocharger  14  is activated, and air flowing into the turbocharger  14  from the air box  12  is pressurized, the pressurized air flows through the throttle  16 , and the air then flows into the intake manifold  18 . In this second mode of operation, the manifold  18  is operating under positive pressure. Some of this pressurized air flows into the fourth conduit  20   d , and into the first vent port  64 . During the second mode of operation, the pressurized air then flows through the vents  124  and into the first check valve cavity  108  and applies pressure to the first valve plate  114 , moving the valve plate  114  towards the valve seat  118  such that the seal member  116  contacts the valve seat  118 , placing the first check valve  60  in the closed position. 
     When the turbocharger  14  is activated during the second mode of operation, and pressurized air is passing through the seventh conduit  20   g , the venturi valve assembly  24 , and the eighth conduit  20   h . The pressurized air flowing through the venturi valve assembly  24  also creates vacuum pressure in the fifth conduit  20   e , where air is drawn from the fifth conduit  20   e  into venturi valve assembly  24 , such that the air passes through the eighth conduit  20   h  and into the air box  12 . During the second mode of operation, this vaccum pressure in the fifth conduit  20   e  also draws the second valve plate  114   a  away from the second valve seat  118   a  and towards the inner wall  120   a  of the base portion  122   a , placing the second check valve  62  in an open position. During the second mode of operation, purge vapor from the canister  30  passes through the sixth conduit  20   f , the cavity  92  of the overmold assembly  36  from the inlet port  132  connected to the sixth conduit  20   f , the aperture  90  (when the solenoid assembly  68  is in the open position), the cavity  94  of the reservoir  58 , through the aperture  112   a , the valve cavity  108   a , through the vents  124   a , the second vent port  66  and into the fifth conduit  20   e . The purge vapor flows into the venturi valve assembly and mixes with the pressurized air in the eighth conduit  20   h , and flows into the air box  12 . The purge vapor and air mixture then flows through the turbocharger  14 , the throttle  16 , and into the intake manifold  18 . 
     The orientation of the turbo purge valve assembly  22  also has an effect on the operation of the turbo purge valve assembly  22 , since there are no springs or other biasing members in either of the check valves  60 , 62  to bias either of the check valves  60 , 62  to an open or closed position. In the embodiment shown in  FIG. 1 , gravity biases the valve plate  114  of the first check valve  60  downward (towards the first valve seat  118 ), and therefore towards the closed position. However, it is within the scope of the invention that the turbo purge valve assembly  22  may be oriented such that gravity may bias the first valve plate  114  toward either the first valve seat  118  or the inner wall  120 . It is also within the scope of the invention that the turbo purge valve assembly  22  may be oriented such that gravity may bias the second valve plate  114   a  toward either of the second valve seat  118   a  or the second inner wall  120   a . The turbo purge valve assembly  22  is shown in different orientations in  FIGS. 1-4 , where gravity biases the check valves  60 , 62  to either the open or closed positions, depending on the orientation of the valve assembly  22 . 
     Furthermore, the free movement of each of the valve plates  114 , 114   a  in the respective check valve cavities  108 , 108   a  also provides the advantage of reducing or eliminating turbo lag. Because there is no biasing member which biases either of the valve plates  114 , 114   a  towards an open or closed position, the valve plates  114 , 114   a  change position quickly between the open and closed positions as the manifold  18  changes from operating under vacuum pressure to positive pressure, when the turbocharger  14  is activated. 
     When the turbocharger  14  is generating pressurized air during the second mode of operation, and purge vapor is passing through the purge valve assembly  22 , some level of vaccum is detectable in the canister  30  by a pressure sensor  32 . By placing the solenoid assembly  68  in the closed position, flow through the venturi valve assembly  24  is reduced, exposing the sixth conduit  20   f  and the canister  30  to less vacuum pressure, which is detected by the sensor  32 . If there is a pressure change detected by the sensor  32  in the canister  30  when the solenoid assembly  68  is changed between the open and closed positions, a malfunction has occurred, such as the sixth conduit  20   f  becoming disconnected from either the canister  30  or the inlet port  132 , and a malfunction light may be used to alert the vehicle driver the malfunction has occurred. 
     Another function of the turbo purge valve assembly  22  is the relief of vacuum pressure in the canister  30  and the fuel tank 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 and the canister. The turbo purge valve assembly  22  is capable of relieving this vacuum pressure. To relieve the vacuum pressure, the solenoid assembly  68  is pulsated after the vehicle is shut off. In one embodiment, the solenoid assembly  68  is pulsated at 10 Hz, but it is within the scope of the invention that the solenoid assembly  68  may be pulsated at other frequencies. This pulsation opens one of the check valves  60 , 62  to allow air to flow from one of the ports  64 , 66  into the cavity  94 , and then through the aperture  90  and into the cavity  92 . The air flows back into the cavity  92 , through the sixth conduit  20   f , the canister  30 , and into the fuel tank, relieving the vacuum pressure. 
     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.