Abstract:
A system which includes a turbo bypass switching valve (BSV) positioned at a beneficial location as a direct mount on an air box to achieve compliance to OBD hose-off requirement via electronic actuation of the BSV and monitoring of the fuel tank pressure sensor for pressure change. When the turbocharger unit is generating pressurized air, the turbo BSV is open, and vapor is passing through the purge valve, some level of vacuum in the fuel tank is sensed. By closing the BSV, flow through the venturi is reduced, producing both less vacuum and a change in fuel tank pressure. The pressure change does not occur if any of the hoses become disconnected. This results in a simple OBD “venture hose off” check without additional components.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/825,649 filed May 21, 2013, U.S. Provisional Application No. 61/825,681 filed May 21, 2013, and U.S. Provisional Application No. 61/825,616 filed May 21, 2013. The disclosures of the above applications are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates generally to a valve assembly which is mounted on an air box and capable of providing venting from a carbon canister, as well as providing venting from the fuel EVAP system during OBD testing. 
       BACKGROUND OF THE INVENTION 
       [0003]    Current turbo purge systems use a venturi vacuum generator (such as a vacuum pump) to allow purge of the evaporative system while the turbocharger unit is activated (i.e., the intake manifold is under positive pressure). This vacuum pump often uses significant amounts of the pressurized air created by the turbocharger unit, thereby reducing the power increase created by the turbocharger unit. In order to limit the amount of turbo air running through the pump, and temporarily maximize engine power, a turbo bypass switching valve (BSV) has been used to alter the amount of flow going to the vacuum pump (venturi nozzle). 
         [0004]    Recent changes in the legislation of evaporative emissions management systems have required that the On-Board Diagnostic (OBD) system have the capacity to determine if the outlet flow of the venturi (which contains hydrocarbons) is connected to the vehicle inlet system, or if it has become disconnected or broken. 
         [0005]    To provide compliance with these regulations, various systems typically require a separate (OBD) relief valve to conduct the OBD test, and detect if there is a leak, or if one or more of the hoses has become disconnected. The valve is necessary to conduct the OBD test. However, the inclusion of this valve adds complexity and cost to the system. 
         [0006]    Other attempts to comply with the regulations include systems with the turbo BSV mounted in-line and upstream of the vacuum pump. The drawback to this approach is that this results in an increase in the temperature and pressure requirements for the turbo BSV. Also, the OBD check for every hose connection is more complex and may require additional components. 
         [0007]    Accordingly, there exists a need for a valve assembly which is incorporated into the airflow system which is capable of performing the OBD test for failure, as well as having the capability to perform purge system function. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention provides a system which includes a turbo bypass switching valve (BSV) positioned at a beneficial location as a direct mount on the air box. In this configuration, the system achieves compliance to OBD hose-off requirement via electronic actuation of the BSV and monitoring of the carbon canister pressure sensor for reaction, such as pressure change. This configuration has cost and efficiency benefit over other systems. 
         [0009]    In one embodiment, the turbo BSV is mounted on or within the air box and secured with a fastener, such as a bolt. The venturi vacuum generator (vacuum pump) is installed in-line between the turbocharger unit and turbo BSV. 
         [0010]    Having the BSV mounted on the air box reduces the number of connections, and the temperature and pressure requirements for the BSV are significantly reduced, resulting in cost benefits. 
         [0011]    A secure connection using a bolt between turbo BSV and air box allows the OBD system to detect any hose disconnection between any one of the outlet of the turbocharger unit, the venturi vacuum generator, and the turbocharger unit. At a steady state, when the turbocharger unit is generating pressurized air, the turbo BSV is open, and vapor is passing through the purge valve, some level of vacuum in the carbon canister is sensed. By closing the BSV, flow through the venturi is reduced, producing both less vacuum and a change in canister pressure. This pressure change is detected by a pressure sensor, and any change in the state of operation of the BSV results in a change in the state of the pressure sensor. The pressure change does not occur if any of the hoses mentioned above is disconnected, of there is a leak. This results in a simple OBD “venturi hose off” check without additional components. 
         [0012]    One of the advantages of the configuration of the present invention is the reduced temperature and pressure requirements for the turbo BSV because of the mounting of the BSV on the air box, and simplified OBD check for every hose connection by securing the turbo BSV on the air box. 
         [0013]    In one embodiment, the present invention is a bypass switching valve assembly mounted on an air box, where the valve assembly includes an overmold assembly having an inlet port, a bypass switching valve, and an overmold assembly cavity formed as part of the overmold assembly, where the bypass switching valve located in the overmold assembly near the overmold assembly cavity. A cap is connected to the overmold assembly, a reservoir is connected to the cap, and a reservoir cavity is 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 bypass switching valve is in an open position. 
         [0014]    A bleed aperture is formed as part of the cap, and the bleed aperture provides fluid communication between the overmold assembly cavity and the reservoir cavity when the bypass switching valve is in the open position or in a closed position such that pressurized air and purge vapor are able to pass from the overmold assembly cavity to the reservoir cavity under low-pressure conditions. 
         [0015]    At least one port is connected to the reservoir and is in fluid communication with the reservoir cavity. The port extends into an aperture formed as part of an air box. A check valve is connected to the reservoir, the check valve is biased towards a closed position such that when pressurized air and purge vapor flow into the inlet port and the overmold assembly cavity, and the bypass switching valve is in the open position, the pressurized air and purge vapor flow through the cap aperture, through the reservoir cavity, and force the check valve into an open position, such that the pressurized air and purge vapor flow through the port and into the air box. 
         [0016]    The valve assembly and the air box are part of an air flow system which includes a carbon canister containing the purge vapor, where the carbon canister is in fluid communication with the valve assembly, and a pressure sensor is connected to the carbon canister. The pressure sensor detects changes in pressure in the carbon canister, such that a diagnostic check is performed when the bypass switching valve is switched between an open position and a closed position. During normal operation when the air flow system is functioning properly, the pressure in the canister changes when the bypass switching valve changes between an open position and a closed position. When a change in pressure in the canister is not detected by the pressure sensor as the bypass switching valve changes between an open position and a closed position, an indication is provided that the air flow system is functioning improperly. 
         [0017]    In alternate embodiments, various turbo BSV and various venturi vacuum generators (vacuum pumps) are used in the same configuration and all are suitable with the same effect. 
         [0018]    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 
         [0019]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0020]      FIG. 1  is a diagram of an airflow system for a vehicle having a turbo bypass switching valve assembly mounted on an air box, according to embodiments of the present invention; 
           [0021]      FIG. 2  is a perspective view of a turbo bypass switching valve assembly, according to embodiments of the present invention; 
           [0022]      FIG. 3  is a top view of a turbo bypass switching valve assembly, according to embodiments of the present invention; 
           [0023]      FIG. 4  is a sectional side view taken along lines  4 - 4  of  FIG. 3 , according to embodiments of the present invention; and 
           [0024]      FIG. 5  is a sectional top view taken along lines  5 - 5  of  FIG. 2 , with the turbo bypass switching valve assembly mounted to an air box, according to embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    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. 
         [0026]    A diagram of an air flow system having a bypass switching valve (BSV) mounted to an air box according to the present invention is shown in the  FIG. 1  generally at  10 . The system  10  includes an air box  12  which intakes air from the atmosphere, and the air box  12  is connected to a first conduit  20   a . There are several conduits which provide fluid communication between the various components. Located downstream of and in fluid communication with the first conduit  20   a  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. Air flows from the throttle assembly  18  into the intake manifold  20 . 
         [0027]    As mentioned above, 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, in addition to the first conduit  20   a  providing fluid communication between the air box  12  and the turbocharger unit  14 , there is a second conduit  20   b  providing fluid communication between the turbocharger unit  14  and the throttle assembly  16 . There is also a third conduit  20   c  providing fluid communication between the throttle assembly  16  and the intake manifold  18 . 
         [0028]    A fourth conduit  20   d  is in fluid communication with the third conduit  20   c  and a fifth conduit  20   e.  The fifth conduit  20   e  also places a turbo purge valve assembly, shown generally at  22 , in fluid communication with a venturi valve assembly  28 . A first check valve  24  is located in the fourth conduit  20   d,  and a second check valve  26  is located in 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,  and a pressure sensor  32  connected to the carbon canister  30  to detect the pressure in the carbon canister  30 . 
         [0029]    A seventh conduit  20   g  provides fluid communication between the venturi valve assembly  28  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  28 . An eighth conduit  20   h  provides fluid communication between the venturi valve assembly  28  and a bypass switching valve assembly, shown generally at  34 . 
         [0030]    With reference to  FIGS. 2-5 , connected to the air box  12  and the eighth conduit  20   h  is the bypass switching valve assembly  34 . The bypass switching valve assembly  34  includes a third check valve, or bypass check valve, shown generally at  36 , and a bypass switching valve, shown generally at  38 . 
         [0031]    The bypass switching valve assembly  34  also includes an overmold assembly  40 , and disposed within the overmold assembly  40  is a solenoid assembly, shown generally at  42 , which is part of the bypass switching valve  38 . The solenoid assembly  42  is disposed within a cavity, shown generally at  44 , formed as part of the overmold assembly  40 , and the cavity  44  includes an inner wall portion  46 . Also forming part of the cavity  44  is an outer wall portion  48  of the overmold assembly  40 . 
         [0032]    The solenoid assembly  42  includes a stator insert  50  which surrounds a support  52  formed as part of the overmold assembly  40 . A first washer  54  is disposed between an upper wall  56  of the overmold assembly  40  and a bobbin  58 . The bobbin  58  is surrounded by a coil  60 , and two straps (not shown) surround the coil  60 . There is a sleeve  62  which is surrounded by the bobbin  58 , and the sleeve  62  partially surrounds a moveable armature  64 . The armature  64  includes a cavity, shown generally at  68 , and located in the cavity  68  is a spring  70 , which is in contact with an inner surface  72  of the cavity  68 . The spring  70  is also mounted on a narrow diameter portion  74  of the support  52 . Disposed between part of the armature  64  and the bobbin  58  is a second washer  76 . Connected to the overmold assembly  40  is a cap  78 , and formed as part of the cap  78  is a valve seat  80  and a cap aperture  82 , where purge vapor is able to flow from an overmold assembly cavity, shown generally at  108 , formed as part of the overmold assembly  40  and through the cap aperture  82 . 
         [0033]    The armature  64  includes a stopper portion  64   a  which is made of a rubber or other flexible material. The stopper portion  64   a  includes a contact surface  84  which contacts the valve seat  80  when the armature  64  is in the closed position. The stopper portion  64   a  includes a plurality of post members  86  which are of the same durometer, but are of different sizes, and therefore have different levels of stiffness. The largest post members  86  are in contact with the bottom surface of the washer  76  when the armature  64  is in the closed position, as shown in  FIG. 3 . The smaller post members  86  contact the bottom surface of the washer  76  when the armature  64  moves to the open position. The more the coil  60  is energized, the further the armature  64  moves away from the valve seat  80 , and the greater number of post members  86  contact the bottom surface of the washer  76 . Because the post members  86  are made of rubber, the post members  86  are able to deform as the armature  64  is moved further away from the valve seat  80 . The largest post members  86  in contact with the bottom surface of the washer  76  deform first when the armature  64  moves away from the valve seat  80 . As the armature  64  moves further away from the valve seat  80 , more of the post members  86  contact the bottom surface of the washer  76 , and then begin to deform as the armature  64  moves even further away from the valve seat  80 . The deformation of the post members  86  (when the armature  64  is moved to the open position away from the valve seat  80 ) functions to dampen the movement of the armature  64 , eliminating noise, and preventing metal-to-metal contact between the armature  64  and the stator insert  50 . 
         [0034]    Disposed between the bottom surface of the washer  76  and an inside surface  88  of the cap  78  is a filter  90 . The filter  90  is made of several blades of plastic which are adjacent one another. The filter  90  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  64  and the stator insert  50  is about 1.0 millimeters, and is the maximum allowable distance between the contact surface  84  of the stopper portion  64   a  and the valve seat  80 , when the armature  64  is moved to the fully open position. The filter  90  ensures that no particles may pass through the filter  90  that are too large to affect the functionality of the solenoid assembly  42  (the particles being too large to fit between the valve seat  80  and the stopper portion  64   a ) when the armature  64  is in the open position. 
         [0035]    The aperture  82  is also in fluid communication with a reservoir cavity, shown generally at  92 , formed as part of a reservoir  94 . The cavity  92  is also in fluid communication with the check valve  36 . The check valve  36  includes a vent port  96 , and the vent port  96  includes a cap portion  98  which is connected to a flange portion  100  formed as part of the reservoir  94 . The connection between the cap portion  98  and the flange portion  100  may be any suitable connection, such as snap-fitting, welding, an adhesive, or the like. The connection between the cap portion  98  and the flange portion  100  forms a first check valve cavity, shown generally at  102 , and formed as part of a lower wall  104  of the reservoir  94  is a plurality of check valve apertures  106 , which allow for fluid communication between the cavity  102  and the cavity  92  when the check valve  36  is in an open position. 
         [0036]    The check valve  36  also includes a valve member  110 , which in this embodiment is an umbrella valve member  110 , located in the check valve cavity  102 , and includes a flexible flange portion  118  that selectively contacts the lower wall  104 . The valve member  110  also includes an inside surface  110   a  which is part of the flange portion  118 , and a base member  110   b  which is at least partially disposed in a central aperture  104   a  which is formed as part of the lower wall  104 . Formed as part of the base member  110   b  is a retention feature  110   c,  which has a larger diameter than the central aperture  104   a.  The valve member  110  is made of a flexible material, such as rubber, and during assembly, the base member  110   b  is pressed through the central aperture  104   a  such that the retention feature  110   c  is moved into the reservoir cavity  92 , as shown in  FIG. 3 . Because the diameter of the retention feature  110   c  is larger than the diameter of the central aperture  104   a,  the base member  110   b  is prevented from being removed from the central aperture  104   a.  The central aperture  104   a  surrounds part of the base member  110   b,  and part of the lower wall  104  is disposed between the retention feature  110   c  and a support member  110   d,  which is also formed as part of the base member  110   b,  securing the valve member  110  in place relative to the lower wall  104 . As mentioned above, the valve member  110  is made of a flexible material, and the flange portion  118  deflects when exposed to air flow in different directions. 
         [0037]    An inner wall  112  is part of a base portion  114 , and also formed as part of the base portion  114  is a plurality of vents  116  which are in fluid communication with the cavity  102 , such that when the flange portion  118  is not in contact with the side wall  104 , purge vapor is able to flow from the cavity  92  through the apertures  106  into the cavity  102 , and through the vents  116  and into the first vent port  96 . 
         [0038]    A bleed aperture  122  is formed as part of the cap  78 , and is substantially parallel to the cap aperture  82 , and places the overmold assembly cavity  108  in continuous fluid communication with the reservoir cavity  92 . The bleed aperture  122  is also located in proximity to the cap aperture  82  such that any air or purge vapor passing through the aperture  122  must also pass through the filter  90  before passing through the bleed aperture  122  and into the reservoir cavity  92 . The bleed aperture  122  is substantially smaller in diameter in comparison to the cap aperture  82 , and only allows for a small amount of air and purge vapor to pass through. 
         [0039]    As mentioned above, the BSV assembly  34  is mounted on the air box  12 . In this embodiment, the BSV assembly  34  is mounted to the air box  12  using a mounting assembly having a plurality of brackets. Formed as part of the overmold assembly  40  is a first bracket  124  which is part of the mounting assembly. Mounted to the first bracket  124  is a first isolator  126  having a slot  128 , and located in the slot  128  is a flange  130 , which is formed as part of the air box  12 . The slot  128  is substantially rectangular shaped, and the flange  130  is shaped to correspond to the shape of the slot  128 , such that the flange  130  fits within the slot  128 . 
         [0040]    The flange  130  protrudes away from a base portion  132  formed as part of the air box  12 . Part of the first isolator  126  contacts the base portion  132  when the flange  130  is located in the slot  128 . 
         [0041]    Also part of the mounting assembly is a second bracket  134  which is connected to the reservoir  94 . The second bracket  134  includes an aperture  136 , and disposed in the aperture  136  is a second isolator  138  and a washer  140 . The washer  140  includes an aperture  142 , and selectively disposed within the aperture  142  is a fastener, which in this embodiment is a bolt  144 . When assembled, the bolt  144  at least partially extends into an aperture  146  formed as part of the air box  12 . 
         [0042]    The second bracket  134  is formed as part of the cap portion  98  of the vent port  96 , and the vent port  96  is surrounded by a sealing device. In this embodiment, the sealing device is a first O-ring  148  disposed in a first groove  150 , and a second O-ring  152  disposed in a second groove  154 . The vent port  96  extends into a flow aperture  156  formed as part of the air box  12 , and a seal between the vent port  96  and the flow aperture  156  is provided by the O-rings  148 , 152 . More specifically, the first O-ring  148  is disposed in the first groove  150  and is in contact with the inner surface of the aperture  156 , and the second O-ring  152  is disposed in the second groove  154  and is also in contact with the inner surface of the aperture  156 . However, it is within the scope of the invention that other types of seals may be used, other than the O-rings  148 , 152 . 
         [0043]    During the assembly of the CPV  10  to the air box  12 , the flange  130  is inserted into the slot  128 . The placement of the flange  130  into the slot  128  ensures that the aperture  142  of the washer  140  is properly aligned with the aperture  146  of the air box  12 , and provides alignment between the vent port  96  and the flow aperture  156 . After the flange  130  is inserted into the slot  128  and the vent port  96  is positioned in the flow aperture  156 , the bolt  144  is inserted through the aperture  142  of the washer  140  and into the aperture  146 . The aperture  146  and the bolt  144  are threaded such that the bolt  144  may be tightened. This provides a rigid connection between the bypass switching valve assembly  34  and the air box  12 . 
         [0044]    The first bracket  124  does not contact the air box  12  because of the first isolator  126 , the second bracket  134  does not contact the air box  12  because of the second isolator  138  and the washer  140 , and the vent port  96  does not contact the air box  12  because of the O-rings  148 , 152 . Therefore, the bypass switching valve assembly  34  is not in contact with the air box  12 , but is still rigidly connected to the air box  12  because of the bolt  144  and the washer  140 . This prevents the bypass switching valve assembly  34  from contacting the air box  12 , and therefore prevents any noise generation resulting from vibration in the air box  12 , and also provides noise isolation to the air box  12 . 
         [0045]    Referring again to the Figures generally, the air flow system  10  has multiple modes of operation. In a first mode of operation, when the turbocharger unit  14  is not active, there is vacuum pressure in the intake manifold  18  created by the engine during the first mode of operation, wherein air flows from the air box  12  through the first conduit  20   a,  the turbocharger unit  14 , the throttle  16 , and into the intake manifold  18 . This vacuum pressure is also in the fourth conduit  20   d,  and when the turbo purge valve assembly  22  is in an open position, the vacuum pressure causes the first check valve  24  to open, where during the first mode of operation, the vacuum pressure draws the purge vapor from canister  30 , through the sixth conduit  20   f,  the turbo purge valve assembly  22 , and into part of the fifth conduit  20   e  prior to entering into the fourth conduit  20   d.  The purge vapor then 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 . During the first mode of operation, the bypass switching valve assembly  34  is not exposed to the vacuum pressure from the intake manifold  18 , but rather is exposed to atmospheric pressure in the air box  12 . Since the check valve  36  is biased towards a closed position, the check valve  36  remains closed during the first mode of operation. 
         [0046]    The air flow system  10  also has a second mode of operation, where the turbocharger unit  14  is activated, and air flowing into the turbocharger unit  14  from the first conduit  20   a  becomes pressurized, the pressurized air then flows through the second conduit  20   b  and into the throttle  16 , and the air then flows through the third conduit  20   c  and 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 places the first check valve  24  in a closed position. 
         [0047]    The pressurized air passing through the seventh conduit  20   g  also passes through the venturi valve assembly  28 , and into the eighth conduit  20   h.  The pressurized air flowing through the venturi valve assembly  28  also creates vacuum pressure in the fifth conduit  20   e,  where air is drawn from the fifth conduit  20   e  into venturi valve assembly  28 , such that the air passes through the eighth conduit  20   h  and into the BSV assembly  34 . During the second mode of operation, this vacuum pressure in the fifth conduit  20   e  also places the second check valve  26  in an open position. During the second mode of operation, purge vapor from the canister  30  passes through the sixth conduit  20   f,  the turbo purge valve assembly  22  (when the turbo purge valve assembly  22  is in the open position), and into the fifth conduit  20   e.  The purge vapor flows into the venturi valve assembly  28  and mixes with the pressurized air in the eighth conduit  20   h , and flows into bypass switching valve assembly  34 . 
         [0048]    When the pressurized air flows into the bypass switching valve assembly  34 , the pressurized air also flows into the cavity  108  of the overmold assembly  40  from an inlet port  120  connected to the eighth conduit  20   h.  When the solenoid assembly  42  moves the armature  64  away from the valve seat  80 , placing the bypass switching valve  38  in an open position, the pressurized air then flows through the aperture  82 , the cavity  92  of the reservoir  94 , through the apertures  106 , and into the valve cavity  102 . When the third check valve  36  is in the closed position, there is an enclosed area, shown generally at  102   a,  formed by the shape of the flange portion  118  being in contact with the bottom surface of the lower wall  104 . More specifically, an outer edge  118   a  of the flange portion  118  contacts the bottom surface of the lower wall  104 , and the area between the flange portion  118  and the bottom surface of the lower wall  104  forms the enclosed area  102   a.  Once the air flows through the apertures  106 , the pressurized air then applies pressure to the inside surface  110   a  of the valve member  110  in the enclosed area  102   a,  causing the flange portion  118  to deflect. The outer edge  118   a  of the flange portion  118  moves away from the lower wall  104 , and the check valve  36 , and more particularly the valve member  100 , is in the open position. Once the air has passed into the valve cavity  102  when the valve member  100  is in the open position, the pressurized air then flows through the vents  116 , the vent port  96 , and into the air box  12 . 
         [0049]    One the air and purge vapor mixture has passed through the bypass switching valve assembly  34 , the air and purge vapor mixture then flows into the air box  12 . The purge vapor and air mixture then flows through the turbocharger unit  14 , the throttle  16 , and into the intake manifold  18 . 
         [0050]    As mentioned above, the bleed aperture  122  functions to provide continuous fluid communication between the overmold assembly cavity  108  and the reservoir cavity  92 , even when the bypass switching valve  38  is in the closed position, to ensure that when the turbocharger unit  14  is generating pressurized air, and that there is still flow through the bypass switching valve assembly  34  at levels of low air flow. The turbocharger unit  14  is able to generate different levels of pressurized air, and therefore to ensure that there is vacuum pressure in the fifth conduit  20   e,  the pressurized air passes through the venturi valve assembly  28 , and if there is no flow allowed through the bypass switching valve assembly  34 , there is no flow in the eighth conduit  20   h.  The flow through the venturi valve assembly  28  may therefore be limited, reducing the amount of vacuum pressure generated by the venturi valve assembly  28  in the fifth conduit  20   e.    
         [0051]    In the embodiments described above, the third check valve  36  is an umbrella valve. However, it is within the scope of the invention that the third check valve  36  may be other types of valves, such as a ball valve, a flap, a duckbill, or the like, and all would be suitable. 
         [0052]    The bypass switching valve assembly  34  may also be used to run a diagnostic check on the system  10  using the pressure sensor  32 . For example, when the system  10  is operating in the second mode of operation, and the turbocharger unit  14  is generating pressurized air, there is vacuum pressure in fifth conduit  20   e  as mentioned above, and therefore in order to draw the purge vapor from the canister  30  to the BSV assembly  34 , the vacuum pressure is also in the sixth conduit  20   f  when the turbo purge valve assembly  22  is in the open position, and the carbon canister  30 . This vacuum pressure is detectable by the pressure sensor  32 . If the bypass switching valve  38  of the BSV assembly  34  is changed between open and closed positions during the second mode of operation, there should be a change in vacuum pressure which is detectable by the pressure sensor  32 . If there is no change in pressure as detected by the pressure sensor  32 , then there is a leak somewhere in the system, such as a leak or a disconnection of one of the conduits  20   e,    20   f,  or  20   h.  One of the advantages of the present invention is that since the BSV assembly  34  is mounted directly on the air box  12 , a conduit or hose is eliminated, and therefore not needed to provide a connection and fluid communication between the BSV assembly  34  and the air box  12 . Air and purge vapor in the BSV assembly  34  flows directly from the vent port  96 , into the flow aperture  156 , and into the air box  12 . Therefore, if there is a leak, or a “hose off” condition, where one of the conduits becomes disconnected, any concern of a leak between the BSV assembly  34  and the air box  12  is reduced or eliminated. 
         [0053]    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.