Abstract:
A valve assembly used as part of a vapor purge system, which uses a vacuum created by a venturi nozzle to direct purge vapor from a canister through the purge system, and into an intake manifold. The valve assembly includes a check valve which closes the flow path to prevent the uncontrolled venting of hydrocarbon rich purge vapor directly to the atmosphere, and provides an on-board diagnostic (OBD) check to make sure the system is functioning properly. The check valve is typically open because of a pressure balance around the check valve, allowing the turbo bleed flow, as well as the purge vapor, to pass through the check valve and into an air box. If the hose is disconnected, there is a pressure drop across the valve, which causes the check valve to close, preventing the release of hydrocarbons in the purge vapor to the atmosphere.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates generally to an on-board diagnostic feature in an air flow system of a vehicle which also prevents the undesired release of fuel vapors into the atmosphere. 
       BACKGROUND OF THE INVENTION 
       [0002]    Turbochargers are commonly used to increase the power of a vehicle engine. Turbochargers include a turbine which generates pressurized air, and the air is forced into the engine to increase combustion pressure, and therefore increase the power generated by the engine. 
         [0003]    With some tubocharging systems, a portion of the pressurized air is bled off to create a vacuum and induce the 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. 
         [0004]    Some turbo purge systems use a venturi vacuum generator (such as a vacuum pump) to allow purge of the evaporative system while the turbocharger is activated (i.e., the intake manifold is under positive pressure). In typical systems, some of the pressure created by the turbo is bled off, through a venturi, which creates the vacuum needed in the venturi to induce purge vapor flow. These venturi nozzles typically are connected to the air intake box through the use of a hose, through which flows the turbo bleed flow, and the hydrocarbon rich, purge vapor. If this hose becomes detached from the air intake box, this could result in blowing hydrocarbons into the atmosphere under the hood of the car. 
         [0005]    There are a number of systems currently in production that are potentially non-compliance in terms of having the ability to be able to detect a hose-off condition. Attempts have been made to address this issue by putting the entire vacuum generating venturi into the air box. Other solutions have included adding pressure transducers to the line. Both of these approaches involve additional cost, and may not completely solve the problem. 
         [0006]    Accordingly, there exists a need for the prevention of the release of hydrocarbon rich purge vapor in an air flow system when one of the hoses becomes disconnected. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention is a valve assembly used as part of a vapor purge system, which uses a vacuum created by a venturi nozzle to direct purge vapor from a canister through the purge system, and into an intake manifold. The valve assembly includes a check valve which closes the flow path to prevent the uncontrolled venting of hydrocarbon rich purge vapor directly to the atmosphere, and provides an on-board diagnostic (OBD) check to make sure the system is functioning properly. 
         [0008]    During typical operation, the check valve is normally open because of a pressure balance around the check valve, allowing the turbo bleed flow, as well as the purge vapor, to pass through the check valve and into the air box. If the hose is not connected, there is a pressure drop across the valve, and the drop in pressure causes the check valve to close, preventing the venting of hydrocarbons in the purge vapor to the atmosphere. The restricted turbo bleed flow no longer creates a vacuum, and when a purge cycle is commanded, the pressure transducer on the tank then detects that no purge is occurring, indicating a malfunction. This is used to set a malfunctioning light, to indicate that there is a problem. 
         [0009]    The valve assembly of the present invention allows the purge valve and vacuum venturi to be modularized. This eliminates hoses, improves packaging, and reduces system costs. 
         [0010]    Under normal operation, the check valve has a default position, which is an open position, allowing the turbo bleed flow and the purge flow to flow through the check valve and into the hose connecting the check valve to the air box of an engine. There is an orifice, or flow restricting nozzle added to the air box inlet. If the hose connecting the check valve to the air box is disconnected, the change in the pressure drop causes the check valve to close. This stops the turbo bleed flow, and the venturi nozzle no longer provides a vacuum differential to induce purge flow. If the purge valve opens, and a purge is expected, the pressure transducer on the purge line does not detect a drop in pressure, indicating that there is an issue, and a malfunction light may be activated to alert the driver of the vehicle that something is malfunctioning. The check valve therefore prevents an uncontrolled release of hydrocarbon rich air to the atmosphere, and provides an OBD diagnostic test to allow for a validation of the functionality of the system. 
         [0011]    In one embodiment, the present invention is a valve assembly which includes a venturi valve member, a check valve connected to the venturi valve member, an air box, and a first conduit in fluid communication with and connected to the air box. A housing is part of the check valve, where the housing is connected to and in fluid communication with the first conduit and the venturi valve member, and a second conduit is also connected to and in fluid communication with the venturi valve member. A valve plate is moveably disposed in the housing, and the valve plate is moveable between a plurality of closed positions and an open position. 
         [0012]    A flow restricting nozzle is formed as part of the air box, and in a first mode of operation, pressurized air flows from the venturi valve member through the housing of the check valve, applying pressure to the valve plate such that the valve plate moves to an open position, allowing the pressurized air to flow through the check valve. The check valve remains in the open position because of a pressure balance around the valve plate created by the back pressure generated by the flow restricting nozzle. When the first conduit becomes disconnected from the air box, the pressure balance around the valve plate is removed, and the pressurized air flowing from the venturi nozzle flows into the housing and places the check valve in one of the closed positions, preventing air from flowing into the first conduit. 
         [0013]    The valve assembly also includes a second mode of operation, in which a vacuum from the air box draws air through the venturi valve member and the housing of the check valve, placing the valve plate in an open position. In the second mode of operation, if the first conduit becomes disconnected from the air box, the venturi valve member and valve plate are no longer exposed to the vacuum from the air box, and the check valve moves to one of the closed positions. 
         [0014]    There is a pressure drop across the venturi valve member during the first mode of operation and the second mode of operation, which creates a vacuum in the second conduit, drawing purge vapor from the second conduit into the venturi valve assembly. 
         [0015]    A first inner surface is formed as part of the housing, and a second inner surface formed as part of the housing on the opposite side of the housing in relation to the first inner surface. A guide is located in the housing between the first inner surface and the second inner surface, and the valve plate is slidably mounted on the guide. A spring is located in between and in contact with the valve plate and the second inner surface, such that the spring biases the valve plate toward the first inner surface. During the first mode of operation, the pressurized air applies pressure to the valve plate in the opposite direction of the force applied to the valve plate from the spring, overcoming the force of the spring, such that the valve plate moves to the open position. The pressure balance provided by the flow restricting nozzle maintains the valve plate in the open position. 
         [0016]    During the second mode of operation, the vacuum from the air box draws the valve plate toward the second inner surface, overcoming the force of the spring, and places the valve plate in the open position. 
         [0017]    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 
         [0018]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0019]      FIG. 1  is a first diagram of an airflow system for a vehicle having a venturi valve assembly, according to embodiments of the present invention; and 
           [0020]      FIG. 2  is a diagram showing the correlation between a pressure chart and part of an airflow system for a vehicle having a venturi valve assembly, according to embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    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. 
         [0022]    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. 
         [0023]    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 . 
         [0024]    A fourth conduit  20   d  is in fluid communication with the third conduit  20   c  and a fifth conduit  20   e,  and the fifth conduit  20   e  places a turbo purge valve  22  in fluid communication with a venturi valve assembly  24 . There is a first check valve  26  disposed in the fourth conduit  20   d,  and a second check valve  28  disposed in the fifth conduit  20   e.  There is also a carbon canister  30  in fluid communication with the turbo purge valve  22  through the use of a sixth conduit  20   f.    
         [0025]    A seventh conduit  20   g  provides fluid communication between the venturi valve assembly  24  and the second conduit  20   b,  such that pressurized air produced by the turbocharger  14  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 . The venturi valve assembly  24  includes venturi valve member  24   a  shown in  FIG. 1  and a check valve  32 , which is connected to the eighth conduit  20   h.    
         [0026]    Referring to the Figures generally, in 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 . The engine creates a vacuum drawing air into the intake manifold  18 . This vacuum also causes the first check valve  26  to open, which draws purge vapor from the canister  30  through the turbo purge valve  22  (when the valve  22  is open), and into the intake manifold  18 . This same vacuum pressure also causes the second check valve  28  to close. 
         [0027]    When the turbocharger  14  is activated, 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 mode of operation, the manifold  18  is operating under positive pressure. 
         [0028]    When the turbocharger  14  is activated, and pressurized air is passing through the seventh conduit  20   g,  the venturi valve member  24   a , the check valve  32  (when the check valve  32  is in an open position), and the eighth conduit  20   h,  a vacuum is created and air is drawn from the fifth conduit  20   e  through venturi valve assembly  24 , such that the air passes through the eighth conduit  20   h  and into the air box  12 . This vaccum in the fifth conduit  20   e  also opens the second check valve  28 , and purge vapor from the canister  30  passes through the turbo purge valve  22  (when the valve  22  is open), through the venturi valve  24   a,  the check valve  32 , and into the air box  12 . The purge vapor then flows through the turbocharger  14 , the throttle  16 , and into the intake manifold  18 . 
         [0029]    The check valve  32  includes a housing  36 , where the venturi valve  24   a  is connected to the housing  36 , and the eighth conduit  20   h  is also connected to the housing  36 . Disposed in the housing  36  is also a valve plate  38  mounted on a guide  40 . Also located within the housing  36  and at least partially surrounding the guide  40  is a biasing member, which in this embodiment is a spring  42 . The spring  42  biases the valve plate  38  towards the venturi valve member  24   a  such that when air is not passing through the venturi valve member  24   a,  the spring  42  applies enough force to the valve plate  38  that the valve plate  38  contacts a first inner surface  44  of the housing  36 , placing the valve  32  in a closed position. 
         [0030]    There is a flow restricting nozzle  46  formed as part of the air box  12 , as shown in  FIG. 2 . When the turbocharger  14  is generating pressurized air, the pressure from the air flow overcomes the force applied to the valve plate  38  by the spring  42 , moving the valve plate  38  away from the first inner surface  44 , and towards a second inner surface  48 . The spring  42  is also in contact with the second inner surface  48  and the valve plate  38 . The flow restricting nozzle  46  limits the amount of flow of air into the air box  12  from the eighth conduit  20   h,  allowing pressure to build in the eighth conduit  20   h,  creating a backpressure, which therefore creates a pressure balance around both sides of the valve plate  38 . This pressure balance around the valve plate  38 , along with the force applied to the valve plate  38  by the spring  42 , maintains the valve plate  38  in an open position. 
         [0031]    The valve plate  38  is considered to be in the open position when the valve plate  38  is not in contact with either the first inner surface  44  or the second inner surface  48 , regardless of how close the valve plate  38  is to either surface  44 ,  48 , because air is allowed to flow from the venturi valve member  24   a  and around the valve plate  38  in the housing  36  and into the eighth conduit  20   f,  even if there is a relatively small gap between the valve plate  38  and either of the surfaces  44 ,  48 . The location of the valve plate  38  changes because the operation of the engine varies the level of pressurized air generated by the turbocharger  14  during the first mode of operation, and varies the level of vacuum from the air box  12  during the second mode of operation. This varies the air flow around the valve plate  38  in the housing  36 . 
         [0032]    The valve  32  also includes an automatic closing feature if the eighth conduit  20   h  were to ever become disconnected from the air box  12 . The valve  32  has multiple closed positions, and in one of the closed positions, the valve plate  38  is in contact with the first inner surface  44 , and in another of the closed positions, the valve plate  38  is in contact with the second inner surface  46 . If the eighth conduit  20   h  is disconnected from the air box  12 , due to the conduit  20   h  breaking or the like, the flow restricting nozzle  46  no longer functions to limit the air flow through the conduit  20   h,  thereby eliminating the back pressure and therefore the pressure balance around the valve plate  38 . Under this condition, the pressurized air from the turbocharger  14  flowing through the venturi valve member  24   a  applies enough pressure to the valve plate  38  to overcome the force of the spring  42 , moving the valve plate  38  away from the venturi valve member  24   a  and toward the second inner surface  48  such that the valve plate  38  contacts the second inner surface  48 , placing the check valve  32  in a closed position. 
         [0033]    This automatic closing feature provides several features. One of which is an on-board diagnostic (OBD) function, and another is the prevention of vapor from the canister  30  from entering into the atmosphere. When the turbocharger  14  is generating pressurized air, and purge vapor is passing through the purge valve  22 , some level of vaccum should be detectable in the canister  30  by a pressure sensor  34 . If the check valve  32  is closed because of the detachment of the eighth conduit  20   h  from the air box  12 , the air in the eighth conduit  20   h  and the seventh conduit  20   g  remains pressurized, but because there is no air flow, the vacuum pressure in the fifth conduit  20   e  is eliminated, and the second check valve  28  moves to a closed position. If the turbocharger  14  is generating pressurized air, and the purge valve  22  is open, but there is no vacuum pressure in the fifth conduit  20   e  to open the second check valve  28  and allow the vapors from the canister  30  to flow through the valve  22 , the pressure sensor  34  detects no pressure change in the canister  30 , indicating that the system  10  has a malfunction. Also, because the check valve  32  is closed, the vapors (hydrocarbon rich air) in the canister  30  are prevented from venting to the atmosphere. 
         [0034]    This is also shown in the chart, shown generally at  50  in  FIG. 2 , where the first line  52  indicates different pressure levels along the venturi valve member  24   a,  the check valve  32 , and the eighth conduit  20   h , when the eighth conduit  20   h  is connected to the air box  12 . The chart  50  also includes a second line  54  which indicates different pressure levels along the venturi valve member  24   a,  the check valve  32 , and the eighth conduit  20   h , when the eighth conduit  20   h  is disconnected from the air box  12 . 
         [0035]    The first line  52  has a first zone  56  which shows the pressure drop across the venturi valve member  24   a.  A portion of this zone  56  has negative pressure, which indicates the vacuum pressure used to draw the purge vapor into the venturi valve assembly  24  from the fifth conduit  20   e.  The first line  52  also has a second zone  58 , which shows the small difference in pressure on each side of the valve plate  38 , and when the force of the spring  42  is combined with the air pressure on each side of the valve plate  38 , the above-mentioned pressure balance on each side of the valve plate  38  is achieved, maintaining the valve plate  38  in the open position, as shown in  FIG. 2 . The first line  52  also includes a third zone  60 , which shows a small pressure drop through the eighth conduit  20   h,  and a fourth zone  62  which shows the pressure drop to zero pressure once the air reaches the air box  12  after passing through the flow restricting nozzle  46 . 
         [0036]    The second line  54  has three zones, the first zone  64  which indicates the pressure along the venturi valve member  24   a,  a second zone  66  showing the pressure drop across the check valve  32 , and a third zone  68  indicating little or no pressure in the eighth conduit  20   h.  The three zones  64 ,  66 ,  68  of the second line  54  indicate the pressure levels when the eighth conduit  20   h  is disconnected from the air box  12 , and the check valve  32  is in a closed position. This pressure level in the first zone  64  is constant, because the check valve  32  is in a closed position, and the valve plate  38  is in contact with the second inner surface  48 . The second zone  66  shows the pressure change across the check valve  32 , where one side of the valve plate  38  is exposed to the pressurized air generated by the turbocharger  14  flowing through the venturi valve member  24   a,  and the other side of the valve plate  38  receives force from the spring  42 , but because there is no pressure in the eighth conduit  20   h  (due to the eighth conduit  20   h  being detached from the air box  12 ), there is little to no pressure on the other side of the valve plate  38 , as indicated by the decrease in the second line  54  in the second zone  66 . The third zone  68  of the second line  54  indicates little or no pressure in the eighth conduit  20   h;  this occurs because the eighth conduit  20   h  being disconnected from the air box  12 , and therefore the flow restricting nozzle  46  doesn&#39;t provide flow restriction of the pressurized air, producing little to no pressure in the eighth conduit  20   h.    
         [0037]    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.