Abstract:
An integrated air fuel module ( 10 ) for an internal combustion engine reduces or eliminates the escape of hydrocarbon evaporative emissions from the integrated air fuel module ( 10 ) system, sub systems and components. The integrated air fuel module ( 10 ) includes containment means ( 34 ), such as a valve ( 34 ) or carbon adsorber, that blocks the escape of evaporated hydrocarbon emissions from the air inlet ( 16 ) of an engine during engine off conditions. The module ( 10 ) provides a reduced number of potential external hydrocarbon leak and permeation paths to the surrounding atmosphere. Preferred geometries of the intake manifold ( 12 ) in the module ( 10 ) with the internal integration of other normally external systems, such as fuel injection ( 60 ) and positive crankcase ventilation ( 50 ) systems, accomplish the containment of evaporative emissions within or entering the air fuel module ( 10 ) between engine operating periods when the engine is shut down.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/149,142, filed Aug. 16, 1999. 
    
    
     TECHNICAL FIELD 
     This invention relates to control of engine evaporative emissions of hydrocarbons and to a low emission integrated air fuel module capable of containing such emissions. 
     BACKGROUND OF THE INVENTION 
     Automobile manufacturers have gone to great lengths to reduce emissions created by the vehicles they manufacture. Many sources of emissions have been pursued. The two major sources of emissions are the exhaust emissions (or ‘tail pipe emissions’) and the hydrocarbon or unburned fuel that evaporate from other sites on the vehicle (or ‘evaporative emissions’). In today&#39;s vehicles, fuel tanks are vented through carbon canisters so that hydrocarbons are removed from the air escaping from the tank due to pressure differentials. These evaporative emissions are stored until they can be pulled into the engine and consumed. This type of system is very effective at stopping hydrocarbon emissions from escaping from the fuel tank system. 
     There are sources other than the fuel tank that can contribute to the hydrocarbon evaporative emissions of a vehicle. One such source is the ‘breathing’ of the air induction system during hot soak and diurnal temperature cycling. Unburned fuel resident in the intake system after engine shutdown evaporates into the air in the system. Air exchanges, between the air induction system and the atmosphere, carry these evaporated hydrocarbon emissions into the atmosphere. Activated charcoal or ‘carbon adsorbers’ have previously been installed in air cleaner housings to reduce these hydrocarbon emissions. The carbon adsorber draws in and holds the hydrocarbons until the engine is started and the air flow past the adsorber pulls the hydrocarbons back into the engine and purges the adsorber. 
     Another common source of hydrocarbon emmissions is seal leakage of both high pressure and low pressure fuel components and systems. Current fuel delivery systems contain many such potential leak paths. These include O-rings, injector and fuel rail interfaces, fuel regulator diaphragm, end plugs, fuel rail inlet and outlet, service valve, and crankcase ventilation system interfaces and joints. Each of these locations has the potential of leaking emissions to the surrounding environment. 
     A third common source of hydrocarbon emissions to the atmosphere is permeation of the fuel through the materials of the system. Hydrocarbons can permeate most composite and elastomer materials commonly used in the automotive engine environment. Small amounts of hydrocarbons therefore leak through the walls of composite components in the system and through the elastomer O-rings and seals at the interfaces in the system. This leakage is increased with higher fuel pressures driving the hydrocarbons out through the walls. 
     The above contributors are generally small in relation to the total evaporative emissions of the vehicle and automobile manufacturers can meet the current standards without further development or control. However, in order to meet zero or near zero evaporative emissions requirements, engine suppliers and vehicle manufactures will have to reduce the number of leak and permeation sites that can emit hydrocarbons. 
     SUMMARY OF THE INVENTION 
     The present invention provides an integrated air fuel module for an internal combustion engine that reduces or eliminates the escape of hydrocarbon evaporative emissions from the integrated air fuel module system, sub systems and components. The integrated air fuel module of the present invention includes containment means, such as a valve or carbon adsorber, that blocks the escape of evaporated hydrocarbon emissions from the air inlet of an internal combustion engine during engine off conditions. The module provides a reduced number of potential external hydrocarbon leak and permeation paths to the surrounding atmosphere. Preferred geometries of the intake manifold in the module with the internal integration of other normally external systems, such as fuel injection and positive crankcase ventilation systems, accomplish the containment of evaporative emissions within or entering the air fuel module between engine operating periods when the engine is shut down. 
    
    
     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a conceptual cross-sectional view of a low evaporative emissions integrated air fuel module including features according to the invention; 
     FIG. 2 is a cross-sectional view showing an exemplary form of containment valve in the module inlet portion; and 
     FIG. 3 is an exterior pictorial view of a module for a V-8 engine including features of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIG. 1 of the drawings in detail, numeral  10  generally indicates an exemplary low evaporative emissions integrated air fuel module for an internal combustion engine, the module including features according to the invention. Module  10  includes a housing  12  internally defining an air system  14 . The air system includes in series an inlet portion  16  for admitting charge air, a throttle control portion  18  having a throttle valve  20  for controlling air flow, a connecting portion  22 , or zip tube, for tuning the air flow, an inlet plenum  24  for distributing and balancing the air flow, and a plurality of intake runners  26 . The runners  26  connect individually with the plenum and connect the plenum  24  with outlet ports  28  along a cylinder head interface  30  coplanar with a mounting flange  32  of the housing  12 . The runners  26  and outlet ports  28  distribute the air flow to inlet ports of an engine, not shown, for intermittent admission to associated cylinders during operation of the engine. 
     In accordance with the invention, the inlet portion includes containment means for limiting the escape of evaporative emissions from within the air system through the inlet portion between periods of engine operation, that is, when the engine is stopped. Air system  14  includes an exemplary embodiment of containment means in the form of a containment valve  34 , shown in further detail with the inlet portion  16  in FIG.  2 . Valve  34  includes a pivotable edge mounted flapper type valve element  36  including a sharp edged sealing portion  38  engagable, when the valve is closed, with a valve seat  40  of an air inlet  42  in the inlet portion  16 . 
     A variable force spring  44  engages the valve element to bias the valve in a closing direction. The spring  44  may be a curved spring steel tape shaped similarly to a steel rule tape but used as a spring. In the closed position shown in solid lines, the spring is positioned to exert a maximum force to hold the valve element  36  firmly against the valve seat  40 . When the valve is opened, the spring flattens and bends easily to allow opening of the valve against a lower spring force. 
     An actuator  46  is provided for pivoting the valve element to the open position shown in dashed lines in FIGS. 1 and 2. Any suitable form of actuator may be used which is responsive to signals indicating operating and shutdown conditions of the engine. The illustrated actuator represents a vacuum motor  46  that opens the valve in response to vacuum in the air system  14 , which indicates that the engine is in operation. The vacuum motor  46  allows the valve to be closed and held in place by the spring  44  when loss of vacuum with near ambient pressure in the air system indicates that the engine is stopped. 
     Containment valve  34  and vacuum motor  46  are only exemplary of the many forms of suitable containment means and actuators which could be used within the scope of the invention. Any suitable electric, pneumatic or fluid actuator might be used with appropriate controls if needed. Containment means may include many forms of valves, including pivoting blades, plungers, reed valves and other check valves, as examples. Instead of valves, carbon adsorbers may provide adequate containment of evaporative emissions and could be used as containment means within the scope of the invention. 
     In accordance with the invention, the air fuel module  10  also includes a positive crankcase ventilation (PCV) system  50 , which is primarily contained within the air system  14  of the housing  12 . The PCV system  50  includes a ventilation inflow passage  52  that connects the air inlet portion between the containment valve  34  and the throttle valve  20  with a ventilation outlet  54  at the cylinder head interface  30  of the housing. A ventilation outflow passage  56  is also provided which extends from the interface  30  to the air system  14  downstream of the throttle valve  20 . Passages  52 ,  56  are defined by walls that are primarily contained within the housing defined air system  14  of the module  10 . When the module  10  is installed on an engine, the passages  52 ,  56 , including outlet  54 , are connected with the crankcase chamber of the engine for passing ventilation air through the crankcase. A PCV valve  58  is located in the ventilation outflow passage  56  to control the flow of air and crankcase vapors through the PCV system. 
     In accordance with the invention, the air fuel module  10  further includes a fuel injection system  60  that is primarily contained within the air system  14  of the housing  12 . Fuel injection system  60  includes one or more fuel rails  62  that extend longitudinally within the housing  12 . A plurality of fuel injectors  64 , generally one for each engine cylinder, are connected with the fuel rail(s) to receive pressurized fuel supplied from a source external to the module housing  12 . The fuel rail(s)  62  and the injectors  64  are mounted entirely within the housing  12  and the air system  14  defined by the housing. The injectors are positioned to spray fuel out through the outlet ports  28  from the runners  26  to mix with air in the intake ports and cylinders of the associated engine, not shown). Preferably, the mounting locations of the injectors and all the connections with the fuel rails and of the fuel rails with incoming fuel lines are contained with the air system  14 . Thus, any leakage of evaporative emissions from the internal portions of the fuel system will be contained within the air system and drawn into the engine during engine operation. 
     In addition to potential leakage of evaporative emissions from joints between various elements of the fuel system, the PCV system and backflow of gases from connected engine cylinders and intake ports, additional emissions may occur by permeation of fuel vapors and the like through molded plastic internal walls of the various systems in the housing  12 . Thus, a molded housing may require treatment of at least the outer walls to maintain containment of evaporated hydrocarbons and other substances within the housing when the engine is shut down. Alternatively, the housing  12 , or at least its outer walls, may be made from cast aluminum or other metal having low permeability. 
     In the embodiment of FIG. 1, the housing  12  is preferably made as a plastic molding in three sections, an entry conduit  66 , an upper manifold  68  and a lower manifold  70 . The lower manifold  70  includes the mounting interface  30  and the lower portions of the plenum  24  and runners  26  as well as the components of the fuel injection system  60 . The upper manifold  68  includes upper portions of the plenum  24  and runners  26 . The PCV system passages  52 ,  56  extend into both manifold sections  68 ,  70  but the PCV valve  58  is mounted in the upper manifold. The entry conduit  66  is mounted on the upper manifold  68  and is removable to allow access to service the PCV valve. 
     Referring particularly to FIG. 3 of the drawings, the air fuel module  72  there disclosed further includes within a housing  74 , a coolant crossover  76  having internal passages, not shown, for carrying coolant between cylinder banks of an associated V-8 engine. A liquid cooled electrical alternator  78  is mounted within the crossover  76  and is cooled by coolant in the passages during engine operation. The figure also shows a side mounted electric throttle control  80  for the internal throttle valve. The housing  74  is made in two sections, including an upper manifold  82  mounted on a lower manifold  84 . The latter includes a mounting flange  86  coplanar with the lower interface, not shown, that mounts on the associated engine cylinder heads. Internally the elements of the module  72  are essentially similar to those of module  10  in FIG.  1 . 
     In operation of an engine having an air fuel module  10  as shown in FIG. 1, the containment valve  34  is opened upon starting of the engine, and remains open, allowing the entry of charging air into the module air system  14 . Vaporized hydrocarbons and other vapors retained in the air system are drawn into the engine with the new air charges and burned in the engine. Any fuel vapors seeping into the air system  14  during engine operation are likewise drawn into the engine and burned along with the crankcase vapors flushed out by the PCV system  50 , which are drawn from the engine crankcase by vacuum in the module downstream of the throttle valve  20 . The inlet air controlled by the throttle valve and including any added crankcase vapors continues through the manifold connecting portion or zip tube  22  and enters the inlet plenum  24 . The air is then drawn into the individual engine cylinders through the intake runners  26  and outlet ports  28  of the module into associated intake ports of the engine. Fuel is added to the incoming air by the fuel injectors  64  that are part of the fuel injection system  60  enclosed within the air fuel module  10 . The fuel is sprayed from the module directly into the cylinder head intake ports, not shown, and normally against the intake valve to assist vaporization. 
     When the engine is stopped, the spring  44  closes the containment valve  34 , sealing off the inlet portion  16  of the air system  14 . Fuel and other vapors in the air system  14  or entering the system  14  from the associated engine ports or from the internal PCV and fuel injection systems  50 , are thus contained within the air system  14  and prevented from escaping into the atmosphere. Restarting of the engine again draws the stored vapors into the engine and disposes of them by burning. 
     While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.