Abstract:
A method and apparatus for reducing or preventing hydrocarbon emissions from an air induction system of an automotive vehicle directs hydrocarbon from induction system into the crankcase when the vehicle is not in operation.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to systems and methods for controlling hydrocarbon emissions in automotive vehicles.  
       BACKGROUND OF THE INVENTION  
       [0002]     The automotive industry has actively sought improved emissions reduction, including reduction in emissions due to gasoline evaporation. Gasoline includes a mixture of hydrocarbons ranging from higher volatility butanes (C 4 ) to lower volatility C 8  to C 10  hydrocarbons. When vapor pressure increases in the fuel tank due to conditions such as higher ambient temperature or displacement of vapor during filling of the tank, fuel vapor may flow through openings in the fuel tank and escape into the atmosphere. To prevent fuel vapor loss into the atmosphere, the fuel tank is vented into a canister called an “evap canister” that contains an adsorbent material such as activated carbon granules. As the fuel vapor enters an inlet of the canister, the fuel vapor diffuses into the carbon granules and is temporarily adsorbed. The size of the canister and the volume of the adsorbent material are selected to accommodate the expected fuel vapor generation. One exemplary evaporative control system is described in U.S. Pat. No. 6,279,548 to Reddy, which is hereby incorporated by reference.  
         [0003]     Evaporative emission control systems have advanced to the point where vehicle induction system or air intake system hydrocarbon emissions account for a significant portion of remaining hydrocarbon emissions. Intake system hydrocarbon emissions may arise from diffusion of a small amount of fuel left in fuel injectors after engine shut down or from liquid fuel wetting the walls of the intake manifold. Hydrocarbon traps containing an adsorbent such as activated carbon may be added to the air intake to absorb such emissions, which may then be desorbed by engine intake air when the engine is operating, but would add cost and complexity to manufacture of the vehicle. A less costly but still effective way to eliminate or reduce the emissions would be desirable.  
       SUMMARY OF THE INVENTION  
       [0004]     In an embodiment of the invention, a method for reducing or preventing hydrocarbon emissions of residual hydrocarbons in an air induction system when an automotive vehicle is not in operation directs residual hydrocarbon (present as vapor, liquid, or both) in the vehicle air induction system into the engine oil crankcase. The crankcase retains the hydrocarbon, and the engine oil may absorb such low amounts of hydrocarbon without detriment.  
         [0005]     In an embodiment of the invention, an apparatus for reducing or eliminating emissions of residual hydrocarbon present in an automotive vehicle air induction system when the vehicle is not in operation includes a vent or other opening located in an underside portion of the air induction system, an orifice or other opening in an engine oil crankcase, and a hollow connector between the vent and the orifice. The vent and orifice are opened when the vehicle is not in operation to allow any hydrocarbon in the air induction system to be introduced into the crankcase through the connector.  
         [0006]     In an embodiment of the invention, an induction hydrocarbon emission control system for an internal combustion engine having an air induction system connecting to engine cylinders, fuel injectors located in the air induction system positioned to inject fuel into intake ports, and a crankcase containing engine oil to lubricate a piston in the cylinder, the crankcase having a vent, includes a throttle valve located in the air induction system and a connective pathway from an underside outlet of the air induction system, the outlet being located between the throttle valve and the intake ports, to the crankcase vent.  
         [0007]     The invention further provides a method for reducing or preventing hydrocarbon emissions of residual hydrocarbons in a portion of an air intake system for an engine having a crankcase containing engine oil, in which, when the engine is not operating, the portion of the air induction system is vented into the crankcase.  
         [0008]     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  
       [0009]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0010]      FIG. 1  is a schematic diagram of a prior art engine positive crankcase ventilation (PCV) system;  
         [0011]      FIG. 2  is a schematic diagram of an induction system hydrocarbon emission control system according to the invention;  
         [0012]      FIG. 3  is a partially cut-away perspective view of an engine and hydrocarbon emission control system for a vehicle according to the invention; and  
         [0013]      FIG. 4  is a graph illustrating measured hydrocarbon emissions for a simulated air induction system.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]     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.  
         [0015]     Positive crankcase ventilation (PCV) systems reduce emission of contaminants by recirculating blowby gases and crankcase vapors into the engine cylinders for burning. During operation of an automotive vehicle with an internal combustion engine, crankcase vapors are drawn through a liquid separator and into the air intake manifold (a part of the air induction system) where they will be drawn into the cylinders by intake manifold vacuum.  FIG. 1  schematically illustrates a prior art design of a positive crankcase ventilation orifice. In  FIG. 1 , PCV orifice  10  in engine PCV system  40  is mounted in an oil separation portion  42  of a cylinder head cam cover of the crankcase. The orifice  10  connects directly with a PCV hose  44  that leads to a fitting  46  on the engine intake manifold  48  for recirculating blowby and crankcase vapors into the engine cylinders, not shown, to which the intake manifold connects.  
         [0016]      FIG. 2  schematically illustrates a positive crankcase ventilation (PCV) system in an embodiment of the induction system hydrocarbon emission control system according to the invention. In  FIG. 2 , PCV orifice  1  in engine PCV system  20  is mounted in oil separation portion  22  of a cylinder head cam cover. The orifice  1  connects directly with a PCV hose  24  to a fitting  26  on a bottom portion  18  of engine intake manifold  28 . During engine operation the PCV system operates as before for recirculating blowby and crankcase vapors into the engine cylinders to be incinerated. When the engine is not in operation, hydrocarbon vapor that is present in the air induction system is heavier than air and sinks to the bottom of manifold  28 , where it can pass through hose  24  into the cylinder head and crankcase.  
         [0017]      FIG. 2  shows a flat bottom  18 , but bottom  18  may also be shaped to help direct hydrocarbon vapor or liquid into hose  24 . For example, bottom  18  may have a funnel shape or other depression around fitting  26  that would encourage passage of hydrocarbon into hose  24  and from there into the crankcase.  
         [0018]     The cut-away diagram of  FIG. 3  further illustrates the invention as an embodiment of an engine and induction hydrocarbon emission control system for a vehicle. The engine  50  has an intake manifold  60  located near PCV orifice  70 . Intake manifold  60  receives air drawn through air filter  62  and air induction hose  64  into opening  66 . Hose  64  is shown detached from opening  66  for simplification. A bottom section of the intake manifold  60  close to PCV orifice  70  has a vent  76 , connected through PCV hose  74  to PCV orifice  70 . During engine operation, fuel injector  52  injects fuel (hydrocarbon) into an engine cylinder. When the engine is not operating, the hydrocarbon of the fuel may drip from the injector and vaporize in intake manifold  60 . Fuel vapor may also wet the wall of intake manifold  60  or other parts of the air induction system, represented by hydrocarbon drops  54 . If the hydrocarbon remains in the air induction system, it may be lost (e.g., through air cleaner  62 ) as undesirable emissions. The hydrocarbon is re-directed into the engine crankcase to capture the hydrocarbon and prevent its emission from the engine  50 .  
         [0019]     Results of a test simulating fuel vaporization using butane gas injection into an air intake manifold with and without the relocated crankcase vent according to the invention are represented by the graph of  FIG. 4 . Bar  100  represents a measured hydrocarbon loss (in grams) for an existing air induction system of 1.4 grams of hydrocarbon, while bar  110  represents a reduction to a loss of 0.3 grams of hydrocarbon under the same conditions with a modified air induction system according to the invention as illustrated by  FIG. 3 .  
         [0020]     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.