Abstract:
An improved engine emission control for controlling both nitrous oxide emissions through an exhaust gas recirculation system and evaporative fuel emissions. These gases (exhaust and evaporated fuel) are mixed with the intake charge in a mixing chamber that surrounds the intake passage so as to insure good mixing at an upstream point removed from the combustion chambers so that a uniform mixture will be delivered to each chamber and there will be uniformity in the added mixture between the chambers.

Description:
BACKGROUND OF INVENTION  
         [0001]    This invention relates to an internal combustion engine and more particularly to an improved system for preventing the emission of unwanted gases to the atmosphere including nitrous oxides (NO X ) and evaporated fuel emissions.  
           [0002]    In internal combustion engines in an effort to improve performance and reduce the emission of unwanted exhaust gases constituents, it has been proposed to utilize a system for recirculating exhaust gases (EGR) to the combustion chamber. By returning some of the exhaust gases to the combustion chamber, the temperature in the combustion chamber can be reduced and the emission of objectionable nitrous oxides can be reduced. Generally, the flow of these exhaust gases is controlled by an EGR valve depending upon engine performance and the exhaust gases are introduced into the intake system somewhere between the air inlet and the combustion chambers.  
           [0003]    It has been found, however that conventional systems do not provide the desired operation because the exhaust gases may be delivered unevenly to the combustion chambers of the engine and/or not thoroughly mixed with the intake air so that their optimum performance can be achieved. In addition, this type of system can cause unequal distribution from cylinder to cylinder as well as variations within the cylinder, which also contribute to unstable running and unstable combustion.  
           [0004]    It is, therefore, a principle object to this invention to provide an improved EGR system wherein the exhaust gases are well mixed with the charge that is delivered to the combustion chambers so as to eliminate the aforenoted problems.  
           [0005]    A similar situation deals with the treatment of evaporative vapors from the fuel, primarily those that accumulate in the fuel tank above the fuel as the fuel level depletes. It has been proposed to employ a carbon canister or canisters containing other materials that will absorb the fuel vapors. These fuel vapors are then periodically delivered to the engine induction system for combustion therein so that the raw fuel is not discharged to the atmosphere.  
           [0006]    The same distribution problems and homogeneous mixture problems as are present with the exhaust gas recirculation system are also true with these evaporative fuel emission systems.  
           [0007]    It is, therefore, a still further object to this invention to provide an improved evaporative fuel emission control system for an engine.  
           [0008]    It is a yet further object to this invention to provide an improved arrangement for mixing both exhaust recirculating gas systems and evaporative emission control systems that combines the products and mixes them well with the intake air charge.  
         SUMMARY OF INVENTION  
         [0009]    The features of this invention are adapted to be embodied in an internal combustion engine that has at least one combustion chamber and an induction system for delivering an air charge to the combustion chamber. The induction system includes at least one generally cylindrical conduit portion.  
           [0010]    In accordance with a first feature of the invention, the engine includes an exhaust system for delivering combustion products from the combustion chamber to the atmosphere. An exhaust gas recirculating system recirculates a portion of the combustion products back to the combustion chamber. This exhaust gas recirculating system includes a mixing chamber encircling at least a portion of the induction system generally circular conduit portion. A plurality of circumferentially spaced apertures are provided in the induction system generally cylindrical conduit portion for communicating the mixing chamber with the interior of the induction system generally cylindrical conduit portion. An exhaust gas re-circulating conduit communicates the exhaust system with the mixing chamber.  
           [0011]    A second feature of the invention is adapted in an engine as set forth in the first paragraph of this section and that includes a fuel system for delivering fuel to the engine for combustion in the combustion chamber. An evaporative fuel control system is provided for preventing the emission of evaporated fuel from the fuel system to the atmosphere. The evaporative fuel control system includes a mixing chamber that encircles at least a portion of the induction system generally cylindrical conduit portion. A plurality of circumferential spaced apertures are formed in the induction system generally circular conduit portion for communicating the mixing chamber with the interior of the induction system generally cylindrical conduit portion. An evaporative fuel control conduit communicates the evaporative fuel control system with the mixing chamber. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0012]    [0012]FIG. 1 is an end elevational view of an internal combustion engine constructed in accordance with an embodiment of the invention.  
         [0013]    [0013]FIG. 2 is a view of the engine as shown in FIG. 1 but looking from the opposite end thereof.  
         [0014]    [0014]FIG. 3 is an enlarged cross sectional view taken along the line  3 - 3  of FIG. 2 and showing the relative position of the throttle valve so that its axis can be related to the remaining components. 
     
    
     DETAILED DESCRIPTION  
       [0015]    An internal combustion engine constructed in accordance with an embodiment of the invention is identified generally by the reference numeral  11  and is shown only partially. That is, the illustrations in FIGS. 1 and 2 shows only the portion of the engine above the crankcase because the invention deals primarily with the emission control systems for the engine rather than the internal mechanical components of the engine. It is believed that from the following description, those skilled in the art will be readily able to understand and practice the invention without knowing more of the internal details of the engine which can be employed with a wide variety of engines.  
         [0016]    The engine  11  is comprised of a cylinder block  12  having an upper crankcase portion  13  in which its crankshaft is rotatably journalled in a known manner. The lower end of the crankcase is not shown for the aforenoted reasons.  
         [0017]    The cylinder block  12  forms a plurality of combustion chambers along with a cylinder head  14  that is affixed thereto and with pistons that reciprocate in the cylinder bores of the cylinder block. Again, the number of cylinders and the arrangement in the cylinder block may be of any suitable type.  
         [0018]    An induction system is provided for delivering an air charge to these combustion chambers. This induction system includes generally an air inlet device, indicated generally by the reference numeral  15  and which includes an atmospheric air opening  16  into which atmospheric air is inducted. A plenum chamber  17  is formed within this inlet device  15  and a suitable filtration element is interposed between the inlet  16  and an outlet portion  18 .  
         [0019]    This outlet portion  18  communicates with a throttle body  19  in which a butterfly type throttle valve  21  is rotatably journalled on a throttle valve shaft  22 . This throttle valve  21  is controlled in any suitable manner.  
         [0020]    The throttle body  19  has a generally cylindrical outlet conduit  23 , which, in turn, communicates with a further intake system plenum chamber  24 . This further plenum chamber  24  serves individual runner pipes  25  of an intake manifold, indicated generally by the reference numeral  26 , and which may have a number of runners  25  equal to the number of the cylinders in the cylinder block  12 . Not all of these conduits are illustrated in the figures. These runners  25  are connected to a manifold flange  27  that is suitably affixed to the inlet side of the cylinder head  14 .  
         [0021]    The cylinder head  14  is provided with suitable intake passages and valve mechanism for delivering the air charge to the combustion chambers. This may include one or a plurality of intake valves operated in any desired manner.  
         [0022]    In addition, a fuel supply system is provided for delivering fuel to the combustion chambers for mixture with the air and combustion in the combustion chambers. This fuel supply system includes a remotely positioned fuel tank (not shown) and suitable supply conduits that deliver fuel to fuel injectors, which are not shown, but which are received in suitable receptacle openings  28  formed in the manifold flange  27  or in the cylinder head  14 . This fuel supply system also includes an evaporative emission system that includes a canister (not shown) that communicates with the area above the fuel in the fuel tank and delivers it to the induction system for mixing with the intake air in a manner, which will be described shortly.  
         [0023]    The fuel air mixture, which has been delivered to the combustion chambers of the engine, is ignited in a suitable manner i.e. by spark plugs in the event the engine  11  is a spark ignited engine. The exhaust gases are then delivered to the atmosphere through an exhaust manifold, indicated generally by the reference numeral  29 . This exhaust manifold  29  has a plurality of runners that are integrally connected to an exhaust flange  31  that is fixed to the side of the cylinder head  14  opposite the intake manifold flange  27 . These individual runners have a common outlet  32  that communicates with a suitable exhaust system (not shown).  
         [0024]    In order to reduce the amount of nitrous oxides formed in the combustion chambers and delivered to the atmosphere, an EGR system is employed. This includes an EGR conduit that comprised of a pick up tube  33  that communicates with the exhaust manifold  29  and which has an outlet end in a fitting portion  34  of the manifold flange  31 .  
         [0025]    An EGR cooler, indicated generally by the reference numeral  35  is connected to this flange  31  by a flange  36  and threaded fasteners  37 . This EGR cooler  35  has a double wall construction that is comprised of an inner tube through which the exhaust gases pass and an outer tube  38  that defines a cooling jacket around this inner tube. A coolant inlet  39  is provided at one end of this cooling jacket and receives coolant from the engine cooling system. A coolant discharge  41  at the other end of the EGR cooler  35  discharges the coolant back into the engine cooling system.  
         [0026]    The amount of recirculated exhaust gasses is controlled by an EGR valve  40  that operates on any desires strategy and to which the cooled exhaust gases are delivered to by a fitting of the cooler  35 . The EGR valve  40  has a flange portion  42  that is suitably attached to an outer shell  43  of a mixing chamber, which surrounds a generally cylindrical portion of the throttle body outlet or intake manifold inlet  23  as best seen in FIG. 3. The connection between the EGR valve flange portion  42  and the mixing chamber outer shell  43  is shown schematically at  44  in this figure.  
         [0027]    As may be seen, there is a fairly substantial cylindrical area  45 , which surrounds the outer wall of the inlet section  23 . The inlet section  23  is provided with a plurality of circumferentially spaced openings  46 ,  47  and  48  that are spaced circumferentially around the center of the intake manifold conduit  23 . The openings  46 ,  47  and  48  are progressively larger in cross sectional area in the flow direction from the fitting  44  to the opposite sides so as to insure equal flow from them into the interior of the intake passage  23 .  
         [0028]    In addition, these openings are disposed so that they are not parallel to the access of the throttle valve shaft  23 , which is shown in broken lines in this figure. This further insures that there will be good mixing.  
         [0029]    In addition to mixing the exhaust gases in the mixing chamber  45 , an outlet  52  from the evaporative fuel canister also enters into this mixing chamber  45   50  as to insure good mixing of the evaporative fuel vapors with the intake air charge.  
         [0030]    Since this device is positioned immediately adjacent and downstream of the throttle valve  22  it will have sufficient distance also to travel before it reaches the individual combustion chambers and will pass through the plenum chamber  24  to further insure good missing and uniform distribution.  
         [0031]    Thus, from the foregoing description, it should be readily apparent that the described construction provides very good emission control by utilizing the mixing chamber that communicates with the intake system and which receives both exhaust gases for EGR control and evaporated fuel for evaporative fuel emission control. Of course, the foregoing description is that of a preferred embodiment of the invention and various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.