Abstract:
A fuel injection system for an internal combustion engine, and particularly a supercharged one that employs both an in-cylinder injector and a manifold injector. By using two fuel injectors, one in-cylinder and one in the intake manifold, it is possible to operate under light loads with stratified charge and obtain a good homogenous mixture for combustion in other engine speed and load ranges.

Description:
BACKGROUND OF INVENTION  
         [0001]    This invention relates to an internal combustion engine and particularly to a direct injected internal combustion engine provided with a supercharger.  
           [0002]    It has been proposed to employ direct cylinder injection for internal combustion engines. By utilizing direct injection, it is possible to operate the engine more efficiently and also to obtain greater power and still improve the efficiency. This can be done by achieving a condition referred to as “stratification” in the engine under some running conditions, normally lower speed and lower load conditions.  
           [0003]    As the performance of the engine is improved, however, it may be difficult for the direct injector to supply not only the minute quantities of fuel required under very low speed, low load conditions as well as the larger quantity of fuel necessary to obtain maximum power output. Although this can be done by providing injectors that have a higher capacity, then the ability to inject controlled small amounts of fuel under low load conditions becomes very difficult. Also, if the injection is set so as to provide adequate and carefully controlled small amounts of fuel, then fuel must be injected for a longer time period under high speed and high load conditions and this can result in unwanted exhaust gas constituents because of the fact that the fuel may not have had the time to vaporize before combustion starts.  
           [0004]    These problems are particularly prevalent when the engine has its power increased through the use of a supercharger or pressure-forming device for introducing the charge into the combustion chamber at pressures greater than atmospheric.  
           [0005]    It is, therefore, a principal object to this invention to provide an improved fuel injection system for a direct injected engine that permits accurate fuel control over a wide speed of engine load and speed ranges.  
           [0006]    It is a further object to this invention to provide an improved fuel injection system for a supercharged internal combustion engine.  
         SUMMARY OF INVENTION  
         [0007]    An internal combustion engine constructed in accordance with an embodiment of the invention is provided with a pair of relatively moveable components that define a combustion chamber, the volume of which varies cyclically during the engine operation. An induction system is provided for delivering an air charge to the combustion chamber. A first fuel injector is provided that injects fuel directly into the combustion chamber. A second fuel injector is provided for injecting fuel into an induction system that supplies an air charge to the combustion chamber. A control selectively controls the timing and duration of fuel injection from both of the fuel injectors.  
           [0008]    In accordance with a further feature of the invention, the engine is provided with a supercharger which is mounted upstream of the second fuel injector. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0009]    [0009]FIG. 1 is a cross sectional view taken through a single cylinder of an internal combustion engine constructed in accordance with an embodiment of the invention and showing the piston thereof at top dead center position in solid lines and at bottom dead center position in phantom lines.  
         [0010]    [0010]FIG. 2 is an enlarged cross sectional view, in part similar to FIG. 1, and shows primarily the upper end of the cylinder block and the cylinder head assembly.  
         [0011]    [0011]FIG. 3 is a graphical view showing the various ranges of engine speed, engine torque and the control arrangement and strategy in connection with the fuel injectors. 
     
    
     DETAILED DESCRIPTION  
       [0012]    Referring now in detail to the drawings and initially to FIGS. 1 and 2, an internal combustion engine constructed and operated in accordance with an embodiment of the invention is identified generally by the reference numeral  11 . The engine  11  is shown only by reference to a cross section through a single cylinder of the engine  11  and specifically taken along the axis of a cylinder bore  12  formed in a cylinder block  13  of the engine. Although the invention is described in conjunction with only a single cylinder, it should be readily apparent to those skilled in the art how the invention may be employed with engines having various cylinder numbers and cylinder configurations.  
         [0013]    The cylinder bore  12  is closed at its upper end by a cylinder head assembly  14  that is affixed to the cylinder block  13  in a known manner. The undersurface of the cylinder head assembly  14  is provided with one or more recesses  15  depending upon the number of cylinder bores  12 . These recesses  15  cooperate with the cylinder bores  12  and the heads of pistons  16  that reciprocate therein to form the combustion chambers of the engine  11 . As may be seen by the top dead center position shown in FIGS. 1 and 2, the cylinder head recess  15  forms the primary portion of the combustion chamber at top dead center and at times the reference numeral  15  will be referred to as the “combustion chamber”.  
         [0014]    The piston  16  is connected by a piston pin  17  to the small end of a connecting rod  18 . The big end of the connecting rod  18  is journalled on a respective throw  19  of a crankshaft  21 . The crankshaft  21  is rotatably journalled within a crankcase assembly that is formed by a skirt  22  of the cylinder block  13 , a bearing cap member  23  and an oil pan  24 , all of which are connected to each other in a suitable manner. The actual form of journaling for the crankshaft  21  can be of any desired type.  
         [0015]    An induction system, indicated generally by the reference numeral  25  is provided for delivering an intake air charge to the combustion chambers  15 . In accordance with a feature of the invention, the induction system  25  includes a supercharger  26 , which is, in the preferred embodiment, a turbocharger. This supercharger  26  is provided with an inlet  27  that draws atmospheric air through a suitable air filter and silencing arrangement. The supercharged air is then discharged through a supply conduit  28  to a throttle body  29  in which a flow controlling throttle valve  31  is provided.  
         [0016]    Downstream of the throttle valve  31 , the throttle body  29  cooperates with an inlet  32  of a plenum chamber  33  which extends generally longitudinally of the engine above the cylinder head assembly  14 .  
         [0017]    Intake manifold runners  34  extend from the plenum chamber  33  to cylinder head intake passages  35 , each of which communicate with a respective one of the cylinder head combustion chamber  15  through an intake valve  36 . It will be seen that the manifold runners  34  have curved portions  37  that terminate in straight sections  38  which cooperate with the generally straight cylinder head intake passages  35  so as to provide a direct and unobstructed airflow into the combustion chamber  15 .  
         [0018]    The intake valves  36  cooperate with valve seats  39  formed in the cylinder head recesses  15  in an appropriate manner. The intake valves  36  are opened and closed by an intake camshaft  41  that is journalled in the cylinder head assembly  14  in a known manner, as will be described later, and which is contained within a cam cover  42  that is detachably affixed to the cylinder head assembly  14 .  
         [0019]    A first series of fuel injectors of the direct injection type, one of which appears in the drawings and is indicated by the reference numeral  43 , are fixed in the cylinder head assembly  14  and have their discharge nozzles communicating with the combustion chamber  15  at one peripheral edge thereof. The fuel injectors  43  are supplied with fuel from a suitable fuel source and are controlled in a manner, which will be described hereinafter.  
         [0020]    A second series of fuel injectors of the manifold type, indicated generally by the reference numeral  44 , are mounted in the curved portions  37  of the intake manifold runners  34 . As may be seen in these figures, a spray axis  45  of each of these second fuel injectors  44  is aligned with a flow axis  46  of the straight portion  38  of the intake passage formed by the runners  34  and the cylinder head intake passages  35 . Thus, the fuel sprayed by the injectors  44  will be well mixed with the intake air and will not tend to impinge upon the walls of the intake passage.  
         [0021]    Spark plugs  47  are mounted in the cylinder head assembly  14  and are disposed generally on the axis of the cylinder bores  12 . These spark plugs  47  are fired by a suitable ignition system.  
         [0022]    Exhaust passages  48  are formed in the cylinder head assembly  14  on the side opposite the intake passages  35 . These exhaust passages terminate in openings that communicate with the turbine phase of the supercharger  26  through a suitable manifold arrangement  49 . From the turbine of the supercharger  26  the exhaust gases exit through a flange  51 , which communicates with a suitable, exhaust system.  
         [0023]    Exhaust valves  52  are provided at the cylinder head recess surface end of the cylinder head exhaust passages  48 . These exhaust valves  52  are operated by an exhaust camshaft  53 , which is driven in a suitable manner along with the intake camshaft  41 . Specifically, the intake and exhaust valves  36  and  52  are operated by respective lobes  54  and  55  (FIG. 2) of the intake and exhaust camshafts  41  and  53 , which act upon thimble tappets  56  and  57 , respectively, supported for reciprocation in the cylinder head assembly  14 . These act against coil compression springs  58  and  59 , respectively, which urge the valves  36  and  52  toward their closed positions within valve guides  61  and  62  formed in the cylinder head that support the stems of the intake and exhaust valves  36  and  52 , respectively.  
         [0024]    The control strategy by which the injectors  43  and  44  are operated will now be described by reference to FIG. 3. As seen in this figure, there is a curve, indicated by the reference character B which delineates the range when only the fuel injector  43  is employed from the range when both injectors  43  and  44  are employed to supply fuel. Within this range, there is a further range, indicated by the curve A under which the engine operates in a stratified charge mode. This area is indicated by the reference character S 1 . Under this condition the injector  43  only injects a small amount of fuel necessary to sustain engine operation. This fuel is injected toward the gap of the spark plug  47  and at a timing to insure that the charge will ignite even though the total charge in the combustion chamber  15  is less that stoichiometric.  
         [0025]    Outside of the curve A and below the curve B in this figure, there are two ranges indicated as S 2  and S 3 . In each of these ranges, the fuel is supplied only by the injector  43  but the engine is operated to provide homogeneous combustion.  
         [0026]    Above the curve B, there is homogenous combustion and the mixture is supplied by the combination of the injectors  43  and  44 . Since both injectors  43  and  44  are supplying fuel, it is possible to inject the necessary amount of fuel over the entire engine speed and low ranges. The disposition of the injector  44  in relation to the induction system flow passage, as previously noted, improves in the obtaining of the homogenous mixture.  
         [0027]    In this portion of the curve, there is a broken line C which shows the torque which would be provided by the engine were it not for the supercharger  26 . The curve D shows the actual output with the supercharger  26  operative so that the increase in torque between these two is indicated by the dimension as indicated.  
         [0028]    Although the invention has been described in conjunction with an engine having a turbocharger, other forms of compressors can be employed including centrifugal or positive displacement type compressors. Also, some features of the invention may also be employed in un-supercharged engines. Of course, various other changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.