Abstract:
A direct injected, internal combustion engine combustion chamber configuration that employs a shrouded arrangement for the intake valve seat so as to generate a tumble motion under at least some running conditions. This is accomplished by a shrouding of the intake valve in such a way that the flow direction effects a tumbling motion and also so that the air flow does not adversely affect the flow from the injector nozzle.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an internal combustion engine and more particularly to an improved induction control system for a direct injected engine. 
     The continued demand for higher performance and more efficient and lower emission internal combustion engines has prompted the widespread use of fuel injection as a method of charge forming. By utilizing fuel injectors, a number of benefits can be gained. Among these include the ability to more accurately control the amount of fuel delivered, particularly on a cycle-by-cycle basis. 
     Most production engines that employ fuel injection, however, employ a system which is referred to as “manifold injection.” With this type of arrangement, the fuel is injected into the intake passage generally in proximity to the intake port that serves the combustion chamber. This system permits the use of lower cost fuel injectors and still obtains many of the benefits of fuel injection. 
     However, it is generally necessary to have a homogeneous fuel air mixture in the combustion chamber. This is done to insure combustion at the appropriate timing. This is particularly true in conjunction with spark ignited engines. As a result of this, there is actually more fuel in the combustion chamber than is necessary to obtain the desired power under most running conditions. Thus, there gives rise to the problem of higher than necessary fuel consumption and also greater than desired exhaust gas emissions. 
     Therefore, there has been a desire to obtain an engine that can run in a so-called “lean burn” mode. This involves fling the cylinder with a less than stoichiometric mixture under all but high speed, high load running conditions. If this can be achieved, then further improvements in fuel economy and exhaust emission control can be obtained. 
     One way of obtaining the capability of lean burning is if the charge in the combustion chamber is stratified. Although stratification can be easily obtained utilizing pre-combustion chambers, these chambers give rise to pumping losses and have other disadvantages. Therefore, there is a desire to be able to obtain stratification in an open chamber engine. Direct cylinder fuel injection lends itself to achieving this goal. 
     However, there is still a difficulty in insuring that the appropriate fuel air mixture is present at the spark plug at the time of firing. Also, there is a desire to increase the turbulence in the charge at low speeds and low loads so as to insure good flame propagation. 
     It is, therefore, a principal object of this invention to provide an improved internal combustion engine having direct cylinder injection and wherein lean burning through stratification can be accomplished. 
     It is a further object of this invention to provide an improved arrangement for introducing a fuel air charge into the combustion chamber of an engine that will ensure good burning under all running conditions. 
     In connection with the generation of turbulence in the combustion chamber, this is desirable in order to obtain good flame propagation under low speed low load conditions. Most turbulence generating devices, however, restrict the amount of airflow and hence, the power output of the engine will be reduced. 
     It is a further object of this invention to provide an improved turbulence generating arrangement for the induction system of an engine wherein high speed high load output are not sacrificed. 
     In addition to desiring turbulence in the combustion chamber, another problem that is attendant with direct fuel injection is the difficulty of confining the location of the injected fuel. Obviously, the fuel must be injected at a fairly high pressure so as to insure that adequate will be present to serve all running conditions. This high pressure spray, however, is somewhat difficult to control. 
     It is, therefore, a still further object of this invention to provide an improved induction passage arrangement for a direct injected engine wherein the induction passage assists in controlling the direction of fuel spray and increasing turbulence without significantly reducing the amount of fuel spray. 
     SUMMARY OF THE INVENTION 
     This invention is adapted to be embodied an internal combustion engine that has a cylinder block, cylinder head assembly which define a cylinder bore that is closed at one end by a surface of the cylinder head portion of the cylinder block, cylinder head assembly. A piston reciprocates in the cylinder bore and forms a combustion chamber with the cylinder bore and cylinder head surface. At least one intake passage extends from an inlet opening in an outer surface of the cylinder block, cylinder head assembly and serves the combustion chamber through an intake valve scat formed in the cylinder head surface. A poppet type intake valve is supported in the cylinder head portion of the cylinder block, cylinder head assembly for controlling the opening and closing of the intake valve seat. The intake passage has a general configuration that causes the flow into the combustion chamber to be in a direction generally toward a plane containing the axis of the cylinder bore and downwardly toward the head of the piston. A fuel injector is mounted in the cylinder block cylinder head assembly with a discharge port directed into the combustion chamber so as to spray in a direction generally parallel to the axis of the airflow charge through the intake passage. The fuel injector discharge port is disposed in proximity to a peripheral edge of the intake valve seat. The intake valve seat is formed within the cylinder head surface and is bounded by a masking peripheral edge of the cylinder head surface which partially shrouds the discharge flow of air past the intake valve through the intake port toward the fuel injector on the side closest to the cylinder bore. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial cross-sectional view taken through a portion of a single cylinder of an internal combustion engine constructed in accordance with a first embodiment of the invention and showing only the upper portion of the engine. 
     FIG. 2 is a bottom plan view showing the underside of the cylinder head assembly, with the valves removed and is taken generally in the direction of the line  2 — 2  in FIG.  1 . 
     FIG. 3 is an enlarged cross-sectional view taken along the same plane as FIG. 1 but primarily showing the construction associated with one of the intake valves and its seat to show the masking effect. 
     FIG. 4 is a graphical view that depicts the power output of the engine under certain different running control conditions. 
     FIG. 5 is a graphical view showing from top to bottom the timing of the opening of the exhaust valve, the intake valve and the firing of the spark plug, and in the lower portion the varying conditions of the fuel injection under the varying types of engine control conditions. 
     FIG. 6 is a graphical view showing the tumble ratio in relation to valve lift in connection with the embodiment of the invention illustrated in solid lines and in the prior art or conventional type structure in the phantom lines. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now in detail to the drawings and initially to FIGS. 1-3, a portion of 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  includes a cylinder block, cylinder head assembly, indicated generally by the reference numeral  12 . This is comprised of a cylinder block  13  and a cylinder head assembly  14  that is detachably connected to the cylinder block  13  by means of threaded fasteners  15  (FIG.  2 ). 
     Since the invention deals primarily with the induction system for the engine  11  and the charge forming system  40 , the lower part of the engine is not shown. Where any engine component is not illustrated or described, it may be assumed that any conventional construction may be utilized for such components. 
     In the illustrated embodiment, the cylinder block  13  is provided with a cylinder liner  16  that is cast, pressed, or otherwise positioned within the main body of the cylinder block  13 . This permits the use of a light alloy material such as aluminum or aluminum alloy for the main cylinder block  13  with the cylinder bore, indicated at  17 , to be formed from a harder more wear resistant material. 
     The cylinder bore  17  has an axis indicated at A and is closed at its upper end by the cylinder head  14 . The cylinder head  14  is formed with a lower surface  18  that closes the cylinder bore at this end. It should be noted that, although the invention is described in conjunction with an engine having a detachable cylinder head and wherein the cylinder bore is formed by a liner in the cylinder block, it may be utilized with other types of arrangements, for example, those having integral cylinder heads and cylinder blocks. 
     A piston  19  is supported for reciprocation within the cylinder bore  17  along its axis A. The head of the piston  19  is formed with a bowl  21  which assists in the stratification process of the fuel, as will become apparent. 
     A piston pin  22  connects the piston  19  to the upper or small end of a connecting rod  23 . The lower end of the connecting rod  23 , (which does not appear in the drawings) is rotatably journaled in a known manner on a crankshaft which is not illustrated, for the reasons already noted. 
     The area in the cylinder bore  17  above the head of the piston  19 , the head of the piston  19  and the cylinder head recessed surface  18  form a combustion chamber, indicated generally by the reference numeral  24 . An intake charge is delivered to this combustion chamber  24  by an intake passage arrangement, indicated generally by the reference numeral  25 . 
     The intake passage arrangement  25  is comprised of an inlet opening  26  that is formed in an outer surface  27  of the cylinder head  14 . A suitable induction system which is not shown but may include an air inlet device, a flow controlling throttle valve and silencing and filtering arrangements provides an atmospheric air source to the inlet opening  26  of the inlet passage arrangement  25 . 
     The inlet opening  26  serves a common runner portion  28  that extends generally downwardly and inwardly toward a plane containing the axis of the cylinder bore axis A. This common passage  28  is divided by a dividing wall  29  into a pair of passage portions  31  each of which terminates at a respective intake valve seat  32 . 
     The heads  33  of a respective poppet-type intake valves  34  cooperates with the valve seats  32  for controlling the flow through the intake passage arrangement  25  into the combustion chamber  24 . Each intake valve  34  has a stem portion  35  that is slidably supported within a guide  36  provided in the cylinder head  14 . 
     A coil compression spring  37  cooperates with a keeper retainer assembly for urging the intake valves  34  to their closed positions. Bucket-type tappets  38  are supported within bores  39  formed in the cylinder head  14 . These bucket-type tappets  38  are operated by the lobes of an intake camshaft  41 . The intake camshaft  41  is rotatably journaled within a cam chamber  42  formed at the upper end of the cylinder head assembly  14 . A suitable timing drive drives the camshaft  41  at one-half crankshaft speed, as is well known in the art. 
     As may be best seen from FIG. 2, the intake valve seats  32  lie substantially on one side of a plane that contains the axis of the cylinder bore  17 . On the opposite side of this plane, there are provided a pair of exhaust valve seats  43 . These exhaust valve seats  43  are formed at the inlet end of an exhaust passage arrangement  44 . The exhaust passage arrangement  44  includes a pair of branch sections  45  that extend from the exhaust valve seats  43  upwardly and then turn where they merge into a common section  46 . 
     A wall  47  divides the inlet portions  45  downstream of the common portion  46 . The common portion  46  opens through an outer face  47  of the cylinder head  14  through an exhaust discharge opening  48 . A suitable exhaust system (not shown) may be affixed to the cylinder head surface  47  so as to collect the exhaust gases and discharge them to the atmosphere. 
     The heads  49  of poppet type exhaust valves  51  control the flow through the exhaust valve scats  43 . The poppet type exhaust valves  51  have stem portions  52  that are slidably supported in guides  53  fixed in the cylinder head  14 . Coil compression springs  54  act against keeper retainer assemblies fixed to the ends of the valve stems  52  for holding the exhaust valve  51  in their closed positions. 
     Bucket-type tappets  55  are slidably supported in bores  56  formed in the cylinder head  14 . The lobes of an exhaust camshaft  57  cooperate with the bucket tappets  55  for opening the exhaust valves  51  in a known manner. 
     Like the intake camshaft  41 , the exhaust camshaft  57  is driven by a suitable timing drive at one-half crankshaft speed. This exhaust camshaft  57  is also contained within the cam chamber  42 . This cam chamber  42  is closed by a cam cover  58  that is fixed to the cylinder head  14  in a known manner. 
     As seen only in FIG. 2, a spark plug, indicated generally by the reference numeral  59  is mounted in a tapped hole  61  in the cylinder head  14 . This spark plug  59  has its terminal  62  disposed substantially on the axis A of the cylinder bore  17 . Thus, good flame propagation will be insured. 
     A fuel injector, indicated generally by the reference numeral  63  is mounted on the intake side of the cylinder head  14  in an injector receiving recess  64  formed beneath the intake passage arrangement  21 . As may be best seen in FIG. 13, the fuel injector  63  has a nozzle portion  65  that defines a spray opening  66  that has a spray axis  67 . This spray axis  67  extends generally parallel to the flow direction through the main portion of the intake passage arrangement  25  and is slightly offset from it. 
     As may be best seen in FIG. 2, the cylinder head surface  18  is provided with a recessed opening  68  through which the tip portion of the injector nozzle  65  extends so as to not obstruct the flow from the injector  63 . The exposed portion of the injector  63  has a fuel delivery tip  69  that cooperates with a fuel rail (not shown) so as to deliver fuel to the injector body through a fuel inlet  71 . 
     The injector  63  may be of any known type and generally has a solenoid winding that operates an injector valve so as to open and close the nozzle port  66  so that fuel will be sprayed into the combustion chamber in a direction indicated generally by the arrow  72  as seen in FIGS. 1 and 3. The fuel supply system for supplying fuel to the injector  63  may be of any known type and thus, has not been illustrated. Also the injection timing strategy will be described in more detail later by reference to FIG.  5 . 
     As has been noted, if stratification is to be obtained, it is important to ensure that the patch of fuel that is at a stoichiometric ratio will be in the vicinity of the gap  62  of the spark plug  59  at the time of firing. This is particularly important when operating with a very lean overall mixture under low speed/low load and lower mid-range conditions. However, it is also important to ensure that there is turbulence in the combustion chamber so that once the flame is initiated, it will rapidly propagate across the flame front. 
     The direction of airflow is also important in addition to obtaining the turbulence in ensuring that the fuel patch is at the appropriate location. In accordance with an important feature of the invention, the intake passage arrangement and particularly the area around the intake valve seats  32  is configured so as to achieve this result. 
     As may be best seen in FIGS. 1 and 3, the intake air flowing through the intake passage arrangement  25  follows in a direction indicated by the arrow  73  through the common portion  29  and then branches toward the individual sections  29  and their valve seats  32 . When the intake valve  34  opens, the flow passes around the intake valve head  33  with a first portion, indicated by the arrow  74  flowing generally downwardly toward the cylinder bore axis A and the plane that contains it. This will tend to cause a tumble motion in the combustion chamber indicated again by the reference numeral  74 . That is, the flow goes downwardly toward the head of the piston  19  where it is then deflected across the cylinder bore and back across the plane containing the axis of the cylinder bore A and then in an upward direction. 
     There is, however, another flow path around the other side of the head portion indicated by the arrow  75  which also causes a tumble motion but in an opposite direction. Hence, rather than generating turbulence, these opposing tumble motions will tend to cancel each other out and reduce the tumble effect. This is not desirable. 
     Therefore, in accordance with the invention and as is best seen in FIG. 3, there is provided a shrouded area  76  that extends around the intake valve seat  32  on the side thereof away from the cylinder bore axis A and adjacent the cylinder bore  17 . This provides a somewhat restricted flow path  77  through which the air is channeled when the intake valve  34  is in its initial opening phase as seen in the phantom line in FIG.  3 . The path followed by the valve heads  33  is shown by the phantom lines in this figure. 
     The result of this is that when the intake valves  34  initially begin their lift, there will be a flow restriction caused by the shrouding area  76  on the sides adjacent both the cylinder bore and the fuel injector  63  and hence there will be a greater flow path in the direction of the arrow  74  than in the direction of the arrow  75 . Also, since more air is channeled in this direction, the flow velocity will be higher. Hence, the tumbling motion in the direction of the arrow  74  will be much greater than that of the direction of the arrow  75 . 
     This may be seen best in FIG. 6 wherein there is depicted the tumble ratio in relation to valve lift of the instant invention as shown in solid lines and the prior art type without shrouding as shown in phantom line curve. It will be seen that the tumble ratio actually increases rather abruptly even at low lifts and then stays at a higher rate until the valve is fully opened. At this time, the shrouding effect will bc minimized and also the flow resistance will be reduced so that the system then tapers off and operates more like a conventional system. 
     This has the effect of providing increased tumble flow and assists in confining the fuel patch, indicated by the shaded area  77  in FIGS. 1 and 3 in the area adjacent the piston bowl  21  and on the one side of the combustion chamber. 
     This tumble action can be further augmented by providing a tumble control valve, indicated generally by the reference numeral  78  in the intake passage portion  28 . FIG. 1 shows this tumble valve in its closed position wherein it is maintained under low speed/low load conditions. This causes the direction of the flow to be more toward the enshrouded side of the valve seat  32  and further augments the tumble action already described. 
     As the load and speed of the engine increases, the tumble valve  78  is opened and this tumbling motion is somewhat diminished. In addition, the flow restriction is also substantially diminished. Thus, this relationship ensures that the desired flow motion will be obtained in the combustion chamber so as to aid in stratification. 
     In addition, the shrouding provided by the shroud area  76  will reduce the effect of the air flow from redirecting or dispersing the fuel injection if it is injected early in the cycle. In fact, in accordance with another feature of the invention, the injection strategy is chosen so as to further maximize the stratification and prevent dissipation. 
     FIGS. 4 and 5 explain this situation. In accordance with the invention, the fuel injection timing is controlled so under low speed/low load conditions injection begins toward the end of the compression stroke. This means that the fuel is injected actually after the intake valve is closed as may be seen in FIG. 5 by the control range “C” under lower load conditions. This provides a lesser total engine power output as seen in FIG. 4 in relation to speed but improves significantly the fuel stratification and thus the fuel economy. 
     Since the fuel is injected after the intake flow has stopped, the intake air will not disperse the fuel spray and the fuel patch  77  can be maintained. Because of the tumbling action which has been generated, this patch will then be moved into proximity with the gap  62  of the spark plug at the time of firing and thus even though only a small amount of fuel may be injected, combustion will be assured because there will be definitely a stoichiometric mixture at the spark gap at the time of firing. The piston bowl  21  will also assist in confining the fuel patch. 
     As the power requirements increase, the beginning of injection is advanced while the ending is maintained relatively constant as also seen in FIG.  5 . Thus, added fuel will be introduced but very little fuel if any will be introduced at the time when the intake valve is opened. 
     As the speed and/or load on the engine increases, the control moves to the routine phase “B”. During this phase, a greater amount of fuel is injected and the injection is advanced during the beginning of the intake stroke rather than at the end of the compression stroke. This means that some of the air charge will act on the fuel patch so as to redirect it but nevertheless the fuel patch will still be maintained and it will again pass the spark plug at the time of firing. However, under this condition, the fuel patch may actually have made a revolution in the combustion chamber having passed a spark plug one time and then coming into registry with it again, depending upon the weight of tumble. This provides a power output as shown at B in FIG.  4 . 
     As the speed and load increase, the timing of the injection is both advanced and the ending is retarded so as to provide a longer injection cycle. This is done because now there will be a greater amount of fuel in the combustion chamber and a more homogeneous mixture is desired. However, the late injected fuel will ensure a stoichiometric mixture at the presence of the spark plug at the time of firing. 
     As also seen by the phantom line in FIG. 5 the intake valve timing may be adjusted during engine running. This can increase the ability to induct the air charge. 
     Thus, it should be apparent that the described intake passage arrangement, the shrouding and the use of the tumble valve and specific injection timing pattern all go together to provide an excellent stratification of the charge under conditions when it is desired, the proper decree of turbulence to ensure good flame propagation and unrestricted breathing capabilities to achieve high power output. 
     It will be readily apparent to those skilled in the art that the foregoing description is that of the preferred embodiment of the invention. Various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.