Abstract:
An improved combustion chamber configuration for a direct injected internal combustion engine. The cylinder head recess and piston head are configured so as to provide a small clearance volume and accordingly high compression ratios while the shape of the piston head and the arrangement of the cylinder head recess permits a portion of the injected fuel to be directed toward the exhaust valves to cool them and reduce smoke and increase fuel efficiency.

Description:
BACKGROUND OF INVENTION 
     This invention relates to an internal combustion engine and particularly one of the type having direct cylinder injection and more particularly to a combustion chamber for such an engine. 
     In the interest of improving engine performance in the field of power, fuel consumption and exhaust emission control, it has been proposed to employ direct cylinder injection. By injecting fuel directly into the combustion chamber, it is not necessary to achieve a homogeneous mixture in the combustion chamber under all running conditions so as to insure combustion. In other words, if direct cylinder injection is possible, stratification can be obtained. 
     One problem in connection with obtaining a stratified charge and good combustion under low speeds and low loads is the difficulty in insuring that a stoichiometric mixture is present at the spark plug at the time of ignition. Various combustion chamber arrangements have been proposed with an effort to achieve this. Many of theses combustion chamber designs employ a bowl that is formed in the head of the piston and which is configured so as to enable stratification at least under some running conditions. 
     For example, FIG. 1 is a prior art cross sectional view taken through the cylinder of one type of engine that has been proposed to achieve this goal. This is a combustion chamber of the type that is disclosed in Japanese Published Application Hei 6-81651, published Mar. 22, 1994In this engine, there is a combustion chamber S which is formed by a cylinder bore  11  of a cylinder block  12 , a lower surface  13  of a cylinder head  14  which, in that construction, is detachably connected to the cylinder bloc k  12  and a piston  15  that reciprocates in the cylinder bore  14 . In this combustion chamber S, the piston has its head portion formed with a pair of angularly inclined upper surfaces  16  and  17  which face diametrically opposed portions of the cylinder head lower surface  13  and in which respective intake  18  and exhaust passages  19  are formed. Intake and exhaust valves  21  and  22  cooperate with the valve seats formed at the ports of these intake and exhaust passages  18  and  19  to control the flow of air into the combustion chamber and exhaust gases out of the combustion chamber. 
     The piston head inclined portion  16  is formed with a bowl like recess  23 , which is formed primarily on the intake side of the piston head but extends slightly over toward the exhaust side. 
     A spark plug  24  is mounted in the cylinder head  14  generally on the center of the combustion chamber S and the axis of the cylinder bore  11 . 
     A fuel injector  25  is mounted on the intake side of the cylinder head  14  and sprays its fuel in a pattern as shown in this figure so as to impinge upon the cylinder head recess  23 . The intake port or ports  18  are configured so as to cooperate with the bowl  23  to generate a tumble action as shown by the arrow “a” in this figure. The theory is that this will cause the fuel deposited in the piston head bowl  23  to be swept toward the spark plug  24  to insure stratification under low speed and low load conditions. 
     There are several disadvantages with this type of combustion chamber. Because of the fact that the fuel is injected on the surface of the piston head bowl  23  it tends to become excessively rich and results in lack of complete fuel evaporation into the combustion chamber S. This is because more fuel is deposited than can effectively vaporize and is liable to cause smoke generation and unwanted exhaust gas emissions. 
     Another solution to the problem of combustion chamber configuration and for direct injected engines is shown in Japanese Published Application Hei 11-324680, and its issued United States Letters Patent counterpart 6,062,195, issued May 16, 2000. This type of arrangement is shown in FIG.  2  and again has a combustion chamber S that is formed by a piston  31  that reciprocates in a cylinder bore  32  of a cylinder block  33 . This cooperates with a combustion chamber recess formed in a cylinder head  34  that is affixed to the cylinder block  33  in a suitable manner. 
     Intake passages  35  open into the combustion chamber S and are valved by intake valves  36  positioned on one side of the cylinder head. On the other side of the cylinder head, exhaust passages  37  are formed which are valved by exhaust valves  38 . 
     A fuel injector  39  is mounted between the intake valves  36  and below them and injects fuel into the combustion chamber S which is formed by the head of the piston  31 , which has a slight concave configuration  41  although it is substantially flat. The fuel injector  39  sprays its fuel across this slightly concave surface  41  and propagates towards the exhaust valve  38  so as to be heated and improve fuel vaporization. 
     In this arrangement, there is a fairly large angle α between the stems of the intake and exhaust valves  36  and  38  so that the exhaust valve will be inclined to receive the fuel and also so as to preclude the fuel from passing out of the exhaust valve. Thus, this configuration causes a fairly large volume for the combustion chamber S at top dead center and makes it difficult to raise the compression ratio. 
     It is, therefore, a principal object to this invention to provide an improved combustion chamber configuration for a direct injected internal combustion engine. 
     It is a further object to this invention to provide an improved combustion chamber configuration permits the attainment of high compression ratios and avoids the likelihood of fuel condensing in the combustion chamber recess of the piston and not being able to evaporate fully before the spark plug is fired. Thus, the likelihood of smoke in the exhaust and unwanted hydrocarbons can be substantially reduced. 
     SUMMARY OF INVENTION 
     This invention is adapted to be embodied in an internal combustion chamber. The combustion chamber is defined by a cylinder bore closed at one end by a cylinder head combustion chamber surface and at the other end by a piston reciprocating in the cylinder bore. The cylinder head combustion chamber surface has a pair of angular related surface portions formed on diametrically opposed sides thereof. At least one intake port is formed in one of the cylinder head combustion chamber angularly related surface portions. At least one exhaust port is formed in the other of the cylinder head combustion chamber angularly related surface portions. The piston has a head portion with an upper combustion chamber surface. The piston head portion includes an inclined surface facing the one of the cylinder head combustion chamber surface portions and which is inclined toward the other of the cylinder head combustion chamber angularly related surface portions. A fuel injector is mounted in the engine on the side of the combustion chamber formed by the one of the cylinder head combustion chamber angularly related surface portions and sprays toward the piston head portion inclined surface such that at least a part of the fuel injected therefrom will be directed toward the exhaust port. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a cross sectional view taken through the combustion chamber of one cylinder of an engine constructed in accordance with a first form of prior art construction. 
     FIG.2 is a cross sectional view, in part similar to FIG. 1, and shows another prior art combustion chamber configuration. 
     FIG. 3 is a more detailed cross sectional view, in part similar to FIGS. 1 and 2, but showing the construction associated with one cylinder of the instant invention. 
     FIG. 4 is a top plan view of the piston head. 
     FIG. 5 is a cross sectional view taken along the line  5 — 5  of FIG.  4 . 
    
    
     DETAILED DESCRIPTION 
     Referring now in detail to the drawings and particularly FIGS. 3 through 5, but initially primarily to FIG. 3, an internal combustion engine constructed in accordance with an embodiment of the invention is identified generally by the reference numeral  51 . The entire engine  51  is not depicted because the invention deals, as afore described, with the combustion chamber thereof, indicated by the reference character S. Also, only a single cylinder of the engine is depicted because it is believed readily apparent to those skilled in the art how the invention can be practiced with engines having any desired number of cylinders and any cylinder configuration such as in line, V-type or opposed. 
     The engine  51  has a cylinder block  52 , only the upper end of which is shown. This cylinder block  52  defines a cylinder bore  53  in which a piston  54  is supported for reciprocation. The axis of the cylinder bore is indicated as “C.B”. The piston  54  has a skirt portion  55  that faces the cylinder bore  53  and which terminates at its upper end in a head portion  56 . The head portion  56  has a plurality of ring grooves  56  and  57  in which piston rings  58  and  59  are received for providing compression and oil sealing purposes. 
     The piston  54  further has a pair of bosses  61  on the inner portion thereof that have piston pin receiving openings  62  to receive a piston pin for connection to the small end of a connecting rod, the big end of which is journalled on the crankshaft. None of these latter elements are illustrated in the figure for the reasons aforenoted. 
     The cylinder block  52  is also formed with a cooling jacket  63  which surrounds its cylinder bores  53  and through which coolant is circulated in a suitable manner. 
     Affixed to the cylinder block  52  in a suitable manner, which may include integral formation, is a cylinder head member  64 . The cylinder member  64  has a first surface  65  which is in sealing engagement with the cylinder block  52  around its cylinder bores  53 . A recessed surface area is formed therein over the piston  54  having a configuration, which will be described shortly for completing the formation of the combustion chamber S. 
     On one side of a diametrical plane passing through the axis C.B. of the cylinder bore  53  there are formed a pair of intake passages  66  which terminate at intake ports  67  that lie in a first angularly inclined surface of the combustion chamber recess formed therein. Intake valves  68  cooperate with valve seats formed at the intake ports  67  so as to control the admission of an intake air charge into the combustion chamber S. These intake valves  68  have their stem portions slidably supported in valve guides  69  formed in the cylinder head  64 . These intake valves  68  are opened by any suitable form of valve actuating mechanisms and are closed by suitable return springs, the construction of which valve operation may be of any suitable type. 
     On the opposite side of the aforementioned diametrical plane, there are formed a pair of exhaust passages  71  which terminate in exhaust ports  72 . These exhaust ports  72  lie in a second inclined surface of the cylinder head combustion chamber surfaces and these two cylinder head inclined surfaces generally merge along the diametrical plane that contains the cylinder bore axis C.B. 
     The flow through the valve seats formed at the exhaust ports is controlled by exhaust valves  73  which, like the intake valves, are slidably supported in valve guides  74  fixed in the cylinder head  64 . As with the intake valve  68 , the exhaust valve  73  may be operated any suitable type of operating mechanism. 
     The angle between the reciprocal axes of the intake valves  68  and the exhaust valves  73  may be kept fairly shallow so that the compression ratio can be maintained high. Also, this permits the formation of a more compact cylinder head assembly and leaves a greater amount of room for a fuel injector  75  that is mounted in an injector pocket  76  formed on the intake side of the cylinder head  64 . Fuel is supplied to the fuel injector  75  through a fuel rail  77  in a well known manner. 
     Spark plugs  78  are mounted in the cylinder head  64  generally on the cylinder bore axis C.B. which is substantially the center of the combustion chamber S. 
     A cooling jacket arrangement indicated by the reference numeral  79  is formed in the cylinder head  64  and communicates with the cylinder block cooling jacket  63  in an appropriate manner for cooling the cylinder head  64 . 
     The fuel injector  75  has its spray axis directly downwardly toward the piston head  56  in a manner, which will now be described in more detail by particular reference to FIGS. 4 and 5 in addition to FIG.  3 . As seen in these figures, the piston head  56  is formed by a pair of angularly related portions  81  and  82  formed on the intake and exhaust sides thereof, respectively. It will be seen that the inclined portions  81  and  82  do not actually intersect each other, but rather intersect a generally planar surface  83  formed centrally of the piston head  56 . Partially because the diameter of the exhaust ports  72  is smaller than that of the intake ports  67 , the surface  83  is somewhat offset toward the exhaust side so that the inclined surface  81  has a longer range than the exhaust side surface  82 . 
     The surfaces  81  and  82  are disposed to be substantially parallel to the surfaces in which the intake ports  67  and exhaust ports  72  of the cylinder head  64  are formed. Both of these inclined surfaces  81  and  82  are bounded by curved cutouts  84  and  85  to clear the intake and exhaust valves  68  and  73 , respectively. the curved portions  84  on the intake side are joined by a tangential wall  86 . 
     On the other hand, on the exhaust side the curved portions  84  extend inwardly toward the flat surface  83  so as to assist in increasing the compression ratio. No such corresponding portion is formed on the intake side as seen by the shaded area in FIG.  4 . 
     This leaves a squish area  87  on the exhaust side periphery and a somewhat smaller squish area  88  on the intake side periphery of the piston head  56 . 
     The central part of the flattened area  83  at the top of the piston head is formed with a recess  89  so as to provide clearance for the spark plug  78  and specifically the gap thereof at top dead center. 
     On the intake side and specifically in the area below the tip of the fuel injector  75  the squish area  88  is provided with a clearance groove  91  of somewhat short radial extent that intersects a further fan-shape relieved area  92  so as to permit the fuel sprayed from the injector  75  to impact on the piston head surface portion  81  and spread while confining it from impinging on the outer periphery of the piston head  56 . The angle ⊖ of this fan-shaped area  92  is preferably in the range of 120° but this angle will depend upon the injection spray pattern of the injector nozzle. 
     As may be best seen in FIG. 3, the fuel is sprayed from the injector  75  and flows downwardly toward the piston inclined surface  81 . This surface  81  will direct the sprayed fuel in the manner shown in the shaded patch in FIG. 3 toward the head of the exhaust valves  74  so as to improve vaporization. This prevents the generation of smoke. 
     FIG. 1 shows the condition at top dead center when running at an engine speed of 7200 rpm. Fuel is injected from the end of the exhaust stroke to the later half of the intake stroke at crank angles ranging from 380° before top dead center to 250° before top dead center at this engine speed. In addition to improving the fuel vaporization, the fuel impingement on the exhaust valves  73  aids in their cooling and also the intake side of the piston head  56  is cooled by this fuel impingement so as to increase the knocking limit. 
     Thus, from the foregoing description it should be readily apparent that the described embodiment of the invention permits the use of high compression ratios with direct injected engines and also avoids the likelihood of smoke generation as well as improving temperature control within the combustion chamber. 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.