Abstract:
An engine in which the cylinders are scavenged according to a cross scavenging technique. The engine includes one or more cylinders in each of which a piston is disposed for reciprocal motion. The engine further includes a direct fuel injection system that allows controlled input of fuel into each cylinder to promote more efficient operation of the cross scavenged engine.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to an internal combustion engine, and particularly to an internal combustion engine that utilizes fuel injection and cross scavenging. 
     BACKGROUND OF THE INVENTION 
     Internal combustion engines generally have one or more cylinders through which one or more pistons move in a reciprocating manner. Each piston is connected to a crankshaft by a connecting rod able to deliver force from the piston to the crankshaft to rotate the crankshaft. Power to drive the piston is provided by igniting a fuel-air mixture disposed in the cylinder on a side of the piston opposite the connecting rod. The fuel-air mixture is ignited by some type of ignition device, such as a spark plug. 
     Some internal combustion engines, such as cylinder ported, two-stroke engines, utilize a scavenging process to promote mixing of the air and fuel. One type of scavenging process is referred to as loop scavenging. A loop scavenged engine includes two or more scavenge ports in each cylinder that are directed toward the side of the cylinder away from the exhaust port. Generally, the inflow of air or air-fuel mixture is across a piston having an essentially flat top. 
     Another type of scavenging is referred to as cross scavenging. A cross scavenged engine or cylinder utilizes a deflector to deflect the mixture of air and fuel intaken through the scavenge or intake ports of each cylinder. Often, the deflector is formed on the crown of the piston in the form of a wall or barrier. This type of design utilizes scavenge ports and exhaust ports that are disposed on directly opposite sides of the cylinder, permitting the direct drilling of the scavenge and exhaust ports. This allows for a less expensive manufacturing process and permits closer cylinder-to-cylinder spacing. Additionally, at least some cross scavenged engines have relatively good fuel efficiencies and low emissions at low speed and/or part throttle. 
     It would be advantageous to gain the benefits of a cross scavenged engine design with improved control over combustion to promote starting, fuel economy and power of the engine throughout the range of engine speeds. 
     SUMMARY OF THE INVENTION 
     The present invention features a cross scavenged engine that can be used to power, for example, a watercraft. In one embodiment, the engine is utilized with an outboard motor which can be used to move a vehicle along a body of water. The performance of the engine is improved by utilizing a fuel injection system for injecting a fuel into the one or more cylinders of the engine. The injection of fuel improves the operating characteristics of a cross scavenged by cooling the piston during vaporization of the injected fuel. This vaporization, in turn, allows for a better burn or combustion in the one or more cylinders. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
     FIG. 1 is a perspective view of a watercraft powered by an exemplary engine, according to a preferred embodiment of the present invention; 
     FIG. 2 is a schematic cross-sectional view of a single cylinder in an exemplary two-stroke engine that may be utilized with the watercraft illustrated in FIG. 1; 
     FIG. 3 is an enlarged view of the combustion chamber of the engine illustrated in FIG. 2; 
     FIG. 4 is a schematic representation of an exemplary fuel delivery system utilizing a fuel-only direct injection system; 
     FIG. 5 is a schematic representation of an alternate fuel delivery system for direct injection of fuel and air; and 
     FIG. 6 is a schematic representation of an alternate fuel delivery system utilizing a fuel rail. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present technique for better utilizing a cross scavenged engine can be used in a variety of engines and environments. For the sake of clarity and explanation, however, the invention is described in conjunction with an engine that operates on a two-stroke cycle and powers a watercraft. The exemplary embodiment described herein should not be construed as limiting, however, and has potential uses in other types of engines and applications. 
     Referring generally to FIG. 1, an exemplary application of the present system and methodology is illustrated. In this application, a watercraft  20 , such as an inflatable boat, is powered by an engine  22  disposed in an outboard motor  24 . In this embodiment, outboard motor  24  is mounted to a transom  26  of watercraft  20 . Engine  22  is a two-stroke engine that is cross scavenged and utilizes a fuel injection system, as explained more fully below. 
     Referring generally to FIGS. 2 and 3, a single cylinder of an exemplary two-stroke engine  22  is illustrated. In this embodiment, engine  22  includes at least one cylinder  30  having an internal cylinder bore  32  through which a piston  34  reciprocates. Piston  34  typically includes one or more rings  36  that promote a better seal between the piston  34  and cylinder bore  32  as piston  34  reciprocates within cylinder  30 . 
     Piston  34  is coupled to a connecting rod  38  by a pin  40 , sometimes referred to as a wrist pin. Opposite pin  40 , connecting rod  38  is connected to a crankshaft  42  at a location  43  offset from a crankshaft central axis  44 . Crankshaft  42  rotates about axis  44  in a crankshaft chamber  46  defined by a housing  48 . 
     At an end of cylinder  30  opposite crankshaft housing  48 , a cylinder head  50  is mounted to cylinder  30  to define a combustion chamber  52 . Cylinder head  50  may be used to mount a fuel injection system  54  able to supply fuel to combustion chamber  52 . In one preferred embodiment, fuel injection system  54  is a direct injection system having an injector or injector pump  55  mounted to cylinder head  50 , generally above combustion chamber  52 , to spray a fuel directly into the combustion chamber. 
     Cylinder head  50  also may be used to mount a spark plug  56  to ignite an air-fuel mixture in combustion chamber  52 . Injector pump  55  and spark plug  56  are received in openings  58  and  60 , respectively. Openings  58  and  60  may be formed through the wall that forms either cylinder head  50  or cylinder  30 . In the illustrated embodiment, openings  58  and  60  both are formed through the wall of cylinder head  50  for communication with combustion chamber  52  within a recessed internal region  62  of cylinder head  50 . Cylinder head  50  also may include a notch  65  that enhances mixing of the fuel and air. 
     By way of example, injector pump  55  may be generally centrally located at the top of cylinder head  50 , as illustrated best in FIG.  3 . In this exemplary embodiment, injector  55  is oriented at an angle with respect to the longitudinal axis  63  of cylinder  30 . As illustrated, spark plug  56  also may be disposed at an angle such that its electrodes  64  are positioned in a fuel spray pattern  66  during injection of fuel into recessed region  62  of combustion chamber  52 . Fuel spray pattern  66  is the “cone” or other pattern of fuel spray injected by injector pump  55 . 
     A deflector pin  68  may be positioned such that it extends partially into fuel spray pattern  66  intermediate an injection nozzle  70  of injector pump  55  and electrodes  64  of spark plug  56 . Deflector pin  68  reduces or eliminates the amount of fuel sprayed directly onto electrode  64 . This, in turn, reduces the chance of fouling spark plug  56 . Additionally, a combustion sensor  72 , such as an oxygen sensor, may be positioned in communication with combustion chamber  52  within recessed region  62 . 
     In a cross scavenged engine, cylinder  30  includes one or more intake or scavenge ports  74  and one or more exhaust ports  76 . Generally, the scavenge port  74  and exhaust port  76  are disposed on generally opposite sides of cylinder  30  at a common axial or longitudinal distance along cylinder  30 . The arrangement of ports makes it possible to drill, the scavenge and exhaust ports directly in a single operation performed from the exhaust port side. This greatly reduces the manufacturing costs of the cross scavenged engine as compared to an equivalent loop scavenged engine. The cross scavenged cylinder also includes a deflector  78  designed to deflect air incoming through scavenge port or ports  74  for promoting mixing of air and fuel in combustion chamber  52 . In the illustrated embodiment, deflector  78  is disposed on a crown  80  of piston  34 . An exemplary deflector  78  includes a front deflector face or wall  82 , a top region  84  and a declined region  86  generally disposed towards the exhaust port side of piston  34 . Cylinder head notch  65  preferably is positioned such that it is proximate the transition between front deflector wall  82  and top region  84  when piston  34  is at top dead center. 
     In operation, piston  34  travels towards cylinder head  50  to compress a charge of air within combustion chamber  52 . Simultaneously, injector pump  55  injects fuel to create a fuel air mixture that is ignited by an appropriately timed spark across electrode  64 . As piston  34  travels towards cylinder head  50 , air is drawn through an inlet port  88  into crankshaft chamber  46  and cylinder  30  on a side of piston  34  opposite combustion chamber  52 . A valve  90 , such as a reed valve, allows the air to pass into engine  22  but prevents escape back through inlet port  88 . 
     Upon ignition of the fuel-air charge in combustion chamber  52 , piston  34  is driven away from cylinder head  50  past exhaust port  76  through which the exhaust gasses are discharged. As piston  34  moves past exhaust port  76 , scavenge port  74  is fully opened. Air from crankshaft chamber  46  is forced along a transfer passage  92  and through scavenge port  74  into cylinder  30  on the combustion chamber side of piston  34 . The incoming air is deflected upwardly by deflector  78  to facilitate removal of exhaust gasses through exhaust port  76  while providing a fresh charge of air for mixing with the injected fuel. Effectively, the downward travel of piston  34  compresses the air in crankshaft chamber  46  and forces this fresh charge of air into cylinder  30  for mixing with the next charge of fuel and ignition by spark plug  56 . 
     Preferably, the angle of injector pump  55  is selected to direct fuel spray pattern  66  generally towards the internal wall of cylinder  30  proximate scavenge port  74 . This aids in the mixing of fuel and air as the incoming air, deflected upwardly by deflector  78 , meets the charge of fuel injected through injection nozzle  70 . In an exemplary embodiment, if the injector nozzle  70  is disposed near longitudinal axis  63  and the bore/stroke ratio is approximately 1, the angle between injector pump  55  and longitudinal axis  63  is preferably in the range from 5 to 25 degrees. Regardless of the angle, it is preferred that injector pump  55  be positioned and/or angled such that a majority of the fuel spray is directed into the hemisphere or side of cylinder  30  having scavenge port  74 . 
     The actual amount of fuel injected and the timing of the injection can vary greatly depending on a variety of factors, including engine size, engine design, operating conditions, engine speed, etc. However, the utilization of fuel injection system  54  and the precise control over injector  55  allows the amount of fuel injected and the timing of the ignition to be carefully controlled. Also, the heat otherwise retained in piston  34  and deflector  78  is removed as fuel is sprayed onto the piston and vaporized. These factors permit increases in efficiency, fuel economy and power that would otherwise not be achievable with cross scavenged engines. The factors also permit a variety of fuels to be utilized in engine  22 . 
     Referring generally to FIGS. 4 through 6, exemplary fuel injection systems  54  are illustrated. In FIG. 4, fuel injection system  54  comprises a direct fuel injection system in which only liquid fuel is directly injected into cylinder  30  of engine  22 . Fuel is supplied to injector  55  via a fuel reservoir  110 , e.g., a low pressure fuel supply such as a fuel tank, and fuel supply lines  112 . In this embodiment, fuel injector  55  may be of a variety of injector types, including electrically, hydraulically or mechanically actuated injectors. In this type of system, a pressure pulse created in the liquid fuel forces a fuel spray to be formed at the mouth or outlet of nozzle  70  for direct, in-cylinder injection. The operation of injector  55  is controlled by an electronic control unit (ECU)  114 . The ECU  114  typically includes a programmed microprocessor or other digital processing circuitry, a memory device such as an EEPROM for storing a routine employed in providing command signals from the microprocessor, and a drive circuit for processing commands or signals from the microprocessor, as known to those of ordinary skill in the art. 
     An alternate embodiment of fuel injection system  54 , labeled  54 ′ is illustrated in FIG.  5 . In this embodiment, both fuel and air are directly injected into cylinder  30  of engine  22  by injector  55 . Fuel is supplied via a fuel reservoir  116 , e.g., a low pressure fuel supply such as a fuel tank, and fuel supply lines  118 . Additionally, high pressure air is supplied to injector  55  via an air supply  120  and air supply line  122 . Again, the activation of injector  55  is controlled by an ECU  124 . In this type of system, both the air and the fuel for combustion are provided by injector  55 . 
     Another embodiment of fuel injection system  54 , labeled  54 ″, is illustrated in FIG.  6 . In this embodiment, a fuel rail  126  is utilized to supply fuel to one or more cylinders  30  of engine  22 . Fuel rail  126  supply high pressure fuel to injectors  55 , which are actuated between an open and a closed position to selectively permit the injection of high pressure fuel into one or more cylinders  30 , as known to those of ordinary skill in the art. 
     In the embodiment illustrated, a low pressure fuel supply  128  provides fuel to a high pressure fuel supply  130  via appropriate fuel lines  132 . High pressure fuel supply  130 , in turn, supplies fuel under injection pressure to fuel rail  126  via supply lines  134 . 
     It will be understood that the foregoing description is of preferred exemplary embodiments of this invention, and that the invention is not limited to the specific form shown. For example, the fuel injection systems described are exemplary embodiments, but a variety of injection systems can be utilized with the exemplary cross scavenged engine. Additionally, a variety of engine configurations, displacements, cylinder numbers, piston designs, scavenge port designs and exhaust port designs can be utilized. These and other modifications may be made in the design and arrangement of the elements without departing from the scope of the invention as expressed in the appended claims.