Direct cylinder fuel injection

An internal combustion engine having at least one and preferably two cylinders each with a reciprocating piston, and a compressor which has a reciprocating piston driven by the engine to compress a rich fuel and air mixture within the compressor to inject the mixture directly into the combustion chamber of each engine cylinder. The mixture is ignited by a spark plug to drive the pistons of the engine through their power strokes and rotate an associated crankshaft which is connected to a compressor crankshaft to reciprocate the piston within the compressor and thereby compress and then inject the fuel and air mixture into the engine cylinder. A carburetor preferably supplies an enriched fuel and air mixture to the compressor to reduce the complexity of the system. The fuel and air mixture is preferably substantially atomized through nozzles adjacent each cylinder to improve combustion of the mixture. Preferably the engine is a two-stroke engine with two cylinders and the compressor is driven at twice the speed of the engine.

FIELD OF THE INVENTION
 This invention relates generally to internal combustion engines and more
 particularly to direct cylinder fuel injection for an internal combustion
 engine.
 BACKGROUND OF THE INVENTION
 Internal combustion engines are used in a wide variety of applications to
 power things such as motor boats, power tools, lawn and garden equipment
 and a wide range of vehicles. As concern for the environment increases
 government regulations have been and are being promulgated requiring
 reduced emissions and improved fuel economy from internal combustion
 engines. One method used to lower the emissions and fuel consumption of
 internal combustion engines has been the use of fuel injectors as opposed
 to carburetors to meter and supply fuel to the engine. Electronic fuel
 injectors can be precisely timed to deliver metered quantities of fuel to
 the engine at the appropriate times to reduce emissions and fuel
 consumption and have therefore been widely used. However, electronic and
 computer monitored fuel injectors add considerable cost and complexity to
 the system and are impractical for many small engine systems which do not
 have a battery or generator to power and control the electronic fuel
 injection systems.
 Another approach to lowering the fuel consumption and emission rates of
 internal combustion engines is to directly inject the fuel into an engine
 cylinder as opposed to an intake manifold of the engine which permits
 better timing of the injection to reduce fuel losses in the exhaust
 scavenge gases thereby reducing hydrocarbon exhaust emissions and
 decreasing the fuel consumption of the engine. In some present systems, a
 fuel injector delivers fuel, usually at a relatively low pressure, to a
 compression chamber wherein the fuel is mixed with air creating a
 combustionable mixture which is injected directly into the cylinder of the
 engine. While these systems have been effective at reducing fuel
 consumption and emissions from the engine they are relatively expensive
 due to the fuel injector and the overall complexity of the systems and
 also increase the size of the engine as the compression chamber is located
 on top of the cylinder head with one fuel injector mounted adjacent to the
 compression chamber of each cylinder. This is undesirable for small
 engines such as those in lawn and garden equipment, boat motors and small
 motorcycle engines and the like where a compact engine is required.
 Further, as discussed above fuel injectors add complexity and greatly
 increase the cost of the engine system.
 SUMMARY OF THE INVENTION
 For an internal combustion engine having at least one cylinder each with a
 combustion chamber defined between a cylinder head and a reciprocating
 piston, a valve selectively communicates a compressor, which has a
 reciprocating piston driven by a power transmission member, with the
 engine cylinder to compress a fuel and air mixture within the compressor
 and inject the mixture directly into the combustion chamber of each
 cylinder. The mixture is ignited by a spark plug to drive the piston of
 the engine through its power stroke and rotate the associated crankshaft
 which is linked through the power transmission member to a crankshaft
 operably associated with the piston of the compressor to rotate its
 crankshaft and reciprocate the piston within the compressor and thereby
 compress and then inject the fuel and air mixture into the engine
 cylinder.
 The valve preferably has a passage therethrough which selectively
 communicates the compressor with each engine cylinder to inject a precise
 portion of the mixture into each engine cylinder. For an engine with a
 single cylinder, the compressor is preferably driven by the transmission
 member at a 1:1 ratio relative to the main cylinder such that the
 compressor causes a portion of the mixture to be injected into the main
 cylinder during substantially the same portion of each cycle of the piston
 of the main cylinder. Preferably, the injection into the main cylinder is
 timed so that the fuel mixture loses in the exhaust scavenge gases are
 minimized to reduce hydrocarbon exhaust emission and also to reduce fuel
 consumption of the engine.
 For an engine with a pair of cylinders, the valve preferably selectively
 communicates the compressor individually with each of the engine cylinders
 to inject a precise amount of the fuel and air mixture separately into
 each of the engine cylinders. In a two-stroke engine application, the
 compressor is preferably driven by the transmission member at twice the
 speed of the engine cylinder such that the compressor injects
 substantially the same amount of the fuel and air mixture into each of the
 engine cylinders during substantially the same portion of each cycle of
 each of the engine cylinders.
 To reduce the cost and complexity of the system, a carburetor preferably
 supplies the fuel and air mixture to the compressor and the carburetor and
 compressor are preferably exteriorly mounted and spaced from the engine
 providing a compact engine and also reducing heat transfer between the
 components. When so mounted, a flexible fluid conduit preferably
 communicates the compressor with a manifold to distribute the fuel and air
 mixture to the combustion chamber of each cylinder. The manifold
 preferably has a nozzle adjacent each of its outlets to improve dispersion
 and atomization of the mixture into the combustion chambers.
 Objects, features and advantages of this invention include providing an
 engine with a fuel and air mixture mechanically injected directly into the
 combustion chamber of each engine cylinder which provides improved
 combustion within the combustion chamber, provides a precisely controlled
 injection event driven by the movement of the piston in the main cylinder,
 reduces fuel consumption of the engine, reduces exhaust emissions from the
 engine, allows for simple adjustment of the injection timing, provides
 improved injection timing to reduce the introduction of fuel into the
 cylinder exhaust scavenge gases, can be adapted to various existing engine
 designs with minimal modifications, improves run quality and starting of
 the engine, can be used with single or multiple cylinder engines, is
 compact, relatively inexpensive, of relatively simple design and
 economical manufacture, readily adaptable to a wide range of engine
 applications, and durable, requires little maintenance and has a long
 in-service useful life.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Referring in more detail to the drawings, FIG. 1 illustrates a two-stroke
 internal combustion engine 10 having a pair of cylinders 12, 14 each with
 a combustion chamber 16, 18 defined between a cylinder head 20 and a
 reciprocating piston 22, 24 within a cylinder body 26 and a carburetor 28
 which delivers a rich fuel and air mixture to a compressor 30. The
 compressor 30 has a reciprocating piston 32 driven by a power transmission
 member 34 operably associated with a crankshaft 36 driven to rotate by
 reciprocation of the pistons 22, 24 of the main cylinders 12, 14 to
 compress the fuel and air mixture and inject it into the combustion
 chambers 16, 18 of the cylinders 12, 14. The compressor 30 is preferably
 mounted at a location spaced from the engine 10 to provide a more compact
 engine 10 which is readily adaptable to many different engine
 applications. Preferably, the compressor 30 is pivotally mounted and can
 be rotated relative to the engine 10 to vary the timing of the fuel
 injection.
 Each cylinder 12, 14 has a central bore 32 constructed to slidably receive
 a piston 22,24 for linear reciprocation between first 40 and second 42
 positions of its upper face 44 in the cylinder 12, 14 commonly referred to
 as top dead center 40 and bottom dead center 42. The cylinder head 20 is
 secured adjacent the upper edge 46 of the cylinder body 26 with a sealing
 gasket 48 received therebetween. A spark plug 50 extends through an
 opening in the cylinder head 20 and into each combustion chamber 16, 18.
 Each combustion chamber 16, 18 is defined by the upper face 44 of its
 piston 22, 24, the cylinder body 26 and the cylinder head 20. To allow
 exhaust gases to flow out of the combustion chamber 14, 16 after
 combustion, at least one, and preferably a plurality of exhaust ports 58
 are located through the side wall of each cylinder 12,14, and are
 selectively communicated with the exterior of the cylinder 12 by the
 pistons 22, 24.
 A crankcase 60 is defined between the lower face 62 of the pistons 22, 24,
 the cylinder body 26 and a lower wall 64 of the cylinder body 26. The
 crankcase 60 houses the crankshaft 36 which is powered to rotate by
 reciprocation of both pistons 22, 24 through connecting rods 66, 68 each
 pivotally connected to a piston 22, 24 at one end and connected to an
 eccentric throw of the crankshaft 36 at its other end. The pistons 12, 14
 reciprocate such that when one piston 12 is at its top dead center
 position 40 the other piston 14 is at its bottom dead center position 42.
 A pulley 70 is operably connected to the crankshaft 36 for co-rotation
 therewith and is constructed to receive and drive the power transmission
 member 34 such as a timing or "cog" belt or chain.
 To allow air flow into the crankcase 60, an air inlet 72 is provided in the
 crankcase 60 and has an engine air throttle valve 74 therein to
 selectively permit air flow therethrough. The air inlet 72 communicates
 with the crankcase chamber 61 for each piston through separate reed valves
 73. To communicate the air in the crankcase 60 with the combustion chamber
 16, 18 of each cylinder 12, 14 a transfer port 75 is located in the body
 26 of each cylinder 12, 14 opening into the crankcase 60 at one end and
 selectively communicated with the combustion chamber 16, 18 by a piston
 22, 24 at its other end. When a piston 22, 24 moves adjacent its bottom
 dead center position 42 the transfer port 75 of that cylinder 12, 14 is
 open to the combustion chamber 16, 18 and air flows from the crankcase 60
 into the combustion chamber 16, 18 of that cylinder 12, 14 to provide
 additional air for combustion and to help purge exhaust gases from the
 combustion chamber 16, 18. Subsequent piston 22, 24 travel away from the
 bottom dead center position 42 and towards the top dead center position 40
 closes the transfer port 75 to prevent air flow therethrough.
 As shown in FIGS. 3-7, the compressor 30 has a secondary cylinder 80 in a
 body 82 mounted to a crankcase body 84 with a gasket 86 received between
 them, a cylinder head 88 and the piston 32 slidably received for
 reciprocation within the cylinder 80. The compressor 30 is preferably
 mounted exteriorly of the engine 10 and has an inlet 90 through the side
 wall 92 of the body 82 constructed to communicate with the outlet 94 of
 the carburetor 28 to receive the rich fuel and air mixture and an outlet
 96 constructed to communicate with a fluid conduit 97 through a coupler 98
 to deliver the rich fuel and air mixture to the main cylinder 12,14. The
 coupler 98 has an opening therethrough concentrically aligned with the
 fluid conduit 97 and with the outlet 96 of the compressor 30 to permit
 flow of the fuel and air mixture through the coupler 98.
 To control the flow of the fuel and air mixture from the compressor 30 and
 substantially prevent reverse flow of the mixture from the fluid conduit
 into the compressor, a spring biased check valve 100 is disposed adjacent
 to the outlet 96 of the compressor 30. A valve head 102 receives one end
 of a coil spring 104 therein to bias the valve head 102 into engagement
 with a valve seat 106 to prevent flow of the fuel and air mixture through
 the outlet 96 of the compressor 30. Preferably, to facilitate assembly of
 the valve 100 within the cylinder head 88, a threaded retainer plug 107 is
 provided in the cylinder head 88 and has an annular groove 108 to receive
 and retain an end of the coil spring 104. A plunger 109 extends from the
 piston 32 and is constructed to contact and displace the valve head 102
 from the valve seat 106 when the piston 32 is adjacent the check valve 100
 the permit the fuel and air mixture to flow into the fluid conduit 97.
 Preferably, the pressure within the fluid conduit 97 and the force of the
 spring 104 tend to hold the check valve 100 closed until the plunger 109
 displaces the check valve 100 so that the fuel and air mixture is at least
 somewhat pressurized prior to being forced into the fluid conduit 97 when
 the check valve 100 is open.
 A compression chamber 110 is defined between the cylinder head 88, the side
 wall 92 and the upper face 112 of the piston 32. Adjacent the opposite
 side 114 of the piston 32, a crankcase chamber 116 is defined by the
 crankcase body 84, the side wall 92 and the piston 32.
 A connecting rod 118 is pivotally connected to the piston 32 adjacent one
 end and rotatably connected adjacent its opposite end to an eccentric
 throw 119 of crankshaft 120 of the compressor 30 which is journalled for
 rotation by bearings 122 and 126 in the crankcase body 84 of the
 compressor 30. A timing pulley 124 is connected to the crankshaft 120, and
 receives thereon the power transmission member 34 associated with the
 pulley 70 of the engine crankshaft 36 for co-rotation therewith. The
 pulley 124 preferably has one-half the effective diameter of the pulley 70
 so that the crankshaft 120 of piston 32 in the compressor 30 is driven at
 twice the rotary speed of the crankshaft 36 of the main cylinders 12, 14
 so that the compressor 30 completes one cycle for each cycle of each
 cylinder 12, 14 to separately inject the fuel and air mixture into each
 cylinder during substantially the same portion of each cycle of each
 cylinder. The compressor 30 has its minimum volume when the piston 32 is
 at its top dead center position 128 and its maximum volume when the piston
 32 is at its bottom dead center position 130. Correspondingly, the
 crankcase chamber 116 has its maximum volume when the piston 32 is at its
 top dead center position 128 and its minimum volume when the piston 32 is
 at its bottom dead center position 130. Currently preferred compressors 30
 have a displacement or swept volume (the difference between the maximum
 and minimum compression chamber volume) desirably in the range of 15% to
 40% of the engine displacement per cylinder and more preferably, in the
 range of 20% and 30%.
 The carburetor 28 is constructed to deliver a rich fuel and air mixture to
 the inlet 90 of the compressor 30 which communicates with the crankcase
 chamber 116 of the compressor 30. Preferably, the fuel and air mixture
 supplied to the compressor 30 is in the range of about 1:2 to 1:12.5 fuel
 to air thus providing a rich fuel to air mixture which has a higher fuel
 to air content than desired for optimum combustion. Currently preferred
 fuel to air ratios for combustion are in the range of 1:12 to 1:18. To
 bring the rich injected mixture into this range additional air is supplied
 to the engine combustion chambers 16, 18 through the transfer port 75 when
 it is open. Injecting the rich fuel and air mixture is desirable because
 it allows a sufficient volume of fuel to be injected over a short
 injection duration or time which improves control over the injection event
 to improve fuel economy and reduce emissions from the engine. In addition,
 the rich fuel and air mixture is injected into each cylinder 12, 14
 adjacent the spark plug 50 and enhances initial ignition of the mixture
 and the additional air added from the crankcase 60 provides additional
 oxygen to the ignited mixture to facilitate its complete combustion.
 The carburetor 28 is preferably operably associated with the engine air
 throttle valve 74 through a throttle linkage (not shown) so that the
 throttle valve 131 of the carburetor 28 meters the fuel and air mixture
 into the compressor 30 corresponding to and proportional to engine air
 flow conditions. To communicate the fuel and air mixture in the crankcase
 chamber 116 of the compressor 30 with the compression chamber 110, a
 transfer passage 134 is provided in the side wall 92 of the compressor 30
 and when the piston 32 travels towards its bottom dead center position 130
 the upper end of the transfer passage 134 is open to the compression
 chamber 110. The piston 32 movement towards its bottom dead center
 position 130 decreases the size of the crankcase chamber 116 and
 compresses the fuel therein such that when the transfer passage 134 is
 open to the compression chamber 110, the fuel and air mixture is forced
 therethrough. Also, with the check valve 100 closed, the movement of the
 piston 32 towards its bottom dead center position 130 creates a pressure
 drop in the compression chamber 110 which tends to draw the mixture into
 the compression chamber 110 when the transfer passage 134 is open. The
 residence time of the fuel and air mixture in the crankcase chamber 116 is
 believed to enhance the dispersion and mixture of the fuel in the air.
 A manifold 136 in communication with one end of the fluid conduit 97 is
 disposed adjacent to the cylinders 12, 14 and has a pair of outlets 138,
 140 each in communication with the interior of a separate cylinder 12, 14
 through at least one port in the cylinder body 26. Each outlet 138, 140
 has a nozzle 142, 144 adjacent thereto to further atomize the fuel and air
 mixture injected into the cylinders 12, 14 and improve combustion of the
 mixture. The nozzles 142, 144 are selectively communicated with the
 combustion chamber 16, 18 of the cylinders 12, 14 by the reciprocating
 pistons 22, 24 therein.
 During the power stroke of the cylinder 14, as its piston 24 moves towards
 its bottom dead center position 42, it opens the exhaust ports 58 to
 discharge the exhaust gases. Though the outlet 140 is open, the valve 100
 is preferably closed and no fuel is discharged through the outlet 140 at
 this point in the engine cycle. Upon further downward movement of the
 piston 24, air intake ports 141 are opened and fresh air from the
 crankcase chamber 60 is delivered through the transfer passage 75 and
 intake ports 141 to scavenge exhaust gases and provide air to support
 combustion for the next power stroke.
 After the piston 24 reaches its bottom dead center position 42, it travels
 back towards top dead center 40 and closes the air intake ports 141 and
 exhaust ports 58. Preferably, the valve 100 is opened to inject fuel into
 the combustion chamber 18 after the exhaust ports 58 are closed. Further
 movement of the piston 24 towards top dead center 42 compresses and mixes
 the fuel and air in the combustion chamber 18 for ignition usually
 somewhat before the piston 24 reaches top dead center 40 and another power
 stroke begins.
 A second manifold 150 is disposed adjacent to the crankcase 60 and in
 communication with the crankcase excess oil drains for each cylinder 12,
 14. The second manifold 150 communicates excess oil within the engine
 crankcase 60 with the outlet of the carburetor 28 through a flexible fluid
 conduit 152 to deliver excess engine oil to the compressor 30 to lubricate
 it. Excess oil flows through the fluid conduit 97 into the combustion
 chamber 16, 18 of the cylinders 12, 14 where it is burned with the fuel
 and air mixture.
 In an alternate embodiment, as shown in FIG. 8, the compressor 200 has a
 rotary valve 202 with a rotating valve head 204 mounted on a stem 205 and
 selectively communicating a passage 206 therethrough with a pair of
 outlets 208, 210 of the compressor 200. The rotation of the valve head 204
 is driven by the reciprocation of the piston 32 to align with the outlets
 208, 210 of the compressor 200 individually and communicate the
 compression chamber 110 with each outlet 208, 210 to deliver a metered
 amount of the fuel and air mixture separately to each cylinder 12, 14 of
 the engine 10.
 Preferably, the valve head 204 is driven to rotate at a speed corresponding
 to the engine speed to deliver the fuel and air mixture separately to each
 cylinder 12, 14 during substantially the same portion of the cycle of each
 piston 22, 24. Thus, to inject each cylinder 12, 14 during substantially
 the same portion of each cycle, the crankshaft 120 of the compressor 200
 is driven at twice the rotary speed of the crankshaft 36 of the engine 10
 and the rotating valve head 204 is driven to rotate through one complete
 revolution for each revolution of the engine crankshaft 36 and thus at
 half the rotary speed of the compressor. The valve head 204 closes the
 outlets 208, 210 of the compressor 200 when the passage 206 through the
 valve head 204 is not aligned with either outlet 208210. When both outlets
 208, 210 are closed and the piston 32 moves toward its top dead center
 position 128, the fuel and air mixture is compressed. When the valve head
 204 rotates its passage 206 into communication with one of the outlets
 208, 210, as shown in FIG. 9, the fuel and air mixture is forced
 therethrough to be delivered under pressure to a cylinder 12, 14 of the
 engine 10.
 Another embodiment of the compressor 250 is shown in FIG. 10 and has a fuel
 injection port 252 through the side wall of the cylinder body 254 of the
 compressor 250 which is selectively communicated with a passage 256, at
 least partially through the piston 32 and in communication with the
 compression chamber 258 of the compressor 250 when the piston 32 nears its
 top dead center position 128. The fuel and air mixture delivered to the
 compressor 250 by the carburetor 28 is compressed by the upward movement
 of the piston 32 with the fuel injection port 252 closed by the piston 32.
 The fuel and air mixture is compressed until it is released under pressure
 through the fuel injection port 252 when aligned with the passage 256
 through the piston 32 to inject the fuel and air mixture into the
 cylinders 12, 14 of the engine 10.
 The fuel and air mixture delivered from the carburetor 28 to the crankcase
 chamber 116 of the compressor 30 is moved through the transfer passage 134
 and into the compression chamber 110 during movement of the piston 32
 towards its bottom dead center position 130 as shown in FIG. 4. Upon
 movement of the piston 32 towards its top dead center position 128 the
 piston 32 closes the transfer passage 134, as shown in FIG. 5, and
 compresses the fuel and air mixture within the compression chamber 110.
 When the plunger displaces the valve head 102 of the check valve 100 from
 its associated valve seat 106, as shown in FIG. 6, the fuel and air
 mixture is displaced through the check valve 100 and into the fluid
 conduit 97 until the piston 32 moves sufficiently away from its top dead
 center position 128 and the plunger no longer displaces the check valve
 100 as shown in FIG. 7.
 As the piston 22, 24 in each main cylinder 12, 14 travels toward its top
 dead center position 40 the volume of the combustion chamber 16, 18
 decreases and the piston 22, 24 compresses the fuel and air mixture in the
 combustion chamber 16, 18 and increases the pressure within the combustion
 chamber 16, 18. Ignition of the mixture preferably occurs slightly before
 the pistons 22, 24 reach their top dead center position 40 and the
 subsequent combustion of the mixture drives the pistons 22, 24 toward
 their bottom dead center position 42. The downward movement of the pistons
 22, 24 eventually opens the exhaust ports 58 of the cylinders 12, 14
 allowing the exhaust gases of the burned mixture to escape through the
 exhaust ports 58.
 Movement of the pistons 22, 24 rotates the crankshaft 36 which in turn,
 through the pulleys 70, 124 and timing belt 34, rotates the crankshaft 120
 of the compressor 30. Rotation of the crankshaft 120 of the compressor 30
 causes its piston 32 to reciprocate and thereby alternately transfer the
 fuel and air mixture from its crankcase chamber 116 to its compression
 chamber 110 and then to deliver the fuel and air mixture under pressure to
 the combustion chamber 16, 18 of each cylinder 12, 14.
 Thus, the fuel and air mixture is preferably mechanically metered and
 directly injected into the combustion chamber 16, 18 within each cylinder
 12, 14 to power the engine 10 although, if desired, a low pressure
 electronic fuel injector may be mounted adjacent the compressor 30 in
 place of the carburetor 28. For a two stroke engine with two cylinders,
 the compressor 30 is driven at a 2:1 ratio with the engine crankshaft 36
 to inject the fuel and air mixture during substantially the same portion
 of each cycle of each cylinder 12, 14. The timing of the injection event
 can be readily changed by rotating one of the crankshafts 36, 120 relative
 to the other to change the portion of the cycle of the main cylinders 12,
 14 in which the injection occurs or by pivoting the compressor 30 about
 the crankshaft axis. Further, the injection event can be timed accurately
 to minimize the amount of injected fuel and air mixture which is lost with
 the exhaust scavenged gases. This greatly reduces the hydrocarbon
 emissions of the engine 10 and also greatly reduces the fuel consumption
 of the engine 10. Still further, the system is of relatively low cost and
 is easily adaptable to current engine designs and many current engine
 applications.