2-cycle engine

Abstract

A 2-cycle internal combustion engine in which the intake cycle begins before and ends after the exhaust cycle, resulting in a longer power stroke, increased torque and greater efficiency is disclosed herein. In the preferred embodiment, the 2-cycle engine has a power stroke of about 160 degrees, an exhaust stage of about 70 degrees, and an intake cycle of about 110-115 degrees.

Claims

1. A 2-cycle engine comprising: an engine block defining a bore with a longitudinal axis; a piston disposed within the bore for linear movement parallel to a longitudinal axis of the bore and operatively connected to a crankshaft; an intake port in fluid communication with the bore and located near the top of said bore; and an exhaust port in fluid communication with the bore and located near the bottom of said bore; wherein in operation of the engine, the engine undergoes combustion cycles of intake, compression, combustion/expansion and exhaust; wherein during the combustion/expansion cycle, the intake port opens at about 135-140 degrees after top dead center and closes at about 250 degrees after top dead center while the exhaust port opens after the intake port at about 160 degrees after top dead center and closes at about 233 degrees after top dead center; and wherein the intake port and the exhaust port are each oriented transverse to the longitudinal axis of the bore, the intake port and the exhaust port positioned in different ones of laterals planes which are defined perpendicular to the longitudinal axis and that are spaced from one another along the longitudinal axis of the bore.

2. The 2-cycle engine of claim 1, wherein the intake port is controlled by a valve.

3. The 2-cycle engine of claim 1, wherein the exhaust port comprises an opening in a wall of the bore, the exhaust port having a trapezoidal cross-sectional configuration.

4. The 2-cycle engine of claim 3, wherein the exhaust port having a trapezoidal cross-sectional configuration is further defined as an isosceles trapezoidal cross-section.

5. The 2-cycle engine of claim 1, wherein the engine is naturally aspirated.

6. A method of operation of the 2-cycle engine of claim 1, the method comprising: an intake cycle that begins at about 135-140 degrees after top dead center and ends at about 250 degrees after top dead center; and an exhaust cycle that begins at about 160 degrees after top dead center and ends at about 230 degrees after top dead center.

7. The 2-cycle engine of claim 6, wherein the intake cycle is controlled by operation of a valve.

8. The 2-cycle engine of claim 6, wherein an exhaust cycle is controlled by movement of the piston against the exhaust port.

9. The 2-cycle engine of claim 6, wherein an exhaust cycle is controlled by movement of the piston against the exhaust port and wherein the exhaust port defines a trapezoidal cross-sectional shape.

10. The 2-cycle engine of claim 6, wherein the engine is naturally aspirated.

11. The 2-cycle engine of claim 1 further comprising an electronic fuel injector configured to inject fuel into the bore at an appropriate, predetermined point in the combustion cycle.

Description

BRIEF DESCRIPTION OF THE. DRAWINGS

(1) FIG. 1 is a schematic illustration of a preferred embodiment of the 2-cycle engine of the present invention

(2) FIG. 2 is a circular diagram of the stages of the combustion cycle in a typical 2-stroke engine.

(3) FIG. 3 is a circular diagram of the stages of the combustion cycle in a preferred embodiment of the present invention.

(4) FIG. 4 is an enlarged cross-section of the exhaust port in the preferred embodiment of the 2-cycle engine of the present invention, as seen along line 4-4 of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT AND OPERATION OF THE INVENTION

(5) For a better understanding of the invention and its operation, turning now to the drawings, Referring first to FIG. 1, a preferred embodiment of a 2-cycle engine of the invention is schematically shown therein. The engine 10 is defined by an engine block 12, a crankcase 14 and a cylinder head 16. The engine block contains a bore 18 defining a combustion cylinder. A piston 20 is disposed within the bore 18 for movement therein parallel to the longitudinal axis 22 of the bore 18. Piston 20 is operatively connected to crankshaft 24 by a connecting rod 26, whereby linear motion of the piston 20 within the bore 18 will translate to rotational movement to the crankshaft 24.

(6) The cylinder head 16, in the embodiment shown, may preferably include a fuel injector, such as electronic unit injector 28 which injects fuel into the bore 18 at the appropriate, predetermined point in the combustion cycle. An intake valve 30 is in fluid communication with the bore 18 and is operatively controlled by a valve 32. When the valve 32 is open, as shown in FIG. 1, air can be drawn through the intake port 30 and into the bore 18 for use in the combustion process. In the embodiment shown, the intake port and valve are contained within the cylinder head 16 and thus are located at or near the top of bore 18.

(7) An exhaust port 34 is also in fluid communication with the bore 18. In the preferred embodiment, exhaust port 34 defines a trapezoidal shape, which is not merely a design choice but rather is engineered for a more versatile engine, regardless of fuel type. Unlike the intake 30, and those intake orifices taught in the prior art, preferred exhaust port 34 is located below a lateral plane that intersects the midline of intake port 30. In this configuration, it would be understood that intake port 30 and exhaust port 34 are in different lateral planes which are perpendicular to longitudinal axis 26. In FIG. 1, the piston 20 is shown near the lowermost end of the bore 18, which corresponds to bottom dead center (“BDC”), The exhaust port 34 is preferably located just above the top of piston 20 when the piston is at BDC. As explained below, by locating the exhaust port 34 low in the bore 18 delays opening of the exhaust pathway to later in the combustion cycle, thus increasing the effective length of the power stroke.

(8) With reference now made to FIGS. 2 and 3, the differences in the combustion cycle as between the prior art 2-cycle engine and the 2-cycle engine of the present invention can be compared. These FIGS. depict the stages of a combustion cycle in reference to the rotational movement of the crankshaft and are typically referred to as “circular”, “clock”, or “pie” diagrams. The dock diagram in FIG. 2 shows the stages of a combustion cycle of a typical prior art 2-stroke engine, such as that disclosed in the aforementioned U.S. Pat. No. 6,044,812, the entire disclosure of which is incorporated herein by reference. The dock diagram of FIG. 3 shows the stages of a combustion cycle of an embodiment of the present invention.

(9) As seen in FIG. 2, the prior art 2-stroke engine began the exhaust cycles at approximately 90-94 degrees (+/−2 degrees) from top dead center (“TDC”) and ended at approximately 231-235 degrees (+/−1-2 degrees) from TDC. This figure also shows that the intake cycle begins at approximately 126-127 degrees (+/−2 degrees) from TDC and ends at approximately 231-235 degrees (+1-2 degrees) from TDC. In the preferred embodiment of the 2-stroke engine of the invention (FIG. 3) it is seen that the order of the exhaust and intake cycles are reversed from prior art engines. Specifically, at about 135-140 degrees (+/−2 degrees) from TDC, the intake cycle begins when the intake valve 32 begins to open and does not close until about 250 degrees (+/−2 degrees) from TDC. The exhaust cycle begins at about 160 degrees (+/−2 degrees) from TDC when the exhaust port begins to open and ends when the piston has blocked the exhaust port at about 230 degrees (+1-2 degrees) from TDC.

(10) Accordingly, the 2-cycle engine of the present invention reverses the sequence of the intake and exhaust stages of the combustion cycle. Not only does the intake cycle begin earlier, but it also last longer than the exhaust cycle, another difference from the prior art 2-cycle engines. These modifications result in significant improvements in engine function over prior art designs. For example, the airflow through the bore 18 is improved as fresh air is drawn in through the intake port 34 at the top of the bore 18 before the gasses from burning of the air/fuel mixture escape out the exhaust port. The improved unidirectional airflow allows the engine to be cranked naturally aspirated and eliminates the need for a turbo to crank heavy and expensive blowers or air pumps. In an embodiment with a turbo (i.e. free, exhaust-driven pressurized air), said turbo is thus free to take over aspiration for continued engine acceleration and be fueled for maximum power output. This is made possible by the unique intake and exhaust placement of the instant new design. The new 2-cycle unidirectional air flow allows for an unexpected, novel phenomenon that makes some or all of the benefits of the instant engine possible. That is due to the fact that as a cylinder ignites its air/fuel mixture at or near TDC that at some point, at some degree of crankshaft rotation of the pistons downward travel relationship in the cylinder will create enough vacuum to pull enough fresh air in through the intake valves assisted by the venture-type orifice being exposed at the top of the trapezoidal exhaust port as the piston travels downward enough to keep those burnt gases low in the cylinder. The intake valves being in the top of the cylinder and the more exhaust port being exposed as the piston travels downward keeps everything flowing in the same direction. This also allows for an abundance of cylinder cleaning air. This air will also assure that there is more than adequate air to completely burn all fuel that was supplied to the cylinder.

(11) Another improvement resulting from these modifications is the increased duration of the power stroke (i.e., combustion/expansion cycle(s)) from approximately 120 degrees (+/−2 degrees) in the prior art (and in actuality starting to end the power stroke at 93° as the exhaust valves begin to open) to about 160 degrees (+/−2 degrees) in the present invention. The longer power stroke results in increased torque output.

(12) FIG. 4 shows a preferred cross sectional shape of the exhaust port 34 of the present invention. As described above, the preferred shape of exhaust port 34 is trapezoidal, with the wider parallel side 40 located closer to the bottom of the bore 18 and the narrower parallel side 42 located closest to the cylinder head 16. This to cause a venturi type effect or the speeding up of the exhaust gases as they are continuing to travel downward in the cylinder. As the piston moves downward more of the port is exposed to help evacuate the cylinder of burnt gases so the cylinder can be purged completely and flushed with clean ambient air. Not only giving clean air for the next engine cycle in the cylinder but flushing out the engines exhaust and help filter burnt air gas exhaust by helping to purify exhaust concentrating with cleaner air.

(13) Although not shown in the FIGS., it will be understood by the skilled worker that additional modifications may be made to the engine of the invention. For example, in an alternate embodiment, an exhaust driven turbocharger may be employed to further increase efficiency. Various other substitutions or modifications to the embodiments illustrated and described may suggest themselves to those skilled in the art upon reading this disclosure. Accordingly, the illustrations and examples provided herein are for explanatory purposes and are not intended to limit the scope of the appended claims.