BACKGROUND OF THE INVENTION
The present invention relates to engines and in particular to two stroke engines. Known two stroke engines provide an advantage of firing on every two strokes, versus every four strokes of a four stroke engine. Typically, a small two stroke engine can provide more power in a simple design, however, such two stroke engines generally draw fuel into the crankcase as the piston rises, and require oil added to the fuel to lubricate main and rod bearings. Such two stroke engines have been banned in many applications due to emissions. As a result, there is a need for a two stroke engine which provides the advantages of a two stroke engine, without requiring oil added to the fuel.
Further, known two stroke motors compress air in the crankcase and then transfer the compressed air to the cylinder. The compression in the crankcase is limited by the change in volume between piston TDC and BDC. The air is only transferred from the crankcase to the cylinder when the piston uncovers a transfer port near BDC, and the amount of air transferred is limited by the limited compression of the air in the crankcase.
BRIEF SUMMARY OF THE INVENTION
The present invention addresses the above and other needs by providing a two-stroke engine without requiring oil added to the fuel. The two-stroke engine comprising a cylinder block with a crankshaft supported for rotation. A trunnion is fixedly attached to the engine block, at least one throttle body attached to the trunnion communicates with a trunnion interior. A cylinder head is rotatably attached to the trunnion, supporting a fuel injector and an ignition device. The engine includes a charge cylinder and a power cylinder, each housing a charge piston and a power piston respectively, both pistons connected to the crankshaft. Air intake into the charge cylinder is controlled to allow an airflow into the charge cylinder during the intake stroke, and capture air inside a charge piston chamber during the compression stroke. The captured air is transferred from the charge piston chamber into the power cylinder at Bottom Dead Center (BDC) and compressed during a power piston compression stroke. No oil is required to be mixed with the fuel enhancing engine efficiency.
In accordance with one aspect of the invention, there is provided a two-stroke engine having pairs of charge pistons in charge cylinders and power pistons in power cylinders, connected to a common crankshaft journal. The charge pistons draws air into the charge cylinder during a charge piston intake stroke, and compresses the air into a charge piston chamber on a charge piston compression stroke. When both the charge piston and power piston reach BDC at the same time the compressed air in the charge piston chamber flows into the power cylinder. The air is then further compressed with added fuel in the power cylinder and ignited near TDC for a power stroke.
In accordance with another aspect of the invention, there is provided a two-stroke engine including either check valves, or trunnion intake air ports and cylinder head intake air ports, which align and miss-align for air regulation into the charge cylinder. The alignment allows air to be drawn into the charge cylinder during a charge piston intake stroke, and the miss alignment allows the air to be compressed into the charge cylinder chamber during a charge piston compression stroke.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein:
FIG. 1A shows a side view of a two stroke charge piston engine according to the present invention with a top left charge piston and a bottom left power piston both at Top Dead Center (TDC) and a top right power piston and a lower right charge piston both at Bottom Dead Center (BDC).
FIG. 1B shows a top view of a four cylinder embodiment of the two stroke charge piston engine according to the present invention.
FIG. 2 shows a side view of the two stroke charge piston engine according to the present invention with a crankshaft rotated 90 degrees clockwise from FIG. 1 and the bottom right charge piston in a compression stroke and the top left charge piston in an intake stroke.
FIG. 3 shows a side view of the two stroke charge piston engine according to the present invention with the top left charge piston and the bottom left power piston both at BDC and the top right power piston and the lower right charge piston both at TDC.
FIG. 4 shows a side view of the two stroke charge piston engine according to the present invention with a crankshaft rotated 270 degrees clockwise from FIG. 1 and the bottom right charge piston in an intake stroke and the top left charge piston in a compression stroke.
FIG. 5A shows a side view of the power piston and a connecting rod of the two stroke charge piston engine according to the present invention.
FIG. 5B shows a top view of the power piston and the connecting rod of the two stroke charge piston engine according to the present invention.
FIG. 6A shows a side view of the charge piston of the two stroke charge piston engine according to the present invention.
FIG. 6B shows a top view of the charge piston of the two stroke charge piston engine according to the present invention.
FIG. 7A shows a side view of one piece charge piston and power piston connecting rod of the two stroke charge piston engine according to the present invention.
FIG. 7B shows a top view of one piece charge piston and power piston connecting rod of the two stroke charge piston engine according to the present invention.
FIG. 8 shows trunnion intake air ports of the two stroke charge piston engine according to the present invention.
FIG. 9 shows cylinder head intake air ports of the two stroke charge piston engine according to the present invention.
FIG. 10A shows the miss-alignment of the trunnion intake air ports and the cylinder head intake air ports of the two stroke charge piston engine according to the present invention when the corresponding charge piston is at BDC.
FIG. 10B shows the miss-alignment of the trunnion intake air ports and the cylinder head intake air ports of the two stroke charge piston engine according to the present invention when the charge piston is in the charge piston compression stroke.
FIG. 10C shows the miss-alignment of the trunnion intake air ports and the cylinder head intake air ports of the two stroke charge piston engine according to the present invention when the corresponding charge piston is at TDC.
FIG. 10D shows the alignment of the trunnion intake air ports and the cylinder head intake air ports of the two stroke charge piston engine according to the present invention when the charge piston is in the intake stroke.
FIG. 11 shows a side view of the two stroke charge piston engine according to the present invention having check valves in the air flow through the trunnion intake air ports and the cylinder head intake air ports.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings.
DETAILED DESCRIPTION OF THE INVENTION
The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims.
Where the terms “about” or “generally” are associated with an element of the invention, it is intended to describe a feature's appearance to the human eye or human perception, and not a precise measurement, or typically within 10 percent of a stated value.
The motion of the pistons is described below as inward when the pistons move towards a crankshaft away from the cylinder heads, and outward as the pistons move away from the crankshaft and towards the cylinder heads.
FIG. 1A shows a side view of two cooperating pairs of cylinders of a two stroke charge piston engine 10 according to the present invention with a top left charge piston 17b (see FIGS. 6A and 6B) and a bottom left power piston 30b (see FIGS. 5A and 5B), both at Top Dead Center (TDC) and a top right power piston 30a and a lower right charge piston 17a, both at Bottom Dead Center (BDC). The charge pistons 17a and 17b and power pistons 30a and 30b operate in charge cylinders volume 23a (the volume inside the cylinder sleeve 15 between the charge pistons 17a and 17b and the cylinder heads 38) and power cylinder volume 23b (the volume inside the cylinder sleeves 15 between the power piston 10a and 30b and the cylinder head 38) respectively. The charge pistons 17a and 17b, and the power pistons 30a and 30b, all ride on the same rod journal 14 of a crankshaft 11 having a main journal 12. Cylinder blocks 16 are fixed to the cylinder heads 38 and the cylinder sleeves 15 are fixed inside cylinder blocks 16. The crankshaft 11 rotates inside an engine block 13 (see FIG. 1B) and the trunnions 40 and 40′ are fixed to the engine block 13 and do not rotate.
Those skilled in the art will recognize that the paired charge pistons and power pistons may be attached to separate crankshaft journals as long as the paired charge pistons and power pistons reach BDC at or near the same time, and engines having the paired charge pistons and power pistons on separate journals are intended to come within the scope of the present invention.
During a charge piston intake stroke, the charge pistons 17a and 17b move inward, creating a vacuum in the charge cylinders volume 23a drawing air into the charge cylinders volume 23a. During a charge cylinder compression stroke, the charge pistons 17a and 17b move outward compressing the air in the charge piston cylinders volume 23a, which air passes past the charge piston valves 20 and into the charge piston chambers 18 inside the charge pistons 17a and 17b.
During the charge pistons 17a, 17b intake strokes, valves 20 are closed against the valve seats 24 by the valve springs 22 retaining the compressed air in the charge piston chambers 18. At or near BDC at the end of the charge piston intake strokes, charge piston charge passages 26a and power piston charge passages 26b align with charge piston cylinder ports and power piston cylinder ports 27a and 27b in the charge cylinders volume 23a and power cylinders volume 23b, and the compressed air captured in the charge piston chambers 18 flows 28 into the power piston cylinders volume 23b. The air is then further compressed in the power piston cylinders volume 23b and into the combustion chambers 25b during power piston compression strokes. Fuel is injected by fuel injectors 48 into the combustion chambers 25b at or near TDC to mix with the compressed air for ignition by spark plugs 48 in a direct injection engine 10. Alternatively, the fuel may be added to the air drawn into the charge cylinders volume 23a in a non-direct injection engine, through fuel injection into a throttle body 50 (see FIG. 1B) or by carburetors.
The compressed air-fuel mixture in the combustion chambers 25b is ignited by the spark plugs 46 within the combustion chambers 25b, expanding gases drive the power pistons 30a and 30b towards the crankshaft 11. The power piston motion generates mechanical power, which is transferred via the power piston rods 32 to the crankshaft 11, converting the linear motion of the power pistons 30a and 30b into rotational energy of the crankshaft 11.
Once the power pistons 30a and 30b have completed a power stroke and are at or near BDC, the spent gases are expelled from the power cylinder volume 23b through the exhaust ports 34a. The exhaust ports 34a are preferably opposite to the charge piston cylinder ports 27a and air 28 rushing into the power cylinder volume 23b through the charge piston cylinder ports 27a further urges the exhaust flow 36 to exit the power cylinder volume 23b through the exhaust ports 34a. The exhaust system includes exhaust flow passages 34b in cylinder heads 38 and into the trunnions 40 providing fixed exhaust ports 37 (see FIG. 1B) in the trunnions 40.
Cylinder heads 38 pivot on the fixed trunnions 40 and carry the pivoting cylinder blocks 16 allowing the cylinder blocks 16 carrying the sleeves 15 to pivot on the trunnions 40 as the pistons 17a, 17b, 30a and 30b reciprocate in the cylinders volume 23a and volume 23b, as shown in FIGS. 2 and 4. The charge piston 17a and 17b connect to the rod journal 14 without a connecting rod, and the pivot of the cylinder blocks 16 is determined by the geometry of the rod journal 14, the charge pistons 17a and 17b, and the trunnions 40. The pivoting of the blocks 16 on the fixed trunnions 40 maintains alignment of the pistons 17a, 17b with the cylinders volume 23a. The power pistons 30a and 30b ride on piston pins 33 and align with the cylinders volume 23b.
The heads 38 form the tops of the charge chambers 25a and combustion chambers 25b and house elements, for example, the spark plugs 46 and fuel injectors 48. Head ports 43 allow for the intake of fresh air into the charge cylinders volume 23a and the exhaust ports 34 allows expulsion of exhaust gas flows 36 from the engine 10.
Piston rings 31 reside around the charge pistons 17a and 17b and power pistons 30a and 30b above and below the charge passages 26a and 26b, creating a seal between the pistons 17a, 17b, 30a, and 30b and the cylinder sleeves 15 fixed, reducing or prevent the leakage of compressed air during piston strokes and when the compressed air is transferred from the charge piston chambers 18 into the power cylinders volume 23b.
Trunnion ports 42 and head ports 43 are miss-aligned at TDC and BDC and are only aligned during a charge piston intake stroke.
While the engine 10 is described above with pivoting cylinders, those skilled in the art will recognize that a two stroke charge piston engine may also have fixed cylinders and connecting rods connecting both the charge piston and the power piston to the crankshaft, and any two stroke engine having a charge piston including a chamber capturing compressed air during a charge piston compression stroke, and transferring the compressed air to a power piston at BDC, is intended to come within the scope of the present invention.
FIG. 1B illustrates a detailed top view of a four pairs of pistons version of the engine 10, showing the mechanical arrangement and interaction of the charge pistons 17a, 17b, 17a′ and 17b′, and power piston 30a, 30b, and 30a′ and 30b′ and related components. The trunnions 40 may be two pieces, 40 and 40′. The pistons 17a′, 17b′, 30a′ and 30b′ all riding on a second rod journal 14′ of the crankshaft 11 not shown in FIG. 1A, and the main journal 12 rotated in the engine block 13. Intake air flows 44 and 44′ enter trunnion interiors 40a of the trunnions 40 and 40′ of the engine 10 through the throttle bodies 50 and 50′, and enter the charge cylinders volume 23a through trunnion ports 42 when aligned with head ports 43 (see FIG. 1A). The elements in FIG. 1B not shown in FIG. 1A are indicated by an apostrophe added to the element number in FIG. 1A.
FIGS. 2 to 4 illustrate different operational phases of the two-stroke charge piston engine 10, highlighting the positions of the charge pistons 17a and 17b and power pistons 30a and 30b as the crankshaft 11 rotates. In FIG. 2, with the crankshaft rotated 90 degrees clockwise from FIG. 1, the bottom right charge piston 17a is in a compression stroke, moving outward to compress the air in the charge cylinder volume 23a, while the top left charge piston 17b is in the intake stroke, moving inward to draw fresh air into the charge cylinder volume 23a. The ports 42 and 43 are miss-aligned in the lower right charge cylinder volume 23a to allow the air in the lower right charge cylinder volume 23a to be compressed, and the ports 42 and 43 are aligned in the top left charge cylinder to allow the air to be drawn into the top left charge cylinder volume 23a.
FIG. 3 shows the engine with the top left charge piston 17b and bottom left power piston 30b both at BDC, the charge piston 17b having completed a intake stroke and the power piston 30b having completed a power stroke. The top right power piston 30a and lower right charge piston 17a are at TDC, the power piston 30s having completes a power piston compression stroke and the charge piston 17a having completed a charge piston compression stroke.
FIG. 4 shows the crankshaft 11 rotated 270 degrees clockwise from FIG. 1. The bottom right charge piston 17a is in a charge intake stroke, moving inward, while the top left charge piston 17b is in a compression stroke, moving outward to compress air in the charge cylinder volume 23a. The top right power piston 30a is in a power stroke and the bottom left power piston 30b is in a compression stroke. These figures show the synchronized movement of the pistons. The trunnion ports 42 and the head ports 43 are only aligned for the charge piston intake stroke and misaligned are all other times.
FIG. 5A shows a side view of the power piston 30a and 30b, connected to the connecting rod 32 by piston pin 33 and FIG. 5B shows a top view of the power pistons 30a and 30b . . . . The piston rings 31 reside above and below the power piston charge passage 31 create a tight seal with the cylinder sleeves 15, preventing pressure loss during the compression and combustion strokes. The power piston charge passage 26b is also illustrated, located between the perimeter of the power piston 30 and its top surface. This passage allows for the communication of air from the charge piston chamber 18 into the combustion chamber 25b.
FIG. 6A shows a side view of the charge piston 17a and 17b and FIG. 6B shows a top view of the charge piston 17a and 17b. The charge piston charge passage 26a connects the charge piston chamber 18 to the exterior of the charge piston 17a and 17b.
FIG. 7A and FIG. 7B an alternative embodiment of the pistons and rod. A one-piece connecting rod assembly 32′ couples the charge piston 17′ and the power piston 30 to the crankshaft 11. In FIG. 7A, the side view shows how the charge piston 17′ is positioned above the power piston 30, both connected by the one-piece connecting rod 32′, which couples linear motion of the pistons 17′ and 30 with rotational motion of the crankshaft 11. The piston pin 33′ secures the charge piston 17′ to the upper section of the connecting rod, while the piston pin 33 connects the power piston 30 to the lower part. This design allows both pistons to move in unison, facilitating efficient transitions between the intake, compression, combustion, and exhaust strokes. In FIG. 7B, the top-down view highlights the alignment of the pistons along the connecting rod 32′, with the piston pins 33, 33′ connecting the pistons to the rod. The operation of engine having the pistons and rods in FIGS. 7A and 7B is otherwise similar to the operation of the engine 10.
FIGS. 8 and 9 show the cooperation of the ports 42 and 43. The widths A1 and A3 of the ports 42 and 43 and the separation A2 and A4 of the of the ports 42 and 43 is determined based on the amount of the pivot of the cylinder blocks 16 to only align the ports 42 and 43 during the charge piston intake stroke, and misalign the ports at all other times, with an exception that in some operation the alignment may be extended to capture some addition air after BDC of the charge piston intake stroke when momentum of the intake air flow 44 may add additional air into the charge piston cylinder volume 23a after the charge piston 17 or 17b passes BDC.
FIGS. 10A-10D illustrate the misalignment and alignment of the trunnion ports 42 and the head ports 43 during different strokes of the two-stroke charge piston engine 10 operation. FIG. 10A shows the ports misaligned when the charge piston 17a or 17b is at BDC, to capture the air in the charge piston cylinder volume 23a during the following compression stroke.
FIG. 10B shows the misalignment of the trunnion ports 42 and the head ports 43 during the charge piston compression stroke, as the charge piston 17 moves outward, preventing air from escaping, and allowing full compression of the air in the charge piston cylinder volume 23a.
FIG. 10C shows the trunnion ports 42 and the head ports 43 misalignment when the charge pistons 17a and 17b reaches TDC, to complete the compression of the air captured into the charge piston chamber 18 of the charge pistons 17a and 17b and in the power piston cylinder volume 23b prior to ignition.
FIG. 10D illustrates the alignment of the trunnion ports 42 and the head ports 43 during the intake stroke, where the charge pistons 17a and 17b are moving outward drawing air into the charge piston cylinder volume 23a. These figures underscore the importance of controlling port alignment and misalignment to manage intake, compression, and airflow efficiently during each phase of the two-stroke cycle.
FIG. 11 provides a side view an alternative two-stroke charge piston engine 10 according to the present invention, focusing on the incorporation of check valves 45 in the trunnion or in the head, replacing the trunnion intake air ports 42 and the cylinder head intake air ports 43. The check valves 45 ensure that air flows into the engine during the intake stroke while preventing any backflow of air out of the charge piston cylinder during the charge piston compression stroke.
While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.
Patent Grant
12291993
