Patent Application
20060048729
This invention relates generally to piston driven apparatuses, such as pumps and engines. In one specific embodiment, the invention relates to two-stroke cycle engines.
Crank case scavenged, cylinder ported two-stroke cycle engines of the prior art are commonly used for a wide variety of light duty applications. Two-stroke cycle engines of the prior art, however, have several shortcomings.
One shortcoming arises from the fact that prior art two-stroke cycle engines typically have intake and exhaust ports at about the same level. This results in some of the intake fuel-air mixture following the exhaust out of the exhaust port, thereby decreasing efficiency and increasing emissions.
Another shortcoming of prior art two-stroke engines arises because some of the engine's lubricating oil can pass to the exhaust port, thus producing emissions and often leaving deposits on the walls of the exhaust port, thus forming a hard carbon layer or “coking” which restricts the exhaust and causes other problems.
Yet another shortcoming of prior art two-stroke cycle engines involves the difficulty of bringing intake fuel-air mixture from the bottom of the engine cylinder to the top of the cylinder where the igniter is located. During part throttle operation, most of what remains in the cylinder are burnt gases. Moving the small amount of fresh intake mixture undiluted by burnt gases to the igniter becomes very problematic. Misfires are typical, resulting in irregular operation, and surging. Various arrangements, such as loop scavenging or deflecting pistons, have been suggested for passing the mixture to the combustion chamber without some of it escaping via the exhaust port. None of these various arrangements, however, have been wholly successful.
Yet another shortcoming of prior art two-stroke cycle engines involves the difficulty of lubricating the cylinder wall and piston. Having the piston pass over both intake and exhaust ports around the lower circumference of the cylinder limits the amount of oil that can be delivered to the upper cylinder wall. Piston thrust against the cylinder wall then results in scuffing and premature wear.
Yet another shortcoming of prior art two-stroke cycle engines involves the use of the crank case as the delivery pump for the scavenge charge. This results in delivery of the charge at very limited pressure, limiting control of the scavenge process. Mixing oil with the fuel or an expensive oiling system is also required, as are more expensive bearings that will survive on oil vapor only.
Fuel injection systems have been utilized in order to reduce emissions and to delay fuel injection until an exhaust port is closed. However, such systems are generally costly and often involve new problems.
For many years, efforts have been made to deliver a fresh fuel-air charge directly to a spark plug to insure ignition with every piston stroke. None of these efforts, however, have been truly successful.
In my presently pending U.S. patent application Ser. No. 10/804,351, I disclosed an advanced two-stroke cycle engine which avoids the aforementioned problems in the prior art. However, even that advanced two-stroke cycle engine design can be improved upon if it can be modified to provide increased power and fuel efficiency and decreased pollution.
The invention provides such an improvement. The invention is an apparatus useful in a two-stroke cycle engine, the apparatus comprising (a) a piston cylinder having a piston cylinder upper portion, a piston cylinder lower portion, a piston cylinder side wall with an interior surface and a piston cylinder top cover, the piston cylinder further having first and second intake ports defined within the piston cylinder upper portion and an exhaust port defined within the piston cylinder lower portion; (b) an intermediate piston cylinder head fixedly disposed within the piston cylinder so as to separate the piston cylinder upper portion from the piston cylinder lower portion, the piston cylinder head extending transversely across the interior of the piston cylinder and having an upper surface and a lower surface, the piston cylinder head being disposed within the piston cylinder so as to define at least one head gap between the interior surface of the piston cylinder side wall and the piston cylinder head; (c) a piston slidably disposed within the piston cylinder, the piston having a piston side wall with an exterior surface, the piston being sized and dimensioned to be operatively sealable with the interior surface of the piston cylinder side wall, the piston also having a lower piston portion with a lower piston portion upper surface disposed within the lower piston cylinder portion and an upper piston portion comprising at least one upright extension member, the at least one upright extension member having an uppermost portion, the at least one upright extension member extending upwardly from the lower piston portion through the at least one head gap and being extendable upwardly into the upper cylinder portion, the lower piston portion upper surface being adapted to cooperate with the interior surface of the piston cylinder side wall, the at least one upright extension member and the lower surface of the piston cylinder head to define an enclosed lower chamber, the piston being operatively connected to a crank shaft by a piston rod and adapted to reciprocate within the piston cylinder between an upward cycle and a downward cycle; (d) a piston top wall disposed transversely within the piston cylinder and attached to the uppermost portion of the at least one upright extension member, the piston top wall being adapted to cooperate with the interior surface of the piston cylinder side wall to define an enclosed upper chamber in the upper cylinder portion immediately above the piston top wall, the piston top wall also being adapted to cooperate with the at least one upright extension member, the interior surface of the piston cylinder side wall and the upper surface of the piston cylinder head to define an enclosed intermediate chamber immediately below the piston top wall; (e) a tube connecting the upper chamber to the lower chamber in fluid type communication; (f) an upper tube valve for alternatively (i) allowing the flow of fluids between the upper chamber and the tube (ii) preventing the flow of fluids between the upper chamber and the tube; (g) a lower tube valve for alternatively (i) allowing the flow of fluids between the tube and the lower chamber and (ii) preventing the flow of fluids between the tube and the lower chamber; (h) a first upper chamber intake valve for controlling the flow of fluids to the first intake port defined within the piston cylinder upper portion; (i) a second upper chamber intake valve for controlling the flow of fluids to the second intake port defined within the piston cylinder upper portion; (j) means for alternatively allowing the transfer of fluids between the intermediate chamber and the lower chamber and for alternatively preventing the transfer of fluids between the intermediate chamber and the lower chamber; and (k) an igniter disposed proximate to the lower chamber for igniting fluids within the lower chamber.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description, appended claims and accompanying drawings where:
The following discussion describes in detail one embodiment of the invention and several variations of that embodiment. This discussion should not be construed, however, as limiting the invention to those particular embodiments. Practitioners skilled in the art will recognize numerous other embodiments as well.
The invention is an apparatus 10 which can be useful in a two-stroke engine 11. The apparatus 10 of the invention is illustrated in
By way of background, the underlying concept of the invention is illustrated in
The apparatus 10 comprises a uniquely configured piston 13 disposed within a uniquely configured piston cylinder 14. The piston cylinder 14 has a piston cylinder upper portion 16, a piston cylinder lower portion 18 and a piston cylinder top cover 20. The piston cylinder 14 further comprises one or more piston cylinder side walls 22, each having an interior surface 24.
In the embodiments wherein the apparatus 10 is used in a two-stroke cycle engine 11, at least one intake port 26 is defined within the piston cylinder upper portion 16 and at least one exhaust port 28 is defined within the piston cylinder lower portion 18. The intake port 26 is adapted to emit a fuel-air mixture 30 into the upper portion 16 of the piston cylinder 14, such as via a carburetor or fuel injector (not shown).
An intermediate piston cylinder head 32 is fixedly disposed within the piston cylinder 14 so as to separate the piston cylinder upper portion 16 from the piston cylinder lower portion 18. The piston cylinder head 32 extends transversely across the interior of the piston cylinder 14 and has an upper surface 34, a lower surface 36 and side walls 38.
The piston cylinder head 32 can be fixedly mounted in the piston cylinder 14 by any suitable method, such as by welding, force fit, or being formed integrally within the piston cylinder 14. A resilient seal 40 is optionally provided between the piston cylinder head 32 and the interior wall of each piston upright extension member 66 (described below).
The piston cylinder head 32 is disposed within the piston cylinder 14 so as to define at least one head gap 42 between the piston cylinder side wall 22 and the piston cylinder head 32. In the embodiments illustrated in the drawings, the piston cylinder head 32 has a pair of opposed flat side walls 38, so as to define a pair of opposed head gaps 42.
Also in the embodiment illustrated in the drawings, the cylinder has a plurality of cooling fins 44 disposed about its exterior. Alternatively, the cooling fins 44 can be eliminated and interior passageways can be provided for liquid cooling.
The piston 13 is slidably disposed within the piston cylinder 14. The piston 13 is operatively connected to a crank shaft 46 by a piston rod 48 and is adapted to reciprocate within the piston cylinder 14 between an upward cycle and a downward cycle. A crank pin 50 is rotatably mounted in the lower portion 59 of the piston 13. The piston rod 48 has its upper portion disposed about the crank pin 50 and extends to engage a conventional crankshaft 46 disposed within a conventional crank case 56.
The piston 13 is best visualized in
The piston 13 has a lower piston portion 59 disposed within the lower piston cylinder portion. The lower piston portion has an upper surface 60 which is adapted to cooperate with the interior surface 24 of the piston cylinder side wall 22, the upright extension members 66 and the lower surface 36 of the piston cylinder head 32 to define an enclosed lower chamber 62. Where the apparatus 10 is used in a two-stroke cycle engine 11, the lower chamber 62 serves as a combustion chamber.
The piston 13 also has an upper piston portion 64 which comprises at least one upright extension member 66. The at least one upright extension member 66 extends upwardly from the lower piston portion 59, through the at least one head gap 42 and is extendable upwardly into the piston cylinder upper portion 16.
In the embodiments illustrated in the drawings, the at least one upright extension member 66 comprises a pair of opposed upright extension members 66. In such embodiments, the piston cylinder head 32 is disposed within the piston cylinder 14 so as to define a pair of opposed head gaps 42 between the interior surface 24 of the piston cylinder side wall 22 and the piston cylinder head 32. Each of the pair of opposed upright extension members 66 extends upwardly from the piston lower portion 59 through one of the two opposed head gaps 42, and is extendable into the piston cylinder upper portion 16.
A piston top wall 68 is disposed transversely within the piston cylinder 14 and is attached to the uppermost portion of the at least one upright extension member 66. The piston top wall 68 is adapted to cooperate with the interior surface 24 of the piston cylinder side wall 22 to define an enclosed upper chamber 70 in the piston cylinder upper portion 16 immediately above the piston top wall 68. Where the apparatus 10 is used in a two-stroke cycle engine 11, the upper chamber 70 serves as an intake chamber.
The piston top wall 68 is also adapted to cooperate with the at least one upright extension member 66, the interior surface 24 of the piston cylinder side wall 22 and the upper surface 34 of the piston cylinder head 32 to form an enclosed intermediate chamber 72. Where the apparatus 10 is used in a two-stroke cycle engine 11, the intermediate chamber 72 serves as an scavenge pump.
A valve 74 is provided within the piston cylinder 14 for alternatively allowing the transfer of fluids into the intermediate chamber 72 and for alternatively preventing the transfer of fluids from the intermediate chamber 72.
In the embodiment illustrated in
In the embodiments illustrated in
Means 76 are also provided for alternatively allowing the transfer of fluids between the intermediate chamber 72 and the lower chamber 62 and for alternatively preventing the transfer of fluids between the intermediate chamber 72 and the lower chamber 62. In one embodiment, such means 76 are provided by a valve 78.
The means 76 for alternatively allowing the transfer of fluids between the intermediate chamber 72 and the lower chamber is alternatively provided by at least one scavenge passage 86 disposed within the at least one upright extension member 66. During a portion of both the upward and downward cycles of the piston 13, the scavenge passages 86 are open to both the intermediate chamber 72 and the lower chamber 62. Thus, during the downward cycle of the piston 13, the piston 13 compresses fluids in the intermediate chamber 72 between the piston cylinder head 32 and the piston top wall 68. Upon such compression, the fluids within the intermediate chamber 72 are forced into the lower chamber 62 via the scavenge passages 86.
In the embodiment illustrated in
The size and length of the scavenge passages 86 are predetermined and designed to effect greater or lesser force into the scavenge passages 86 to provide sufficient fresh mixture at a predetermined location within the lower chamber 62 to insure ignition on every stroke. The scavenge passages 86 are also designed and sized to effect the flow of a large percentage of the fuel-air mixture 30 from the intermediate chamber 72 to the lower chamber 62. Appropriate scavenge passage configurations provide delivery of a desired amount or percentage of fuel-air mixture 30 to a predetermined location in the lower chamber 62. As illustrated in
At the top of the piston cycle, all of the scavenge passages 86 are closed by the piston cylinder head 32, thereby preventing the communication of fluids between the intermediate chamber 72 and the lower chamber 62.
In embodiments wherein the apparatus 10 is to be used in a two-stroke cycle engine 11, the apparatus 10 further comprises an igniter 92 disposed proximate to the lower chamber 62 for igniting fluids within the lower chamber 62. Typically, such igniter 92 is provided by an ordinary spark plug. In one embodiment, the igniter 92 is positioned centrally, so as to minimize the combustion period, and to thereby improve combustion.
As illustrated in
The plurality of the vertical seal strips 96 are provided so as to define two diametrically opposed thrust quadrants 100 and two diametrically opposed exhaust quadrants 102 on the interior surface 24 of the cylinder wall. The thrust quadrants 100 are indicated in
The vertical seal strips 96 serve four functions: gas sealing, dissipation on heat at the feather edge of the upright extension members 66, controlling oil on the piston cylinder interior surface 24 and the piston 13 and preventing rotation of the piston 13.
A lateral seal strip 106 is disposed on each side wall of the piston cylinder head 32 to seal the upright extension members 66 with the piston cylinder head 32. The respective ends on of the lateral seal strips 106 are each mated to edges of a vertical seal strip 96.
In the embodiments illustrated in the drawings, the seal strips 96 and 106 are urged radially towards the piston 13 by elongated, undulating, sine wave spring members 104 mounted in the seal strip slots 98.
A plurality of piston rings 108 are disposed in annular grooves 109 in the lower portion 59 of the piston 13 to provide effective sealing between the piston 13 and the cylinder wall 22. In the embodiment illustrated in the drawings, five piston rings 108 are disposed in respective piston ring grooves 109 in the piston 13. A first piston ring 108a is mounted in a piston ring groove 109 in the upper end of the lower piston portion 59, and three piston rings 108, the second piston ring 108b, the third piston ring 108c and the fourth piston ring 108d are mounted in respective piston ring grooves 109 in a lower portion 59 of the piston 13. A fifth piston ring 108e is disposed in a piston ring groove 109 at the bottom of the lower piston portion 59.
The piston rings 108 are of conventional type, are oversized relative to the piston cylinder 14, and each have a gap 111, thus to exert constant radially outward spring pressure against the piston cylinder wall 22 to cause the piston ring 108 to fill any clearance gap between the piston 13 and the cylinder 14.
Each piston ring 108 has defined in its periphery two diametrically opposite thrust quadrants 110, and two diametrically opposed exhaust quadrants 112. These quadrants correspond to the quadrants defined by the seal strips 96. Some of the quadrants 110 or 112 of the piston rings 108, except for the first piston ring 108a, have peripheral portions reduced in diameter, as by being ground down, as indicated in
The piston rings 108 are adapted to enable lubrication of upper portions of the piston 13, and are so arranged and configured that oil may pass via the upright extension members 66, thus to lubricate the upper piston cylinder wall 22 and adjacent components. Oil can pass upwardly on the piston cylinder wall 22 to lubricate the upright extension members 66 relative to the piston cylinder wall 22 while these same rings seal the lower chamber 62.
Notches 114 in the respective piston rings 108 align with the vertical seal strips 96 to prevent contact between the piston rings 108 and the vertical seal strips 96. The notches 114 in the piston rings 108 serve the additional purpose in preventing piston ring rotation.
The first piston ring 108a serves as a compression ring. This first piston ring 108a has a uniform, full diameter. This piston ring 108a operates to prevent oil from reaching the upper chamber 70 and provides a compression seal for the intermediate chamber 72.
The second piston ring 108b also provides the function of a compression ring. This second piston ring 108b has a reduced diameter at its thrust quadrants 110. The purpose of this ring 108b is to allow oil to move up the cylinder 14 on the thrust quadrants 100 and to lubricate the piston upright extension members 66. This piston ring 108 also helps to seal the lower chamber 62.
The third piston ring 108c acts as an oil scraper. The third piston ring 108c has thrust quadrants 110 of reduced diameter to allow oil to move up the cylinder wall 22 via the thrust quadrants 110 to lubricate the upright extension members 66 and the cylinder wall 22.
The fourth piston ring 108d operates as an oil control piston ring 108. The fourth piston ring 108d has a reduced diameter at its exhaust quadrants 112. This ring 108 helps to control oil delivery on the thrust quadrants 100 and to minimize oil to the exhaust quadrants 102.
The fifth piston ring 108e acts as an oil scraper. This lowermost piston ring 108e has a reduced diameter at its thrust quadrants 110. This piston ring 108e acts to scrape oil from the exhaust quadrants 102 and to allow oil to move up the thrust side 110 of the cylinder 14.
In operation, the two-stroke cycle engine 11 illustrated in
After the piston 13 begins its upward movement, the inertial valve 74 is opened. Fresh fuel-air mixture 30 flows from the upper chamber 70 to the intermediate chamber 72 as the piston top wall 68 begins contracting the upper chamber 70 and expanding the intermediate chamber 72. The scavenge passages 86 are momentarily opened and then closed again to seal closed the lower chamber 62. As the piston 13 continues thereafter to move upwardly, fresh fuel-air mixture 30 within the lower chamber 62 becomes compressed.
As the piston 13 passes its uppermost position and begins its downward cycle, the inertial valve 74 is closed and the upper chamber 70 is minimized in size. The intermediate chamber 72 is maximized in size and is filled with fresh fuel-air mixture 30. The scavenge passages 86 are closed. The lower chamber 62 is minimized in size and is filled with compressed fuel-air mixture 30.
Just prior to this point, the igniter 92 fires, exploding the compressed fuel-air mixture 30 within the lower chamber 62, and thereby driving the piston 13 downwardly.
As the piston 13 proceeds downwardly, the inertial valve 74 remains closed. The upper chamber 70 expands, drawing fresh fuel-air mixture 30 into the upper chamber 70. The intermediate chamber 72 contracts and the fresh fuel-air mixture 30 within the intermediate chamber 72 becomes compressed. The lower chamber 62 is expanding and is filled with exhaust.
As the piston 13 further continues downwardly, the exhaust port 28 opens the scavenge passages 86 open and the fresh fuel-air mixture 30 within the intermediate chamber 72 is pressured into the upper portion of the lower chamber 62. The flow of the fresh fuel-air mixture 30 from the intermediate chamber 72 into the upper portion of the lower chamber 62 pressurizes exhaust within the lower chamber 62 downwardly.
Thereafter, some of the scavenge passages 86 are closed as the piston 13 nears its lowest point. After the piston 13 reaches its lowest point, a new piston cycle begins.
As noted above, the apparatus 10 can be also be effectively used in a pump 12. Many different pump 12 configurations are possible.
An upper chamber intake valve 124 is provided for allowing fluids into the upper chamber 70 through the upper portion intake port 116 during the downward cycle of the piston 13, and for preventing fluids from flowing out of the upper chamber 70 through the upper portion intake port 116 during the upward cycle of the piston 13.
An intermediate chamber intake valve 126 is provided for allowing fluids into the intermediate chamber 72 through the intermediate portion intake port 120 during the upward cycle of the piston 13 and for preventing fluids from flowing out of the intermediate chamber 72 through the intermediate portion intake port 120 during the downward cycle of the piston.
A lower chamber intake valve 128 is provided for allowing fluids into the lower chamber 62 through the intermediate portion intake port 120 during the downward cycle of the piston 13 and for preventing fluids from flowing out of the lower chamber 62 through the intermediate portion intake port 120 during the upward cycle of the piston 13.
An upper chamber discharge valve 130 is provided for allowing fluids to flow out of the upper chamber 70 through the upper portion discharge port 118 during the upward cycle of the piston 13 and for preventing fluids from flowing into the upper chamber 70 through the upper portion discharge port 118 during the downward cycle of the piston 13.
An intermediate chamber discharge valve 132 is provided for allowing fluids to flow out of the intermediate chamber 72 through the intermediate portion discharge port 122 during the downward cycle of the piston 13 and for preventing fluids from flowing into the intermediate chamber 72 through the intermediate portion discharge port 122 during the upward cycle of the piston 13.
Finally, a lower chamber discharge valve 134 is provided for allowing fluids to flow out of the lower chamber 62 through the intermediate portion discharge port 122 during the upward cycle of the piston 13 and flow preventing fluids from flowing into the lower chamber 62 through the intermediate portion discharge port 122 during the downward cycle of the piston 13.
The upper portion of the piston cylinder 14 defines an upper portion intake port 116 and an upper portion discharge port 118. The lower portion 18 of the piston cylinder 14 defines an exhaust port 28 (not shown in
An upper chamber intake valve 124 is provided for allowing fluids into the upper chamber 70 through the upper portion intake port 116 during the downward cycle of the piston 13 and for preventing fluids from flowing out of the upper chamber 70 through the upper portion intake port 116 during the upward cycle of the piston 13.
An upper chamber discharge valve 130 is provided for allowing fluids to flow out of the upper chamber 70 through the upper chamber discharge port 118 during the upward cycle of the piston 13 and for preventing fluids from flowing into the upper chamber 70 through the upper portion discharge port 118 during the downward cycle of the piston 13.
A valve 74 is provided for alternatively allowing the transfer of fluids into the intermediate chamber 72 and for alternatively preventing the transfer of fluids from the intermediate chamber 72. In the embodiment illustrated in
Means 76 are also provided for alternatively allowing the transfer of fluids between the intermediate chamber 72 and the lower chamber 62 and for alternatively preventing the transfer of fluids between the intermediate chamber 72 and the lower chamber 62. In the embodiment illustrated in
Finally, an igniter 92 is provided proximate to the lower chamber 62 for igniting fluids within the lower chamber 62.
As illustrated in
The basic apparatus 10 provides an inexpensive, efficient and effective way of solving the prior art problem with two-stroke cycle engines of the intake fuel-air mixture follow the exhaust out of the exhaust port. In the invention, this problem is solved by introducing the fuel-air mixture at the top of the combustion chamber. In this way, the mixture must travel down the cylinder filling the combustion chamber prior to reaching the exhaust port. By controlling the amount of mixture inducted, the piston will be in upward motion, closing the exhaust port before any mixture escapes.
The basic apparatus 10 also provides a simple, efficient and inexpensive way of solving the problem with prior art two-stroke cycle engines of lubricating oil passing to the exhaust port. In the invention, this problem is solved by a quadrant system of rings and seals and locating the exhaust port on the non-thrust quadrant. The long seals in the cylinder isolate the quadrants and the rings limit the oil to the non-thrust quadrants. This is not detrimental to engine operation as piston load on these quadrants is minimal.
The basic apparatus 10 also provides a simple, efficient and inexpensive solution to the problem in prior art two-stroke cycle engines of bringing intake fuel-air mixture from the bottom of the engine to the top of the cylinder where the igniter is located. In the invention, this problem is solved by a scavenge chamber of higher pressure capability delivering intake mixture directly to the top of the combustion chamber. Shaping and directing the delivery passages will ensure combustible mixture at the igniter even at very small throttle openings.
The basic apparatus 10 also provides a simple, efficient and inexpensive solution to the problem in prior art two-stroke cycle engines of the difficulty of lubricating the cylinder walls. In the invention, this problem is solved by continuous oil supply to the thrust quadrants. These quadrants are not exposed to the heat of combustion, as the piston uprights cover these quadrants during engine operation. There are no port openings in these quadrants, so oil may flow freely upward between the cylinder wall and piston.
The apparatus 10 also provides a simple, efficient and inexpensive solution to the problem in prior art two-stroke cycle engines of the use of the crank case as the delivery pump for the scavenge charge. In the invention, this problem is solved by the intermediate chamber. This chamber delivers intake mixture directly to the combustion chamber with potential pressures many times greater than a crank case pump. Additionally, this leaves the crank case available to serve as an oil sump, avoids the mixing of oil with the fuel and permits the use of inexpensive plain bearings.
As noted above,
In the present invention, the upper chamber 70 is connected with the lower chamber 62 by a tube 136. This tube 136 is valved at both ends. At the upper end of the tube 136 is an upper tube valve 138. The upper tube valve 138 is typically a one-way valve, so that, when the upper tube valve 138 is open, gases in the upper chamber 70 can flow into the tube 136 but cannot flow from the tube 136 into the upper chamber. At the lower end of the tube 136 is a lower tube valve 140. The lower tube valve 140 is also typically a one-way valve, so that, when the lower tube valve 140 is opened, gases within the tube 136 can flow into the lower chamber 62 but cannot flow from the lower chamber 62 into the tube 136. The upper tube valve 138 and the lower tube valve 140 may be controlled in numerous ways, such as by mechanical means, electrical means, differential pressure means or by some combination thereof.
The upper chamber 70 further comprises a first intake port 116a defined in the piston cylinder upper portion 16. The flow of fluids into the upper chamber 70 through the first intake port 116a is controlled by a first upper chamber intake valve 124a. The intermediate chamber 72 further comprises a second intake port 116b defined in the piston cylinder upper portion 16. The flow of fluids into the intermediate chamber 72 through the second intake port 116b is controlled by a second upper chamber intake valve 124b. Typically, the fluid available to the intermediate chamber 72 via the second intake port 116b is air only, whereas fluids available to the upper chamber 70 via the first intake port 116a can either be air (alone) or an air/fuel mixture.
Fuel to the apparatus 10 can be provided at any of several different locations. The preferred location in each case will depend upon a cost/emissions analysis. Typically, fuel is injected into the upper chamber 70 via the first intake port 116a or to the upper portion of the tube 136. An inexpensive two-stroke cycle engine employing the apparatus 10 of the invention (such as a lawn mower), can employ a carburetor whose air/fuel output is provided to the upper chamber 70 via the first intake port 116a.
Table One is a summary of the approximate relative timing of the functioning of the valving and porting of the various chambers to one another during piston motion expressed in degrees of crankshaft rotation.
On the piston downstroke (as illustrated in
When the exhaust port 28 and the scavenge passages 86 close or are closing (as illustrated in
On further piston upstroke (as illustrated in
An advantage to the invention is that some air may escape through the exhaust port 28 but no fuel will escape through the exhaust port 28, as the fuel/air mixture does not enter the lower chamber 62 until the exhaust port 28 is closed. Thus, use of the invention will greatly improve emissions. In most prior art systems, the air enters from the bottom of the combustion chamber, requiring most of the cylinder to fill with air to clear the area approximate to the igniter of exhaust, even when the engine is at part throttle (e.g. idling). Excess air causes higher emissions of nitrous oxides. In the invention, the intermediate chamber 72 can be throttled such that only the needed amount of fresh air to clear the area proximate to the ignitor 92 need be admitted. This lowers nitrous oxide emissions. What remains in the lower chamber 62 distant from the igniter 92 will be inert exhaust gases. This will help prevent knock, as the flame front burns toward what is commonly called the end gas. (Inert gases will not explode or knock, under the increasing pressure.)
Contrary to conventional two-stroke engines which use the crankcase as a pump, the design of the invention uses the upper and intermediate chambers 70 and 72, allowing a less costly and more durable crankcase wet-sump lubricating system.
Also, prior art two-stroke cycle engines often require ancillary pumps for air or fuel injection, whereas the system of the invention uses only the piston 13.
Because the present invention allows supercharging without the need of an ancillary pump, use of the present invention allows power output from a smaller and less costly engine.
Overall efficiency is also increased in the invention in that mechanical friction is a smaller percentage of total power.
TDC - Top Dead Center
BDC - Bottom Dead Center
ATDC - After TDC
BTDC - Before TDC
EO - Exhaust Open
SO - Scavenge Open
inj. - injection
Having thus described the invention, it should be apparent that numerous structural modifications and adaptations may be resorted to without departing from the scope and fair meaning of the instant invention as set forth hereinabove.
The present application is a continuation-in-part of U.S. patent application Ser. No. 10/804,351 filed Mar. 17, 2004 entitled “Apparatus with Piston Having Upper Piston Extensions”; the contents of which are incorporated in this disclosure by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10804351 | Mar 2004 | US |
| Child | 11208218 | Aug 2005 | US |
