NL2011947C2

NL2011947C2 - Combustion engine comprising a cylinder.

Info

Publication number: NL2011947C2
Application number: NL2011947A
Authority: NL
Inventors: Sander Wallené
Original assignee: Twostroke Motorcycle Company
Priority date: 2013-12-12
Filing date: 2013-12-12
Publication date: 2015-06-15
Also published as: WO2015088347A1

Abstract

The present invention is in the field of a combustion engine comprising a two stroke cylinder (6), to an injector spark assembly (1) for use in such a combustion engine, to a method of operating said engine, and to a method of operating said injector spark assembly (1). In the internal combustion engine combustion of a fuel, such as fossil fuel, occurs with air in a combustion chamber (24).

Description

Combustion engine comprising a cylinder

FIELD OF THE INVENTION

The present invention is in the field of a combustion engine comprising a two· stroke cylinder, to an injector spark assembly for use in such a combustion engine, to a method of operating said engine, and to a method of operating said injector spark assembly.

BACKGROUND OF THE INVENTION

The present invention is in the field of an internal combustion engine wherein combustion of a fuel, such as fossil fuel, occurs with air in a combustion chamber. The chamber is an integral part of a working fluid flow circuit. The combustion engine produces an expansion of high-temperature and high-pressure gases. These gasses apply a direct force to a further component of the engine. The force is applied typically to pistons, turbine blades, or a nozzle. This force moves the component over a distance, transforming chemical (combustion) energy into mechanical energy. The term internal combustion engine usually refers to an engine in which combustion is intermittent, that is during limited periods, between which periods no combustion takes place. Examples relate to four-stroke and two-stroke piston engines. Further less used variants relate to a six-stroke piston engine and a Wankel rotary engine.

Engines based on the two-stroke cycle use two strokes (one up, one down) for every power stroke. Spark-ignition two-strokes are small and light for their power output and mechanically very simple. Two stroke engines are generally less efficient and more polluting than their four-stroke counterparts; these two-stroke engines typically do not meet standards as Euro 5 (European Directive· 99/96/EC). The two-stroke engines typically have a large amount of oil in exhaust gasses. Efficiency is typically hampered by escape of fuel through exhaust ports. In terms of power per cm3, a two-stroke engine produces comparable power to an equivalent four-stroke engine. It may be possible for a two-stroke to produce more power than an equivalent four-stroke, over a narrow range of engine speeds, at the expense of less power at other speeds. Two-stroke engines are mostly used at low engine speeds (100-500 rotations (or revolutions) per minute), such as in ships. A typical combustion engine comprises a cylinder wall, the wall forming a main part of a combustion chamber, a piston movable arranged in the cylinder, a crankcase, a crankshaft arranged in the crankcase, and a piston rod connecting the crankshaft with the piston.

Developments of engines go back a long time. One such development relates to a two stroke engine having a moveable cylinder wall (GB133232 A). The wall is moved downward by a spring, and upwards by a cam; such is complex. The cylinder wall comprises openings, which are bound to wear. The cylinder wall is not very efficient in terms of energy consumption and power output. Also (absence of) sealing of the engine seems critical. The cylinder is further limited to rather low engine speeds (< 500 rpm).

Further developments relate to diesel engines having sleeve valves. Such engines are typically heavy weight engines, to be operated at low engine speeds (< 500 rpm).

The present invention therefore relates to a combustion engine comprising a two stroke cylinder, which solve one or more of the above problems and drawbacks of the prior art, providing reliable results, without jeopardizing functionality and advantages.

SUMMARY OF THE INVENTION

The present invention relates to a combustion engine comprising a two stroke cylinder according to claim 1, an injector spark assembly for use in such a combustion engine according to claim 13, to a method of operating said engine according to claim 16, and to a method of operating said injector spark assembly according to claim 17.

For generic understanding of the present invention and details thereof also reference is made to PCT/EP2012/061025, which relates to an earlier invention of the present inventor, partly relating to the present combustion engine, which document is incorporate by reference in its entirety. In view of the subject matter of this patent application major improvements have been achieved by the present invention. The two stroke engine of the '025 is not well balanced in terms of forces, and therefore does not function well. The present two stroke engine is easier to manufacture, easier to install, easier to maintain and simpler of design. In view of design for instance no means for limiting space/tolerance is needed. Also the present design has less wear. In view of the cam restrictions to the crankshaft are less severe or absent; as a result the crankshaft can be lighter. Also temperature of the engine is better controlled. And efficiency of the present engine is much better.

The present invention relates to an improved design of a two stroke engine, which is to be certified under Euro 5 (99/96/EC) and possible Euro 6 norms. Such relates to extremely "green" and efficient technology. The efficiency is even further improved by specific and dedicated design of various components, such as cylinder walls and injection spark assembly. The present invention reduces fuel consumption by 5-10% and it allows for relatively lean mixtures to be used (such as λ e [1;1,5]) without loss of power. The improved design further limits wear of parts. The design also allows for relatively high engine speeds, such as up to 12500 rpm. Also friction is reduced. In an example the present engine has an improved cooling and/or an advanced air inlet.

For better understanding the term "up" (or "upper") relates to a position where a top of a piston is located when the chamber is having its smallest volume. Likewise the term "low" relates to the piston being located when the chamber is having its largest volume.

The first upper moveable cylinder wall (umcw) has a restricted movement, which movement is restricted downwards by a means such as a bulge or fixed stop, and upwards by a top of the cylinder wall. Height dimensions are found to be not very critical, as long as the first moveable wall does not block.an air inlet (38) and an exhaust gas outlet (36). The umcw supports initial movement of the lower moveable cylinder wall, thereby also relieving load on the cam (s)/camshaft (s).

The second lower moveable cylinder wall (lmcw)(7), is designed and dimensioned for opening and closing air inlet opening (s) and exhaust gas opening(s). In a first position of the lmcw the air inlet opening(s) and exhaust gas opening(s) are blocked, hence closed, and in a second position of the lmcw the air inlet opening(s) and exhaust gas opening(s) are free, hence opened.

The present lmcw and umcw separate parts of the engine having lubrication and the internal combustion chamber. Thereby pollution of the environment is prevented. The present engine reduces wear and deformation of piston rings. The present invention in an example provides piston ring(s) and (oil) scraper (ring(s) that are provided in the moveable cylinder wall; they do not wear, e.g. as they do not encounter openings (or ports).

An inner and outer diameter of the lmcw and umcw are preferably substantially the same. The outer diameter is equal to an inner diameter of the cylinder, minus a minimal amount for allowing movement of the moveable cylinder walls. The inner dimension is equal to an outer dimension of the piston, plus a minimal amount for allowing movement of the piston. The minimal amount is in an example 0.001-0.005 mm.

The lmcw is moved up and down by an actuator, wherein the actuator is in phase with engine operation, i.e. two-stroke revolution thereof. In an example the actuator is a tumbler.

Thereby the present invention provides a solution to one or mpre of the above mentioned problems and drawbacks.

Advantages of the present description are detailed throughout the description.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in a first aspect to a combustion engine comprising a two stroke cylinder according to claim 1.

In an example of the present combustion engine the cylinder has a volume of 10-1500 cc, preferably from 25-1200 cc, more preferably from 50-1000 cc, even more preferably from 100-750 cc, such as from 250-500 cc. It is noted that an effective volume of a cylinder is somewhat smaller, as the present umcw and lmcw are provided. Therewith the present invention provides as a further advantage a higher cylinder volume during scavenging and a higher compression to be applied. Such provides higher efficiencies. The present invention is suited for light weight applications. Such engines can be used in motorcycles, karts, cross-motors, in cars, jet skis, snow scooters, handheld equipment, such as in motor saws, lawn mowers, forest mowers, and outboard motors. Such engines are also suited if maintenance should be simple and limited. In principle the present technology is also applicable to other internal combustion engines, such as four-stroke motors.

In an example of the present combustion engine the first and/or second moveable cylinder wall are hollow. It has been found that in terms of revolutions to be obtained, especially higher rpms, it is an advantage to make the umcw and lmcw hollow. A thickness of a wall can be limited to 1-3 mm. In this respect it is noted that producing a hollow cylinder wall is considered too complex for applications typically considered.

It is preferred that the inner diameter and outer diameter of the first and second moveable wall, respectively, are the same.

In an example of the present combustion engine the first and/or second moveable cylinder wall have a width of 2-25% of an outer diameter of the moveable wall, preferably 5-15%, more preferably 8-12%, such as 9-10%. Choosing a width is considered not trivial. Especially an lmcw is found to operate more efficient at lesser wear if a weight thereof' is relatively small.

On the other hand a surface area of a top section of the lmcw, in combination with a surface area of a bottom section of the umcw have been found to influence fuel consumption, if chosen appropriately in a positive way. It is considered that when the lmcw approaches the umcw, in its upward movement, an "air gap" between the two becomes smaller and smaller; at a certain point, when the umcw and lmcw almost collide with one and another, air is moved inwards into the cylinder, thereby contributing to mixing fuel and air intimately significantly. Even further, it is considered that the air gap provides a natural damping means, therewith minimizing an effect of collision; wear of umcw and lmcw is thereby limited substantially. In view of weight the width is preferably as small as possible, in view of "air gap" the width is preferably as large as possible. It has been found that optimal results are obtained of the preferred ranges.

In an example of the present combustion engine the first and/or second moveable cylinder wall have a reinforcement element in the hollow wall. Despite introducing some extra weight to the umcw and lmcw, respectively, a width thereof can be made somewhat larger and walls can be made somewhat thinner (see also the previous section).

In an example the present combustion engine further comprises at least one means for pushing down the first moveable wall (3), such as a spring. It has been found that sometimes a gap between the umcw and lmcw is not fully closed. Such may- involve introduction of unwanted lubricant (oil) into the combustion chamber. In order to further secure sealing a means for pushing the umcw down is provided, such as a spring.

In an example the present combustion engine further comprises at least one cam (8,11), preferably two cams, and a camshaft (9,10), for restricting movement of the actuator. In order to reduce movement of the actuator, to reduce wear thereof, to improve efficiency of the combustion engine (as a whole) one or more cams are provided. The cams further support revolutions of the engine.

In an example cams can be repositioned during revolution of the engine, therewith changing a period of e.g. exhaust. Also a timing of a bellow (see below) may be tuned. A cylinder may be filled more efficient. As a result thereof an engine can be operated more optimal in all ranges of rpm's, and under various loads .

In an example of the present combustion engine the at least one cam (8) has a bulge (), wherein the bulge is for upward movement of the second moveable cylinder wall such that the second moveable cylinder wall firmly presses the first moveable cylinder wall upwards. Such a bulge helps to overcome a "dead" position of the lmcw. As such efficiency is improved.

In an example the present combustion engine further comprises an energy absorber (55), wherein the energy absorber is for providing energy to the actuator for moving the actuator over a dead point and for absorbing energy when the actuator is in an active position, wherein the actuator preferably has a cam (54) for energy transfer between the absorber and actuator. The present cam (54) fits extremely well within the present engine. Such an energy absorber helps to overcome a "dead" position of the lmcw. As such efficiency is improved.

In an example of the present combustion engine the actuator is directly or indirectly in contact with the crankshaft.

As such motion of the actuator, and thereby motion of the lmcw, and operation of the engine and cylinder, are synchronized.

In an example the present combustion engine further comprises a bellows (44,45,46) and a valve (49) for opening and closing the crankcase (20), wherein the bellows is for providing air flow to the combustion chamber and for cooling the crankcase. Therewith a thermal load of the crankcase is limited to acceptable levels. Also lubrication of moving parts is not jeopardized (in comparison to prior art solutions). The bellow further provides compression to the combustion chamber, thereby improving efficiency and power output.

In an example the present combustion engine further comprises an injector spark assembly (1), wherein a spark plug comprises a first central electrode and a second mass electrode, wherein the second mass electrode comprises a rotating part for improved ignition, wherein the rotating part is in a first position in front of the injector and in a second position in front of the central electrode. It has been found that rather large amounts of fuel are typically lost in prior art combustion engines, due to (superfluous) wetting of a spark assembly with fuel. The superfluous wetting is typically required in order to secure sparking (and combustion of the fuel), especially under lean burn conditions. The wetting also consumes extra time, thereby limiting efficient use of the combustion engine. By providing the present injector spark assembly injection can be limited with about 0.2-1.5 msec per revolution, which attributes to a reduction in fuel consumption of 5-10%.

As a result also much leaner fuel mixtures may be used.

In a second aspect the present invention relates to an injector spark assembly (1) for use in a combustion engine, wherein a spark plug comprises a first central electrode and a second mass electrode, wherein the second mass electrode comprises a rotating part for improved ignition, wherein the rotating part is in a .first position in front of the injector and in a second position in front of the central electrode.

In an example of the present assembly the rotating part is a section of a disc, preferably a section of 10-40 degrees, such as 20-30 degrees. By carefully designing the rotating part fuel consumption is optimized (limited) whereas sparking is secured. It has been found that a relatively small section is sufficient for the purpose intended.

In an example of the present assembly the rotating part comprises a counter weight, wherein the counter weight is of equal weight as the section of the disc. It has been found that an imbalance may be introduced into the engine, which imbalance causes extra noise, wear and fuel consumption. In order to im- prove the assembly a counter weight is provided.

In a third aspect the present invention relates to a method of operating an assembly according to the invention, wherein the injector provides fuel in a period which period is reduced by 0.2-1.5 msec per revolution. An injection time may vary depending on e.g. rotations per minute, temperature, load, amount of gas provided, volume of an engine, etc. However, in all cases the period can be made shorter with the present assembly. Details hereof are provided above and below.

In a fourth aspect the present invention relates to a method of operating a combustion engine according to the invention, wherein a lean mixture is provided to the combustion chamber. Details hereof are provided above and below.

The one or more of the above examples and embodiments and the (elements of) the figures may be combined, falling within the scope of the invention.

EXAMPLES

The invention is further detailed by the accompanying figures, which are exemplary and explanatory of nature and are not limiting the scope of the invention. To the person skilled in the art it may be clear that many variants, being obvious or not, may be conceivable falling within the scope of protection, defined by the present claims.

FIGURES

The invention although described in detailed explanatory context may be best understood in conjunction with the accompanying figures.

Figs. A1-A2 show details of a piston.

Figs. B1-B2 show details of a piston and lmcw and umcw, respectively.

Figs. C1-C2 show details of a piston. Fi Figs. DB1A, DB1B and DB2 show details.

Figs. D13A and D13B show an injector spark assembly. DETAILED DESCRIPTION OF THE FIGURES List of elements: 1: spark plug 2: cylinder head 3: Push spring for umcw 4: Piston 5: Upper moveable cylinder wall (umcw) 6: Cylinder 7: Lower moveable cylinder wall (lmcw) 8: Upper cam 9: Camshaft holder 10: Camshaft 11: Lower cam 12: Carter lid 13: Cam shaft gears 14: Seal 15: Dynamo/ignition 16: Oil pan/dry sump 17: Lower block of carter 18: Seal 19: Bearing (ball-bearing) 20: Crankshaft 21: lmcw-arm 22: B-port (inlet) 23: Cooling channel 24: Combustion chamber 25: Second piston ring recess 26: Connecting rod 27: O-ring recess 28: O-ring recess 29: Oil scraper ring recess 30: O-ring recess 31: Upper piston ring recess 32: Seal 33: Oil scraper ring recess lmcw 34: A-port (inlet) 35: C-port (inlet) 36: Main exhaust port (exhaust) 37: Auxiliary exhaust port (exhaust) 38: Boost port (inlet) 39: Rotation point bellows arm 40: Inlet membrane 41: Throttle valve/slide 42: Rotation point lmcw arm 43: Throttle body/housing 44: Bellow arm 45: Bellow plate 46: Bellow 47: Exhaust carter cooling 48: Crankshaft bellow 49: Carter cooling membrane 50: Drive chain/belt cam shafts 51: Oil pump 52: Inlet carter cooling 53: Drive chain/belt bellow 54: Cam support spring lmcw 55: Support spring lmcw 56: Adjusting nut support spring lmcw 57: Tolerance umcw 58: Combustion pressure 59: Air cushion 60: Movement limiter (bulge) A: Electrode B: Injector C: Rotating mass electrode D: Injector/spark assembly E: Inner core (moveable) F: Bore G: Dome area H: Cylinder Head I: Counter weight

Fig. A1 shows a front view of a piston in its upper dead point. Fig. Ά2 shows a side view of a piston in its upper dead point. If the piston (4) is in the tdc (top dead center) position, then the lmcw (7 lower moveable cylinder wall) and umcw (5 upper moveable cylinder wall) are closed and at rest. The lmcw is lightly pressed against the umcw via the lmcw arm (21) by means of the two cam shafts (8,11), with sufficient pressure for proper sealing. The bellows (45,46) will then be on their lowest setting. On the inlet side an air/mixture is then completely sucked. Such needs not to be in symmetrical operation with the crank angle; an asymmetrical setting is in fact possible. The crankcase side of the bellows is about to suck crankcase air through the crankcase cooling membrane (49). This crankcase air will flow through a cooler back into the crankcase via the crankcase inlet channel (52). This will prevent that the piston bottom is too heavy loaded thermally (overheated). Because the lmcw keeps the inlet ports (22,34,35,38) and the outlet ports (36,37) closed, all of the moving parts under the piston may be lubricated, without lubricating oil entering into the combustion chamber (24).

The cylinder head can also be equipped with a direct injection system and a by inventor developed lean burn direct injection assembly as shown in drawing D13A and DI3B. Also, the cylinder head can be equipped with a variable compression system.

The cams (8,11) are driven by a belt or a chain (50) via gear wheels (13). The cams run 1 to 1 along with the crankshaft (20). The present two-stroke engine runs in this way as a symmetrical two-stroke engine. By applying, camshaft adjustment, it is also possible to have the scavenging periods (inlet and outlet duration) proceed asymmetrically.

The lmcw (7) is sealed by one or more sealing rings in a groove in the cylinder (33). The umcw (5) is sealed by various sealing rings (27,28,30). The lmcw-arm (21) pivots about a fixed point (42).

Fig. B1 shows a front view of a piston when moveable cylinder walls are opened or closed.

Fig. B2 shows a side view of a piston when moveable cylinder walls are opened or closed.

After ignition by means of the spark plug (1), the piston (4) will move to the position as shown in the figures, Bl and B2. Even before the top of the piston (4) approaches the upper surface of the lmcw (7), the cam shafts (8,11) will press up the lmcw against the spring pressure (3) of the umcw (5). This is intended to give more tension and bring the lmcw up to speed. When the top of the piston approaches the top of the lmcw, the cams will allow the lmcw to follow the piston. At the moment the umcw hits its fixed stop, the combustion pressure above the piston supports to move the lmcw downwards (see detail DB1A showing a representation of combustion pressure which supports the umcw when accelerating downwards and DBl showing a representation of an air cushion during closure, which cushion supports damping). This occurs for a short period just before the opening of the outlet ports (36,37). The bellow (45,46) is in the meantime pressurizing the air/mixture for the intake cycle. The inlet side of the bellow is connected to the cylinder (6) via the scavenging ports/inlet channels (22,34,35,38). On the crankcase side of the bellow the meantime heated carter air is sucked through the crankcase cooling membrane (49) and cooled crankcase air flows through the crankcase inlet (52) into the crankcase. The piston and lmcw open after this point the exhaust ports and a moment later the inlet ports. The present cylinder then scavenges as a classical two-stroke engine.

Fig. Cl shows a front view of a piston in its bottom dead centre . , Fig. C2 shows a side view of a piston in its bottom dead centre .

Just before the piston and the lmcw reach the bdc (bottom dead center), the cam (54) runs at a back end of the lmcw-arm (21) against an auxiliary spring (55). The spring is adjustable with an adjustable nut (56). The spring supports an initial movement of the lmcw from the Idp back on track in an upward movement. The inlet ports (22,34,35,38) are now fully open. Because the lmcw moves along with the piston, during the scavenging period the cylinder volume is a temporary larger. So the cylinder can be scavenged more easily. Indeed, there is less resistance to a returning pulse from a to be used expansion ex-haust/or the outlet baffles. By movement of the piston with piston rings in the lmcw through the cylinder the piston rings, and in this case also an oil- scraper ring, do not touch the inlet and outlet ports. As a result, piston rings wear is much less than with a conventional two-stroke engine.

In the meantime, the bellows has reached its highest point. Figures Bl and B2

After scavenging, the piston will return to a position as shown in the figures Bl and B2. The lmcw (7) will in first instance be damped by the air cushion (59) between lmcw and umcw (5) (see detail drawing DB1). Thereafter, the lmcw will make contact with the umcw and slightly press it. The cylinder is now completely closed again. Then, the piston will compress the mixture/air for the next power stroke (see figure A1 and A2).

Claims

A combustion engine comprising a cylinder (6) for use at 800 rpm-15000 rpm, the cylinder comprising: a) a first cylinder wall, the first wall forming a main part of a combustion chamber, b) a piston (4) movably arranged in the cylinder, c) a crankcase (20), d) a crankshaft (20) mounted in the crankcase, e) a piston rod (26) connecting the crankshaft to the piston, characterized by f) a first upper movable cylinder wall (5) wherein the first movable wall does not block an air inlet (38) and a flue gas outlet (36), the first movable wall having a means for limiting movement (60), such as an outward bulge, h) a second lower movable cylinder wall (7), said second movable cylinder wall for opening and closing the air inlet opening (s) and exhaust gas opening (s), and i) an actuator (21) for moving the second movable cylinder wall, such as a tumbler.

The engine of claim 1, wherein the cylinder has a volume of 10-1500 cc, preferably of 25-1200 cc, more preferably of 50-1000 cc, even more preferably of 100-750 cc, such as of 250-500 cc.

Engine according to any one of the preceding claims, wherein the first and / or second movable cylinder wall are hollow and / or wherein the inner diameter and the outer diameter of the first and second movable wall, respectively, are the same.

Engine as claimed in any of the foregoing claims, wherein in the first and / or second movable cylinder wall have a width of 2-25% of an outer diameter of the movable wall, preferably 5-15%, more preferably 8-12%, such as 9-10%.

5. Engine according to any of claims 3-5, wherein the first and / or second movable cylinder wall has / have a reinforcement element in the hollow wall.

The motor of any one of the preceding claims, further comprising at least one means for pushing down the first movable wall (3), such as a spring.

Motor according to one of the preceding claims, further comprising at least one cam (8,11), preferably two cams, and a camshaft (9,10), for movement limitation of the actuator.

The engine of claim 7, wherein at least one cam (8) has a protrusion, the protrusion for upward movement of the second movable cylinder wall being such that the second movable cylinder wall firmly pushes the first movable cylinder wall up.

The motor of any one of the preceding claims, further comprising an energy absorber (55), wherein the energy absorber is for supplying energy to the actuator to move the actuator over a dead point and for absorbing energy when the actuator is in an active position, the actuator preferably having a cam (54) for energy transfer between the energy absorber and the actuator.

Engine according to one of the preceding claims, wherein the actuator is in direct or indirect contact with the crankshaft.

The engine of any one of the preceding claims, further comprising a bellows (44,45,46) and a valve (49) for opening and closing the crankcase (20), the bellows serving to provide air flow to the combustion room and for cooling the crankcase.

The engine of any one of the preceding claims, further comprising an injector spark assembly (1), wherein the spark plug comprises a first central electrode and a second ground electrode, the second ground electrode comprising a rotating member for improved ignition, wherein the rotating member is in a first position for the injector and is in a second position for the central electrode.

An injector spark assembly (1) for use in an internal combustion engine, the spark plug comprising a first central electrode (A) and a second ground electrode (C), the second ground electrode comprising a rotating member for improving the ignition wherein the rotating part is in a first position for the injector and in a second position for the central electrode.

The assembly of claim 13, wherein the rotating member is a portion of a disc, preferably a disc portion of 10-40 degrees, such as 20-30 degrees.

Assembly according to claim 13 or 14, wherein the rotating part comprises a counterweight (I), wherein the counterweight is of the same weight as the portion of the disc.

A method of operating the assembly of any one of claims 13-15, wherein the injector provides fuel for a period of time, the period being shortened by 0.2-1.5 msec

A method of operating a combustion engine according to any of claims 1-12, wherein a lean mixture is supplied to the combustion chamber.