Patent ID: 12253047

An internal combustion engine according to the present invention comprises a plurality of cylinders of which one exemplary cylinder1is depicted inFIG.1A to1D. The cylinder1comprises a cylinder wall15defining a combustion chamber3, which is enclosed by said cylinder wall15.

A piston2is received inside the combustion chamber3of the cylinder1. During operation of the internal combustion engine, the piston2performs a reciprocating motion in the combustion chamber3away from and towards a crankshaft22in a crankcase21situated beneath the cylinder1, as may be discerned fromFIG.3.

The cylinder1comprises at its top end an inlet channel9for the introduction of a fuel-oxidiser mixture into the combustion chamber3and an exhaust outlet10for guiding exhaust gasses out of the combustion chamber3after combustion. The inlet channel9and the exhaust outlet10respectively comprise valves14and14′ for selectively closing and opening the inlet channel9and exhaust outlet10during successive engine strokes. A spark plug13is provided to ignite the fuel mixture within combustion chamber3for powering of the internal combustion engine.

During operation of the internal combustion engine, the cylinder1continuously performs one of a number of successive engine strokes, during which piston2undergoes an upward or downward motion within the combustion chamber3of the cylinder1. An operational cycle of the internal combustion engine consists of an intake stroke, followed by a compression stroke, a combustion stroke and finally an exhaust stroke.

In the appended figures,FIG.1Adepicts the piston2undergoing a downward motion towards a crankcase during an intake stroke with the valve14in an opened state for the introduction of the fuel-oxidiser mixture. The piston2undergoes a downward motion within cylinder1. The fuel-oxidiser mixture is introduced into the combustion chamber3via the inlet channel9with valve14being kept open and valve14′ remaining closed. Once the piston2reaches a predefined lowest point within the interior of cylinder1, valve14is closed to inhibit any further introduction of the fuel-oxidiser mixture.

The intake stroke of cylinder1is followed by a compression stroke as depicted inFIG.1B. During this intake stroke, both of valves14and14′ remain closed and the piston2undergoes an upward motion within the interior of cylinder1. The internal volume of the combustion chamber3is thus reduced, thereby compressing the fuel-oxidiser mixture located therein. When the piston2has reached a predefined highest point within the interior of cylinder1—at which point the combustion chamber3comprises its smallest volume—the compressed fuel-oxidiser mixture is brought to ignition by means of the spark plug13.

The compression stroke is followed by a combustion stroke upon, as illustrated inFIG.1C. During the combustion stroke, the fuel-oxidiser mixture within combustion chamber3combusts and the resulting rapidly expanding combustion gasses force the piston2in the downward direction, thereby powering the internal combustion engine. The piston2continues to travel downward within cylinder1until the aforementioned predefined lowest point within the interior of cylinder1is once again reached.

Lastly, during a subsequent exhaust stroke as is depicted inFIG.1D, the valve14of the inlet channel9is kept closed while—in contrast toFIG.1B—the valve14′ of the exhaust outlet10is opened. The piston2again moves upward within the interior of the cylinder1while forcing combustion gasses present within combustion chamber3outward via the exhaust outlet10. Once the piston2has again reached the aforementioned predefined highest point within the interior of cylinder1, the exhaust stroke is complete. The valve14′ of the exhaust outlet10may then be closed and the valve14of the inlet channel9opened, after which the piston2may perform a further intake stroke as described here above, to subsequently repeat the entire operating cycle of the internal combustion engine.

To enable the above described operation of the internal combustion engine, lubricating oil is provided to reduce mechanical friction between in particular the contacting surfaces of the cylinder1and the piston2. For example, an oil dispensing nozzle (not shown) may be provided to continuously or periodically apply lubricating oil into a lower section of the cylinder1closest to the crank shaft22.

As is depicted inFIG.1A to1D, a plurality of piston rings4,5and6is provided between the piston2and the cylinder wall15. In the depicted embodiments four piston rings4,5and6are provided, but the present disclosure is not limited thereto. As is best illustrated inFIG.2, each of the plurality of piston rings4,5and6may be arranged in one of corresponding grooves4′,5′ and6′ that are disposed on an outer circumference of the piston2.

The plurality of piston rings4,5and6includes compression rings6. The compression rings6are configured and appropriately arranged to seal a gap between the (interior) cylinder wall15of the cylinder1and the piston2, to thereby allow the above described operation of the internal combustion engine. In the depicted embodiment, an exemplary number of two compression rings6are arranged at the top of the piston2and closest to a piston crown7of the piston2.

Moreover, a first scraper ring4defining an oil scraper ring4(also known as an “oil control ring”) is provided between the piston2and the cylinder wall15for regulating the distribution of lubricating oil. The first scraper ring4—which is henceforth referred to as an oil scraper ring4—is configured to assist in distributing lubricating oil over the interior cylinder wall15of the cylinder1during reciprocal motion of the piston2as described here above. Simultaneously, the oil scraper ring4is configured scrape off any excess lubricating oil that may otherwise interfere with the operation of the internal combustion engine. For this purpose, the oil scraper ring4is arranged adjacent to at least one oil drain channel16in the piston2, which may be at least partially formed in the groove4′ into which the oil scraper ring4is arranged. The oil drain channel16may extend around at least part of the circular circumference of the piston2. Moreover, a plurality of oil drain channels16may be provided.

After flowing through drain channel16, excess lubricating oil may fall into an oil sump23within a crankcase21as illustrated inFIG.3. A lubrication system33may moreover be provided, which will be elucidated here below with reference toFIG.3.

According to certain embodiments of the present invention, the oil scraper ring4is configured to scrape off lubricating oil from the cylinder wall15during a downward motion of the piston2towards the crankshaft22housed in a crank case21. That is to say, during intake stroke or a combustion stroke of the internal combustion engine as is depicted inFIGS.1A and1C, respectively. In these figures, the flow of scraped off lubricating oil is indicated by the arrows.

The skilled person is well aware of the requirements with respect to the shape and/or configuration of the oil scraper ring4to achieve scraping off oil from the cylinder wall15during downward motion of the piston2.

As stated in the introductory part of the present disclosure here above, certain fuels or fuel mixtures may result in a relatively large amount of water after being present in combustion chamber3after combustion. In particular natural gas, LPG (propane), renewable fuels such as bioethanol and biodiesel, and hydrogen are known to have a relatively large portion of their combustion products in the form of gaseous water in comparison to petrol and diesel fuel.

A significant portion of this gaseous water will remain in its gaseous state. As such, it is easily driven out of the combustion chamber3during a here above described exhaust stroke of the internal combustion engine. Nevertheless, a portion of this gaseous water will come into contact with the cylinder wall15of the cylinder. Typically, at least part of this cylinder wall15is relatively cold in comparison to the hotter combustion gasses resulting from the combustion of the fuel mixture, in particular when the internal combustion engine has only just been started, has been running for only a short amount of time or when an ambient temperature of the internal combustion engine is particularly low. Consequently, at least some of the gaseous water (water vapour) condensates on the relatively cold cylinder wall15to form liquid water. In the sense of the present disclosure, this liquid water is referred to as condensation fluid forming small droplets or a thin film of fluid on the cylinder wall15. Due to this condensation fluid being in a liquid state, it is not forced out of the combustion chamber3during a subsequent exhaust stroke of the internal combustion engine.

Over the course of several engine cycles, this condensation fluid may accumulate to the point at which it inhibits the above described normal operation cycle of the internal combustion engine. To prevent such problems and remove this condensation fluid from the combustion chamber3, the plurality of piston rings4,5and6moreover comprises at least one second scraper ring5defining a condensation fluid scraper ring5.

The condensation fluid scraper ring5is likewise arranged between the piston2and the cylinder wall15and configured to scrape condensation fluid off from the cylinder wall15during reciprocal movement of the piston2, in particular during an upward stroke of the piston away from the crankshaft22. The condensation fluid scraper ring5may function in a manner that is comparable to that of the oil scraper ring4with respect to the scraping off of lubricating oil from the cylinder wall15.

The condensation fluid scraper ring5may be oriented in a direction opposite to a direction in which the oil scraper ring4is oriented, and in particular may be configured to scrape condensation fluid from the cylinder wall15when moving in a direction within cylinder1opposite a direction in which the oil scraper ring4scrapes oil from the cylinder wall15. More in particular, the condensation fluid scraper ring5may be configured to scrape the condensation fluid off from the cylinder wall15when the piston2moves upwardly away from the crankcase21and the crankshaft22. In other words, the condensation fluid scraper ring5is preferably configured to scrape off condensation fluid from the cylinder wall15during an exhaust stroke and/or a compression stroke of the cylinder1, whereas the oil scraper ring4in contrast is preferably configured to scrape off lubricating oil from the cylinder wall15during an intake stroke and/or combustion stroke of the internal combustion engine. As such, the oil scraper ring4and the condensation fluid scraper ring5are preferably configured to respectively scrape off lubricating oil and condensation fluid when moving in opposing directions.

The oil scraper ring4and the condensation fluid scraper ring5may each comprise a respective shape configured to adequately perform their respective scraping actions in the respective movement directions of the piston2. Alternatively, the oil scraper ring4and the condensation fluid ring5may comprise identical shapes and be oriented in opposing directions relative to one another. According to yet further configurations, the oil scraper ring4and the condensation fluid ring5may be substantially identical, with the oil scraper ring4and the condensation fluid ring5being reliant on the presence of lubricating oil or condensation fluid within the cylinder1to perform their respective functions.

The condensation fluid scraper ring5is preferably arranged closer to a piston crown7of the piston2than the at least one oil scraper ring4. The fluid scraper ring5is moreover preferably arranged between the oil scraper ring4and the at least one compression ring6.

Referring now toFIG.2, the condensation fluid scraper ring5is arranged in an appropriately arranged groove5′. Groove5′ may extend around an outer circumference of the piston2. Adjacent to groove5′ there is arranged a condensation fluid drain channel17extending inwardly from the groove5′ into the piston2. Condensation fluid scraped off from the cylinder wall15by the condensation fluid scraper ring5is drained via condensation fluid drain channel17.

The condensation fluid drain channel17for draining scraped off condensation fluid is distinct from the here above described oil drain channel16, which ensures that the scraped off oil and the scraped of condensation fluid do not mix after these respective fluids have been scraped off the cylinder wall by, respectively, the first (oil) scraper ring4and the second (condensation fluid) scraper ring5.

In the depicted embodiments, the condensation fluid drain channel17debouches into a chamber18defining a hollow interior of the piston2. The chamber18is in turn fluidly connected with a drain channel12extending downwardly out of the piston2. Consequently, condensation fluid scraped off from the cylinder wall15by means of condensation fluid scraper ring5flows out of the cylinder1via fluid drain channel17, chamber18and drain channel12. Problems associated with the presence of condensation fluid within or near the combustion chamber3may thus be obviated or abated. In addition, it is by and large prevented that significant amounts of liquid water end up in the lubricating oil and/or the oil sump23.

It is emphasised here that the embodiments depicted in the appended figures should be interpreted as being merely exemplary and that identical or similar results may be achieved with comparable but alternative configuration of the piston2. For example, while the presence of chamber18comprises the advantages reductions in weight and material, it is conceivable for this chamber18to be omitted and instead be replaced with a more narrow conduit (not shown) directly connecting condensation fluid drain channel17with drain channel12.

FIG.3depicts a schematic partial representation of an internal combustion engine comprising at least the cylinder1with therein the piston2as described with reference toFIG.1A,1BandFIG.2.

As illustrated inFIG.3, the piston2is received in the cylinder1to thereby define the combustion chamber3illustrated in the foregoing figures. The piston2is moreover connected to a crankshaft2arranged within the crankcase21by means of a connecting rod connected to the connection means8of the piston2. The crankcase21moreover comprises the oil sump23that forms part of a lubrication system33of the internal combustion engine.

Still referring toFIG.3, there is provided a connector20that is fluidly connected to the drain channel12described with reference to the foregoing figures. The connector20may moreover comprise a motor for enabling an adequate flow of fluid. Alternatively or in addition, an auxiliary pump24may be provided downstream of the connector20for this purpose. The connector20fluidly connects the drain channel12with a fluid-oil separator26.

As described with reference to the foregoing figures, condensation fluid flows out of the piston2via drain channel12. It has been determined that in practice, it cannot be entirely prevented that this condensation fluid comprises at least some residual lubricating oil.

The mixture of lubricating oil and condensation fluid is fed to the fluid-oil separator26via connector20. The fluid-oil separator26is configured to separate the (residual) lubricating oil from the condensation fluid. According to certain embodiments, this separation may be based at least on part on the immiscibility of the lubricating oil and the condensation fluid, which as a result of said immiscibility are inclined to form two separate and distinct layers of condensation fluid and oil within the fluid-oil separator26, allowing for a relatively easy separation. Lubricating oil that has been separated from the condensation fluid may be returned to the oil sump23via an oil return conduit25fluidly connecting the fluid-oil separator26to the oil sump23.

According to more preferred embodiments, the fluid-oil separator26is alternatively or additionally configured to separate the condensation fluid and the lubricating oil based on evaporation of at least the condensation fluid. In these embodiments, the fluid-oil separator26comprises a heating element32configured to heat the mixture of condensation fluid and lubricating oil to an elevated temperature. At this elevated temperature, the condensation fluid will evaporate, allowing it to exit the fluid-oil separator26via gas outlet27.

The fluid-oil separator26preferably comprises a temperature control to maintain a predefined temperature therein.

While the evaporated condensation fluid exiting the fluid-oil separator26primarily consists of water vapour, some residual lubricating oil may nevertheless still be present in a evaporated state. For environmental reasons, the gaseous flow of evaporated condensation fluid comprising residual lubricating oil exiting fluid-oil separator26is preferably fed back into the combustion chamber3, so that the any residual lubricating oil is combusted there.

The gas outlet27of the fluid-oil separator26thus extends into the inlet channel9. A constriction29—of which the shape preferably resembles a Venturi tube—may be arranged at the section where the gas outlet27debouches into the inlet channel9. The constriction29ensures that a relatively increased flow velocity of gas, including water vapour (condensation fluid) and gaseous lubricating oil, flows from the fluid-oil separator26via the gas outlet27into the inlet channel9and eventually the cylinder1.

As can moreover be discerned fromFIG.3, there is provided a gas inlet28upstream of the constriction29and providing a further connection between the fluid-oil separator26and inlet channel9. The gas inlet28provides a constant introduction of air that is required for the above described gaseous flow from the fluid-oil separator26to the inlet channel9to take place. The gas inlet28thereby moreover prevents air from the crankcase21being sucked in by the fluid-oil separator26.

Further upstream of the gas inlet28there is arranged an air filter30that is configured to filter any ambient air before it is taken in by the internal combustion engine.FIG.3moreover depicts an optional fuel injector31configured to inject a fuel mixture into inlet channel9from which it may flow into the combustion chamber3of the cylinder1. Alternatively, the internal combustion engine may comprise a carburettor (not shown).

It is noted here that the scope of protection for the developments described in the present disclosure are by no means limited to any particular feature of the embodiments described above and illustrated in the appended drawing.

While the present invention has been elucidated with reference to a four-stroke, spark-ignition, engine, these exemplary embodiments should not be understood as being limitative to the present disclosure. Indeed, it is entirely conceivable that the general principles of the present invention as elucidated here above may likewise be applied in a two-stroke engine, a six-stroke engine, and a compression-ignition engine. In light of this, the skilled person will acknowledge that according to the type of internal combustion engine to which the present invention is applied, some of the engine components discussed here above may be omitted while alternative engine components may be present.