KR100291822B1 - Internal combustion engine with coke scraping ring on cylinder - Google Patents

Abstract

The two-stroke crosshead engine with uniflow scavenge device has a coke scraping ring in the cylinder and a piston 18 longitudinally displaceable in the cylinder and having piston rings 19, 19 ′, The piston rings 19, 19 ′ slide along the cylindrical inner surface of the cylinder upon displacement of the piston and form a pressure-sealing separation between the space under the piston and the working chamber 20, the working chamber 20 being a piston. It is disposed above the top piston ring of and is bounded by the top piston ring 19 ', the piston 18, the inner surface of the cylinder and the cylinder cover 8. The coke scraping ring 23 protrudes from the inner surface of the cylinder and extends annularly along the axial position so that the top piston ring is the bottom of the coke scraping ring when the piston is in its top dead center position. Placed near the edge. On the cylindrical inner surface, the coke scraping ring 23 has several leak grooves 24 extending obliquely with respect to the longitudinal axis of the cylinder from the bottom surface to the top surface of the coke scraping ring. Alternatively, leaky grooves may be provided on the cylindrical outer surface of the top piston region 21 disposed above the top piston ring.

Description

Internal combustion engine with coke scraping ring on cylinder

An engine having such a coke scraping ring is known in the art of a four stroke engine having both an intake valve and an exhaust valve in a cylinder cover. The purpose of the coke scraping ring is to scrape the coke attachment from the top of the cylindrical piston above the top piston ring. The uppermost piston ring forms a lower limit of the combustion chamber in an annular space disposed between the uppermost part of the piston above the piston ring and the inner surface of the cylinder. A portion of the combustion product will thus penetrate into the annular space and attach on the outer surface of the top piston region. Lubricant from the cylinder inner surface can also be scattered onto the outer surface. The lubricant residues and attached combustion products will be exposed to the action of intense heat during combustion, which will convert into cohesive coke layers on the piston outer surface as the engine operates. If coke scraping rings are not used, the coke layer will increase in thickness until it reaches the inner surface of the cylinder.

In order to avoid damaging the cylinder and piston rings, an appropriate lubricating film must be maintained between these mutually movable parts. If the coke layer around the piston increases to its maximum thickness and contacts the inner surface of the cylinder, it will interfere with the thin oil film and absorb or scrape a significant amount of lubricating oil, adversely affecting the lubricating conditions. In the worst case, lubrication will be locally degraded, resulting in severe damage to the piston rings or liner.

The coke scraping ring known in the four-stroke engine art limits the thickness of the coke layer when the piston moves near its top dead center position and when the top piston region is reciprocated past the coke scraping ring. The upper and lower annular edges of the coke scraping ring shave coke abutting the edges. Since the scraping ring protrudes from the inner surface of the cylinder, the coke layer is avoided from growing in thickness, which growth causes a contact between the coke layer and the inner surface of the cylinder.

Known engines with coke scraping rings are four-stroke engines, and both the intake and exhaust valves of the four-stroke engines are arranged in the cylinder cover, so other operating conditions of the engine depend on whether or not the coke scraping ring is used. It is not greatly affected. In a four-stroke engine, the scavenge of the cylinder is carried out by an independent piston stroke between each operating stroke, and combustion air supply is made from top to bottom through the intake valve in a subsequent downward intake stroke. Therefore, the coke scraping ring does not affect the scavenging and filling of the cylinder. A more important factor for the desired result achieved with the coke scraping ring of a four-stroke engine is the movement of the piston itself relative to the inner surface of the cylinder. The four-stroke cycle involves different loads on the piston in the upstroke, which is performed every other time, and the form of the load changes every other time in the downstroke. The result is that the radial position of the piston is always changing near the top dead center position, so that the coke scraping ring scrapes the coke deeper than its corresponding inner diameter, so that the coke-coated top is A gap is automatically formed between the piston region and the coke scraping ring. In a Uniflow scavenging two-stroke crosshead engine, the situation is not so simple, and experiments with known coke scraping rings from four-stroke engines have shown increased fuel consumption and especially the top piston ring. It showed operational problems of the same type, such as the damage of, which is surprising because the coke scraping ring was thought to substantially improve the lubrication conditions for the piston rings.

It is an object of the present invention to ameliorate the above drawbacks, to enable the advantageous use of the coke scraping ring in a two-stroke crosshead engine.

The present invention relates to an internal combustion engine having a piston with a coke scraping ring in the cylinder and longitudinally displaceable in the cylinder and provided with a piston ring, wherein the piston rings of the cylinder are displaced during displacement of the piston. It slides along a substantially cylindrical inner surface and forms a pressure-tight separation between the space under the piston and the combustion chamber, which is located above the upper piston ring of the piston and the inner surface of the upper proston ring, piston, cylinder. And a cylinder cover, wherein the coke scraping ring protrudes from the inner surface of the cylinder and extends annularly in an axial position, with the top piston ring being the coke screed when the piston is in its top dead center position. Ensure that the wrapping ring is positioned adjacent the bottom edge.

1 is a schematic cross-sectional view of an engine with a coke scraping ring according to the present invention.

2 is an enlarged partial cross-sectional view around the coke scraping ring in the cylinder of the engine of FIG.

3 is a developed side view of a coke scraping ring.

4 is a plan view of a coke scraping ring.

5 is a perspective view of the top piston region with leaking grooves in the region above the top piston ring.

6 is another embodiment of a piston with a leak groove.

In this respect, the flame is a two-stroke crosshead engine with a uniflow scavenge with the engine having a scavenging air outlet disposed in the lower cylinder region, the coke scraping ring being a coke scraping ring at its cylindrical inner surface. And a plurality of leaking grooves extending obliquely with respect to the longitudinal axis of the cylinder from the bottom surface to the top surface.

It is assumed that the above disadvantages caused by using a coke scraping ring known in a two-stroke engine can be explained with the aid of the mechanism described below. In a two-stroke crosshead engine, the piston executes each upstroke movement stroke, and each downshift movement stroke. This means that each time the piston passes up and down through the coke scraping ring, the piscon is generally loaded in the same way, which is why the piston has a uniform and repetitive form of motion near the top dead center position. Run The propensity of the uniformly shaped movement is reinforced by the crosshead, which guides the lower end of the piston rod in pure translation along the extension of the cylinder. As a result, the coke attachment on the periphery of the piston forms a precise shape-fit into the coke scraping ring, resulting in little gap between the coke scraping ring and the top piston region. When the top of the pescon passes through the coke scraping ring in the compression stroke, an annular cavity between the outer surface of the piston with the coke layer and the inner surface of the cylinder is placed between the protruding coke scraping ring and the top piston ring. It is formed in the axial direction. The upward piston movement creates a rapid axial shortening of the annular cavity at the inevitable strong pressure of its internal air, which causes a very increased load on the top piston ring.

Leak grooves on the cylindrical inner surface of the coke scraping ring reduce or eliminate pressure build-up in the annular cavity, which allows air in the annular cavity to escape through the leak groove into the combustion chamber portion located above the piston. Because there is. This avoids exposing the top piston ring with increased load due to the presence of the coke scraping ring. This is especially important for today's large two-stroke crosshead engines, which have advanced at very high effective compression ratios such as 1:16-1:20, and they themselves have very large loads on piston rings. Generates.

The inclined path of the leaking grooves ensures that the coke is scraped off in the area opposite the leaking grooves. Some of the coke attachment opposite the lower openings of the leaking grooves will not meet at the bottom of the coke scraping ring, but will be scraped to the desired dimension through the top edges of the leaking groove during subsequent upward piston movement. The coke particles scraped into the grooves rise into the space above the piston by leaking air exiting the grooves. Moreover, leaky grooves reduce fuel consumption. Without leaking grooves, the effective piston area is reduced in the first part of the combustion when the piston top is positioned at or above the coke scraping ring, because the coke scraping ring is the pressure in the combustion chamber. This is because the increase prevents the transfer below the top piston ring, where the effective piston area covers the entire cross-sectional area of the cylinder. The leak grooves reduce or eliminate the pressure drop throughout the coke scraping ring during the compression stroke and the operating stroke, and thus the fuel consumption rate is substantially independent of the use of the coke scraping ring.

In large two-stroke diesel engines with high output cylinders of 1500 to 5500 kW, the coke scraping ring offers a particularly advantageous effect, where the fuel emits a direction-specific mist of atomized fuel. It is injected into the cylinder by three or four fuel injectors. Combustion of the fuel produces relatively cohesive thermal action, but the piston is located near the top dead center position where the thermal load is greatest, while the coke scraping ring has only a high temperature gas passing through the leak groove to the piston ring. The heat load is more evenly distributed throughout the top piston ring because it covers the top piston ring and also protects the heat sensitive lubricant film on the inner surface of the cylinder. These two factors provide better operating conditions for the piston ring pack and increase the effect of preventing coke on the piston from contacting the lubricant film.

According to a variant arrangement of leaking grooves on the cylindrical inner surface of the coke scraping ring, the engine is a two-stroke crosshead engine with a uniflow scavenge device with a scavenging air vent disposed in the lower cylinder area, and coke scraping The coke in the cylinder is characterized in that the top piston region disposed above the top piston ring on the cylindrical outer surface of the ring is provided with several leaking grooves extending from the top region of the piston to below the annular groove region of the top piston ring. It is also possible within the scope of the present invention to design the above internal combustion engine with a scraping ring. In the present case, the cylindrical inner surface of the coke scraping ring may be formed as an interfering circular cylindrical surface. During each engine cycle, a flow of both compressed air and combustion gas passes through the leaking grooves, which exclude coke deposits in the grooves.

In the first embodiment, the cylindrical inner surface of the cylinder consists of an upper cover area and a lower liner area, and a coke scraping ring is disposed on top of the liner area. The coke scraping ring may be a ring fitted into a recess in the liner inner surface, or alternatively, it may be a protrusion of the liner material itself, i.e. an integral mate of the liner. In the latter case, the piston with the piston rod must be mounted so that the piston passes from the bottom through the top through the liner before the liner is placed downward in place in the engine assembly. Above all, this embodiment has the advantage that existing engines can be equipped with coke scraping rings.

In a variant embodiment, the cylindrical inner surface of the cylinder consists of an upper cover area and a lower liner area and a coke scraping ring is disposed below the cover area. Also, in this case, the coke scraping ring may be a separate ring inserted into the recess of the upper cover area or may be formed integrally with the cover area, the lower part of the cover area being more than the area disposed thereon. Slightly fine-turned by small inner diameter If the leaking grooves are arranged in the coke scraping ring, they can act up to the bottom of the cover area. This variant embodiment is applicable to cylinders in which the cylinder cover is made of a heat resistant material stronger than the garner, in particular exposed to high heat loads. By placing the coke scraping ring in the cover area, the separation edge between the liner and the cover can be moved down from the top dead center position to the area just above the position for the top piston ring.

The leaking grooves are preferably formed from 0.25 to 50 percent of the axial face of the coke scraping ring protruding from the cylindrical inner surface of the cylinder, more preferably from 5 to 40 percent, preferably from 20 to 30 percent. Most appropriate. If the area of the leak grooves is less than 0.25 percent, the pressure drop across the coke scraping ring becomes too large and no more positive effect is achieved at a leak area of more than 50 percent. The 5 percent limit still results in a pressure drop, but nevertheless a significant improvement in operating conditions, and the 40 percent limit is sufficient to prevent pressure drop across the coke scraping ring. The area of the section between 20 and 30 percent satisfactorily satisfies both the purpose of achieving a small pressure drop or zero pressure drop and a uniform distribution of heat load.

In an engine with a uniflow scavenging device, it is preferred that the micropores be opened by the upper surface of the piston, which means that the coke scraping ring should not protrude too much from the inner surface of the cylinder, for that reason The result of the excessive annular space of the butterfly between the coke scraping ring layer and the inner surface of the cylinder is that the passage of the top piston ring on the upper side of the small pores at the end of the operation stroke opens the small pores. As a result, for a cylinder bore of 250 to 1000 mm, the coke scraping ring preferably protrudes 0.5 to 5 mm, at least 0.2 mm from the inner surface of the cylinder. A low value of 0.2 mm or 0.5 mm ensures complete blocking of small pores until the upper piston surface passes. For the largest engines, the coke scraping ring is appropriate to protrude 2 to 3 mm, at least 1 mm, while 0.5 to 2 mm is suitable for small engines. If the ring protrudes 0.25 mm or less, it is more difficult to ensure that the coke deposits do not reliably contact the lubricant film on the inner surface of the cylinder.

The top piston region disposed above the top piston ring preferably has a smaller diameter than the bottom piston region with piston rings, and the inner diameter of the coke scraping ring is 2-6 mm, at least 0.5 mm more than the diameter of the top piston region. It is desirable to be large, and to be 1 to 4 mm larger. In addition to this diameter ratio, the coke layer can be formed with a thickness of 0.5 to 3 mm, suitably 0.75 to 2 mm, which is applied to the coke scraping ring without the risk of contacting the scraping ring around the piston. Provide a suitable clearance for the radial placement of the piston in relation.

Within the scope of the present invention, a coke scraping ring is applied from the inner surface of the cylinder, with a corresponding decrease in the top piston region diameter such that the annular space around the inner surface of the cylinder and the upper piston region has a large thickness. It is possible to make more derivation than mentioned. This design entails a faster opening of the small pores, ie a faster passage of the top piston ring at the end of the operating track, so that the other parameters of the engine and the opening time of the exhaust valve are dependent on the opening time of the small pores. Should be changed according to a faster supply of air.

The number of leak grooves in the piston or coke scraping ring is determined by the desired leak area and the desired homogenization of the heat load on the top piston ring, and the larger leak area and more uniform distribution of the heat load will result in a greater number of leak grooves. Requires use. The coke scraping ring or piston preferably has 4 to 30 leaking grooves.

More than 15 leak grooves are preferred, as they are quite advantageous for equalizing the heat load to the top piston ring.

If a leaking groove is formed around the top piston region, it is advantageous for the leaking grooves to extend parallel to the axis of the cylinder, so that no fragments of coke are caught in the leaking grooves, thus avoiding the risk of clogging of the leaking grooves. Otherwise, the number and size of leaking grooves may be selected in the same manner as the leaking grooves of the coke scraping ring of the specification described below.

Embodiments of the present invention will be described in more detail with reference to the schematic accompanying drawings.

The engine shown in FIG. 1 is a large two-stroke diesel engine having a uniflow scaffold and is operated with oil such as heavy oil, and combustion of the oil forms a residual product, which remains coarse on the surface of the engine combustion chamber. It can be attached as a crux. Depending on the dimensions and number of cylinders, the engine can generate for example 2,000 to 70,000 kW of power. Such engines are typically used as the ship's main engine or as a stationary power generating engine. In both cases it is important that the engine can be operated for a long time without checking and total disassembly of the engine components. Such engines are preferably capable of being operated continuously for more than two years without total disassembly of the engine, which requires the best operating conditions for the cylinder elements.

The stop of the engine comprises a pedestal 1 on which the crankshaft 2 is journaled and an engine frame box 3 mounted on the pedestal and supporting the cylinder region 4 on its upper surface. The cylinder liner 5 is fixed with respect to the upper plate 6 of the cylinder region by cover studs 7 and the cylinder cover 8. The cylinder liner has a thick wall thickness seated on the upper surface of the upper plate via the annular intermediate member 9 and an elongated lower region projecting downward into the cylinder region 4. At its lower end the cylinder liner has a number of small pores 10, through which the purge and fill air from the scavenging air receiver 11 flows into the cylinder when the piston is near the bottom dead center position. do. An exhaust valve housing 12 having a hydraulically actuated exhaust valve is arranged in the center of the cylinder cover. When the exhaust valve is opened, the scavenging air from the small holes flows upwardly through the cylinder, and at the same time, the combustion gas flows into the exhaust receiver 13 through the exhaust valve, from which the gas is turbocharged. It flows into the exhaust pipe via the charger. The engine is high-pressure charged, for example at a charging pressure of 3.5-4 bar.

The connecting rod 14 connects the crankshaft 2 with the cross head 15, which cross piston 15 is provided by the guide surface 16 of the engine frame box in a reciprocating motion of the longitudinal axis of the cylinder in a piston rod 17. Guide the bottom of the). The piston 18 is mounted on top of the piston rod. As best shown in FIG. 2, the piston has several, for example four, piston rings 19, 19 ′, which slide along the inner surface of the cylinder liner and are located below the piston. To form a pressure-sealing separation between the combustion chamber 20 and the space communicating with the cavity of the cylinder region filled with the scavenging air.

Combustion chamber or combustion chamber 20 has an inner surface of cylinder cover 8, an inner surface of cylinder liner 5, a top of piston 18, a top piston ring 19 ′ and a top piston region extending upward from the top piston ring. It is limited to around 21. The upper piston region 21 has a smaller diameter than the lower part of the piston, where an annular space exists between the outer surface of the upper piston region and the inner surface of the cylinder, in which coke adheres to the outer piston surface. Will be.

The annular coke scraping ring 23 in the cylinder protrudes from the inner surface of the cylinder, scraping the coke attachment on the outer surface of the top piston region 21, such that the attachments have an inner diameter of the coke scraping ring. It is possible not to exceed the maximum diameter corresponding to. The coke scraping ring changes the axial position of the cylinder such that the upper piston ring 19 'is smaller than the ring height below the coke scraping ring 23 when the piston is in the top dead center position shown in the figure. This ensures that the coke layer is always scraped off mainly under the top piston ring. Although the coke scraping ring is placed somewhat higher, for example by two to three ring heights, a substantial coke-scraping effect will still be achieved.

3 and 4 show, on its inner surface, several leaks forming a gas flow passage in communication between a portion of the annular space 22 disposed below the coke scraping ring and the remaining upper region of the combustion chamber 20. A coke scraping ring with grooves 24 is presented. The flow area of the leaking grooves is suitably applied so that the pressure drop across the coke scraping ring is negligible. The leaking grooves are advantageously distributed evenly along the inner circumference of the coke scraping ring because it generates a very uniform heat load on the uppermost piston ring 19 '. The depth of the leak grooves may correspond to the protruding thickness of the coke scraping ring with respect to the inner surface of the cylinder. This is particularly advantageous if the coke scraping ring protrudes from the inner surface at short intervals of, for example, 0.5-3 mm, at least 0.25 mm. When the piston and the scraping ring are manufactured in such a way that the annular space 22 has a wide width, and the small pores 10 are opened by the passage of the uppermost piston ring, the depth of the leaking grooves is coke scraping. It should be smaller than the thickness of the inward protrusion of the ring. At larger depths it is desirable that the leaking grooves not be deeper than 3 -4 mm, since the gas flow through each groove can be so large that the heat load on the uppermost piston ring can be too high locally. For example, a very uniform heat distribution can be achieved with a groove of depth less than 1.5-2 mm combined with 15 or more appropriately large numbers of leak grooves.

The width of the leaking grooves is selected based on the number of leaking grooves, the groove depth and the desired total flow area, ie the overall axial cross-sectional area of the groove ends. In most cases a groove width of 5-30 mm will be appropriate, and a groove width of 10-20 mm is suitable for achieving a uniform heat load.

The leak groove 24 extends obliquely with respect to the longitudinal axis of the cylinder, so that the upper groove end 25 is disposed in the circumferential direction with respect to the lower groove end 26. This provides the advantage that the coke layer scrapes along the entire perimeter of the upper piston region 21. In the illustrated embodiment, the longitudinal axis of the leaky groove forms an angle of 45 degrees with the longitudinal axis of the cylinder. Of course, other angles between 15 and 80 degrees may be used. The angle is applied to the groove width such that no axial overlap occurs between the upper groove end 25 and the lower groove end 26. For fabrication reasons, the leak groove preferably extends straight between the upper and lower groove ends, but other designs that allow communication between the upper groove end 25 and the lower groove end 26 are L-shaped or non-linear. Course-like design can be selected without difficulty.

5 and 6 show an embodiment in which leak grooves are disposed on the piston outer surface of the uppermost piston region. For simplicity of explanation, like reference numerals are used for like elements. It should be noted that the piston rings in the drawings are omitted.

5, the longitudinal section of the top of the cylinder cover 8 and the liner 5 in the region around the coke scraping ring 23 ′ formed directly to the cylinder cover material, ie integrally with the cover, to the left of the piston. Is shown. To the right of the piston, a longitudinal section corresponding to the design variant is shown, wherein the coke scraping ring 23 'is made directly to the material of the cylinder liner, ie as an integral part and a joint of the liner. Comparing the left side and the right side of the drawing, in the same engine, the coke scraping ring 23 'can be placed on the cylinder cover such that the separating surface 27 between the cylinder cover and the liner moves downward in the longitudinal direction of the cylinder. Immediately see the benefits. Since the inner surface of the cover does not constitute a sliding surface for the piston ring, lubricity and sliding characteristics can be neglected in the selection of the cover material. Thus, the cover may be made of a material such as steel that is more corrosion and heat resistant than liner material, which is typically cast iron. The influence of heat is greatest in the upper region of the cylinder, and as a result longer life can be achieved by the cover extending further downward.

In the embodiment shown, the coke scraping ring 23 ′ disposed on or in liner 5 or on cover 8 or in cover 8 has a cylindrical inner surface 28. The inner surface 28 is annular and there are no leaking grooves. Of course, some leak grooves may be placed in the coke scraping ring and some leak grooves may be placed in the piston, and for manufacturing reasons, if the design is desired, for example, it may be made by rotating the inner surface of the liner or cover. have.

The leak grooves 24 ′ are arranged in the uppermost region 21 of the piston and extend downward from the chamfer of the upper rim of the piston to the uppermost annular groove 29 for the uppermost piston ring. The uppermost region 21 of the piston is at a higher height, so that when the piston is at top dead center the piston rings are placed further downward in the cylinder, which allows the cylinder cover to extend further down the cylinder.

The leaking grooves of FIG. 5 form an angle r of about 30 degrees with the longitudinal axis of the cylinder. In practice, the angle can be chosen between 0 and 60 degrees or larger, but along the minimum length portion the groove forms an angle of at least 15 degrees, which prevents the upper and lower groove ends from being placed perpendicular to each other. It is preferable.

Figure 6 shows a variant embodiment of the piston, where the leak grooves 24 "have an upper region 24a extending parallel to the longitudinal axis of the cylinder and a lower region 24b extending obliquely with respect to the longitudinal axis of the cylinder. The inclined lower region 24b displaces the lower groove end in the circumferential direction with respect to the upper groove end, so that coke is scraped along the entire circumference.The upper region 24a of the leaking grooves does not contribute to scraping out the coke. There is therefore no risk of clogging with scratched coke particles It is also possible to place the inclined area of the leaking groove at the top of the groove, which leads to a faster gas velocity through the grooves during the scraping of the coke. This is because the piston's movement speed is faster while the upper groove region passes through the coke scraping ring.

The design of the inclined groove region at the lower end of the grooves is particularly advantageous when the relatively high height of the top region 21 of the piston is formed by the separating piston top fixed to the lower piston region having an annular groove for the piston ring. In this case, the two regions of the leaking grooves can be produced in a simple manner as a straight groove of each piston region.

Otherwise, depending on area and number, the leaking grooves may be formed corresponding to the leaking grooves aligned with the coke scraping ring.

Claims (11)

An internal combustion engine with piston rings (19, 19 ') having a coke scraping ring in the cylinder and a piston (18) displaceable longitudinally in the cylinder, the piston rings being When displaced, it slides along a substantially cylindrical inner surface of the cylinder and forms a pressure-tight separation between the space under the piston and the working chamber, which is disposed above the top piston ring of the piston. And the uppermost piston ring 19 ', the piston 18, the inner surface of the cylinder and the cylinder cover 8, wherein the coke scraping ring 23 protrudes from the inner surface of the cylinder and is axially oriented. In an internal combustion engine which extends annularly in position, with the coke scraping ring positioned near the bottom and the top piston ring when the piston is in the top dead center position, the engine comprises small pores (10). Genie is a two-stroke crosshead engine with a uniflow scavenger disposed in the lower cylinder region, with a compression stroke in the annular space between the inner surface of the cylinder and the outer surface of the piston and the uppermost piston ring and coke scraping rings. An internal combustion engine, characterized in that a plurality of leaking grooves are formed to reduce the pressure formed during the process. The cylinder of claim 1, wherein the plurality of leak grooves (24) are disposed on a cylindrical inner surface of the coke scraping ring (23) and from the lower surface to the surface of the upper portion of the coke scraping ring. An internal combustion engine, characterized by extending obliquely with respect to the longitudinal axis. The area of the annular groove according to claim 1, wherein the plurality of leak grooves 24 'are located on the cylindrical outer surface of the uppermost piston region 21, and the uppermost piston ring 19' is located from the top of the piston region. Internal combustion engine, characterized in that extended to. 4. The substantially cylindrical inner surface of the cylinder according to claim 2 or 3 consists of an upper cover area and a lower liner area, with the coke scraping rings 23 and 23 'at the top of the liner area 5. An internal combustion engine, characterized in that arranged. 4. The substantially cylindrical inner surface of the cylinder according to claim 2 or 3, comprising an upper cover area and a lower liner area, wherein the coke scraping rings 23, 23 'are disposed below the cover area. An internal combustion engine characterized by the above-mentioned. 6. An internal combustion engine according to claim 5, wherein the coke scraping ring (23, 23 ') is an integral joint of the substantially cylindrical inner surface of the cylinder. 4. The leaking grooves (24, 24 ') of claim 2 or 3 have a 0.25 to 50 percent of the axial area of the coke scraping rings (23, 23') protruding from the cylindrical inner surface of the cylinder. And preferably from 5 to 40 percent, suitably from 20 to 30 percent of the area. 4. The cylinder bore of claim 2, wherein the cylinder bore is between 250 and 1000 mm and the coke scraping rings 23, 23 ′ protrude at least 0.2 mm, preferably 0.5 to 5 mm, from the inner surface of the cylinder. An internal combustion engine, characterized in that. 4. The top piston region 21 according to claim 2 or 3, arranged above the top piston ring 19 ', has a smaller diameter than the bottom piston region with piston rings, and coke The inner diameter of the scraping rings 23, 23 'is 2 to 6 mm larger than the diameter of the top piston region and is at least 0.5 mm, suitably 3 to 4 mm larger than the diameter of the top piston region and at least 1 mm. An internal combustion engine, characterized in that. 4. The coke scraping ring (23, 23 ') or the uppermost piston region (21) is provided with 4 to 30 leak grooves, preferably 15 leak grooves. An internal combustion engine characterized by the above-mentioned. 4. The longitudinal axis of the leak grooves 24, 24 'forms an angle of 0 to 60 degrees with the axial direction of the cylinder, preferably at least 15 degrees, preferably 45 degrees. Internal combustion engine to form a.

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