Piston Ring Package

Abstract

To provide a piston ring package 100 for a piston 20 of a reciprocating internal combustion engine, a piston with such a piston ring package, and a reciprocating internal combustion engine with such a piston 20, which realize a sufficient sealing and an easy manufacturing.SOLUTION: The piston ring package 100 comprises at least a first piston ring 1 and a second piston ring 2. The first piston ring 1 is arranged to be gastight for a pressure from a first axial side 3 of the piston ring package 100, and the second piston ring 2 is gas-tight for a pressure from a second axial side 4 opposite to the first axial side 3.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a piston ring package for a piston of a reciprocating internal combustion engine according to the general title of claim 1, to a piston equipped with such a piston ring package and to a reciprocating internal combustion engine equipped with such a piston. [Background technology]

[0002] The invention relates to an internal combustion engine, such as a large marine or ship-based engine, or a stationary engine, preferably whose cylinders have an internal diameter of at least 200 mm. The engine is preferably a two-stroke engine or a two-stroke crosshead engine. The engine may be a diesel or gas engine, a dual-fuel or multi-fuel engine. In this type of engine, the combustion of liquid and / or gaseous fuels and auto-ignition or forced ignition are possible.

[0003] The internal combustion engine may be a longitudinally scavenged two-stroke engine.

[0004] The term internal combustion engine also refers to larger engines capable of operating not only in a diesel mode characterized by the self-ignition of one fuel, but also in an Otto mode characterized by positive ignition of one fuel, or a mixture of the two. Furthermore, the term internal combustion engine specifically includes dual-fuel engines and larger engines in which the self-ignition of one fuel is used in conjunction with the spark ignition of another fuel.

[0005] The engine speed is preferably below 800 RPM, especially for a four-stroke engine, and more preferably below 200 RPM, especially for a two-stroke engine, which implies the name slow speed engine.

[0006] The fuel may be diesel or marine diesel, or heavy fuel oil, or an emulsion, or a slurry, or methanol, or ethanol, as well as gases such as liquefied natural gas (LNG), liquefied petroleum gas (LPG), and the like.

[0007] Further possible fuels that could be added depending on requirements are liquefied biogas (LBG), biofuels (e.g. oil produced from algae or seaweed), ammonia, hydrogen, CO 2 Synthetic fuels derived from natural gas (e.g., produced by Power-to-Gas or Power-to-Liquid).

[0008] Larger ships, especially those used for the transportation of cargo, are usually powered by internal combustion engines, in particular diesel and / or gas engines, mostly two-stroke, crosshead engines.

[0009] The pistons of reciprocating piston internal combustion engines, particularly those of the dual fuel or Otto cycle type, are provided with piston rings which form a piston ring package and which are mounted in grooves in the piston and serve to seal the combustion chamber from the outside.

[0010] At least the top ring of the piston ring package is cut to allow the piston ring to expand when seated within the ring groove in the piston sidewall. Typically, the two ends of the cut in the ring are designed to form locking ends to substantially prevent gases in the combustion chamber of the cylinder from flowing through the cut.

[0011] The two locking ends of the top ring may have overlapping tongues that close off at least a majority of the ring gap and limit the ability of combustion gases to flow through the ring gap.

[0012] Such a top piston ring is disclosed, for example, in European Patent Application Publication No. 20167735.8, which is incorporated herein by reference.

[0013] DE 102017118773 A1 discloses a piston ring package having three piston rings, an upper or combustion chamber side compression ring and a lower or crankcase side compression ring, and a central oil scraper ring arranged between the upper and lower compression rings. The compression rings have a small clearance to provide a good seal and minimize blow-by.

[0014] The upper compression ring may be identical to the lower compression ring in terms of dimensions and other mechanical properties, thereby realizing a reduced number of different components.

[0015] According to DE 102017118773 A1, a pressurized oil reservoir is created between an upper and a lower compression ring, the average pressure of which corresponds approximately to the average value between the pressure in the crankcase and the average pressure in the combustion chamber. According to DE 102017118773 A1, the top piston ring and the bottom ring are arranged in parallel and essentially provide a seal towards the space below the piston.

[0016] For the purpose of reducing ring wear of the upper piston ring, a controlled leakage of gases may be allowed to escape from the combustion chamber, as disclosed, for example, in EP 0 742 875 B1. According to DE 10 2010 020 490 B4, the allowed leakage decreases from the piston ring closest to the combustion chamber to the piston ring furthest from the combustion chamber.

[0017] During each piston stroke, the piston ring assembly is exposed from above to the combustion pressure created in the combustion chamber bounded by the piston, and from below to the pressure present beneath the piston.

[0018] There is a risk that pressure from below, coming from the space below the piston, will have an effect on the piston rings, for example lifting the top piston ring off the lower wall of the piston ring groove, especially during the piston's axial downward movement towards the crankcase. Leaks may therefore be possible in the direction towards the combustion chamber. Oil may pass into the combustion chamber and deposits may form on the liner. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] German Patent Application Publication No. 102017118773 (A1) [Patent Document 2] European Patent No. 0742875(B1) [Patent Document 3] German Patent Application Publication No. 102010020490 (B4) Summary of the Invention [Problem to be solved by the invention]

[0020] The present invention is based on the object of providing a piston ring package which avoids the known disadvantages and in particular provides a satisfactory sealing and easy manufacture, a piston equipped with such a piston ring package and a reciprocating internal combustion engine equipped with such a piston. [Means for solving the problem]

[0021] This object is achieved by means of the features of the independent claims.

[0022] According to the present invention, a piston ring package for a piston of an internal combustion engine has at least a first piston ring and a second piston ring.

[0023] The first piston ring is positioned such that it is gas-tight against pressure from a first axial side of the piston ring package, and the second piston ring is positioned such that it is gas-tight against pressure from a second axial side opposite the first axial side.

[0024] Thus, the piston ring package provides gas tightness towards both axial sides of the piston ring package.

[0025] The first axial side may correspond to a direction facing towards the combustion chamber and the second axial side may correspond to a direction facing towards the space below the piston.

[0026] Preferably, the first piston ring is adapted to prevent combustion gases from entering the space below the piston ring, while the second piston ring prevents pressure from below the piston acting on the first piston ring, particularly during downward movement of the piston towards the crankcase.

[0027] In use, the first and second piston rings may be mounted in the same groove of the piston, or the first and second piston rings may be mounted in respective grooves.

[0028] The first and second piston rings may have the same locking mechanism but are disposed towards opposite axial sides.

[0029] The first and second piston rings may have different heights and / or different cross sections. The second piston ring may have a smaller height than the first piston ring.

[0030] In a preferred embodiment of the piston ring package, the first piston ring is identical to the second piston ring.

[0031] Thus, the first and second piston rings have the same shape. The first and second piston rings are equivalent in terms of dimensions and other mechanical properties. However, the piston rings are positioned differently within the piston package.

[0032] The first piston ring may have a piston ring lock that is gas-tight against pressure from the first axial side.

[0033] The second piston ring may have the same piston ring lock as the first piston ring, and when arranged in a piston ring package, the second piston ring is arranged in an axially opposite direction to the first piston ring such that the piston ring lock is gas-tight toward the second axial side.

[0034] Thus, the tightness for the two different axial sides of the piston ring package is provided by two identical piston rings.

[0035] The first and second piston rings may be cambered.

[0036] The contact line of the piston ring with the cylinder is usually defined by the most extended line of cambering, and in the case of a piston ring lock with male and female locking ends, the contact line is preferably located on the male locking end.

[0037] The crown's maximum extension line is preferably axially centered on the height of the piston ring.

[0038] Alternatively, the line of greatest extension may divide the height of the piston ring into smaller and larger portions, such as one-quarter and three-quarters of the height. Preferably, the crown of the first piston ring is disposed with its smaller portion offset to the second axial side, whereas the crown of the second piston ring is disposed with its smaller portion offset to the first axial side.

[0039] Advantageously, the first piston ring has a locking portion with a male locking end and a female locking end.

[0040] The first piston ring may have a ring portion and a lock portion with female and male lock ends. The outside of the top ring is in contact with the cylinder liner.

[0041] The male locking end has a protruding tongue that projects into a corresponding recess in the female locking end.

[0042] In the radial direction, the tongue is smaller than the ring portion and the recess is bounded on the inside of the first piston ring by a vertical wall which contacts the inside of the tongue. The axial height of the tongue is smaller than the axial height of the ring portion and the recess is bounded in the axial direction by a protruding wall. The side of the protruding wall facing towards the second axial side contacts the side of the tongue facing towards the first axial side. The recess is therefore open towards the second axial side.

[0043] Because the tongue essentially fills the recess in the width and height directions, combustion gases are substantially prevented from flowing through the cut whether or not the tongue is circumferentially spaced from the bottom of the recess. The circumferential distance between the tongue and the bottom of the recess changes with expansion of the piston ring which is dependent on thermal conditions.

[0044] Alternatively or additionally, the second piston ring has a ring portion and a locking portion with a male locking end and a female locking end.

[0045] The male locking end has at least one protruding tongue that protrudes into a corresponding recess in the female locking end.

[0046] In the radial direction, the tongue is smaller than the ring portion and the recess is bounded on the inside of the second piston ring by a vertical wall which contacts the inside of the tongue. The axial height of the tongue is smaller than the axial height of the ring portion and the recess is bounded in the axial direction by a protruding wall. The side of the protruding wall facing towards the first axial side contacts the side of the tongue facing towards the second axial side. The recess opens towards the first axial side.

[0047] The locking portion of the second piston ring withstands pressure acting from the second axial side towards the piston ring package.

[0048] The locking ends of the first and second piston rings are preferably equivalent in size.

[0049] In an advantageous embodiment, the first piston ring is a top piston ring and / or the second piston ring is a bottom piston ring, such that the first piston ring is the piston ring closest to the combustion chamber of the piston ring package and the second piston ring is the piston ring furthest from the combustion chamber.

[0050] The piston ring package may include at least one further piston ring.

[0051] The at least one further piston ring may be an oil distribution ring arranged between the first and second piston ring and / or next to the second piston ring on a side of the second ring facing away from the first ring.

[0052] The oil distribution ring may have oil scraping blades to create a defined oil film on the inner surface of the cylinder and to remove excess oil, for example via an oil scavenge groove in the piston.

[0053] The at least one additional piston ring may be a gas-tight piston ring disposed between the first piston ring and the second piston ring and disposed such that it is gas-tight against pressure from the first axial side of the piston ring package. The additional piston ring may be identical to the first piston ring and disposed in the same manner. The additional piston ring provides an additional barrier in case gas passes through the first piston ring.

[0054] The at least one further piston ring may be a gas-tight piston ring arranged between the first piston ring and the second piston ring and arranged such that it is gas-tight against pressure from a second axial side of the piston ring package. The further piston ring enhances the function of the second piston ring.

[0055] The at least one further piston ring may be a non-gas-tight piston ring.

[0056] The at least one further piston ring may differ from the first and / or second piston ring in terms of dimensions, the further piston ring may have a different height or may have a different cross-section.

[0057] Further piston rings may have a straight lock.

[0058] A piston ring package may have a combination of different types of piston rings.

[0059] The object is also achieved by a piston for an internal combustion engine, comprising a piston ring package as described above.

[0060] The piston may have at least one groove for a first and a second piston ring, preferably the first piston ring being disposed in a first groove of the piston and the second piston ring being disposed in a second groove axially spaced from the first groove.

[0061] The object is also achieved by a combustion engine having a piston as described above.

[0062] Further advantageous aspects of the invention are explained below with the aid of exemplary embodiments and a drawing, in which: [Brief description of the drawings]

[0063] [Figure 1] FIG. 1 is a schematic diagram of a first example of a piston ring package. [Diagram 2] FIG. 2 is a schematic diagram of a cross-sectional view of a piston according to a first example. [Diagram 3] FIG. 13 is a schematic diagram of a cross-sectional view of a second example of a piston. [Figure 4] FIG. 13 is a schematic diagram of a cross-sectional view of a third example of a piston. [Diagram 5] FIG. 13 is a schematic diagram of a cross-sectional view of a fourth example of a piston. [Figure 6] FIG. 13 is a schematic diagram of a cross-sectional view of a fifth example of a piston. [Figure 7] FIG. 13 is a schematic diagram of a cross-sectional view of a sixth example of a piston. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0064] 1 shows a schematic diagram of a first example of a piston ring package 100. The piston ring package 100 includes a first piston ring 1 and a second piston ring 2.

[0065] The first piston ring 1 is arranged so as to be gas-tight against pressure from a first axial side 3 of the piston ring package 100, and the second piston ring 2 is gas-tight against pressure from a second axial side 4 opposite the first axial side 3.

[0066] The first piston ring 1 has a locking portion 11 with a male locking end 12 and a female locking end 13. The male locking end 12 has at least one protruding tongue 14 that protrudes into a corresponding recess 15 in the female locking end 13.

[0067] The recess 15 opens towards the second axial side 4 .

[0068] The second piston ring 2 is dimensionally identical to the first piston ring 1, but is arranged upside down.

[0069] The second piston ring 2 also has a locking portion 11 with a male locking end 12 and a female locking end 13. The male locking end 12 has at least one protruding tongue 14 which protrudes into a corresponding recess 15 of the female locking end 13. The second piston ring is arranged differently than the first piston ring 1, so that the recess 15 of the second piston ring 2 opens towards the first axial side 3.

[0070] FIG. 2 shows a schematic cross-sectional view of a piston 20 according to a first example.

[0071] The piston 20 has two grooves 21, one for the first piston ring 1 forming the top piston ring and one for the second piston ring 2 forming the bottom piston ring.

[0072] The piston rings 1, 2 are crowned. The contact line of the piston rings 1, 2 with the liner 31 of the cylinder 30 is defined by the most extended line 5 of the crown.

[0073] The crown's most extended line 5 divides the overall height 6 of the piston rings 1, 2 into a minor portion 7 and a major portion 8. The minor portion 7 of the first piston ring 1 is offset towards the second axial side 4. The second piston ring 2 is arranged in the opposite direction so that the minor portion 7' ​​of the second piston ring 2 is offset towards the first axial side 3.

[0074] 3 to 6 show schematic cross-sectional views of second, third, fourth and fifth examples of piston 20. FIG.

[0075] The piston 20 has three grooves 21 .

[0076] The first piston ring 1 is arranged so as to be gas-tight against pressure from a first axial side 3, and the second piston ring 2 is arranged so as to be gas-tight against pressure from a second axial side 4.

[0077] As shown in FIG. 3, the oil distribution ring 40 is disposed between the first piston ring 1 and the second piston ring 2 .

[0078] An oil distribution ring 40 may be positioned to direct excess oil towards the second axial side.

[0079] As shown in Figure 4, a further piston ring 45, which may have a straight lock, is placed between the first piston ring 1 and the second piston ring 2. Alternatively, the further piston ring 45 may have male and female locking ends. Alternatively, the further piston ring 45 may be crowned.

[0080] The further piston ring 45 may be crowned or have a straight outer cross section.

[0081] Alternatively, the piston 20 may have four grooves (not explicitly shown) in which the oil distribution ring 40 and the further piston ring 45 are arranged between a first piston ring 1 arranged so as to be gas-tight against pressure from a first axial side 3 and a second piston ring 2 arranged so as to be gas-tight against pressure from a second axial side 4.

[0082] As shown in FIG. 5, a further first piston ring 1 ′ arranged in a gas-tight manner against pressure from a first axial side 3 is arranged between the first piston ring 1 and the second piston ring 2 .

[0083] As shown in FIG. 6, a further second piston ring 2′ arranged in a gas-tight manner against pressure from a second axial side 4 is arranged between the first piston ring 1 and the second piston ring 2.

[0084] 7 shows a schematic diagram of a cross-section of a sixth example of a piston 20. The piston 20 has four grooves 21.

[0085] An oil distribution ring 40 is arranged below the first piston ring 1 arranged so as to be gas-tight against pressure from the first axial side 3 and the second piston ring 2 arranged so as to be gas-tight against pressure from the second axial side 4.

[0086] Furthermore, a further piston ring 45 may be arranged between the first piston ring 1 and the second piston ring 1 .

[0087] Alternatively, between the first piston ring 1 and the second piston ring 1, a further first piston ring 1', a further second piston ring 2' and / or a further oil distribution ring 40 (not shown) may be arranged.

Claims

1. A piston ring package (100) for a piston of an internal combustion engine, comprising at least a first piston ring (1) and a second piston ring (2), the first piston ring (1) is arranged so as to be gas-tight against pressure from a first axial side (3) of the piston ring package (100), and the second piston ring (2) is gas-tight against pressure from a second axial side (4) opposite to the first axial side (3); the first piston ring (1) has a locking portion (11) with a male locking end (12) and a female locking end (13), the male locking end (12) has at least one protruding tongue (14) protruding into a corresponding recess (15) of the female locking end (13), the recess (15) opening towards the second axial side (4), the recess (15) being bounded on the inside of the first piston ring (1) by a vertical wall contacting the inside of the protruding tongue (14); 10. A piston ring package (100) comprising: said second piston ring (2) having a locking portion (11) with a male locking end (12) and a female locking end (13'), said male locking end (12) having at least one protruding tongue (14) protruding into a corresponding recess (15) of said female locking end (13), said recess (15) opening towards said first axial side (3), said recess (15) being bounded, on the inside of said second piston ring (2), by a vertical wall contacting the inside of said protruding tongue (14).

2. 2. The piston ring package of claim 1, wherein the first piston ring (1) is the same as the second piston ring (2).

3. the first piston ring (1) is a top piston ring, and / or 3. The piston ring package according to claim 1 or 2, wherein the second piston ring (2) is a bottom piston ring.

4. 2. The piston ring package of claim 1, wherein the piston ring package (100) comprises at least one additional piston ring (40, 45).

5. 5. The piston ring package of claim 4, wherein said at least one further piston ring is an oil distributing ring (40).

6. 6. The piston ring package according to claim 5, wherein at least one further piston ring (40) is an oil-distributing ring (40) arranged between the first piston ring (1) and the second piston ring (2) and / or arranged adjacent to the second piston ring (2) on a side of the second piston ring (2) facing away from the first piston ring (1).

7. 6. The piston ring package according to claim 5, wherein at least one further piston ring (45, 1') is a gas-tight piston ring arranged between the first piston ring (1) and the second piston ring (2) and arranged to be gas-tight against pressure from the first axial side (3) of the piston ring package (100).

8. 6. The piston ring package according to claim 5, wherein at least one further piston ring is a gas-tight piston ring (45, 2') arranged between the first piston ring (1) and the second piston ring (2) and arranged to be gas-tight against pressure from the second axial side (4) of the piston ring package (100).

9. A piston (20) for an internal combustion engine, comprising a piston ring package (100) according to at least one of claims 1 to 8.

10. A combustion engine having a piston (20) according to claim 9.

11. 2. The piston ring package of claim 1, wherein said first piston ring and said second piston ring are formed with a crown and have a most extending line of said crown.

12. 12. The piston ring package of claim 11, wherein the most extended line of the crown is disposed on the male lock ends of the first piston ring and the second piston ring.

13. 13. The piston ring package of claim 11 or 12, wherein the most extended line of the crown is axially centered between the heights of the first piston ring and the second piston ring.

14. 13. The piston ring package of claim 11 or 12, wherein the most extended line of the crown divides the height of the first piston ring and the second piston ring into a smaller portion and a larger portion.

15. 15. The piston ring package of claim 14, wherein the crown of the first piston ring is disposed such that the minor portion is offset toward the second axial side, while the crown of the second piston ring is disposed such that the minor portion is offset toward the first axial side.

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