Piston ring assembly

Abstract

The invention relates to a piston ring assembly comprising an annular base body having a gap, and comprising a cover element covering the gap of the base body, the annular base body having a first end and a second end arranged adjacent to each other and separated by the gap, the base body having a radially outer face and a radially inner face, the base body has a first axial face and a second axial face, and the base body has a first recess at a first end and a second recess at a second end such that the first recess and the second recess leave corresponding projections at the first end and at the second end, and the cover element has a first lateral portion, an intermediate portion and a second lateral portion, the intermediate portion is located between the lateral portions, the first and second lateral portions each having a third recess, and the cover element is located at the base body such that the intermediate portion of the cover element covers the gap of the base body and each projection of the end of the base body is located in the third recess of the lateral portion of the cover element.

Description

Technical Field

[0001] The present invention relates to a piston ring assembly, particularly for an internal combustion engine designed to use carbon-neutral fuels. The present invention also relates to a piston having a piston ring assembly and an internal combustion engine having a piston with a piston ring assembly. Background Art

[0002] Internal combustion engines have at least one movable piston that is movably disposed within a cylinder such that the top surface of the piston defines a chamber for combustion. Due to the increasing concerns about environmental issues related to pollutant emissions from internal combustion engines using fossil fuels, several methods are being studied to minimize their impact. Currently, most internal combustion engines have been optimized to operate with fossil fuels such as gasoline, natural gas, liquefied petroleum gas, and diesel, and thus they have a significant environmental impact. New developments are focused on new carbon-neutral fuels such as hydrogen, which burns to produce water vapor.

[0003] Using new fuels generally requires improvements to the internal combustion engine such that the engine operates safely, efficiently, and durably. This is the case with hydrogen, which has different properties compared to fossil fuels, such as mixture requirements, combustion temperature, and pressure. Two main concerns in operating hydrogen in an internal combustion engine are the air / fuel mixture flow into the crankcase and the presence of lubricating oil in the combustion chamber.

[0004] These situations are also common with other fuels, as the way they occur is related to the overall geometry of the engine components. However, when the fuel is hydrogen, these two concerns present greater problems because hydrogen is flammable at much higher air / fuel concentration ratios than other fuels, making its presence in the crankcase a potential for accidental ignition. In addition, the oil in the combustion chamber will ignite with the hydrogen and produce carbon dioxide and particulate emissions. Furthermore, the oil vapor in the combustion chamber alters the air / fuel mixture and may cause a situation where the engine compression is sufficient to ignite the mixture before timed ignition.

[0005] Generally, a piston has a plurality of grooves for placing annular piston rings that also contact the cylinder. These rings have gaps that facilitate assembly within the piston grooves and provide tension to the rings such that the rings remain in contact with the cylinder. Thus, gas can flow through the gaps. Such an effect is referred to as "blow-by", which has a negative impact on engine efficiency and results in unwanted fuel in the crankcase.

[0006] Document EP3889471A1 discloses a piston ring for an internal combustion engine of a ship, such that for a two-stroke engine the engine speed is in the range of 200 RPM, and for a four-stroke engine the engine speed is in the range of 800 RPM, and the inner diameter of the cylinder is at least 200 mm. The piston ring has a ring portion and a lock portion, and the lock portion has a convex locking end and a concave locking end that act on each other. Such a piston ring design is not suitable for an internal combustion engine for automotive applications operating at higher engine speeds up to 6000 RPM. At high engine speeds, the lock portion cannot lock the concave locking end to the convex locking end, and the piston ring will open the lock portion, resulting in air leakage and likely damage to the lock portion of the piston ring. Summary of the Invention

[0007] An object of the present invention is to create an improved piston ring assembly compared to the prior art. Another object is to find a solution to minimize air leakage and the presence of an oil film inside the combustion chamber of an internal combustion engine, thereby improving the efficiency of the internal combustion engine and allowing for safe operation when using hydrogen as fuel. In addition, an object of the present invention is to create an improved piston and an improved internal combustion engine.

[0008] The object regarding the piston ring assembly is solved by the features of claim 1.

[0009] An exemplary embodiment of the present invention relates to a piston ring assembly that includes an annular base body having a gap, and includes a cover element that covers the gap of the base body. The annular base body has a first end and a second end that are arranged adjacent to each other and separated by the gap. The base body has a radially outer surface and a radially inner surface, and the base body has a first axial surface and a second axial surface. The base body has a first recess at the first end and a second recess at the second end, such that the first recess and the second recess leave corresponding protrusions at the first end and at the second end. The cover element has a first lateral portion, a middle portion, and a second lateral portion. The middle portion is located between the lateral portions. Each of the first lateral portion and the second lateral portion has a third recess. The cover element is located at the base body such that the middle portion of the cover element covers the gap of the base body, and each protrusion of the end of the base body is located in the third recess of the lateral portion of the cover element. Such a piston ring assembly makes assembly easy because the base body is an open annular component with a gap, which is easy to assemble, and the cover element covers the gap, such that there is no fuel leakage or only very small fuel leakage, making this design useful for internal combustion engines operating with non-fossil fuels such as hydrogen, and minimizing oil leakage.

[0010] According to an embodiment of the present invention, advantageously, the protrusion projects from the face of the first recess and from the second recess in the radial direction. This allows the protrusion to block gas in the axial direction, while the protrusion is also used to define the position of the cover element and hold it in place even at high engine speeds.

[0011] According to another embodiment of the present invention, advantageously, the outer radial face of the protrusion is aligned with the outer radial face of the annular base body. This results in the fact that the protrusion has the same function when contacting the inner wall of the cylinder of the internal combustion engine, but has an additional function in terms of the positioning of the cover element and holds it in place even at high engine speeds.

[0012] According to another embodiment of the present invention, advantageously, the radial depth of the first recess at the first end of the annular base body and the second recess at the second end is less than the radial depth of the base body, in particular less than half of the radial depth of the base body. This enables the base body and the cover element to have sufficient stability even at high engine speeds.

[0013] According to another embodiment of the present invention, advantageously, the first recess at the first end and the second recess at the second end are in the shape of a C, and each of the first recess and the second recess defines an upper leg and a lower leg extending in the circumferential direction and an intermediate leg extending in the axial direction, leaving a protrusion between the upper leg and the lower leg. This design allows for a secure connection between the base body and the cover element, which holds the cover element in a position covering the gap of the base body, and allows for an additional labyrinth seal between the base body and the cover element at the outer radial surface, thereby minimizing air leakage.

[0014] According to another embodiment of the present invention, advantageously, the distance between the two protrusions is wider than the width of the gap, and the middle part of the cover element is located between the protrusions. This feature allows the cover element to securely cover the gap, thereby minimizing air leakage through the gap.

[0015] According to another embodiment of the present invention, advantageously, the cover element is in the shape of an H with a middle part and first and second lateral parts each having a third recess. This design allows for a secure connection between the base body and the cover element, which holds the cover element in a position covering the gap of the base body, and allows for an additional labyrinth seal between the base body and the cover element on both lateral sides at the outer radial surface, further minimizing air leakage.

[0016] According to another embodiment of the present invention, advantageously, the first recess at the first end and the second recess at the second end produce a flat, cylindrical, conical or a combination thereof surface. This feature allows for better adaptation between the base body and the cover element and allows for easier manufacturing of the two components.

[0017] The object regarding the piston is solved by the features of claim 9.

[0018] An exemplary embodiment of the invention relates to a piston of an internal combustion engine, which has a substantially cylindrical piston body, which has at least one circumferential groove on the radially outer surface of the piston body, and at least one piston ring assembly is arranged in at least one groove, and the piston ring assembly is similar to the features of the piston ring assembly according to the invention.

[0019] The object regarding the internal combustion engine is solved by the features of claim 10.

[0020] An exemplary embodiment of the invention relates to an internal combustion engine having at least one piston according to the invention.

[0021] Further advantageous designs are described by the following description of the drawings and the dependent claims. Description of the Drawings

[0022] Hereinafter, the invention will be further explained based on a plurality of exemplary embodiments using the drawings.

[0023] In the drawings:

[0024] Figure 1 is a perspective depiction of a piston with piston rings of an internal combustion engine arranged according to the prior art to explain the background of the inventive piston ring assembly,

[0025] Figure 2 is a partial perspective depiction of the base body of a piston ring assembly according to an embodiment of the invention,

[0026] Figure 3 is according to Figure 2 a partial top view of the base body,

[0027] Figure 4 is a perspective depiction of a cover element of a piston ring assembly according to an embodiment of the invention,

[0028] Figure 5 is according to Figure 4 a top view of the cover element,

[0029] Figure 6 is a cross-sectional view of a piston ring assembly arranged in a groove of a piston according to an embodiment of the invention,

[0030] Figure 7 is a top view of a piston ring assembly according to an embodiment of the invention, and

[0031] Figure 8 is according to Figure 7 a side view of a piston ring assembly according to an embodiment of the invention.

[0032] List of Reference Numerals

[0033] 1 Piston

[0034] 2 Piston Body

[0035] 3 Radial Outer Surface

[0036] 4 Piston Ring

[0037] 5 Groove

[0038] 6 Inner Surface

[0039] 7 Cylinder

[0040] 10 Piston Ring Assembly

[0041] 11 Groove

[0042] 12 Piston

[0043] 13 Internal Combustion Engine

[0044] 14 Cylinder

[0045] 15 Substrate

[0046] 16 Cover Element

[0047] 17 Gap

[0048] 18 First End

[0049] 19 Second End

[0050] 20 Radial Outer Surface

[0051] 21 Radial Inner Surface

[0052] 22 First Axial Surface

[0053] 23 Second Axial Surface

[0054] 24 First Recess

[0055] 25 Second Recess

[0056] 26 Protrusion

[0057] 27 Surface

[0058] 28 Radial Outer Surface

[0059] 29 Upper Leg

[0060] 30 Lower Leg

[0061] 31 Intermediate Leg

[0062] 32 Surface

[0063] 33 First Lateral Portion

[0064] 34 Middle part

[0065] 35 Second lateral part

[0066] 36 Third concave part Detailed implementation mode

[0067] Figure 1 Fig. 1 shows a piston 1 according to the prior art, which piston 1 has a piston body 2 having a radial outer surface 3 in which grooves 5 are provided at different axial positions. In the grooves 5, piston rings 4 are arranged to contact the inner surface 6 of a cylinder 7, and the piston 1 is arranged in the cylinder 7. Such piston rings 4 usually have gaps to facilitate better assembly of the piston rings 4 within the grooves 5, which results in unwanted gas leakage and oil leakage.

[0068] Figures 2 to 8 Fig. 2 shows different depictions of a piston ring assembly 10 for being arranged in a groove 11 of a piston 12 of an internal combustion engine 13 according to an embodiment of the present invention, see Figure 6 . The piston 12 is arranged in a cylinder 14 of the internal combustion engine 13 for reciprocating movement of the piston 12 within the cylinder 14.

[0069] Compared with a standard piston ring 4 having an open gap, the piston ring assembly 10 of the present invention can prevent or reduce gas leakage and oil leakage.

[0070] The piston ring assembly 10 according to an embodiment of the present invention comprises an annular base body 15 according to Figure 2 , 3 and 6 and a cover element 16 according to Figures 4 to 8 . According to this embodiment, the piston ring assembly 10 only comprises two components. It may also have other components not shown.

[0071] The annular base body 15 of the piston ring assembly 10 has a gap 17 which allows the base body 15 to have an open annular structure which allows the base body 15 to be easily assembled in the groove 11 of the piston 12.

[0072] The cover element 16 is designed and arranged to be able to cover the gap 17 of the base body 15.

[0073] According to Figure 1 , 2 , 7 and 8, the annular base body 15 has a first end 18 and a second end 19, and these two ends 18, 19 are arranged adjacent to each other and separated by the gap 17.

[0074] The base body 15 further has a radial outer surface 20 and a radial inner surface 21, and the base body 15 has a first axial surface 22 and a second axial surface 23, thereby defining the base body 15 as an annular base body 15.

[0075] For example, as Figure 2 and 3 seen in, the base body 15 has a first recess 24 at the first end 18, and the base body 15 has a second recess 25 at the second end 19, such that the first recess 24 and the second recess 25 leave corresponding protrusions 26 at the first end 18 and at the second end 19.

[0076] The protrusions 26 are connected to the part of the base body 15 that is made without the recesses 24, 25, such that the protrusions 26 appear to grow in the circumferential direction from the part made without the recesses 24, 25 to the ends 18, 19 having the recesses 24, 25.

[0077] The protrusions 26 project in the radial direction from the face 27 of the first recess 24 and from the second recess 25. The radially outer surface 28 of the protrusions 26 is aligned with the radially outer surface 20 of the annular base body 15 so as to define the outer surface of the base body 15 to contact the inner surface 21 of the cylinder 14 of the internal combustion engine 13.

[0078] The radial depth l of the first recess 24 at the first end 18 and the second recess 25 at the second end 19 of the annular base body 15 is less than the radial depth L of the base body 15, in particular less than half of the radial depth L of the base body 15. Thus, the stability of the base body 15 is ensured.

[0079] As Figure 2 seen in, the shapes of the first recess 24 at the first end 18 and the second recess 25 at the second end 19 are at least almost C-shaped. The first recess 24 and the second recess 25 each define an upper leg 29 and a lower leg 30 extending in the circumferential direction, and an intermediate leg 31 extending in the axial direction, which leaves the protrusion 26 between the upper leg 29 and the lower leg 30.

[0080] The first recess 24 at the first end 18 and the second recess 25 at the second end 19 produce a surface 32 that is planar, cylindrical, conical, or a combination of these.

[0081] The distance a between the two protrusions 26 is wider than the width of the gap 17. The distance a is equal to the width of the gap plus the width of the intermediate leg 31 of the first end 18 plus the width of the intermediate leg 31 of the second end 19.

[0082] The width of the intermediate leg 31 of the first end 18 is preferably the same as the width of the intermediate leg 31 of the second end 19. According to another embodiment, the width of the intermediate leg 31 of the first end 18 may not be the same as the width of the intermediate leg 31 of the second end 19.

[0083] The cover element 16 has a first lateral part 33, a middle part 34, and a second lateral part 35. The middle part 34 is located between the lateral parts 33, 35.

[0084] As can be seen from Figure 4 it, the first lateral part 33 and the second lateral part 35 each have a third recess 36.

[0085] In the assembled state, for example, see Figures 6 to 8 , the cover element 16 is located at the base body 15 such that the middle part 34 of the cover element 16 covers the gap 17 of the base body 15, and each projection 26 of the end parts 18, 19 of the base body 15 is located in the third recess 36 of the lateral parts 33, 35 of the cover element 16.

[0086] The cover element 16 is in an H shape with the middle part 34 and the first lateral part 33 and the second lateral part 35 each having a third recess 36. In the assembled state, the middle part 34 of the cover element 16 is located between the projections 26. The radial extension dimension b of the middle part 34 is wider than the radial extension dimension c of the lateral parts 33, 35.

[0087] According to Figure 6 , the piston ring assembly 10 is arranged in the groove 11 of the piston 12 such that parts of the base body 15 and the cover element 16 are located within the groove 11 and overlap the boundary of the groove 11 to create a labyrinth seal between the piston ring assembly 10 and the groove 11. The radial outer surfaces 20 of the base body 15 and the cover element 16 contact, or almost contact, the inner surface (so-called side wall) of the cylinder 14.

[0088] The piston ring assembly 10 is made of a base material of steel, cast iron, or polymer based on a chromium composition between 10% and 18%.

[0089] In addition, the piston ring assembly 10 can be made such that at least one surface of each part of the base body 15 and the cover element 16 has a surface hardening layer with a hardness higher than that of the base material.

[0090] Such a hardening layer can be a gas nitride layer.

[0091] In addition, a surface coating applied by PVD (physical vapor deposition) can be provided. The coating can have a thickness between 6 μm and 60 μm.

[0092] The surface hardening can be a DLC coating with a thickness between 3 μm and 60 μm.

[0093] From a manufacturing perspective, the method of manufacturing the base body 15 can be such that the gap 17 and / or the axial recesses 24, 25 are machined in the axial direction.

[0094] The method of manufacturing the base body 15 and / or the cover element 16 can be to manufacture by bending a wire and then cutting the wire into small parts with a required perimeter.

Claims

1. A piston ring assembly (10), comprising an annular base (15) having a gap (17), and comprising a cover element (16) covering the gap (17) of the base (15), wherein the annular base (15) has a first end (18) and a second end (19), the first end (18) and the second end (19) being arranged adjacent to each other and separated by the gap (17), the base (15) having a radial outer face (20, 28) and a radial inner face (21), the base (15) having a first axial face (22) and a second axial face (23), and the base (15) having a first recess (24) at the first end (18) and a second recess (25) at the second end (19), such that the first recess The first and second recesses (24 and 25) of the cover element (16) leave corresponding protrusions (26) at the first end (18) and at the second end (19), and the cover element (16) has a first lateral portion (33), a middle portion (34) and a second lateral portion (35), the middle portion (34) being located between the lateral portions, the first lateral portion (33) and the second lateral portion (35) each having a third recess (36), and the cover element (16) is located at the base (15) so that the middle portion (34) of the cover element (16) covers the gap (17) of the base (15), and each protrusion (26) of the ends (18, 19) of the base (15) is located in the third recess (36) of the lateral portion of the cover element (16).

2. The piston ring assembly (10) according to claim 1, characterized in that: The protrusion (26) protrudes in a radial direction from a surface (27) of the first recess (24) and from the second recess (25).

3. The piston ring assembly (10) according to claim 1 or 2, characterized in that: The radially outer surface (20, 28) of the protrusion (26) is aligned with the radially outer surface (20, 28) of the annular base (15).

4. The piston ring assembly (10) according to claim 1, 2 or 3, characterized in that: The radial depth of the first recess (24) at the first end (18) of the annular base (15) and the second recess (25) at the second end (19) is smaller than the radial depth of the base (15), in particular, smaller than half of the radial depth of the base (15).

5. The piston ring assembly (10) according to claim 1, 2, 3 or 4, characterized in that The first recess (24) at the first end (18) and the second recess (25) at the second end (19) are C-shaped, and the first recess (24) and the second recess (25) each define an upper leg (29) and a lower leg (30) extending in a circumferential direction and an intermediate leg (31) extending in an axial direction, leaving the protrusion (26) between the upper leg (28) and the lower leg (30).

6. The piston ring assembly (10) according to claim 1, 2, 3, 4 or 5, characterized in that The distance (a) between the two protrusions (26) is wider than the width of the gap (17), and the middle portion (34) of the cover element (16) is located between the protrusions (26).

7. The piston ring assembly (10) according to any one of the preceding claims, characterized in that The cover element (16) is H-shaped with the middle portion (34) and the first lateral portion (33) and the second lateral portion (35) each having the third recess (36).

8. The piston ring assembly (10) according to any one of the preceding claims, characterized in that The first recess (24) at the first end (18) and the second recess (25) at the second end (19) create a surface (32) that is planar, cylindrical, conical, or a combination thereof.

9. A piston (12) of an internal combustion engine (13), the piston (12) having a piston body, the piston body having at least one circumferential groove (11) and at least one piston ring assembly (10) arranged in at least one of the grooves (11), characterized in that The piston ring assembly (10) has the features according to at least one of the preceding claims.

10. An internal combustion engine (13) having at least one piston (12) according to claim 9.

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