Piston ring assembly

Abstract

The invention relates to a piston ring assembly (10) comprising a first annular ring element (15) having a first gap and further comprising a second annular ring element (16) having a second gap, the first annular ring element (15) being located above the second annular ring element (16) and contacting the second annular ring element (16) such that the first gap and the second gap are misaligned, the first annular ring element (15) has a first radially outer face (17) having a first outer radius (R1) and the second ring element (16) has a second radially outer face (18) having a second outer radius (R2) such that the second outer radius (R2) is greater than or equal to the first outer radius (R1).

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 in a cylinder such that the top surface of the piston defines a chamber for combustion. Due to the increasing concerns about the environmental problems of pollutants emitted 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 using fossil fuels such as gasoline, natural gas, liquefied petroleum gas, and diesel, and thus they have a significant environmental impact. New developments are dedicated to new carbon-neutral fuels such as hydrogen, whose combustion produces water vapor.

[0003] Using new fuels generally requires improvements to the internal combustion engine so that the engine operates safely, efficiently, and durably. This is the case with hydrogen, which has different characteristics 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 in other fuels because 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. Moreover, the oil vapor in the combustion chamber alters the air / fuel mixture, which may cause the engine compression to be 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 make the assembly in the piston grooves easier and provide tension to the rings so that the rings remain in contact with the cylinder. Thus, gas can flow through the gaps. Such an effect is called "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 part and a lock part, and the lock part 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 part cannot lock the concave locking end to the convex locking end, and the piston ring will open the lock part, resulting in air leakage and likely damage to the lock part 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 a first annular ring element having a first gap, and also includes a second annular ring element having a second gap. The first annular ring element is located above and in contact with the second annular ring element such that the first gap and the second gap are not aligned. The first annular ring element has a first outer surface with a first outer radius, and the second ring element has a second outer surface with a second outer radius such that the second outer radius is greater than or equal to the first outer radius. Such a piston ring assembly covers the gaps of the two annular ring elements by a corresponding other annular ring element, and in the case where the radii of the two annular ring elements are different, only one ring element contacts the inner surface of the cylinder, reducing the friction when slidingly contacting the inner surface of the cylinder.

[0010] According to an embodiment of the present invention, it is advantageous that the first ring element and the second ring element are twisted at an angle such that the first gap is not aligned with the second gap, in particular the first ring element is twisted relative to the second ring element by an angle of about 30° to 180°, preferably an angle of about 90° to 180°. The twist is applied around the axial direction such that the first ring element is rotated relative to the second ring element around the axial direction, causing the first gap and the second gap to be offset from each other and no longer aligned. In the case of an angle of 30° to 180°, it can be ensured that the two gaps are not aligned and they are far from each other, creating a labyrinth seal between them.

[0011] According to another embodiment of the present invention, advantageously, the second ring element has a second radially outer surface, a second radially inner surface, a second axially lower surface, and a second axially upper surface, and the second axially upper surface contacts the first annular ring element. With this design, the second ring element serves as a seal within the cylinder and as a support for the first ring element, which holds the second ring element in place.

[0012] According to one embodiment of the present invention, advantageously, the second radially outer surface is arranged at a right angle to the second axially lower surface, and / or the second radially inner surface is arranged at a right angle to the second axially lower surface, and / or the second axially upper surface is an inclined second axially upper surface, which is arranged at an angle less than 90° with respect to the second radially outer surface, and the second axially upper surface is arranged at an angle greater than 90° with respect to the second radially inner surface. The design with the inclined axially upper surface brings about a self-centering effect between the first ring element and the second ring element.

[0013] According to one embodiment of the present invention, advantageously, the first ring element has a first radially outer surface, a first radially inner surface, a first axially lower surface, and a first axially upper surface, and the first axially lower surface contacts the second annular ring element. With this design, the first ring element serves as a support for the second ring element, which holds the second ring element in place.

[0014] Furthermore, advantageously, the first ring element also has a third radially outer surface and a third axially lower surface, such that the third radially outer surface contacts the second radially inner surface, and the third axially lower surface is at the level of the second axially lower surface. This design brings about a stable arrangement of the first ring element within the groove of the piston and a stable support of the second ring element.

[0015] Furthermore, advantageously, the first radially outer surface is arranged at a right angle to the first axially upper surface and / or the first radially inner surface is arranged at a right angle to the first axially upper surface and / or the first axially lower surface is an inclined first axially lower surface, which is arranged at an angle greater than 90° with respect to the first radially outer surface and / or the first axially lower surface is arranged at an angle less than 90° with respect to the first radially inner surface and / or the first axially lower surface is arranged at a right angle to the third axially lower surface. The design with the inclined axially lower surface brings about a self-centering effect between the first ring element and the second ring element.

[0016] According to one embodiment of the present invention, advantageously, one of the first annular ring element and the second annular ring element has at least one protrusion, and the other of the first annular ring element and the second annular ring element has at least one recess, such that the protrusion projects into the recess to lock the first annular ring element to the second annular ring element. This design enables a form-locking connection between the first ring element and the second ring element to prevent rotation of one ring element relative to the other without inadvertently aligning the two gaps of the two ring elements.

[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, the piston having a substantially cylindrical piston body having at least one circumferential groove on a radially outer surface of the piston body, and at least one piston ring assembly being arranged in at least one groove, the piston ring assembly being 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 several exemplary embodiments with reference to the drawings.

[0023] In the drawings:

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

[0025] Figure 2 is a sectional depiction of a piston ring assembly according to an embodiment of the invention,

[0026] Figure 3 is according to Figure 2 a perspective depiction of the piston ring assembly, and

[0027] Figure 4 is a sectional view of a piston ring assembly arranged in a groove of a piston according to an embodiment of the invention.

[0028] List of Reference Numerals

[0029] 1 Piston

[0030] 2 Piston body

[0031] 3 Radially outer surface

[0032] 4 Piston ring

[0033] 5 Groove

[0034] 6 Inner surface

[0035] 7 Cylinder

[0036] 10 Piston ring assembly

[0037] 11 Groove

[0038] 12 Piston

[0039] 13 Internal combustion engine

[0040] 14 Cylinder

[0041] 15 First annular ring element

[0042] 16 Second annular ring element

[0043] 17 First radial outer surface

[0044] 18 Second radial outer surface

[0045] 19 Inner surface

[0046] 20 Second radial inner surface

[0047] 21 Second axial lower surface

[0048] 22 Second axial upper surface

[0049] 23 First radial inner surface

[0050] 24 First axial lower surface

[0051] 25 First axial upper surface

[0052] 26 Third radial outer surface

[0053] 27 Third axial lower surface Detailed implementation mode

[0054] Figure 1 Shows a piston 1 according to the prior art, the piston 1 having a piston body 2, the 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 the cylinder 7, and the piston 1 is arranged in the cylinder 7. Such piston rings 4 usually have gaps for better assembly of the piston rings 4 within the grooves 5, which results in unwanted leakage of air and oil.

[0055] Figures 2 to 4 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 4 . 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.

[0056] 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.

[0057] The piston ring assembly 10 according to an embodiment of the present invention includes a first annular ring element 15 and a second annular ring element 16.

[0058] The first annular ring element 15 has a first gap and is made as an open ring element 15. The second annular ring element 16 includes a second gap and is also made as an open ring element 16. The presence of the gaps in the corresponding annular ring elements 15, 16 supports the application of the ring elements in the groove 11 of the piston 12.

[0059] As Figures 2 to 4 can be seen, the first annular ring element 15 is located above the second annular ring element 16 and contacts the second annular ring element 16 such that the first gap and the second gap are not aligned. This arrangement causes the gaps of the ring elements 15, 16 to be blocked by the corresponding other ring element 16, 15.

[0060] In addition, the first annular ring element 15 has a first radially outer surface 17 having a first outer radius R1, and the second ring element 16 has a second radially outer surface 18 having a second outer radius R2 such that the second outer radius R2 is greater than or equal to the first outer radius R2. This results in the fact that in the case where R2 is greater than R1, only the second ring element 16 contacts the inner surface 19 of the cylinder 14, and the first ring element 15 does not contact the inner surface 19 of the cylinder 14.

[0061] To keep the gaps of the two ring elements 15, 16 away from each other, the first ring element 15 and the second ring element 16 are arranged in such a way that they are twisted at a certain angle such that the first gap is not aligned with the second gap, in particular, the first ring element 15 is rotated relative to the second ring element 16 by an angle of about 30° to 180°. This causes the two corresponding gaps of the two corresponding annular ring elements 15, 16 to be stably blocked by the corresponding other annular ring element 16, 15.

[0062] As can be seen from the drawings, the second annular ring element 16 having the second radially outer surface 18 also has a second radially inner surface 20, a second axially lower surface 21, and a second axially upper surface 22. The second annular ring element 16 is arranged such that the second axially upper surface 22 contacts the first annular ring element 15.

[0063] Furthermore, the second radially outer face 18 is arranged at a right angle to the second axially lower face 21, and the second radially inner face 20 is arranged at a right angle to the second axially lower face 21, and the second axially upper face 22 is an inclined second axially upper face 22 which is arranged at an angle α less than 90° with respect to the second radially outer face 18, and the second axially upper face 22 is arranged at an angle β greater than 90° with respect to the second radially inner face 20. This results in an inclined face 22 at the periphery of the second annular ring element 16.

[0064] The first annular ring element 15 is designed such that it has a first radially outer face 17, a first radially inner face 23, a first axially lower face 24 and a first axially upper face 25. The first axially lower face 24 contacts the second annular ring element 16 at the second axially upper face 22.

[0065] Furthermore, the first annular ring element 15 has a third radially outer face 26 and a third axially lower face 27 such that the third radially outer face 26 contacts the second radially inner face 20, and the third axially lower face 27 is at or above the level of the second axially lower face 21. This may lead to the fact that the first annular ring element 15 is supported by the second annular ring element 16 rather than by the groove 11 of the piston 12.

[0066] Furthermore, the first radially outer face 17 is arranged at a right angle to the first axially upper face 25, and the first radially inner face 23 is arranged at a right angle to the first axially upper face 25, and the first axially lower face 24 is an inclined first axially lower face 24 which is arranged at an angle γ greater than 90° with respect to the first radially outer face 17, and the first axially lower face 24 is arranged at an angle δ less than 90° with respect to the first radially inner face 23, and the first axially lower face 24 is arranged at an angle greater than 90 degrees with respect to the third radially outer face 26 arrangement, and the third radially outer face 26 is arranged at a right angle to the third axially lower face 27.

[0067] In order to lock the two annular ring elements 15, 16 to each other, they can be designed such that one of the first annular ring element 15 and the second annular ring element 16 has at least one projection, and the other of the first annular ring element 15 and the second annular ring element 16 has at least one recess such that the projection projects into the recess to lock the first annular ring element 15 to the second annular ring element 16 in the circumferential direction and / or the radial direction.

[0068] Thus, the piston ring assembly 10 for an internal combustion engine 13 according to the invention comprises two annular tensionable ring elements 15, 16 which have angularly spaced corresponding gaps such that each annular ring element 15, 16 blocks the gap of the corresponding other annular ring element 16, 15.

[0069] The lower annular ring element 16 creates most of the gas sealing effect of the piston ring assembly 10, as its outer annular radial surface 18 contacts the cylinder 14, except in the clearance area, and this clearance is blocked by another annular ring element 15. The upper annular ring element 15 also has a clearance blocked by the lower annular ring element 16.

[0070] The inclined contact surface between the upper annular ring element 15 and the lower annular ring element 16 improves the tension transmission between the ring elements 15, 16 and generates a downward force component, thus pushing the piston ring assembly 10 towards the bottom part of the groove 11 of the piston 12. Therefore, compared with the design where the contact surface is perpendicular to the ring axis and the traditional piston ring 4 with only one component, the ring flutter in the piston groove is reduced.

[0071] The intersection of the two inclined surfaces of the annular ring elements 15, 16 can have an undercut to facilitate the manufacture of the annular ring elements 15, 16 without negative impact on the performance of the ring assembly. In the inclined surfaces of the annular ring elements 15, 16, there may be at least one additional protrusion or projection and at least one recessed interface to improve the sealing ability of the assembly by restricting the flow of gas between the rings.

[0072] According to an embodiment of the present invention, both annular piston ring elements 15, 16 have a tangential force in the range of 5 and 25 Newtons, and the top annular ring element 15 has a higher tangential force than the lower annular ring element 16.

[0073] The dimensions and weights of the annular ring elements 15, 16 can be such that the upper annular ring element 15 has a mass 1.1 to 2.8 times that of the lower annular ring element 16. Compared with the upper annular ring element 15, the lower annular ring element 16 has smaller radial thickness and height dimensions.

[0074] The piston ring assembly 10 can be manufactured such that at least a nitriding surface treatment is applied to at least one or both of the annular ring elements 15, 16.

[0075] In addition, it may be advantageous that at least one of the surfaces of one or both of the annular ring elements 15, 16 includes a coating applied by a PVD (Physical Vapor Deposition) process generated by a cathode arc source. Alternatively, other coatings are also possible.

[0076] The coating can have a preferred thickness between 10μm and 60μm.

[0077] The annular ring elements 15, 16 can be made of the same material or different materials. The base material of the annular ring elements 15, 16 is made of steel, carbon steel or cast iron with 10% to 17% chromium. The base material can be made of nitrided cast iron.

[0078] If the base material is made of carbon steel or steel with 10% to 17% chromium, the piston ring assembly 10 can be manufactured by winding wire, or if the base material is cast iron, it can be manufactured by turning. After winding or turning, the two annular ring elements 15, 16 can be ground and machined on the side, outer surface, and inner surface.

[0079] If the annular ring elements 15, 16 can have protrusions and / or depressions, the method of manufacturing the protrusions and depressions is: winding wire having a protrusion or depression geometry included in its cross-section, and grinding or machining the protrusions or depressions.

[0080] Preferably, the steel base material used is gas nitrided at a temperature of 400 °C to 700 °C, and the nitride layer thickness is between 6 μm and 150 μm.

[0081] In addition, the two-piece piston ring assembly 10 can be manufactured such that at least one surface includes a PVD coating deposited at a temperature between 300 °C and 700 °C and has a coating thickness of about 10 μm to 60 μm.

Claims

1. A piston ring assembly (10), comprising a first annular ring element (15) having a first gap, and further comprising a second annular ring element (16) having a second gap, wherein the first annular ring element (15) is located above the second annular ring element (16) and contacts the second annular ring element (16), such that the first gap and the second gap are not aligned, the first annular ring element (15) having a first radial outer surface (17) having a first outer radius (R1), and the second ring element (16) having a second radial outer surface (18) having a second outer radius (R2), such that the second outer radius (R2) is greater than or equal to the first outer radius (R1).

2. The piston ring assembly (10) according to claim 1, characterized in that: The first ring element (15) and the second ring element (16) are twisted at an angle such that the first gap is not aligned with the second gap, in particular the first ring element (15) is twisted relative to the second ring element (16) at an angle of about 30° to 180°, preferably about 90° to 180°.

3. The piston ring assembly (10) according to claim 1 or 2, characterized in that: The second ring element (16) has a second radial outer surface (18), a second radial inner surface (20), a second axial lower surface (21) and a second axial upper surface (22), and the second axial upper surface (22) contacts the first annular ring element (15).

4. The piston ring assembly (10) according to claim 3, characterized in that: The second radial outer surface (18) is arranged at a right angle to the second axial lower surface (21), and / or the second radial inner surface (20) is arranged at a right angle to the second axial lower surface (21), and / or the second axial upper surface (22) is an inclined second axial upper surface (22), which is arranged at an angle less than 90° relative to the second radial outer surface (18), and the second axial upper surface (22) is arranged at an angle greater than 90° relative to the second radial inner surface (20).

5. The piston ring assembly (10) according to claim 1, 2, 3 or 4, characterized in that The first ring element (15) has the first radial outer surface (17), a first radial inner surface (23), a first axial lower surface (24) and a first axial upper surface (25), and the first axial lower surface (24) contacts the second annular ring element (16).

6. The piston ring assembly (10) according to claim 5, characterized in that The first ring element (15) also has a third radial outer surface (26) and a third axial lower surface (27) such that the third radial outer surface (26) contacts the second radial inner surface (20) and the third axial lower surface (27) is at the level of the second radial lower surface (21) or above the level of the second radial lower surface (21).

7. The piston ring assembly (10) according to any one of the preceding claims, characterized in that The first radial outer surface (17) is arranged at a right angle to the first axial upper surface (25), and / or the first radial inner surface (23) is arranged at a right angle to the first axial upper surface (25), and / or the first axial lower surface (24) is an inclined first axial lower surface (24), which is arranged at an angle greater than 90° relative to the first radial outer surface (17), and / or the first axial lower surface (24) is arranged at an angle less than 90° relative to the first radial inner surface (23), and / or the first axial lower surface (24) is arranged at an angle greater than 90° relative to the third radial outer surface (26), and / or the third radial outer surface (26) is arranged at a right angle to the third axial lower surface (27).

8. The piston ring assembly (10) according to any one of the preceding claims, characterized in that One of the first annular ring element (15) and the second annular ring element (16) has at least one protrusion, and the other of the first annular ring element (15) and the second annular ring element (16) has at least one recess, so that the protrusion protrudes into the recess to lock the first annular ring element (15) to the second annular ring element (16).

9. A piston (12) of an internal combustion engine (13), the piston (12) having a piston body (2), the piston body (2) 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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