Piston ring and internal combustion engine

Abstract

The invention relates to a piston ring (1) for an internal combustion engine (20). The invention relates to a piston ring (1) having an annular base body (2) which has a central longitudinal axis (M) extending in an axial direction (A) and which extends circumferentially about the central longitudinal axis (M) in a circumferential direction (U) of the base body (2) perpendicular to the axial direction (A). The base body (2) also has an interruption structure (4) in the circumferential direction (U) forming a joining structure (3). The axial end face (6) of the base body (2) comprises a radially outer surface portion (7) extending perpendicular to the central longitudinal axis (M). The radially outer surface portion (7) merges radially inward in the radial direction (R) of the base body (2) to a radially inner surface portion (8). The radially inner surface portion (8) is arranged at an obtuse angle (alpha) to the central longitudinal axis (M). The invention also relates to an internal combustion engine (20) for a motor vehicle.

Description

Technical Field

[0001] The invention relates to a piston ring for an internal combustion engine and an internal combustion engine having such a piston ring. Background Art

[0002] Conventional piston rings of known internal combustion engines induce different wear mechanisms in piston grooves including: step wear, trumpet wear and flat wear.

[0003] A well-known solution to reduce this type of wear is to increase the strength of the material of the piston groove, for example by laser hardening the piston. However, this has proven to be a very expensive and difficult solution to implement. Summary of the invention

[0004] It is therefore an object of the present invention to provide an improved piston ring by which the occurrence of wear in the piston groove accommodating the piston ring can be reduced.

[0005] This object is achieved by the subject matter of the independent claims. Preferred embodiments are the subject matter of the dependent claims.

[0006] The piston ring for an internal combustion engine according to the present invention comprises an annular base body, the annular base body having a central longitudinal axis extending in the axial direction, and the annular base body extending around the central longitudinal axis in the circumferential direction of the base body perpendicular to the axial direction. The base body has an interruption structure in the circumferential direction forming a joining structure. The interruption structure or the joining structure is defined in the circumferential direction by the first joining side and the second joining side of the base body. The end face of the base body axially facing the axial direction surrounds a radial outer surface portion extending perpendicular to the central longitudinal axis. The surface portion merges radially inwardly into the radial inner surface portion along the radial direction of the base body. The radial inner surface portion is arranged at an obtuse angle to the central longitudinal axis. According to the present invention, the radial outer surface portion has a maximum extension scale of 0.3 mm measured in the radial direction. Such a maximum extension scale significantly reduces the wear of the piston groove.

[0007] Furthermore, the (first) edge formed between the first engaging side and the end face has a (first) chamfer, the axial extension of the (first) chamfer measured in the axial direction being at most 0.16 mm, preferably about 0.06 mm. Furthermore, the extension of the (first) chamfer measured in the circumferential direction being at most 0.16 mm, preferably about 0.05 mm. By means of such an edge design, the occurrence of wear on the piston groove can be further reduced. Furthermore, a protective coating is arranged on the outer circumference of the annular base body.

[0008] Preferably, the base material of the substrate may be stainless steel, and the base material may contain 10-17% chromium.

[0009] In a preferred embodiment, the (second) edge formed between the second joining side surface and the axial end surface has a second chamfer, and the second chamfer has an axial extension dimension of a maximum of 0.16 mm, preferably about 0.06 mm, measured in the axial direction, and an extension dimension of a maximum of 0.16 mm, preferably about 0.05 mm, measured in the circumferential direction.

[0010] According to another preferred embodiment, in order to reduce the occurrence of adhesive wear, i.e. the material transfer from the piston groove material to the lower side of the piston ring, an additional protective coating made of a polymer or Cr plating or DLC film is arranged on the axial end face of the annular base of the piston ring. The coating material may include a polymer or consist of such a polymer, metallic chromium or a carbon-based film. The coating material based on a polymer structure may contain WC (tungsten carbide) particles.

[0011] It is particularly advantageous if the protective coating comprises or is a DLC coating. Such a DLC coating has not only a very high hardness but also a particularly low coefficient of friction, which is particularly advantageous for driving piston rings in internal combustion engines, for example by increasing the anti-seizure properties. It is particularly preferred that more than 50% of the bonds formed in the amorphous carbon of the DLC protective coating are formed by sp2 hybrid bonds. They provide advantageous sliding properties for the sliding element. Alternatively or additionally, in this variant, 20% to 45% of the bonds formed in the amorphous carbon of the DLC protective coating are formed by sp3 bonds. Since the mechanical properties of the sp3 bonds determine the highest wear resistance of the DLC protective coating, the selected proportion of this bond form ensures the high hardness and excellent low friction properties of the DLC protective coating.

[0012] In another preferred embodiment, the coating material of the protective coating may include or consist of a ceramic material, in particular a PVD ceramic coating based on nitrides. The coating material may be, for example, PVD chromium nitride (CrN), chromium aluminum nitride (CrAlN), chromium aluminum nitride multilayer (CrAlN / CrAlN), chromium nitride niobium nitride multilayer (NbN / CrN), diamond-like carbon film (DLC), the purpose of which is to improve wear resistance and extend the service life of the piston ring.

[0013] According to an advantageous further development, an adhesion promoting layer containing chromium (Cr) or consisting of chromium (Cr) can be sandwiched between the protective coating and the substrate. In this way, the adhesion of the protective coating to the piston ring substrate can be significantly improved.

[0014] Particularly advantageously, the layer thickness of the additional protective coating can be between 5 μm and 40 μm, preferably between 15 μm and 30 μm.

[0015] According to a further advantageous development, the axial end surface has two texture sections which extend in the circumferential direction over a circumferential angle of at most 35°, preferably approximately 25°, starting from a central position of the engagement structure relative to the circumferential direction.

[0016] In this further development, the end face has a texture in each of the two texture sections. By means of the texture, the area around the engagement structure of the piston ring which is subject to particularly high mechanical loads during use in internal combustion engines can be additionally protected from wear.

[0017] Particularly preferably, the two textures can each be formed by a plurality of grooves, which are preferably arranged in a grid-like manner on the surface of the end face, preferably with a rounded, particularly preferably circular geometry. The texture formed in this way can be produced in a particularly simple manner, in particular by irradiation with a laser beam.

[0018] In another preferred embodiment, the depth of at least one, preferably several, particularly preferably all grooves measured perpendicular to the surface is between 5 μm and 20 μm, preferably between 8 μm and 12 μm, preferably about 10 μm. In this embodiment, the groove diameter of at least one, preferably several, particularly preferably all grooves is between 30 μm and 90 μm, preferably between 50 μm and 70 μm, preferably about 60 μm.

[0019] Particularly advantageously, the surface proportion of the two texture parts covered by the grooves can be between 15% and 35%.

[0020] The invention also relates to an internal combustion engine for a motor vehicle, the internal combustion engine having at least one cylinder surrounding a combustion chamber in which a piston is adjustably arranged. At least one annular groove is formed on the outer circumference of the piston, in which the piston ring according to the invention can be partially arranged or partially received, so that the piston ring is supported on both the cylinder and the piston. The advantages of the piston ring according to the invention are thus transferred to the internal combustion engine according to the invention. The axial end face of the piston ring in at least one annular groove is arranged axially away from the combustion chamber.

[0021] In a preferred embodiment of the internal combustion engine according to the present invention, a first annular groove, a second annular groove and a third annular groove are arranged axially at intervals on the outer circumference of the piston. The first annular groove faces the combustion chamber axially, and the second annular groove is axially arranged between the first annular groove and the third annular groove. The piston ring according to the present invention is arranged in the first annular groove.

[0022] Further important features and advantages of the invention emerge from the dependent claims, the drawings and the description of the figures with reference to the drawings.

[0023] It is understood that the features mentioned above and those still to be explained below can be used not only in the combination indicated in each case but also in other combinations or alone, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Examples of preferred embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein the same reference numerals refer to the same or similar or functionally identical components.

[0025] The accompanying drawings schematically show:

[0026] Figure 1 shows an axial plan view of an example of a piston ring according to the invention,

[0027] Figure 2 Shows Figure 1 A partial perspective view of the piston ring in

[0028] Figure 3a , 3b 1 and 2 show respectively a plan view of the outer circumference 11 of the piston ring in the region of the first engaging side and the second engaging side of the engaging structure along the radial direction R,

[0029] Figure 4 A rough schematic diagram showing the surface texture of two side areas of the joined structure,

[0030] Figure 5 An axial longitudinal section through an example of an internal combustion engine according to the invention with a piston ring according to the invention is shown. DETAILED DESCRIPTION

[0031] Figure 1 A highly simplified top view in the axial direction A shows an example of a piston ring 1 for an internal combustion engine according to the invention, Figure 2 yes Figure 1 A partial perspective view of a piston ring.

[0032] according to Figure 1 and Figure 2 The piston ring 1 includes an annular base body 2, which has a central longitudinal axis M extending along the axial direction A, and the annular base body also extends circumferentially around the central longitudinal axis M along a circumferential direction U of the base body 2 perpendicular to the axial direction A. In addition, a radial direction R extends perpendicular to the axial direction A and is also perpendicular to the circumferential direction U away from the central longitudinal axis M orthogonally.

[0033] The base material of the substrate 2 may be stainless steel, and the chromium content in the base material may be 10% to 17%.

[0034] according to Figure 1The base body 2 has an interruption structure 4 in the circumferential direction U which forms a joining structure 3. The interruption structure or joining structure 3 is delimited in the circumferential direction U by a first joining side surface 5a and a second joining side surface 5b of the base body 2.

[0035] from Figure 2 As can be seen in the perspective view of FIG. 2 , the end face 6 of the base body 2 is axially oriented relative to the axial direction A, and the end face 6 includes a radial outer surface portion 7 extending perpendicularly to the central longitudinal axis M. The radial outer surface portion 7 merges radially inwardly into the radial inner surface portion 8 along the radial direction R of the base body 2. The radial inner surface portion 8 is arranged at an obtuse angle α relative to the central longitudinal axis M. Therefore, the radial outer surface portion 7 and the radial inner surface portion 8 are arranged at an obtuse angle θ to each other. According to the present invention, the extension dimension r1 of the radial outer surface portion 7 measured along the radial direction R is at most 0.3 mm.

[0036] Figure 3a and 3b A plan view along the radial direction R of the outer circumference 11 of the base body 2 in the region of the first joining side surface 5 a and the second joining side surface 5 b is shown in each case.

[0037] Therefore, the first bonding side 5a (such as Figure 3a The first edge 12a between the first and second joint sides 5b (see FIG. 1 ) and the end face 6 has a first chamfer 9a, wherein the axial extension x1 of the first chamfer measured in the axial direction is at most 0.16 mm, preferably about 0.06 mm. In addition, the extension y1 of the first chamfer 9a measured in the circumferential direction U is at most 0.16 mm, preferably about 0.05 mm. Accordingly, the second joint side 5b (see FIG. 1 ) is formed with a first chamfer 9a. Figure 3b ) and the axial end face have a second chamfer 9b, the axial extension x2 of the second chamfer measured in the axial direction is at most 0.16 mm, preferably about 0.06 mm, and the radial extension y2 of the second chamfer measured in the circumferential direction U is at most 0.16 mm, preferably about 0.05 mm. Preferably, the first chamfer 9a and the second chamfer 9b can be as follows Figure 3a and Figure 3b The same is formed as shown.

[0038] according to Figure 1 , Figure 2 A protective coating 10a is arranged on the outer periphery 11 of the annular substrate 2. The coating material of the protective coating 10a can be a ceramic material. In this example, the protective coating 10a is formed by a DLC layer. An adhesion promoting layer 13 containing chromium (Cr) can be sandwiched between the protective coating 10a and the substrate 2.

[0039] An additional protective coating 10b is provided on the axial end face 6 of the annular base body 2, and the coating material of the additional protective coating comprises a polymer or chromium (Cr) plating or a DLC film. The layer thickness of the additional protective coating 10b can be between 5 μm and 40 μm, preferably between 15 μm and 25 μm. When the piston ring 1 in the internal combustion engine is working, the axial end face 6 can be the lower surface facing away from the combustion chamber.

[0040] In addition, if Figure 1 As shown, the axial end face 6 may have two texture portions 14a, 14b, which respectively start from the first joint side 5a and the second joint side 5b and extend along the circumferential direction U at a maximum of 35°, preferably about 25°, and the circumferential angles β1, β2 start from the center position 3.1 of the joint structure 3 relative to the circumferential direction U (see Figure 1 ).

[0041] The two textured portions 14a, 14b have Figure 4 The textures 15a, 15b are roughly reproduced in FIG. Figure 4 , the two textures 15a, 15b are each formed by a plurality of grooves 16, which are arranged in a grid-like manner on the surface of the end face 6 and have an annular or circular geometry, such as Figure 4 The surface ratio of both texture parts 14a, 14b covered by grooves 16 may be between 15% and 30% ( Figure 4 ). The groove diameter D of each groove is between 30 μm and 90 μm, preferably between 50 μm and 70 μm, particularly preferably about 60 μm. Independently of this, the depth of each groove 16 measured perpendicular to the surface is between 5 μm and 20 μm, preferably between 8 μm and 12 μm, preferably about 10 μm.

[0042] Figure 5 FIG. 2 shows an application of the piston ring 1 in an internal combustion engine 20. The internal combustion engine 20 comprises a cylinder 21 surrounding a combustion chamber 22 and Figure 5 , a longitudinal section view of the internal combustion engine along the axial direction A is partially shown in FIG. The combustion chamber 22 includes a cylindrical piston ring 1. A cylindrical piston 23 is arranged in the combustion chamber 22 and can be adjusted along the axial direction A. On the outer periphery 24 of the piston 23, three annular grooves 25a, 25b, 25c are arranged axially at intervals. The first annular groove 25a of the three annular grooves 25a-25c is axially facing the combustion chamber 22. The third annular groove 25c of the three annular grooves 25a-25c is axially away from the combustion chamber 22. Therefore, the second annular groove 25b of the three annular grooves 25a-25c is axially arranged between the first annular groove 25a and the third annular groove 25c.

[0043] like Figure 5As shown, each of the three annular grooves 25 a , 25 b , 25 c can be arranged with a corresponding piston ring 26 a , 26 b , 26 c , which is supported radially inwardly on the piston 22 and radially outwardly on the cylinder 21 of the internal combustion engine.

[0044] The piston ring 26a arranged in the first annular groove 25a is the piston ring 1 according to the present invention as described above, which serves as a compression ring. The axial end face 6 of the piston ring 1 is arranged in the first annular groove 25a axially facing away from the combustion chamber 2 .

Claims

1. A piston ring (1), in particular a compression ring, for an internal combustion engine (20), - the piston ring comprises an annular base body (2), the annular base body having a central longitudinal axis (M) extending in an axial direction (A), and the annular base body extends circumferentially around the central longitudinal axis (M) in a circumferential direction (U) of the base body (2) perpendicular to the axial direction (A), and the piston ring also comprises an interruption structure (4) in the circumferential direction (U) forming a joining structure (3), the joining structure being delimited in the circumferential direction (U) by a first joining side surface (5a) and a second joining side surface (5b) of the base body (2), -in, The axial end face (6) of the base body (2) comprises a radial outer surface portion (7), which extends perpendicularly to the central longitudinal axis (M) and merges radially inwardly along the radial direction (R) of the base body (2) into a radial inner surface portion (8), which is arranged at an obtuse angle (α) to the central longitudinal axis (M), - the radially outer surface portion (7) has an extension (r1) measured in the radial direction (R) of at most 0.3 mm, - a (first) edge (12a) formed between the first engaging side surface (5a) and the end surface (6) has a (first) chamfer (9a), the axial extension (x1) of the (first) chamfer (9a) measured in the axial direction (A) being at most 0.16 mm, preferably about 0.06 mm, and the extension (y1) of the (first) chamfer (9a) measured in the circumferential direction (U) being at most 0.16 mm, preferably about 0.05 mm, - A protective coating (10a) is arranged on the outer circumference (11) of the annular base (2).

2. The piston ring according to claim 1, Features The (second) edge (12b) formed between the second joining side surface (5b) and the end surface has a second chamfer (9b), the axial extension dimension (x2) of the second chamfer measured in the axial direction is at most 0.16 mm, preferably about 0.06 mm, and the extension dimension (y2) of the second chamfer measured in the circumferential direction (U) is at most 0.16 mm, preferably about 0.05 mm.

3. The piston ring according to claim 1 or 2, Features The coating material of the protective coating (10a) includes a ceramic material or consists of a ceramic material.

4. The piston ring according to any one of claims 1 to 3, It is characterized in that The protective coating (10a) comprises a nitridation-based PVD ceramic coating or a nitridation-based PVD ceramic coating, or comprises a DLC layer or a DLC layer.

5. Piston ring according to any one of the preceding claims, Features An additional protective coating (10b) is arranged on the axial end surface (6) of the annular base (2), and the additional protective coating includes a polymer as a coating material, or the coating material of the additional protective coating includes a polymer, Cr electroplating or a DLC film.

6. Piston ring according to any one of the preceding claims, Features An adhesion promoting layer (13) is sandwiched between the protective coating (10a) and the substrate (2), and the adhesion promoting layer (13) contains chromium (Cr) or consists of chromium (Cr).

7. Piston ring according to any one of the preceding claims, Features The layer thickness of the additional protective coating (10b) is between 5 μm and 40 μm, preferably between 15 μm and 30 μm.

8. Piston ring according to any one of the preceding claims, Features - the axial end face (6) has two textured sections (14a, 14b), each of which extends in the circumferential direction over a circumferential angle (β1, β2) of at most 35°, preferably about 25°, starting from a center position (3.1) of the engagement structure (3) relative to the circumferential direction (U), - the axial end face (6) has a texture (15a, 15b) in each of the two texture portions (14a, 14b).

9. The piston ring according to claim 8, Features The two textured portions (14a, 14b) are each formed by a plurality of grooves (15) which preferably have a rounded, particularly preferably circular, geometry and are arranged in a grid-like manner on the surface of the axial end face (6).

10. The piston ring according to claim 9, Features at least one, preferably a plurality, particularly preferably all of the grooves (15) have a depth, measured perpendicularly to the surface, of between 5 μm and 20 μm, preferably between 8 μm and 12 μm, preferably of approximately 10 μm, and / or The groove diameter (D) of at least one, preferably a plurality, particularly preferably all grooves (15) is between 30 μm and 90 μm, preferably between 50 μm and 70 μm, preferably approximately 60 μm.

11. The piston ring according to claim 9 or 10, Features The proportion of the surface of the two textured portions (14a, 14b) covered by the grooves (15) is between 15% and 35%.

12. An internal combustion engine (20) for a motor vehicle, The internal combustion engine comprises at least one cylinder (21) surrounding a combustion chamber (22) in which a piston (23) is movably arranged, -in, At least one annular groove (25a, 25b, 25c) is formed on the outer periphery (24) of the piston (23), and the piston ring (1) according to any one of the preceding claims is partially arranged in the annular groove (25a, 25b, 25c) so that the piston ring is supported on both the cylinder (21) and the piston (23), The axial end face (6) of the piston ring (1) is arranged in at least one annular groove (25a, 25b, 25c) axially facing away from the combustion chamber (22).

13. The internal combustion engine according to claim 12, Features - on the outer circumference (24) of the piston (23), a first annular groove (25a), a second annular groove (25b) and a third annular groove (25c) are arranged axially spaced from each other, the first annular groove (25a) axially faces the combustion chamber (22), the second annular groove (25b) is axially arranged between the first annular groove (25a) and the third annular groove (25c), - wherein the piston ring (1) according to any one of claims 1 to 10 is arranged at least in the first annular groove (25a), preferably in the first annular groove (25a) and the second annular groove (25b).

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