CYLINDER LINER FOR AN INTERNAL COMBUSTION ENGINE

Abstract

A cylinder liner for an internal combustion engine may include a hollow-cylindrical liner body, which may have an inner circumferential surface including a first axial portion and a second axial portion. The first axial portion may open at a first opening angle towards the second axial portion. The second axial portion may open at a second opening angle away from the first axial portion. The second opening angle may be greater than the first opening angle. A first surface roughness in the first axial portion may be greater than a second surface roughness in the second axial portion. A plateau aspect in the second axial portion, which may be defined as R3p=Rvk/(Rpk+Rk), may be 0.2 to 1.6. A texture height in the second axial portion, which may be defined as R3k=Rpk+Rk+Rvk, may be 0.4 μm or less.

Claims

1. A cylinder liner for an internal combustion engine, comprising: a hollow-cylindrical liner body extending along an axial direction, the liner body having an inner circumferential side surface including, along the axial direction, a first axial portion and a second axial portion; the first axial portion formed one of cylindrically and conically, and opening at a first opening angle towards the second axial portion; the second axial portion opening at a second opening angle away from the first axial portion; wherein the second opening angle is greater than the first opening angle; wherein a first surface roughness of the inner circumferential surface in the first axial portion is greater than a second surface roughness in the second axial portion; wherein a plateau aspect of the inner circumferential surface in the second axial portion, which is defined as R3p=Rvk/(Rpk+Rk), is 0.2 to 1.6; and wherein a texture height of the inner circumferential surface in the second axial portion, which is defined as R3k=Rpk+Rk+Rvk, is 0.4 μm or less.

2. The cylinder liner according to claim 1, wherein the first surface roughness has: an Rpk<0.15 μm; an Rk<0.5; and an Rvk of 0.2 μm to 1.5 μm.

3. The cylinder line according to claim, wherein the second surface roughness has: an Rpk<0.05 μm; wherein an Rk<0.15 μm; and an Rvk<0.2 μm.

4. The cylinder liner according to claim 1, wherein: the liner body further includes a third axial portion; the third axial portion is formed one of cylindrically and conically, and opens at a third opening angle way from the second axial portion; and the second axial portion, relative to the axial direction, is arranged between the first axial portion and the third axial portion.

5. The cylinder liner according to claim 4, wherein a third surface roughness of the inner circumferential surface in the third axial portion is smaller than the first surface roughness.

6. The cylinder liner according to claim 1, wherein a radial widening of the liner body in a direction perpendicular to the axial direction is 1 μm to 100 μm.

7. The cylinder liner according to claim 1, wherein the inner circumferential surface has a generatrix that at least one of: follows a curved course in at least one of (i) a longitudinal section along the axial direction of the first axial portion and (ii) a longitudinal section along the axial direction of the second axial portion; and follows a straight line in at least one of (i) a longitudinal section along the axial direction of the first axial portion an (ii) a longitudinal section along the axial direction of the second axial portion.

8. The cylinder liner according to claim 4, wherein the inner circumferential surface has a generatrix that at least one of: follows a curved course in a longitudinal section along the axial direction of in the third axial portion; and follows a straight line in a longitudinal section along the axial direction of the third axial portion.

9. The cylinder liner according to claim 1, wherein, relative to the axial direction, the second axial portion is disposed directly adjacent to the first axial portion.

10. The cylinder liner according to claim 4, wherein, relative to the axial direction, the third axial portion is disposed directly adjacent to the second axial portion.

11. An internal combustion engine for a motor vehicle, comprising: a cylinder liner delimiting an outer circumference of a cylinder bore; a piston adjustably arranged in the cylinder bore, the piston adjustable in an axial direction of the cylinder liner between a top reversal point and bottom reversal point; the cylinder liner including a hollow-cylindrical liner body extending along the axial direction, the liner body having an inner circumferential surface including a first axial portion and a second axial portion; the first axial portion formed one of cylindrically and conically, and opening at a first opening angle towards the second axial portion; the second axial portion opening at a second opening angle away from the first axial portion; wherein the second opening angle is greater than the first opening angle; wherein a first surface roughness of the inner circumferential surface in the first axial portion is greater than a second surface roughness in the second axial portion; wherein a plateau aspect of the inner circumferential surface in the second axial portion, which is defined as R3p=Rvk/(Rpk+Rk), is 0.2 to 1.6; wherein a texture height of the inner circumferential surface in the second axial portion, which is defined as R3k=Rpk+Rk+Rvk, is 0.4 μm or less; and wherein the top reversal point is arranged in the first axial portion of the cylinder liner.

12. The internal combustion engine according to claim 11, wherein the bottom reversal point is arranged in the second portion of the cylinder liner.

13. The internal combustion engine according to claim 11, wherein: the liner body further includes a third axial portion; the second axial portion is arranged between the first axial portion and the third axial portion relative to the axial direction; and the bottom reversal point is arranged in the third axial portion of the cylinder liner.

14. A motor vehicle, comprising an internal combustion engine according to claim 11.

15. The cylinder liner according to claim 1, wherein the first opening angle and the second opening angle are defined relative to the axial direction.

16. The cylinder liner according to claim 1, wherein the first axial portion is cylindrical and the first opening angle is substantially 0°.

17. The cylinder liner according to claim 1, wherein the first axial portion is conical.

18. The cylinder liner according to claim 4, wherein the third axial portion is cylindrical and the third opening angle is substantially 0°.

19. The cylinder liner according to claim 4, wherein the third axial portion is conical.

20. The cylinder liner according to claim 1, wherein: the plateau aspect is 0.6 to 0.8; and the texture height is 0.2 μm or less.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] It shows, in each case schematically:

[0036] FIG. 1 shows a first example of a cylinder liner according to the invention, in which the first axial portion of the inner circumferential side is formed cylindrically, i.e. without opening angle,

[0037] FIG. 2 shows a second example of a cylinder liner according to the invention, in which the first axial portion of the inner circumferential side opens conically towards the second axial portion.

DETAILED DESCRIPTION

[0038] FIG. 1 illustrates, in a longitudinal section along an axial direction A, a first example of a cylinder liner 1 according to the invention for an internal combustion engine of a motor vehicle which is not shown. The cylinder liner 1 includes a hollow-cylindrical liner body 2 extending along the axial direction A, whose inner circumferential side 3 comprises, along the axial direction A, a first, second and third second axial portion 4a, 4b, 4c. The second axial portion 4b is arranged along the axial direction A between the first and third axial portion 4a, 4c.

[0039] The axial direction A extends along a centre longitudinal axis M of the liner body 2, while a radial direction extends perpendicularly to the axial direction A away from the centre longitudinal axis M. A circumferential direction U—extending perpendicular both to the axial direction A and also to the radial direction R—encircles the centre longitudinal axis M. In a simplified variant of the example (not shown), the third axial portion 4c can be omitted.

[0040] A possible material for the liner body 2 for example is aluminium, steel or cast iron.

[0041] In the example of FIG. 1, the inner circumferential side 3 in the first axial portion 4a is formed cylindrically, as shown—i.e. without opening and without taper and thus at an opening angle zero. Thus, the inner circumferential side 3 extends in the first axial portion 4b along the axial direction A and parallel to the centre longitudinal axis M. This means that the liner diameter d determined by the generatrix of the inner circumferential side 3 of the liner body 2 has a constant value d1 along the axial direction A in the first axial portion 4a.

[0042] FIG. 2 shows a scenario alternative thereto. Accordingly, the first axial portion 4a can open—preferentially conically—at a first opening angle α1 towards the second axial portion, i.e. taper away from the second axial portion 4b—preferentially conically. In the shown longitudinal section along the axial direction A, the opening angle α1 corresponds to the intermediate angle between the first axial portion 4a of the inner circumferential side 3 and the centre longitudinal axis M of the liner body 2. This means that along the axial direction A in the first axial portion 4a the liner diameter d of the liner body 2 determined by the generatrix of the inner circumferential side 3 has a value d1′ increasing along the axial direction A.

[0043] Both in the example of FIG. 1 and also in that of FIG. 2, the second axial portion 4b opens at a second opening angle α2 away from the first axial portion, namely preferentially conically. In the longitudinal section shown in each of the figures along the axial direction A, the opening angle α2 corresponds to the intermediate angle between the second axial portion 4b of the inner circumferential side 3 and of the centre longitudinal axis M of the liner body 2.

[0044] This means that the liner diameter d of the liner body 2 determined by the inner circumferential side 3 has, along the axial direction A, a value d2 increasing along the axial direction A in the second axial portion 4b. Here, the second opening angle α2 of the second axial portion 4b is greater than the possibly existing first opening angle α1 of the first axial portion 4a. This means that the value d2 of the liner diameter d increases more in the second axial portion 4b than the value d1′ of the liner diameter d in the first axial portion 4a. The two opening angles α1, α2 are shown enlarged in the FIGS. 1 and 2 for the sake of better illustration. Typical values for the opening angle α1 are in the range between 0 and 5 angular minutes. Typical values for the opening angle α2 are in the range between 4 and 25 angular minutes.

[0045] Apart from this, the liner body 2, can comprise, in both examples as shown in the FIGS. 1 and 2, a third axial portion 4c, in which the inner circumferential side 3 is formed cylindrically or opens (shown in dashed lines each in the FIGS. 1 and 2) at a third opening angle α3 away from the second axial portion 4c, preferentially conically. This means that the value d3 of the liner diameter d of the liner body 2 determined by the inner circumferential side 3 has a constant value d3 along the axial direction A in the third portion 4c or increases. In a respective simplified variant both of the example of FIG. 1 and also of the example of FIG. 2 the third axial portion 4c can be omitted.

[0046] In each of the exemplary scenarios explained above, a widening of the cylinder liner 1, originating from the centre longitudinal axis M along the radial direction R, i.e. measured perpendicularly to the axial direction A, can be up to 100 μm, preferentially approximately 50 μm.

[0047] In the examples of the FIGS. 1 and 2, a first surface roughness OR1 of the inner circumferential side 3 in the first axial portion 4b is greater than a second surface roughness OR2 in the second axial portion 4b. Further, a third surface roughness OR3 of the inner circumferential side 3 is smaller in the third axial portion 4c—provided this third portion 4c is present—is smaller than the first surface roughness OR1. The third surface roughness OR3 can, in an embodiment variant, be equal to the second surface roughness OR2, but alternatively thereto, also smaller or greater than the second surface roughness OR2. Thus, the surface roughness of the inner circumferential side 3 in the region of the first axial portion 4a is maximal, i.e. OR1>OR2. OR1>OR3 may also apply where appropriate.

[0048] For example, the first surface roughness OR1 of the inner circumferential side 3 can be characterised in the first axial portion 4a by a value Rpk<0.15 μm, by a value Rk<0.5 μm and by a value Rvk between 0.2 μm and 1.5 μm. Apart from this, the second surface roughness OR2 of the surface of the inner circumferential side 3 in the second axial portion 4b can have a value RpK<0.05 μm and a value Rk<0.15 μm and Rvk a value <0.2 μm. Here, Rk is the roughness of the roughness core profile, i.e. the so-called “core roughness”. Further, RpK is the average height of the peaks protruding out of the core region, i.e. the so-called “reduced peak height”. Finally, Rvk is the average depth of the grooves protruding out of the core region, i.e. the so-called “reduced valley depth”.

[0049] A plateau aspect PA2 of the inner circumferential side 3 in the second axial portion 4b is defined as R3p=Rvk/(Rpk+Rk) and is between 0.2 and 1.6, preferentially between 0.6 and 1.6, most preferentially between 0.6 and 0.8. A texture height SH2 of the inner circumferential side 3 in the second axial portion 4b is defined as R3k=Rpk+Rk+Rvk and amounts to maximally 0.4 μm, preferentially maximally 0.2 μm.

[0050] Thus, R3p describes the characteristic of the contact and core region relative to the surface valleys. R3k thus describes the overall roughness of the honing texture without extreme peak and valley regions.

[0051] The desired surface roughness and the plateau aspect PA2 and the texture height SH2 can be created by honing the axial portion 4a, 4b, 4c of the inner circumferential side 3 concerned. Applying a texture to the axial portion 4a, 4b, 4c of the inner circumferential side 3 concerned is also conceivable, for example with the help of a suitable laser or etching process

[0052] In the two FIGS. 1 and shown longitudinal section along the axial direction A, the inner circumferential side 3 in the first, second and third axial portion 4a, 4b, 4c follows a straight line course in each case. However a curved design of two or of all three axial portions 4a, 4b, 4c (not shown in the figures for the sake of clarity) is also conceivable. It is also conceivable that one or more (first) sub-portions of the first, second and/or third axial portion 4a, 4b, 4c are formed in a straight line and one or more (second) sub-portions of the first, second and/or third axial portion 4a, 4b, 4c are formed curved.

[0053] In the example of the FIGS. 1 and 2, the second axial portion 4b along the axial direction A directly follows the first axial portion 4a. Likewise, the third axial portion 4c along the axial direction A directly follows the second axial portion 4b. Thus, the three portions 4a, 4b, 4c directly merge into one another.

[0054] In a first optional variant of the examples, an axial intermediate portion (not shown) having a suitable contour profile of the inner circumferential side 3 between the first and second axial portion 4a, 4b can be formed cylindrically or with an opening angle both in a straight line or curved.

[0055] In a second optional variant of the example, an axial intermediate portion (not shown) having a suitable contour profile of the inner circumferential side 3 between the second and the third axial portion 4a, 4c, can be formed cylindrically or with opening angle as well as in a straight line or curved. The first variant can be combined with the second variant.

[0056] The cylinder liner 1 of the FIGS. 1 and 2 can be used in an internal combustion engine 10, so that it delimits a cylinder bore 5 of the internal combustion engine on the circumferential side. Here, the internal combustion engine 10 includes a piston that is adjustably arranged in the cylinder bore 5 between an top reversal point OP and a bottom reversal point UP, which is not shown in the figures for the sake of clarity.

[0057] As illustrated by the figures, the top reversal point OP is arranged in the first axial portion 4a of the cylinder liner 1. The bottom reversal point UP is arranged in the third axial portion 4c. In the case of the simplified variants of the cylinder liner 1 without third axial portion 4c mentioned above, the bottom reversal point UP can be arranged in the second axial portion 4b.