CYLINDER SLEEVE FOR AN INTERNAL COMBUSTION ENGINE

Abstract

A cylindrical sleeve for an internal combustion engine is disclosed. The cylindrical sleeve includes a hollow cylindrical sleeve body, extending along an axial direction, with an inner peripheral side that has, along the axial direction, a first axial portion and a second axial portion. The inner peripheral side in the first axial portion is either cylindrical or opens at a first opening angle towards the second axial portion. The second axial portion opens at a second opening angle away from the first axial portion that is greater than the first opening angle. A first surface roughness of the inner peripheral side in the first axial portion is greater than a second surface roughness in the second axial portion.

Claims

1. A cylinder sleeve for an internal combustion engine, comprising: a hollow cylindrical sleeve body, extending along an axial direction, with an inner peripheral side that has, along the axial direction, a first axial portion and a second axial portion, wherein the inner peripheral side in the first axial portion is either cylindrical or opens at a first opening angle toward the second axial portion, wherein the second axial portion opens at a second opening angle away from the first axial portion that is greater than the first opening angle, and wherein a first surface roughness of the inner peripheral side in the first axial portion is greater than a second surface roughness in the second axial portion.

2. The cylinder sleeve according to claim 1, wherein the first surface roughness of the inner peripheral side in the first axial portion is Rpk<0.15 mm, wherein Rk<0.5 and Rvk is between 0.2 and 1.5.

3. The cylinder sleeve according to claim 1, wherein the second surface roughness of the inner peripheral side in the second axial portion is Rpk<0.05 mm, wherein Rk<0.15 and Rvk<0.2.

4. The cylinder sleeve according to claim 1, wherein the sleeve body has a third axial portion where the inner peripheral side is cylindrical or opens at a third opening angle away from the second axial portion, wherein the second axial portion is arranged in the axial direction between the first axial portion and the third axial portion.

5. The cylinder sleeve according to claim 4, wherein a third surface roughness of the inner peripheral side in the third axial portion is less than the first surface roughness in the first axial portion.

6. The cylinder sleeve according to claim 1, wherein a radial widening of the cylinder sleeve, measured perpendicularly to the axial direction, is 1 mm to 100 mm.

7. The cylinder sleeve according to claim 1, wherein at least one of: in a longitudinal section along the axial direction, a surface line of the inner peripheral side in at least one of the first axial portion and the second axial portion runs in a curved manner; or/and that and in the longitudinal section along the axial direction, the surface line of the inner peripheral side in at least one of the first axial portion and the second axial portion runs in a rectilinear manner.

8. The cylinder sleeve according to claim 4, wherein at least one of: in a longitudinal section along the axial direction, a surface line of the inner peripheral side in the third axial portion runs in a curved manner; and in the longitudinal section along the axial direction, the surface line of the inner peripheral side in the third axial portion runs in a rectilinear manner.

9. The cylinder sleeve according to claim 1, wherein the second axial portion along the axial direction directly adjoins the first axial portion.

10. The cylinder sleeve according to claim 4, wherein the third axial portion along the axial direction directly adjoins the second axial portion.

11. An internal combustion engine for a motor vehicle, comprising: at least one cylinder bore delimited on a peripheral side by a cylinder sleeve, the cylinder sleeve including: a hollow cylindrical sleeve body, extending along an axial direction, with an inner peripheral side that has, along the axial direction, a first axial portion and a second axial portion, wherein the inner peripheral side in the first axial portion is either cylindrical or opens at a first opening angle towards the second axial portion, wherein the second axial portion opens at a second opening angle away from the first axial portion, the second opening angle being greater than the first opening angle, wherein the inner peripheral side has a first surface roughness in the first axial portion that is greater than a second surface roughness in the second axial portion, a piston arranged displaceably in the at least one cylinder bore along the axial direction of the cylinder sleeve between an upper reversal point and a lower reversal point, and wherein the upper reversal point is arranged in the first axial portion of the cylinder sleeve.

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

13. The internal combustion engine according to claim 11, wherein the lower reversal point is arranged in a third axial portion of the cylinder sleeve, wherein the third portion is cylindrical or opens at a third opening angle away from the second axial portion, and the second axial portion is arranged in the axial direction between the first axial portion and the third axial portion.

14. A motor vehicle, comprising: an internal combustion engine, the internal combustion engine including: at least one cylinder bore delimited on a peripheral side by a cylinder sleeve, the cylinder sleeve including: a hollow cylindrical sleeve body, extending along an axial direction, with an inner peripheral side that has, along the axial direction, a first axial portion and a second axial portion, wherein the inner peripheral side in the first axial portion is either cylindrical or opens at a first opening angle towards the second axial portion, wherein the second axial portion opens at a second opening angle away from the first axial portion, the second opening angle being greater than the first opening angle, wherein the inner peripheral side has a first surface roughness in the first axial portion that is greater than a second surface roughness in the second axial portion, a piston arranged displaceably in the at least one cylinder bore along the axial direction of the cylinder sleeve between an upper reversal point and a lower reversal point, and wherein the upper reversal point is arranged in the first axial portion of the cylinder sleeve.

15. The motor vehicle according to claim 14, wherein at least one of: the first surface roughness of the inner peripheral side in the first axial portion is Rpk<0.15 mm, wherein Rk<0.5 and Rvk is between 0.2 and 1.5; and the second surface roughness of the inner peripheral side in the second axial portion is Rpk<0.05 mm, wherein Rk<0.15 and Rvk<0.2.

16. The internal combustion engine according to claim 11, wherein a radial widening of the cylinder sleeve measured perpendicularly to the axial direction is 1 mm to 100 mm.

17. The internal combustion engine according to claim 11, wherein at least one of: the first surface roughness of the inner peripheral side in the first axial portion is Rpk<0.15 mm, wherein Rk<0.5 and Rvk is between 0.2 and 1.5; and the second surface roughness of the inner peripheral side in the second axial portion is Rpk<0.05 mm, wherein Rk<0.15 and Rvk<0.2.

18. The internal combustion engine according to claim 13, wherein a third surface roughness of the inner peripheral side in the third axial portion is less than the first surface roughness in the first axial portion.

19. The cylinder sleeve according to claim 1, wherein the first axial portion opens conically at the first opening angle towards the second axial portion.

20. The cylinder sleeve according to claim 1, wherein the second axial portion opens conically at the second opening angle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] There are shown, respectively schematically:

[0030] FIG. 1 a first example of a cylinder sleeve according to the invention, in which the first axial portion of the inner peripheral side is cylindrical, therefore without opening angle,

[0031] FIG. 2 a second example of a cylinder sleeve according to the invention, in which the first axial portion of the inner peripheral side opens conically towards the second axial portion.

DETAILED DESCRIPTION

[0032] FIG. 1 illustrates in a longitudinal section along an axial direction A a first example of a cylinder sleeve 1 according to the invention for an internal combustion engine, not illustrated, of a motor vehicle. The cylinder sleeve 1 comprises a hollow cylindrical sleeve body 2, extending along the axial direction A, the inner peripheral side 3 of which along the axial direction A has 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.

[0033] The axial direction A extends along a central longitudinal axis M of the sleeve body 2, a radial direction extends perpendicularly to the axis direction A away from the central longitudinal axis A. A circumferential direction U runs—extending perpendicularly both to the axial direction A and also to the radial direction R—around the central longitudinal axis M. In a simplified variant of the example (not shown), the third axial portion 4c can be dispensed with.

[0034] Aluminium, steel or cast iron for example come into consideration as material for the sleeve body 2.

[0035] In the example of FIG. 1, the inner peripheral side 3 in the first axial portion 4a as shown is cylindrical—therefore without an opening and without narrowing and thus with an opening angle of zero. The inner peripheral side 3 therefore extends in the first axial portion 4a along the axial direction A and parallel to the central longitudinal axis M. This means that the sleeve diameter d of the sleeve body 2, established by the surface line of the inner peripheral side 3 has a constant value d1 along the axial direction A in the first axial portion 4a.

[0036] FIG. 2 shows an alternative scenario thereto. Accordingly, the first axial portion 4a can open—preferably conically—at a first opening angle a1 towards the second axial portion, therefore away from the second axial portion 4b. In the longitudinal section which is shown along the axial direction A, the opening angle a1 corresponds to the intermediate angle between the first axial portion 4a of the inner peripheral side 3 and the central longitudinal axis M of the sleeve body 2. This means that the sleeve diameter d of the sleeve body 2, established through the surface line of the inner peripheral side 3 along the axial direction A in the first axial portion 4a has an increasing value d1′ along the axial direction A.

[0037] 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 a2 away from the first axial portion, and namely preferably conically. In the longitudinal section respectively shown in the figures along the axial direction A, the opening angle a2 corresponds to the intermediate angle between the second axial portion 4b of the inner peripheral side 3 and the central longitudinal axis M of the sleeve body 2.

[0038] This means that the sleeve diameter d of the sleeve body 2, established through the inner peripheral side 3, along the axial direction A in the second axial portion 4b has a value d2 increasing along the axial direction A. Here, the second opening angle a2 of the second axial portion 4b is greater than the possibly present first opening angle a1 of the first axial portion 4a. This means that the value d2 of the sleeve diameter d in the second axial portion 4b increases more intensively than the value d1′ of the sleeve diameter d in the first axial portion 4a. The two opening angles a1, a2 are illustrated in an enlarged manner in FIGS. 1 and 2 for reasons of better illustration. Typical values for the opening angle a1 lie in the range between 0 and 5 angle minutes. Typical values for the opening angle a2 lie in the range between 4 and 25 angle minutes.

[0039] In addition, the sleeve body 2 in both examples, as shown in FIGS. 1 and 2, can have a third axial portion 4c, in which the inner peripheral side 3 is cylindrical or opens at a third opening angle a3 away from the second axial portion 4c—preferably conically—(illustrated respectively in dashed lines in FIGS. 1, 2). This means that the value d3 of the sleeve diameter d of the sleeve body 2, established through the inner peripheral side 3, along the axial direction A in the third portion 4c has a constant value d3 or increases. In a respectively simplified variant, both of the example of FIG. 1 and also of the example of FIG. 2, the third axial portion 4c can be dispensed with.

[0040] In each of the example scenarios explained above, a widening of the cylinder sleeve 1, measured proceeding from the central longitudinal axis M along the radial direction R, therefore perpendicularly to the axial direction A, can be up to 100 mm, preferably ca. 50 mm.

[0041] In the examples of FIGS. 1 and 2, a first surface roughness OR1 of the inner peripheral side 3 in the first axial portion 4a is greater than a second surface roughness OR 2 in the second axial portion 4b. Furthermore, a third surface roughness OR 3 of the inner peripheral side 3 in the third axial portion 4c—if this third portion 4c is present—is smaller than the first surface roughness OR1. In an embodiment variant, the third surface roughness OR 3 can be identical to the second surface roughness OR2, alternatively thereto, however, it can also be smaller or greater than the second surface roughness OR2. The surface roughness of the inner peripheral side 3 is therefore maximal in the region of the first axial portion 4a, i.e. OR1>OR2. If applicable also OR1>OR3.

[0042] For example, the first surface roughness OR1 of the inner peripheral side 3 in the first axial portion 4a can be characterized by a value Rpk<0.15 mm, by a value Rk<0.5 and by a value Rvk between 0.2 and 1.5. In addition, the second surface roughness OR2 of the surface of the inner peripheral side in the second axial portion 4b can have a value Rpk<0.05 mm and a value Rk<0.15 and Rvk a value<0.2. Rk here is the depth of the roughness core profile, therefore the so-called “core roughness depth”. In addition, Rpk is the averaged height of the peaks projecting from the core region, therefore the so-called “reduced peak height”. Finally, Rvk is the averaged depth of the grooves projecting from the core region, therefore the so-called “reduced groove depth”.

[0043] The desired surface roughnesses can be produced by honing the respective axial portion 4a, 4b, 4c of the inner peripheral side 3. The application of a texturing is also conceivable, for example by means of a suitable laser- or etching process, onto the respective axial portion 4a, 4b, 4c of the inner peripheral side 3.

[0044] In the longitudinal section, shown in the two FIG. 1 and along the axial direction A the inner peripheral side 3 runs in the first, second and third axial portion 4a, 4b, 4c respectively in a rectilinear manner. However, a curved configuration of two or of all three axial portions 4a, 4b, 4c is also conceivable (not shown in the figures for the sake of clarity). It is also conceivable that one or more (first) sub-portions of the first, second or/and third axial portion 4a, 4b, 4c are configured in a rectilinear manner and one or more (second) sub-portions of the first, second or/and third axial portion 4a, 4b, 4c are configured in a curved manner.

[0045] In the example of FIGS. 1 and 2, the second axial portion 4b directly adjoins the first axial portion 4a along the axial direction A. Likewise, the third axial portion 4c directly adjoins the second axial portion 4b along the axial direction A. The three portions 4a, 4b, 4c therefore merge directly into one another.

[0046] In a first optional variant of the examples, between the first and second axial portion 4a, 4b an axial intermediate portion (not shown) with a suitable contour shape of the inner peripheral side 3—cylindrical or with opening angle and in a rectilinear or curved manner—can be formed.

[0047] In a second optional variant of the examples, between the second and the third axial portion 4b, 4c an axial intermediate portion (not shown) with a suitable contour shape of the inner peripheral side 3—cylindrical or with opening angle and in a rectilinear or curved manner—can be formed. The first variant can be combined with the second variant.

[0048] The cylinder sleeve 1 of 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 peripheral side. The internal combustion engine 10 comprises here a piston, arranged displaceably in the cylinder bore 5 along the axial direction A of the cylinder sleeve 1 between an upper reversal point OP and a lower reversal point UP, which piston is not illustrated in the figures, for clarity.

[0049] As the figures demonstrate, the upper reversal point OP is arranged in the first axial portion 4a of the cylinder sleeve 1. The lower reversal point UP is arranged in the third axial portion 4c. In the case of the above-mentioned, simplified variants of the cylinder sleeve 1 without a third axial portion 4c, the lower reversal point UP can be arranged in the second axial portion 4b.