Cylinder bore for a cylinder housing of an internal combustion engine, and arrangement having a cylinder bore and a piston

Abstract

A cylinder bore for a cylinder housing of an internal combustion engine may have a cylinder running surface, an upper reversal point and a lower reversal point at which a piston, which may be moved up and down in the cylinder bore and may have piston rings and a piston skirt, may reach a speed which approaches zero during engine operation. The cylinder bore may also have a region between the upper reversal point and the lower reversal point at which the piston may reach a maximum speed during engine operation. The cylinder bore may further have at least two circumferential depressions formed within the region, the at least two circumferential depressions each having a diameter that may be greater than a diameter of the cylinder bore above the region and below the region.

Claims

1. A cylinder bore for a cylinder housing of an internal combustion engine, comprising: a cylinder running surface; an upper reversal point and a lower reversal point at which a piston, which is moved up and down in the cylinder bore and has piston rings and a piston skirt, reaches a speed which approaches zero during engine operation; a region between the upper reversal point and the lower reversal point at which the piston reaches a maximum speed during engine operation; at least two circumferential depressions formed within the region, the at least two circumferential depressions each having a diameter greater than a diameter of the cylinder bore above the region and below the region; wherein a roughness of the cylinder running surface in a region of the at least two circumferential depressions is less than in regions outside the at least two circumferential depressions; and wherein the diameters of the at least two circumferential depressions are greater by 5 μm to 30 μm than at least one of the diameter of the cylinder bore above the region and the diameter of the cylinder bore below the region.

2. The cylinder bore as claimed in claim 1, wherein the diameters of the at least two circumferential depressions are the same.

3. The cylinder bore as claimed in claim 1, wherein the diameter of the cylinder bore above the region and below the region are the same.

4. The cylinder bore as claimed in claim 1, wherein the diameter of the cylinder bore above the region and below the region are constant over axial heights of the cylinder bore above the region and below the region.

5. The cylinder bore as claimed in claim 1, wherein a roughness of the cylinder running surface in a region of the at least two circumferential depressions is less than 3 μm.

6. The cylinder bore as claimed in claim 5, wherein the roughness of the cylinder running surface in the region of the at least two circumferential depressions is less than 1 μm.

7. The cylinder bore as claimed in claim 6, wherein the roughness of the cylinder running surface in the region of the at least two circumferential depressions is less than 0.5 μm.

8. The cylinder bore as claimed in claim 1, wherein the cylinder running surface has, at least partially in a region outside the at least two circumferential depressions, a hardness greater than in a region of the at least two circumferential depressions.

9. The cylinder bore as claimed in claim 1, wherein the at least two circumferential depressions merge into adjacent portions of the cylinder running surface via a curved transition.

10. The cylinder bore as claimed in claim 1, wherein: an intermediate region of the cylinder running surface extends axially between the at least two circumferential depressions; and the intermediate region of the cylinder running surface includes a max speed point at which the piston reaches the maximum speed during engine operation.

11. An arrangement for a cylinder housing of an internal combustion engine, comprising: a piston having piston rings and a piston skirt; and a cylinder bore in which the piston is moved up and down, the cylinder bore having: a cylinder running surface; an upper reversal point and a lower reversal point at which the piston reaches a speed which approaches zero during engine operation; a region between the upper reversal point and the lower reversal point at which the piston reaches a maximum speed during engine operation; and at least two circumferential depressions formed within the region, the at least two circumferential depressions each having a diameter greater than a diameter of the cylinder bore above the region and below the region; wherein at least one piston ring, at least in a contact region with the cylinder running surface, includes one of a CrN coating and a DLC coating produced by a PVD process; and wherein the cylinder running surface has, at least partially in a region outside the at least two circumferential depressions, a hardness greater than in a region of the at least two circumferential depressions.

12. The arrangement as claimed in claim 11, wherein at least the piston skirt includes a steel material.

13. The arrangement as claimed in claim 11, wherein the arrangement is configured for an internal combustion engine for motor vehicles having at least two cylinders.

14. The arrangement as claimed in claim 11, wherein the diameter of the cylinder bore above the region and below the region are constant over axial heights of the cylinder bore above the region and below the region.

15. The arrangement as claimed in claim 11, wherein the diameters of the at least two circumferential depressions are greater by 5 μm to 30 μm than at least one of the diameter of the cylinder bore above the region and the diameter of the cylinder bore below the region.

16. The arrangement as claimed in claim 11, wherein a roughness of the cylinder running surface in a region of the at least two circumferential depressions is less than in regions outside the at least two circumferential depressions.

17. The arrangement as claimed in claim 11, wherein a roughness of the cylinder running surface in a region of the at least two circumferential depressions is less than 3 μm.

18. An arrangement for a cylinder housing of an internal combustion engine, comprising a piston including a plurality of piston rings and a piston skirt, and a cylinder bore in which the piston is disposed, the cylinder bore including: a cylindrical interior running surface having an upper reversal point and a lower reversal point between which the piston axially slides within the piston bore during engine operation; and at least two circumferential depressions disposed in a region between the upper reversal point and the lower reversal point at which the piston reaches a maximum speed during engine operation; wherein the at least two circumferential depressions each have a diameter that is 5 μm to 30 μm greater than a diameter of the cylinder bore above the region and below the region; and wherein the running surface has a surface roughness of 3 μm Rz or less in a region of the at least two circumferential depressions.

19. The arrangement as claimed in claim 18, wherein: an intermediate region of the cylindrical running surface extends axially between the at least two circumferential depressions; the piston is disposed within the cylinder bore with play between the piston and the cylindrical running surface; and when aligned with the intermediate region of the cylindrical running surface, at least one of the plurality of piston rings is in tight sliding contact with the intermediate region of the cylindrical running surface such that the piston is substantially prevented from deflecting and striking the cylindrical running surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the present invention will be described in more detail below with reference to the appended drawings. In a schematic illustration which is not true to scale:

(2) FIG. 1A shows a first exemplary embodiment of a cylinder bore according to the invention in the form of a cylinder liner having a piston, which is guided up and down therein;

(3) FIG. 1B shows a speed profile of the piston skirt correlated thereto during engine operation;

(4) FIG. 2A shows a further exemplary embodiment of a cylinder bore according to the invention in the form of a cylinder liner having a piston, which is guided up and down therein; and

(5) FIG. 2B shows a speed profile of the piston skirt that is correlated thereto during engine operation.

DETAILED DESCRIPTION

(6) The cylinder bore 10 according to the invention illustrated in FIG. 1A is configured in the form of a cylinder liner 11. The cylinder liner 11 can consist for example of a cast iron material, in the exemplary embodiment of a cast iron material with lamellar graphite, and can be produced for example by a centrifugal casting process. In the exemplary embodiment, the cylinder liner 11 has a shaft 12 with a circumferential flange 13, and a cylinder running surface 14.

(7) A piston 20, which has piston rings 21 and a piston skirt 22, is guided upward and downward in the cylinder liner 11 during engine operation. During engine operation, the piston skirt 22 moves along the cylinder running surface 14 between an upper reversal point OS and a lower reversal point US, where the piston 20 reaches a speed v.sub.o which approaches zero. The point of minimum speed is defined on the piston 20 itself at the highest loaded point of the piston skirt 22. During engine operation, the piston skirt 22 reaches a higher speed v, with a maximum speed v.sub.max, within a region 15 between the upper reversal point OS and the lower reversal point US.

(8) In this region 15, there is provision according to the invention that two circumferential depressions 18a, 18b are provided which have a diameter D2a, D2b which are greater than the diameter D1 above the region 15 and the diameter D3 below the region 15. The difference between the diameters D2a, D2b and the diameters D1 and D3 is preferably 5 μm to 30 μm.

(9) Above and below the region 15 there are formed running surface regions 14a, 14b of the cylinder running surface 14 which are in frictional contact with the piston rings 21 during engine operation.

(10) It can also be seen from FIG. 1A that the diameters D2a, D2b have identical dimensions. The diameters D1 and D3 likewise have identical dimensions. The diameters D1 and D3 are furthermore constant over their heights h1 and h3.

(11) Between the depressions 18a, 18b there is situated a further circumferential running surface region 14c which is in frictional contact with the piston rings 21 during engine operation. This means that the piston 20 is guided securely along the running surface regions 14a, 14b, 14c during engine operation, with the result that a deflection of the piston skirt 22 due to possibly occurring transverse accelerations is avoided.

(12) The cylinder bore 110 according to the invention illustrated in FIG. 2A is likewise configured in the form of a cylinder liner 111. The cylinder liner 111 can consist for example of a cast iron material, in the exemplary embodiment of a cast iron material with lamellar graphite, and can be produced for example by a centrifugal casting process. In the exemplary embodiment, the cylinder liner 111 has a shaft 112 with a circumferential flange 113, and a cylinder running surface 114.

(13) A piston 20, which has piston rings 21 and a piston skirt 22, is guided upward and downward in the cylinder liner 111 during engine operation. During engine operation, the piston skirt 22 moves along the cylinder running surface 114 between an upper reversal point OS and a lower reversal point US, where the piston 20 reaches a speed v.sub.o which approaches zero. The point of minimum speed is defined on the piston 20 itself at the highest loaded point of the piston skirt 22. During engine operation, the piston skirt 22 reaches a higher speed v, with a maximum speed v.sub.max, within a region 115 between the upper reversal point OS and the lower reversal point US.

(14) In this region 115, there is provision according to the invention that three circumferential depressions 118a, 118b, 118c are provided which have a diameter D2a, D2b and D2c which are greater than the diameter D1 above the region 115 and the diameter D3 below the region 115. The difference between the diameters D2a, D2b, D2c and the diameters D1 and D3 is preferably 5 μm to 30 μm.

(15) Above and below the region 115 there are formed running surface regions 114a, 114b of the cylinder running surface 114 which are in frictional contact with the piston rings 21 during engine operation.

(16) It can also be seen from FIG. 1A that the diameters D2a, D2b, D2c have identical dimensions. The diameters D1 and D3 likewise have identical dimensions. The diameters D1 and D3 are furthermore constant over their heights h1 and h3.

(17) Between the depressions 118a, 118b, 118c there are situated two further circumferential running surface regions 114c, 114d which are in frictional contact with the piston rings 21 during engine operation. This means that the piston 20 is guided securely along the running surface regions 114a, 114b, 114c, 114d during engine operation, with the result that a deflection of the piston skirt 22 due to possibly occurring transverse accelerations is avoided.