PISTON RING SYSTEM FOR AN INTERNAL COMBUSTION ENGINE WITH DIRECT WATER INJECTION

Abstract

A piston ring system for an internal combustion engine includes a first compression piston ring (2), a second compression piston ring (4), and an oil scraper piston ring (6). The first compression piston ring (2) has a first ring body (8) with a first upper ring flank (10), a first lower ring flank (12), a first ring inner side (14), a first ring outer side (16), as well as two first abutting surfaces. A first contact region (18) of the first ring body (8) is arranged with a cylinder running surface (20) above a first piston ring center (22). At least one first oil pocket (24) is arranged below the first contact region (18) in the circumferential direction. The second compression piston ring (4) having a second ring body (26) a second upper ring flank (28), a second lower ring flank (30), a second ring inner side (32), a second ring outer side (34), as well as two second abutting surfaces. A second contact region (36) of the second ring body (26) is arranged with the cylinder running surface (20) above or below a second piston ring center (38). At least one second oil pocket (40) is arranged below the second contact region (36) in the circumferential direction. The oil scraper piston ring (6) is formed in one piece, two pieces, or three pieces.

Claims

1-10. (canceled)

11. A piston ring system for an internal combustion engine, comprising a first compression piston ring, a second compression piston ring, which is configured to be located below the first compression piston ring, and an oil scraper piston ring, which is configured to be arranged below the first and second compression rings, wherein the first compression piston ring has a first ring body comprising a first upper ring flank, a first lower ring flank, a first ring inner side, a first ring outer side, as well as two first abutting surfaces, wherein a first contact region of the first ring body is arranged with a cylinder running surface above a first piston ring center, wherein at least one first oil pocket is arranged below the first contact region in the circumferential direction, wherein the second compression piston ring comprises a second ring body comprising a second upper ring flank, a second lower ring flank, a second ring inner side, a second ring outer side, as well as two second abutting surfaces, wherein a second contact region of the second ring body is arranged with the cylinder running surface above or below a second piston ring center, wherein at least one second oil pocket is arranged below the second contact region in the circumferential direction, and wherein the oil scraper piston ring is formed in one piece, two pieces, or three pieces.

12. The piston ring system according to claim 11, wherein a main contour of the compression piston rings describes a continuous curve, which connects the offset first oil pocket upper edge to the first contact region with a constant tangent, in order to ensure the hydrodynamic contact ratio over the entire running surface of the compression piston rings.

13. The piston ring system according to claim 11, wherein the first contact region of the ring body is at 1-40% of the axial height of the upper run-out of the groove.

14. The piston ring system according to claim 11, wherein the second contact region of the ring body is at 1-40% of the axial height of the upper run-out of the groove.

15. The piston ring system for an internal combustion engine according to claim 11, wherein the second contact region of the second ring body is arranged with the cylinder running surface below the second piston ring center at a height of 25-45%.

16. The piston ring system for an internal combustion engine according to claim 11, wherein the at least one second oil pocket is divided into a plurality of sections in the circumferential direction.

17. The piston ring system for an internal combustion engine according to claim 16, wherein the at least one second oil pocket is divided into 20 to 30 sections.

18. The piston ring system for an internal combustion engine according to claim 11, wherein the first compression piston ring is arranged on the combustion chamber side, the oil scraper piston ring is arranged on the crankcase side, and the second compression piston ring is arranged between the first compression piston ring and the oil scraper piston ring, wherein a first land height separates an installation space of the first compression piston ring and an installation space of the second compression piston ring in the axial direction, and a second land height separates the installation space of the second compression piston ring and an installation space of the oil scraper piston ring in the axial direction.

19. The piston ring system according to claim 13, wherein the first contact region of the ring body is between 5-20% of the axial height of the upper run-out of the groove.

20. The piston ring system according to claim 14, wherein the second contact region is between 5-20% of the height of the upper run-out of the groove.

21. The piston ring system according to claim 15, wherein the height is between 30-40%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Exemplary embodiments of the invention will be described in more detail below with reference to the figures on the basis of schematic illustrations, wherein

[0032] FIG. 1 shows a piston ring system according to an embodiment of the invention and

[0033] FIG. 2 shows a compression piston ring main contour.

DETAILED DESCRIPTION

[0034] FIG. 1 shows a cross sectional view of a piston ring system. In said piston ring system, 3 grooves are arranged in a piston, wherein a first compression piston ring 2 is arranged in the uppermost groove, a second compression piston ring 4 is arranged in the middle groove, and an oil scraper piston ring 6, which is arranged below the other rings, namely at a distance from the second land height 90, is arranged in the lower groove. It is the main task of the compression piston rings 2, 4 to prevent the gas passage of combustion gases between piston and cylinder wall into the crankcase. It is the main task of the oil scraper piston ring 6 to seal between crankcase and combustion housing, and to regulate the oil film.

[0035] The first compression piston ring 2 has a first ring body 8 comprising a first upper ring flank 10, a first lower ring flank 12, a first ring inner side 14, and a first ring outer side 16. A first contact region 18 of the first ring body 8 comprising a cylinder running surface 20 is arranged above a first piston ring center 22. A first oil pocket 24 for storing oil is arranged below the first contact region 18, wherein said first oil pocket supports the regulation of the oil film on the cylinder running surface. The first contact region 18 is spaced apart farther away from a base of the upper piston groove in the radial radiation than a first grove upper edge 42.

[0036] The second compression piston ring 4 is located so as to sit below the first ring at a distance from the first land height 89 and has a second ring body 26 with a second upper ring flank 28, a second lower ring flank 30, a second ring inner side 32, and a second ring outer side 34. A second contact region 36 of the second ring body 26 with the cylinder running surface 20 is arranged above a second piston ring center 22 but can also be arranged below a second piston ring center 22. A second oil pocket 40 for storing oil is arranged below the second contact region 36, wherein said second oil pocket supports the regulation of the oil film on the cylinder running surface. The second contact region 36 is spaced apart farther away from a base of the middle piston groove in the radial direction than a second groove upper edge 44.

[0037] The oil scraper ring is made of three pieces, but can also be made of two pieces, and has two lamellae, which are pressed against the cylinder wall by means of a separation and expander spring.

[0038] The advantage of the piston ring system according to the invention is that the distribution of the available oil is improved, whereby an adaptation is not made to very small amounts of oil. In spite of the direct water injection into the piston, the oil film is thus not weakened and also does not tear. An insufficient lubrication is effectively avoided. The total height of the first ring body corresponds to the largest distance between the first upper ring flank and the first lower ring flank, measured in the axial direction. A better shape adaptability because of reduced moments of inertia is attained in the case of such an arrangement of the first contact region of the first ring body with the cylinder running surface. The gas pressure is further reduced by means of this arrangement in front of the piston ring, and the sealing effect is improved because of the increased hydrodynamic contact pressure.

[0039] FIG. 2 shows a compression piston ring main contour, which describes a continuous curve, which connects the offset first oil pocket upper edge 42 to the first contact region 18 with a constant tangent.