Piston ring and piston ring/piston combination with improved wear properties

Abstract

A piston ring with improved wear properties has a running surface, an upper ring flank, a lower ring flank, and an inner surface. The piston ring has a radius R, and wherein in a radial section, a running surface contour includes an upper region, a central region, and a lower region. The upper region of the running surface contour has a curvature radius R.sub.o, which lies between the ring radius R and infinity. The central region of the running surface contour has a curvature radius R.sub.m, which lies between the ring radius R and infinity. The lower region has a curvature radius R.sub.u, which is smaller than the ring radius R.

Claims

1. A piston ring with improved wear properties, comprising: a running surface, an upper ring flank, a lower ring flank, and an inner surface, wherein the piston ring has a radius R of predetermined dimension and a ring height h of predetermined dimension, wherein in a radial section, the running surface has a running surface contour which comprises an upper region, a central region, and a lower region, wherein in the radial section between the upper region and the central region, the running surface contour has an upper transition region, and between the central region and the lower region the running surface contour has a lower transition region, wherein the upper region and the upper transition region in each case form parts of torus surfaces, the upper region of the running surface contour has a curvature radius R.sub.o of predetermined dimension, the central region of the running surface contour has a curvature radius R.sub.m of predetermined dimension, the lower region has a curvature radius R.sub.u of predetermined dimension, which is smaller in dimension than the ring radius R, the upper transition region has a rounding radius Rü, om of predetermined dimension which is 1/10.sup.th to 1/30.sup.th the dimension, of the ring height h, and the lower transition region has a rounding radius Rü, mu of predetermined dimension which is 1/10.sup.th to 1/30.sup.th the dimension, of the ring height h.

2. The piston ring according to claim 1, wherein an average tangent angle β of the upper region of the running surface contour is between 2 to 40 times as large as an average tangent angle α of the central region.

3. The piston ring according to claim 2, wherein the average tangent angle β is between 4 to 30 times.

4. The piston ring according to claim 2, wherein the average tangent angle β is between 10 to 20 times.

5. The piston ring according to claim 1, wherein the curvature radius Ro is 1 to 4 times as large as, the ring radius R, and the curvature radius Ru is less than ½ of the ring radius R.

6. The piston ring according to claim 1, wherein the curvature radius Ro is 1 to 2 times as large as the ring radius R, the curvature radius Rm is 1 to 2 times as large as the ring radius R, and the curvature radius Ru is smaller than the ring height h.

7. The piston ring according to claim 1, wherein the curvature radius Ro is 1 to 1.5 as large as the ring radius R, the curvature radius Rm is 1 to 1.5 as large as the ring radius R, and the curvature radius Ru, is less than ½ the ring height h.

8. The piston ring according to claim 1, wherein the lower curvature radius Ru is larger than one or both of the rounding radius Rú, mu and Rü, om.

9. The piston ring according to claim 8, wherein the radius of curvature of the lower region Rü is at least 5 times as large as one or both of Rü,mu and Rü,mo.

10. The piston ring according to claim 8, wherein the radius of curvature of the lower region Rü is at least 10 times as large as one or both of Rü,mu and Rü,mo.

11. The piston ring according to claim 1, wherein the lower central curvature radius Rm is larger than the upper curvature radius Ro.

12. The piston according to claim 11, wherein the lower central curvature radius R.sub.m is 2 to 20 times as large as R.sub.o.

13. The piston according to claim 11, wherein the lower central curvature radius R.sub.m is 4 to 10 times as large as R.sub.o.

14. The piston ring according to claim 1, wherein an angle α between an axial direction and an average tangent of the central region is between −4 and +4°.

15. The piston according to claim 14, wherein the angle α is between 0° and 4°.

16. The piston according to claim 14, wherein the angle α is between 2° and 4°.

17. The piston ring according to claim 1, where in an angle β between an axial direction and an averaged tangent of the upper region is larger than or equal to a sum of an angle α between an axial direction and an averaged tangent of the central region and a value δ, which is between 30′ and 180′.

18. A combination of a piston ring and a piston ring groove, comprising: a piston ring having a running surface, an upper ring flank, a lower ring flank, and an inner surface, wherein the piston ring has a radius R of predetermined dimension, wherein in a radial section, the running surface has a running surface contour which comprises an upper region, a central region, and a lower region, wherein in the radial section between the upper region and the central region, the running surface contour has an upper transition region, and between the central region and the lower region the running surface contour has a lower transition region, wherein the upper region and the upper transition region in each case form parts of torus surfaces, the upper region of the running surface contour has a curvature radius R.sub.o of predetermined dimension, wherein the central region of the running surface contour has a curvature radius R.sub.m of predetermined dimension, wherein the lower region has a curvature radius R.sub.u of predetermined dimension, which is smaller than the ring radius R, wherein the upper transition region has a rounding radius Rü, om of predetermined dimension, which is 1/30.sup.th to 1/10th of the ring height h, and wherein the lower transition region has a rounding radius Rü, mu, which is 1/30th to 1/10th of the ring height h; and a piston ring groove in which the ring is received; and wherein an angle α is provided between an axial direction and an average tangent of the central region of the piston ring in the range of −4 and +4° which is less than or equal to a maximum twist angle of the piston ring in the piston ring groove.

19. A combination of a piston ring and a piston ring groove comprising: a piston ring having a running surface, an upper ring flank, a lower ring flank, and an inner surface, wherein the piston ring has a radius R of predetermined dimension, wherein in a radial section, the running surface has a running surface contour which comprises an upper region, a central region, and a lower region, wherein in the radial section between the upper region and the central region, the running surface contour has an upper transition region, and between the central region and the lower region the running surface contour has a lower transition region, wherein the upper region and the upper transition region in each case form parts of torus surfaces, the upper region of the running surface contour has a curvature radius R.sub.o of predetermined dimension, wherein the central region of the running surface contour has a curvature radius R.sub.m of predetermined dimension, wherein the lower region has a curvature radius R.sub.u of predetermined dimension, which is less than the ring radius R, wherein the upper transition region has a rounding radius Rü, om of predetermined dimension, which is 1/30.sup.th to 1/10th of the ring height h, and wherein the lower transition region has a rounding radius Rü, mu of predetermined dimension, which is 1/30.sup.th to 1/10th of the ring height h; and a piston ring groove in which the ring is received; and wherein an angle β is provided between an axial direction and an averaged tangent of the upper region and wherein angle β is larger than or equal to a sum of an angle α between the axial direction and the averaged tangent of the central region and a value δ, which is between 30′ and 180′, and wherein the angle (α) is less than or equal to a maximum twist angle of the piston ring in the piston ring groove.

Description

THE DRAWINGS

(1) The present invention will be described below by means of schematic illustrations of exemplary embodiments.

(2) FIG. 1 shows a section through a running surface contour of a piston ring according to the invention according to a first embodiment.

(3) FIG. 2 illustrates a section through a running surface contour of a piston ring according to the invention according to a further embodiment.

(4) FIG. 3 shows the angle ratios between an upper region and a central region by means of a running surface contour of a piston ring according to the invention according to a further embodiment.

(5) FIG. 4 illustrates a top view onto a piston ring according to the invention, in order to clarify the piston ring radius.

DETAILED DESCRIPTION

(6) Identical or similar reference numerals will be used below in the drawing as well as in the figures, in order to refer to identical or similar components and elements.

(7) A differentiation will not be made below between the respective curvature radii of the upper, central, and lower region, and the respective regions, because these regions are in each case defined by the curvature radii thereof. The reference numerals R.sub.o, R.sub.m, and R.sub.u thus represent an axial region of the running surface contour as well as the respective n value of the curvature radius thereof.

(8) FIG. 1 shows a section through a running surface contour of a piston ring according to the invention according to a first embodiment. In FIG. 1, the upper section of the contour of the running surface has a curvature radius R.sub.o, which lies between the ring radius or half the ring diameter, respectively, of the installed piston ring and ∞. The upper region of the running surface contour is thereby inclined inwards, and forms a section of a torus surface. The upper region of the running surface contour faces the combustion chamber the most. An upper transition region R.sub.ü,om, which forms a transition to a central region Rm of the piston ring, is located below the upper region R.sub.o. The upper transition region R.sub.ü,om likewise forms a part of a torus surface. The curvature radius R.sub.ü,om is essentially likewise smaller than the curvature radius of the upper region. The curvature radius R.sub.ü,on is essentially likewise smaller than a height h of the piston ring at least by a factor 10. A central region R.sub.m, which is to actually be in contact with an inner cylinder side, connects below the upper transition region R.sub.ü,om. The central region of the contour of the running surface has a curvature radius R.sub.o, which lies between the ring radius or half the ring diameter of the installed piston ring, respectively, and ∞. In FIG. 1, a further transition region, a lower transition region R.sub.ü,mu, which forms a transition to a lower running surface contour section R.sub.u, connects below the central region R.sub.m. As does the upper transition region R.sub.ü,om, the lower transition region R.sub.ü,mu also has a curvature radius, which is small with respect to the height of the piston ring, and which is maximally 1/10 of the height h. A lower region R.sub.u of the running surface contour, the curvature radius of which is smaller than the radius of the piston ring in an installed state, connects below the lower transition region.

(9) Depending on the load scenario, a wear can be distributed in such a way by means of the design that, as a whole, it is less strong than for example in the case of conventional taper-faced or lug-taper-faced rings.

(10) FIG. 2 illustrates a section through a running surface contour of a piston ring according to the invention according to a further embodiment. In FIG. 2, the upper region R.sub.o and the central region R.sub.m have significantly larger curvature radii than in the case of the embodiment of FIG. 1. As in the case of FIG. 1, the upper transition region R.sub.ü,om has a relatively small value. The lower region R.sub.m of the running surface contour has a curvature radius, which is smaller as compared to FIG. 1. The central region R.sub.m of the running surface contour transitions seamlessly into the lower region R.sub.u of the running surface contour. The central region R.sub.m and the lower region R.sub.u of the running surface contour meet at a point, at which the respective tangents of the central region R.sub.m and of the lower region R.sub.u coincide. Due to the significantly smaller curvature radius, the lower transition region as it is used in FIG. 1, can be forgone. The curvature radius of the lower region R.sub.u is thereby at least 10 times smaller than that of the central region. However, the curvature radius of the lower region R.sub.u can also be at least 100-times smaller than that of the central region. In FIG. 2, the central region R.sub.m of the running surface contour transitions steadily and tangent-steadily into the lower region R.sub.u of the running surface contour.

(11) FIG. 3 shows the angle ratios between an upper region R.sub.o and a central region R.sub.m by means of a running surface contour of a piston ring according to the invention according to a further embodiment. In the figure, the upper region R.sub.o has a virtually infinitely large curvature radius. Due to the large curvature radius of the upper region R.sub.o, all tangents at the upper region R.sub.o of the running surface contour coincide in the first approximation. In FIG. 3, the central region R.sub.m likewise has a virtually infinitely large curvature radius, all The large curvature radius of the central region R.sub.m has the effect that all tangents of this section of the running surface contour coincide in the first approximation. A transition region R.sub.ü,om, which reaches a steady and tangent-steady transition between the upper region R.sub.o and the central region R.sub.m, is arranged between the upper region R.sub.o and the central region R.sub.m. Together, the shapes of the upper and central region form a type of bend truncated cone. The lower region R.sub.u is connected steadily and tangent-steadily to the central region R.sub.m via the lower transition region R.sub.ü,mu. The figure thereby shows the difference of the cone angles α of the central region Rm of the running surface contour, and of the cone angle β of the upper region R.sub.o of the running surface contour. The angle β of the upper region R.sub.o thereby lies within and slightly above a value range, as it is known from taper-faced rings. The angle α of the central region R.sub.m lies significantly below the value β, and can be up to 2 angle degrees in a region between a few angular minutes.

(12) FIG. 4 illustrates a top view in an axial direction onto a piston ring according to the invention, whereby the figure clarifies the piston ring radius R.

(13) In the case of all presented embodiments, the running surface contour is always steady and tangent-steady, even in the case of all transitions between the respective regions and between the respective regions and the respective transitions.