Oil scraper ring and piston ring set for internal combustion engines

Abstract

The present invention relates to an oil scraper ring (4) comprising a ring element (6), the ring element (6) having an upper ring edge (8), a lower ring edge, an inner ring surface, and an outer ring surface (14), the ring element (6) being provided with two opposing contact surfaces (20) with a ring gap (18) between the two contact surfaces (20), the outer ring surface (14) of the ring element (6) being provided with at least one scraper bar (24, 26), the oil scraper ring (4) being provided with two recesses (28), one recess (28) arranged on each contact surface (20), each of the two recesses (28) being adjacent to at least the outer ring surface (14), each contact surface (20), and the upper ring edge (8).

Description

[Technical Field]

[0001] The present invention relates to an oil scraper ring to be fitted to an internal combustion engine, preferably a four-stroke engine, and a piston ring set including such an oil scraper ring. The oil scraper ring of the present invention has ring gaps designed to be different on its upper and lower sides, i.e., on the combustion chamber side and the crankcase side. [Background technology]

[0002] To date, oil scraper rings with a fixed ring gap are known. These fixed ring gaps are usually selected to be as small as possible to achieve maximum oil scraping effectiveness. "Blow-by" gases must pass through this ring gap, but if a narrow ring gap is selected, gas pressure will build up on the ring. This high pressure can cause the second ring to become unstable, negatively affecting the overall function and performance of the ring. Summary of the Invention

[0003] The present invention aims to combine the benefits of a small ring gap associated with the oil scraping effect with a larger ring gap to prevent pressure buildup and second ring instability. The present invention also aims to reduce oil flow upward, i.e., into the combustion chamber, in throttle or overrun modes.

[0004] The present invention is intended to be effective, particularly in operating conditions where the pressure in the combustion chamber drops below ambient pressure, to reduce the amount of oil that can enter the combustion chamber, while at the same time increasing the stability of the second or center (oil control) piston ring by reducing the buildup of gas pressure or gas pressure differential.

[0005] A larger effective gap at the upper edge of the oil scraper ring allows for freer gas flow under high loads when the ring is pressed against the upper edge of the piston ring groove by mass or inertial forces. Less oil can enter the combustion chamber, which reduces the amount of oil burned, thereby reducing particulate emissions, especially after overrun.

[0006] The oil scraper ring according to the invention has the features of claim 1. Advantageous further embodiments are defined in the dependent claims. According to a further aspect of the invention, a piston ring set is described, which includes the oil scraper ring according to the invention and a further oil control ring which also has a specific shape in the ring gap.

[0007] The oil scraper ring of the present invention, with its non-uniform ring gap, also guides a portion of the blow-by oil into the intermediate space between the two scraper bars of the piston ring, allowing it to flow inward through the radial openings of the oil scraper ring to the bottom of the ring groove, and from there through the oil discharge channel or the axial play below it into the crankcase. Note that in this case, the two compression rings located above reduce the blow-by oil to a level where such discharge does not cause significant problems. The blow-by flow, in particular, can entrain oil droplets from the gap between the two oil scraper bars and supply them to the crankcase.

[0008] According to an exemplary embodiment of the present invention, an oil scraper ring comprises a ring element having an upper ring edge, a lower ring edge, a radially located inner ring side, and a radially located outer ring side. The ring element is provided with two contact ends, between which a ring gap exists. The contact ends have opposing contact surfaces. The ring element is provided with at least one scraper bar on the ring outer side. The oil scraper ring according to the present invention comprises two (opposite) recesses in the contact end region, each of which is adjacent to at least the ring outer side, the respective contact surfaces, and the upper ring edge. Each recess thus extends to the region where one corner would be formed by the ring outer side or bar surface, the respective contact surfaces, and the upper ring edge is located. The two opposing recesses located on either side of the ring gap particularly widen the ring gap between the edges of the upper scraper bar.

[0009] One of the two recesses is located at each contact end, so that each recess extends to the outer ring or bar surface, each contact surface, and the upper ring edge. Each recess also extends to the upper scraper bar area.

[0010] This allows the remaining ring gap to be (substantially) 2 to 3 times smaller than that of a conventional ring. The ring gap at the upper edge surface is 2 to 5 times larger than the ring gap in the attached state.

[0011] According to a further exemplary embodiment, the recess is designed symmetrically with respect to the mirror plane of the contact surface, whereby the mirror plane of the contact surface is defined by the contact surface, and the center point and the axial direction of the piston ring preferably lie within the mirror plane.

[0012] In an additional embodiment of the oil scraper ring, the ring element has two scraper bars: an upper scraper bar on the combustion chamber side and a lower scraper bar on the crankcase side. In this case, the recess extends into the area of ​​the upper scraper bar. In this embodiment, the upper scraper ring is circumferentially shorter than the lower scraper ring. This results in a larger ring gap for the upper scraper ring, allowing combustion gases to pass through the larger upper gap into the area between the scraper bars and from there into the space behind the oil scraper ring via radially extending oil passages. In this case, oil droplets from the area between the scraper bars can be transported behind the oil scraper ring. As the piston moves downward, the sealing of the piston ring is further relaxed, so pressure equalization can occur through the oil drain in the oil scraper ring groove and through the crankcase under all operating conditions.

[0013] In a further exemplary embodiment of the oil scraper ring, the recess has the shape of a portion of a sphere, a cylinder, a cone or a rectangle, and is therefore defined by a portion of a spherical, cylindrical, conical or rectangular surface.

[0014] In a further exemplary embodiment of the oil scraper ring, the recess on the contact surface is further adjacent to the contact surface on the inside of the ring. In this embodiment, the recess on the contact surface extends in the area where the edge between the contact surface and the upper ring edge would extend and forms a passage in the radial direction from the inside of the ring to the outside of the ring. In this case, blow-by gases can pass directly behind the ring.

[0015] In a further exemplary embodiment of the oil scraper ring, the oil scraper ring is provided with at least one further radial recess in a region spaced from the contact end, which radial recess extends from the outer side of the ring to the inner side of the ring at the upper ring edge. In this embodiment, this further recess terminates before reaching the inner side of the ring. In a further embodiment, this at least one further recess extends until it reaches the inner side of the ring and forms a channel in the radial direction.

[0016] In an additional embodiment of the oil scraper ring, the at least one further recess or radial recess and the two recesses at the contact area are uniformly distributed around the circumference of the piston ring, and the two recesses at the contact area are considered to be one recess divided by the contact area. In this case, the recesses are arranged at a distance of, for example, 180°, 120°, 90°, 60°, or 30° from each other. In the case of a larger number, the recesses are arranged accordingly.

[0017] In an additional embodiment of the oil scraper ring, the oil scraper ring is designed as a two-part oil scraper ring, in which the oil scraper ring has a circumferentially extending groove on the inner side of the ring, into which at least one expander, such as a hose spring, is fitted.

[0018] In a further embodiment of the three-part oil scraper ring, this effect is ensured by different selection of the "rail" contact play. In a further preferred embodiment, an even number of additional or radial recesses are used. By being arranged closer or more closely together in the circumferential direction, there are no recesses in the rear region of the ring, which reduces the risk of the ring breaking at the point where it is most heavily loaded during assembly. If an even number of additional or radial recesses are used, which are arranged symmetrically with respect to the mirror plane through the ring gap, there are no recesses in the rear region of the ring, which improves the stability of the entire ring.

[0019] According to a further exemplary embodiment of the oil scraper ring, the two recesses and the at least one radial recess each have a different height or depth in the radial direction, the two recesses located directly in the ring gap having the greatest depth (axially), the adjacent radial recesses having a smaller axial depth, and the radial recess located at the rear of the ring being designed to be the flattest.

[0020] According to another exemplary embodiment of the oil scraper ring, the two recesses or at least one radial recess have a depth of 0.1 to 0.3 mm, measured in the axial direction.

[0021] According to a further exemplary embodiment of the oil scraper ring, the two recesses and / or the at least one radial recess are designed so as not to interrupt the upper scraper ring.

[0022] According to a further aspect of the present invention, there is provided a piston ring set comprising the oil scraper ring described above and further comprising at least one oil control ring (or central piston ring), preferably other compression rings. The oil control ring has a control ring element having an upper control ring edge, a lower control ring edge, a radially inwardly positioned inner control ring, and a radially outwardly positioned outer control ring. The control ring element is provided with two control contact edges, with a control ring gap located between the control contact edges. The contact edges have opposing control contact surfaces. The control ring is provided with two recesses in its control contact end region, each of which is adjacent to at least the ring outer side, each contact surface, and the upper ring edge. In the piston ring set, two piston rings are provided in each contact region, and the contact recesses are mutually spaced.

[0023] The present invention will now be described with reference to schematic illustrations of the prior art and exemplary embodiments of the present invention. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a partial view showing the ring gap region of a conventional oil scraper ring. [Figure 2] FIG. 10 is a partial view of an oil scraper ring according to the present invention with an inclined recess in the ring gap. [Figure 3] 1 is a partial view of an oil scraper ring according to the present invention, which has a recess defined by a conical part surface in the ring gap; FIG. [Figure 4] FIG. 1 is a partial view of an oil scraper ring according to the present invention, which has a rectangular recess in the ring gap. [Figure 5] FIG. 1 is a partial view of an oil scraper ring according to the present invention, which has a recess extending from the outside to the inside in the ring gap. [Figure 6] FIG. 10 is a partial view showing the provision of a radial recess that interrupts the upper scraper bar at a location spaced from the ring gap. [Figure 7] FIG. 10 is an illustration showing a further version of the radial recess without interrupting the upper scraper bar. [Figure 8] FIG. 10 is an illustration showing a further version of the radial recess without interrupting the upper scraper bar. [Figure 9] FIG. 10 is an illustration showing a further version of a radial recess extending from the outside to the inside of the ring. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, in both the drawings and the description, the same or similar elements and components are designated with the same or similar reference numerals.

[0026] FIG. 1 shows a partial perspective view of the ring gap 18 region of a conventional oil scraper ring 2. The conventional oil scraper ring 2 comprises a ring element 6 having an upper ring edge 8, a lower edge (not shown), an inner ring side (also not shown), and an outer ring side 14. The ring element 6 is interrupted at a contact point, and two opposing contact surfaces 20 are formed between the ring gap 18. In the figures and in the following, the dimensions of the ring gap are always considered in the installed state. The ring element 6 is provided with at least one scraper bar 24, 26 on the outer ring side. The oil scraper ring according to the prior art and / or the oil scraper ring according to the invention can further be provided with oil passages (not shown for clarity) extending from the outer ring side towards the inner ring side between the scraper bars.

[0027] FIG. 2 shows a partial perspective view of an oil scraper ring 4 according to the invention, which has an inclined recess 28 in the region of the ring gap 18. In the illustrated embodiment, the oil scraper ring 4 according to the invention also comprises a ring element 6. This ring element has an upper ring edge 8, a lower edge (not shown), an inner ring side (not shown), and an outer ring side 14. The ring element 6 has a ring gap 18 defined by two opposing contact surfaces 20. The ring element 6 is provided with at least one scraper bar 24, 26 on the outer ring side 14. In the region of the contact surfaces 20, the oil scraper ring 4 has two recesses 28, i.e., one recess 28 on each contact surface 20. In this case, each recess is adjacent to the outer ring side 14, each contact surface 20, and the upper ring edge 8. In FIG. 2, each recess corresponds approximately to a triangular prism. In this case, blow-by gases that have passed through at least two upper compression rings or oil control rings can flow into the intermediate chamber between the upper scraper bar 24 and the lower scraper bar 26. From there, the blow-by gases flow circumferentially and through oil passages (not shown) toward the bottom of the inner oil scraper ring groove, entraining oil droplets. This allows more oil to be returned toward the crankcase, reducing the amount of oil that enters the combustion chamber, especially in overrun mode.

[0028] 3 shows a partial view of an oil scraper ring according to the invention, which corresponds to FIG. 3 except for the shape of the recess. In this case, instead of a recess with a triangular cross section, a recess defined by a part of a conical surface is used. This shape allows the blow-by gases to flow better towards the intermediate space between the upper scraper bar 24 and the lower scraper bar 26.

[0029] Figure 4 shows further possibilities for configuring the shape of the recess 28. The remainder of Figure 4 corresponds to Figures 2 and 3. The recess 28 in Figure 4 is defined by rectangular parallelepiped surfaces.

[0030] Figure 5 shows further possible embodiments for the ring gap 18 or recess 28. As in Figure 4, the recess 28 in Figure 5 is defined by a rectangular parallelepiped surface, and the recess extends radially completely through the oil scraper ring 4. In the illustrated embodiment, blow-by gases can flow directly through the recesses 24, 26 towards the ring groove bottom.

[0031] Figure 6 shows an embodiment of the oil scraper ring in which the recesses of Figure 4 are used at positions spaced apart from the ring gap and contact surface. These recesses are referred to as radial recesses 34 to distinguish them from the recesses in the ring gap. The illustrated embodiment is also based on the principle of achieving an improved outward-to-inward flow of blow-by gases through the oil scraper ring.

[0032] In Fig. 7, the radial recess 34 of Fig. 6 is designed only to be extremely flat and therefore does not interrupt the upper scraper bar 24 in the axial direction. The radial recess 34 of Fig. 7 extends radially only over a portion of the upper ring edge 8. The radial recess 37 is formed over the entire upper ring edge 8 and therefore only provides a passage to the bottom of the piston ring groove when the oil scraper ring is twisted forward. When the oil scraper ring is twisted backward, the continuous edge between the inner ring surface and the upper ring edge abuts against the upper side of the oil scraper ring groove on the piston, preventing oil from passing radially.

[0033] In Figure 8, the radial recess 34, like the radial recess in Figure 7, is only designed very flat, so that in this case it does not interrupt the upper scraper bar in the axial direction either. In Figure 8, the radial recess 37 extends over the entire upper ring edge 8, so that it forms a passage to the piston ring groove bottom at each twist position of the oil scraper ring.

[0034] In FIG. 9, the radial recess 34 extends to the inside of the ring. [Explanation of symbols]

[0035] 2. Conventional oil scraper ring 4 Oil scraper ring according to the present invention 6 Ring Elements 8 Upper ring edge 14 Outside of the ring 18 Ring Gap 20 Contact surface 24 Upper scraper bar 26 Lower scraper bar 28 Recess 30 Ring gap width 32 recess width 34 Radial recess 36 Radial recess width 38 Piston ring set 40 Oil control ring 42 Oil Control Ring Element 44 Upper control ring edge 50 Control ring outer side 52 Control ring contact surface 54 Control Ring Gap 56 Control ring recess

Claims

1. An oil scraper ring (4) comprising a ring element (6), said ring element (6) comprising: an upper ring edge (8); a lower ring edge; Inside the ring and The outer ring (14) and and The ring element (6) is provided with two opposing contact surfaces (20), between which there is a ring gap (18); At least one scraper bar (24, 26) is provided on the outer ring side (14) of the ring element (6), two recesses (28) are provided in the contact surface (20) area of ​​the oil scraper ring (4), each of the two recesses (28) being adjacent to at least the ring outer side (14), each of the contact surfaces (20) and the upper ring edge (8); The recess (28) is defined by a portion of a spherical surface or has a conical surface; the oil scraper ring (4) is provided with at least one further radial recess (34) in a region spaced from the ring gap (18), the radial recess (34) extending from the outer ring side (14) towards the inner ring side at the upper ring edge (8); The recess terminates before reaching the inside of the ring.

2. 2. An oil scraper ring (4) according to claim 1, wherein the recess (28) extends symmetrically with respect to the mirror surface of the contact surface (20).

3. 3. An oil scraper ring (4) according to claim 1 or 2, wherein, in an installed state, a width (30) of the ring gap (18) is defined as the distance of the contact surfaces (20) in the circumferential direction, and in an installed state of the ring, the sum of the width (32) of the recess (28) and the width of the ring gap (18) in the circumferential direction is 2 to 5 times larger than the width (30) of the ring gap.

4. 4. An oil scraper ring (4) according to claim 1, 2 or 3, characterized in that the ring element (6) has two scraper bars, an upper scraper bar (24) and a lower scraper bar (26), the recess (28) extending into the area of ​​the upper scraper bar (28), and preferably the upper scraper bar (24) being shorter than the lower scraper bar (26) by the width of the recess (32).

5. 5. The oil scraper ring (4) according to claim 1, wherein the at least one radial recess (34) and the two recesses (28) on the ring gap (18) are uniformly distributed around the circumference of the oil scraper ring (4).

6. 6. An oil scraper ring (4) according to any one of claims 1 to 5, characterized in that the two recesses (28) or the radial recesses (34) closer to the ring gap (18) are arranged closer to each other than at the rear of the ring, preferably an even number of radial recesses (34) are used.

7. 7. An oil scraper ring (4) according to claim 1, wherein each of the two recesses (28) and the at least one radial recess (34) closer to the ring gap (18) has a depth that decreases circumferentially towards the rear of the ring.

8. An oil scraper ring (4) according to any one of claims 1 to 7, wherein the two recesses (28) or the at least one radial recess (34) have a depth of 0.1 to 0.3 mm. An oil scraper ring characterized by:

9. 9. An oil scraper ring (4) according to any one of claims 1 to 8, characterized in that the two recesses (28) and / or the at least one radial recess (34) do not interrupt the oil scraper ring.

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