A multi-piece oil scraper piston ring includes a slotted spring element and at least one lamella element which is operatively connected to the slotted spring element and provided with a joint, the spring element being designed as a meander spring that axially receives and radially supports the lamella element, the two end regions of the meander spring being provided with legs that extend approximately parallel to one another and the axial length of which is designed such that the legs at least partially engage in the joint of the lamella element.

A play-free oil scraper ring has a cross section with a running surface leg having at least one scraper web that is situated on a running surface, an upper piston ring flank leg that is connected to the running surface leg, and the upper surface of which forms an upper piston ring flank. A lower piston ring flank leg is likewise connected to the running surface leg, the lower surface of which forms a lower piston ring flank. The upper and/or the lower piston ring flank leg are/is elastic, taper(s) inwardly in the radial direction, and their/its piston ring flank(s) essentially form(s) a conical surface in an uninstalled state. The uninstalled piston ring has an axial height that exceeds a width of a piston ring groove for which the piston ring is intended.

The invention relates to an MF expander spring 20 for a three-part oil scraper ring 2, 4, 6, 8. It comprises a steel band, which is corrugated in a trapezoidal or diamond-shaped manner in the axial direction, wherein the MF expansion spring 20 has axial protrusions 30, 32, which are intended to abut in each case against an upper or lower oil scraper ring 34, 36 from the inside in the radial direction, in order to press said axial protrusions outwards against an inner cylinder surface, comprises upper flat sections 24, which are intended to abut against an upper scraper ring 34, 36 of a three-part oil scraper ring 2, 4, 6, 8 in the axial direction, comprises lower flat sections 23, which are intended to abut against a lower scraper ring 34 of the three-part oil scraper ring 2, 4, 6, 8 in the axial direction, and comprises flank sections 26, 28, which extend between the upper flat sections 24 and the lower flat sections 22. At least every second flank section 26 forms an acute angle (α) with the associated upper or lower flat sections 22, 24.

In this piston ring combination, a second outer peripheral surface, which is the outer peripheral surface of a second ring, has a second protruding surface curved into a convex shape, and a pair of third outer peripheral surfaces, which are the outer peripheral surfaces of a pair of segments, each have a third outer peripheral area in which a third protruding surface is formed, the third protruding surfaces being curved into convex shapes. In at least one of the pair of third outer peripheral surfaces, the peripheral edge on a crank-chamber side is positioned farther outward in the diametrical direction than the peripheral edge on a combustion-chamber side, and a peak of the third protruding surface is positioned nearer to the crank chamber than the center of the third outer peripheral surface.

A multi-piece piston ring includes an upper scraper ring 10 comprising two flank surfaces, an outer scraping surface/edge, and an inner spring contact surface. A lower support ring 4 includes two flank surfaces, an outer spring contact surface, and a support ring inner surface. An expander spring/spiral spring 8, which, on an upper and lower side, is operational to abut against a respective lower flank surface of the upper scraper ring 10 and against the upper flank surface of the support ring 4. Scraper ring contact projections protruding upwards on an inner spring side, and support ring contact projections protruding downwards on an outer spring side, wherein the scraper ring contact projections are to each abut against the inner spring contact surface of the scraper ring 10, and support ring contact projections protruding downwards are to abut against the outer spring contact surface.

The present invention relates to an oil scraper ring spring (1) for an oil scraper ring (3) comprising the oil scraper ring spring (1), an upper and a lower metal ring (21, 22) and provided for being mounted in an oil ring groove of a piston. The oil scraper ring spring (1) comprises a plurality of upper regions (5) and a plurality of lower regions (7) arranged in alternating manner in a circumferential direction so as to be spaced in an axial direction; connecting regions (9) each connecting the adjacent upper and lower regions (5, 7) to each other. Each of the upper and lower regions (5, 7) comprises: a nose section (13) disposed at the inner circumferential end and adapted to push the respectively abutting upper or lower metal ring (21, 22) radially outwardly, and having a through-opening (15); an abutment section (17) extending radially between the nose section (13) and the outer circumferential end and configured to have the respective upper metal ring (21) abutting thereon or the respective lower metal ring (22) abutting thereon; wherein the abutment section (17) has a recess (19) formed therein the depth of which, relative to the abutting area of the abutment section (17), increases in the radial direction towards the through-opening (15), and the width of which increases in the radial direction towards the through-opening (15); wherein the recess (19) in the abutment section (17) has substantially the shape of a half-funnel; wherein the half-funnel has an opening angle of 30° to 150°, in particular of 30° to 60°, or wherein the upper side edges of the recess (19) span an angular segment of 5-50°, in particular 5-15°; and wherein increasing the depth and width of the recess (19) radially inwardly together with the through-opening (15) serves to increase and accelerate the oil flow to the piston center.

A multi-piece piston ring includes an upper scraper ring 10 comprising two flank surfaces, an outer scraping surface/edge, and an inner spring contact surface. A lower support ring 4 includes two flank surfaces, an outer spring contact surface, and a support ring inner surface. An expander spring/spiral spring 8, which, on an upper and lower side, is operational to abut against a respective lower flank surface of the upper scraper ring 10 and against the upper flank surface of the support ring 4. Scraper ring contact projections protruding upwards on an inner spring side, and support ring contact projections protruding downwards on an outer spring side, wherein the scraper ring contact projections are to each abut against the inner spring contact surface of the scraper ring 10, and support ring contact projections protruding downwards are to abut against the outer spring contact surface.

A three-piece piston oil control ring 2 has an upper, disc-shaped scraping ring 4, a lower, disc-shaped stabilising ring 6, and a circular expander 8 which has projections 10 protruding in the axial direction on an inner face. The circular expander 8 is arranged between the upper scraping ring 4 and the lower stabilising ring 6, wherein the projections 10 each bear inwardly against an inner face 14 of the scraping ring 4 or against an inner face 16 of the stabilising ring 6. An outer radius 18 of the scraping ring 4 is greater than an outer radius 20 of the lower stabilising ring 6, so that there is a radius difference δ between the scraping ring 4 and the stabilising ring 6.

In this piston ring combination, a second outer peripheral surface, which is the outer peripheral surface of a second ring, has a second protruding surface curved into a convex shape, and a pair of third outer peripheral surfaces, which are the outer peripheral surfaces of a pair of segments, each have a third outer peripheral area in which a third protruding surface is formed, the third protruding surfaces being curved into convex shapes. In at least one of the pair of third outer peripheral surfaces, the peripheral edge on a crank-chamber side is positioned farther outward in the diametrical direction than the peripheral edge on a combustion-chamber side, and a peak of the third protruding surface is positioned nearer to the crank chamber than the center of the third outer peripheral surface.

The invention relates to an MF expander spring 20 for a three-part oil scraper ring 2, 4, 6, 8. It comprises a steel band, which is corrugated in a trapezoidal or diamond-shaped manner in the axial direction, wherein the MF expansion spring 20 has axial protrusions 30, 32, which are intended to abut in each case against an upper or lower oil scraper ring 34, 36 from the inside in the radial direction, in order to press said axial protrusions outwards against an inner cylinder surface, comprises upper flat sections 24, which are intended to abut against an upper scraper ring 34, 36 of a three-part oil scraper ring 2, 4, 6, 8 in the axial direction, comprises lower flat sections 23, which are intended to abut against a lower scraper ring 34 of the three-part oil scraper ring 2, 4, 6, 8 in the axial direction, and comprises flank sections 26, 28, which extend between the upper flat sections 24 and the lower flat sections 22. At least every second flank section 26 forms an acute angle () with the associated upper or lower flat sections 22, 24.