A cylinder of an internal combustion engine, having a cylinder liner and a cylinder piston guided in the cylinder liner The cylinder piston has multiple ring grooves delimited by ring webs and are separated by the ring webs. Each ring grooves receives a compression ring or an oil scraping ring. Each ring groove is delimited by an upper groove flank, a lower groove flank and a groove base, and each piston ring has a lower ring flank, an upper ring flank a ring back and a section which rests against a radially inner running surface of the cylinder liner. A depression is introduced into the lower groove flank of the at least one ring groove or each ring groove which receives a compression ring and/or into the lower ring flank of the piston ring designed as a compression ring.

Provided are an oil ring for an internal combustion engine and a piston assembly including the same, in which the oil ring for an internal combustion engine includes: a compression portion protruding from an upper portion of a body, in close contact with a cylinder inner wall and effectively limiting explosive gas generated in a combustion chamber; a scraper portion protruding from a lower portion of the body, in close contact with the cylinder inner wall and including a nose scraping off oil oversupplied to cylinder inner wall; and an oil suction portion being a space formed between the compression portion and the scraper portion to collect and discharge the oil oversupplied to cylinder inner wall, thereby reducing leakage of high-temperature and high-pressure gas generated in the combustion chamber, and preventing incomplete combustion caused by oil leaked into the combustion chamber.

A piston ring is provided, in particular a compression piston ring having at least one recess with a lower edge running obliquely to the upper piston ring flank on its upper piston ring flank, the ring flank extending radially outward from the piston ring interior and radially inward from the piston ring bearing surface. The piston ring has a chamfer, which is opposite at least one recess. At least one recess and the chamfer extend in the radial direction up to at most the center of the cross-sectional area of the piston ring.

A scraper ring for a piston includes a top surface, a bottom surface, an inner surface, and an outer surface. The top surface has a first planar portion and a first angled portion. The bottom surface has a second planar portion and a second angled portion. The second angled portion is configured to slidably contact the first angled portion to adjust a diameter of the scraper ring. The inner surface connects the top surface to the bottom surface. The outer surface is opposite to the top surface and is configured to form 360 degrees of contact with a wall of a cylinder to substantially limit an amount of oil entering a combustion chamber of the cylinder.

To provide a piston ring for an internal combustion engine, particularly a second compression ring, which has excellent wear resistance and can achieve both lower fuel consumption and efficient combustion. The above-described problem is solved by a piston ring (1) for an internal combustion engine formed so as to have a tapered shape by a peripheral surface (14) that gradually projects outward from a top to a bottom, and a radial cross-sectional shape of a Napier ring. The peripheral surface (14) is constituted by an outer edge end portion (14b) that has a non-tapered shape and comes into sliding contact, as a peripheral sliding surface, with a mating material, an outer peripheral tapered part (14a) formed at a predetermined taper angle (α) above the outer edge end portion (14b), a curved surface part (14c) having a diameter that gradually decreases inward from the outer edge end portion (14b) to a lower end in an axial direction, and a lower end portion (14d) forming a section of the curved surface part (14c). A distance (d2) between a position (A) of the outer edge end portion (14b) and a position (C) of the lower end portion (14d) in a ring axial direction is within a range of 0.001 mm to 0.05 mm, and a contact width (d1) of the outer edge end portion (14b) in the ring axial direction is within a range of 0.01 mm to 0.3 mm.

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 three-part oil scraper ring includes an upper scraper ring (24), a lower scraper ring (26), wherein the scraper rings (24, 26) are held at a distance by an expander spring (34) and pressed radially outwards. The upper scraper ring (24) has a ring body (4) having an upper flank (6), a lower flank (8), a ring inner surface (10) and a ring outer surface (12) which has a ring outer contour (14) in cross-section in axial direction (A). The ring body (4) has a height H which, when viewed in axial direction (A), corresponds to the greatest distance of the upper flank (6) from the lower flank (8). The ring outer contour (14) forms a running surface (16) which has a radius of curvature R which is smaller than the height H of the upper scraper ring (24) by a factor between 1.5 to 6.

To provide a piston ring for an internal combustion engine, particularly a second compression ring, which has excellent wear resistance and can achieve both lower fuel consumption and efficient combustion. The above-described problem is solved by a piston ring (1) for an internal combustion engine formed so as to have a tapered shape by a peripheral surface (14) that gradually projects outward from a top to a bottom, and a radial cross-sectional shape of a Napier ring. The peripheral surface (14) is constituted by an outer edge end portion (14b) that has a non-tapered shape and comes into sliding contact, as a peripheral sliding surface, with a mating material, an outer peripheral tapered part (14a) formed at a predetermined taper angle (α) above the outer edge end portion (14b), a curved surface part (14c) having a diameter that gradually decreases inward from the outer edge end portion (14b) to a lower end in an axial direction, and a lower end portion (14d) forming a section of the curved surface part (14c). A distance (d2) between a position (A) of the outer edge end portion (14b) and a position (C) of the lower end portion (14d) in a ring axial direction is within a range of 0.001 mm to 0.05 mm, and a contact width (d1) of the outer edge end portion (14b) in the ring axial direction is within a range of 0.01 mm to 0.3 mm.

A piston assembly for an internal combustion engine includes a cylinder bore and a piston having exactly two ring grooves, a scraper ring positioned in the upper ring groove, and an oil control ring positioned in the lower ring groove. A constant twist occurs in the scraper ring about a rotational center of the cross-section, the constant twist occurring at each cross-sectional location of the scraper ring about the circumference of the ring and between adjacent free ends of the ring. The oil control ring can be of a multi-segmented U-flex design, with a coil spring mounted in a channel thereof. The combination of the two rings leads to improved sealing and oil control so that the piston can be manufactured with only two rings, thus reducing overall weight and cost.

An oil scraper ring (4) includes a ring element (6), having an upper ring edge (8), a lower ring edge, a ring inner side and a ring outer side (14. The ring element (6) is provided with two opposing contact surfaces (20), between which there is a ring gap (18. The ring element (6) is provided with at least one scraper bar (24, 26) on the ring outer side (14. The oil scraper ring (4) is provided with two recesses (28), each arranged on each contact surface (20), and each adjoining at least on the ring outer side (14), the respective contact surface (20) and the upper ring edge (8).