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.

An oil control ring according the present disclosure includes a pair of side rails, and a spacer expander disposed between the pair of side rails. The spacer expander includes a plurality of sets and each set includes a lug part and a rail facing part. For each set, the lug part is in contact with an inner circumferential surface of either of the pair of the side rails, and the rail facing part is provided adjacent to the lug part and faces a side surface of either of the pair of the side rails. The lug part satisfies a following condition (1):

W/H≥1.5   (1)

In condition (1), W indicates a width of the lug part at a position 0.05 mm away from a highest position of the lug part in a direction towards the rail facing part, and H indicates a height difference between a highest position of a region on the rail facing part adjacent to the lug part and the highest position of the lug part.

Under a state in which the combination oil ring is mounted in an oil ring groove before inserted into a cylinder bore, when an inclined surface of an upper ear portion of an expander spacer is held in contact with an inner peripheral surface of an upper segment and an inclined surface of a lower ear portion of the expander spacer is held in contact with an inner peripheral surface of a lower segment, an upper protrusion amount (P1) from an outer peripheral-side end surface of the expander spacer to an outer peripheral surface vertex of the upper segment is larger than a lower protrusion amount (P2) from the outer peripheral-side end surface of the expander spacer to an outer peripheral surface vertex of the lower segment. When the combination oil ring is inserted into the cylinder bore, the sealing performance can be improved to reduce the oil consumption.

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.

Provided is a side rail 1 having an outer peripheral surface 14, an inner peripheral surface 13, a first axial side surface 11, and a second axial side surface 12 parallel to the first axial side surface 11, in which, a beveled portion 30 is provided between the outer peripheral surface 14 and the second axial side surface 12, the beveled portion 30 is formed in a tapered surface having a diameter gradually decreasing from the first axial side surface 11 toward the second axial side surface in an axial direction; a tapered surface 30a is provided between a first tapered surface portion 30a1 with an angle of 10 or more to the axial direction and a second tapered surface portion 30a2 provided between the first tapered surface portion 30a1 and the outer peripheral surface 14 and having a smaller angle of inclination to the axial direction than that of the first tapered surface portion.

Provided is a combined oil ring that further reduces engine oil consumption. A combined oil ring attached to an oil ring groove of a piston includes: a pair of upper and lower side rails each formed into a flat annular shape, and having a slide contact part that comes into sliding contact with a cylinder; and a spacer expander arranged between the pair of upper and lower side rails. In at least the upper side rail of the pair of upper and lower side rails, a cross-sectional shape of the slide contact part along an axial direction of the piston is a tapered shape linearly spreading from upper to lower parts of the piston; the tapered shape is at an angle of 5 to 30 degrees with respect to a central axis of the spacer expander, and has a vertex of the tapered shape within 0.15 mm from a lower end of the side rail; and a part closer to the lower end than the vertex is formed into a curved shape having a curvature of R0.01 to 0.5.

Under a state in which the combination oil ring is mounted in an oil ring groove before inserted into a cylinder bore, when an inclined surface of an upper ear portion of an expander spacer is held in contact with an inner peripheral surface of an upper segment and an inclined surface of a lower ear portion of the expander spacer is held in contact with an inner peripheral surface of a lower segment, an upper protrusion amount (P1) from an outer peripheral-side end surface of the expander spacer to an outer peripheral surface vertex of the upper segment is larger than a lower protrusion amount (P2) from the outer peripheral-side end surface of the expander spacer to an outer peripheral surface vertex of the lower segment. When the combination oil ring is inserted into the cylinder bore, the sealing performance can be improved to reduce the oil consumption.

To provide a combined oil control ring for an automobile engine which is capable of maintaining an outstanding oil control function without causing the occurrence of firm sticking between the spacer expander and the side rails even when the engine is operated over an extended period of time, the crest and the trough of the spacer expander are each provided with a seating tab for pressing an inner peripheral surface of the side rail, a projection for supporting the side rail, and a middle part between the seating tab and the projection, and a ratio (S.sub.min/S.sub.0) is 1.9% or greater, where S.sub.min is a minimum axial cross-sectional area of a space formed between the middle part and the side face of the side rail opposed thereto, and S.sub.0 is an axial cross-sectional area from a groove bottom of an oil ring groove of a piston, to which the combined oil control ring is attached, to an inner wall of a cylinder liner.

Provided are a segment, a combination oil ring, and a manufacturing method for a segment, which are capable of preventing independent rotation of the segment while dealing with reduction in tension of the combination oil ring. Specifically, provided is a segment being slidable in an axial direction of a cylinder under a state in which an inner peripheral surface of the segment is pressed by ear portions formed in an expander spacer in a circumferential direction and an outer periphery side of the segment is pressed against an inner wall of the cylinder, in which the inner peripheral surface of the segment has at least two or more dross-projecting portions in the circumferential direction, and the dross-projecting portions have a projection height of from 4 m to 25 m.