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.

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.

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.

An engine includes a housing and a combustion assembly. The combustion assembly includes an annular bore and a combustion piston assembly disposed within the annular bore. The combustion piston assembly includes a set of pistons, a first sealing ring connected to each piston and a second sealing ring connected to each piston. The second sealing ring is configured to provide selective access between the annular bore and at least one fluid conduit carried by the engine. The engine includes at least one valve configured to move between a first position within the annular bore to allow the combustion piston assembly to travel within the annular bore from a first location proximate to the at least one valve to a second location distal to the at least one valve and a second position within the annular bore to define a combustion chamber.

An engine includes a housing and a combustion assembly. The combustion assembly includes an annular bore and a combustion piston assembly disposed within the annular bore. The combustion piston assembly includes a set of pistons, a first sealing ring connected to each piston and a second sealing ring connected to each piston. The second sealing ring is configured to provide selective access between the annular bore and at least one fluid conduit carried by the engine. The engine includes at least one valve configured to move between a first position within the annular bore to allow the combustion piston assembly to travel within the annular bore from a first location proximate to the at least one valve to a second location distal to the at least one valve and a second position within the annular bore to define a combustion chamber.

A piston assembly for an internal combustion engine of a motor includes a piston head having an outer diameter surface spaced a first distance from the longitudinal axis and an annular surface spaced a second distance from the longitudinal axis, with the second distance being less than the first distance. Upper and lower walls extend between the annular surface and the outer diameter surface so as to define an annular groove in the outer diameter surface. A piston ring is received within the annular groove and includes an inner diameter surface facing the annular surface of the piston head. The inner diameter surface of the piston ring and the annular surface of the piston head cooperate with one another to define a plurality of pockets angularly spaced from one another about the longitudinal axis and configured to receive oil.

A piston assembly for an internal combustion engine of a motor includes a piston head having an outer diameter surface spaced a first distance from the longitudinal axis and an annular surface spaced a second distance from the longitudinal axis, with the second distance being less than the first distance. Upper and lower walls extend between the annular surface and the outer diameter surface so as to define an annular groove in the outer diameter surface. A piston ring is received within the annular groove and includes an inner diameter surface facing the annular surface of the piston head. The inner diameter surface of the piston ring and the annular surface of the piston head cooperate with one another to define a plurality of pockets angularly spaced from one another about the longitudinal axis and configured to receive oil.

A seal assembly includes a tensionable annular member and a gap seal annular member that are axially juxtaposed and configured to be carried by one of a pair of coaxially movable components for sealingly engaging another one of the pair of components. The tensionable annular member includes first and second radial surfaces, an inner surface, and an outer contact surface. Rounded bottom grooves are formed across the first radial surface from the outer contact surface to the inner surface. In another embodiment, notches are formed across the inner surface from the first radial surface to the second radial surface.

A bearing assembly comprising a first component and a second component, the first and second components being slidably disposed with respect to each other, wherein the first component slides relative to the second component in a first direction, wherein the first component comprises a plurality of first recesses formed in a first surface facing the second component, wherein the first recesses are distributed in a second direction perpendicular to the first direction with neighboring first recesses being spaced apart in the second direction with a first spacing, wherein the second component comprises a plurality of second recesses formed in a second surface facing the first surface of the first component, wherein the second recesses are distributed in the second direction with neighboring second recesses being spaced apart in the second direction with a second spacing, wherein the first recesses are sized to fit within the second spacings and the second recesses are sized to fit within the first spacings, and wherein the first and second components are urged into a relative position in the second direction in which the first and second recesses do not overlap one another.

A gas compressor compressing gas includes a cylinder liner, a piston member, and a first sliding member. The piston member includes a piston reciprocating in an inner space of the cylinder liner, and a piston rod connected to the piston. The first sliding member is made of a resin, has a ring shape, and is provided on one of the piston member and the cylinder liner. The first sliding member slides relatively against a reception member while another of the piston member and the cylinder liner serves as the reception member that receives sliding. An amorphous carbon film is formed on a sliding surface of each of the first sliding member and the reception member. A carbon content in the amorphous carbon film formed on each of the sliding surfaces is larger in its surface part than in its inner part on an inner side of the surface part.