A piston expander and transfer valve for the controlled metering of a pressurised working fluid into an expansion chamber as part of an energy conversion device, and in particular as part of a heat to power conversion device employing a rankine thermodynamic cycle. The piston expander comprising a cylinder having an inlet manifold connected to an aperture in the cylinder's inlet aperture, a piston movable within the cylinder, and a transfer valve assembly movable under the action of changing gas pressure in the main chamber of the piston expander.

A piston ring includes a body portion presenting a running surface, and a spring member disposed between the body portion and a ring groove of a piston. A running surface of the piston ring presents an upper rail, a lower rail, and a fulcrum disposed between the rails and each extending radially outwardly. An outermost tip of the fulcrum is disposed radially outwardly relative to an outermost surface of the rails, and the running surface presents a convex shape along the fulcrum. The fulcrum contacts an oil film applied to a cylinder wall as the piston reciprocates along the cylinder wall. The spring member presses the body portion of the piston ring toward the cylinder wall and causes the body portion to pivot about the fulcrum to provide for improved control of the oil film, less friction, and reduced oil consumption.

The oil control ring (2) extends in a circumferential direction (2x) about a center (2l) and has a longitudinal axis (2m) that passes through the center (2l), wherein the oil control ring (2) has an end face (2d) that faces the center (2l), and wherein the oil control ring (2) has a first lateral surface (2s), a second lateral surface (2t), and an outer surface (2u) facing away from the center (2l), wherein the oil control ring (2) has a plurality of channels (2c) extending toward the center (2l) on the first lateral surface (2s), said channels being arranged at mutual distances in the circumferential direction (2x) and extending over the entire width of the first lateral surface (2s) in the radial direction and thereby forming a fluid-conducting connection between the end face (2d) and the outer surface (2u), and wherein crown parts (2i) extending in the circumferential direction (2x) are arranged between pairs of channels (2c), wherein each crown part (2i) protrudes beyond the respective channel (2c) in the direction of extent of the longitudinal axis (2m) and forms a lateral channel surface (2w) for the channel (2c), wherein at least one of the crown parts (5i) is designed as a long crown part (2p) and extends over an angular range (α) between 60 degrees and 350 degrees in the circumferential direction (2x). 212×2121.

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.

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 with an oil return channel may include a piston head, a piston skirt, and an oil return hole. The piston head may include a ring groove. The piston skirt may be connected to the piston head. The piston skirt may have a surface including a concave face window. A connection between the face window and the ring groove may form a residual ring bank. The oil return hole may be formed by milling on the residual ring bank. The oil return hole may connect the ring groove close to the piston skirt with the face window. A depth of the oil return hole may be greater than a depth of the ring groove.

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 for an internal combustion engine may include at least one oil ring groove configured to receive an oil scraper ring. The at least one oil ring groove may have an upper groove flank, a lower groove flank, and a groove base. The at least one oil ring groove may be structured to be asymmetrical and deeper in a radial direction in a region of the lower groove flank. The piston may also include an oil outflow channel structured and arranged to fluidically communicate with an oil collecting chamber disposed in a spine of the oil scraper ring. A connecting point between at least one of (i) the at least one oil ring groove and the oil outflow channel, and (ii) the oil collecting chamber and the oil outflow channel may be disposed exclusively in the lower groove flank.

A piston for an internal combustion engine may include at least one oil ring groove configured to receive an oil scraper ring. The at least one oil ring groove may have an upper groove flank, a lower groove flank, and a groove base. The at least one oil ring groove may be structured to be asymmetrical and deeper in a radial direction in a region of the lower groove flank. The piston may also include an oil outflow channel structured and arranged to fluidically communicate with an oil collecting chamber disposed in a spine of the oil scraper ring. A connecting point between at least one of (i) the at least one oil ring groove and the oil outflow channel, and (ii) the oil collecting chamber and the oil outflow channel may be disposed exclusively in the lower groove flank.