A piston for a reciprocating piston machine includes a piston crown, a piston recess, and an annular groove formed in the piston crown. The annular groove extends in a radial direction of the piston outwards and a cross-section of the annular groove has a half-teardrop shape. The half-teardrop shape has a first radius and a second radius where the second radius is directly contiguous with the first radius outwards in the radial direction of the piston and where the second radius is greater than the first radius.

A piston for an internal combustion engine may include a ring belt, a groove, and an additional groove. The ring belt may extend along an axial direction. The groove may be arranged on the outer circumference of the ring belt and may be configured to receive an oil scraper ring. The additional groove may be arranged on the outer circumference spaced apart from the groove with respect to the axial direction. The additional groove may include a first groove side axially facing away from the groove and a second groove side axially facing the groove. The first groove side may include an axial step.

A piston for an internal combustion engine may include a ring belt, a groove, and an additional groove. The ring belt may extend along an axial direction. The groove may be arranged on the outer circumference of the ring belt and may be configured to receive an oil scraper ring. The additional groove may be arranged on the outer circumference spaced apart from the groove with respect to the axial direction. The additional groove may include a first groove side axially facing away from the groove and a second groove side axially facing the groove. The first groove side may include an axial step.

A piston for an internal combustion engine is provided. The piston includes a piston bowl defined by a floor surface and a rim wall extending from an outer periphery of the floor surface in a system vertical direction to circumferential surround the floor surface. The piston bowl includes a center portion that extends above the floor surface. A plurality of protrusions extend radially from the center portion and from the floor surface and are spaced apart such that a spray guide is formed between each of the spaced apart plurality of protrusions. Each of the plurality of protrusions and spray guides are tapered so to terminate prior to the rim wall such that a continuous radius portion is formed from a portion of the rim wall and a portion of the floor surface beyond a respective terminating portion of each of the plurality of protrusions and spray guides.

A piston for an internal combustion engine is provided. The piston includes a piston bowl defined by a floor surface and a rim wall extending from an outer periphery of the floor surface in a system vertical direction to circumferential surround the floor surface. The piston bowl includes a center portion that extends above the floor surface. A plurality of protrusions extend radially from the center portion and from the floor surface and are spaced apart such that a spray guide is formed between each of the spaced apart plurality of protrusions. Each of the plurality of protrusions and spray guides are tapered so to terminate prior to the rim wall such that a continuous radius portion is formed from a portion of the rim wall and a portion of the floor surface beyond a respective terminating portion of each of the plurality of protrusions and spray guides.

An anti-polishing ring includes a ring body defining an axis of revolution, and a radial direction that is perpendicular to the axis of revolution, and a circumferential direction about the axis of revolution. The ring body includes an outer circumferential surface, a bottom surface, a top surface, and an inner circumferential surface. The inner circumferential surface defines an inner diameter, the ring body defines a radial thickness measured from the inner circumferential surface to the outer circumferential surface, and a ratio of the radial thickness to the inner diameter ranges from 0.015 to 0.020.

An anti-polishing ring includes a ring body defining an axis of revolution, and a radial direction that is perpendicular to the axis of revolution, and a circumferential direction about the axis of revolution. The ring body includes an outer circumferential surface, a bottom surface, a top surface, and an inner circumferential surface. The inner circumferential surface defines an inner diameter, the ring body defines a radial thickness measured from the inner circumferential surface to the outer circumferential surface, and a ratio of the radial thickness to the inner diameter ranges from 0.015 to 0.020.

Unique apparatuses and methods for scraping deposits from a piston as the piston moves in an upstroke direction and a downstroke direction. An engine assembly includes a cylinder having a cylinder bore, a piston having a crown end, wherein the piston is disposed in the cylinder bore and configured to move in an upstroke direction and a downstroke direction relative to the cylinder bore. The piston includes a first land positioned adjacent the crown end. An antipolishing ring is disposed within the cylinder bore. The antipolishing ring has an outer annular surface and an inner annular surface, the inner annular surface has one or more protrusions configured to scrape the first land when the piston moves in the upstroke direction and the downstroke direction. The protrusions are also configured to scrape the first land when the piston has secondary or lateral motion.

Unique apparatuses and methods for scraping deposits from a piston as the piston moves in an upstroke direction and a downstroke direction. An engine assembly includes a cylinder having a cylinder bore, a piston having a crown end, wherein the piston is disposed in the cylinder bore and configured to move in an upstroke direction and a downstroke direction relative to the cylinder bore. The piston includes a first land positioned adjacent the crown end. An antipolishing ring is disposed within the cylinder bore. The antipolishing ring has an outer annular surface and an inner annular surface, the inner annular surface has one or more protrusions configured to scrape the first land when the piston moves in the upstroke direction and the downstroke direction. The protrusions are also configured to scrape the first land when the piston has secondary or lateral motion.

An engine having a cylinder fastened to the engine ease with the biconcave internal partition, which divides the cylinder into the upper and bottom parts. Sparking plugs are mounted on both sides of the partition. The upper and the bottom parts of the cylinder have side scavenging channels which connect suction spaces to the working spaces of both parts of the cylinder. The upper and bottom parts of the cylinder have inlet and outlet orifices. Inside the upper and inside the bottom part of the cylinder and the upper and bottom piston are placed respectively, while both pistons are directed towards each other by the working surfaces. The pistons are connected by a rod that is led through the linear bearing that is embedded in the partition forming a seal. The connecting rod is fastened to the bottom piston and by its other end it is connected to the crankshaft.