A method of manufacturing an engine piston may include performing upper-body formation for forming an upper body as an upper portion of a piston body by pressing a powder-type sintered material, performing lower-body formation for forming a lower body as a lower portion of the piston body by pressing a powder-type sintered material, performing bonding for forming the piston body by providing a brazing material between the upper body and the lower body and brazing the upper body and the lower body to each other while sintering a sintered material, performing machining for removing pores from the surface of the piston body by machining the surface, and performing heat treatment for forming a passive film by performing at least one of nitriding heat treatment or oxidation heat treatment on the surface of the piston body.

There is provided an engine piston including a piston main body and a piston pin. The piston main body includes a piston head that has a crown surface forming a part of a wall of a combustion chamber and a pair of pin bosses that are connected to a side of the piston head opposite to the crown surface, arranged with a distance between the pin bosses in a first direction included in a radial direction of the piston head, and respectively have pin holes for the piston pin, the pin holes penetrating in the first direction. The piston head includes a pair of hollow parts extending in a second direction orthogonal to both the axial direction and the first direction at a position between the crown surface and each of the pin holes in the axial direction and a particulate filler filled in the pair of hollow parts.

There is provided a method for manufacturing a piston for a vehicle engine, including: a piston assembling step of forming a piston assembly by assembling a first piston part, a bonding member and a second piston part, wherein the first piston part has two or more bonding surfaces separated from each other and extended in a circumferential direction, and the second piston part has two or more bonding surfaces separated from each other and extended in the circumferential direction; a piston diffusion brazing step of diffusion brazing the first piston part, the bonding member and the second piston part under an open atmosphere by heating the formed piston assembly; and a piston cooling step of cooling a piston unit formed by diffusion brazing the first piston part, the bonding member and the second piston part. The piston diffusion brazing step is performed in a piston manufacturing device which includes a partially opened heating zone, a heater for providing heat into the heating zone, and a moving unit moved in one direction in the heating zone. In the piston diffusion brazing step, the piston assembly is heated while being moved at a predetermined speed through the heating zone in one direction by the moving unit.

Provided is an engine, including: a cylinder including a cylinder liner; a piston provided inside the cylinder liner; a piston ring provided on the piston; a contact detector configured to detect a contact between a step formed in an inner peripheral surface of the cylinder liner and the piston ring; and a compression ratio controller configured to control a top dead center position of the piston so that the piston ring at the top dead center position is located on a combustion chamber side with respect to the step when the contact is detected.

A piston for an internal combustion engine may include two pin bosses configured to receive a gudgeon pin. The two pin bosses may respectively include a nadir pocket of at least two nadir pockets at =180 and extending outward from a piston axis. The at least two nadir pockets may have a respective length that is smaller than a length of a respective pin boss of the at least two pin bosses. The piston may also include a pin boss axis that is axially offset from the piston axis by 0.1-1.0 mm.

A steel piston with anti-coking design features is provided. The piston includes an upper crown portion and a lower crown portion forming an outer cooling gallery therebetween. The outer cooling gallery is substantially closed except for an oil inlet, oil outlet, and optional oil passage(s) to a central cooling gallery. According to one embodiment, at least one anti-coking insert is disposed in the outer cooling gallery and sized to prevent escaping through the oil inlet or the oil outlet. For example, the insert(s) can comprise a helical coil, a plurality of steel balls, coil springs, or chips formed of polymer with abrasive filler. Alternatively, an outer gallery floor to the outer cooling gallery includes a plurality of anti-coking openings disposed sequentially in decreasing spaced relation from one another, or anti-coking openings with varying lengths.

An internal combustion may include a cylinder having a first combustion chamber at one end and a second combustion chamber at an opposing end, first and second cylinder heads located at an end of the first and second combustion chambers, respectively, and a double-faced piston slidably mounted within the cylinder. The piston may be configured to move in the cylinder in a first stroke from one end to another. The first stroke may include an expansion stroke portion and a non-expansion stroke portion. The non-expansion stroke portion may include a momentum stroke portion. The non-expansion stroke portion may include a scavenging phase. The engine may further include first and second piston rod portions extending from opposite faces of the piston. Passageways in the piston rod portions may be configured to communicate gases between a combustion chamber and other locations.

A piston for an internal combustion engine includes: a crown; a skirt extending from the crown; an oil gallery extending annularly within the crown, and having an inlet and an outlet; and a structure mounted at the outlet of the oil gallery to induce oil shaking.

There is provided a method for manufacturing a piston, including: a piston assembling step of forming a piston assembly by assembling a first piston part, a bonding member and a second piston part, wherein the first piston part has two or more bonding surfaces separate from each other and extending in a circumferential direction, and the second piston part has two or more bonding surfaces separate from each other and extending in the circumferential direction; a piston diffusion brazing step of diffusion brazing the first piston part, the bonding member and the second piston part under an open atmosphere by heating the formed piston assembly; and a piston cooling step of cooling a piston unit formed by diffusion brazing the first piston part, the bonding member and the second piston part. The piston diffusion brazing step is performed in a piston manufacturing device which includes a partially opened heating zone, a heater for providing heat into the heating zone, and a moving unit moved in one direction in the heating zone. In the piston diffusion brazing step, the piston assembly is heated while being moved at a predetermined speed through the heating zone in one direction by the moving unit.

A piston for an internal combustion engine includes: a crown; a skirt extending from the crown; an oil gallery extending annularly within the crown, and having an inlet and an outlet; and a structure mounted at the outlet of the oil gallery to induce oil shaking.