The invention relates to a piston for an internal combustion engine having an upper part integrally joined to a lower part having a shaft and at least one pin bore. The upper part including a combustion chamber bowl recess and a piston crown with a crown edge. At least one joint is arranged in the region of a ring zone and in an outer wall of the combustion bowl recess, and the ratio of piston compression height (h.sub.1) and the diameter of the piston (d.sub.1) is less than 0.53.

A piston assembly, piston therefor and methods of construction are provided. The assembly includes a piston head and connecting rod operably coupled thereto via a wrist pin. The piston head has an upper crown with a combustion bowl and an undercrown surface. The lower crown includes axially aligned pin bores receiving the wrist pin. An upper wall of the lower crown has an oil inlet, an oil outlet and a concave, saddle bearing surface that bears against the wrist pin. A toroid-shaped outer cooling gallery is formed between wall portions of the upper and lower crowns, wherein the outer cooling gallery surrounds an inner cooling gallery. The connecting rod is fixed to the wrist pin for conjoint oscillation. The connecting rod has an oil passage in fluid communication with a through hole in the wrist pin to allow oil to flow therethrough into the inner cooling gallery via the oil inlet.

A piston for an internal combustion engine has a lower piston part and an upper piston part connected with the lower piston part by welding to form jointly a circumferential cooling channel having inner and outer circumferential walls. The welding process forms weld seams that curl outwards on the inner and outer circumferential walls. An insert is disposed in the circumferential cooling channel. The insert is placed in the cooling channel prior to welding of the upper and lower piston parts, and is clamped in place by at least one of the weld seams that projects into the cooling channel. This way, no additional fabrication or steps need to be taken to hold the insert securely in place in the cooling channel.

An opposed-piston engine includes pistons, each piston having an annular cavity in the piston's sidewall and positioned between its crown and ring grooves to block transfer of heat from the crown to the piston body.

A method for producing a piston may include aligning at least two piston components along corresponding joining surfaces, activating a laser designed for deep-welding, and aligning a laser beam with a starting point. The method may then include increasing a power density of the laser beam over a first defined path along the joining surfaces to produce a weld seam with an increasing weld seam depth, deep welding along the joining surfaces to produce a deep weld seam with a substantially constant weld seam depth up to a defined end point, and reducing the power density over a second defined path to produce a weld seam with a decreasing weld seam depth. The method may further include overwelding at least part of at least one of the first and second defined paths by a laser designed for heat conduction welding to produce at least one heat conduction weld seam.

A method for producing a piston for an internal combustion engine may include arranging a piston upper part and a piston lower part in a friction welding device. The piston upper part may include a piston head with a combustion recess. The piston lower part may include two mutually opposite skirt elements connected to one another via two mutually opposite pin bosses. The method may also include arranging a deflecting device configured to deflect at least one weld bead one of on and in the friction welding device. The method may further include joining the piston upper part and the piston lower part to one another via friction welding.

A piston capable of operating at a high temperature and consequently contributing to a high in-cylinder temperature, as well as reducing engine oil temperature, when used in an internal combustion engine, is provided. The piston includes an upper portion and a lower portion welded together to present a cooling gallery therebetween. The cooling gallery extends circumferentially around a center axis of the piston and is spaced the center axis. A partition is located in the cooing gallery and extends from one inner surface to another inner surface of the cooling gallery. The partition extends circumferentially around the center axis, and divides the cooling gallery into at least a first gallery portion and a second gallery portion. The partition can be formed as one piece with the upper portion or the lower portion. Alternatively, the partition can be formed as a separate piece from the upper portion and the lower portion.

The invention relates to a piston of an internal combustion engine including at least one peripheral annular groove. The piston includes an upper part and a lower part permanently joined in the region of a joining plane by a friction welding method. The joining plane may be located between the upper flank and the lower flank of the annular groove. A heat-affected zone is generated due to the use of the friction welding and includes at least one of the upper flank or the lower flank of the annular groove. Where multiple annual grooves are used, the joining plane and heat-affected zone may be positioned on alternate annular grooves.

An internal combustion engine piston formed by a lower part connected to an upper part through a form-fitting connection. In one example, the piston lower part has a flat joining area with at least one recess and the piston upper part has a flat joining area including an annular recess. The upper part annual recess extends from the joining area into the lower part, wherein the at least one recess of the lower part is in overlap with a partial area of the annular recess in the upper part after the form-fitting connection. In one example, a sealing element is used between the upper part and the lower part.

A steel piston (10) for an internal combustion engine includes a cooling cavity (20) extending in a rotationally symmetrical manner about the piston axis and at least three annular grooves (12, 14, 16), wherein the third annular groove (16), as viewed from the piston crown (18), has a greater depth (T3) than the depth (T2) of a second annular groove (14).