A steel piston (1) for a combustion engine, having an upper part in which a ring section (7) with at least one ring groove (8) is arranged, wherein the upper part is adjoined by a lower part that has two opposing skirt wall sections (2), wherein the two skirt wall sections (2) are connected via two mutually opposite case walls (3), wherein a pin bore (4) surrounded by a piston boss (6) is provided in each case wall (3). In one example, there is at least one aperture (14) or at least one recess in the case wall (3) in the region between the piston boss (6) and the skirt wall section (2).

The present invention relates to pistons (10) for use in internal combustion engines, having: a piston crown (12) which is adjoined by a piston skirt (14), wherein the piston skirt (14) has surfaces (18) which abut the cylinder wall during use of the piston, wherein the surfaces (16) have one or more friction-reducing coatings (18) and wherein depressions (20) are provided in the coating, which are arranged such that the spacing S between each two adjacent depressions (20) along the axial direction (A) of the piston and the width L of the depressions (20) along the axial direction (A) of the piston satisfy the formula S>2L.

A power cylinder system for a reciprocating engine includes a piston configured to move within a cylinder of the reciprocating engine. The system also includes a groove extending circumferentially about the piston and configured to support a ring. An axially-facing surface of the groove has circumferential undulations at ambient temperatures that are configured to compensate for distortions to the groove caused by operation of the reciprocating engine.

In an opposed-piston engine, a piston has a top land. The piston top land has a non-cylindrical shape which affords more clearance with a piston bore to thrust and anti-thrust sides than to front-facing and rear facing sides.

A power cylinder system for a reciprocating engine includes a piston configured to move within a cylinder of the reciprocating engine. The system also includes a groove extending circumferentially about the piston and configured to support a ring. An axially-facing surface of the groove has circumferential undulations at ambient temperatures that are configured to compensate for distortions to the groove caused by operation of the reciprocating engine.

A power cylinder system for a reciprocating engine includes a piston configured to move within a cylinder of the reciprocating engine. The system also includes a groove extending circumferentially about the piston and configured to support a ring. An axially-facing surface of the groove has circumferential undulations at ambient temperatures that are configured to compensate for distortions to the groove caused by operation of the reciprocating engine.

A cast piston for an internal combustion engine is made of an iron-based material and has windows in at least one side wall carrying a piston pin boss. The windows are asymmetric relative to one another on the side of the skirt walls.

A cast piston for an internal combustion engine is made of an iron-based material and has windows in at least one side wall carrying a piston pin boss. The windows are asymmetric relative to one another on the side of the skirt walls.

A piston for an internal combustion engine may include a piston crown, a piston body, and a ring portion. The piston body may have a radially outermost piston outer surface, which may emanate from the piston crown and extend axially and in a circumferential direction. The ring portion may be disposed axially spaced apart from the piston crown. The ring portion may extend axially and in the circumferential direction. The ring portion may include a ring carrier with a ring groove configured to receive a piston ring. The ring portion may further include a radially outer ring portion outer surface that extends in the circumferential direction. The ring portion outer surface may be disposed radially to an inside relative to the piston outer surface. The piston outer surface may extend elliptically in the circumferential direction. The ring portion outer surface may extend rotation-symmetrically in the circumferential direction.

A coating composition for forming a coating film including particles and a resin binder is so configured that a content of the particles in the coating film is more than 30 vol%, the coating composition includes the particles, a raw resin of the resin binder, and a solvent, and a ratio V/D is 2.5 or less, where V is a volatilization rate (g/m.sup.2.Math.s) of the solvent, and D is a diffusion coefficient (10.sup.−9 m.sup.2/s) of the solvent in the coating composition.