A piston for a diesel engine includes a piston body having a skirt and crown. The piston body has portions defining an outer combustion bowl and an inner combustion bowl within the piston body through the crown. The outer combustion bowl has a curved annular side wall extending from the crown surface and an annular flat shelf extending from the curved annular side wall. The new stepped bowl design integrates a bottom profile with smoothly varying curvature and a sharp step at the top. The annular flat shelf is recessed a distance in the range of 2.5-4.5 millimeters from a line coplanar with the crown surface. The piston body defines an outer convex curved surface connecting the curved annular side wall to the crown surface. The outer convex curved surface has a radius of curvature in the range of 0.25-0.75 millimeter.

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 piston in which a solid lubricant resin layer made of a resin containing a solid lubricant is formed at a skirt portion. A guide groove absent area where no guide groove is formed, which is provided in a predetermined range of the solid lubricant resin layer at a center portion in a width direction. The guide grooves directing from the both ends in the width direction of the guide groove absent area to both ends in the width direction of the skirt portion. The end portions of the guide grooves extended to end edges of the solid lubricant resin layer to form open ends. The solid lubricant resin layer and the guide grooves are formed at least at a thrust side skirt portion. The guide grooves are formed in a shape inclined upward from the guide groove absent area toward the end edges of the solid lubricant resin layer.

Internal combustion engines having non-circular, preferably rectangular, cross-section pistons and cylinders are disclosed. The pistons may include a skirt with a field of pockets that provide a ringless, non-lubricated, seal equivalent. The pistons also may have a domed piston head with depressions thereon to facilitate the movement of air/charge in the cylinder. The engines also may use multi-stage poppet valves in lieu of conventional poppet valves, and a split crankshaft. The engines may use the pumping motion of the engine piston to supercharge the cylinder with air/charge. The engines also may operate in an inverted orientation in which the piston is closer to the local gravitationally dominant terrestrial body's center of gravity at top dead center position than at bottom dead center position.

Internal combustion engines having multi-stage telescoping poppet valves in lieu of conventional poppet valves are disclosed. The engines may have pistons with a skirt with a field of pockets that provide a ringless, non-lubricated, seal equivalent. The piston heads may include one or more depressions and may be domed to facilitate the movement of air/charge in the cylinder. The engines may also have non-circular, preferably rectangular, cross-section pistons and cylinders. The engines also may include a split crankshaft. The engines may use the pumping motion of the engine piston to supercharge the cylinder with air/charge. The engines also may operate in an inverted orientation in which the piston is closer to the local gravitationally dominant terrestrial body's center of gravity at top dead center position than at bottom dead center position.

Internal combustion engines that use the pumping motion of the engine pistons to supercharge the cylinder with air/charge are disclosed. The pistons may include a skirt with a field of pockets that provide a ringless, non-lubricated, seal equivalent. The piston heads may be domed with one or more depressions to facilitate the movement of air/charge in the cylinder. The engines also may have non-circular, preferably rectangular, cross-section pistons and cylinders. The engines also may use multi-stage poppet valves in lieu of conventional poppet valves, and may include a split crankshaft. The engines also may operate in an inverted orientation in which the piston is closer to the local gravitationally dominant terrestrial body's center of gravity at top dead center position than at bottom dead center position.

A piston for an engine includes a skirt part, and a resin coating film and a recess formed on a surface of the skirt part. A plurality of the resin coating films are discretely arranged in spots on the surface of the skirt part, and a mesh-like groove is formed by the recess provided between the resin coating films. The recess formed on the skirt part between the resin coating films adjacent to each other in a piston circumference direction is set to be adjacent to another resin coating film in a piston moving direction. An end part of the resin coating film in the piston moving direction is formed in a concave shape when seen in a piston radius direction.

A piston for an internal combustion engine has an upper crown portion with a pair of pin bosses depending therefrom, wherein the pin bosses have pin bores axially aligned along a central pin bore axis. A pair of laterally spaced skirt portions are fixedly attached to the pin bosses and depend to a lowermost free edge. At least one of the skirt portions has a recess extending upwardly from the lowermost free edge beyond the central axis of the pin bores.

A piston for assembly with a cylinder of an internal combustion engine. The piston includes a piston body having a longitudinal axis that extends from a crown to a bottom of the piston body. The piston body defines a pin opening having a piston pin axis for receipt of a piston pin. A piston skirt is assembled with and exterior to the piston body. The piston skirt includes a first skirt pocket and a second skirt pocket, wherein the first and second skirt pockets are positioned above the piston pin axis. The piston skirt includes a lower skirt positioned below the piston pin axis. Outer surfaces of the first and second skirt pockets are recessed laterally relative to an outer lower skirt surface of the lower skirt. The outer lower skirt surface of the lower skirt is longitudinally aligned with an outer surface of an upper land.