A piston and methods for constructing a piston for use in an internal combustion engine are presented wherein the piston includes a cylindrical body extending from the crown. The cylindrical body defines a ring groove, and a portion of the cylindrical body defines a non-circular cross-section below the ring groove. The ring groove is configured to correspond with an associated sealing ring. The non-circular cross-section creates a gap between the cylindrical body and an associated cylinder wall enabling a quantity of oil to pass from an annular region between the cylindrical body and the associated cylinder wall.

A piston capable of withstanding high temperatures and extreme conditions of a combustion chamber of an internal combustion engine and manufactured with reduced costs is provided. The method of manufacturing the piston includes casting or forging the bulk of the piston as a single-piece with an open cooling gallery from an economical first material, such as steel, cast iron, or aluminum. The method further includes forming a portion of a combustion bowl surface, which is a small area of the piston directly exposed to the combustion chamber, from a second material by additive machining. The second material has a higher thermal conductivity and higher resistance to oxidation, erosion, and oil coking, compared to the first material. The additive machining process is efficient and creates little waste, which further reduces production costs.

A galleryless piston for an internal combustion engine and method of construction thereof are provided. The piston has a monolithic piston body extending along a central longitudinal axis. The piston body has an upper wall forming an upper combustion surface with first and second portions, with the first portion extending annularly along an outer periphery of the upper wall and the second portion forming a combustion bowl. The upper wall has an undercrown surface on an underside of the combustion bowl directly opposite the second portion of the upper combustion surface. The undercrown surface has an openly exposed 2-dimensional surface area, as viewed looking along the central longitudinal axis, between about 35-60 percent of an area defined by a maximum outer diameter of the piston body, thereby providing an expansive area against which oil being splashed or sprayed can freely contact to cool the piston.

A two-stroke internal combustion engine includes at least one gaseous communication charge passage between a crankcase chamber and a combustion chamber of the engine and a piston to open and close the top end of the transfer passage. The air inlet port to the transfer passage for stratified scavenging is opened and closed by the piston that has passages and cutouts. The charge inlet to the crankcase chamber is opened and closed by the piston. The air inlet passage is substantially asymmetrical to the layout of the transfer passages and are closer to one transfer passage compared to the other. The internal air passage in the piston is substantially parallel to the piston pin and the single air inlet passage is laterally off-set from the air-fuel inlet passage. The transfer passages are cover by plates to make them closed passages having opening at the transfer port in the cylinder and opening in the crankcase chamber for periodical gaseous communication between the crankcase chamber and the combustion chamber. The cover plate is a single piece covering the transfer passage channel along the cylinder and the crankcase. The air channel in the piston is below the piston crown and at least portion is above the piston pin. A spiraling transfer passage in the cylinder cavity is longer than the length of the transfer passage in a conventional stratified two-stroke engine.

A piston for an internal combustion engine is provided. The piston includes a piston body which is made of steel. The piston body has a crown portion with an upper combustion surface, a pair of skirts which depend from the crown surface, a pair of pin bosses for receiving a wrist pin and a plurality of pin boss bridges which extend from the pin bosses to the skirts. Each of the pin boss bridges extends axially to a lower end which is opposite of the crown portion and has a rib with an increased thickness at its lower end. At least one of the pin boss bridges has a generally flat counter-bore surface for providing a reference location for machining of the piston body.

The present invention provides piston production device and piston production method capable of surely holding friction-resistant ring regardless of presence or absence of decrease in accuracy of outside diameter of holding pin. Device has lower mold provided thereinside with cavity for forming piston and having opening, upper mold provided movably to open/close opening of cavity, and three holding pins rotatably supported by holding holes of upper mold and having top end portions protruding from lower surface of upper mold. Top end portions have flat holding surfaces formed by cutting tip end sides of top end portions in half from tip end edges along axial direction and stepped surfaces formed from upper ends of holding surfaces toward radial direction. By rotating holding pins in synchronization with each other in the same direction, friction-resistant ring is held by three points of holding surfaces.

Steel pistons used in many internal combustion engines are generally composed of a skirt and a crown. The skirt's function is to reduce the lateral and rotational movement of the piston in the cylinder while the engine is in operation. Lateral and rotational frictional forces imparted to a piston during engine operation cause the piston to scrape off the lubricating oil film present on the cylinder wall. The reduced oil film thickness increases piston and cylinder wall wear due to metal to metal contact. The subsequent metal to metal contact produces a phenomenon called scuffing. This disclosure incorporates several design modifications to the piston and results in a significant reduction of the lateral and rotational motion of the piston during engine operation. The reduction of piston motion reduces the amount of oil film removed from the cylinder wall and increases lubrication efficiency. The Increased lubrication efficiency realized reduces frictional wear power loss and scuffing.