A method for manufacturing an engine includes: preparing, as a preparing step, a cylinder head having a surface on which a ceiling surface of a combustion chamber is formed; forming, as a film formation step, a thermal insulation film on the ceiling surface; measuring, as a measurement step, a volume of the thermal insulation film; and selecting, as a selection step, from a plurality of ranks set in correspondence with compression heights of pistons, the rank of the piston to be combined with the ceiling surface, the selected rank corresponding to an amount of difference of the measured volume of the thermal insulation film from a design value of the volume of the thermal insulation film.

An engine includes a cylinder block with first and second saw cuts intersecting a block face on opposed sides of a block bore bridge. A cylinder head has third and fourth saw cuts intersecting a head face on opposed sides of a head bore bridge. A gasket is placed between the block and the head. The gasket defines a cooling passage adapted to fluidly connect the first, second, third and fourth saw cuts and cool the interbore region of the engine. The cooling passage has an inlet and a pair of outlets.

A piston for a diesel engine is prepared as a piston for a direct injection engine, a cavity face of the piston is grinded, and a squish face thereof is masked. Next, a high-purity aluminum coating is formed on the cavity face, and the masking of the squish face is removed and the entire area of the piston top face is subjected to an anodizing treatment. Thereafter, the cavity face is masked, and the squish face is subjected to a sealing treatment.

The film forming apparatus includes a mask member and a shield member. The mask member is made of a cylindrical insulation material that can expose inner surfaces of cylinder bores, and mask the inner surface of a crankcase. The shield member is made of a metal material disposed along an inner surface of the mask member.

A cylinder block of an internal combustion engine includes a cylinder bore wall that holds a piston so as to allow the piston to reciprocate. In at least one part of the cylinder bore wall in a cylinder axial direction, the density of a layer located farther from a cylinder head is lower than the density of a layer located closer to the cylinder head in the cylinder axial direction.

A method for producing a groove structure in an internal surface of a pin bore of a piston may include providing a rotatable boring bar with at least one cutting tool; advancing the boring bar while rotating at a first rotational speed in a direction of rotation with a first feed speed into the pin bore and introducing at least one helical first groove of the groove structure with a first depth and a first width into the internal surface; and retracting the boring bar, subsequent to introducing the at least one helical first groove, from the pin bore with a second feed speed while maintaining rotation at a second rotational speed in the direction of rotation; during the retracting of the boring bar at least one helical second groove is introduced into the internal surface.

One of the processes needed for the conversion of a diesel engine so that it can use natural gas as fuel is the reduction of the compression ratio, since the one that the diesel engine originally has is greater than the one needed for the optimal operation with natural gas.

The proposed process consists of adding cold material to the cylinder head or engine head through metallization or electric arc or plasma spraying to form a combustion chamber therein.

An improved surface activation technique improves the adhesion of thermal spray coatings, which is useful for engine cylinder bores. The new method includes compressing the cylinder bore surface to create a surface profile on the surface, such as through rolling a roller along the surface. An engine block is also provided, which includes a plurality of cylinder bores, each cylinder bore having an inner surface, and each inner surface having a surface profile that includes a helical groove and other surface profiles formed in the inner surface. A thermal spray coating is formed on the inner surface of each cylinder bore, the thermal spray coating being adhered to the surface profile of the inner surface. A roller assembly for activating the surface is also provided.

The present invention suppresses leakage of combustion gas from a contact surface. A cylinder head (20) is attached to a cylinder block. The surface (26) of the side of the cylinder head (20) that is attached to the cylinder block includes a first region (AH1) and a second region (AH2) that has higher hardness than the first region (AH1).

Provided is a piston of an internal combustion engine that can reduce a fluid lubrication frictional coefficient on an outer peripheral surface of a skirt portion. The piston of the internal combustion engine includes at least one electrodeposited film on the outer peripheral surface of the skirt portion that is slidably moved relative to an inner wall of a cylinder.