In a fuel injection valve that is inserted along a shape of an attachment hole formed in a cylinder head and that directly injects fuel supplied from a fuel supply section into a combustion chamber via a stepped section, the fuel supply section includes: a fuel cup, an end of which has a tapered section; a seal ring that prevents leakage of the fuel to the outside; and a support ring that supports the seal ring, the stepped section includes: a nozzle that injects the fuel into the combustion chamber; and an attachment shaft that has a larger radius than the nozzle, and a first gap in an axial direction between the tapered section and the support ring is larger than a second gap in the axial direction between the attachment hole and the attachment shaft.

An intake cam is positioned between first and second shaft supports that support an intake camshaft. An exhaust cam is positioned between third and fourth shaft supports that support an exhaust camshaft. An ignition plug unit extends between the intake camshaft and the exhaust camshaft and inward of the intake cam and the exhaust cam with a cylinder axis defining a reference position. A cylinder head includes a joint plane that is joined to a cylinder body. In a case where a virtual plane is defined by the joint plane and is perpendicular or substantially perpendicular to the cylinder axis, a distance between a portion, closest to the virtual plane, of the intake camshaft and the virtual plane is less than a distance between a portion, farthest from the virtual plane, of the intake port and the virtual plane.

An engine power unit includes a crankcase, a cylinder body, and a cylinder head sequentially stacked and fastened with each other. A cam shaft holder is fastened to the cylinder head to rotatably support a cam shaft of an engine valve operating mechanism. A cylinder head cover covers the cylinder head and the cam shaft holder. Fastening bolts penetrate the cylinder head cover and the cam shaft holder to be screwed into the cylinder head. Pressing surfaces are formed on the inner surface of the cylinder head cover. The pressing surfaces are abutted against and press the cam shaft holder to the cylinder head. Thus, rigidity around the cylinder head is enhanced, and a weight reduction of the power unit is achieved.

A cylinder head assembly for an internal combustion engine includes a cast cylinder head defining a combustion chamber and fabricated from a first material, and an internal support structure at least partially encapsulated within the cast cylinder head. The internal support structure is fabricated from a thermal strain and fatigue resistant second material, different from the first material, such that during engine operation, thermal and mechanical loads are transferred to the internal support structure to reduce combustion chamber displacement. The internal support structure and the cylinder head are bonded via a hot isostatic pressing (HIP) process to eliminate internal porosity and gaps therebetween.

The cylinder head 3 includes: a lower deck; a wall portion including an upper deck and a lower deck; an upper deck that is provided above the lower deck so as to face the lower deck and that defines a cooling water flow space between the lower deck and the upper deck; and a wall portion that is formed between the lower deck and the upper deck and includes a valve-hole forming wall 40 forming an intake valve hole and an exhaust valve hole which are opened into a lower surface of the lower deck. The lower deck includes: a cooling water introduction hole that passes through the lower deck in a vertical direction so as to extend in a circumferential direction of a virtual circle VC surrounding a valve-hole forming wall in a plan view; and a rib that projects from an upper surface of the lower deck.

A piston for an internal combustion engine includes a plurality of valve pockets formed in a piston rim, the valve pockets forming fluid flow paths through the piston rim. Each of the valve pockets includes a central step standing proud of a pocket floor to limit a fluid flow area through the pocket and slow combustion gas flow from a combustion bowl toward a cylinder liner and thereby reduce displacement of an engine oil film thereon.

A cylinder head of a multi-cylinder engine is provided, the cylinder head including a plurality of ceiling parts for respective cylinders, and a water jacket. Each ceiling part is connected to an intake port including a primary port and a secondary port aligned in a cylinder-row direction, and is attached with an in-cylinder pressure sensor. A plug is attached to a hollow part of the cylinder head corresponding to a core print provided to a core of the water jacket, and is disposed at a position corresponding to a location between certain cylinders. The in-cylinder pressure sensor is attached at a position on an opposite side from the plug with respect to a cylinder center axis in the cylinder-row direction. Positions of the primary and secondary ports connected to each ceiling part are interchanged in the cylinder-row direction according to the position of the in-cylinder pressure sensor.

A spark ignition engine includes: a pre-chamber (PC); a main chamber (MC); and a cylinder head coupled with a water jacket. The PC includes: a spark plug; and a PC body. The spark plug is surrounded by a jacket with thermal-conductive substance. The thermal-conductive substance is solid at room temperature and liquid at working temperature of the PC. At working temperature of the PC, the liquid thermal-conductive substance conducts heat from the spark plug to the water jacket. The PC body is coated with a layer of non-thermal-conductive substance.

A cylinder head includes a hydraulic lash adjuster attachment portion provided with a hydraulic lash adjuster bore in which a hydraulic lash adjuster is inserted; a main oil provided at a position away from the hydraulic lash adjuster bore; a connection oil passage which connects the hydraulic lash adjuster bore and the main oil passage; and a side wall that defines a radially outer portion of the hydraulic lash adjuster bore. The side wall includes a first side wall portion and a second side wall portion that is positioned closer to an opening of the hydraulic lash adjuster bore than the first side wall portion is. A thickness of the second side wall portion is greater than a thickness of the first side wall portion.

Various embodiments of the present disclosure are directed to an internal combustion engine cylinder head. In one example embodiment, the cylinder head includes a combustion chamber, a fire deck, an intermediate deck remote from a combustion chamber, a central receptacle that receives an injection or ignition device, at least one valve bridge, at least two adjacent gas exchange valves, a top-down cooling system, at least one first transfer opening, and at least one second transfer opening. The top-down cooling system including a first sub-cooling chamber and a second sub-cooling chamber. The at least one first transfer opening positioned between the first sub-cooling chamber and the second sub-cooling chamber. The at least one second transfer opening positioned between the first sub-cooling chamber and the second sub-cooling chamber is arranged in the region in the region of the at least one valve bridge between the at least two adjacent gas exchange valves.