An internal combustion engine comprising at least a crank case, which houses a cylinder, and a cylinder head, which is adapted to be coupled to the crank case, and a liquid cooling circuit, wherein the liquid cooling circuit comprises at least one inlet aperture and at least one outlet aperture, a lower cooling chamber housed in said cylinder head in a position adjacent to a flame deck of said cylinder head; an upper cooling chamber housed in said cylinder head above said lower chamber, so that said lower chamber is sandwiched between said upper chamber and said flame deck; wherein said inlet aperture is provided in said upper or lower chamber and said outlet aperture is provided in said lower or upper chamber, on a same side of the internal combustion engine, so that the cooling liquid runs in a substantially U-shaped path moving between said upper chamber and said lower chamber, transversely relative to a crankshaft of said engine.

A valve arrangement for an internal combustion engine having at least one intake valve, at least one exhaust valve, and at least one reciprocating piston. Each intake valve is seated in the cylinder head at a lesser distance from the piston than is each exhaust valve. Also, each exhaust valve has a cross sectional area less than seventy percent of the cross sectional area of each intake valve. The cross sectional area of each exhaust valve may be for example sixty to sixty-two percent of the cross sectional area of each intake valve.

A barrier ring for a cylinder assembly for an opposed-piston engine fits into a groove fashioned into a portion of the cylinder liner that is adjacent to the top dead center location of the end surfaces of the pistons, in a volume of the cylinder liner that defines the combustion chamber. The barrier ring and groove are part of a barrier assembly that prevents heat generated during combustion from reaching the outer wall of the cylinder assembly, reducing the need for conventional cooling systems and increasing the amount of heat retained in the combustion chamber. The barrier assembly allows for increased engine efficiency because of the combustion heat retained in the combustion chamber, as well as a reduction in the overall size of the engine because of the reduction in engine cooling needed.

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.

An internal combustion engine includes a hollow cylinder, a piston within the hollow cylinder, and a cylinder head. A base valve assembly at a base of the hollow cylinder permits or restricts fluid flow from an intake manifold into a sub-chamber below the piston. The piston includes at least one intake port connecting a combustion chamber above the piston with the sub-chamber, and a transfer valve that opens and closes the at least one intake port. When the transfer valve opens the at least one intake port, fluid is permitted to flow from the sub-chamber to the combustion chamber. The internal combustion engine operates according to a four-stroke piston cycle, wherein multiple intake stages are provided. The intake stages may include intake of air into the sub-chamber during a compression stroke, transfer of air from the sub-chamber to the combustion chamber during a power stroke, intake of air-fuel mixture into the sub-chamber during an exhaust stroke, and transfer of air-fuel mixture from the sub-chamber to the combustion chamber during an intake stroke.

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.

An engine head assembly includes a valve seat insert having a valve seating surface defining a center axis, and each of an inner peripheral surface and an outer peripheral surface extending circumferentially around the valve seat center axis. The outer peripheral surface includes an upper section interference-fitted with the engine head, and a lower section. A stiffness relief channel is formed by a relief cutout in the valve seat insert, and extends radially between the lower section of the outer peripheral surface and the engine head. The stiffness relief channel permits flexing of the valve seat insert to cushion valve seating to prolong engine valve and valve seat insert service life.

A hydraulic lash adjuster for use in diesel engines including a cylinder head having a first valve, a second valve, and a valve bridge extending between and in contact with both the first valve and the second valve. Where the diesel engine includes a first rocker arm, and where at least one of the first valve and the second valve undergo an oil can valve deflection rate. The hydraulic lash is configured to selectively transmit force between the first rocker arm and the valve bridge, and where the hydraulic lash adjuster is normally in the open configuration, and where the hydraulic lash adjuster changes from the open configuration to a closed configuration at a critical velocity that is greater than the oil can valve deflection rate.

An engine includes a cylinder block, a cylinder head, and a piston. The cylinder head is connected to the cylinder block. The piston is movably connected to the cylinder block. The cylinder block, the cylinder head, and the piston form a combustion chamber. The cylinder head includes an intake valve hole and an exhaust valve hole. An intake valve is disposed at the intake valve hole and an exhaust valve is disposed at the exhaust valve hole. A barrier protrusion is protruded at the edge of the intake valve hole away from the exhaust valve hole. The included angle between a first connecting line connecting a first end of the barrier protrusion and a center of the intake valve hole and a second connecting line connecting a second end of the barrier protrusion and the center of the intake valve hole is greater than 120 degrees and less than or equal to 180 degrees.

An off-road vehicle includes a frame and an engine. The engine includes a cylinder block and a cylinder head, on which an exhaust passage is arranged. The cylinder head is provided with a supplementary air supply passage for mixing air into the exhaust gas discharged from the combustion chamber. Alternatively, the supplementary air supply passage can be included in the exhaust system, such as in a cylinder head mounting flange of the exhaust pipe, upstream of an oxygen sensor and first and second stage catalytic converters. The exhaust gas from the engine is further oxidized by air, which reduces the content of components such as CO and NOx in the exhaust gas, improving environmental protection.