A method of preparing an engine valve is provided. The method includes hot forging a heat resistant steel at 1,150 to 1,250° C. to mold a valve, aging the molded valve and hollowed-out processing the aging valve. Additionally, the method includes nitride-heating the hollow valve and grinding a surface of a neck of the nitride-heated valve to remove a nitride layer.

A method for manufacturing an engine poppet valve may comprise a forging operation, a diameter-decreasing operation, and a joining operation. At the forging operation, an intermediate member at which a valve head portion and an intermediate stem portion are made integral by way of a neck portion may be formed. At the diameter-decreasing operation, the intermediate stem portion may be inserted between/among a plurality of diameter-decreasing tools that have stem member compressing surfaces and stem member inlet surfaces formed so as to be progressively distant from the stem member compressing surfaces and toward the tip end and that are arranged at a plurality of circumferentially equipartite locations about a circumference of the intermediate stem portion, application at the intermediate stem portion from a base end portion of compressive forces which are inwardly directed in a radial direction from the compressing surfaces of the respective diameter-decreasing tools which have been made to come in contact with a part of the intermediate stem portion that has been made to rotate while being displaced in relative fashion in a direction along a central axis thereof causing the part of the intermediate stem portion to be decreased in diameter from the base end portion and causing a main body portion of a first stem portion to be formed at the intermediate member and also causing formation by the compressing surfaces of a stepped portion which is continuous with the main body portion, and formation, by an absence of decrease in diameter of a remaining portion at the intermediate stem portion, of a second stem portion which is broader in girth than the main body portion and which is continuous with the neck portion and which is also continuous with the main body portion by way of the stepped portion. At the joining operation, a stem end member having a same outside diameter as the main body portion may be joined to a base end portion of the main body portion.

A method for manufacturing an engine poppet valve may comprise a forging operation, a diameter-decreasing operation, and a joining operation. At the forging operation, an intermediate member at which a valve head portion and an intermediate stem portion are made integral by way of a neck portion may be formed. At the diameter-decreasing operation, the intermediate stem portion may be inserted between/among a plurality of diameter-decreasing tools that have stem member compressing surfaces and stem member inlet surfaces formed so as to be progressively distant from the stem member compressing surfaces and toward the tip end and that are arranged at a plurality of circumferentially equipartite locations about a circumference of the intermediate stem portion, application at the intermediate stem portion from a base end portion of compressive forces which are inwardly directed in a radial direction from the compressing surfaces of the respective diameter-decreasing tools which have been made to come in contact with a part of the intermediate stem portion that has been made to rotate while being displaced in relative fashion in a direction along a central axis thereof causing the part of the intermediate stem portion to be decreased in diameter from the base end portion and causing a main body portion of a first stem portion to be formed at the intermediate member and also causing formation by the compressing surfaces of a stepped portion which is continuous with the main body portion, and formation, by an absence of decrease in diameter of a remaining portion at the intermediate stem portion, of a second stem portion which is broader in girth than the main body portion and which is continuous with the neck portion and which is also continuous with the main body portion by way of the stepped portion. At the joining operation, a stem end member having a same outside diameter as the main body portion may be joined to a base end portion of the main body portion.

An engine valve includes a stem, a head comprising an outer lip surface, a seating surface extending from the outer lip surface toward the stem, and a combustion surface extending from the outer lip surface on the opposite side of the head as compared to the seating surface. The combustion surface includes a first convex arcuate surface spaced away from the outer lip surface, at least partially forming a raised ring, and a first concave arcuate surface spaced away from the outer lip surface, at least partially forming a dimple.

A matrix for shaping a valve preform has a circular through opening and a reduced conical section. The reduced conical section tapers from an outer diameter to a reduced cone inner diameter, the outer diameter being greater than or equal to the initial outer diameter of the valve preform, and the matrix inner diameter being smaller than the initial outer diameter.

An internally cooled valve (2) includes a valve body having a valve head (4) and a valve stem (6). The valve body has at least one cavity (8) in which coolant (10) is situated. The coolant is a nanofluid (12) in which nanoparticles (14) are dispersed in a dispersion medium (16).

Poppet valve for an internal combustion engine including a valve stem and a single circular valve head attached at one end of the valve stem. The valve head has a circular peripheral contour and an arcuate edge without any sharp elements to avoid turbulence and improve flow around the valve to therefore maximize flow velocity. This translates into increased cylinder breathing in the intake cycle and reducing back pressure in the exhaust cycle.

Poppet valve for an internal combustion engine including a valve stem and a single circular valve head attached at one end of the valve stem. The valve head has a circular peripheral contour and an arcuate edge without any sharp elements to avoid turbulence and improve flow around the valve to therefore maximize flow velocity. This translates into increased cylinder breathing in the intake cycle and reducing back pressure in the exhaust cycle.

Poppet valve for an internal combustion engine including a valve stem and a single circular valve head attached at one end of the valve stem. The valve head has a circular peripheral contour and an arcuate edge without any sharp elements to avoid turbulence and improve flow around the valve to therefore maximize flow velocity. This translates into increased cylinder breathing in the intake cycle and reducing back pressure in the exhaust cycle.

Provided is a method for filling a stem-side hollow area of an engine valve with metallic sodium. The method includes injecting melted metallic sodium into a cylinder having a larger diameter than an inner diameter of the hollow area of the engine valve, forming a solidified metallic sodium rod having a substantially uniform structure in the cylinder, inserting the metallic sodium into the hollow area of the engine valve through a nozzle having a small diameter, and sealing the engine valve.