Abstract: A method of manufacturing an engine valve intermediate product with a boss portion formed in integral fashion at an outer circumferential surface at an intermediate location on a stem forming portion. The manufacturing method may comprise a stem retaining operation in which an intermediate location of the stem forming portion is retained by a plurality of intermediate jigs removably installable radially with respect to a center of the stem forming portion, and a base end portion is retained by a base end jig. The manufacturing method may further comprise a stem enlarging operation in which compressive forces are applied from both ends of the intermediate product and the boss portion is formed as the intermediate product is made to rotate and alternating loads that cause tensile forces and compressive forces to act in repeated and alternating fashion at the outer circumferential surface of the stem forming portion are applied.

Abstract: A method of manufacturing an engine valve intermediate product with a boss portion formed in integral fashion at an outer circumferential surface at an intermediate location on a stem forming portion. The manufacturing method may comprise a stem retaining operation in which an intermediate location of the stem forming portion is retained by a plurality of intermediate jigs removably installable radially with respect to a center of the stem forming portion, and a base end portion is retained by a base end jig. The manufacturing method may further comprise a stem enlarging operation in which compressive forces are applied from both ends of the intermediate product and the boss portion is formed as the intermediate product is made to rotate and alternating loads that cause tensile forces and compressive forces to act in repeated and alternating fashion at the outer circumferential surface of the stem forming portion are applied.

Abstract: A hollow poppet valve (10) having an improved heat transfer capability is provided. The valve has an internal cavity (S), extending from within a valve head (14) into a stem (12) of the valve, is loaded with a coolant (19) together with an inert gas. The coolant in the valve head (14) is stirred by swirl flows of the coolant generated during reciprocal motions of the valve. A multiplicity of swirl-forming protrusions are formed on at least on one of the bottom and the ceiling of the valve head cavity (S1) in such a way that swirl flows (F20, F30) of coolant are generated by the protrusions in the valve head cavity (S1) during reciprocal motions of the valve to thereby stir the coolant in the circumferential direction of the cavity (S1).

Abstract: A hollow poppet valve (10) having an improved heat transfer capability is provided. The valve has an internal cavity (S), extending from within a valve head (14) into a stem (12) of the valve, is loaded with a coolant (19) together with an inert gas. The coolant in the valve head (14) is stirred by swirl flows of the coolant generated during reciprocal motions of the valve. A multiplicity of swirl-forming protrusions are formed on at least on one of the bottom and the ceiling of the valve head cavity (S1) in such a way that swirl flows (F20, F30) of coolant are generated by the protrusions in the valve head cavity (S1) during reciprocal motions of the valve to thereby stir the coolant in the circumferential direction of the cavity (S1).