To efficiently transport heat of a valve umbrella part on a valve stem side to improve a cooling property of an engine valve and thereby to elongate service life of an engine and improve reliability thereof, reduce a manufacturing cost of an engine valve, and facilitate treatment of the used engine valve.
In the engine valve 7A, a hollow part 21A is axially extended in the valve stem 7Aa extended from the valve umbrella part 7Ab, and a heat transport medium 23 is sealed in the hollow part 21A. The heat transport medium 23 is substance, such as low-melting-point alloy made by mixing lead with bismuth at the mixing ratio of 45 wt.% to 55 wt.%, having a heat transport capacity, that is, a heat quantity transported from a bottom face of the valve umbrella part 7Ab to a stem end part of the valve stem 7Aa is 3×1010(J*s0.5)/(K*m4) or more when a certain temperature difference is applied between the bottom face of the valve umbrella part 7Ab and the stem end part of the valve stem 7Aa.
MORII HIROKAZU
YOSHIMURA COMPANY KK
Kunio Ueda
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