| 摘要 |
PROBLEM TO BE SOLVED: To provide lightening structure of a poppet valve for easily performing boring work when boring a hole in a stem in a hollow shape, by reducing weight of a valve element part, without reducing rigidity of a joining part of the stem and a valve element. SOLUTION: This lightening structure is constituted by integrally arranging the valve element of arranging a conical valve surface seated on a valve seat and the tubular stem extending in the apex direction of the valve surface from a central part of its valve element. A lightening hole communicating with the stem is arranged in a central part of a combustion chamber surface of the valve element. Its lightening hole is constituted of a relatively large diameter first hole opening on the combustion chamber side and a relatively small diameter second hole extending inside the stem from a central part of its first hole. COPYRIGHT: (C)2009,JPO&INPIT
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