| 摘要 |
PURPOSE:To obtain a light-weight poppet valve at low cost for use in the intake and the exhaust systems and the like of an internal combustion engine by forming a recessed part through cutting out the external surface of a valve spindle within a predetermined lengthwise area. CONSTITUTION:An engine valve 21 has a valve spindle part 21a and a valve head part 21b and is inserted in a valve guide 2. In this case, a recessed part 22 is formed on the valve spindle 21a within a lengthwise area in slidable contact with the valve guide 2. The outer diameter 'd' of an area where the recessed part 22 is provided, is decided from a correlation between the strength of the valve 21 and the weight reduction thereof. Also, the valve 21 is first molded in a hot forging process in manufacture and the external surface thereof is machined. The machining of the recessed area 22 is concurrently carried out with grinding after the machining of the valve 21. According to the aforesaid manufacture method, the engine valve 21 of light weight can be obtained at low cost without any machining facilities.
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