| 摘要 |
PROBLEM TO BE SOLVED: To provide a valve cap having an extended service life by suppressing wear and pitching. SOLUTION: The valve cap disposed at the tip part of a valve 54 abutting on a rocker arm 51 is provided with innumerable micro recesses randomly at least at one of a contact part with the valve 54 and a contact part with the rocker arm. A surface roughness parameter Ryni of a surface provided with the recesses is within a range of 0.4μm≤Ryni≤1.0μm, and an Sk value is -1.6 or less. The contact part thereby obtains high oil film forming ability, and a long service life can be obtained even under the condition that oil film thickness is extremely thin under low viscosity and lean lubrication. COPYRIGHT: (C)2007,JPO&INPIT
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