| 摘要 |
PROBLEM TO BE SOLVED: To facilitate the setting of the lower limit value of engine oil ullage from a seal lip part of a valve stem seal and suppress the upper limit value of the ullage, and as a result reduce the dispersion width of the ullage and improve durability. SOLUTION: In a valve stem seal having a fluororesin film 8 at the inner peripheral sliding face of a seal lip part 6, the fluororesin film 8 contains 3-30 wt.pts. of graphite grain, soft grain of 20-100μm in average grain diameter, to 100 wt.pts. of fluororesin. |
