| 摘要 |
PROBLEM TO BE SOLVED: To prevent the contact area of an annular protrusion with a piston rod from being enlarged by the large flexural deformation of the annular protrusion on the inner side in the axial direction of a cylinder caused by the pressure of a high pressure fluid in the cylinder, and eliminate an oil film break on the outer peripheral surface of the piston rod. SOLUTION: A plurality of annular protrusions 19a-19e are formed on the inner peripheral surface of a seal lip 18, along an axial direction. The protruding height h2 of the annular protrusions 19d, 19e positioned on the axially outside of a cylinder 12 is made higher than the protruding height h1 of the annular protrusions 19a-19c positioned on the inside. In the state of the axially inside annular protrusion 19a receiving high pressure in the cylinder 12, the contact surface pressure of the inside annular protrusion 19a and outside annular protrusions 19d, 19e in the axial direction of the cylinder 12 becomes almost equal, and the flexural deformation of the respective annular protrusions 19a-19e is almost the same, so that the contact area is almost uniform. |
