| 摘要 |
PROBLEM TO BE SOLVED: To provide an oil seal that can suppress reduction in fluid suction performance by screw threads as much as possible even if sliding wear of a seal lip progresses.SOLUTION: The oil seal includes screw threads for functioning as a pumping action on an inclined surface at an atmospheric air side of a seal lip that is slidably in close contact with a circumferential surface of a shaft. The screw threads has a two-step structure comprising a combination of: a protruding base formed on the inclined surface at the atmospheric air side; and a screw formed on the base. The base is formed in such a shape that dimensions of height and width increase toward the atmospheric air side. A gentle slope and a steep slope are formed on a front side and on a rear side, respectively, with respect to the shaft rotation direction of the base. The oil seal is formed to satisfy the relationship of A/2<B and A/2>C wherein an apex angle of the screw is A, an angle of the gentle slope with respect to a screw center line is B, and an angle of the steep slope with respect to the screw center line is C. |
