| 摘要 |
PROBLEM TO BE SOLVED: To improve sealing ability while the increase of frictional resistance of a spline groove is suppressed. SOLUTION: A protrusion seal part 12 formed on a lip 10 on the inner circumferential side is formed in an arcuate shape conforming to that of a spline groove 7 having an outer peripheral surface 7a formed in an arcuate shape in a peripheral direction. The curvature of radius of the circular arc is reduced to that of the circular arc of the outer peripheral surface 7a of the spline groove 7. As a result, the slide contact surface 12a of a protrusion seal part 12 is forced into close contact with the outer peripheral surface 7a of the spline groove 7 at approximately the same contact surface pressure as that of the lip 10 on the inner peripheral side at two edges, and forced into a further high contact surface force at a central part. The slide contact surface 11a of the tip part 11 and the slide contact surface 12a of the protrusion seal part 12 is formed in an arcuate shape in the direction of a central axis, and the curvature radius of the circular arc of the slide contact surface 12a of the protrusion seal part 12 is reduced to a value lower than that of the slide contact surface 11a of the tip part 11. |
