| 摘要 |
PURPOSE:To reduce wear of a main lip and to improve durability thereof by relaxing such a phenomenon that a main lip, slides on an inside member while shifting in the central axial direction of an inside member in compliance with pressure fluctuation on the other a side, by making a middle chamber divisible by means of the inside member, a reinforcing metallic part, the main lip, and a negative-pressure lip. CONSTITUTION:When a positive pressure acts on the other side B of an oil seal 16, a negative-pressure lip 9 is easily deformed so as to and lead the pressure to a middle chamber 14, and consequently, a main lip 2 makes elastically strong sliding contact with a rotary shaft 4 and prevents liquid from leaking to one side A. When a negative pressure acts on the other side B, the negative-pressure lip 9 strongly touches the rotary shaft 4 and pressure in the middle chamber 14 comes such one between the atmospheric pressure on one side A and the negative pressure on the other side B; thus the main lip 2 and the negative-pressure lip 9 keep their multual balance. As a result, the main lip 2 comes in sliding contact with the shaft on almost the same circumference at all times. Besides, a very small amount of air, which invades into the middle chamber 14 when the negative pressure acts on the other side B, is prevented from flowing to the other side B by the negative-pressure lip 9; so that, a satisfactory sealing action can be obtained. |
