Answer: there is a thin layer of adhesion film between the oil seal lip and shaft contact surfaces. The existence of this layer of the film, on the one hand, can serve to seal the fluid medium, on the other hand can also play the role of lubrication between the lip and the shaft. Oil seal during use but, due to the role of the oil seal lip and shaft surface and different rotation and fluid sealing in nature, as well as the interactions between and interaction conditions often change, so the oil seal in the dynamic often in the hydrodynamic lubrication, boundary lubrication and dry friction Chung lubrication state alternate coexistence, which is fluid lubrication. Therefore, to ensure that the film thickness in the appropriate range to achieve a good seal.
Skeleton oil seal oil seal, the lubricating oil seal. It is commonly used in a variety of mechanical bearings, particularly to parts of the rolling bearing. Its purpose is the isolation of the oil chamber and the outside world, internally sealed oil, foreign dust. The difference with other lip seal, oil seal is to have a greater resilience of the lip seal contact width is very narrow (about 0.5mm) and contact stress distribution graph showed a cusp-shaped. The typical oil seal lip contact stress diagram. Oil seal cross-section shape and tight coupling spring, so that the lip following compensatory axis. Therefore, the oil seal to the smaller caliber of the lip to force seal fruit. Oil seals and other sealing device has the following advantages: ① The structure is simple, easy to manufacture. The once simple oil seal will be able to molding, even the most complex oil seal manufacturing process is not complicated. Metal skeleton oil seal only after stamping, adhesive bonding, mosaic, molding and other processes can be of metal and rubber to the requirements of the oil seal. ② light weight, less supplies. Each of oil seals are thin-walled metal parts and rubber parts combination, the material cost little, and thus the weight of each oil seal is very light.③ oil seal installation location, the axial dimension is small, easy processing and machine compact. ④ good sealing performance and longer life. Eccentricity on the vibration of the machine spindle has a certain degree of adaptability. ⑤ disassembly easy, easy maintenance. ⑥ the price is cheap. The oil seals the disadvantage is that can not withstand high pressure, we can only make the sealing of the bearing lubricant. Oil seals the scope of work are as follows: working pressure 0.3MPa sealing surface linear velocity low-speed type <4m / s, high-speed type 4 ~ 15m / s Operating Temperature -60 to 150 ° C (with rubber types) applies medium oil, water, and weak corrosive fluid design life of 500 ~ 2000h.