The introduction of hydraulic seal (oil seal)

Hydraulic seal are used to protect shafts and bearings from ingress of dirt and foreign matter and egress of oil or grease. A hydraulic seal generally consists of an outer circular metal part and an inner flexible member that does the actual sealing and is bonded to the metal part by chemical adhesive agents.

A hydraulic seal is a relatively soft, non-metallic ring, captured in a groove or fixed in a combination of rings, forming a seal assembly, to block or separate fluid in reciprocating motion applications. Hydraulic seals are vital in machinery. Preventing oil leakage in the bearing housing is the most basic function of the oil seal. In addition, a good oil seal should also prevent external pollutants (dust, water vapor) from entering and reduce bearing wear. Therefore, the oil seal is also called a bearing protector.

There is a thin layer of adhesive film between the oil seal lip and the shaft contact surface. The presence of this oil film, on the one hand, acts to seal the fluid medium and on the other hand acts as a lubricant between the lip and the shaft. However, during the use of the oil seal, due to the action of the oil seal lip, the difference between the shaft surface and the rotation condition and the fluid seal property, and the interaction and mutual cooperation conditions of the three are often changed, the oil seal is often in the dynamic state. Fluid lubrication, boundary lubrication and dry friction 3 secondary lubrication states alternately coexist, mainly fluid lubrication. Therefore, it is possible to achieve a good seal by ensuring the thickness of the oil film in a suitable range.

The skeleton oil seal oil seal, that is, the seal of the lubricating oil. It is commonly used in bearings of various machinery, especially in rolling bearing parts. Its function is to isolate the oil chamber from the outside world and seal the oil inside to prevent dust. The oil seal differs from other lip seals in that it has a lip with a greater resilience, the seal contact surface is narrow (about 0.5 mm) and the contact stress distribution pattern is sharp. Typical structure of oil seal and schematic diagram of lip contact stress. The cross-sectional shape of the oil seal and the tightening spring make the lip have a good follow-up compensation to the shaft. Therefore, the oil seal can obtain a better sealing fruit with a smaller lip radial force. The oil seal has the following advantages compared with other sealing devices:

①The structure is simple and easy to manufacture. Simple oil seals can be molded at one time, and even the most complex oil seals are not complicated. The metal skeleton oil seal can also form the oil seal required by metal and rubber only by stamping, gluing, inlaying, molding and the like. ②light weight, less consumables. Each oil seal is a combination of thin-walled metal parts and rubber parts, and the material consumption is extremely small, so each oil seal is light in weight.

③The oil seal is installed in a small position, has a small axial dimension, is easy to process, and makes the machine compact. ④good sealing performance and long service life. It has certain adaptability to the vibration of the machine and the eccentricity of the spindle. ⑤easy to disassemble and easy to repair .⑥It is cheap. The disadvantage of the oil seal is that it cannot withstand high pressure, so it can only be used as a seal for bearing oil. The working range of the oil seal is as follows: working pressure ~0.3MPa sealing surface speed low speed type <4m / s, high speed type 4 ~ 15m / s working temperature -60 ~ 150 °C (related to rubber type) for medium oil, water and weak corrosion The design life of the liquid is 500-2000h.