What factors affect the performance of oil seals?

Skeleton oil seals are a typical example of oil seals, and generally, when people talk about oil seals, they are referring to skeleton oil seals. The function of an oil seal is to isolate the lubricated parts from the output parts in a transmission system, preventing lubricant leakage. The skeleton acts like the reinforcing steel in a concrete structure, providing reinforcement and maintaining the seal's shape and tension. Based on structure, they can be divided into single-lip skeleton oil seals and double-lip skeleton oil seals. The secondary lip of a double-lip skeleton oil seal provides dust protection, preventing external dust and impurities from entering the machine. Based on skeleton type, they can be divided into enclosed skeleton oil seals, exposed skeleton oil seals, and assembly-type oil seals. Based on operating conditions, they can be divided into rotary skeleton oil seals and reciprocating skeleton oil seals.

Different types are distinguished based on their specific characteristics. Today, we will primarily discuss skeleton oil seals. The structure of a skeleton oil seal consists of three parts: the seal body, the reinforcing skeleton, and the self-tightening helical spring. The sealing body is further divided into the bottom, waist, cutting edge, and sealing lip, depending on the location. Under normal conditions, the inner diameter of a skeleton oil seal is smaller than the shaft diameter, meaning it has a certain "interference fit."

Therefore, after the oil seal is installed in the seal housing and on the shaft, the pressure of the oil seal's cutting edge and the compression force of the self-tightening helical spring exert a certain radial tightening force on the shaft. After a period of operation, this pressure will quickly decrease or even disappear. Therefore, adding a spring can compensate for the oil seal's self-tightening force at any time.

Therefore, during installation, it is necessary to apply some oil to the sealing ring and ensure that the skeleton oil seal is perpendicular to the shaft centerline. If it is not perpendicular, the sealing lip of the oil seal will drain the lubricating oil from the shaft, leading to excessive wear of the sealing lip. During operation, a small amount of lubricant seeps out from the housing to form an oil film at the sealing surface.