October 7, 2023
Knowledge of skeleton oil seals (1)
1. Structure
The skeleton oil seal structure consists of three parts: oil seal body, reinforced skeleton and self-tightening coil spring. The sealing body is divided into bottom, waist, cutting edge and sealing lip according to different parts. Generally, the skeleton oil seal in the free state has a smaller inner diameter than the shaft diameter, that is, it has a certain "interference amount".
Therefore, when the oil is encapsulated into the oil seal seat and the shaft, the pressure of the oil seal cutting edge and the contraction force of the self-tightening coil spring produce a certain radial tightening force on the shaft, and after a period of operation, the pressure will quickly decrease or even disappear, therefore, the spring can compensate for the self-tightening force of the oil seal at any time.
2. Sealing principle
Due to the existence of an oil film controlled by the oil seal cutting edge between the oil seal and the shaft, this oil film has fluid lubrication characteristics. Under the action of the surface tension of the liquid, the stiffness of the oil film just makes the contact end of the oil film and the air form a crescent surface, which prevents the leakage of the working medium, so as to realize the sealing of the rotating shaft. The sealing capacity of the oil seal depends on the thickness of the oil film on the sealing surface, the thickness is too large, and the oil seal leaks; If the thickness is too small, dry friction may occur, causing oil seal and shaft wear; There is no oil film between the sealing lip and the shaft, which is easy to cause heat and wear.
Therefore, during installation, some oil must be applied to the sealing ring, and at the same time ensure that the skeleton oil seal is perpendicular to the shaft line, if not vertical, the sealing lip of the oil seal will drain the lubricating oil from the shaft, and will also cause excessive wear of the sealing lip. During operation, the lubricant in the housing exudes slightly to achieve the optimal formation of an oil film at the sealing surface.
