The skeleton oil seal is relatively simple and generally consists of three parts: the oil seal body, the reinforced skeleton and the self-tightening coil spring. The sealing body is divided into the bottom, waist, cutting edge and sealing lip according to different parts. Usually, in the free state of the skeleton oil seal, its inner diameter is smaller than the shaft diameter, that is, it has a certain "interference quantity".
Therefore, when the oil seal is loaded into the oil seal seat and shaft, the pressure of the oil seal edge and the contraction force of the self-tightening spiral spring produce a certain radial tightening force on the shaft, and after a period of running, the pressure will rapidly reduce or even disappear, so that the spring can compensate the self-tightening force of the oil seal at any time.
Sealing principle:
Because there is an oil film controlled by the edge of the oil seal between the oil seal and the shaft, the oil film has fluid lubrication characteristics. Under the action of the liquid surface tension, the stiffness of the oil film just makes the oil film and the air contact end form a crescent surface, preventing the leakage of the working medium, so as to achieve the sealing of the rotating shaft. The sealing ability of the oil seal depends on the thickness of the oil film on the sealing surface. If the thickness is too large, the oil seal will leak. If the thickness is too small, dry friction may occur, causing oil seal and shaft wear; There is no oil film between the seal lip and the shaft, which is easy to cause heat and wear.
Therefore, in the installation, it is necessary to apply some oil on the sealing ring, while ensuring that the skeleton oil seal is perpendicular to the axis line, if not vertical, the sealing lip of the oil seal will drain the lubricating oil from the shaft, which will also lead to excessive wear of the sealing lip.
During operation, the lubricant in the shell exudes a little to achieve the ideal state of forming an oil film at the sealing surface.