The Sealing Mechanism Principle Of Oil Seal

The sealing mechanism of the oil seal involves two factors. One is the sealing of the cavity, mainly the positioning of the outer edge of the oil seal (static component) in the cavity; the second is the dynamic seal in which the sealing lip contacts the surface of the rotating shaft, which is the key to the oil seal. The most important function.

The outer edge of the oil seal is to ensure the static sealing of the oil seal in the cavity and stable positioning in the hole, and is easy to assemble. Generally, the metal frame is covered with rubber material, which combines the reliable static sealing ability of the rubber elastomer with the support and positioning advantages of the metal frame. The outer edge of the oil seal is designed with chamfers to facilitate assembly. In addition, grooves are designed on the outer edge of the oil seal to increase adhesion and avoid the danger of the oil seal retreating and skewing. It also increases the press fit tolerance, which can improve the reliability of the oil seal’s static sealing. Oil seals whose outer edges are designed with a metal outer frame are suitable for occasions that require particularly strong and precise installation in the cavity. It should be noted that when the inner surface of the oil seal seat hole is rough, sealant should be applied. Sealant can be used at the seal seat. .

The sealing mechanism of the sealing lip contact area of the oil seal is of extremely important significance to the sealing function of the oil seal. It depends on: the design of the sealing lip; the structure of the elastic material; the roughness of the shaft surface, etc. The combined effect of the radial force of the sealing lip, the angle design of the sealing lip, and the distance design between the lip tip and the center of the spring produces a contact pressure with an asymmetric distribution on the shaft surface: the pressure is maximum on the oil side and rises sharply; The air side pressure decays at a small angle. With the interference (the inner diameter of the sealing lip is designed to be slightly smaller than the diameter of the shaft in a free state and without load), this asymmetric distribution of contact pressure is incompatible with the circumferential annular tightening force generated by the rotating shaft. The combined effect results in deformation of the structural properties of the sealing lip contact area. This sealing elastomer deformation structure is formed during the trial operation of the oil seal and plays a decisive role in the sealing performance (therefore, the oil seal requires a running-in period for trial operation). The influence of the helix plus the rotation of the shaft creates a pumping effect towards the oil side due to this deformation.

1. Overview: Oil seals are sealing elements used to seal rotating shafts in mechanical equipment, while the cavity is basically stationary.

2. Oil seal sealing state: There is a static seal between the outer edge of the oil seal and the cavity, while ensuring reliable positioning of the outer edge of the oil seal between the cavities. The sealing state between the oil seal lip and the shaft is dynamic sealing when the shaft rotates and static sealing when the shaft is stationary.

3. Sealing principle: In order to achieve the sealing effect, an oil film must be formed between the shaft and the oil seal lip. Under the action of the liquid surface tension and the skeleton oil seal seal lip, an oil film is formed to prevent the leakage of the working medium, thereby preventing the leakage of the working medium. Realize the sealing of the rotating shaft. If the oil film thickness is too large, the oil seal will leak; if the thickness is too small, dry friction may occur, causing wear of the oil seal and shaft; if there is no oil film between the sealing lip and the shaft, it will easily cause heat and wear. The formation of oil film has many influencing factors. For example: the smoothness of the sliding surface, the pressure distribution of the contact part, etc.