Bearing sealing technology

In order to keep the bearing in good lubricating conditions and normal working environment, give full play to the working performance of the bearing and prolong the service life, the rolling bearing must be properly sealed to prevent the leakage of lubricant and dust, moisture or other contamination. intrusion of things.

Bearing seals can be divided into self-contained seals and external seals. The so-called bearing self-sealing is to manufacture the bearing itself into a device with sealing performance. Such as bearing with dust cover, sealing ring and so on. The sealing takes up little space, is easy to install and disassemble, and has a relatively low cost. The so-called bearing plus sealing performance device is a sealing device with various performances manufactured inside the installation end cover, etc. The following main factors should be considered in the selection of bearing seals: 1. Bearing lubricant and type (grease and lubricating oil); 2. The working environment of the bearing and the size of the space occupied; 3. The advantages of the shaft support structure allow Angular deviation; 4. Circumferential speed of sealing surface; 5. Operating temperature of bearing; 6. Manufacturing cost.

External sealing is divided into two types: non-contact and contact. The descriptions are as follows: 1) Non-contact sealing Non-contact sealing is a seal in which the seal does not contact its relative moving parts and has an appropriate gap. This form of seal produces almost no frictional heat and no wear during operation, and is especially suitable for high-speed and high-temperature applications. Non-contact seals are commonly used in various structural forms such as gap type, labyrinth type and gasket type, which are used in different occasions. The gap of the non-contact seal is preferably as small as possible. 2) Contact seal Contact seal is a seal in which the seal is in contact with its relative moving parts and has no gap. Due to the direct contact between the seal and the mating parts, this kind of seal has a large friction and a large amount of heat during operation, which is easy to cause poor lubrication, and the contact surface is easy to wear, resulting in a decrease in sealing effect and performance. Therefore, it is only suitable for medium and low speed working conditions. Commonly used contact seals include felt seals, leather cup seals and other structural forms, which are used in different occasions. According to the working conditions of the bearing and the requirements of the working environment for the degree of sealing, various sealing forms are often used comprehensively in engineering design to achieve a better sealing effect.

The limit speed of the bearing The limit speed of the bearing is related to many factors such as the type, size, load, lubrication, precision, clearance, cage and cooling conditions of the bearing. However, the most important factor is the allowable operating temperature of the lubricant or bearing material. The limiting speeds of various types of bearings are listed in the bearing dimension and performance table in the 'Rolling Bearing Product Catalog'. They are determined under the conditions of grease lubrication and oil lubrication (including oil bath lubrication) respectively. The scope of application is: (1) Standard (G) class tolerance bearings; (2) radial bearings only bear radial loads; thrust bearings only bear axial loads; (3) Pu003d0.1C, due to the increase of the contact stress between the rolling element and the contact surface of the raceway, the working temperature of the bearing increases, and the performance of the lubricant is relatively deteriorated. Therefore, the limit speed of the bearing increases. will be reduced accordingly. For the range of C/p>u003d10, since the limit speed is reduced very little, it can be ignored, that is, the value is taken as f1u003d1. For radial bearings under combined load, due to the increase in the number of rolling elements under load, the frictional resistance increases, the heat generation increases, the lubrication and cooling conditions become worse, and the force acting on the cage also increases. Therefore, it must be According to the bearing type and the size of the load angle, the limit speed of the bearing is multiplied by a reduction factor f2 to adjust. If the limit speed and rotation speed of the selected bearing cannot meet the requirements of use, some improved technical measures can be used to improve it to achieve more satisfactory requirements. Such as increasing the bearing tolerance level; appropriately increasing the clearance; changing to special materials and improving the structure of the cage; changing the lubrication method, such as using oil and gas, oil mist and jet lubrication; improving cooling conditions, etc.