Writer: Eric Bearing Limited
1. FAG deep groove ball bearing seal structure analysis
FAG deep groove ball bearings have a variety of sealing structures. According to the different sealing materials, they are mainly divided into two types: rubber sealing ring and dust cover (standard iron cover): according to the different sealing arrangements, they can be divided into contact sealing and non-contact Type seal. For sealed deep groove ball bearings such as motorcycles, home appliances motors, luxury ceiling fans, etc., the basic sealing structures commonly used at present mainly have the following five forms.
(1) Groove contact type sealing structure
The inner ring of FAG bearing has a sealing groove. The sealing ring and the sealing groove form a labyrinth shape. The sealing route is long and has a buffer zone, which is conducive to sealing, especially suitable for sealing solid particles such as dust. However, due to the difficulty of processing and production cost, the sealing groove of the bearing ring is generally no longer processed after turning and heat treatment. Therefore, the processing accuracy of the sealing groove of the bearing ring is limited, resulting in the sealing ring lip and the sealing groove The matching accuracy of the seal ring is not high: Moreover, because the angle between the oblique line of the inner ring seal groove and the vertical line that contacts the seal ring lip is generally only a few degrees, the tightness of the seal ring lip and the seal groove is affected by the inner and outer sides. The axial size of the ring seal groove (the axial position of the seal groove) has a great influence. The axial size of the seal groove of the outer ring changes, and the axial positioning position of the bearing seal ring also changes; or the change of the axial size of the oblique line of the inner ring seal groove in contact with the seal ring lip will directly affect the seal ring and the inner ring seal groove The matching accuracy. Therefore, the sealing ring lip of this structure has a large interference fit with the inner ring seal groove, and the sealing ring lip either has too little contact deformation, which affects the sealing effect, or the contact deformation is too large, increasing the contact surface The frictional torque and bearing rotating torque cause the vibration and noise of the bearing to increase and the temperature rise is too high and too fast. FAG 6010-2RSR bearings online , pls click here :
(2) Inner and outer diameter contact sealing structure
The difference with the groove contact seal structure is that the inner ring of the bearing does not have a seal groove, and the sealing route is shorter, which is not conducive to sealing. But the advantage is that the outer diameter of the inner ring can be grinded to greatly improve the dimensional processing accuracy and reduce the roughness, and this sealing structure is sealed by contacting the outer diameter of the inner ring with the lip of the sealing ring, and is not normally sealed The influence of the axial positioning of the ring has nothing to do with the machining accuracy of the axial dimension of the seal groove of the outer ring of the FAG bearing. Therefore, the matching accuracy between the sealing ring lip and the outer diameter of the inner ring is high, and the interference dispersion is small, which is beneficial to the improvement of the sealing performance. At the same time, due to the better roughness of the outer diameter grinding of the inner ring, the bearing has a smaller friction torque than the groove contact seal structure under the same sealing effect.
(3) Double lip seal
It not only has the sealing advantages of the groove contact type sealing structure, but also has the sealing advantages of the inner and outer diameter contact type sealing structure, so the sealing effect is better. However, due to the limitations of current processing conditions and production costs, it is difficult for both lips to achieve an ideal contact and sealing state at the same time. Therefore, it is generally to ensure that the radial direction has a better contact state, and the axial direction allows non-contact state. If the sealing effect of the outer lip of the sealing ring is considered, it can also be called a three-lip or multi-lip seal. Since this structure requires high processing precision of the sealing ring and the sealing groove of the ferrule, and high production cost, it has not been widely adopted. With the continuous development of sealing ring and ferrule processing technology and the continuous improvement of processing quality, the multi-lip seal structure will be the development direction of bearing high sealing performance.
(4) Non-contact rubber sealing structure
Compared with the groove contact sealing structure, the sealing effect is worse, and it is not suitable for the sealing of oil leakage and water resistance. However, its advantage is that the processing accuracy requirements for the sealing ring and the sealing groove of the ferrule are not as high as the requirements for the groove contact type sealing structure, so it has a greater advantage in terms of production cost control.
(5) Non-contact dust cover sealing structure
The non-contact dust cover sealing structure and the groove contact type sealing structure belong to the same non-contact sealing structure. The difference is that the groove contact type sealing structure uses a rubber sealing ring, and the non-contact dust cover sealing structure uses a non-contact sealing structure. Dust cover. For non-contact sealing structure, the smaller the matching gap between the sealing ring or dust cover and the sealing groove, the better the sealing effect. Due to the excellent elasticity of the rubber sealing ring, even the non-contact structure often allows ultra-light contact; while the dust cover is an iron cover, which does not have the above advantages. The fit must be a clearance fit. The design is to ensure the dust cover The clearance fit with the sealing groove has to reserve a larger clearance. Therefore, the sealing performance of the non-contact dust cover sealing structure is often worse than that of the groove contact sealing structure. However, due to the simple processing of the dust cover and the low cost of the gap, the cost is about 70% of the nitrile rubber seal, so it is often used in some occasions where the sealing requirements are not high.
2. Application of seal structure of deep groove ball bearing
At present, the groove contact type sealing structure deep groove ball bearings used in motorcycles, home appliances motors and luxury ceiling fans industries are usually designed with different sealing structures according to the installation position or working conditions of the bearing.
For example, a single-sided sealed motorcycle engine case bearing is lubricated by splash lubrication by the engine oil in the engine when the engine is working. This splash lubrication method not only forms a certain oil pressure in the engine cavity and the bearing cavity, but also has a certain flow speed of the oil, which is not conducive to the anti-leakage seal of the bearing. Therefore, the requirements for the anti-leakage sealing performance of this type of bearing are very high, and the bearing must adopt a contact seal structure.
Comparing the groove contact sealing structure and the inner and outer diameter contact sealing structure, the inner and outer diameter contact sealing structure has the following four advantages:
(1) The inner ring has no sealing groove, so the processing cost is lower;
(2) The dispersion of the interference between the seal ring lip and the ground inner and outer diameter is small;
(3) The friction torque is smaller under the same sealing effect;
(4) Under the same frictional torque and the same oil pressure on the inside of the sealing ring, the sealing ring lip and the contact surface of the inner ring are not easily separated. This is very advantageous for the sealing under pressure on the inside of the FAG bearing sealing ring.
Therefore, it is more common for motorcycle engine box bearings to adopt inner and outer diameter contact sealing structures. The fit interference mentioned here is a key technical parameter that not only affects the anti-leakage and sealing performance of the bearing, but also affects the friction torque.
Industrial sewing machine bearings are also lubricated with grease, and there are no special requirements for oil and water resistance. However, due to the problem of more dust in the installation environment of the bearing and the use environment of the sewing machine, the dustproof and sealing performance of the bearing is relatively high. Equipped with a labyrinth seal structure with a long sealing circuit, such as a groove contact seal structure
Or non-contact rubber sealing structure.
Luxury ceiling fan motor bearings are the ones with the lowest requirements for sealing performance among the above-mentioned types of bearings. Because the luxury ceiling fans are installed in the home, the working environment is better, and the requirements for dust and water resistance are not high; at the same time, due to the low speed, it is normal The work is generally only a few hundred revolutions per minute, and the centrifugal force on the grease is very small, which is not easy to cause grease leakage. Therefore, the non-contact dust cover sealing structure with the lowest production cost is generally adopted.