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SKF Deep Groove Ball Bearing Seal Structure

Source:  skf bearing  Time:  2020-09-03

    SKF 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 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 include the following five forms. The first to fourth sealing structures use rubber seals, and the fifth type uses dust caps.


1. Sealing groove contact type sealing structure:


    The inner ring of SKF 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, since 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.

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2. Inner and outer diameter contact sealing structure:


    The difference from the first groove contact sealing structure is that the inner ring of the bearing does not have a sealing groove, and the sealing route is short, which is not conducive to sealing. But the advantage is that the outer diameter of the inner ring of SKF bearings can be grinded to greatly improve the dimensional processing accuracy and reduce the roughness, and this sealing structure is sealed by contacting the lip of the sealing ring with the outer diameter of the inner ring. Generally, it is not Affected by the axial positioning of the sealing ring, it has nothing to do with the machining accuracy of the axial dimension of the sealing groove of the outer ring of the 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 friction torque of the bearing under the same sealing effect is smaller than that of the groove contact seal structure in Figure 1.


3. Double lip seal structure:


    This sealing method has both the sealing advantages of the first structure and the sealing advantages of the second structure, so the sealing effect is better. However, due to 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 ensured that the radial direction has a better contact state, and the axial direction allows non-contact state. If you consider the sealing effect of the outer lip of the sealing ring, 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. For example, for precision low-pitched automotive bearings produced by some domestic bearing manufacturers, the sealing groove is ground with a shaped grinding wheel, which greatly improves the processing accuracy of the sealing groove and the accuracy of matching with the sealing ring, so that the sealing performance of the bearing The quality of vibration and noise has been significantly improved.


4. Non-contact rubber sealing structure:


    Compared with the first groove contact sealing structure, the sealing effect is worse, and it is especially not suitable for sealing against oil leakage and waterproofing. However, the advantage is that the processing accuracy requirements for the sealing ring and the sealing groove of the ferrule are not as high as those required by the first structure, so it has a greater advantage in terms of production cost control.


5. Non-contact dust cover sealing structure:


    The difference is that the fourth structure uses a rubber seal, while the fifth structure uses a 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, its fit must be a clearance fit, and 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 fifth non-contact dust cover sealing structure is often worse than that of the fourth structure. However, due to the simple processing of the dust cover and the low gap cost, 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.