Writer: Eric Bearing Limited
Under normal circumstances, the contact angle of the assembled angular contact ball bearings is the same. The following is the allowable external axial load of the preload introduced by Eric Bearing Limited. When the axial load exceeds the rated requirement, some bearings will be unloaded, causing the ball Slippage and cause early bearing failure. In order to avoid unloading phenomenon (that is, increase unloading force), the preload of the bearing set can be increased or NSK bearings with different contact angles can be used for assembly.
In order to meet the bearing capacity and rigidity requirements, NSK angular contact ball bearings can be assembled in a variety of ways during use, and in order to maximize the performance of the bearing after assembly under specific operating conditions, select the appropriate The preload is extremely critical. The correct preload can not only increase rigidity, but also reduce noise, improve shaft guiding accuracy, extend bearing life, improve rotation accuracy, and prevent high-speed applications with fast start/stop, ultra-light load or no-load conditions Slippage occurs.
1. NSK angular contact bearing assembly method
Bearings with different contact angles have the same assembly method as those with the same contact angle. According to the number of assembled bearings, the assembly methods can be divided into double, triple and quadruple, etc.; according to the direction of assembling bearings Different classifications. There are mainly DB, TBT, QBC and DBT types for the assembly of bearings with different contact angles.
2. Preloading method of NSK angular contact bearing
Angular contact ball bearings usually adopt axial preload during use, and the preload methods include positioning preload and constant pressure preload.
(1) Positioning preload
It is through the assembly of the bearing itself or the pre-selected inner and outer ring spacers to keep the distance of the assembled bearing unchanged, so that the bearing can be properly preloaded. Due to the influence of the working state of the NSK bearing and the external environment, the size of the bearing seat and the bearing The components will also change accordingly, which will affect the preload state of NSK bearings. The use of this preload method is beneficial to improve the rigidity of NSK, but it is necessary to pay attention to the influence of the change of preload on the bearing performance. NSK 6418 bearings online , pls click here :
(2) Constant pressure preload
It uses elastic elements such as coil springs and butterfly springs to properly preload the bearing at the supporting position. With constant pressure preloading, the movement of NSK bearings under normal working conditions will not affect the preload, but the bearing stiffness grade is low, so it is suitable for high-speed rotation occasions, but not suitable for high stiffness, load direction changes or possible occurrences In bearing applications where the impact load is uncertain.
3. The influence of external load on the axial displacement of the preloaded bearing group
For the preloaded assembly bearing, the preload is more susceptible to external load.
(1) DB type
After the preload and load displacement of DBs with different contact angles are assembled, under the action of the preload, the inner ring end faces of the two NSK bearings will fit together.
The influence of external axial load on the axial displacement of the preloaded bearing group. Because two NSK bearings have different contact angles, the force and displacement curves of the two NSK bearings are quite different. Under the same axial load, one of the NSK bearings A The amount of deformation is smaller than that of another NSK bearing B. The maximum external load should not exceed 1.73 times of the preload, otherwise the bearing B will be unloaded, leading to premature failure of the bearing.
(2) TBT type
The effect of the external load on the axial displacement of the pre-tightened bearing set of triple TBT grouped bearings. Because one end of the bearing is connected in series with two sets of bearings, under the action of external load, the pre-tightening force and the axial The directional forces are F0/2 and FaA/2 respectively, and the preload force of bearing B is still F0.
(3) QBC and DBT type
For the quadruple bearing, the relationship between the external load and the minimum preload can also be solved by the above method.
4. Unloading force comparison
It can be seen from the above calculation that the maximum external load (unloading force) that can be borne in different directions is different for the several assembly methods in the above example. The unloading force of different contact angle bearing assembly and the same contact angle bearing assembly is also different.
Compared with the assembly of bearings with the same contact angle, the assembly of bearings with different contact angles can increase the bearing capacity of the bearing at the main load end (end A) without unloading.
(1) NSK angular contact ball bearings can not only be assembled with bearings with the same contact angle, but also can be assembled with bearings with different contact angles, and the assembly methods are various.
(2) Compared with the use of assembled bearings with the same contact angle, under the same preload and assembly method, the use of bearings with different contact angles for assembly can increase the carrying capacity of the main load end.
(3) When NSK bearings with different contact angles are used for assembly, the bearing capacity of the non-primary load bearing end of the bearing set is relatively low, and the directionality should be paid attention to during use.