The determination of bearing clearance is a very important part in the selection of bearing and its application. Clearance selection is related to bearing selection, and it directly affects the bearing performance and service life. Therefore, this paper is about the determination of bearing clearance in bearing form and combination.
Bearing form clearance
Firstly, let’s talk about the clearance of bearing form. Bearing form clearance refers to the general clearance of the bearing which is determined according to the bearing type and size. This clearance is usually determined according to the relevant regulations of the bearing standard, and the general normal bearing manufacturing process also stipulates the allowable clearance range. Generally speaking, when selecting the bearing clearance, it is necessary to consider the working temperature, working speed and load direction and magnitude of the bearing, etc. When selecting the appropriate clearance of bearing type, the regular clearance range should be chosen first. If necessary, the clearance value can be reduced or increased based on the corresponding size(Le 2019).
In the case of the increase of working temperature, the clearance of bearing shall be appropriately increased. This is because the increase of temperature will cause the expansion of bearing inner and outer rings, which will lead to the increase of clearance. Generally, when the temperature is higher than 70℃, the bearing clearance should be appropriately increased. In addition, in the case of high-speed operation of bearing, the clearance should be appropriately increased, and the amount of increase should be large when the speed is higher than 11000rpm. When the speed reaches 15000rpm, the clearance should reach the fixed size. And when the speed is higher than 18000rpm, the radial clearance should be increased by 10-30%. Besides, when the bearing is subjected to thrust load, the radial bearing clearance should be increased, while the axial clearance should be reduced. The amount of change should be greater when the load is large, and different materials should be used when the clearance is completely filled.
Bearing fit clearances
Secondly, considering the combination of bearing, the combination clearance is also very important. The combination clearance of bearing refers to the clearance which is obtained by combining the bearings with different tolerances and different inner and outer diameter clearance differences. Its purpose is to meet the requirements of bearing installation and movement accuracy(Oshiro 2019).
In terms of bearing fit, the bearing clearance can be divided into the following three types:
1) Light clearance: It is suitable for the bearings which work in light load and low speed and are allowed to have bigger running resistance. At the same time, it has low manufacturing accuracy and large mutual clearance, and the bearing capacity is small.
2) Tight fit: It has small mutual clearance, low running resistance and large bearing capacity, but it needs to have higher manufacturing accuracy and is suitable for bearings to carry heavy radial and axial load.
3) Interference fit: It has the most stringent manufacturing accuracy, and the fit clearance is negative, which can obtain the better dynamic stability. It is suitable for bearings with low rotation speed and frequent acceleration and braking. Generally, it can be applied to the combination of high-precision and high-speed bearing shaft and bearing.
In addition, when selecting the combination clearance of bearing, the size and weight of the bearing, the working conditions of bearing, the manufacturing accuracy of components, the size and thermal deformation of the parts should be fully considered.
Selection of bearing clearance
Finally, the selection of bearing clearance is an effective measure to improve the performance and service life of bearing, and it also requires careful consideration. Bearing clearance should be selected based on the requirements of bearing structure, size, working temperature and working speed. When user choose the bearing clearance, the following points should be taken into consideration:
1) The radial clearance and axial clearance of bearing should be kept consistent in use;
2) The chosen bearing clearance should be in the range of clearance provisions;
3) Increase the bearing clearance when the working temperature is higher than 70℃;
4) The amount of radial and axial clearance should be considered when the bearing is subjected to a heavy load;
5) When the bearing rotates at a high speed, the radial and axial clearances should be increased accordingly.
In conclusion, bearing clearance selection is an important part of bearing selection and application. To improve the performance and life of bearing, it is necessary to consider the working temperature, working speed, load direction and other factors of bearing in advance, and adopt suitable bearing form and combination clearance to obtain the satisfactory assembly effect and working performance.
References
Le SD (2019). Selection of bearing bearing clearance. Baidu Wenku, 17. https://wenku.baidu.com/view/2f31967e7a14cfd0732ecff1.html
Oshiro H (2019). Consideration points for bearing fit selection. Jisho Souri, 138. https://jisho-suuri.com/bearings-5/fit_5/%E6%80%A7%E5%90%8D%E9%81%B8%E3%81%AE%E3%82%BB%E3%83%BC%E3%83%AB%E9%81%B8%E3%81%AE%E9%81%95%E6%83%85%E3%81%A8%E8%A9%B3%E6%A7
