How to calculate the preload of tapered bearing installation

The magnitude of the preload must be calculated, and the calculation must take into account the internal structure of the bearing and related dimensions, including groove curvature, steel ball curvature, material properties, etc. After calculating, it is converted into the torque of the bolt, because the general preload is applied by the bolt, so the preload can be applied by the torque wrench. It should be noted that many occasions in China rely on experience to control the preload, this method is because the consistency ratio of the domestic bearing accuracy is poor, and the second is that the control method of the preload force is not very standardized.

Tapered roller bearings are pure rolling regardless of positive and negative clearance, and their largest heat source is the sliding friction at the large end face of the roller and the large flange of the inner ring, while the different points of the rollers of the spherical roller bearings have sliding friction with the inner and outer ring raceways regardless of the positive and negative clearance. Generally, the reason for the sharp increase in heat during negative clearance is that the preload destroys the lubricating oil film, so that the contact surface of the two metals is directly adhered to. This is not the case with diagonal contact ball bearings, and whether the bearing is pure rolling after assembly depends on the assembly state of the bearing.

If the inner and outer sleeves of a tapered roller bearing are not compressed in the opposite direction sufficiently, it is not in a pure rolling state.

Bearing preload is generally used under high-precision operating conditions. Theoretically speaking, the bearing runs most smoothly in the negative clearance working condition at zero clearance or even a certain extent, and the bearing stiffness is the most effective at this time, and the noise during the bearing operation is also the lowest, therefore, the bearing should be guaranteed to work under this condition as much as possible. However, considering the factors such as the installation and coordination of the bearing, the material deformation caused by the temperature change during operation, the bearing is reserved for positive clearance during processing.

In order to be able to be used under the working conditions of high-precision operation, after the bearing and related components are installed and matched, certain measures are taken to apply preload, and the bearing clearance is adjusted by adjusting the position of the inner and outer rings, so that the clearance value of the bearing is zero or negative when working, so that the smooth operation of the bearing under high-precision operation can be guaranteed.

As for the bearing types to be preloaded, basically all conventional models are covered, and it can be said that all types of bearings used in high-precision applications need to be preloaded. Including: deep groove ball bearings (used in household appliances), angular contact ball bearings (which must be preloaded when used on high-speed machine tool spindles), thrust bearings, tapered roller bearings, cylindrical roller bearings, etc., can be seen preloaded.

It should be noted that the preload also has a degree, and too much preload will also cause the bearing working temperature rise to be too high, which is easy to cause the early failure of the bearing. However, the preload is too small, and the bearing cannot run smoothly when running at high speed.

Therefore, a variable preload adjustment mechanism has also been developed.

Preload is divided into light preload, moderate preload, and heavy preload. When the bearing needs to run at high speed and requires smooth operation, a light preload should be implemented; When the bearing needs to increase the load capacity and stiffness, and the speed is not high, moderate or heavy preload should be implemented. The slight preload is only to reduce the channeling caused by the clearance between the rolling elements and the raceway in the non-contact area of the bearing during the working operation, so it is sufficient to ensure that the bearing clearance is zero or zero upstream clearance; Moderate or severe clearance is minus negative clearance.

This one is more difficult to calculate. In terms of stiffness, the effect of temperature should also be taken into account. So in many cases, it needs to be determined experimentally.

In general use, it is still empirical, and then exothermic expansion predose. There are many things that cannot be calculated mechanically. That's why good assembly fitters are in demand.

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About how to calculate the bearing preload, you can go to the architectural books or physics books, the general physics books will have calculations on this aspect, well, there is no standard for reference, it may just be that each place has a different standard, so for reference, there may not be for the time being.

I don't know what major you are studying, people who study mechanical design know that there are instructions in a textbook called mechanical design, and there are also such instructions on the Internet, and you can understand them all if you search on the Internet.

Each type of bearing must be different.