Rolling bearing type selection-02

Alignment performance of the bearing: When the center line of the shaft is different from the center line of the bearing seat, there is an angular error, or because the distance between the two bearings of the shaft is large and the rigidity of the shaft is small, and it is easy to bend or tilt under force, you can choose a bearing with Self-aligning ball or spherical roller bearings with good self-aligning properties, as well as outer ball bearings. This type of bearing can maintain normal operation even when the shaft is slightly tilted or bent. The quality of the bearing's alignment performance is related to its allowable misaxiality. The larger the misalignment value, the better the alignment performance.

Bearing rigidity: Bearing rigidity refers to the amount of force required to produce unit deformation of the bearing. The elastic deformation of rolling bearings is very small and does not need to be considered in most machinery. However, in some machinery, such as machine tool spindles, bearing rigidity is an important factor, and cylindrical and tapered roller bearings should generally be used. Because when these two types of bearings are loaded, their rolling elements and raceways are in point contact and have poor rigidity. In addition, various types of bearings can also be preloaded to increase support rigidity. For example, angular contact ball bearings and tapered roller bearings, in order to prevent shaft vibration and increase support rigidity, a certain axial force is often applied in advance during installation to press them against each other. It is particularly pointed out here that the preload amount cannot be too large. If it is too large, the friction of the bearing will increase, the temperature rise will increase, and the service life of the bearing will be affected.

Bearing speed: Each bearing model has its own limit speed, which is determined by physical characteristics such as size, type and structure. The limit speed refers to the maximum operating speed of the bearing (usually r∕min), which exceeds This limit will cause the bearing temperature to rise, the lubricant to dry up, and even the bearing to seize. Multiplying the pitch circle diameter D by the shaft rotation speed (unit r/min) gives a limit speed factor (DN). DN is very important when selecting bearing type and size. The product catalogs of most bearing manufacturers provide the limiting speed value of their products. Practice has proved that it is better to work at a speed lower than 90% of the limiting speed.

Influence of lubrication method: The limit speed of grease-lubricated bearings is lower than that of oil-lubricated bearings. The oil supply method of the bearing has an impact on the achievable limit speed. It must be noted that for grease-lubricated bearings, the limit speed is generally only 80% of the limit speed when the bearing uses a high-quality recirculating oil system, but for oil mist lubrication systems, the limit speed is generally higher than the same basic lubrication system. 50% higher.

The design and structure of the cage also affect the limiting speed of the bearing, because the rolling elements are in sliding contact with the surface of the cage. Using a more expensive, reasonably designed cage made of high-quality and low-friction materials can not only reduce the rolling Separate the body and help maintain a lubricant film in the sliding contact area. But cheap cages, such as stamped cages, usually only keep the rolling elements separated. As a result, they suffer from accident-prone and distressing sliding contact, resulting in a lower limit speed.