What are the properties of rolling element bearing?

Performance of rolling element bearing
Alignment performance
The ability of the bearing to work normally when the shaft centerline is inclined relative to the centerline of the bearing seat hole. Double row radial spherical ball bearings and double row radial spherical roller bearings have good self-aligning performance. Roller bearings and needle roller bearings are not allowed to have relative inclination of the inner and outer ring axes. Different types of rolling bearings allow different inclination angles, such as 8′～16′ for single row radial ball bearings, 2°～3° for double row radial spherical ball bearings, and ≤2′ for tapered roller bearings.

The limiting speed of rolling element bearing
The maximum speed allowed by the bearing under certain load and lubrication conditions. The limiting speed is related to bearing type, size, accuracy, clearance, cage, load and cooling conditions. The working speed of the bearing should be lower than the limit speed. Selecting high-precision bearings, improving cage structure and materials, using oil mist lubrication, improving cooling conditions, etc., can improve the high limit speed of rolling element bearings.

Lubrication of rolling element bearing
There are mainly grease lubrication and oil lubrication. Grease lubrication is not easy to leak, easy to seal, long service time, easy to maintain and has high oil film strength, but the friction torque is larger than that of oil lubrication, so it is not suitable for high speed. The filling amount of grease in the rolling element bearing should not exceed 1/2 to 1/3 of the bearing space, otherwise the bearing will be overheated due to excessive stirring of lubricant. Oil lubrication has good cooling effect, but the sealing and oil supply devices are more complicated. The viscosity of the oil is generally 0.12 to 0.2 cm/sec.

When the load is large, the oil with high viscosity should be used when the working temperature is high, and the oil with low viscosity should be used when the rotation speed is high. Lubrication methods include oil bath lubrication, drip oil lubrication, oil mist lubrication, oil injection lubrication and pressure oil supply lubrication. During oil bath lubrication, the oil level should not be higher than the center of the lowermost rolling element. If the bearing is designed according to the theory of elastohydrodynamic lubrication and the viscosity of the lubricant is selected, the contact surfaces will be separated by an oil film. At this time, under the action of stable load, the life of rolling element bearing can be increased many times.

Modern machines, instruments and other equipment are developing in terms of high speed, heavy load, precision and lightness. This puts forward many new requirements for rolling bearings. For example, while reducing the size, the rolling element bearing is required to maintain or even increase the rated load, and new technologies are adopted. Improve the process, improve the manufacturing accuracy and reduce the cost. It is difficult for general rolling element bearings to meet various requirements. Special rolling element bearings should be designed and manufactured for machinery and equipment with large production volumes. While strengthening standardization, increase varieties and expand the proportion of special bearings. The development of modern industry also requires special bearings that work under special working conditions, such as rolling element bearings that work in high speed, high temperature, low temperature, strong magnetic field or in acid, alkali and other media.

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