Bearings play a crucial role in mechanical transmission. They not only support the rotating parts of machinery but also effectively reduce the friction coefficient during the transmission process of equipment, ensuring that the center position of the shaft is fixed. This kind of component is called “Bearing” in the West and “shaft-bearing” in Japan, both highlighting its indispensable position in contemporary mechanical equipment. According to the friction characteristics of the moving elements, bearings can be further classified into two major categories: rolling bearings and sliding bearings.
I. History and Development
China is one of the important birthplaces of rolling bearings. In ancient books, the structure of axle bearings has been recorded, which proves China’s profound foundation in bearing technology. In fact, the cultural relics unearthed in Xuejiaya Village, Yongji County, Shanxi Province show that the prototype of the oldest modern rolling bearing structure in China emerged during the Qin Dynasty from 221 BC to 207 BC.
Since the founding of the People’s Republic of China, especially since the reform and opening up in the 1970s, China’s bearing industry has ushered in a new chapter of rapid development. Meanwhile, the development of bearing technology worldwide is also changing with each passing day. At the end of the 17th century, C. Warlow of Britain designed ball bearings and attempted to install them on mail vans for use, while P. of Britain Worth has also obtained the patent for ball bearings. By the end of the 18th century, H.R. Hertz of Germany published a classic paper on the contact stress of ball bearings, laying an important foundation for the development of bearing technology. On this basis, R. Streebeck from Germany and A. Palmgren from Sweden, among others, made outstanding contributions to the design theory and fatigue life calculation of rolling bearings through A large number of experiments. Furthermore, N.P. Petrov of Russia applied Newton’s viscosity law to calculate bearing friction, while O. Of the United Kingdom Renault conducted an in-depth mathematical analysis of Thor’s discovery and derived the Renault equation, thereby laying the foundation for the theory of hydrodynamic lubrication.
Looking back at history, China’s bearing industry has achieved remarkable accomplishments that have attracted worldwide attention over the past 50 years since the founding of the People’s Republic of China, fully demonstrating its competitiveness and influence on the international stage.
Ii. Application and Impact
Rolling bearings play a crucial role in modern machinery. They are widely used in various devices, including automobiles, machine tools, motors, etc., playing a role in supporting rotating shafts or sliding shafts. The excellent performance of rolling bearings makes the operation of mechanical equipment more stable and efficient, thereby improving production efficiency and product quality. Meanwhile, there are various types of rolling bearings, which can meet different application requirements and provide strong support for the diversified development of mechanical equipment. Therefore, rolling bearings play an indispensable role in promoting the development of modern mechanical industry.
Its core function lies in support, that is, bearing the shaft, but this function is not limited to this. Essentially, support means being able to bear radial loads, fixing the shaft so that it can only rotate, while controlling its axial and radial movements. If the motor lacks bearings, it will not work properly because the shaft may move in any direction, and when the motor is working, the shaft is required to only rotate. From a theoretical perspective, bearings cannot fulfill the transmission function, but they will affect the transmission effect. Therefore, good lubrication must be achieved on the bearings of the high-speed shaft to reduce this effect. Some bearings are already lubricated by themselves and are called pre-lubricated bearings, while the majority of bearings need to rely on lubricating oil. When operating at high speed, additional energy consumption will be generated due to friction, which is more likely to cause bearing damage. Therefore, the idea of converting sliding friction into rolling friction is not comprehensive, as there are still devices like sliding bearings.
Iii. Classification of Rolling Bearing Dimensions
(1) Miniature bearings, with a nominal outer diameter dimension less than 26mm;
(2) Small-sized bearings, with nominal outer diameters ranging from 28 to 55mm;
(3) Medium and small-sized bearings, with nominal outer diameters ranging from 60 to 115mm;
(4) Medium and large-sized bearings, with nominal outer diameter dimensions ranging from 120 to 190mm;
(5) Large bearings, with nominal outer diameter dimensions ranging from 200 to 430mm;
(6) Extra-large bearings, with nominal outer diameter dimensions exceeding 440mm up to 2000mm;
(7) Heavy and large-sized bearings with a nominal outer diameter exceeding 2000mm.
In addition, there are also classifications based on the bore diameter. For instance, bearings with a bore diameter less than 10mm are categorized as miniature bearings.
Iv. Classification of Load Directions that Rolling Bearings can Withstand
Rolling bearings can be classified according to the direction of the load they can withstand, specifically including radial bearings, thrust bearings and radial thrust bearings. Radial bearings, also known as radial bearings, mainly bear radial loads. Thrust bearings, or thrust bearings, are specifically designed to withstand axial loads. Radial thrust bearings, also known as radial thrust bearings, can withstand both radial and axial loads simultaneously.
In addition, according to the frictional nature of the bearing’s operation, rolling bearings can be divided into two major categories: sliding friction bearings and rolling friction bearings. Sliding friction bearings usually have the advantages of large load-carrying capacity and stable friction, while rolling friction bearings are widely used in high-speed rotating machinery due to their small friction coefficient and high limiting speed.
Among the specific types of bearings, the nominal contact Angle between the balls and the rings of angular contact bearings ranges from 0° to 90°. They can simultaneously withstand radial and axial loads and are suitable for high-speed operation scenarios. Spherical plain bearings, with their simple structure and ease of installation, are often used in simple housing applications. Linear motion bearings are particularly suitable for applications that require relative linear motion.
In addition, there are deep groove ball bearings, which have a simple structure and are convenient to use and maintain. They are the most widely used type of bearing in the mechanical industry. It can not only withstand radial loads, but also demonstrate the performance of angular contact ball bearings when the radial clearance is increased, capable of withstanding larger axial loads. Meanwhile, its low coefficient of friction, high limiting speed and diverse size range enable it to perform well under various working conditions.In addition, thrust ball bearings are also an important type of rolling bearing. Their rolling elements are spherical and are specially designed to withstand axial loads.
Key Points for Storage
When bearings leave the factory, they are coated with an appropriate amount of anti-rust oil and packaged with special anti-rust paper to ensure their quality is guaranteed even before opening. However, for bearings that are stored for a long time, it is recommended to place them in an environment with a humidity of less than 65% and a temperature maintained at around 20℃, and it is best to store them on shelves about 30cm above the ground. At the same time, it should also be ensured that the storage area is protected from direct sunlight and contact with cold walls.
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Post time: May-16-2025