This article focuses on some details that should be paid attention to in actual work of single row angular contact ball bearings, from the acceptance check of bearing quality, to the best installation method, to the maintenance of correct operation, to ensure the service life of the bearing. , contributing to the development of the enterprise.
Keywords: angular contact ball bearings; bearing installation; bearing lubrication; energy saving benefits; selection principles
Classification of bearings
Bearings play a decisive role in modern mechanical equipment and are very important components in mechanical equipment. Its main function is to support the rotating shaft or other moving bodies, guide the rotation or moving motion and bear the load transmitted by the shaft or parts on the shaft.
According to the different friction properties of moving elements, bearings can be divided into two categories: rolling bearings and sliding bearings. According to the load direction it can bear, it can be divided into: ① radial bearings, also called radial bearings, bear radial loads; ② thrust bearings, also called thrust bearings, bear axial loads; ③ radial thrust bearings, Also called radial thrust bearing, it bears both radial load and axial load. What is mainly mentioned here is rolling bearings. According to the different functions, designs and functions of rolling bearings, there are many types of bearings, generally including: needle roller bearings, aligning ball bearings, deep groove ball bearings, spherical roller bearings, thrust bearings Bearings, seated bearings, spherical plain bearings, combined bearings, rolling mill bearings, etc. Different bearings have different functions and play an important role in different mechanical equipment.
In order to better identify and distinguish bearings, experts and scholars have given different types of bearings a name – the bearing code. A complete bearing code consists of a basic code plus one or more supplementary codes. The basic code is used to indicate the type of bearing, the basic design of the bearing, and the overall dimensions of the bearing. Supplementary codes refer to components of the bearing, variations with different structures or other characteristics from the basic design.
Classification of rolling bearings
What are rolling bearings? Simply put, rolling bearings are supports that work on the principle of friction. Due to the lubrication effect of lubricating oil, they have low friction, easy startup, fast rising speed, compact structure, and wide adaptability. For example, it is widely used in various industries such as industry, agriculture, transportation, national defense, aerospace, home appliances, etc., and is closely related to the national economy and people’s livelihood.
Most of the bearings we often encounter in our daily work are rolling bearings. Of course, sliding bearings will also be encountered, but relatively speaking, rolling bearings are widely used in actual work. There are also many types of rolling bearings, as mentioned in the above bearing codes, such as: deep groove ball bearings, angular contact ball bearings, tapered roller bearings, thrust ball bearings, spherical roller bearings, spherical ball bearings, etc., according to their respective The differences in function, design and function all play their respective roles.
Structure of angular contact ball bearings
As we all know, general bearings are composed of four parts: inner ring, outer ring, cage, rolling elements, and some also contain dust disks. Angular contact ball bearings are no exception. Their basic components are inner ring, outer ring, cage and rolling balls. Angular contact ball bearings come in two forms: single row and double row angular contact ball bearings, and their functions are different. But regardless of their different forms, they are all installed in pairs. For some reason, according to the basic design requirements, they are used individually, but it is not common. Here is a brief introduction to single row angular contact ball bearings.
Single row angular contact ball bearings are widely used at present, mainly because they can bear axial load and radial load at the same time, as well as pure axial load. The limit speed is very high, and the size of the axial load is related to the size of the contact angle. Relevantly, the larger the contact angle, the greater the axial load it bears. What is the contact angle? Simply put, it is the angle between the line connecting the contact points of the ball and the raceway on the radial plane and a line perpendicular to the bearing axis. This kind of bearing can be roughly divided into two forms: separable and inseparable. Here I am mainly talking about the single row angular contact ball bearings inseparable 7000 series.
There are problems that should be paid attention to during the actual installation and use of angular contact ball bearings
We know that angular contact ball bearings can be divided into three types according to their contact angle: ① Type 7000C, contact angle а = 15°, mainly used in larger size precision bearings; ② Type 7000AC, contact angle а = 25°, mainly used in For precision spindle bearings; ③7000B type, contact angle а=40°, can withstand large axial loads.
The installation methods of angular contact ball bearings can generally be divided into three main types:
Back-to-back configuration, its suffix code is DB
What is a back-to-back configuration? Simply speaking, it refers to the installation method in which the outer ring of the bearing faces the wide face, or the small end of the inner ring of the bearing faces the small end. This is an installation method that we should often use. Compared with the other two methods, it has the following advantages: ① The load it bears is separated from the bearing shaft, pay attention to the separation; ② It can withstand the effects of Axial loads in 2 directions, but the load in each direction can only be borne by one bearing; ③ It can adapt to bearing configurations with relatively high rigidity and can also withstand overturning moments.
Combining these three advantages, it is not difficult to find that back-to-back installation separates the load toward the bearing shaft. It has the advantage of separating the load for both the bearing and the shaft. In addition, it can withstand overturning moments. If you choose the appropriate Contact angle, you can imagine how much maintenance labor can be saved in actual operation, and how many possible equipment accidents can be avoided? Therefore, based on experience and actual conditions, I recommend the preferred back-to-back configuration. For example, the 14 pumps of the methanol and fine boundary zone distillation unit use angular contact bearings and deep groove ball bearings, and they have been in good condition in the past few years.
Face-to-face configuration, its suffix code is DF
What is meant by face-to-face configuration is the opposite of back-to-back configuration. It refers to the installation method in which the large end of the bearing inner ring faces the large end face, or the narrow face of the bearing outer ring faces the narrow face. This method is also often used, but it does not have the advantage of back-to-back arrangement. The load it bears is concentrated toward the bearing shaft. Moreover, this arrangement is not as rigid as the back-to-back arrangement and is not suitable for withstanding overturning moments.
Series configuration, its suffix code is DT
What is a series configuration? As the name suggests, it means moving in one direction and smoothly. In practice, we rarely use this configuration.
In fact, the installation method of this kind of angular contact ball bearing can be distinguished by the bearing suffix code. Coupled with the correct and reasonable installation method, the hot installation method is generally used. After the bearing is heated to the appropriate temperature by the bearing electric heater, it is carried out immediately. Installation, this can avoid bearing deformation caused by excessive beating of the bearing, or reduction of bearing life due to out-of-synchronization of the inner and outer rings, which affects the long-term production operation. Rolling bearings are precision components and must be assembled and disassembled in a standardized manner, otherwise their accuracy will be reduced and the bearings and other parts may even be damaged. During assembly and disassembly, the rolling elements must be free from external forces, and the assembly and disassembly force must be symmetrical and act evenly on the end face of the seat ring. Two methods are usually available: one is the hot-fitting method, as mentioned above; the other is the cold-pressing method, which is a small bearing with a true interference fit. A special pressing sleeve is used to press-fit the inner and outer rings of the bearing, and the bearing is Press-fit onto shaft or housing. Therefore, we must adopt the correct installation method and cannot be opportunistic or fool ourselves, so as to prevent damage to the bearings caused by the installation quality.
Principles for selecting angular contact ball bearings in practice
①The size, direction, nature and service life of the load are the main basis for selecting the type of bearing;
②The rotation speed has little impact on the selection of bearing type, and it only has a significant impact when the rotation speed is high. One point to emphasize here is that the material and structure of the bearing cage have a great influence on the bearing speed;
③The selection and lubrication method of lubricating oil, whether to use grease, solid lubricant, or lubricating oil. Choosing the appropriate lubrication method can avoid direct contact between the raceway and the rolling element surface, reduce friction and wear, extend service life, and at the same time also It can cool, absorb vibration, prevent rust and reduce noise. The specific lubrication method and lubricant selection can be selected according to the following table. It is generally determined according to the on-site working environment. There is no unified regulation, but good lubrication must be ensured. The quality of lubrication and maintenance is directly related to the service life of the bearings. I know this very well. We must do timely, fixed-point, fixed-quality, quantitative, and fixed-person operations. We must analyze the oil regularly to ensure that the equipment bearings are well lubricated. In this way, both Ensure the continuous production of equipment, as well as the safety of the environment and everyone’s happy life;
④Based on the fit of the bearing installation, taking into account the size, direction and nature of the load, the level of rotation speed, the level of rotation accuracy and the factors of assembly and disassembly, the general selection principle is: when the load direction remains unchanged, the inner ring fits better than the outer ring. The fit should be tighter; when the load is larger, the speed is higher, and there is vibration and impact, the fit should be tighter; when the rotation accuracy of the bearing is required to be higher, a tighter fit should be used; when the bearing must consider axial movement , the fit between the outer ring and the housing hole should be looser.
Conclusion and outlook
How to extend the service life of bearings is a permanent topic. For now, what we can do is as mentioned above. First of all, we must ensure that the acceptance of bearings must be scientific and standardized, listen, touch, check, see, test, and carefully check the bearings. Quality, ensure that there are no problems with the quality of newly arrived bearings; secondly, strengthen the improvement of the installation quality level, have a rigorous attitude, and carefully install the bearings so that the installed bearings can operate for a long period of time; thirdly, daily maintenance is also very important It is important to ensure that the “five fixes” are achieved and the lubrication is good. Under normal circumstances, when the rolling bearing is running, the sound is smooth and the temperature rise is normal. Once the sound is abnormal, or there is abnormal noise, and the temperature rise is high, this is a common situation where the rolling bearing is abnormal. You should always pay attention to the sound and temperature changes of the bearing. Quickly and accurately determine the bearing failure, so that it can be dealt with in a timely manner, and repairs must be made and repairs must be made. Finally, it is a common phenomenon in China that the bearing service life cycle is not well implemented. It is only when the bearing is abnormal. It is wrong to start replacing. After all, everything has its inherent service life and we cannot violate it.
In short, the correct use and maintenance of bearings during use will have positive significance in ensuring the operating status of the bearings and reducing the failure of mechanical equipment.
