Bearings are the core basic components of railway vehicles, which can show the technical core level of a country's machinery manufacturing industry. They have the characteristics of high indicators and difficult technology in bearing production. Therefore, high-end bearings need to reflect their technological innovation and research and development in application. . With the vigorous development of railway transportation, my country's requirements for bearings are getting higher and higher. They need to have the characteristics of high-precision operation, high bearing capacity, high reliability, low vibration and low noise, and are better used in railway vehicles. . At this stage, my country's railway operation has the longest mileage, the highest speed and the largest scale. my country's railway vehicles have also determined the direction of high speed and green environmental protection. Therefore, higher requirements are also put forward for their running devices and drive systems, and the rolling bearings must be guaranteed. The stability of the system provides a prerequisite for the safety and reliability of the overall system. In the process of vehicle operation, bearings need to face high-speed and frequent vibration, temperature rise and lubrication problems, and use optimized bearing manufacturing, scientific assembly methods and testing to solve related impact problems, and finally achieve high-quality bearings. operate.

1 Main technical data and technical requirements of railway vehicle bearings

In terms of bearing structure and external dimensions, the axlebox bearings of my country's railway freight vehicles are constructed using double-row tapered roller bearings. The basic structure is shown in Figure 1.

In railway freight cars, axleless double-row tapered roller bearing units are generally used for connection, and the bearing saddle and the bogie side frame are directly connected. Among the shaftless double-row tapered roller bearing units, due to their relatively light structure and relatively convenient assembly and maintenance, they have been widely used in railway freight cars. There are different concepts for the design of the bearing unit, but the bearing unit is universal. For trains with the same axle load, it is necessary to ensure the interchangeability of the product itself on the basis of the corresponding standard. Therefore, the internal and external nominal dimensions of the bearing are basically the same, and the difference between the internal structural parameters is not large. The biggest difference is mainly reflected in the sealing device. among. The manufacturers of each bearing use the modification of the sealing device to improve the sealing performance of the bearing, so as to realize the reduction of the axial width of the bearing unit, so that the bearing structure is in a reasonable state. Figure 2 shows the bearings of various bearing companies. Structure diagram.

During the life of the bearing, if the maximum running speed of the vehicle is within 200 kilometers per hour, the warranty period of the bearing is 900,000 kilometers or 4 years. There is a problem, but it needs to be scrapped when the operating mileage reaches 2.8 million kilometers or the service life reaches 10 years. If the running speed of the train is above 200 kilometers per hour, it is maintenance-free within 10,000 kilometers, and it needs to be scrapped after 2.4 million kilometers after maintenance. The maintenance period of Japan's high-speed rail bearings is 1.2 million kilometers, and it needs to be scrapped at 3 million kilometers or 6 to 7 years.

2 Optimal application and analysis of railway vehicle bearings

In the optimization application and analysis of railway vehicle bearings, it is necessary to analyze and optimize from multiple angles and aspects. In this paper, the analysis and research are mainly carried out from the aspects of design, assembly and inspection.

2.1 Design optimization

Although my country's railway vehicle technology is gradually moving towards the international market, the core component bearings in railway vehicles still rely on imports, so my country's bearing manufacturing technology needs to be continuously enhanced. Comparing the bearings made in my country and foreign countries, under the condition that the structural parameters are consistent, the vibration amplitude and noise generated by the products in our country during the operation are relatively large, and there are certain differences with the products in foreign countries. The main reason is many factors such as the manufacturing process and condition of the bearing. In the manufacturing process of high-end bearings, high-performance materials and high-quality processing technology are two key core fundamental issues. In my country's iron and steel enterprises, the main difficulty is to extract high-purity and high-uniformity bearing steel, and it is necessary to control the oxygen content in the steel to a minimum level. Among the working conditions, the most important problem is to minimize the vibration and noise caused by the manufacturing factors. Among the factors affecting the life of bearings in the past, the rationality and stability of the processing technology are important factors, and the failure factors of the bearing are also directly related to the heat treatment and grinding process of the bearing.

In terms of the vibration of the bearing, due to the influence of the machining factors of the cage and the roller, the vibration amplitude will be different. The machining quality of the roller has the greatest influence on the bearing, and the roughness of the roller , waviness, surface defects and bumps and other issues will affect the bearing. In terms of modeling and refinement of process flow, it is necessary to use strict and scientific manufacturing standards to achieve scientific analysis of working conditions under different applications, and to analyze the overall and microstructure of roller bearings, and finally achieve optimization. The generated friction torque is effectively reduced, so as to effectively improve the running performance of the roller bearing at high speed. At the same time, among the bearing speed, load, temperature, clearance, viscosity and other lubricating factors are also among the key factors, which need to be quantitatively analyzed to achieve effective optimization of structural parameters, and finally achieve the optimal design state .

2.2 Assembly of bearings

In the assembly process of the bearing, it is necessary to maintain the correct and scientific use of the assembly method to achieve the desired effect. During the operation, there are many aspects that have a great impact on the bearing. Among them, the biggest damage to the bearing operation is vibration, and many problems such as rust, peeling, indentation, cracks, and wear will also cause damage to the bearing. . Under the action of vibration, wear occurs at the mating positions of the inner and outer rings, so that the track is offset in the state of mutual cooperation, or the bearing is fatigued. In terms of the factors affecting temperature, the bearing is in an abnormal state when it is in a high temperature state, and the lubricant in the bearing will be adversely affected under the high temperature state. If the high temperature state is maintained for a long time, the life of the bearing will be affected. There are various factors that cause high bearing temperature, such as insufficient lubrication, excessive lubrication, impurities in the lubricant, excessive load, bearing damage, insufficient clearance or high friction in the state of oil seal.

While optimizing the bearing design and manufacturing conditions, it is also necessary to strictly test the assembly of roller bearings in high-speed railway vehicles. For the assembly environment, size, selection and testing standards and other factors Analysis to minimize bearing wear due to improper assembly can ultimately ensure high-precision operation of the bearing.

First of all, you need to pay attention to the following aspects before assembly. The bearing needs to be kept clean to reduce the impact of dust on the operation of the bearing. The invisible dust may cause early wear or peeling of the bearing. Therefore, it is necessary to maintain a clean environment throughout the assembly process. The assembly site, workbench, tools and equipment used, axles, bearing boxes and other parts need to be kept as clean as the bearing. Try not to open the package with rust inhibitor before the bearing is used.

Secondly, before assembly, anti-rust work is also an essential link. If the bearing is rusted, it will produce hard particles, so the bearing will be worn like abrasives during the use of the bearing. Among the causes of bearing rust, there are many factors such as moisture, oxygen, and salt. Among them, sweat on human hands and moisture in lubricants can cause bearings to rust. Therefore, in the process of component assembly, the operator needs to Wear clean gloves to prevent bearing rust problems. If the bearing assembly operation is carried out by hand, it is necessary to keep the hands clean, and use high-quality mineral oil to smear, and then carry out the operation. Moisture and oxygen in the air may also cause the bearing to rust, so for the preservation of the bearing, it needs to be placed in a dry place.

Finally, in the process of bearing assembly operation, it is necessary to pay attention to the phenomenon of vibration and impact, so as to avoid the bearing damage caused by hitting or falling off to the greatest extent. If the bearing must be tapped, the same force needs to be applied to the end face of the bearing, so that the bearing can be properly slid in and the assembly can be completed. In the process of percussion, try to use a plastic hammer for hammering. If only a steel hammer can be used, a non-iron pad can be placed underneath to disperse the force.

It should be noted that the adjustment and preloading of the clearance in the cage rolling bearing cannot be knocked, which is an important part of the assembly work, which can effectively improve the rotation accuracy and bearing capacity of the bearing. At the same time, The noise caused by vibration in the axle box device can also be effectively reduced, and the fatigue strength of the bearing can be reduced.

Therefore, it is necessary to comprehensively grasp and control the process of clearance adjustment and preloading, and scientifically and rationally apply the technology to ensure the high-quality completion of the bearing assembly work. In the process of assembling the bearing, the clearance needs to be moderate, and it should not be too large or too small. When the clearance is too large, the bearing load of a single rolling element will increase, so the rotation accuracy and service life of the bearing will be reduced, and the operating bearing noise will also decrease when the system vibration increases. will increase. When the clearance is relatively small, the friction force will be increased, which will increase the heat of the bearing, thereby aggravating the wear of the bearing operation, reducing the bearing life, and even causing the rolling element to be stuck. affect normal work. Therefore, it is necessary to strictly adjust and control the clearance in the process of bearing assembly.

In the operation of high-speed vehicles, the load capacity of the bearing is in direct proportion to the requirement for the rotation accuracy, that is, the greater the load capacity, the higher the rotation accuracy. The preloading work is carried out to achieve clearance adjustment and preloading in a state that meets the requirements under the condition of maintaining thermal balance. During the assembly process, it is necessary to use preload to increase the axial force of the inner ring or outer ring of the bearing, so as to make the clearance of the bearing disappear, and realize the initial deformation state of the rolling element and the inner and outer rings under contact. Preload can improve the stiffness and rotational accuracy of the bearing under working conditions. In terms of the actual ideal working clearance of the rolling bearing, it belongs to the clearance that needs to be adjusted under the steady state of bearing temperature rise. Therefore, the adjustment of bearing clearance needs to be divided into two parts. The first step is to adjust the bearing clearance in accordance with the relevant operating specifications and technical requirements under normal temperature, adjust to the appropriate clearance, and use hand rotation to feel flexible rotation. The whole mechanism is loosened to effectively prevent the sudden locking of the bearing due to excessive temperature. During the idling experiment, the idling time from low speed to high speed needs to be kept within 2 hours. The time of idling at the highest speed needs to be more than 30 minutes, the bearing parts should be kept flexible and the noise is small, and the working temperature should be kept below 50℃.

There are many ways in the process of bearing clearance adjustment, such as shim adjustment method, nut adjustment method, screw cover adjustment method and inner jacket adjustment method. Generally speaking, the most commonly used method is the shim adjustment method. When assembling, the inner hole of the bearing sleeve is based on lubricating oil, which can reduce the friction effect and also play a cooling effect on the parts in the bearing. After the bearing clearance is adjusted, the heat generated by its friction increases, and the temperature of the axle box assembly also increases. The heat generated will have an impact on the size of the part, which will affect the bearing clearance, generate more heat, and form a vicious circle. Therefore, it is necessary to adjust the bearing clearance to reduce friction, and to use circulating lubricating oil to disperse heat, which can effectively control the temperature and ultimately ensure the thermal balance of the system.

2.3 Inspection and maintenance

In the process of bearing detection, it is necessary to monitor and inspect the actual situation of the bearing according to its relevant technical requirements, including the load, rolling sound, speed, temperature and lubrication state, etc. Find the cause of the abnormal state and make effective rectification for the problem. In the process of bearing maintenance, it is necessary to use strict technological process and technical requirements for maintenance. For disassembled bearings, it is necessary to check whether they can be used for a second time. Use professional and advanced disassembly tools to correctly disassemble the bearing. During the inspection of the bearing, it is necessary to sample and analyze the appearance of the bearing and the residual amount of lubricant, and use gasoline or other cleaning agents to clean the bearing. In terms of bearing cleaning, it is necessary to achieve rough cleaning and fine cleaning. Coarse cleaning is to use a brush to clean grease and sticky objects. Fine cleaning is mainly to use cleaning oil to clean the bearing during the rotation process. The rolling surface, rolling surface, mating surface and cage should also be checked. If there are burrs and cracks in the rolling elements, the breaking of the rolling elements in the inner and outer rings, the raceway surface, the ribs, and the jamming of the rolling elements, it cannot be used. Whether the bearing can be used twice, it is necessary to analyze and consider the damage degree of the bearing, use the conditions and periodic maintenance, and use professional tools and equipment to inspect and measure in accordance with relevant technical specifications. In the running part of the high-speed railway vehicle, that is, the bogie belongs to the core component of the train, which can ensure the safe and stable operation of the train at high speed. The bearing belongs to the key component. The wheel of the vehicle is based on the axle box, spring and bogie frame. Realize the effective connection with the car body. The bearing of the axle box can effectively carry the self-weight and load of the vehicle, as well as the longitudinal, lateral and even vertical impact force generated by the rail on the wheels. The bearing capacity and endurance generated in the process of bringing additional force play the largest bearing role.

3 Faults and solutions for the application of rolling bearings in railway vehicles

First of all, it is necessary to improve the effectiveness of bearing selection, so as to strengthen and improve the maintenance control of bearings. Technicians and researchers have analyzed the causes of the failures. The quality of wheel bearings needs to be improved to achieve a reasonable distribution of talents. According to the foreign situation, our country introduces advanced production technology and production means, and proposes a technical method suitable for the development of domestic bearing enterprises in our country. In my country, the information management database and management mechanism of its bearing quality are also constantly innovating and applying bearings in various industries. In view of the problems that occur in the use of bearings in my country, it is necessary to increase its claims settlement mechanism and make a good evaluation. scheme to avoid a lot of waste of human and material resources of bearing enterprises. For the finished bearing, the quality of the bearing needs to be tested to effectively avoid hidden problems in the bearing.

Secondly, it is necessary to carry out reasonable and standardized inspections on maintenance to improve the scientific control of external factors. For vehicle maintenance, it is necessary to check and adjust its dynamic balance. In the process of processing and designing the wheel, its diameter and radius need to be guaranteed to be within a reasonable range, so as to achieve scientific coordination and cooperation. For the data of each area, it is necessary to avoid the difference phenomenon. In the process of bearing design, the designer needs to effectively prevent the mechanical equipment with excessive friction, and have a good protection for the gap between the rails. For managers, it is necessary to prohibit the illegal welding operation of vehicles caused by some unfavorable factors, so as to avoid unqualified modification. After the bearing is designed, it is necessary to strengthen the inspection of the bearing to avoid some unnecessary failures during use.

Finally, the accuracy of the bearing temperature needs to be standardized to a certain extent, combined with the judgment of the system itself to realize the judgment of the bearing temperature. Due to the relatively long period of time and mileage used by the bearing during use, the temperature difference is relatively large. Therefore, it is necessary to check the temperature of the bearing after the bearing is designed to ensure the accurate data of the bearing temperature. In this process, it is necessary to use infrared rays to survey the bearing temperature, continuously optimize, improve and innovate the forecasting equipment technology, and realize the innovative application of technical methods according to the actual development requirements. The anti-interference performance of the bearing should also be improved. Make reasonable adjustments to the appearance and shape of the bearing equipment to ensure the accuracy of the data, so as to realize the accurate judgment of the internal temperature rise factor of the rolling bearing, which is conducive to the analysis of the cause of the fault judgment.

4 Conclusion

To sum up, in the process of high-speed operation of locomotives and vehicles, bearings are a core key component, and it is necessary to effectively improve and optimize the impact and vibration resistance, safety and reliability of the bearing itself, so as to achieve high bearing capacity and high strength. At the same time, condition monitoring and fault diagnosis are required for bearings to realize the safe and stable operation of high-speed railways in my country.