Abstract: Described are the latest compact type tapered bearing unit developed by SKF Company for high speed cars.
Key words: rolling stock ; bearing ; application
1 General
Bearing, an important part related to driving safety, is one of the most important parts in railway vehicle parts. The train is required to operate under very strict working conditions. Especially under the operation conditions of radial, axial and sometimes high acceleration in the direction of rotation, it is required that the maintenance cycle of railway bearings must be extended and their functions must be maintained with maximum reliability. For this kind of requirement, only relying on the talents with profound knowledge and experience, and constantly improving their safety, can we develop the railway bearings with high cost performance.
In the long-distance passenger transport services in Europe, North America and Asia, high-speed trains are becoming more and more important in the competition with airlines and highways. SKF is participating in the development plan of high-speed vehicles by providing spare parts for railway vehicles to major railway vehicle manufacturers in the world, such as Alstom, Bombardier, Kaffi, Fiat, Kawasaki Heavy Industries and Siemens. When developing axle boxes for high-speed vehicles, we will focus on developing the highest performance bearings with the best sealing performance and low operating temperature, long service life of lubricating grease.
In addition, the results of stress calculation and fatigue test using advanced finite element analysis method are applied to the design of axle box shell. As the latest development product, we have developed a compact tapered rolling bearing assembly (CTBU), which is equipped with sensors to monitor the speed and bearing status.
2 Design concept of compact TBU
In the work of reducing product life cost, its design is the key. Because the compact design can extend the maintenance cycle, at the same time, it can further improve the performance and safety. This design can shorten the axle, reduce the bending of the axle caused by the bearing, and reduce the unsprung mass. Due to the use of polymer liner, it can also completely prevent the friction and corrosion on the mating surface between the inner ring and the backstop. In this bearing design, polymer cage and low friction contact seal are used. This compact TBU bearing (Fig. 1) is equipped with sensors for speed and bearing status monitoring for users to choose from.
Figure 1 Features of compact TBU
3 Bearing characteristics
3.1 Polymer cage
SKF Company adopted polymer cage (Figure 2) in the conical rolling bearing parts (TBU) produced in 1990, and collected a large amount of experience and data from various aspects. The freight trains in European countries also have their application examples, and Chinese railways are used as standard components. At present, all kinds of railway vehicles, including high-speed trains, are using polymer cages. This optimized cage is made of reinforced polymer. The application practice proves that it has excellent performance. For railway vehicle management personnel, the main advantages of this bearing cage can reduce friction, ease roller sliding, reduce wear, reduce operating temperature, and improve safety. Once the bearing is in a damaged state, the bearing will not cause rotation obstacles, and can operate continuously.
Fig. 2 Polymer cage for TBU
3.2 Built in low contact seal
The design principle of this bearing is that the sealing seat and gasket (Spacer) are eliminated, and the sealing function is built in between the outer ring and the inner ring of the bearing (Fig. 3). Therefore, the space is saved, and the bending of the axle can be restrained in many applications. The main feature of this seal design is that based on the principle of low friction rubber seal, labyrinth seal, lip seal and oil throwing plate parts are combined. As the isolation and protection of pollution are improved, it is possible to extend the service life. The friction torque is 75% lower than that of the single-sided sealing structure. Since the temperature is also reduced by about 20 ℃, the long-life and energy saving of the grease can be realized. SKF Company confirmed that it is particularly effective to prevent water and dust pollution according to the tests carried out. Under very strict operating conditions, the long-term durability test was carried out and good results were obtained. In addition, this new built-in seal is also qualified in all certification tests conducted by the North American Association of Railways (AAR).
Fig. 3 Structure and basic principle of built-in seal
3.3 Polymer liner
It is reported that friction corrosion often occurs on the mating surface between the inner ring and the rear cover. Friction corrosion not only causes foreign matters (iron wear powder) to enter the bearing, but also becomes the reason for increasing axial clearance, which is related to reducing the performance and reliability of the bearing. The goal of development is to prevent the development of this friction corrosion. Therefore, the contact between steel and steel is changed into the combination of steel and polymer in order to stop the development of friction corrosion. The liner is made of reinforced polymer material and fixed on the bearing parts (Fig. 4).
Fig. 4 Polymer liner
4 Application example of TBU bearing
4.1 Application on tilting train
The earliest tilting train of Italian railway is ETR 450, which has been put into commercial operation since 1985. Pendolino has a maximum speed of 250 km/h, which is manufactured by Fiat, a subsidiary of Alstom. The axle box of Pendolino train is installed with TBU 130 from SKF × 220 bearing.
TBU 130 designed by SKF company is installed on the 2nd generation Pendolino tilting train × 230 bearing, built-in speed sensor and axle box designed by SKF. Since 1992, this train has been put into operation in Italy as ETR 460 and ETR 480 (Figure 5), while in Finland it has been put into operation as Sm3 train. In addition, Switzerland is called "Cisalpino ETR 470" and Portugal is called "Pendoluso" train. The newly designed tilting train of the same model also operates in the Czech Republic.
The tilting train X2000 in Sweden has a maximum speed of 220 km/h (Figure 6) and is equipped with TBU 130 manufactured by SKF × 220 bearings, including one train running in China.
Figure 5 Italian ETR 480 Train
Figure 6 Sweden X2000 Train
4.2 Application on European high-speed trains
Italy's high-speed train ETR 500 has a maximum speed of 300 km/h (Figure 7), and the bogie is manufactured by Fiat/Alstom. TBU 150 is installed on the power car of the train × 250 type bearing, TBU 130 is installed on the trailer × 220 bearing. The two sizes of bearings are equipped with speed sensors and temperature sensors as standard.
Almost all ICE high-speed trains in operation in Germany are installed with SKF bearings. TBU 130 is installed on ICE 2 trailers running at a maximum speed of 280 km/h × 230 bearing, bogie designed by Siemens. TBU 150 is used on ICE 1 and ICE 2 trailers × 250 type rolling bearing.
Figure 7 Italian ETR 500 Train
For SNCF, as the axle bearing for TGV Atlantic Line, SKF's TBU bearing has been certified.
4.3 application on high-speed trains in Taiwan, China
In Asia, SKF was selected as the export manufacturer of axle box bearings on Taiwan, China's high-speed vehicles that Japan exported Shinkansen high-speed vehicle technology overseas for the first time, and it accepted orders for axle box bearings of 360 vehicles in total. The maximum speed of the vehicle is 300 km/h (Figure 8).
Figure 8 Taiwan, China high speed train T700
As we have accumulated unique experience in bearing production and application on many high-speed trains on major railway lines in Europe, SKF can provide products and technical knowledge including axle bearing components and spare parts. SKF attaches importance to the improvement of product performance to ensure safety, which is an important reason why Taiwan, China high-speed railway chooses SKF Bearing products.
More about UNIM Wheel Hub Bearing:
The main function of hub bearing of UNIM is to bear load and provide accurate guidance for the rotation of hub. It bears both axial load and radial load. It is a very important part. The traditional automobile wheel bearing is composed of two sets of tapered roller bearings or ball bearings. The installation, oiling, sealing and clearance adjustment of the bearing are carried out on the automobile production line. This structure makes it difficult to assemble in the automobile factory, high cost and poor reliability. Moreover, when the automobile is maintained at the maintenance point, the bearing needs to be cleaned, oiled and adjusted. Hub bearing unit is developed on the basis of standard angular contact ball bearing and tapered roller bearing. It integrates the two sets of bearings. It has the advantages of good assembly performance, omitting clearance adjustment, light weight, compact structure, large load capacity, pre loading grease for sealed bearings, omitting external hub sealing and free from maintenance. It has been widely used in cars and gradually expanded in trucks.
2022-09-30
