Axle box device is a component on railway locomotives and vehicles that is sleeved on the axle journal to connect the wheel set and the bogie frame or the two-axle car body, referred to as the axle box.

Axle box device is a component on railway locomotives and vehicles that is sleeved on the axle journal to connect the wheel set and the bogie frame or the two-axle car body, referred to as the axle box. Its function is to transfer the weight and load of the car body to the wheelset, lubricate the axle journal, reduce friction and reduce running resistance. Axle box devices are divided into sliding bearing axle box devices and rolling bearing axle box devices according to the type of bearings used. Early locomotives and rolling stock used sliding bearing axle box devices. In the early 20th century, the rolling bearing axle box device was tried out, and the sliding bearing axle box device has been gradually replaced. Passenger cars, diesel locomotives and electric locomotives of China Railway have all adopted rolling bearing axle box devices, and freight cars have partially adopted them.

Sliding bearing axle box device

The axle box of the truck is mounted on the outer side of the wheel and consists of an axle box body, an axle box cover, a bearing bush, a bearing pad, an oil lubricating device and a dustproof plate. The axle box on the steam locomotive wheel and the guide wheel is installed on the inner side of the wheel, and an oil box is used to lubricate the axle journal, and the other parts are the same as the above parts.

Axle box body

The parts that bear load and store shaft oil are used to contain shaft journals and other parts. In the early days, it was made of cast iron and generally made of cast steel. The axle box body not only transmits the load from the frame to the axle journal, but also bears the load supported by the jack from the bottom when the bearing is repaired and replaced, so it must have sufficient strength. The coaxial box cover of the axle box body must be tightly fitted to avoid oil leakage and prevent rain and dust from entering. The axle box body has two kinds of guide frame type and non-guide frame type.

The bearing bush rubs against the shaft journal and transmits all the loads borne by the shaft box body to the shaft journal. It is composed of the bush body and a layer of anti-friction alloy on its surface. In the early days, the tile body was cast with copper alloy, and later it was replaced with a steel backed copper lining. China used nodular cast iron. The anti-friction bearing alloy used on Chinese railway vehicles, commonly known as white alloy, is a lead-antimony-tin alloy. This alloy is easy to scrape, has good compression resistance, anti-friction, and heat resistance properties, and is easy to cast. In recent years, in order to prevent the bearing bush from being scrapped prematurely and avoid burning axles, plastic bushings have been inlaid on the front end of the bushings of trucks with more than 50 tons.

Bearing plate

It is a part that is installed between the axle box body and the bearing shell for load transmission. Its upper surface is arc-shaped to improve the load distribution on the white metal surface. When replacing the bearing bush, first remove the backing plate to reduce the lifting height of the jack.

Oil lubrication device

A device that supplies shaft oil between the bearing bush and the journal to reduce friction. It is composed of oil roll, wooden front sleeper and rear baffle, and is installed in the axle box. The oil roll is filled with shaft oil (lubricating oil) and is in contact with the lower part of the journal. When the vehicle is running, the axle journal rotates, bringing the axle oil between the bearing bush and the axle journal, forming an oil film, and turning dry friction into liquid friction. Early oil rolls were mostly made of cotton wool, and some used oil brushes. In recent years, Chinese railway vehicles have switched to oil rolls with foamed plastic outsourcing towel covers. The function of the wooden front pillow is to replace the oil roll at the outer end of the journal and prevent the oil roll from moving outside. The rear baffle is used to prevent the shaft oil from overflowing from the rear end of the journal.

Dustproof board

Its function is the same as the axle box cover, so it is also called the axle box rear cover. It is located in the interlayer on the rear wall of the axle box, mostly wood. The wooden dust-proof plate has poor sealing performance and often leaks shaft oil. In recent years, rubber dust-proof plates have been gradually used.

Rolling bearing axle box device

Advantages of rolling bearing axle box device

Compared with the sliding bearing axle box device, the rolling bearing axle box device can reduce the running resistance of the rolling stock by about 10%, and can reduce the starting resistance by more than 80%. It can not only save power consumption, increase the running speed, but also increase the traction weight of the train. The components of this device have a small running clearance, which is beneficial to improve the running quality of rolling stock. It has a low failure rate during operation and can reduce the manpower and material consumption of maintenance work. Therefore, although the manufacturing cost of the rolling bearing axle box device is much higher than that of the sliding bearing axle box device, it is still widely used.

composition

Rolling bearing axle box device usually consists of axle box body, front and rear axle box cover, rolling bearing, sealing device and other parts. The rolling bearings used are cylindrical, conical and spherical. Among them, spherical rolling bearings bear the axial load better, but require a larger size, which is not conducive to reducing the weight of the unsprung, and the manufacturing cost is high, and the maintenance is inconvenient. Therefore, it has been used less in recent years.

Chinese railways use cylindrical rolling bearing axle box devices on passenger cars, and mainly use this kind of axle box devices on diesel locomotives and electric locomotives. On passenger cars, the axial force is borne by the ribs on the inner and outer rings of the bearing, while the bearings on the locomotive generally do not have ribs, and the axial force is borne by the ball bearings mounted on the shaft end. Except for some of the trucks using cylindrical rolling bearing axle box devices, new trucks mainly use sealed tapered rolling bearing axle box devices. The tapered rolling bearing is equipped with sealing devices at both ends, and the upper outer ring is a carrying saddle, which is installed in the side frame of the bogie to transfer the load. There is no axle box outside the bearing. Therefore, this structure is called "shaftless bearing device". The rolling bearings are all greased, so there is no need to open the cover and refuel or check frequently.

Maintenance of FAG axle box device

During the use of bearings, FAG bearings and axle boxes require long-term maintenance. Because this will not only extend the life of the bearing itself, but also reduce the cost of the business.

The maintenance of the FAG bearing axle box is generally less trouble than that of the sliding bearing axle box. There is no need to replace the bushes and refuel frequently, and there are fewer accidents of the burning shaft. However, it should not be careless. Once the bearing is damaged and the combustion shaft is caused, it will be inconvenient to deal with in the middle of the operation, and the wheel set has to be replaced or the car is thrown away. Therefore, vehicle maintenance personnel need to check the axle temperature frequently, check whether the axle box has cracks, oil spills, and loose bolts. The temperature of the bearing is mainly determined by the rolling friction between the roller and the inner and outer ring raceways, the sliding friction between the roller and the cage, the sliding friction between the end of the roller and the ribs of the inner and outer rings, and the difference between the roller and the lubricating grease. Heat generated by friction. The temperature is generally relatively low.

The axle box temperature is related to many factors, such as the load on the FAG bearing, operating speed, line status, air temperature, wind speed, continuous running time, quantity and status of lubricating grease, etc., all have a significant impact on the axle temperature. Two to three hours after the start of the vehicle, the bearing temperature tends to stabilize, and the heat generated by the friction of the bearing and the heat radiated from the outer surface of the axle box are close to balance. In the cold northern areas, the surface of the axle box dissipates heat quickly. The temperature difference between the top of the axle box and the inside of the bearing is as much as 30 to 40 degrees, while in the southern hot season, the temperature difference between the top of the axle box and the inside of the bearing is only about 100 degrees. Usually in summer, the temperature of the axle box on the side of the sun is much higher than the side of the back sun.

The top of the axle box of the FAG bearing is only about 15-x-300C higher than the air temperature under normal conditions. If the temperature on the top of the axle box in the same vehicle is more than four hundred degrees higher than the temperature, it is an abnormal phenomenon and the cause should be investigated. Because there are few factors that affect bearing temperature, especially train running speed, grease quality and bearing clearance size have a greater impact on bearing temperature, so the calculation formula for bearing allowable temperature is currently not available. Under normal circumstances, you can Use external temperature +40 as the allowable temperature of the bearing and measure it on the top of the axle box. For the spare wheel set equipped with the axle box of roller bearings, the axle box should be rotated every half month or so to prevent the bearing from rusting.