With the requirements of urban environment and the public's need for green travel, indoor rail transit has become the most popular means of transportation for the public. As a solution that can effectively improve ride comfort and reduce noise emissions during operation, elastic wheels are increasingly becoming the mainstream configuration of urban rail transit vehicles.

Tags: elastic wheels; subway: indoor rail transit

With the rapid development of cities and urbanization in our country, the urban population has experienced concentrated and explosive growth. The public travel mode in large and medium-sized cities has become one of the current problems restricting urban development. As a form of urban transportation, urban rail transit has the advantages of large transportation capacity, fast speed, safety, punctuality, and environmental protection. It is becoming the preferred transportation method for the urban public. At present, urban rail transit can be divided into several types such as subway, tram and light rail according to its capacity range, vehicle type and main technical characteristics.

The subway is currently the most common rail transit system. It is powered by electric traction, wheel-rail guidance, and has a relatively heavy axle load. It runs according to the operation chart. The vehicles are grouped and run in underground tunnels. It does not pollute the environment and saves urban land. It is suitable for Central areas of cities with long travel distances and large passenger flow demand.

Trams are low-capacity rail transit systems that use tram traction, light rail guidance, and 1 to 3 groupings to run on urban road lines. Tram lines are generally located in the city center and run through streets and alleys, making it easy to get on and off the train.

Light rail is an urban rail transit system modified and developed based on trams. Its axle load is generally lighter than that of subways. Light rail is generally constructed using a combination of ground and elevated lines, and the lines can run from the city to the suburbs.

Different from the dedicated railway lines used by high-speed EMUs, urban rail transit lines are generally built in areas with large passenger flow such as bustling commercial centers and residential areas, and the lines need to be planned according to the traffic location and surrounding environment. In some cases Only lines with smaller curve radii will be constructed. In this case, improving the ride comfort of the train and reducing the impact on the surrounding environment during train operation have become issues that need to be considered during train design. Therefore, the elastic wheel came into being. As a solution that can effectively improve ride comfort and reduce operating noise emissions, elastic wheels are increasingly becoming the mainstream for urban rail transit vehicles.

wheel parts

Elastic wheels are mainly assembled from the following components:

Tire: The part of the wheel that is in direct contact with the track;

Wheel center: The part of the wheel that interfaces with the wheel set/axle/axle bridge;

Wheel ring: lock the rubber block in the cavity formed between the wheel hoop and the wheel ring, and provide appropriate preload to the rubber block;

Rubber block: Located between the wheel hoop and the wheel center, it provides flexible radial stiffness, axial stiffness and circumferential stiffness. According to the load-bearing state of the wheel rubber components, it can be divided into shear type, compression type and shear compression type;

Fastening screws and washers: ensure the tightening of the entire system and provide appropriate pre-tightening force for the wheel ring:

Ground Conductor: Maintains current path between hoop and wheelset:

Noise reduction plate: optional, used to reduce noise emissions during wheel use if necessary.

By adding a rubber block with damping effect between the wheel hoop and the wheel center, the impact noise of the wheel rail can be reduced, the impact vibration of the wheel rail can be alleviated, the dynamic stress of the bogie transmission device can be reduced, the wear of the wheel rail can be reduced, and the use of lines and vehicles can be improved. lifespan and improve vehicle operation stability.

Since the elastic wheel adopts a split structure, the wheel does not need to be removed from the axle or axle bridge during maintenance. It is only necessary to loosen the fastening screws on the wheel ring and wheel center from the outside, and then remove the wheel hoop and rubber block. Just remove it from the wheelset and replace it. This method can greatly improve the maintenance efficiency of the wheel set, avoid wheel seat strain, and reduce maintenance costs and product life cycle costs.

Noise reduction system

A rubber block has been added between the steel wheel hoop and the wheel center of the elastic wheel, and part of the noise can be reduced through the damping effect of the rubber. However, for cities with strict noise emission requirements, or for certain lines with very poor working conditions (producing whistling), a noise reduction system needs to be used to control noise emissions during wheel use.

After years of research and experimental verification, Luchini has developed the Gelene noise reduction system. The system consists of two specially designed steel plates that match the resonant frequency of the wheel rim (the frequency that can cause squealing). A viscoelastic layer with a damping effect is added between the two steel plates to quickly attenuate when the wheel reaches the resonant frequency. vibration energy, reducing noise emission levels.

The noise reduction plate can be assembled directly on the wheel rim using anti-vibration screws, or installed on a special assembly ring in the wheel rim groove through positioning pins. After laboratory analysis, the noise emission level of elastic wheels equipped with Gelene noise reduction system is about 10dB(A) lower than that of elastic wheels without noise reduction system under the same excitation state.

Safety and performance

The development of elastic wheels has gone through twists and turns. Among them, the IEC train accident equipped with elastic wheels in 1998 caused the development of elastic wheels to enter a stagnant stage. However, through the analysis of the accident wheel set, it was mainly due to defects in the material of the wheel rims. The conditions for over-detection were not available at the time, so the over-limit defects may not be discovered in time. Under high-speed operation, the tire eventually broke due to fatigue, causing an accident. Over the years, the manufacturing level of wheel materials has improved greatly, and the stiffness control of the rubber block has continued to improve. The operation of elastic wheels has been proven to be very safe at operating speeds below 110km/h and with regular preventive maintenance.