As a key component of transmission torque and driving vehicle, the safety stability of gearbox directly affects the operation reliability of EMU vehicles. However, due to the complexity of its structure and its poor operating conditions, the gearbox system has become more and more ineffective in recent years, such as seepage oil (oil leakage), high oil temperature, bearing pitting and box cracks. These problems seriously affect the running safety of high-speed trains.

The main function of Gear Box is supporting and accommodating the normal operation of each transmission parts, damping and noise reduction, as shown in Fig. The characteristic of high speed Gear Box is to bear the dynamic load, large impact, high function integration, withstand external shock, complex and compact structure, light weight, high calorific value, temperature rise, seriously affect the service life of gears and bearings, how to effectively deal with the above problems are the key to improve the performance and service life of gear box.

The gearbox is widely used in the motor, and it is an important mechanical part in the wind turbine generator, and its main function is to transmit the power generated by wind turbine to the generator and make it get the corresponding rotational speed. Usually the speed of the wind wheel is very low, far less than the speed required by the generator to generate electricity, it must be achieved by the growth of gear box gear pair, so the gearbox is also called the growth tank. Gear box like the next role: 1, accelerated deceleration, is often said to be variable gear box. 2, change the direction of transmission, for example, we use two fan-shaped gears to transfer force vertically to another axis of rotation. 3, change the torque. Under the same power conditions, the faster the speed of the gear, the smaller the torque of the shaft, the greater the reverse. 4, the function of the clutch: we can separate the engine from the load by separating two gears. such as brake clutch. 5, the distribution of power. For example, we can use an engine to drive multiple shafts through the spindle of the gearbox, thereby enabling a single engine to drive multiple loads.

Gear transmission is the most commonly used transmission mode in mechanical equipment, widely used in all walks of life, as the transmission movement and power of the gear device in almost any large-scale equipment has an important role. Gear failure is an important factor to induce machine failure, so the accurate diagnosis of gear box is of great significance to reduce equipment maintenance cost, prevent sudden accident and reduce production loss.

Gear box is a complex structure of the speed control system, including gears, bearings, transmission shafts, boxes and so on. The box has the function of supporting and sealing in the whole system, and the failure rate is low. According to the characteristics of vibration signal, common fault forms are: meshing vibration of gears, vibration of natural frequencies of gears, vibration caused by gear wear, vibration caused by different shafts of gears, vibration caused by local anomalies of gears.