Model establishment method and bench verification of a double helical gear transmission system for high-speed trains

The gear transmission system is a core power transmission component in electric multiple units (EMUs). Double helical gears possess advantages such as high load-bearing capacity and smooth meshing, making them the preferred choice for transmission systems in high-speed trains. This article considers the unique coupling relationship between two sets of gear pairs in double helical gears. A flexible model of the key components of a transmission system is established on the basis of the finite element substructure condensation method, and a virtual test bench model for a double helical gear transmission system in high-speed trains is developed. Bench tests are conducted to validate the model of the double helical gear transmission system. The results indicate that the simulated time-domain amplitude of vibration acceleration at different measurement points on the gearbox is consistent with the measured values. The RMS values of acceleration at each measurement point are close, and the model accurately simulates frequency domain characteristics such as the gear rotational frequency, harmonics, and meshing frequency. Additionally, the axial forces generated in the transmission system during testing are analyzed via this model. The findings show that angular displacements around the vertical axis occur during the meshing process, leading to nonparallel rotation axes of the two gears, which results in uneven load distributions in the meshing region. This condition generates alternating axial forces within the transmission system. Under the same power conditions, an increase in speed exacerbates the uneven load distribution phenomenon. The results provide a novel dynamic modeling approach for double helical gears, enabling the accurate simulation of vibration responses in double helical gear transmission systems in high-speed trains and supporting the design and manufacture of such systems.