The operating conditions of the drum shearer are very complex, and its ranging arm gear system often suffers from gear scuffing and wear. Gear scuffing is caused by the adhesive wear, which is due to the instantaneous friction and flash temperature of the tooth surface, and the gear meshing power loss is also caused by tooth surface friction. In order to resist tooth scuffing and improve meshing efficiency of the transmission system, an improved semi-analytical tooth surface flash temperature calculation method was used. The tooth flash temperature status under various working conditions were analyzed in detail. Based on the mechanical model of the shearer drum picks, the load condition of the drum was analyzed. Under these load and boundary conditions, the misalignments of each gear pair in the ranging arm were calculated. The tooth surface load distribution was calculated under the gear misalignments, and then the theoretical tooth surface flash temperature and meshing power loss were determined. Next, the tooth micro-geometry was modified to reduce flash temperature and meshing power loss. The flash temperature distribution pattern of the optimized tooth surface was studied under various working conditions, and the meshing power loss was also obtained. Finally, experiments were conducted to verify the effects of the optimized tooth surface on the friction temperature rise and the effectiveness of the modification method. Tooth surface optimization aimed at reducing tooth surface flash temperature can also effectively reduce meshing power loss, which has a significant effect on gear anti-scuffing and energy saving.

Planetary bearings are critical components in double planetary gear trains. The influence of carrier rotation direction on bearing dynamic behavior remains insufficiently understood, which hinders accurate reliability assessment and optimal design. To investigate this issue, a dynamic model of the double planetary gear train is developed. The model captures the coupled interactions and motion characteristics of both gears and bearings. Furthermore, an experimental platform is constructed to validate the accuracy of the proposed model. A comparative analysis is conducted to examine the dynamic loads and vibration responses of the planetary bearings under forward and reverse carrier rotations. The results show that reverse rotation significantly intensifies collision forces, particularly under low-speed and high-torque conditions, where the increases for inner and outer bearings reach 38.34% and 31.25%, respectively. In terms of contact forces, the inner bearing exhibits higher loads under reverse rotation, whereas the outer bearing carries greater loads under forward rotation. Vibration response analysis reveals that the carrier rotation direction has a limited effect on the vibration of the inner bearing, but significantly amplifies that of the outer bearing. Under reverse rotation, the acceleration amplitudes of the outer cage in the x- and y-directions increase by 96.20% and 95.74%, respectively, markedly exceeding the approximate 26% increase observed for the inner bearing. This study provides new insights into the asymmetric tribological behavior of planetary bearings under bidirectional rotation. These findings provide theoretical guidance for the design and optimization of planetary bearings in double planetary gear trains.

Gear skiving is an efficient and high-precision gear processing method, particularly advantageous for internal gears and coupling gears. However, the main limitation of its application is the rapid wear of skiving tools. This paper combines simulation analysis and numerical calculations to reveal the essential characteristics of the gear skiving process and the fundamental causes of tool wear. Firstly, it researches the distribution of cutting loads on the tool edges through the kinematic simulation analysis of gear skiving. Then, it analyzes the changing rule of working angle, clearance angle, tool inclination, and cutting speed and reveals the cutting state and chip flow patterns during the skiving process through numerical simulation calculations of gear skiving. Finally, it investigates the chip formation mechanism and the stress variation rule on the tool edges through finite element simulation of gear skiving. These analyses and calculations provide optimization guidance and methods for improving the cutting performance and the service life of skiving tools.