The complex three-shaft three-reducer structural designs of helicopter transmission systems are prone to changes in the relative positions of shafting under the conditions of main rotor and tail rotor loads. These changes will affect the transmission characteristics of the entire transmission system. In this study, the planetary gear trains of helicopters were examined. Due to the fact that these structures are considered to be the most representative structures of the main reducers of helicopters, they were selected as the study objects for the purpose of examining the meshing characteristics of planetary gear trains when the relative positions of the shafting changed due to the position changes of the main rotor shafts under variable load conditions. It was found that by embedding the comprehensive time-varying meshing stiffness values of the main rotor shafts at different positions, a dynamic model of the relative position changes of the planetary gear trains could be established. Then, combined with the multibody dynamics software, the meshing characteristics of the sun gears, and the planetary gears, the planetary gears and the inner ring gears were simulated and analyzed under different inclinations and offsets of the shafting. The results obtained in this study revealed the following: (1) the average meshing force of the gears increased with the increases in the angle inclinations, and the meshing force between the sun gears and the planetary gears increased faster than the meshing force between the planetary gears and the inner ring gears. It was observed that during the changes in the shafting tilt positions, obvious side frequency signals had appeared around the peak of the meshing frequency in the spectrum. Then, with the continuous increases in the tilt position, the peak was gradually submerged; (2) the average meshing force of the gears increased with the increases in the offset, and the increasing trend of the meshing force between the sun gears and the planetary gears was similar to that observed between the planetary gears and the inner ring gears. It was found that when the shafting offset position changed, there were obvious first and second frequency doubling in the spectrum; (3) the mass center orbit radii of the sun gears increased with the increases in the shafting position changes, and the changes in the angular tilt position were found to have greater influencing effects on the mass center orbit radii of the sun gears than the changes in the offset positions. This study’s research findings will provide a theoretical basis for future operational status monitoring of the main transmission systems of helicopters and are of major significance for improvements in the operational stability of helicopter transmission systems, which will potentially ensure safe and efficient operations.

中文翻译：

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发生轴位变化的直升机主行星齿轮系的齿轮啮合特性分析

直升机传动系统复杂的三轴三减速器结构设计，在主旋翼和尾桨载荷条件下，轴系相对位置容易发生变化。这些变化会影响整个传输系统的传输特性。在这项研究中，对直升机的行星齿轮系进行了检查。由于这些结构被认为是直升机主减速器中最具代表性的结构，因此选择它们作为研究对象，目的是检验当轴系相对位置发生变化时行星齿轮系的啮合特性。变负载条件下主转子轴的位置变化。结果表明，通过嵌入主转子轴在不同位置的综合时变啮合刚度值，可以建立行星齿轮系相对位置变化的动力学模型。然后结合多体动力学软件，对轴系不同倾角和偏置下的太阳轮与行星齿轮、行星齿轮和内齿圈的啮合特性进行了仿真分析。研究结果表明：（1）齿轮的平均啮合力随着角度倾角的增加而增加，太阳轮与行星齿轮之间的啮合力增加速度快于行星齿轮之间的啮合力。齿轮和内齿圈。观察到，在轴系倾斜位置的变化过程中，频谱中啮合频率的峰值附近出现了明显的边频信号。然后，随着倾斜位置的不断增加，峰逐渐被淹没；(2)齿轮平均啮合力随着偏移量的增大而增大，太阳轮与行星轮啮合力的增大趋势与行星轮与内齿圈啮合力的增大趋势相似。发现当轴系偏移位置改变时，频谱中出现明显的第一次和第二次倍频；(3)太阳轮的质心轨道半径随着轴系位置变化的增加而增加，并且发现倾斜角位置的变化比偏移位置的变化对太阳轮质心轨道半径的影响更大。本研究的研究成果将为未来直升机主传动系统的运行状态监测提供理论依据，对提高直升机传动系统的运行稳定性、保障安全高效运行具有重要意义。