| In the past few decades,the gear transmission system of the high-performance aviation rotorcraft has been the focus of research and development.It accounts for a considerable proportion of the load capacity and power transportation of the entire equipment.It converts the input power of the engine at high speed into the take-off rotor speed of the main and tail at low speed.Among them,gears play an extremely important role to achieve these functions.Up to now,most rotorcrafts adopt conventional transmission technology,and the transmission system still uses straight/helical gears or spiral bevel gears.Research has found that face gears have greater potential advantages than traditional gears in the transmission field,which are not subject to radial force,are insensitive to axial errors,and have strong transmission tolerances.They have extremely broad military and civilian equipment application prospects.In addition,the cooperation of face gears and spur gears can realize power split and reversal,with stable high reduction ratio and load sharing performance.The mixed gear pair with orthogonal face gear and non-orthogonal face gear has no limitation of shaft intersection angle,and the pressure angle and modulus are flexible.It has important scientific value for expanding the type of gear transmission mechanism and enriching the face gear system,and has irreplaceable unique advantages in extreme transmission occasions.This paper takes an aviation double input face gear split-parallel transmission system as the research object,and mainly carries out the research on the dynamics,static load sharing characteristics and natural characteristics of the transmission system.The research contents include: the time-varying meshing stiffness calculation,static load sharing characteristics research,dynamics load sharing characteristics research and natural characteristics research.The specific research work is as follows:First,the calculation method of the international standard ISO6336-2006 is used to solve the meshing stiffness of the cylindrical gear pairs in the transmission system.The meaning of the face gear drive is introduced in detail,and the theoretical basis and analysis steps for calculating the meshing stiffness of the face gear transmission by the finite element method are given.Further,the time-varying meshing stiffness of the face gear pairs included in the transmission system is obtained through experiments.It lays a numerical foundation for studying the load sharing characteristics of the double input face gear split-parallel transmission system.Secondly,taking into account the support and torsional deformation of the transmission shaft,the simple harmonic function is used to express the projection of the eccentric error on the meshing line,and the statics model of the load sharing characteristics of the double input face gear split-parallel transmission system including the error and stiffness is established.Meanwhile,the statics equations of the system are constructed combined with the relative displacement between gears.The meshing force between gear pairs and the static load sharing coefficient of each drive stage are obtained by solving the equations,and the effects of eccentric error,support stiffness and torsional stiffness on the static load sharing characteristics of the transmission system are studied.Third,the double input face gear split-parallel transmission system is divided into three subsystems for processing,and the subsystems and the overall system are refined dynamic modeling.In addition,considering the stiffness excitation and error excitation,the dynamic balance equations of each gear in the transmission system is deduced according to Newton’s second law.The dynamic load sharing coefficients of each drive stage in the system are calculated,and the load sharing characteristics are studied.Finally,the dynamic equation of the double input face gear split-parallel transmission system is simplified to an undamped free vibration equation,and the eigenvalues are solved to obtain the natural frequencies and mode vectors of the transmission system.Further,the influence rules of meshing stiffness and support stiffness on the natural frequencies and the modal transition phenomenon when the stiffness changes are studied.It provides a theoretical basis for avoiding the resonance zone of the transmission system by optimizing the system parameters.Meanwhile,by solving the modal strain energy and kinetic energy of the system,the frequency order corresponding to the larger modal energy of each gear was revealed. |
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