Research On Dynamic Load Sharing Modeling Method And Load Sharing Law Of Helicopter Planetary Gear Train

Planetary gear trains have the advantages of compact structure,strong load carrying capacity,large transmission torque,and low vibration and noise.Therefore,they are widely used in various vehicle engineering,marine power,tanks,armored vehicle transmission systems,and other largescale precision equipment,especially in helicopter transmission systems.There are two main sources of transmission error in planetary gear train transmission systems.One is the cumulative error caused by industrial machine accuracy issues,which causes manufacturing errors in the production and manufacturing process of gears.The other is the installation error caused by insufficient installation equipment accuracy during the installation process.The above two error coupling effects cause differences in the meshing forces of each transmission branch of the planetary gear train,resulting in uneven loading of the entire planetary gear train,affecting the stability and reliability of the entire transmission system.To solve this problem,this paper considers the real meshing state of two tooth surfaces in contact,establishes a TCA/LTCA model for the internal and external meshing of spur gear pairs,and solves the model to obtain timevarying meshing stiffness,an important excitation parameter during the internal and external meshing process;A dynamic model of a spur gear pair planetary gear train including installation errors,planetary gear modification design,and flexible ring gear structure was established,and the key parameters were calculated to analyze the impact of each parameter on the load sharing performance.The specific content is as follows:(1)Based on the principle of gear meshing and the definition of gear pair meshing stiffness,a method for calculating the time-varying meshing stiffness of straight cylindrical gear pairs under real meshing conditions through tooth contact analysis(TCA)/load tooth contact analysis(LTCA)is proposed.On the basis of considering the tooth modification design and installation errors of spur gear pairs,TCA and LTCA analysis models of spur gear pairs under real meshing conditions are constructed.The method of combining mathematical programming and finite element method is used to obtain the tooth surface load distribution factor and transmission error.Through three Hermite interpolations,the time-varying meshing stiffness of the gear pair within a meshing cycle is calculated.The results show that topological modification can affect the amplitude and mean value of time-varying meshing stiffness of spur gear pairs,and the timevarying meshing stiffness tends to decrease as the amount of modification increases.(2)A dynamic model of a planetary gear train with a flexible gear ring and a thin-walled hollow support shaft structure was established using the lumped mass method.The meshing damping and manufacturing error projections on the meshing line were calculated,respectively.Carry out force analysis on the components included in the dynamic model,derive and solve the dynamic equation of the planetary gear train based on the acceleration law,calculate the meshing forces of each branch,and then calculate the load sharing coefficient.Using the control variable method,the effects of the thickness of the hollow support shaft,the thickness of the gear ring,the rotational speed of the input shaft,and the buoyancy of the sun gear on the load sharing performance of the planetary gear train were investigated,keeping other parameters unchanged.(3)A planetary gear train containing five planetary wheels was verified by load sharing experiments.Design a strain bridge and an experimental scheme,using strain measurement methods to measure the deformation of the loaded gear teeth.The data collected by the sensor is visually processed through programming software,and the required results are obtained after filtering.The displacement of each degree of freedom of the component is substituted into the formula to obtain the meshing force of each planetary gear,and then the load sharing coefficient of the planetary gear train is obtained.And compared with the simulation results in chapter 4 to verify the correctness of the simulation results.