Dynamics Of Three-stage Planetary Gears System Of Main Reducer Used In EPB Shield Tunnelling Machine

Earth pressure balance (EPB) shield tunnelling machine (STM) is a key equipment in shield excavation project, and its main driving system is to drive the cutter head cutting rock and soil, which includes hydraulic motor, main reducer and pinion-ring unit. The main reducer with three-stage planetary gears train (PGT) is the primary part of the driving system. The dynamic behaviors of main reducer are more complex because of the demand for high power density, and the coupling vibration would accelerate its fatigue failure, which has a great effect on system reliability and whole performance. It is an important work before production to study the vibration property of main reducer by dynamic theory and testing.According to the research task of national 863 program (2007AA041802)"EPB STM high-power reducer", and considering the practical operating condition of STM and the guide line of project, for the three-stage planetary gearbox used in EPB STM, the dynamic problems are investigated fairly comprehensively and deeply in this dissertation. The main researches are as following:①Dynamics of 3-stage planetary gears train of STM main reducerAccording to gear mesh theory and Lagrange equation, the torsional dynamic model for multi-stage PGT is developed by lumped-parameter method, and the natural characteristics of 3-stage PGT are computed. Trapezoid waves are used to express the time-varying mesh stiffness, and the mesh phasing relations among planetary gears are analyzed. For the 3-stages planetary gears of shield tunnelling machine, the torsional vibration frequencies are calculated at the different mesh position of sun-planet-ring gearing. According to the characteristics of the gears mesh errors, the harmonic waves with composite shaft frequencies and mesh frequencies are presented to describe the transmission errors of the planetary gears. Considering the time-varying mesh stiffness with different mesh phases of planet gears, the inner excitations of 3-stages planetary gears are analyzed systematically. The dynamic responses of the 3-stages planetary gears are simulated under the inner and external excitation got from a statistical load, and the spectrum properties of gears vibration are also analyzed. The dynamic response of system components are calculated under different speeds for the reducer, and the relationship between gears vibration and the rotational speed of the reducer is studied, which provides the base for choosing the suitable operating condition of driving system of the shield tunnelling machine.②Coupling dynamics of multi-stage PGT—housing of main reducerConsidering the torsional support stiffnesses of ring gears, the coupling torsional dynamic model for multi-stage PGT-housing is developed by lumped-parameter method. The torsional support stiffnesses of ring gears are obtained by using the FE method. Based on the analysis of mesh phase and inner excitations, the system dynamic response and time-frequency characteristics of ring gears are analyzed, and then realize the vibration coupling mechanism between gears train and housing.③The gears train dynamic response of STM main reducer under variable loadThe load characteristics of cutter head are analyzed by developing the mechanical model for the cutter head of EPB shield tunnelling machine. The external load of main reducer is obtained through the torque data of cutter head from the STM control system. According to the fluctuating range and randomness of the load data, the continuous load data are simulated by using the IVS (Insert-value stochastically) and data fitting. The dynamic responses of three-stage PGT of main reducer are computed, moreover, the vibration property and the relationship between the system response and the speed of STM cutter head are investigated.④Experimental and theoretical modal analysis on main reducer housingThe eigenvalue problem is solved by developing the FE model for the gearbox housing, and the low order natural frequencies and corresponding modes are extracted. The modal testing is made for the gearbox housing. The least-squares complex frequency-domain (LSCF) estimation method is used to analyze the modal data, and the natural characteristics of housing are obtained. According to the modal assurance criterion (MAC), the experimental modal parameters are validated. The experimental data is coincided with analytical results, which indicates the accuracy of modal parameters. Modal analysis shows the weak position, which provides a basis for structural optimization.⑤Testing and analysis on dynamic performance of STM main reducerThe frequency responses and natural frequencies of the gearbox are obtained by modal experiment on the basis of the experimental modal analysis method. According to the large speed ratio of 3-stage planetary gearbox, the experimental project of back-to-back power circulation set-up is developed, and the test scheme is designed. The vibration properties of the gearbox are analyzed by using the acceleration data tested under different operating condition, and 1/3 octave structural borne noise have been calculated. The vibration velocities are computed, and the vibration severity is valuated synthetically. The ring gear responses from the theoretical and experimental method are successfully compared, which validates the rationality and validity of the analytical model for multi-stage PGT-housing. The sound pressure level is obtained by sound pressure testing under background noise suppressed through using the acoustic enclosure. At the same time, the sound intensity measurement is also carried out, and the sound intensity distribution is understood.