Nonlinear Dynamic Analysis Of Planetary Reverse Mechanism For Metal V-belt Continuous Variable Transmission

Planetary gear transmission system has the advantages of compact structure,high transmission efficiency, widely used in automobile, aviation, marine, windpower and other fields. But the system has complex vibration problems, causedexcessive noise and dynamic load, such as certain helicopter cabin noise caused byplanetary systems is up to100dB, seriously harm to the reliability of transmissionsystem. Research point out, planetary gear transmission system is a typicalself-excited vibration system, Internal incentive mainly are time-varying meshstiffness, gear error, synthetic mesh shock and so on. In addition, due to gearengaging and impact load problems caused by backlash, planetary gear transmissionsystem has serous nonlinear character, such as bifurcation and chaos. So thevibration character is research key point of planetary gear transmission systemnonlinear dynamic problem.In the transmission system of Metal Belt CVT, planetary reverse mechanism isone of the key parts. Through the multi-plate clutch locking control, this planetarygear system can realize the reverse starting and running. As in the starting andrunning process, the rotational speed and torque of the planetary reverse mechanismis timely variable. Therefore, the planetary reverse mechanism not only bear theinternal excitation, but also the external excitation at the same time. Furthermore,the rotational speed of external incentives will affect the internal excitation, such asthe time-varying meshing stiffness, comprehensive meshing error and so on. In otherwords, the Internal and external excitation are in the coupling state, not simplylinear superposition, and this will directly make it more difficult to analysis the faultof planetary gear transmission system.In consideration of that, planetary reverse mechanism of domestic prototype hasbeen failed in fatigue test in the process of localization. Vibration, noise, toothfracture failure occurred during the test, which seriously weakened life cycle andreliability of domestic CVT product. Considering time-varying meshing stiffness, acomprehensive meshing error, tooth side clearance and other factors, this paperestablished the planetary reverse mechanism of nonlinear coupled differentialequations of motion based on the theory of gear system dynamics. Solve the equationby the variable step size4-5order Runge-Kutta algorithm, and analysis the system infrequency domain and time domain. Finally, according to the simulation results, draw the system bifurcation diagram, and combined with the load diagram, phasediagram, Poincare section and FFT spectrum in typical operating condition,systematic analyze the response evolution process of the system with internal andexternal parameter excitation. In addition, considering the planetary reversemechanism may approach chaotic state, we bring in the chaotic time series analysistheory, and calculate the largest Lyapunov exponent to judge whether the system isin a chaotic state.Finally, through the gear side clearance as the breakthrough point, carry outimproved performance test to the planetary reverse mechanism, and to verify theresult of theoretical analysis. Test results show that, if gear side clearance is toolarge, noise is serious and tooth fracture failure will happen frequently. Reducinggear side clearance can effectively reduce the vibration of the system. However,keep reasonable gear side clearance is not only convenient for installation andlubrication of gear, but also appear to planetary carrier floating design for load share,which can prevent breaking tooth failure due to uneven load.