Research On Gear-Rack Meshing Dynamic Performance Of Cog Railway Vehicle

Cog railway vehicles have the advantages of strong climbing ability.In recent years,they have attracted widespread attention in China.For the cog railway vehicle,this thesis analyzes the structural features,running mechanism,the topological relationship of the cog railway vehicle and degree of freedom of vehicle in detail.Considering the factors such as gear and cog railway shape,time-varying meshing stiffness,dynamic transmission error,elastic vibration of wheelsets,support stiffness of cog railway and vertical curve,the rigid-flexible coupling dynamic model of cog railway vehicle was established.Firstly,based on the model,the influences of track irregularity,driving mode,vehicle speed,elastic vibration of wheelsets,traction and braking on gear–rack meshing dynamic performance of cog railway vehicle and dynamic response of wheel–rail interface were analyzed.Secondly,the influence of vehicle,track and gear–rack parameters on meshing dynamics were studied.Finally,the influence of different track conditions such as vertical curve length and track gradient on meshing dynamic performance were further studied,and the matching relationship between track gradient and vertical curve length was given.The main work was as follows:(1)The gear–rack meshing dynamic performance of cog railway vehicle was analyzed.The results show that the meshing stiffness,the gear circumferential force and radial force show obvious periodic characteristics,and the gear radial force would lead to the decrease of wheel–rail vertical force.With the increase of the speed,the meshing force,wheelset vertical vibration acceleration,wheel–rail vertical force and meshing frequency show an increasing trend.The elastic vibration of wheelsets can significantly affect the meshing dynamic response of gear,such as circumferential force and radial force.Different driving modes have obvious influence on the meshing dynamic performance,especially the meshing impact increases significantly in the fixed gear driving mode considering the excitation of track irregularity.In the braking condition,the circumferential force,radial force,wheelset vertical vibration acceleration and wheel–rail vertical force fluctuation amplitude were greater than those obtained in traction condition.(2)The influence of vehicle–track parameters on gear–rack meshing dynamic was analyzed.The results showed that the reasonable value of radial clearance of gear can effectively reduce the meshing impact of gear under wheel–rail excitation.Gear displacement coefficient,gear tooth width and gear pressure angle obviously affected the meshing dynamic performance,but the stiffness of the primary steel spring,the damping of the primary vertical damper,the vertical support stiffness of cog railway and the vertical support damping of cog railway have no significant influence on the meshing dynamic performance.Suitable displacement coefficient and tooth width can effectively improve meshing stability,large pressure angle would deteriorate the meshing performance of gear–rack.(3)The gear–rack meshing dynamic performance under different track parameters was analyzed.The results showed that the amplitude of meshing impact of gear and rack decreases with the increase of vertical curve length,and the longer the vertical curve length,the more stable the meshing.With the increase of track gradient,the dynamic response of gear and rack engagement increases significantly,and the wheel–rail vertical force decreases obviously.The coupling between gear and rack increases with the increase of track gradient.The influence of track gradient and vertical curve length on meshing dynamic performance were comprehensively analyzed.When the track gradient is greater than 150‰,a long vertical curve length(recommended that the vertical curve length be greater than 100 m)should be adopted to avoid large meshing impact and wheel–rail impact.