| Cycloid gear planetary transmission with small tooth difference has several excellent features,such as compact structure,large transmission ratio,more than one tooth meshing at the same time with high transmission precision,strong torsional rigidity and strong load-carrying capacity,so that it is widely used in industrial fields,especially in the field of robot joint reducer and other precision driving fields.Composite cycloid as a special cycloid with a good characteristic of geometry adjustable,and applied in the field of small tooth difference planetary transmission has some advantages.Carrying out the transmission characteristics research of composite cycloid used in small tooth difference planetary transmission can reveal its meshing theory and accelerate the process of its industrial application,which has important theoretical significance and practical value.The main contents of this thesis are as follows:(1)Meshing characteristic analysisFirstly,based on the generation principle of traditional cycloid curve,a transforming method from cycloid curve generation to two-link equivalent mechanism is proposed,and nth-order cycloid motion is concluded using n+1 link mechanism,and the general fourth-order composite cycloid equation for gear driving is derived.Then by using the composite cycloid with good adjustable geometric characteristic as the internal gear tooth profile and on the basis of differential geometry and gear conjugate engagement theory,a meshing equation and a conjugate profile equation of composite cycloid planetary driving with small teeth difference are established,and the line of action,the contact ratio,the mesh boundary as well as the non-undercutting condition are all derived.Lastly the induced normal curvature and the pressure angle are analyzed,as well as the influence of tooth profile adjustment coefficient on the pressure angle is discussed.(2)Load capacity of gear analysisFirstly,analyzed the theory of modification method for composite cycloid planetary gear,and the backlash of gear pair after the profile modification of the composite cycloid planetary gear is deduced,then the location of the point where the first teeth pair get into mesh and the initial gap between those teeth pairs which are not getting into mesh are analysed,after that the force analysis of the composite cycloid gear pair under the condition of meshing theoretically is carried out,including location of contact points,force arms of contact points,contact forces,meshing situation has carried on the force analysis,including the contact position.Lastly,the gear pair torsional rigidity is analysed according to the Hertz elastic contact theory.(3)Dynamic simulation and finite element analysisFirstly,structure design of cycloid planetary reducer with small tooth difference has been carried out,then the multi-rigid-body dynamics simulation model of the reducer is established in ADAMS,and the dynamic simulation is done.Thus the gear ring speed,gear pair contact force,load of planet gear support bearings and any other dynamic characteristics are researched,meanwhile transmission precision and efficiency of the reducer are analysed. |
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