Research On Static Bearing Capacity Of Inverted Planetary Roller Screw

The inverted planetary roller screw integrated in the disposable electric steering gear is a threaded meshing transmission mechanism that converts the circular drive into linear motion output.It is normal to work under full load,thus its static bearing capacity is one of the important reference indicators.In this paper,theoretical modeling and experimental research on the elastoplastic threads-load distribution and elastoplastic critical load value of the inverted planetary roller screw are carried out to provide theoretical guidance for the design of the static bearing capacity of the inverted planetary roller screw.Firstly,based on the structural characteristics and working principles of the IPRS,the load-bearing,static-load stiffness and contact deformation analysis are carried out,and based on the closed-loop deformation coordination equation of the threads,the elastic threads-load distribution model of the IPRS is studied.Moreover,based on the simplified elastoplastic mechanics model,the plastic deformation of a single thread and its axial equivalent contact stiffness of the IPRS in the plastic deformation stage are derived,thereby,the elastoplastic threads-load distribution mathematical model of the IPRS is established.Secondly,the normal contact stress of the rightmost thread on the roller screw-side reaches the yield limit state of the material as the basis for judging whether the IPRS enters the yield state,the elastoplastic critical load value of a single thread is obtained by the Hertz contact theory and the Mises yield criterion,and taken into the IPRS elastic threads-load distribution model to calculate the elastoplastic critical load value of the entire IPRS.Then,Workbench software is used to perform finite element analysis on the IPRS to verify the correctness of the theoretical model through simulation,and it makes theoretical guidance and preparations for the IPRS static load experiment.Finally,on the basis of the IPRS elastoplastic threads-load distribution model and elastoplastic critical load model,a designed special fixture are used to carry out the IPRS static load experiment on the universal testing machine to analyze the deformation of threads and the static stiffness value of the IPRS thread tooth meshing section,comparing them with the theoretical model and simulation to verify the correctness of the established model.