The Modeling And Dynamic Characteristic Analysis Of Recirculating Ball Variable Ratio Steering Gear

Steering gear is the key parts in automobile steering system, which plays an vital role in auto safety driving. Vehicle steering system performance are different under different conditions of requirements. Vehicle needs smaller ratio to get more heavy steering wheel in order to guarantee the stability at high speed during the straight driving; When the vehicle is turning a corner, it need larger transmission ratio make the vehicle has a high handiness and mobility. The presence of the variable ratio steering system solves this problem, which can solve the contradiction between handiness and sensitivity to some extent.This paper puts forward the complete design idea from modeling to finite element analysis and optimization based on the recirculating ball type steering gears as the research object. According to the variable transmission ratio curve, conform the variable ratio gear pair tooth in the movement relationship; Based on envelope principle, established the variable ratio gear pair of 3d model by the simulation of generating method; Through theoretical analysis, established of steering trapezium of the mechanical model and motion model; Combining with the actual loading conditions, analyzed the variable ratio gear pair meshing movement process with dynamic finite element analysis, and study the dynamic characteristics of the meshing process; Based on dynamic characteristic of the variable ratio gear pair study, this paper proposes a method of tooth profile fitting optimization.The paper main work is as follows.(1) According to the variable transmission ratio curve, simulated the generating cutting of gear machining process and established variable ratio gear pair of 3d model through secondary development of CATIA.(2) Based on the theory of mechanics, studied steering trapezium of the mechanical model and motion model of recirculating ball type steering system; Analyzed the steering resistance moment of the actual working conditions which is used as the applied load of finite element analysis.(3) Through theoretical calculation, established the mechanical model of variable ratio gear pair and analyzed the mechanical characteristics and kinetic characteristics of the variable ratio gear pair meshing process, and compared with the results of finite element analysis.(4) Based on the transient analysis of the variable ratio gear pair, the dynamic characteristics of the variable ratio gear pair during the meshing process were studied. Analyzed the mechanics characteristics(the distribution and regulation of meshing force, contact stress and tooth root bending stress) and kinetic characteristics(the regulation of transmission error, velocity and acceleration).(5) Based on the dynamic characteristics of the valuable ratio gear pair, taking contact stress, tooth root bending stress, dynamic transmission error as the optimization objection, optimized the profile design which can put forward a thought for the optimization design of the gear.This paper puts forward a complete design progress of the recirculating ball style variable ratio steering gears from generating cutting modeling to the dynamic characteristics based on the finite element analysis and the tooth profile fitting optimization, which is of great significance to the research of variable ratio steering gear and has practical significance to the development of the steering gear.