| Spiral bevel gears are widely used in high-speed and heavy-duty transmission systems which require torque transmission between intersecting shafts or staggered shafts,owing to their high contact ratio,strong bearing capacity and smooth transmission.Gear tooth fatigue fracture caused by excessive dynamic load and tooth surface wear due to lubrication failure are common failure modes of spiral bevel gears.Therefore,in the design stage of gear transmission system,it is particularly important to perform dynamic and elastohydrodynamic lubrication(EHL)anaylsis.However,in the aspect of dynamic analysis,the existing meshing model is not suitable for analyzing the dynamic mesh force of each pair of gear teeth in the multi-tooth meshing zone,and the method of using mesh stiffness to calculate dynamic mesh force has certain limitations since it ignores the nonlinear relationship between mesh force and mesh deformation;in terms of the EHL analysis,since the contact point deviation when the gear pair is loaded is not taken into account,the resu lts of the EHL analysis fail to accurately reflect the lubrication characteristics of the gear at the actual loaded contact position.In response to the above problems,this article carries out the following specific research work.In order to more accurately calculate the dynamic mesh force acting on each pair of teeth in contact of spiral bevel gears,the mesh model of a tooth pair describing the change of the mesh characteristics of each tooth pair during the meshing process is established.The calculation results of the dynamic mesh force of each meshing tooth pair by using the mesh model of a tooth pair and the traditional mesh model of a gear pair are compared,and the superiority of the mesh model of a tooth pair in calculating the dynamic mesh force of each pair of meshing gear teeth is analyzed.The interpolation function of elastic contact force considering the nonlinear relationship between the mesh force and the mesh deformation is used to calculate the dynamic mesh force.This method is compared with the traditional calculation method of dynamic mesh force by using mesh stiffness,and the limitation of the later is analyzed.A method to calculate the geometric and motion parameters of the contacting tooth surfaces at the actual loaded contact point is proposed,so as to provide the necessary input parameters for EHL analysis of spiral bevel gears at the actual loaded contact position.By comparing the results from isothermal Newtonian EHL analysis of spiral bevel gears at the actual and theoretical contact points,the importance of considering the contact point migration caused by the bearing deformation of the gear to accurately analyze the lubrication performance of spiral bevel gears is analyzed.The influence of geometric and kinematic parameters on the lubrication performance of spiral bevel gears is also analyzed,and the main influencing factors are explored.A thermal EHL model considering the actual machined tooth surfaces and the non-Newtonian fluid shear thinning behavior of the lubricant is established.This model can analyze the lubrication characteristics of the gear from the full-film lubrication state to the mixed lubrication state and then to the boundary lubrication state,and calculate the corresponding friction coefficients.At the same time,in order to meet the need of fast calculation of friction coefficient in engineering application,a fast calculation method of friction coefficient of spiral bevel gears is put forward.A tribo-dynamic model of spiral bevel gears considering time-varying mesh characteristics of each meshing tooth pair,tooth flank clearance,transmission error and time-varying sliding friction is developed.The influence of friction on the dynamic characteristics of spiral bevel gears is analyzed.A dynamic test platform for spiral bevel gears is built to measure transmission error,vibration and tooth root stress.A method for estimating the maximum dynamic mesh force by using the measured maximum dynamic root stress is proposed.The test results are compared wi th the analysis results to verify the accuracy of the dynamic model. |
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