Theoretical And Experimental Research On Integrated Design Of Transmission Components And Bearings Of RV Reducer

RV reducer is a key functional component of an industrial robot,and its performance determines the transmission performance of the entire industrial robot.With the rapid development of the robot industry,the demand for power density of reducer is increasing.The external load of the reducer has become more complicated,which puts forward new requirements on the stiffness and carrying capacity of the reducer.At the same time,domestic RV reducers lack advanced design theories and methods.Compared with foreign products,there is a certain gap in stiffness and carrying capacity.Furthermore,the gap between the fatigue life of the reducer and the foreign products is larger due to insufficient technical performance such as the stiffness and carrying capacity of the reducer.These are the key to restrict the localization of RV reducer in China.Therefore,it is necessary to carry out the structural innovation design and optimization research on the reducer.By improving the stiffness and carrying capacity of the reducer,the fatigue life of the product is further improved.These researches have important theoretical significance and engineering value to promote the localization process of robot reducer in our country.The integrated design of reducer transmission components and bearings is an important trend in the development of RV reducers.Based on the force analysis of the RV reducer based on the coordination of deformation,this paper proposes a method for the fatigue life analysis and optimization of the RV reducer based on the failure of the crankshaft.Based on the force analysis of the RV reducer considering the coordination of deformation,a method of fatigue life analysis and optimization method of the RV reducer is proposed.The fatigue life of the reducer is based on the failure of crankshaft bearing.The integrated design method of RV reducer transmission components and bearings was established,and the rigidity and load-carrying capacity of the integrated structure of the RV reducer were studied,and the prototype was completed and tested.The main research work and results of the thesis are as follows:(1)The structural characteristics and transmission principle of the RV reducer have been analyzed.The tooth contact analysis model(TCA)between cycloidal gear and pin tooth is established.Applying tooth surface contact analysis technology,and according to the force balance and deformation coordination conditions of the cycloidal gear,the(LTCA)model of cycloidal-pin pair is established.Based on the deformation coordination conditions and static balance of each component,the statics equation of the RV reducer is deduced.The load law of the key parts of the reducer is revealed,which provides the basis for the life analysis,integrated design,and optimization research of the reducer.(2)Based on the operating conditions of the RV reducer,the failure modes of key parts are analyzed.The quasi-static equations of crankshaft bearings were deduced and established.The contact stress between roller and raceway was analyzed based on the non-Hertz contacts method.Based on the Lundberg-Palmgren bearing life theory,the life calculation model of the crankshaft bearing considering the roller-raceway contact stress was established.According to the LTCA model,the contact load law of the cycloidal meshing pair was analyzed,and the fatigue life characteristics of the meshing pair were analyzed according to the nominal stress law.The results show that the crankshaft bearing is the weak link of the fatigue failure of the reducer due to the complicated load condition and the structural limitation of the reducer.(3)The integrated design of the cycloidal gear,crankshaft,and crankshaft bearing was carried out.An integrated design of a full complement cylindrical roller bearing structure was proposed.The influences of geometrical parameters and roller crown on fatigue life of bearing are analyzed.The optimization design method of crankshaft bearing is derived.The fatigue life of the crankshaft bearing is taken as the objective function.Parameters such as bearing geometry and roller crown profile are used as optimization variables.The results show that the integrated design of the full complement cylindrical roller bearing has a compact structure,which is beneficial to improve the service life of the reducer;The optimization method reasonably optimizes the design parameters,and the load capacity and service life of the reducer are effectively improved.(4)The integrated design of reducer housing,planet carrier,and main bearing was carried out.A new type of radial-axial bearing is proposed.The static model and stiffness calculation method are established by comprehensively considering the deformation coordination conditions under the combined action of axial load,radial load,and overturning moment.The accurate calculation method of the load-carrying capacity of the main bearing is deduced,and the load distribution and load-carrying capacity characteristics of the main bearing are revealed.According to the movement and geometric relations between the parts,a numerical model of the rotation accuracy of the planet carrier is established,and the influence of geometric errors on the rotation accuracy of the main bearing is analyzed.The results show that the integrated design of the bearing improves the rigidity and load-carrying capacity of the main bearing.The clearance has a significant effect on the performance of the main bearing.The geometric error of the inner raceway has a greater effect on the rotation accuracy of the planet carrier than that of the outer raceway and should be strictly controlled.(5)The prototype of the new type of radial-axial bearing is processed.Stiffness tests were carried out and the results were compared with theoretical analysis.The design and prototype trial production of a new RV reducer integrating transmission components and bearings have been completed.Accelerated fatigue life test was carried out on the prototype,and the transmission error,torsional stiffness and hysteresis,and transmission efficiency experiment of the reducer prototype before and after the life test were carried out.Experiments show that the main bearing has high stiffness and carrying capacity.The integrated design prototype can meet the performance requirements of industrial robots with high precision,long life,and high bearing capacity.The feasibility of the integrated design method of transmission components and bearings of RV reducer is verified.