| The gear pair with intersected axes composed of an involute cylindrical gear and an involute beveloid gear can effectively avoid the interference of tooth side clearance caused by excessive axial displacement and the jam during the transmission.But in practical application,the contact pattern of tooth surface is point contact theoretically which greatly restricts its bearing capacity and result in frequent abrasion of tooth surface,short service life,high vibration and loud noise.In view of above problems,the paper combines the theory of gear meshing,loaded tooth contact analysis and tooth modification,researched the theory of working pitch cone,geometric design method,meshing characteristic and tooth modification optimization of intersected involute cylindrical and beveloid gear pair,so as to improve the bearing capacity of this type of transmission,reducing vibration and noise and improving service life are of great significance.The main contents of this dissertation are shown as follows:(1)The conjugate meshing theory is studied and the working pitch cone model is established for intersected cylindrical and beveloid gear pair;according to the mesh of hypothetical common rack,the formula for the first principle direction angle is derived;considered the restrictive of undercutting,topping and tooth interference in the manufacture and transmission process,the limited condition of profile shift coefficient is studied and the mesh equation without tooth side clearance of the gear pair is derived.From the view of the mesh line,the formula of the contact ratio for this gear pair is derived,the effect of tooth number,helix angle,cone angle and normal pressure angle on contact ratio is analyzed.The results show that the increase of tooth number and helix angle will increase the contact ratio;the increase of normal pressure angle and cone angle will decrease the contact ratio and the smaller axis angle is,the bigger contact ratio will be.(2)Based on the accurate modeling of involute beveloid gear,the finite element contact analysis model for intersected cylindrical and beveloid gear pair is built;mesh characteristics including contact pattern,root bending stress,transmission error and mesh stiffness under specified load condition and different loads conditions are analyzed.The effect of geometric design parameters and installation errors on mesh characteristics are studied.The results show that the helix angle,cone angle,torque load and the axis angle error have great influence on mesh characteristics,the gear axial position error has little influence on mesh characteristics.(3)Considered the tooth modification on flank and profile direction,the mathematical equations of tooth surface with tooth modification is derived,four modification methods are proposed for intersected cylindrical and beveloid gear pair and the effect of different modification methods and modification amounts on contact pattern,root bending stress,transmission error and mesh stiffness is discussed.The results show that the tooth profile modification of cylindrical gear makes the contact pattern shift from toe to heel,the bearing capacity and the partial load is improved better;The contact pattern of profile drum modification on beveloid gear is basically the same as that of the cylindrical gear,showing an increase trend;The combined modification of profile drum modification on beveloid gear and flank slope modification on cylindrical gear can obviously increase the contact pattern area,reduce the stress and transmission error in the meshing process and make the gear pair drive more stable. |
