| With the improving requirement of the accuracy,backlash and service life,the worm drive is developing to the direction of high accuracy,high efficiency,high load carrying capability and zero backlash.As a new type of worm drive,the single roller enveloping hourglass worm drive(SREHWD)has the advantages of high bearing capacity,high transmission efficiency and long service life due to its large number of meshing teeth and small friction coefficient.Moreover,the hourglass worm gear surface can be reasonably pre-loaded to achieve zero backlash,so it has a wide application prospect in the related field such as precision indexing mechanism.This thesis study on the single roller enveloping hourglass worm.The theoretical analysis,numerical calculation,and experimental verification are used to solve the key problems of zero-backlash meshing process under the multiple design parameters,assembly error and sectional modification.It provides a theoretical basis for transmission accuracy improvement and return difference control in the engineering application of this kind of worm drive.The main work of this paper are as follows:(1)Based on the differential geometry and gear meshing principle,the meshing geometry model was established combined with the structural characteristics and operation mechanism of single roller enveloping worm drive.Then meshing equation and the tooth surface equation of SREHWD was obtained.The mathematics of macro and micro meshing performance such as contact line distribution,boundary curve,lubrication angle and induced normal curvature was formed.The influence of the geometrical parameters on the meshing performance was analyzed.(2)Based on the theoretical meshing geometry model of this transmission pair,the new geometry model of SREHWD which considering center distance error,worm axial error,worm axial error and shaft intersection angle error was established.The contact interference areas of the transmission pair under the error state were analyzed and then the interference areas were proposed as the evaluation index of the interference quality.The interference area was solved by numerical method.And then the influence law of each error component on the interference was obtained.(3)By means of the method of preloading the tooth surfaces on both sides at the same time,the zero-backlash meshing was realized through the sectional modification control of the tooth surfaces of the hourglass worm.Through deducing the transformation model from theoretical tooth surface to modified tooth surface,the modification parameters and correlation rules of each part were analyzed.After that,the logarithm curve trimming and secondary chamfering trimming of the gear tooth surface was carried out to improve stress distribution stress.In order to verify the effectiveness of the modification of the tooth surface is verified with no backlash,3D solid modeling and finite element comparative analysis model was established before and after the modification.(4)Based on the principle of virtual turning center grinding and the envelope generating process of SREHWD,the linkage relationship between workpiece and grinder in high precision grinding of hourglass worm tooth surface was analyzed.Then the hourglass worm sample with the characteristics of modification was developed.This thesis defined the topological network error of hourglass worm tooth surface,then the error measuring method was put forward.Furtherly,the processing flow of error data points was established.At last,the surface error of a sample hourglass worm was measured.It provides theoretical guidance for the high-precision machining and measuring of the tooth surface of SREHWD. |
