Research On Superfinishing Modification Of Tapered Roller Crowing

Rolling bearing is an kind of important and basic part of machinery, and taperedroller is an kind of important rolling element of bearing. Tapered Roller crownmodification is to modify the roller straight generatrix to a curve, the curve is slightlyprotruding to the outside entity, it can avoid or mitigate the edge stress concentrationbetween straight generatrix roller and raceway, and make the contact stress distributiontends be uniform, thereby it can increase the carrying capacity, life and reliability of thebearing. Through-feed superfinishing is an important processes of tapered roller crownmodification, in this paper, it is taken as research object of crown modification, the maincontents and conclusions drawn are as follows.(1) The tapered roller bearings and other parts superfinishing process and generalsuperfinishing are compared and analyzed, it points out the special nature of this kind ofsuperfinishing process. In the general superfinishing that plunge superfinishing ofcylindrical surface as the representative, it is presented “surface contact” state betweenstone and workpiece surface; in the bearing parts superfinishing, such as tapered rollerthrough-feed superfinishing and the current channel of deep groove ball bearing ringssuperfinishing process, depending on their specific processing method, it is showing“non-surface contact” state between stone and workpiece surface, this process becomesa special kind of process.(2) By analysis of the characteristics of the superfinishing process as well as thegeometric and kinematic relationship between the rollers and the stones, equations ofthe contact line between the roller and the stone as well as the longitudinal sectionprofiles of the roller are established; based on the features of the contact line shape todivide superfinishing area, and the formulas for computing the width of everysuperfinishing region is derived. Regarding this superfinishing process as a roller wearprocess in contact with the stone, and the crown as the result of the non-uniform rollerwear, the crown generation mechanism is revealed as follows according to basic wear principle: there are four different superfinishing regions corresponding to the contactline with the pattern of “π”, and they make more wear at end part than the middle part ofthe roller; there are different inclination between the longitudinal section profiles of theroller, and they make the roller’s wear depth decrease gradually and nonlinearly fromtwo end point to the middle point of the roller, so the crown is generated.(3) Analyzed the influence of top generatrix inclination angle of the roller, halfroller cone angle and other factors on crown, the results show that, a symmetricalsmoothed crown can be generated only when the roller’s top generatrix inclines at aproper angle with its small end rising up; the roller’s taper angle is the basis, and thecrown can be generated only when the taper angle is not zero; the biggest crowngenerated is restricted by the magnitude of the taper angle, and the bigger the taperangle is, the bigger the crown is. The formulas that determine the range of the properinclination angle of the roller’s top generatrix are derived.(4) Test of fixed posture through-feed superfinishing indicates that selected areasonable inclination angle of top generatrix inclination angle of the roller within agiven range in this paper analysis, we can get a better symmetry smooth curve crown.