圆锥滚子定姿态贯穿式超精研凸度形成机理分析

Analysis of Crown Generating Mechanism in Fixed Posture Through-feed Superfinishing of Taper Rollers

圆锥滚子无心贯穿式超精研中,滚子以某种定姿态沿直线贯穿时,在锥面上可以形成一种大致对称的光滑曲线凸度,其凸度形成机理尚未揭示。针对滚子轴线只在贯穿方向铅垂平面倾斜某一固定角度这种定姿态,基于超精研工艺特性及滚子与油石之间的几何和相对运动关系,建立滚子-油石接触线方程和滚子纵向截形方程,推导出各超精研区宽度计算公式。将这种超精研过程看作滚子与油石的接触磨损过程,将凸度看作滚子不均匀磨损的结果,依据磨损基本原理,揭示出凸度形成机理:滚子-油石接触线呈'几'字形,形成8个不同的超精研区,使滚子两端磨损量大于中部;接触线各点的滚子纵向截形倾斜程度存在差异,使滚子磨损深度从两端向中部逐渐非线性减小,从而形成光滑曲线凸度。得出如下结论:只有滚子上素线小端向上倾斜某一适当角度时,才可以形成比较对称的曲线凸度;滚子锥角是基础,其值不为零才能形成凸度;所能形成的最大凸度受锥角大小制约,锥角越大,所能形成的凸度越大。推导出滚子上素线小端向上适当倾斜角度范围的计算公式。

In through-feed centerless superfinishing of tapered rollers, an approximately symmetrical smoothed crown can be generated on the conical surface when the rollers feed through straightly with a fixed posture, but the crown generation mechanism not yet be revealed. For the fixed posture that the roller＇s axial is just inclined at a fixed angle on the through-feed direction vertical plane, based on the characteristics of the superfinishing process as well as the geometric and kinematic relationship between the rollers and the oilstones, equations of the contact line between the roller and the oilstone as well as the longitudinal section profiles of the roller are established, and the formulas for computting the width of every superfinishing region is derived. Regarding this superfinishing process as a roller wear process in contact with the oilstone, and the crown as the result of the nonuniform roller wear, the crown generation mechanism is revealed as follows according to basic wear principle： there are four different superfinishing regions corresponding to the contact line with the pattern of ＂n＂, and they make more wear at end part than the middle part of the roller; there are different inclination between the longitudinal section profiles of the roller, and they make the roller＇s wear depth decrease gradually and nonlinearly from two end point to the middle point of the roller, so the crown is generated. The conclusions are drawn as follows： a symmetrical smoothed crown can be generated only when the roller＇s top generatrix inclines at a proper angle with its small end rising up; the roller＇s taper angle is the basis, and the crown can be generated only when the taper angle is not zero; the biggest crown generated is restricted by the magnitude of the taper angle, and the bigger the taper angle is, the bigger the crown is. The formulas that determine the range of the proper inclination angle of the roller＇s top generatrix are derived.