打结器割绳脱扣机构磨损分析与改进设计

Wear Research and Improved Design of D-knotter Wiper Mechanism

针对打结器割绳脱扣机构盘形凸轮内轮廓磨损严重的问题,提出以凸轮理论廓面的等距圆弧面代替现有柱面轮廓的解决方案,即将凸面-凸面和凸面-平面的点接触改进为凸面-凹面的弧点接触;计算得到改进后凸轮轮廓的曲面方程,以及改进前后滚子与凸轮的压力角、初始接触面积和初始最大接触应力;最后,用硬铝合金材料试制改进前和改进后的凸轮,进行磨损对比试验,并定量分析其磨损量。结果表明:改进后滚子与凸轮的压力角在推程开始和接近结束阶段比改进前减小25%左右;改进后滚子与凸轮的初始接触面积比改进前增大约50%,初始最大接触应力减小约38%;各运转10 h后,改进后盘形凸轮内轮廓的磨损痕迹宽度比改进前增加31.7%,磨损量减小约50%。

In order to solve the serious wear problem of D-knotter wiper inner cam, firstly, a new structure cam was designed. To be more precise, the original eylinder cam contour was replaced by using the offset arc surfaces of the cam theoretical surfaces, which means the point contact manner of convexity- convexity and convexity-plane was substituted by convexity-concave. Secondly, the surface equations of the improved cam were obtained, and then the pressure angle, initial eontact area, initial maximum contact stress were calculated. Thirdly, the original and improved earns were manufactured by the turning and milling machine, which were using the aluminum alloy materials. Finally, a contrast experiment of wear pattern between the original and improved cams was designed, and the results were given by quantitative analysis. The results indicated that the improved cam mechanism reduced the pressure angle by an average of 25% than the original one in the majority of the rise travel. In contrast to the original one, the improved cam mechanism＇ s initial contact area can increase by approximately 50% and the initial maximum contact pressure decreased by 38%. After 10 hours＇ runs of each earn mechanisms, the improved cam exceeds the original one by 31.7% in case of the width of the wear trace, and the abrasion value of improved cam is about 50% smaller than the original cam.