基于无函数表达节曲线的非圆齿轮分插机构设计与试验

针对行星轮系分插机构的非圆齿轮节曲线形状复杂、反求时难以用函数对非圆齿轮节曲线拟合的问题,把非圆齿轮的节曲线用数值点形式表示,提出了无函数表达非圆齿轮节曲线的设计方法。应用数值分析方法,对分插机构的秧针进行运动学分析;编写了人机交互设计和优化软件,研究设计变量对秧针运动轨迹和运动姿态的影响,对反求得到的无函数表达节曲线的非圆齿轮系进行检验和修正,完成了对行星架初始安装角等分插机构参数的优化。结果显示:非圆齿轮中心距为40.7 mm,齿轮齿数为19,行星架初始安装角为35°,栽植臂初始安装角为42°,秧针长度为142 mm,取秧角为12°,推秧角为75°为满足农业要求的分插机构的结构参数。秧针相对运动轨迹的高速摄影分析和田间插秧试验说明,求得的旋转式分插机构能够很好地满足插秧要求。该研究结果为高速插秧机核心工作部件的研发提供参考。

Design and experiment of noncircular gears transplanting mechanism based on pitch curve with nonfunction expression

Abstract: Design documents about non-circular gears were firstly given with pitch curve functions of gears, and then tooth profiles of non-circular gears were designed according to the design principle of the gear. Because of complicated pitch curve of non-circular gear, in the reverse design process of non-circular gear's transplanting mechanism, it was difficult to use the function to cover some of the details of non-circular gear pitch curve, which made the study of rotary transplanting mechanism with non-circular gears be carried on, only if a kind of curve function was given. It influenced further study of non-circular gear transplanting mechanism. Aiming at the problem that it was difficult to determine the non-circular gear pitch curve when reversing, this paper studied non-circular gear pitch curve in the expression of numerical points form, and put forward a method of non-circular gear pitch curve in the expression of non-function. The phenomenon of concave or nonsmooth connection in the first joint curve would often appear when the tooth top data of surveying and mapping was fit. So curve correction was needed. It was difficult to find a new suitable function to fit the corrected tooth top data because the original fitting function of addendum curve was not used for the corrected tooth top data. Therefore, this paper proposed a method that the corrected tooth top curve was expressed by the data of addendum circle's numerical point. The method overcame the limitation of designing non-circular gears transplanting mechanism when the function of pitch curve was given, and it also avoided the problem that it was difficult to find a new suitable function to fit the corrected tooth top data. Numerical point data of non-circular gear pitch curve was obtained by moving the addendum circle an addendum distance to rotation center. Then non-circular gear pitch curve with non-function expression was obtained, which made the design of the non-circular gear more flexible. Using numerical analysis method, the method of solving the seedling needle trajectory was studied, when non-circular gear pitch curve was in the expression of non-function. The kinematics analysis of transplanting mechanism was carried out. Using the design method of human-computer interaction, a software of optimization design of transplanting mechanism was written, to which that seedling needle trajectory met the planting requirements was the optimization target. The software of visualizing characteristics of mechanism motion was used to optimize the structure, and a group of structural parameters which met the agronomic requirements were obtained. The prototype of transplanting mechanism was manufactured based on the optimized structural parameters. The seedling needle tip point's relative trajectories obtained from high-speed camera and theory study were the same, which indicated that manufactured transplanting mechanism met the requirement of actual testing. According to the field planting experiment, manufactured transplanting mechanism has good seedling upright degree, high precision of fetching seedlings, less seedling injury and also satisfies the requirement of machine planting. The field planting experiment also proves the correctness of reversing of non-circular gears transplanting mechanism based on non-function expression of non-circular gears pitch curve. The research results provided the reference for the research and development of core working parts of high speed transplanter.