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.