双凸轮连杆型排种施肥无级变速器设计与试验

Design and experiment on double cam-link of continuously variable transmission for seeding and fertilizing

针对目前国产机械式施肥播种机中种肥排量无级调节装置种类较少、电液式种肥排量无级调节装置成本较高,变量播种施肥作业调节范围有限、准确性与均匀性较差等问题,该文提出了一种基于连杆机构与凸轮机构实现无级变速的方法,并设计了相应的双凸轮连杆型无级变速器,它由输出机构、传动机构及调节机构共同实现对输出轴转速的无级调节。运动学仿真分析表明:无级变速器的机构设计合理,凸轮的轮廓曲面质量较高,设计方案可行;性能校验试验表明:随着传动比的变化,输出转速的相对误差值基本在0～10%的范围内波动,占空比值在其理论值附近的波动幅度不超过10%,均满足种肥排量调节的传动比精确性与传动平稳性要求。该研究可为变量施肥播种机的设计提供参考。

In China, there are relatively few types of mechanical, continuously variable transmissions for variable rate seeding and fertilizing, while the electronic hydraulic application has the disadvantages of high cost, limited adjustable range, and poor accuracy and uniformity of distribution. To address these problems, and according to the analysis of the desired variable application rate of adjusting seed and fertilizer, the factors of the manufacturing costs, and the reliability of the structure for medium and small scale size farming operation, this paper put forward a method to achieve the variable speed of a transmission system based on a cam mechanism and connecting lever mechanism, designed the relevant parameters through the above principle mechanism, and developed the double cam link of continuously variable transmissions. The transmission achieved the variable rate of seeding and fertilizing through the simultaneous combined action of the output mechanism, transmission mechanism, and adjusting mechanism. In addition, in order to shorten the development processing cycle, reduce manufacturing cost, and increase the application efficiency, the three-dimensional modeling, simulation analysis, and optimization design were done based on Pro/E platform before the experiment prototype was put into manufacturing. The final analyzed kinematics simulation showed that the mechanisms of a continuously variable application rate transmission were reasonable, the quality of the cam contour curve was high, and the design scheme was feasible. Furthermore, for the purpose of testing the performance of the prototype which was manufactured accurately, a suit testing system that can simulate the actual operating environment of planter in the field was developed to calibrate the variable transmission’s working accuracy and the uniformity of stability. Particularly, the system can perform satisfactorily with the double cam link of a continuously variable desired transmission both qualitatively and quantitatively. After multiple sets of performance calibrations of this experiment and data were analyzed, the results indicated that as transmission ratio changed, the relative error of measured output speed ranged from 0 to 10%, and the fluctuation range near the theoretical value of measured duty cycle was less than 10%, which met the requirement of transmission accuracy and stability. This study can provide some references for the development and design of continuously variable rate applications into small and medium scale agricultural farming machinery based on the above design and tests parameters, and at the same time, it can help to promote the development of exact seed and fertilizer use efficiency in agricultural mechanization operation, especially in China.