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

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.