Dynamic characteristics of the ring gear structure of two-stage plastic planetary reducers

With the emergence of various high-performance engineering plastics, the industrial application of plastic gears has increased considerably. Based on the conventional integrated structure of the first- and second-stage ring gears of the planetary reducer, this study proposes a novel split structure of the first- and second-stage ring gears of the planetary reducer. Dynamic simulation, noise test, and dynamic stability tests of the planetary systems, including split and all-in-one ring gears, were performed to determine the dynamic characteristics of the overall system by using rigid body dynamics theory. The dynamic characteristics of the system were analysed and compared theoretically and experimentally. The results revealed that the dynamic characteristics of the planetary gear train are strongly affected by the ring gear structure. Under similar working conditions and simulation environment, the transmission error of the all-in-one-type model fluctuated more rigorously than that of the split-type model, and the angular acceleration and contact force errors of each component of the all-in-one-type model were larger than those of the split-type model. A high-order second-order meshing frequency appeared in the frequency-domain diagram of the first-level planet carrier of the all-in-one-type model, indicating that the vibration has been transmitted, whereas the frequency-domain diagram of the second-level planet carrier exhibited low-frequency components. Correspondingly, the high-order frequency amplitude of the split-type model was smaller than that of the all-in-one-type model, and the model exhibited no low-frequency component. The analysis results of the contact force spectrum between the first- and second-stage planet gears and the ring gear of the two models are consistent with the analysis results of the frequency-domain diagram of the planet carrier, indicating that the split-type model is more stable in overall transmission. The all-in-one-type model transmits a large amount of vibration to the primary system through the all-in-one-type ring gear, causing the system to have a positive feedback effect, which results in its unsteady transmission. Noise and current stability experiments revealed that the noise and current fluctuations of the all-in-one-type model are larger than those of the split-type model, verifying that the transmission in the all-in-one-type model is not stable.