Analysis of Transmission Ratio Problem for Planetary Gear Reducer with Two Internal Gear Pairs

Planetary gear reducer with two internal gear pairs is known as NN type reducer. It has the advantage of large transmission ratio. Through the deep comprehensive studies on transmission ratio from four NN type reducers with different structure, the author proposes a new method to analyze transmission ratio from the tooth number difference for both internal gear pairs and external gear pairs, reveals rule, feature and range of transmission ratio of NN type reducer, and provides a clear train of thought for the selection of transmission ratio.