Impact Analysis of Tolerance and Contact Friction on a RV Reducer using FE Method

Since RV (rotation vector) reducer has a high reduction ratio with compact size, high efficiency and stiffness, the reducer is extensively used in applications requiring high precision in the restricted space like industrial robotic joints. Since the cycloid disk of the RV reducer makes contacts with many pin-rollers simultaneously, tolerance and friction between the cycloid disk and the pin-rollers significantly affect the contact force of the cycloid disks as well as the performance of the RV reducer. This paper presents an impact analysis of tolerance and friction on the RV reducer using FE method. A FE model for a two-disk RV reducer and the eccentric shaft is built considering tolerance and friction between the cycloid disk and the pin-rollers. Then, the FE analysis of an ideal rigid cycloid reducer was performed and verified with the theoretical calculation. The effects of tolerance and friction on multi-contact and the output torque of the RV reducer were investigated. Since the contact forces vary according to both tolerance and friction, the resulting torsional rigidity and output torque are affected considerably. Precisely, the tolerance mainly decreases the torsional rigidity while the friction primarily increases the output torque fluctuation.