Study On Meshing Principles Of Pure-Rolling Cycloid-Like Gear Drive

Cycloid pin-wheel reducer has advantages of large reduction ratio range, high transmission efficiency, large coincidence and compact structure. Due to these advantages, cycloid pin-wheel reducer has been applied in various fields like petroleum, chemical and defense industries. RV reducer and FA cycloid pin-wheel reducer which are improved from basic cycloid pin-wheel reducer are occupied most of the market share in precision transmission fields like industrial robots, aerospace and large telescopes. However, there are some disadvantages in cycloid pin-wheel reducer. The arm bearing is the weak link due to the high relative speed and large stress during long working-time. Usually the output mechanism is a cantilever structure which will results in the fatigue fracture due to the large load torque. Bearings cannot be applied to the pin-wheels due to the small radius of pin-wheels if the reducer has a large reduction ratio, therefor sliding friction is increased and transmission efficiency is reduced.A new structure reducer is proposed after analyzing the structure features and operating principles of common cycloid pin-wheel reducers. This struc-ture contains two transmission types, one is dual cycloid-like pin-wheel trans-mission, and the other is small teeth difference coplanar dual internal meshing transmission. Structure characteristics and transmission principle of each trans-mission type are described, three-dimensional principle models are established. The feasibility and effectiveness are verified through kinematics and dynamics analysis and prototype testing.Pure-rolling cycloid-like pin-wheel reducer is proposed. On the problem of the pin-wheels’ sliding friction in cycloid pin-wheel reducer, a new type of tooth profile—cycloid-like profile—is proposed based on the conditions of arc lengths equivalence of each tooth of epicycloid and hypocycloid gear and the two contact points of every pin-wheel are instantaneous center of each meshing component. By comparing several commonly used methods of superposition of small teeth, convert-tooth shape method is chosen to superimposing small involute teeth to the cycloid-like profile. The feasibility and effectiveness are verified through kinematics analysis and prototype testing.Small teeth difference coplanar dual internal meshing transmission is pro-posed. On the problem of the arm bearing and output mechanism failure in the case of heavy load in cycloid pin-wheel reducer, a new type of transmission—small teeth difference coplanar dual internal meshing transmission—is pro-posed after analyzing the structural features of RV reducer, three-ring reducer and internal translation reducer. In this transmission, two small teeth difference internal meshing gears are coplanar with each other, one is external and another is internal. The force on bearing is about1/5～1/4of the load force accord-ing to the results of kinetostatics analysis. Two parameter design procedures are given according to the structure characteristics. A principle model is estab-lished, the force analysis of the key components and the gears’fatigue strengths are calculated. The feasibility and effectiveness are verified through prototype testing.A new type of transmission is obtained by combined the two type of trans-missions above. It has advantages of pin-wheel pure-rolling, small bearing force, small axial size and no W output mechanism. It is a new type of reducer for industrial robots and has a value of deep study.