| dc.description.abstract | The cycloid planetary gear drives, so-called RV-drives in the industries, consist of a cycloid planetary gear stage and an involute planetary gear stage. Due to the short tooth depth of cycloid profile, a small tooth number difference can be achieved for application with a high reduction ratio and multiple tooth pairs in contact. With these features the cycloid planetary gear drives can have higher durability, higher shock absorbability and higher power density than the conventional involute planetary gear drives. On the other hand, the multiple contact tooth pairs can also provide lower backlashes, which make precision transmission possible. Because of the above features the cycloid planetary gear drives are widely applied in the conditions with heavy load, shock or high precision, for example, automatic machinery, civil machinery, as well as yaw and pitch system of wind turbines. However, the analysis of the split torques among the crankshafts and the two cycloid disks as well as the shared loads among the contact tooth pairs becomes difficult, because of multiple tooth pairs in contact and power split. On the other hand, the cycloid disks move eccentrically and the bearing stiffness can not be ignored. The dynamic loading conditions are influenced additionally by centrifugal and inertia effect and the bearing stiffness with comparison of static analysis. The power distribution and the load sharing of tooth pairs in cycloid planetary gear drives are the essential research topics.
The purpose of this thesis is to establish a dynamic analysis model by using software Adams for load analysis of the cycloid planetary gear drives. In the study the meshing stiffness of the contact tooth pairs is at first determined by using FEM. The analysis result of load sharing of contact tooth pairs with the obtained stiffness parameters has a good agreement with a loaded tooth contact analysis (LTCA) approach. This method is obviously reliable. The analysis model is therefore established with aid of this approach, and the bearing stiffness is considered in the model. The study cases in the thesis for dynamic load analysis include two different reducers, each having the pin-wheel or the carrier as the output component. The tooth modification of the two cases are different due to different application conditions. The boundary conditions for dynamic load analysis include quasi-static, various constant speeds, and variable speed conditions. The analysis items in the thesis are the transmission error with/without eccentric error of cycloid disks, shared loads in cycloid and involute tooth pairs, variation of bearing loads for supporting the cycloid disks, and the distribution of the torques to the crankshafts and cycloid disks.
The results show that different kinds of tooth modification cause different variations in tooth contact force. The nonlinear bearing stiffness will cause also unevenly shared torques between crankshafts and cycloid disks. The variation of the unevenly shared torques among the three crankshafts is about 13%, and 1% between the two cycloid disks. The dynamic conditions affect also the tooth contact forces, not only in the trend and but also the maximum value of the shared forces. As the speed increases, the end of tooth contact occurs earlier, and the maximum value of the shared loads also increase, for example, the maximum value in the condition of the output speed 30 rpm is 1.5 times as much as that in the quasi-static condition.
The analysis results show that the computer-aided analysis approach proposed in this study can effectively analyze the varaition of dynamic loads in the cycloidal planetary gear deives due to the bearing stiffness and the rotational speed.
Keywords：Cycloid planetary gear drives, Dynamic load analysis, Multiple tooth contact, Adams | en_US |