dc.description.abstract | Planetary gear drives have the advantages of high power-weight ratio, large gear ratio, as well as smooth transmission with high efficiency. They are often widely applied in mechanical power transmission system, such as vehicles, ship machinery, production machinery, and wind turbines. However, in the practice, the load sharing among the planets will be not even due to the presentence of manufacturing and assembling errors. It means the planetary gear set can’t provide power transmission with a larger torque even by increasing the number of planetary gears. In order to solve the problem, many load balancing mechanisms are applied to meet the requirement of even load sharing by using flexible elements or floating gears to have more degrees of freedom. One of the well-known methods for the planetary gear drives is the design with flexible pins, i.e. the planet gears are flexibly supported.
The aim of this study is to analyze the static load sharing and load distribution in planetary gear sets with a floating planet gear in the presentence of manufacturing and assembly errors. The geometrical relation between the manufacturing errors and the gaps of the engaged teeth among the gears of the planetary gear drives is at first analyzed. Based the influence coefficient method, a numerical method of loaded tooth contact analysis for planetary gear sets in the case of multiple gear-pairs and multiple tooth-pairs is also developed to analyze the load sharing among the planet gears and the load distribution on the engaged tooth flanks., The loading in the planetary gear sets with flexible supported planet gears is further analyzed by using the developed LTCA method and the conditions of load equilibrium of the planets and the relation of the tooth gaps due to the position change of the planets. The unknowns can be thus solved, including the balanced positions of the planets, the contact stresses distribution on the flanks and also the load sharing among the planet gears.
In order to verify the feasibility of this theory, the analyzed results for the planetary gear sets with manufacturing and assembly errors are also compared with the finite element method under consideration of the planetary gear sets with rigidly or flexibly supported planets. Both the calculated results are in good agreement. The influences of the number of the planets, the stiffness of the planet supporting, and the transmitted torque on the load sharing are also discussed.
The analysis of the load sharing in planetary gear set under consideration of the influences of various types of errors and design parameters shows that with different planet number the tangential pinhole position error, tooth thickness error and the radial pinhole position error all can influence the load sharing of planet gears. Which the pinhole position error is the critical influence tolerance, the tooth thickness error is the second and the radial pinhole position error has little effect. In case of floating planet gears design, the even load sharing among planets can be achieved. In the comparison of design parameters, the smaller planet flex-pin stiffness the more even load sharing and increased input torque can reduce the uneven load sharing.
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