Development of Prediction Method of Static Torque Sharing Distribution of Planetary Gear Sets Generated by Manufacturing Error Distribution

This paper discusses a method of predicting the torque distribution on planet gears originating in manufacturing errors, which is necessary for appropriate strength design of the gears in planetary gear sets. First, an expression of relation between manufacturing errors and the torque on the planet gears in a normal n-planet planetary gear set was derived. As a result, an equation expressing the distribution of torque to the planet gears was obtained. Tests were conducted to verify the validity of the equation in the case of a 4-planet planetary gear set. In order to predict the distribution of torque, it was necessary to estimate the stiffness of the planetary gear set that was the subject of the relational expression. These stiffness values were calculated by numerical analysis using a 3D FEM, into which blueprint values and material property values were input. The accuracy of the estimated stiffness values was verified by testing, and it was confirmed that the stiffness values could be estimated with a high degree of accuracy. Having confirmed the accuracy of the method of numerical analysis, the method was used to verify the validity of the relational expression for planetary gear sets with five planets or more. Given the above, the distribution of torque to planet gears due to manufacturing errors in a normal n-planet planetary gear set can be estimated with a high degree of accuracy using only computer data.