Preliminary Draft Selection of Geometrical Parameters in Simple Planetary Gear Trains in Automotive Drive Line

The paper deals with the first stage of planetary transmission design and namely the preliminary selection of geometrical parameters in spur and helical gears of simple planetary gear trains. Conditions for correct assembling and spacing planets are considered. There are some conditions to be fulfilled: coaxial location of gears, assembling of gears and spacing of planets. Having known the centre distance modification criterion λ and the condition of coaxial location of gears, the relationships between the numbers of gears: z₁, z₂ and z₃ are given.

As a basic parameter for the planetary gear train the operating pitch diameter d_w3 of the internal gear is assumed. The formula for the operating pitch diameter d_w3 is given according to the calculated torque, contact stress factor k_H, gear ratio u and the relationship of facewidth to centre distance of gear train.