T-115
Fig. 13-3 Single-Stage Gear Train with an Idler
13.3 Planetary Gear System
The basic form of a planetary gear system is shown in Figure 13-4. It consists of a
sun gear A, planet gears B, internal gear C and carrier D. The input and output axes of a
planetary gear system are on a same line. Usually, it uses two or more planet gears to
balance the load evenly. It is compact in space, but complex in structure. Planetary gear
systems need a high-quality manufacturing process. The load division between planet
gears, the interference of the internal gear, the balance and vibration of the rotating
carrier, and the hazard of jamming, etc. are inherent problems to be solved.
Figure 13-4 is a so called 2K-H type planetary gear system. The sun gear, internal
gear, and the carrier have a common axis.
Fig. 13-4 An Example of a Planetary Gear System
Gear 3
(z3, n3)
Gear 2
(z2 , n2)
Gear 1
(z1, n1)
Sun
za =
D
Internal Gear C zc = 48
Planet Gear B zb = 16
