Page 193 - Mechatronics with Experiments

MECHANISMS FOR MOTION TRANSMISSION 179

4
Ring gear
N
3 4
Planetary gear
1
Sun gear
N
2 3
N 1
Carrier

Symbol

P
R
C

(a) S
N 3
N 1 3 N 4
1 4
2

(b)
FIGURE 3.25: Planetary gears: (a) ring gear is an internal gear, (b) ring gear is an external gear.

gears are also called epicyclic gears. There are four main components of a planetary
gear:
1. sun gear,
2. carrier (also called planetary carrier or arm),
3. planetary gear,
4. ring gear.
There are five possible conditions of planetary gear applications (Figure 3.26): in four of
the conditions one of the components is fixed.
1. Sun gear is fixed, (w = 0.0): ring gear, planetary gear, and planetary carrier all
1
rotate in the same direction. This is called the walking planetary gear condition
(Figure 3.26a).