Planetary Gear

Aim : Motion analysis on the Planetary Gear assembly with a carrier using Solidworks.

Introduction : A planetary gear (also known as epicyclic gear) set is made up of three types of gears – a sun gear , planet gears and a ring gear. The sun gear is located at center and transmit torque to the planet gears which are typically mounted on a moveable carrier. The planet gears orbit around the sun gear and mesh with an outer ring gear.

Planetary gears are often used when space and weight are an issue, but a large amount of speed reduction and torque are needed. This requirement applies to a variety of industries including tractors and construction equipment where a large amount of torque is needed to drive the wheels. Other places you will find planetary gear sets include turbine engines, automatic transmission and even electric screwdrivers.

Calculation :

The module (m) is same for all the gears.

The relationship between pitch circle diameter (D) and number of teeth (t) is –

D=m*t

Ring gear –

m = 2.5 & t = 46

D = m*t = 2.5 * 46 = 115mm

Sun gear –

m = 2.5 & t = 14

D = m*t = 2.5 * 14 = 35mm

Planet gears –

m = 2.5

dia of ring/2 = dia of planet gear + dia of sun gear/2

115/2 = dia of planet gear + 35/2

Dia of planet gear = 40mm

Hence no. of teeth = D/m = 40/2.5 = 16

Type of gear	Pitch diameter	Module	No. of teeth
Sun gear	35mm	2.5	14
Planet gear	40mm	2.5	16
Ring gear	115mm	2.5	46

Procedure :

• First open the solidworks part modeling to make the 3D model of carrier and assemble with sun gear , 4 planet gear and ring gear.
• In design library ( ANSI metric ) we find power transmission and then spur gear and internal spur are taken.
• Then constrains them in such a way that they rotate about there their axis.
• Finally go for the motion analysis and get desired results and plots.

Model :

Pressure angle = 20 degree

Face width = 12mm

Carrier

Assembly

Results :

Case 1 =

Ring gear fixed.

Motor = sun gear

Plot of angular velocity vs. time

Case 2 =

Sun gear fixed.

Motor = ring gear

Plot of angular velocity vs. time

Case 3 =

Carrier is fixed

Motor = sun gear

Plot of angular velocity vs. time

Conclution :

• In case 1 input is given to the sun gear and output is obtained at the carrier keeping the ring gear is fixed.
• In case 2 the input is given to the ring gear and output is obtained from the carrier keeping the sun gear is fixed.
• In case 3 the input is given to the sun gear and a carrier is fixed and the output is obtained from the ring gear.
• Highest angular velocity is obtained case 2.