Planetary Gear

AIM:- TO RUN THE MOTION ANALYSIS ON THE PLANETARY GEAR ASSEMBLY WITH FOUR PLANET GEAR AND CARRIER BY USING SOLIDWORK

INTRODUCTION

An epicycle gear train (also known as planetary gear) consists of two gears mounted so that the centre of one gear revolves around the centre of the other. A carrier connects the centres of the two gears and rotates to carry one gear, called the planet gear or planet pinion, around the other, called the sun gear or sun wheel. The planet and sun gears mesh so that their pitch circles roll without slip. A point on the pitch circle of the planet gear traces an epicycloid curve. In this simplified case, the sun gear is fixed and the planetary gear(s) roll around the sun gear.

An epicycle gear train can be assembled so the planet gear rolls on the inside of the pitch circle of a fixed, outer gear ring, or ring gear, sometimes called an annular gear. In this case, the curve traced by a point on the pitch circle of the planet is a hypocycloid.

The combination of epicycle gear trains with a planet engaging both a sun gear and a ring gear is called a planetary gear train. In this case, the ring gear is usually fixed and the sun gear is driven.

PROBLEM STATEMENT

Use the following inputs for designing the Planetary Gear

• Ring Gear

• Module = 2.5 (You must use the metric system in design modeler)
• Number of teeth = 46

• Sun Gear

• Number of teeth = 14

• Input Speed of the Gear = 200 rpm.
• Number of planet gears = 4

The dimensions of the carrier depend on the shaft diameter of the planet gear.

With the above input parameters, you are going to run a simulation on the following cases,

Sl.No	Input	Output	Fixed
1	Sun Gear	Carrier	Ring Gear
2	Ring Gear	Carrier	Sun Gear
3	Sun Gear	Ring Gear	Carrier

Calculation of Pitch circle diameter and no of teeth in planet gear

Given data

Module of all gear is same m = 2.5

No of teeth of Ring gear, T_R = 46

No of teeth of Sun gear, T_S = 14

We know, m = D/T

D = m*T

Diameter of ring gear D_R = m* T_R

D_R = 2.5*46 = 115 mm

Similarly,

Diameter of sun gear D_S = m* T_S

D_S = 2.5*14 = 35 mm

By geometry, D_R = D_S + 2D_P

D_P = (D_R - D_S )/2

D_P = ( 115 – 35 )/2 = 40 mm

No of teeth of planet gear, T_P = D_P/m

T_P = 40/2.5 = 16

Creating 3D model of gears and carrier

For creating gear from toolbox of Solidworks

Go to design library – Toolbox – ANSI metric – Power transmission – gears

For sun gear choose spur gear

Enter module = 2.5

No of teeth = 14

Pressure angle = 20

Face width = 12 mm

For Planet gear choose spur gear

Enter module = 2.5

No of teeth = 16

Pressure angle = 20

Face width = 12 mm

For Ring gear choose internal spur gear

Enter module = 2.5

No of teeth = 46

Pressure angle = 20

Face width = 12 mm

Outside diameter = 135 mm

Dimension of carrier depends on geometry of gear

Motion analysis

Case-1

Sl.No	Input	Output	Fixed
1	Sun Gear	Carrier	Ring Gear

Input speed = 200 rpm

Assembly

Generating plot of angular velocity of output (carrier)

Excel plot

Case-2

Sl.No	Input	Output	Fixed
2	Ring Gear	Carrier	Sun Gear

Input speed = 200 rpm

Assembly

Generating plot of angular velocity of output (carrier)

Excel plot

Case-3

Sl.No	Input	Output	Fixed
3	Sun Gear	Ring Gear	Carrier

Input speed = 200 rpm

Assembly

Generating plot of angular velocity of output (Ring Gear)

Excel plot

COCLUSON

1. Case-1 – When the input is given to the sun gear and output is obtained at the carrier keeping the ring gear fixed, the planet not only rotate about axis but are also forced to roll on the inside of the ring gear since it is fixed. This results in low speed and high torque transmitting capacity.
2. Case-2 – When the input is given to the ring gear and output is obtained from the carrier keeping sun gear fixed, the angular velocity achieved is maximum since the ring gear is quite big and planets gears are small, so when large gear meshes with a small gear the velocity achieved from the small gear is very much because the velocity ratio is very high. It is shown in plot of angular velocity.
3. case-3 – When carrier is fixed and output is to be obtained from the ring gear the opposite happens, the planet gears rotate only about their axis and transmit motion from sun to the ring and since the ring gear is big in diameter the angular velocity achieved is less.

Links for parts, assembly and excel sheet

https://drive.google.com/drive/folders/1jezTqCmHsEDFbmiYe67zGCxDy161iK5M?usp=sharing

link for case-1 animation video

link for case-2 animation video

link for case-3 animation video

Reference

https://en.wikipedia.org/wiki/Epicyclic_gearing