PLANETARY GEAR

AIM

To select a gear from design library for planetary gear and assemble properly , study the motion analysis using solidworks and

Determine the angular velocity of output in each case

Input output fixed

Case 1 Sun gear carrier ring gear

Case 2 Ring gear carrier sun gear

Case 3 Sun gear ring gear carrier

INTRODUCTION

Planetary gear is also known as a epicyclic gear train and is the one of the important and interesting invention in engineering they are great speed variation mechanism and are often use in automobiles as a vital part of automatic transmission

A planetary gear set have a four main parts The sun gear, planet gear, ring gear and carrier it sometime rotate slowly sometime quickly and some time even in Reverse

when two gear moving they should have same speed at the interface this means the speed of gear “A” is same as a speed of there “B” at the meeting point V(A) =V(B)

The speed has to be same otherwise teeth will be penetrate

EXPLANATION AND THEORY

But how the speed variation is achieved assume

Sun gear(input) carrier(output) ring(fixed)

The ring gear is stationary and the sun gear is rotating but what happens to the planet gear ,the mating between sun and planet should have a certain speed while at a point that mating between ring and planet gear the speed should be zero as a ring gear is stationary .however both this condition is possible at a same time. There is only one ways that planet gear should spin as well as turn the spinning will produce velocities in opposite direction

At these point output velocity achieved that will give low speed

So these turning produces unidirectional velocities

At the top the spinning and turning are in opposite direction so velocity is zero

At the bottom they get added up in short the planet gear forced to turn in order to satisfy the condition of velocities

As the carrier is attached to the planet gear it will turn along with planet gear.

Radius = low

v=r*omega

Here radius is small because contact between planet gear and sun gear is near to axis of center

Ring gear(input) carrier(output) sun(fixed)

Now the sun gear is stationary and ring gear is rotating in these case is totally opposite to the previous case in these case the velocities at point between planetary gear and sun gear have low velocities or zero velocities and velocities will be high at contact between planet gear and ring gear because the radius is more and contact is far away from axis of center

Radius = high

V = r*omega

In these case we achieve high output velocity or speed

Sun gear (input) Ring gear (output) carrier(fixed)

In this case planet gear is not allowed to turn is only spin At one position means the carrier is fixed this spinning opposite to the rotation of the sun gear and ring gear rotate opposite to sun gear that means spinning process is rotation is same as ring gear these will make a reverse process.

OBJECTIVES

How the speed variation occurs in planetary gear train and how to model a planetary gear

CALCULATION

Module is same for all gear

Ring gear

Module = 2.5

Number of teeth = 46

Module = pitch circle diamterno of teeth

Pitch circle diameter = module no of teeth

= 2.5 46 = 115

Pitch circle diameter = 115

Sun gear

Number of teeth = 14

Pitch circle diameter = module no of teeth

= 2.5 14 = 35

Planet gear

As module is same for all the gear

Where planet gear is placed between ring gear and sun gear

Then we can determine

As radius of ring gear is = 57.5

And radius of sun gear is = 17.5

So pitch circle diameter is = 57.5 - 17.5 = 40

RESULTS AND PLOTS

When input is sun gear,carrier is output and ring gear is fixed ,

From the plots representation

Angular velocity of carrier is between 214rad/sec to 285 rad/sec

When input is ring gear ,carrier is output and sun gear fixed

Then according to plot Angular velocity of output : carrier is between 694 rad/sec to 925 rad/sec

When input is sun gear , output is ring gear and carrier is fixed

Then according to plot angular velocity of ring gear is between 288rad/sec to 384 rad/sec

From the plots we can determine when sun gear is input and carrier is output the angular velocity output is low means velocity of planetary gear is low (v = r)

As we know it's mainly used in automobile point of view as vehicle velocity of vehicle is low

In the second plots ring gear is input and carrier is output where angular velocity of output is high so the velocity is also increase

So the speed of vehicle is also increases

In third plots angular velocity gives in between 1st and 2nd plots

But its give a reverse output

So the vehicle can take reverse

Conclusion

When ring gear is fixed and input is sun gear and output is carrier then angular velocity is low

When sun gear is fixed and ring gear is input and carrier is output then angular velocity is high

When carrier is fixed and sun gear is input and ring gear is output then angular velocity is in between means its give reverse output