DESIGN AND MOTION ANALYSIS OF PLANETARY GEAR SYSTEM

INTRODUCTION: An epicyclic 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 epicyclic 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.

OBJECTIVE:

1. To calculate the ‘Pitch Circle Diameter’ and the ‘Number of Teeth’ for the Planet Gear.
2. Performing Motion Analysis of the Planetary Gear System.
3. Obtaining plots of Angular Velocity for different outputs.

SIMULATION CASES:

S. NO	INPUT	OUTPUT	FIXED
CASE 1	Sun Gear	Carrier	Ring Gear
CASE 2	Ring Gear	Carrier	Sun Gear
CASE 3	Sun Gear	Ring Gear	Carrier

GIVEN:

• Ring Gear
  • Module = 2.5
  • Number of Teeth = 46
• Sun Gear
  • Module = 2.5
  • Number of Teeth = 14
• Input Speed of the Gear = 200 rpm.
• Number of Planet Gears = 4

PLANETARY GEAR SPECIFICATIONS:

Module(m) = 2.5

Pitch Circle Diameter = p

No. of Teeth = N

`m=p⁄N`

`p_((R) )=115mm`

`p_((S) )=35mm`

Now, to calculate the pitch circle diameter of the planetary gear,

`p_((R) )/2= p_((S) )/2+ p_((P) )`

`p_((P) )=40mm`

`N_((P) )= 40⁄2.5=16`

PROCEDURE:

• Open the assembly file and upload an internal spur gear from the metric system Design Library. Specify the dimensions and insert the component.

• The Sun Gear is uploaded in the same fashion as the ring gear from the Design Library.

• The uploading process is followed by inserting 4 Planetary Gears and the toolbox dimensions are assigned parallelly.

• The carrier is designed in a separate part file and is inserted into the part file where the gears have already been uploaded from the Design Library. The dimensions of the carrier depend on the shaft diameter of the Planet Gear.

• The Planetary Gear Mechanism for Motion Study is created with proper and adequate number of mates.

ANIMATION: The Link for the animations is mentioned below –

CASE 1

"https://youtu.be/QCuqMFEtmCw"

CASE 2

https://youtu.be/ntkhDT3-ub8

CASE 3

https://youtu.be/Qa2k3ydEKVE

RESULTS:

• CASE 1 –

INPUT

The Angular Velocity remains constant throughout because of the smooth engagement of gears and the transmssion is highly efficient.

OUTPUT

The Angular Velocity at the output, i.e. the Carrier Velocity has sudden peaks due to the variable power transmitted.

• CASE 2 –

INPUT

The above plot depicts constant Angular Velocity of the Input Ring Gear. The initial transmission is usually smooth, but the addition of idler gears make the output variable.

OUTPUT

The plot signifies transmission anomalies that may exist due to out of order contact between the parts interconnected.

• CASE 3 –

INPUT

The sun gear possesses constant input Angular Velocity with minimal variations with the absence of any strange behaviour.

OUTPUT

The output obtained in the form of movement of Ring Gear gives a perception of sudden increments and decrements projected in the result.

LINK TO SOLIDWORKS PART & ASSEMBLY FILES:

"https://drive.google.com/drive/folders/1P33FrZR1XBbe2A-VhpzH-NV54x50hYP7?usp=sharing"

CONCLUSION: The Motion Study provides a clear insight about the functioning of the Planetary Gear System. The cases have been simulated accordingly with the most common being the fixed Ring Gear case. With the variation of the parameters, the output can be varied and thus, optimization is possible.