Planetary Gear

Aim

The objective of this task is to perform motion analysis on planetary gear by constraining various parts of the assembly and studying the angular velocities of each.

Introduction

To study and understand the mechanisms, understanding the mere basics and concepts would help us understand it better.

What are gears?

Gears are parts of rotating machinery having cut teeth. They are used for transmitting torque from one part of a machine to another. Geared devices can change the speed, torque, and direction of a power source.

What are some of the applications of the gears?

Gears are almost used in everyplace where there is a motion or movement required. It varies based on the size, material being used, Application it’s being used in and many more. They can be found starting right from the mechanical watches to Complex operations in ISS.

What is planetary gear arrangement and what are its applications

Planetary gearboxes have become extremely important in many areas of mechanical engineering. These are arrangement of the gears placed similar to the solar system. Where the sun gear takes the center position and planetary gears rotate around the sun. Both the sun gear and planetary gear lie within the orbit of the ring gear with internal teeth.

Applications of Planetary gear mechanism

• Tractors and construction equipment
• Turbine engines
• Automatic transmissions
• Electric screwdrivers

Advantages of planetary gear mechanism

• High efficiency
• Compact size
• Low backlash
• Less resistant to damages
• High torque-weight ratio
• Even load distribution

Design and parts

There are 4 key components in this set up

1. Ring Gear

The housing with integrated internal teeth is known as a ring gear.

Parameters:-

• Module:2.5
• Number of Teeth: 46
• Pressure angle:20
• Facewidth:15
• Pitch Circle diameter:- No. of teeth x module:46x2.5=115
• No of gears: 1

2. Sun Gear

The sun pinion is usually attached to a clamping system in order to provide the mechanical connection to the motor shaft

Parameters:-

• Module:2.5
• Number of Teeth: 14
• Pressure angle:20
• Facewidth:15
• Nominal Shaft dia:10
• Pitch Circle diameter:- No. of teeth x module:14x2.5=35
• No of gears: 1

3. Planetary Gears

Planetary gears, which are mounted on a planetary carrier, roll between the sun pinion and the ring gear.

Parameters:-

• Module:2.5
• Number of Teeth: 16
• Pressure angle:20
• Facewidth:15
• Nominal Shaft dia: 20
• Pitch Circle diameter:- No. of teeth x module:14x2.5=40
• No of gears: 4

4. Planetary Carrier

The planetary carrier also represents the output shaft of the gearbox. The sole purpose of the planetary gears is to transfer the required torque. Dimensions here are bases on the nominal shaft diameter for planetary geras

Working process

There are basically 5 basic ground laws for motion of single planetary gear sets.

1. Single Input single Output and no reactionary force.

In this case the motion is neutral and there won’t be any kind of motion.

2. Planetary Carrier is the output

Here the initial motion starts. So the gear reduction mechanism takes place here. It is employed when higher operating torques are required, at the expense of loss of speed. This is often used when the vehicle is initially starting.

3. Planetary Carrier is the input

Here the overdrive mechanism takes place. Overdrive is the operation of an automobile cruising at sustained speed with reduced engine revolutions per minute and better fuel consumption.

4. Planetary Carrier is the reactionary

Here the reverse mechanism is employed, where the direction of the drive changes.

5. Two Members of the mechanism are locked.

Here the direct drive mechanism takes place. A direct drive mechanism is one that uses the torque coming from a motor without any reductions

Based on the place and situation of application the rules are applied to get the motion

Methodology of analysis

To perform the motion analysis and study how the mechanism works, a few situations are taken and studied.

• In the 1^st motion study the sun gear is combined with the motor and angular velocity of carrier is studied keeping the ring gear fixed.
• In the 2^nd motion study the ring gear is combined with the motor and angular velocity of carrier is studied keeping the sun gear fixed.
• In the 3^rd motion study the sun gear is combined with the motor and angular velocity of Ring gear studied keeping the carrier fixed.

Motion analysis

Assembly and Mates

Using the toolbox of American metric system in designer module, the gears are created. A spur gear with different no of teeth are selected for sun and planetary gears. Internal ring gear is used for the ring gear. All these have a module of 2.5.

For constraining and setting the components in right places, Coincident and concentric mates are used.

Motors, Solid Contacts,Gravity and FPS

In all the 3 motion studies, motor has been combined to different faces and axes.

Motion when given to Sun gear

Motion when given to Ring gear

All the solid contacts are made considering the material to be steel dry.

Gravity has been placed in Y axis

Plots

Sun gear is combined with the motor and angular velocity of carrier is studied keeping the ring gear fixed.

Input angular velocity

Output angular velocity

Ring gear is combined with the motor and angular velocity of carrier is studied keeping the sun gear fixed.

Input angular velocity

Output angular velocity

Sun gear is combined with the motor and angular velocity of Ring gear studied keeping the carrier fixed.

Input angular velocity

Output angular velocity

Results

Based on the analysis performed we came to a conclusion that, when

• Sun gear is combined with the motor and angular velocity of carrier is studied keeping the ring gear fixed The gear input angular velocity is 1200 and gear output velocity is 378. It works as a gear reduction mechanism as gear ratio is 0.315:1
• Ring gear is combined with the motor and angular velocity of carrier is studied keeping the sun gear fixed.The gear input angular velocity is 1200 and gear output velocity is 1194. It works as a gear reduction mechanism as gear ratio is 0.995:1
• Sun gear is combined with the motor and angular velocity of Ring gear studied keeping the carrier fixed.The gear input angular velocity is 1200 and gear output velocity is 383. It works as a gear reduction mechanism as gear ratio is 0.319:1

Conclusion

The analysis and the study for the planetary gear mechanism is done and the reuired plots are plotted.