Planetary Gear

NAME :- PRAJWAL SUTE

AIM:- To design Planetary Gear Train, perform the motion study on it and interpret the plots obtain by motion study.

INTRODUCTION

The task of gears is to transmit torques and to change the speed of rotation or the torque between the input and the output. When it is necessary to increase torque, planetary gears are often employed, particularly in the automobile industry. An example is their use in automatic gear transmission, transfer cases in four-wheel-drive vehicles, etc. Planetary gears are characterized by its high efficiency with a high transfer of torque even in very small construction spaces. They are suitable for clockwise and counter-clockwise use as well as in alternating, constant or intermittent operation.

A planetary gear train (also known as epicyclic gear) consists of two gears mounted so that the center of one gear revolves around the center of the other. A carrier connects the centers 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.

This gear train has specialty that the alteration of input and output will be possible. The input can be given to the sun gear and output can be taken from carrier by keeping the ring gear fixed. Otherwise by fixing the carrier and the output can be taken from ring gear. It also allows the forward and reverse rotation of the gear train.

MOTION STUDY

Motion studies are graphical simulations of motion for assembly models. Motion Analysis is most advanced motion simulation and it can be used for accurately simulating and analyzing the effects of motion elements (including forces, springs, dampers, and friction) on an assembly. Motion Analysis uses computationally strong kinematic solvers, and accounts for material properties as well as mass and inertia in the computations. You can also use Motion Analysis to plot simulation results for further analysis. You can incorporate visual properties such as lighting and camera perspective into a motion study.

Motion studies do not change an assembly model or its properties. They simulate and animate the motion you prescribe for a model. You can use mates to restrict the motion of components in an assembly when you model motion.

INPUT PARAMETERS

Use the following inputs for designing the Planetary Gear in the Solidworks.

• 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

CALCULATIONS

To find PCD of planet gear.

Form the geometry

D_R = D_S+2D_P

Hence PCD of planet gear = 40 mm

And hence teeth on planet gear = 16 teeth

Sr No.	Gear	Module (m in mm)	No of teeth (T)	PCD (mT in mm)
1	Sun Gear	2.5	14	35
2	Planet gear	2.5	16	40
3	Ring Gear	2.5	46	115

Go to Toolbox, go to ANSI metric (since module is given as 2.5mm) and select the required dimensions gear.

PROCEDURE

• Design the carrier by considering suitable dimensions. Make carrier as separate part
• Start the assembly by sketching the sketch on one of the plane. This sketch has circles of PCD’s of the all gears (As shown in fig.)

• Add the sun gear as per the dimensions given in the table.
• Make the bore of sun gear concentric with the sun gear sketch.
• Make one of its face coincide with the sketch plane.
• Add the planet gear as per the dimensions given in the table.
• Make the bore of planet gear concentric with the planet gear sketch.
• Make one of its face coincide with the sketch plane.
• Make a copy of planet gear as gear train has 4 number of gears. Follow the same steps as above.
• Add the carrier part into the assembly.

• Made its 4 shafts concentric with the bore of 4 planet gears.
• Make coincident with the sketch plane.
• Make axis of carrier coincide with the assembly origin axis (perpendicular to the front plane.)
• Add the ring gear as per the dimensions given in the table.
• Make the bore of ring gear concentric with the ring gear sketch.
• Make one of its face coincide with the sketch plane.
• Now go to the mates and select gear mates. Add gear mate between sun gear and planet gears with the known number of teeth.
• Similarly add gear mate between planet gear and ring gear.
• Now go to motion study select motion analysis. We have to perform the following cases.

Sr. No.	Input	Output	Fixed
1	Sun gear	Ring gear	Carrier
2	Sun gear	Carrier	Ring gear
3	Ring gear	Carrier	Sun gear

CASE 1 Input is given to sun gear and carrier is made fixed.

1. Add the motor to the sun gear with 10 rpm.
2. Go to the contact and select the parts and add steel dry to all.
3. Click on the calculate and see the simulation.
4. Plot the graph as angular velocity of output vs time.

CASE 2 Input is given to sun gear and ring gear is made fixed.

1. Now make new motion study and select motion analysis.
2. Suppress all gear mates.
3. Right click on ring gear and make it fixed.
4. Suppress the concentric mates of planet gear with sketch.
5. Now unsuppress all gear mates.
6. Add the motor to the sun gear with 10 rpm.
7. Go to the contact and select the parts and add steel dry to all.
8. Click on the calculate and see the simulation.
9. Plot the graph as angular velocity of output vs time.

CASE 3 Input is given to ring gear and sun gear is made fixed.

1. Now make new motion study and select motion analysis.
2. Suppress all gear mates.
3. Right click on sun gear and make it fixed.
4. Suppress the concentric mates of planet gear with sketch.
5. Now unsuppress all gear mates.
6. Add the motor to the ring gear with 10 rpm.
7. Go to the contact and select the parts and add steel dry to all.
8. Click on the calculate and see the simulation.
9. Plot the graph as angular velocity of output vs time.

CONCLUSION

• CASE 1 Input is given to sun gear and carrier is made fixed.

The above graph is angular velocity of ring gear vs time. The graph shows that angular velocity is linear function of time. The fluctuations are less so the output is smooth.

• CASE 2 Input is given to sun gear and ring gear is made fixed.

The above graph is angular velocity of carrier vs time. The graph shows that angular velocity is a linear function of time. There is a fluctuation at a point in the output, which can result in jerk in gear train.

• CASE 3 Input is given to ring gear and sun gear is made fixed.

The above graph is angular velocity of carrier vs time. The graph shows that angular velocity is a linear function of time. There is a fluctuation at a point in the output, which can result in jerk in gear train.