Planetary Gear
MOTION ANALYSIS OF PLANETARY GEAR MECHANISM USING SOLIDWORKS MULTIBODY DYNAMICS
1.INTRODUCTION
GEAR
Gears are used for transmitting power from one part of a machine to another. In a bicycle, for example, its gears that take power from the pedals to the back wheel. Similarly, in a car, gears transmit power from the crankshaft to the drive shaft running under the car that ultimately powers the wheels.
TERMINOLOGY
To transmit power smoothly without any unnecessary vibrations the pitch circle or pitch circle diameter should be tangent for the gears to be mated and the modules should be the same for both the gears. In this project, we use spur type gears, in which one is with internal teeth, and the rest of the gears have external gear. Here we analyze planetary gear assembly using Solidworks multibody dynamics.
PLANETARY GEAR
A planetary gear set is made up of three types of gears; a sun gear, planet gears, and a ring gear. The sun gear is located at the center and transmits torque to the planet gears which are typically mounted on a moveable carrier. The planet gears orbit around the sun gear and mesh with an outer ring gear. Planetary gear systems can vary in complexity from very simple to intricate compound systems, depending on the application.
APPLICATION
Planetary gears are often used when space and weight are an issue, but a large amount of speed reduction and torque are needed. Other places you will find planetary gear sets include turbine engines, automatic transmissions, and even electric screwdrivers. Planetary gear systems can produce a lot of torque because the load is shared among multiple planet gears. Because of this, the load is more evenly distributed, and therefore the gears are more resistant to damage.
2. OBJECTIVE
Design planetary gear with the following parameters:
- Ring Gear:
- Module = 2.5 (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
Simulation & Analysis of planetary gear system with the following conditions:
Determine the plots for angular velocity.
3. PROCEDURE
This involves importing the sun, ring, and planetary gears from the Solidworks toolbox. For the planetary gear assembly, the type of gear used is a spur gear. Before proceeding for the assembly the unknown parameters are identified.
FORMULA
[m=d/T]
Where m is the module,
d is the pitch circle diameter,
T is the no. of teeth,
CALCULATION
- RING GEAR
m = 2.5, T = 46,
d = m. T = 2.5 * 46
d = 115mm
- SUN GEAR
m = 2.5, T = 14,
d = m. T = 2.5 * 46
d = 35mm
- PLANETARY GEAR
m = 2.5 (same as the other gears) we have to determine the pitch circle diameter and no. of teeth.
Pitch circle radius of ring gear = Pitch circle radius of sun gear + Pitch circle diameter of planetary gear
57.5 = 17.5 + (Pitch circle diameter of planetary gear)
Pitch circle diameter = 40mm
T = d/m= 40/2.5 = 16
|
S.NO |
GEARS |
PITCH CIRCLE DIAMETER |
MODULE |
NUMBER OF TEETH |
|
1 |
RING GEAR |
115 |
2.5 |
46 |
|
2 |
SUN GEAR |
35 |
2.5 |
14 |
|
3 |
PLANETARY GEAR |
40 |
2.5 |
16 |
4. MODELING IN SOLIDWORKS
As stated earlier the gears are imported to the assembly from the Solidworks toolbox.
RING GEAR
|
PITCH CIRCLE DIAMETER |
MODULE |
NUMBER OF TEETH |
PRESSURE ANGLE |
|
115 |
2.5 |
46 |
20 |
SUN GEAR
|
PITCH CIRCLE DIAMETER |
MODULE |
NUMBER OF TEETH |
PRESSURE ANGLE |
|
35 |
2.5 |
14 |
20 |
PLANETARY GEAR
|
PITCH CIRCLE DIAMETER |
MODULE |
NUMBER OF TEETH |
PRESSURE ANGLE |
|
40 |
2.5 |
16 |
20 |
CARRIER
This is modeled based on the distance between the sun gear and one of the planetary gear.
ASSEMBLY
Assembly is done using standard mates and analyzed using solid body contact. Gears mates or not used to mate the teeth of the gears.
5. SIMULATION & ANALYSIS
- CASE 1 (Plot the angular velocity of the carrier with the following condition)
|
Input |
- Sun Gear (200rpm) |
|
Output |
- Carrier |
|
Fixed |
- Ring Gear |
From the graph, it is observed that velocity starts from zero and reaches a maximum of 298 deg/sec and keeps on fluctuating due to the transmission of its movement to the other gears, matted to it.
- CASE 2 (Plot the angular velocity of the carrier with the following condition)
|
Input |
- Ring Gear(200rpm) |
|
Output |
- Carrier |
|
Fixed |
- Sun Gear |
This is similar to the previous graph where it starts from zero and reaches a value of 948 deg/sec. Initially, there is a fluctuation but as time increase the fluctuation in the velocity reduces and may reach a constant velocity sometime later.
- CASE 3 (Plot the angular velocity of the carrier with the following condition)
|
Input |
- Sun Gear(200rpm) |
|
Output |
- Ring Gear |
|
Fixed |
- Carrier |
From the above graph, it is found that the velocity increase from zero to 382 deg/sec and starts fluctuating. After some time the fluctuation stops and the velocity is maintained constant.
6. ERROR
Throughout the process, errors occurred multiple times, but some major errors are improper mates and during motion analysis, the contact body was not specified correctly. All the errors faced were eliminated only by the trial and error method.
7. RESULT
By fixing and giving rotary motion to various parts of the planetary gear assembly the angular velocity plots are created for time. This method of fixing and giving rotary motion to various gears helps to achieve various speeds during power transmission.
Motion by fixing ring gear
Motion by fixing sun gear
Motion by fixing carrier
SOLIDWORKS & EXCEL FILES
https://drive.google.com/drive/folders/17rTA1yxPx65wYTzxVZZaFcEM8qkkZ8GV?usp=sharing