Planetary Gear
AIM:
To simulate and study the motion analysis of a planetary gear using solidworks motion study.
INTRODUCTION:
Planetary gear is a type of gear setup, that consists of a ring gear, a sun gear and a number of planetary gears. They are positioned in such a way that, the ring gear and the sun gear are concentric, and the planet gears are connected to both the ring gear and sun gear and are influenced by their motion.
The outermost gear is the rinng gear that has internal teeth which is connected directly with the four planet gears (spur gears) which are connected with the carrier at their internal diameters. The planet gears are further connected with the sun gear which makes the motion of each components connected to each other. The allignment of the gears are in such a way that, the transmission of power is possible between any two gear types, keeping the third type fixed. And in this simulation, we will analyze the following three configurations:
| Sl.No | Input | Output | Fixed |
| 1 | Sun Gear | Carrier | Ring Gear |
| 2 | Ring Gear | Carrier | Sun Gear |
| 3 | Sun Gear | Ring Gear | Carrier |
WHAT IS MOTION STUDY?
Motion study is the graphical simulation of physical motion between the assembly models. They simulate the actual motion that should occur between the bodies. We can govern the simulation according to our needs by providing the necessary conditions, and we can allign the setup of for the configuration by alligning all the relevant part models during the assembly.
The motion studies in solidworks can namely be categorised into three categories:
ANIMATION: It provides the most basic movement of the the part, witout accounting any physical parameters such as mass, physical contact or even gravity.
BASIC MOTION: It is an upgraded version of animation that accounts for the physical contact, mass, spring and similar physical parameters.
MOTION ANALYSIS: It is the most advanced form of simulation. It accounts for all the parameters that basic motion does, but in addition, it can simulate torque forces, motion path, momentum and even allows us to choose the material type.
CALCULATION:
GIVEN DATA:
- Ring Gear
- Module = 2.5
- Number of teeth = 46
- Sun Gear
- Number of teeth = 14
- Input Speed of the Gear = 200 rpm.
- Number of planet gears = 4
RING GEAR:
Module = 2.5
No. of teeth = 46
pitch diameter = (No. of teeth)x(Module) = 46x2.5 = 115mm
SUN GEAR:
Module = 2.5
No. of teeth = 14
pitch diameter = (No. of teeth)x(Module) = 14x2.5 = 35mm
PLANET GEAR:
Module = 2.5
pitch diameter = R(ring gear) - R(sun gear) = 57.5-17.5 = 40mm
No. of teeth = pitch diameter/module = 40/2.5 = 16
The respective gears were designed using the design library with the respective parameters, With face width of 12mm.
SUN GEAR:
PLANET GEAR:
RING GEAR:
CARRIER:
The dimensions of the carrier were in reference with the planet gears. The diameter of the arms of the carrier was equal to that of the nominial diameter of the planet gears and the distance between the adjacent arms was set according to the final allignment of the planet gears setup.
ALLIGNMENT:
To perform motion analysis, we have to allign all the component parts related to the motion first. To do this, we can draw a reference sketch in any of the assembly planes with their dimensions in scale with the pitch diameter of the respective gears and then, use the mate feature to allign them with reference to the sketch and restricting their movement to a single plane.
REFERENCE SKETCH:
After creating the reference sketch, the gear setup was arranged with the help of concentric and coincident mates. With this, the design and assembly ordeal was accomplished.
STARTING WITH MOTION ANALYSIS:
To start with motion analysis, we have to enable "SOLIDWORKS motion" which can be accessed through solidworks add-ons.
To get started with our simulation, we have to assign a motor to the sun gear at 200 RPM and fix the ring gear. In addition to that, we have to assign solid contact between:
-the planet gears and ring gear
-the planet gears and sun gear
-the planet gears and the carrier
Thats all. Now we just have to click on the "Calculate motion study" button to begin thhe simulation.
CASE-1:
The ring gear is fixed, and the motor is connected to the sun gear as input. With this setup, then the power transmission occurs between the sun gear and the planet gears and the carrier acts as the output.
YOUTUBE LINK FOR THE MOTION:
https://www.youtube.com/watch?v=pcpcxtdkDIs&feature=youtu.be
CASE-2:
The sun gear is fixed, and the motor is connected to the ring gear as input. With this setup, then the power transmission occurs between the ring gear and the planet gears and the carrier acts as the output.
YOUTUBE LINK FOR THE MOTION:
https://www.youtube.com/watch?v=ZkDTUvMEX1A&feature=youtu.be
CASE-3:
The sun gear is fixed, and the motor is connected to the ring gear as input. With this setup, then the power transmission occurs between the ring gear and the planet gears and the carrier acts as the output.
YOUTUBE LINK FOR THE MOTION:
https://www.youtube.com/watch?v=GP1YlnSl8CA&feature=youtu.be
CONCLUSION AND ANALYSIS:
In the above plots, we observe that the maximum output angular velocity is attained during CASE-2, where the sun gear is fixed and the ring gear and carrier act as input and output rerspectively. This happened so because, the gear ratio generated between them favoured to the maximum output velocity.
The gear ratio of planetary gears can be calculated by:
Where, N represents no. of teeth
`omega` represents the angular velocity
Hence, by following the equation, we find that case-2 gives highest output angular velocity since the input ring gear has a higher number of teeth.