MBD simulation - Planetary Gear

PLANETARY GEAR MOTION ANALYSIS

AIM:

To create motion analysis for planetary gear system using solidworks MBD.

INTRODUCTION:

Planetary gear system also know as epicyclic gear system has 3 main components, namely, sun gear (a normal spur/helical gear), a ring gear (internal teeth gear, aka annular gear) and no. Of planetary gears attached with planet carrier.

Unlike normal gear system which are all made adjacent and output and input shaft are parallel (not about worm gear or bevel gear systems) here input(s) and output shafts will be concentric.

The important thing for gears

1. At the contact between two teeth(each from each gear) the velocity should be same, otherwise overlap occurs.
2. The pitch circle of each gear should be tangent to each mating gears.
3. Module(pitch circle diameter(PCD)/ No. Of teeth) in case of metric system or diametric pitch(No. Of teeth/PCD) in case of inch system of all mating gears should be same.

The principle of epicyclic gear box is from 1^st principle.

When ring gear is fixed

When sun gear is fixed

When carrier is fixed

credits: https://www.youtube.com/watch?v=ARd-Om2VyiE

APPLICATIONS:

This setup made gearboxes compact and used in automotive gearboxes including automatic transmission, inside hub motor, output of CVT in scooters etc.,

CALCULATION

No. Of teeth - Z

Module - m

Given

m = 2.5 (same for all gears)

Z_ring = 46

Z_sun = 14

m=(PCD/z)

PCD_ring = 2.5 * 46 = 115mm

PCD_sun = 2.5 * 14 = 35 mm

PCD_carrier = (115-35)/2 = 40 mm (from gears PC should be tangent principle)

Z_carrier = 40/2.5 =16

3D MODEL

First make a sketch of all PCSs in right plane.

• From design library, import internal gears and spur gear.
• (facewidth = 12mm, OD of ring gear = 150mm, Shaft diameter for all 4 planet gears = 20 mm, Shaft diameter for sun gear = 15 mm)
• Make planet carrier as shown.

• Mates:

1. All gear face coincided with right plane
2. Ring gear OD and sketch’s PCDring concentric
3. Sun gear OD and sketch’s PCDsun concentric
4. Planet carrier shaft concentric with a circle of sketch
5. Concentric mates to all planet gears with planet carrier accordingly.

• Go to motion analysis, enable solidworks motion analysis (I’ve given colour here alone, check videos)
• Give Contacts for:
• 1) Planet gears with sun gear
• 2) Planet gears with ring gear
• 3) Planet gears with carrier

LINK: https://drive.google.com/drive/folders/1eDhKx_0HJ2CO3_MM7TW-v1zAmXemoUQU?usp=sharing

This link contains

• Part files and assembly files in a folder
• Zip file of them to avoid part missing error
• All 3 videos (compressed to mp4 as sizes were around 400mb, so download and then watch if not supported)

Objective for motion analysis

Case 1

1. Motor is set for sun gear axis at CW direction for 200RPM constant speed
2. Ring gear is fixed.
3. Angular velocity calculated for planet carrier shaft

(video in link: Download as drive is not supporting compressed video mp4)

Plot:

Case 2

1. Motor is set for ring gear axis at CW direction for 200RPM constant speed
2. sun gear is fixed.
3. Angular velocity calculated for planet carrier shaft.

(video in link: Download as drive is not supporting compressed video mp4)

Plot:

Case 3

1. Motor is set for sun gear axis at CW direction for 200RPM constant speed
2. Planet carrier gear is fixed.
3. Angular velocity calculated for ring gear.

(video in link: Download as drive is not supporting compressed video mp4)

Plot:

RESULT/CONCLUSION:

Case 1

1. Angular velocity is less compared to all.
2. The output speed is less compared input speed
3. The peaks in fluctuation represent the gear hitting each other.
4. This can be compared to first gear( less rpm more torque)

Case 2

1. Angular velocity is high compared to all.
2. The output speed is very high compared input speed
3. The peaks in fluctuation represent the gear hitting each other.
4. This can be compared top gear or overdrive gear( more rpm less torque)

Case 3

1. Angular velocity is higher than case 1.
2. But still the output speed is less compared input speed
3. The peaks in fluctuation represent the gear hitting each other.
4. This can be compared to second gear.