How planetary gears work

Planetary gears are at the heart of modern engineering and are used in gearboxes that power everything from basic plant machinery to cutting-edge electric vehicles. The simple configuration of a central drive and orbiting gears was developed thousands of years ago to model the movements of the planets. Today, engineers use planetary gears in applications that demand high torque density, operational efficiency and durability. 

What Is A Planetary Gear Set?

A simple planetary gear set is made up of three main components:

1. The sun gear that sits in the centre (central gear).

2. Multiple planet gears.

3. The ring gear (outer gear).

The three components make up a stage within a planetary gearbox. For higher ratios we can offer double or triple stages.

Planetary gearboxes can be powered by either electric motors, hydraulic motors or petrol or diesel combustion engines.

The load from the sun gear is distributed to several planetary gears which can either be used to drive an outer ring or a shaft or spindle. The central sun gear takes a high-speed, low-torque input. It drives several rotating external gears which increases the torque.

The simple design is a highly efficient and effective way of transferring power from a motor to an output. Approximately 97% of the energy input is delivered as an output.

Principles Of Operation.

In a wheel drive planetary gearbox, the sun gear drives the surrounding planetary gears which are fixed to a carrier. When the sun gear is driven, the planet gears rotate the outer ring gear. The wheels can be mounted over the housing of the gearbox. By mounting the wheel directly to the gearbox, the size of the assembly can be minimised. Wheel drive planetary gears can deliver up to 332,000Nm torque.



Application of planetary gear assembly in traveling gear box of excavator