Lexicon DIY-Knowledge

Planetary gearing


Engrana planetario

Engrenage planétaire

Planetary gears or epicycloidal gears consist of a central sun wheel (as a rule, this is the drive wheel, often executed as motor pinion), the ring wheel with internal toothing (which is often fixed forming a part of the internal gearbox housing) and the planet wheels mounted on a web or frame which usually ends as the drive pinion.

Planetary gears can be very versatile. Different transmission ratios are obtained depending on whether the ring wheel, the sun wheel or the planetary wheels are fixed, driven or serve as drive. Several gears are connected in parallel at all times which means that high torques can be transmitted in accordance with the transmission diameter. The transmission has no free bearing losses and a good efficiency ratio.

There is a minimum of two planetary wheels, the maximum number is restricted by the space inside the ring wheel. Several planetary gears (gear train) can be connected in series to realise high transmission ratios.