Epicyclic gear

The epicyclic gear is a device of mechanical drive. It with the characteristic to have two degrees of mobility, like the Differential , i.e. he associates by two mathematical relations, three tree S having different number of revolutions.

These trains are often used for the reduction speed because of the great reports/ratios of reduction which this configuration authorizes (with equal compactness with a simple Engrenage). One finds such reducers in particular in the automatic gear boxes, the motor reducer electric, the Winch S.

Generally constituted of gears (it can also be a question of system with friction), one finds the following elements there:

two coaxial trees known as planetary ,
of the satellite S gearing with the 2 planet gears, and turning around their common axis
carries it satellite.
the frame

The epicycloidal term comes from the trajectory according to an epicycloid of a point of the satellites observed compared to the interior planet gear. One observes a Hypocycloïde however if the reference of the movement is it planetary outside, which is often fixed in the reducers. That thus corresponds exactly so that the observer sees who looks at evolving/moving a satellite.

Epicyclic gears

Various configurations

Parallel trains.

In the case of the trains Parallel S, the two planet gears gearing with the satellites can be located around (case of the external planet gears), or in the center (case of the interior planet gears). It results 4 configurations from them:

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