Working Principles of Planetary Gears

Sky Zhang
3 min readDec 13, 2022

--

Planetary Gearbox Working?

Planetary gear is a kind of gear structure, in which usually one or more external gears rotate around a sun gear, just like a planet revolves around the sun, hence the name “planetary gear”.

Ⅰ. The planetary gear set is a sun and planet gear transmission mechanism of autobiography plus revolution

The structure of the planetary drive gear set is the same as that of the solar system. There is the sun in the middle and several large planets next to it. The planets revolve by themselves and revolve around the sun at the same time. Due to the number of gear, there will be a speed change effect, so as to achieve the purpose of speed change/deceleration.

Ⅱ. Planetary gears principles of operation

Most of the gears we know are gears with a fixed axis of rotation. For example, mechanical clocks, ordinary mechanical gearboxes, and reducers. Although all the gears above are rotating, their rotation center (coincident with the center of the circle) is often mounted on the casing through a bearing. Therefore, their rotation axis are fixed relative to the casing, so they are also called “fixed shaft gear transmission.”

Compared to being fixed, there must be movement. Correspondingly, there is a less well-known type of gears called “planetary gears” whose axis of rotation is not fixed, but is mounted on a rotatable bracket. Planetary gears can not only rotate around their own rotating shafts like fixed-axis gears, but their rotating shafts also rotate with the blue bracket around the axis of other gears. The rotation around its own axis is called “rotation”, and the rotation around the axis of other gears is called “revolution”, just like the planets in the solar system, hence the name “planetary gear”.

Just like the solar system, those gears with fixed axles of planetary reducers that become the center of planetary gear revolution are called “sun gears”, which are red. There are usually two meshing points on a planetary gear or on two mutually fixed planetary gears, which are in relationship with the two sun gears respectively. The axis of the gray internal gear coincides with the axis of the red external gear, which is also the sun gear.

The principle of gear transmission with a fixed axis is very simple. In a pair of gears that mesh with each other, one gear is used as the driving wheel, and power is transmitted from it, and the other gear is used as a driven wheel, and the power is output from it. Some gears are only used as a transfer station, which means one side meshes with the driving wheel and the other side meshes with the driven wheel, and the power passes through it.

Laifual is a professional harmonic drive company and planetary gear manufacturer. Our factory has passed the ISO 9001 international quality system certification. Our products are completely self-developed and custom gear manufacturing is also available. Laifual Drive has been providing professional services to more than 50 countries and has won the general praise of users. Welcome to contact us if you have any needs.

--

--