Planetary gear means that the rotation axis is not fixed and is mounted on a rotatable support. In addition to planetary gears that can rotate around their own rotating shafts like fixed-axis gears, their rotating shafts also rotate with the blue brackets around the axes of other gears. Rotation around its own axis is called “rotation”, and rotation around other gear axes is called “revolution”, just like the planets in the solar system, hence the name.
Compared with ordinary gear transmission, planetary gear transmission has many unique advantages. The most significant feature is that power can be split when transmitting power, and the input shaft and output shaft are on the same horizontal line. Therefore, planetary gear transmission has been widely used in reducers, speed increasers and transmissions in various mechanical transmission systems. Especially because of its characteristics of “high load and large transmission ratio”, it has been widely used in aircraft and vehicles (especially heavy vehicles). [1] Planetary gears also play a large role in engine torque transmission. Because the characteristics of the engine’s speed and torque are very different from the road driving requirements, to properly distribute the engine’s power to the drive wheels, the above characteristics of the planetary gears can be used for conversion. Automatic transmissions in automobiles also use these characteristics of planetary gears to change the relative motion relationship of various components through clutches and brakes to obtain different transmission ratios.
However, due to the complex structure and working state of the planetary gear, its vibration and noise problems are also prominent, and it is easy to cause failure phenomena such as tooth fatigue fatigue pitting, tooth root cracks and even tooth or shaft breakage, which affects the equipment’s operating accuracy, Delivery efficiency and service life.
The planetary gear has the following characteristics in structure: (1) The sun gear, planet carrier and ring gear are concentric, that is, they rotate around a common axis. This can eliminate countershafts and intermediate gears such as those used in manual transmissions; (2) All gears always mesh with each other, and there is no need to slip the gears when shifting, so the friction and wear are small and the life is long; (3) The structure is simple and compact, and its load is distributed to a large number of teeth with high strength; (4) Multiple transmission ratios can be obtained.
The planetary gear train has been widely used in various machinery, mainly in the following aspects: (1) Reduction transmission with large transmission ratio
(2) Realize compact high-power transmission
(3) Realization of motion synthesis
(4) Decomposition of movement