In a simple planetary gear mechanism, the sun gear is loed at the center of the planetary gear mechanism. The sun gear and the planet gear are often engaged, and the two outer gears mesh and rotate in opposite directions. Just as the sun is loed at the center of the solar system, the solar wheel is also named after its position. In addition to being able to rotate around the supporting shaft of the planet carrier, planetary gears also rotate around the central axis of the sun gear under certain operating conditions, just like the rotation of the Earth and the revolution around the sun. When this situation occurs, it is called the transmission mode of the planetary gear mechanism. In the entire planetary gear mechanism, if the rotation of the planetary gear exists while the planetary carrier is fixed, this type of transmission similar to parallel axis transmission is called fixed axis transmission. The gear ring is an internal gear that is constantly meshed with the planetary gear, and is meshed with the internal and external gears, with the same direction of rotation between the two. The number of planetary gears depends on the design load of the transmission, usually consisting of three or four, with the larger the number, the greater the load.
