Angular planetary gear reducer: the secret of deceleration and torque amplification under the coordination of self-rotation and revolution

1. Basic structure of planetary gear reducer
Angular planetary gear reducer is mainly composed of key components such as sun gear, planetary gear, inner ring gear, planetary carrier and output shaft. The sun gear is located in the center, as part of the input shaft, receiving external power; the inner ring gear is fixed on the outer shell to form a ring gear; the planetary gear is evenly distributed between the sun gear and the inner ring gear through the planetary carrier, and each planetary gear is meshed with the sun gear and the inner ring gear at the same time. This unique structural design provides the basis for the two motion modes of self-rotation and revolution for the planetary gear.

2. Self-rotation and revolution of planetary gear
The self-rotation of the planetary gear refers to the rotation of the planetary gear around its own axis, while the revolution refers to the rotation of the planetary gear around the central axis of the sun gear. When the sun gear is driven by external power, its rotational motion is transmitted to the planetary gear through meshing, so that the planetary gear rotates while also revolving along the trajectory of the sun gear. This compound motion mode significantly reduces the angular velocity of the planetary gear relative to the sun gear and the inner ring gear, thereby achieving the purpose of deceleration.

Specifically, assuming that the speed of the sun gear is n1 and the speed of the planet carrier (i.e., the speed of the output shaft) is n3, since the planet gear is in contact with the sun gear and the inner gear ring at the same time, its rotation speed n2 is between n1 and n3. Through precise design calculations, the number, size, and gear ratio of the planet gears can be adjusted to achieve the required deceleration ratio. This deceleration mechanism is not only efficient, but also compact in structure, greatly saving space.

3. Torque amplification under friction and pressure

The meshing between the planet gear, the sun gear, and the inner gear ring is not just a simple speed transmission, but also involves complex mechanical effects. During the meshing process, friction and pressure are generated due to the relative motion between the tooth surfaces. These forces are continuously accumulated during the rotation and revolution of the planet gear, and are transmitted to the output shaft through the planet carrier, thereby realizing torque amplification.

The principle of torque amplification is that when the planet gear rotates and revolves, the resultant torque (the sum of the torques transmitted by the sun gear and the inner gear ring) it is subjected to is greater than the input torque (i.e., the torque on the sun gear). This is because the planetary gears not only bear the driving force from the sun gear, but also the restraining reaction force of the inner gear ring during the meshing process. The two work together to enable the planetary gears to transmit greater torque to the output shaft. In addition, the more planetary gears there are and the more evenly they are distributed, the more significant the torque amplification effect is, and it also helps to improve the load-bearing capacity and running stability of the reducer.

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