How does the number of planetary gears in a planetary gearbox affect the reduction ratio and output torque

In planetary gearboxes, the number of planetary gears does not directly affect the reduction ratio, but has a direct impact on the output torque. The specific analysis is as follows:

The impact on reduction ratio

In terms of principle, the reduction ratio mainly depends on the number of teeth on the sun gear and inner ring gear, and is not directly mathematically related to the number of planetary gears.

In practical applications, in multi-stage planetary gearboxes, the reduction ratio of each stage is mainly determined by the sun gear and inner ring gear of that stage. Increasing the number of planetary gears is generally not to change the reduction ratio, but to meet other design requirements such as load sharing and improving load-bearing capacity. However, the increase in the number of planetary gears may indirectly affect the structural design and transmission efficiency of the planetary carrier to some extent, but it will not directly change the theoretical calculation value of the reduction ratio.

The impact on output torque

Load bearing capacity improvement: With an increase in the number of planetary gears, multiple planetary gears share the load together, just like how multiple people share a heavy object. The force borne by each planetary gear is relatively reduced. In this way, the entire planetary gearbox can withstand and transmit greater torque, and the output torque also increases accordingly. For example, in some large lifting equipment, using planetary gearboxes with multiple planetary gears can significantly increase the torque of the motor to meet the needs of lifting heavy objects.

Improved torque output stability: More planetary gears participate in transmission, which can make torque transmission more uniform and smooth. Because each planetary gear plays a certain role in torque transmission when meshing with the sun gear and the ring gear, multiple planetary gears cooperate with each other to reduce fluctuations and unevenness in the torque transmission process. For example, in the feed system of precision machine tools, a reducer with multiple rows of star wheels can make the feed motion of the worktable smoother and improve machining accuracy.