Planetary reducer! Disassemble the hard core fit of the planetary gear, sun gear, and inner ring gear
Why are planetary gearboxes the "Transformers" of the industrial world?

In industrial automation, robot joints, and even aerospace equipment, there is a device that can convert high-speed rotating motors into precise torque output, which is a planetary gearbox.

It has a compact structure and high transmission efficiency, but many people hesitate due to the complex gear coordination inside.

Today we will explain in plain language the core secrets of planetary gearboxes!

structure

1. Sun Gear: the "heart" of power input

Appearance: Located in the center of the gearbox, shaped like a star with teeth.

Function: Directly connected to the input shaft of the motor, it is the starting point for power transmission.

2. Planet Gears: Diligent "Movers"

Appearance: 3-4 small gears are evenly distributed around the sun gear and fixed by brackets (planetary carriers).

Function: It simultaneously meshes with the sun gear and the inner teeth of the outer ring, rotating both on its own and revolving around the sun gear.

3. Ring Gear: the "commander" who controls the rhythm

Appearance: A ring gear with teeth on the outer side, fixed on the inside of the gearbox housing.

Function: By meshing with the planetary gear, the revolution speed of the planetary gear is limited, ultimately reducing the output speed.

How do the three major components work together seamlessly?

Scenario 1: Deceleration mode (most common)

Input: The motor drives the sun gear to rotate clockwise at high speed.

Transmission: The planetary gear meshes with the sun gear and begins to rotate counterclockwise; At the same time, the planetary gear attempted to orbit around the sun gear, but was "stuck" by the fixed internal gear ring.

Output: The rotation of the planetary gear is forced to be converted into a clockwise low-speed rotation of the planetary carrier, achieving deceleration and torque amplification.

Scenario 2: Differential Mode (Advanced Application)

Input: Both the sun gear and the ring gear are driven simultaneously (such as a car differential).

Transmission: The planetary gear adjusts its rotation and revolution ratio based on the speed difference between two inputs.

Output: The planetary carrier speed is synthesized by the speed of the sun gear and the inner ring gear, achieving power splitting.

Why are planetary gearboxes more efficient than regular gears?

1. Power split for stronger load-bearing capacity
Multiple planetary gears simultaneously share the load to avoid stress concentration at a single point. For example, three planetary gears can evenly distribute torque, increasing lifespan by more than three times.

2. Compact structure and small size
Gears are symmetrically distributed around the center, with extremely high utilization of axial space, suitable for narrow spaces such as robot joints.

3. Flexible transmission ratio and astonishing accuracy
By adjusting the gear combination of the sun gear, planetary gear, and inner ring gear, a transmission ratio of 3:1 to 1000:1 can be achieved, and the backlash can be controlled within 1 arc minute!