Ring Gear (Internal Gear)

The ring gear, also known as an internal gear, is a stationary or rotating annular gear with teeth cut on its inner circumference. In planetary gear reducers, it serves as the outer gear that meshes with multiple planet gears orbiting around a central sun gear. This configuration provides high torque density, compact design, and multiple gear reduction ratios within a single stage. The ring gear's internal teeth engage with the planet gears' external teeth to transfer rotational motion and torque while maintaining precise alignment and load distribution across the gear system.

The ring gear operates on the principle of epicyclic gearing, where it either remains stationary (in fixed carrier designs) or rotates (in rotating carrier designs) while engaging with planet gears. As the sun gear drives the planet gears, they rotate and orbit within the ring gear's internal teeth, creating torque multiplication and speed reduction. The gear ratio depends on the number of teeth on the ring gear relative to the sun gear, following the formula: Reduction Ratio = (Ring Gear Teeth / Sun Gear Teeth) + 1.