Ring Gear

A ring gear, also known as an annulus gear or internal gear, is a critical component in planetary reduction gear systems characterized by its internal teeth that engage with multiple planetary gears orbiting around a central sun gear. This configuration creates a compact, high-torque transmission mechanism where the ring gear typically remains stationary or rotates at reduced speed relative to input, enabling significant speed reduction ratios (often 3:1 to 10:1) while maintaining high mechanical efficiency (92-98%). The component serves as the reaction member in the gear train, with its fixed or controlled rotation determining the overall reduction ratio and torque output characteristics.

The ring gear operates on the planetary gear principle where multiple planetary gears rotate between a central sun gear and the internal teeth of the ring gear. When the sun gear rotates as input, it drives the planetary gears which walk along the stationary ring gear's internal teeth, causing the planetary carrier to rotate at reduced speed. The fundamental relationship follows: ω_sun = (1 + N_ring/N_sun) × ω_carrier, where N represents number of teeth. This epicyclic arrangement provides torque multiplication inversely proportional to speed reduction while distributing load across multiple gear meshes for enhanced durability.