noun
planetary gear system; epicyclic gear train
Technical term used in mechanical engineering. Refers to a gear system consisting of a central sun gear, planet gears, and an outer ring gear.
この自動車の変速機には遊星歯車装置が使われている。
This car's transmission uses a planetary gear system.
遊星歯車 refers specifically to the planet gears within the system, while 遊星歯車装置 denotes the entire gear assembly.
Compound of 遊星 (planet) + 歯車 (gear) + 装置 (device), describing a gear mechanism where planet gears revolve around a central sun gear.