Planeettapyörät

Planeettapyörät, also known as planetary gears or epicyclic gears, are a type of gear system consisting of one or more outer gears, or "planet" gears, that revolve around a central, or "sun" gear. In a typical planetary gear set, the planet gears are mounted on a carrier, which also rotates. The planet gears mesh with the sun gear and also with an outer ring gear, or "annulus," which surrounds the entire assembly.

The primary characteristic of a planetary gear set is its ability to achieve multiple gear ratios within a compact space. By holding different components stationary or allowing them to rotate, various output speeds and torque multiplications can be achieved. For example, if the sun gear is held stationary, the carrier's rotation will drive the planet gears, which in turn rotate the ring gear. If the ring gear is held stationary, the sun gear's rotation will drive the planet gears, causing the carrier to rotate at a different speed.

Planetary gear systems are known for their high power density, efficiency, and ability to transmit torque through a common axis. This makes them ideal for applications where space is limited or where significant torque is required. Common uses include automatic transmissions in vehicles, gearboxes for wind turbines, robotic actuators, and even in hand drills. The arrangement of the gears allows for load sharing among the planet gears, which can increase the system's load-carrying capacity. The design can be quite complex, with multiple stages of planetary sets used to achieve very high reduction ratios.