Automatic transmission with planetary gear
Planetary gearing is used in automatic transmissions (AT) to vary the gear ratio and provide smooth gear changes. It consists of the following elements:
* Sun Gear: The central gear that is rotated by the drive shaft.
* Planetary Gears: Gears that rotate around the sun gear. They mesh with the sun gear and the ring gear.
* Gear: The gear that meshes with the planetary gears and the output shaft.
Working principle:
Depending on which elements are locked or unlocked, the planetary gear can provide different gear ratios:
* Direct drive: The sun gear and ring gear are locked, and the planetary gears rotate around them. In this case, the gear ratio is 1:1.
*Reduction gear: The sun gear is locked, and the planetary gears and pinion are unlocked. Planetary gears rotate around their axis and around the gear, which increases the gear ratio.
* Overdrive: The sun gear and planetary gears are unlocked and the pinion gear is locked. In this case, the planetary gears rotate around their axis and around the sun gear, which reduces the gear ratio.
Design:
An automatic transmission with a planetary gear usually has several planetary gears connected to each other. This allows a larger range of gear ratios to be achieved. Gear shifting is controlled by an electronic control unit (ECU), which uses sensors to detect engine speed, load and oil pressure.
Advantages:
* Smooth gear shifting
* Wider range of gear ratios compared to conventional gearboxes
* Less power loss compared to torque converter automatic transmissions
Flaws:
*May be more expensive to produce than other types of automatic transmissions
*More complex designs may require more skilled maintenance