Definition

1. Noun:
   • A type of gear system: A "planetary gear" is a gear arrangement consisting of one or more outer gears (planet gears) that rotate around a central gear (sun gear). All gears are contained within an outer ring gear (annulus). This system is also known as an epicyclic gear train.

Usage

• Noun:
  • The automatic transmission uses a complex set of planetary gears to change ratios smoothly.
  • A key advantage of the planetary gear design is its compactness and ability to provide high torque reduction.

Advanced Usage

• "Planetary gear set": This term refers to the complete assembly, including the sun gear, planet gears, planet carrier, and ring gear.
  • The engineer analyzed the entire planetary gear set for stress points.
• "Planetary gearbox" or "planetary reducer": These terms describe a mechanical device that uses a planetary gear system to reduce speed and increase torque.
  • The robotic arm is driven by a high-precision planetary gearbox.

Variants and Related Words

• Epicyclic gear (train) (n): A technical synonym for a planetary gear system.
• Sun gear (n): The central gear in a planetary system.
• Planet gear (n): One of the smaller gears that orbit the sun gear.
• Ring gear or Annulus (n): The outer ring with internal teeth that meshes with the planet gears.
• Planet carrier (n): The structure that holds the planet gears and allows them to rotate.

Synonyms

• Epicyclic gear train: The formal engineering term.
• Planetary gearset: Emphasizes it as a complete unit.

Related Phrases

• Planetary gear ratio: The specific speed/torque relationship achieved by a particular planetary gear configuration.
  • Calculating the correct planetary gear ratio is essential for the design.

Noun

1. an outer gear that revolves about a central sun gear of an epicyclic train