Definition

1. Noun:
   • A gear in an epicyclic system: A "planet gear" is a gear in a specific mechanical arrangement (an epicyclic or planetary gear train) that rotates around a central gear. It is typically smaller than the central gear and meshes with it. The planet gear is often mounted on a moving carrier or arm.

Usage

• The term "planet gear" is used specifically in mechanical and automotive engineering to describe a component within a planetary gearset.
• It is a countable noun (e.g., , ).
• It functions as the subject or object in a sentence describing mechanical systems.

Examples

• Noun:
  • The planet gear meshes with both the sun gear and the ring gear.
  • In this transmission, each planet gear is mounted on its own pin.
  • A common failure point in the differential was a cracked planet gear.

Advanced Usage

• "Planet gear carrier" or "planet carrier": The structure that holds the planet gears and allows them to rotate together. The carrier itself can be an input or output in the gear system.
  • The input shaft drives the planet gear carrier.
• The system's operation depends on which component (sun gear, planet carrier, or ring gear) is held stationary, used as input, or used as output.

Variants and Related Words

• Planetary gear: Often used synonymously with "planet gear," though it can also refer to the entire gear system.
• Sun gear: The central gear that the planet gear(s) revolve around.
• Ring gear (or annulus gear): The outer, internally-toothed gear that the planet gear(s) also mesh with.
• Planetary gearset (or epicyclic gear train): The complete assembly containing the sun gear, planet gear(s), and ring gear.

Synonyms

• Pinion (in the context of a planetary system, though "pinion" has broader uses).
• Epicyclic gear.

Related Phrases

• Planet gear set: Refers to the group of planet gears working together within the carrier.
  • The planet gear set consists of four identical gears.

Noun

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