Definition

1. Noun:
   • A type of bearing: A journal bearing is a specific type of plain bearing or sleeve bearing. It is a cylindrical component that supports a rotating shaft (called a journal) by providing a smooth, low-friction surface. The shaft rotates within the bearing, typically with a thin film of lubricant separating the two surfaces to reduce wear.

Usage

• Noun:
  • The crankshaft in a car engine is supported by journal bearings.
  • For high-load, low-speed applications, a journal bearing is often more durable than a ball bearing.
  • The engineer inspected the journal bearing for signs of wear or scoring.

Advanced Usage

• Fluid-film journal bearing: A type where a pressurized film of fluid (oil or gas) completely separates the shaft from the bearing surface, eliminating metal-to-metal contact.
  • Large turbines often rely on fluid-film journal bearings for smooth operation.
• Journal bearing failure: A common term describing the breakdown or seizure of this component, often due to loss of lubrication.
  • The root cause of the machinery shutdown was a catastrophic journal bearing failure.

Variants and Related Words

• Plain bearing (n): A broader category of bearings that includes journal bearings; they operate on sliding contact without rolling elements.
• Sleeve bearing (n): A common synonym for a journal bearing, emphasizing its cylindrical, sleeve-like shape.
• Bushing (n): A thin type of sleeve or journal bearing, often used as a lining or for lighter loads.
• Journal (n): The part of a rotating shaft that is in contact with and supported by the bearing.

Synonyms

• Sleeve bearing
• Plain bearing (in its cylindrical form)

Related Phrases

• Bearing clearance: The intentional gap between the journal (shaft) and the bearing surface.
  • Proper bearing clearance is critical for oil film formation.
• Bearing shell: The removable, often replaceable, half-cylindrical part that forms the bearing surface in an engine's connecting rod or main bearing.
  • The mechanic replaced the worn bearing shells during the engine rebuild.

Noun

1. the bearing of a journal