Plain journal bearings, often referred to as sleeve bearings, bushings, sliding bearings, solid bearings, or friction bearings, are simple yet highly effective mechanical components. Unlike their rolling-element counterparts, such as ball bearings and roller bearings, plain journal bearings lack rolling elements. Instead, they rely on a layer of lubrication to create a low-friction interface between the bearing and the shaft it supports.
Plain journal bearings consist of two main components: the shaft and the bearing. The shaft is the rotating component, while the bearing, typically made of a low-friction material like bronze or babbitt, is housed in a stationary structure. The bearing is precisely machined to fit the shaft diameter and incorporates lubrication grooves and oil holes for effective lubrication.
When a plain journal bearing is in operation, a lubricant film is formed between the rotating shaft and the bearing. This film prevents direct metal-to-metal contact, reducing friction and wear. The lubricant film is maintained by the hydrodynamic action, where the relative motion between the shaft and the bearing creates a pressure gradient that draws lubricant into the contact zone.