Plain bearings are bearings that work under sliding friction. Sliding bearings work smoothly, reliably and without noise. Under the condition of liquid lubrication, the sliding surface is separated by the lubricating oil without direct contact, which can also greatly reduce friction loss and surface wear, and the oil film also has a certain ability to absorb vibration. However, the starting frictional resistance is large. The part of the shaft supported by the bearing is called the journal, and the part matching the journal is called the bearing bush. In order to improve the friction properties of the bearing pad surface, a layer of friction reducing material cast on its inner surface is called a bearing bush. The materials of bearing pads and bearing bushes are collectively referred to as plain bearing materials. Sliding bearing applications are generally under high-speed and light-load conditions.
There are many types of plain bearings: ① According to the direction of bearing load, it can be divided into radial (radial) sliding bearings and thrust (axial) sliding bearings.
②According to the type of lubricant, it can be divided into oil lubricated bearings, grease lubricated bearings, water lubricated bearings, gas bearings, solid lubricated bearings, magnetic fluid bearings and electromagnetic bearings.
③ According to the thickness of the lubricating film, it can be divided into two types: thin film lubricating bearings and thick film lubricating bearings.
④Bearing materials can be divided into bronze bearings, cast iron bearings, plastic bearings, gem bearings, powder metallurgy bearings, self-lubricating bearings and oil-containing bearings.
⑤ According to the structure of the bearing shell, it can be divided into round bearings, oval bearings, triple oil leaf bearings, stepped surface bearings, tilting bearing, and foil bearings.
Commonly used sliding bearing materials are bearing alloys (also known as Babbitt or white alloys), wear-resistant cast iron, copper-based and aluminum-based alloys, powder metallurgy materials, plastics, rubber, hardwood and carbon-graphite, polytetrafluoroethylene (special Fluoron, PTFE), modified polyoxymethylene (POM), etc. The sliding bearing absorbs and transmits the force between the relatively moving parts, maintaining the position and positioning accuracy of the two parts. In addition, the directional motion must be converted into a rotary motion (such as a reciprocating piston engine).