What is plain shaft bearings?

Plain shaft bearings are bearings that work under sliding friction. Sliding bearings work smoothly, reliably and without noise. Under liquid lubrication conditions, the sliding surfaces are separated by lubricating oil without direct contact, which can greatly reduce friction loss and surface wear, and the oil film also has a certain vibration absorption capacity. However, the starting friction 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. The anti-friction material layer cast on the inner surface of the bearing bush in order to improve the friction properties of the bearing bush surface is called the bearing liner. The materials of the bearing bush and the bearing liner are collectively referred to as sliding bearing materials. Sliding bearings are generally used under low-speed and heavy-load conditions, or in operating parts that are difficult to maintain and add lubricating oil.

Commonly used plain shaft bearings materials include bearing alloys (also called babbitt alloys or white alloys), wear-resistant cast iron, copper-based and aluminum-based alloys, powder metallurgy materials, plastics, rubber, hardwood and carbon-graphite, polytetrafluoroethylene (Teflon, PTFE), modified polyoxymethylene (POM), etc.

Plain shaft bearings absorb and transmit the force between relatively moving parts to maintain the position and positioning accuracy of the two parts. In addition, the directional motion must be converted into rotational motion (such as reciprocating piston engines)

When plain shaft bearings are working, sliding friction occurs; the magnitude of sliding friction mainly depends on the manufacturing accuracy; and the magnitude of sliding bearing friction mainly depends on the material of the bearing sliding surface. The working surface of sliding bearings generally has self-lubricating function; plain shaft bearings are divided into non-metallic sliding bearings and metal sliding bearings according to the material.

Non-metallic plain shaft bearings are mainly plastic bearings, and plastic bearings are generally made of engineering plastics with relatively good performance; more professional manufacturers generally have engineering plastic self-lubricating modification technology, and use fibers, special lubricants, glass beads, etc. to enhance the self-lubricating modification of engineering plastics to achieve certain performance, and then use the modified plastics to be processed into self-lubricating plastic bearings through injection molding.

The most commonly used metal plain shaft bearings in the early 21st century are three-layer composite bearings. This type of bearing is generally based on a carbon steel plate as the base plate. A layer of spherical copper powder is first sintered on the steel plate through sintering technology, and then a layer of PTFE lubricant with a thickness of about 0.03mm is sintered on the copper powder layer; the main function of the middle layer of spherical copper powder is to enhance the bonding strength between the steel plate and PTFE, and of course it also plays a certain role in load bearing and lubrication during operation.

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