What are the common types of plane bearings?

In mechanical equipment and engineering systems, bearings serve as crucial components supporting rotating shafts and reducing friction. They come in a wide variety of types and structures. Among them, plain bearings (also known as sliding bearings) operate based on the principle of sliding friction. Compared to rolling bearings, they offer a relatively simple structure and high load-bearing capacity, making them widely used in metallurgy, shipbuilding, mining, heavy industry, and other fields.
Despite their seemingly simple structure, plain bearings can be subdivided into various types depending on the application, each with distinct operating characteristics, mounting methods, lubrication requirements, and usage scenarios. This article systematically reviews common types of plain bearings, combining their structural features and operating principles to help engineers gain a deeper understanding of how to choose the appropriate plain bearing type for different operating conditions.
1. Plain Bearing Types by Lubrication Method
Lubrication method is a key factor in determining plain bearing performance. Based on lubrication characteristics, plain bearings can be divided into three basic types:
1. Oil-film-lubricated plain bearings (liquid-lubricated bearings)
This is a common type of plain bearing. Its operating principle is to form a continuous film of lubricant between the shaft and bearing housing, preventing direct metal-to-metal contact. Loads and power are carried and transmitted through the shear action of the oil film. Oil film lubrication significantly reduces friction and wear, extending service life.
Key Features:
Suitable for high-speed, medium-load operating conditions;
Requires a well-equipped lubrication system;
Boundary friction occurs during starting and stopping, requiring special attention to initial lubrication conditions.
2. Boundary Lubricated Sliding Bearings
Under certain high-load or low-speed operating conditions, it is difficult to form a complete oil film. Boundary lubricated bearings are therefore used. Wear-resistant materials (such as those containing solid lubricants or lubricating coatings) are often used on the bearing surface to reduce friction and wear.
Key Features:
Suitable for low-speed, high-load, frequent starting, or vibration environments;
Requires low lubricant viscosity;
Strong resistance to dry friction, making them suitable for occasional lubrication or environments where continuous lubrication is unavailable.
3. Self-lubricating Sliding Bearings (Dry Bearings)
Self-lubricating bearings do not require an external lubrication system. The bearing body contains the lubricant or has a lubricating structure. Common materials include polytetrafluoroethylene (PTFE), graphite, and copper-based powder metallurgy. These bearings are suitable for systems with limited space and difficult maintenance, such as aviation equipment and household appliances. Main Features:
Maintenance-free or low-maintenance;
Low noise, suitable for quiet operating conditions;
Service life is limited by material properties and is not suitable for high-load and high-speed applications.
II. Types of Plane Bearings Classified by Bearing Structure
In addition to lubrication method, different structural types are also important criteria for distinguishing plane bearings. The following are common structural classifications:
1. Cylindrical Sliding Bearing (Sleeve Bearing)
This is the basic type of sliding bearing. The sleeve is cylindrical, and the inner bore matches the shaft. It is primarily used to support rotating shafts and is commonly found in small and medium-sized machinery such as motors and water pumps.
Features:
Simple structure and easy processing;
Suitable for stable rotating systems with low axial loads;
Requires a good lubricating oil environment.
2. Split Sliding Bearing
This type of bearing consists of two semicircular bearing blocks, upper and lower, or left and right, making it easy to install and disassemble. It is commonly used in large, heavy-load equipment such as rolling mills and steam turbines.
Features:
Easy to maintain and replace;
Suitable for carrying large shaft diameters and heavy loads;
Usually used in conjunction with a lubricating oil system. 3. Thrust Sliding Bearing (Plane Thrust Bearing)
Thrust bearings are designed to carry axial loads, that is, forces acting along the length of a shaft. They are disc-shaped, with the shaft contacting them via a circular flat surface to absorb thrust.
Features:
Used in systems that require support for axial forces, such as propeller shafts and motor shafts;
Can be used in conjunction with radial sliding bearings;
The surface often features oil grooves or grooves to enhance lubrication.
4. Multi-wedge Sliding Bearing
This type of bearing features multiple wedge-shaped lubricating oil film zones on the bearing seat surface. Viscous action during shaft rotation creates multiple pressure zones, improving load-bearing capacity.
Features:
Excellent dynamic pressure performance;
Strong stability, suitable for high-speed bearing systems;
High manufacturing cost, primarily used in the aviation industry.
5. Tilting Pad Bearing (Tilt Pad Bearing)
This bearing consists of multiple small, tilting pads that automatically adjust their contact angle to accommodate slight shaft deflections and vibrations, thereby creating a stable oil film bearing zone. Features:
Strong dynamic oil film and high load-bearing capacity;
Particularly suitable for high-speed, large-diameter applications;
Mainly used in steam turbines, compressors, generators, etc.

Plane Bearings by Material Type
Bearing material directly determines its performance, lifespan, and operating environment. Plane bearings can be divided into the following categories based on the material:
1. Metal Bearings
These include materials such as bronze, cast iron, babbitt alloy, and copper-based powder metallurgy. Metal bearings are widely used in traditional equipment due to their high-temperature resistance, high strength, and long life.
Applicable Applications:
High temperatures and heavy loads;
Industrial equipment with comprehensive oil lubrication systems;
Commonly found in heavy machinery and power systems.
2. Non-metallic Bearings
Represented by plastics, engineering ceramics, and composite materials. They are lightweight, have a low friction coefficient, and require no lubrication, but have relatively low load-bearing capacity.
Applicable Applications:
Light loads and low speeds;
Equipment requiring high quietness and corrosion resistance, such as medical equipment and food processing machinery;
Applications where space is limited and regular maintenance is not possible. 3. Multi-layer composite bearings
Composed of a steel plate base, a copper powder layer, and a polymer wear-resistant layer, they combine the strength of metal with the self-lubricating properties of non-metallic bearings. They are commonly used in systems requiring high precision but requiring infrequent lubrication.
Advantages:
Excellent starting lubrication and stable operation;
Lower cost than traditional metal bearings;
Suitable for equipment with medium loads and intermittent operation.
IV. Special Types by Function
Planar bearings also have derivatives and variants for specific engineering applications:
1. Magnetic Sliding Bearings
Using magnetic force instead of traditional friction support, the shaft levitates in a magnetic field, theoretically achieving zero friction. Although uncommon, they are highly valuable in high-speed, non-contact, and high-cleanliness environments.
2. Air Sliding Bearings (Gas-Lubricated Bearings)
Using air as the lubricant, the shaft and bearing are supported by a thin air film. They are suitable for equipment operating in oil-free or vacuum environments.
3. Ceramic Sliding Bearings
Made of ceramic materials such as alumina and silicon nitride, they offer high hardness, corrosion resistance, and insulation properties. They are often used in special media environments, such as high temperatures and areas subject to high acid and alkali corrosion. 5. Practical Selection Considerations
Selecting the appropriate plane bearing type requires comprehensive consideration of the following factors:
Load type and magnitude: Will it support radial loads and axial thrust? Is the load stable?
Speed rating: Is the system operating continuously at high speeds? Is hydrodynamic support required?
Lubrication feasibility: Is a comprehensive lubrication system available? Is dry operation permitted?
Environmental conditions: Are temperature, humidity, dust, or corrosive gases present?
Maintainability requirements: Is regular maintenance permitted? Is the installation concealed?
Lifespan and reliability requirements: Is the equipment a critical core component? Does it require a long lifespan?

Conclusion
Planar bearings, as sliding friction bearings, are widely used in various types of engineering machinery, energy equipment, and industrial systems due to their high load capacity, simple structure, and low manufacturing cost. A deeper understanding of their types reveals that despite their simple structure, they can adapt to a variety of complex operating conditions through diverse lubrication methods, material selection, and structural forms.
Rational selection, scientific maintenance, and proper installation are key to ensuring the stable operation and extended lifespan of plane bearings in actual use. With the development of materials science and manufacturing technology, future plane bearings will become more intelligent and multifunctional, and continue to provide strong support for engineering systems.