Bearings
Bearings are indispensable core components in mechanical engineering. Their primary function is to reduce the friction coefficient between rotating or moving parts of machinery, support the load of shafts and the components mounted on them, and ensure the stable operation of mechanical systems. From daily household appliances to industrial equipment, and from automobiles and high-speed railways to aerospace, bearings are applied in almost all mechanical scenarios involving relative motion. The following is a detailed analysis covering classification, core parameters, application scenarios, and maintenance:
I. Main Classifications of Bearings
Based on friction properties and structural characteristics, bearings are divided into two major categories: rolling bearings and sliding bearings. Among them, rolling bearings have become the mainstream due to their low friction and high efficiency, while sliding bearings excel in specific scenarios.
(I) Rolling Bearings
Rolling bearings convert sliding friction between the shaft and the bearing housing into rolling friction through rolling elements (such as steel balls and rollers). They have a low friction coefficient (typically 0.001–0.005) and high efficiency. They can be further classified based on the shape and structure of rolling elements:
Deep Groove Ball Bearings
Structure: Consists of an inner ring, outer ring, steel balls, and a cage. It can withstand radial loads and small axial loads.
Features: Simple structure, low cost, and high rotational speed (suitable for 10,000–30,000 rpm). It is the most widely used type of bearing.
Applications: Motors, water pumps, automobile wheel hubs, household appliances (e.g., washing machines, air conditioning compressors).
Cylindrical Roller Bearings
Structure: Rolling elements are cylindrical rollers. The inner or outer ring can be separated, and they have strong radial load-carrying capacity (2–3 times higher than deep groove ball bearings).
Features: Suitable for high-load and high-speed scenarios but cannot withstand axial loads.
Applications: Machine tool spindles, automobile gearboxes, large motors.
Tapered Roller Bearings
Structure: Rolling elements are tapered rollers, with inner and outer rings featuring conical raceways. They can withstand both radial and axial loads simultaneously.
Features: High load-carrying capacity; clearance can be adjusted during installation, but rotational speed is slightly lower than that of deep groove ball bearings.
Applications: Automobile differentials, wheel reducers, transmission shafts of heavy machinery.
Thrust Bearings
Structure: Rolling elements are balls or rollers, primarily designed to withstand axial loads (unidirectional or bidirectional) with weak radial load capacity.
Subtypes: Thrust ball bearings (suitable for light loads and high speeds) and thrust roller bearings (suitable for heavy loads and low speeds).
Applications: Crane hooks, axial support for machine tool spindles, automobile clutches.
Self-Aligning Bearings
Structure: The outer ring raceway is spherical, which can automatically compensate for shaft installation deviations or shaft bending deformation (allowing ±2°–3° deflection).
Features: Good impact resistance, suitable for scenarios where shafts are prone to tilting.
Applications: Agricultural machinery, textile machinery, papermaking equipment.
(II) Sliding Bearings
Sliding bearings operate based on sliding friction and have a simple structure (usually composed of bearing bushes and bearing housings). They offer high load-carrying capacity and are suitable for low-speed, heavy-load, or compact-structure scenarios:
Metal Sliding Bearings: Such as Babbitt alloy bearings (wear-resistant and impact-resistant, used in steam turbines) and copper alloy bearings (suitable for medium-speed machinery).
Non-Metal Sliding Bearings: Such as plastic bearings (corrosion-resistant and lightweight, used in food machinery) and graphite bearings (high-temperature resistant, used in high-temperature furnaces).
