Analysis of the structure and function of bearings: comparison between sliding bearings and rolling bearings

Structure and function of sliding bearings
Sliding bearings, as the name implies, achieve support and rotation functions through relative sliding between the journal (i.e., the component supporting the shaft) and the bearing bush. Its basic structure mainly consists of three parts: the journal, the bearing bush, and the anti-friction material layer on the inner surface of the bearing bush - the bearing liner.

Journal: As a component directly mounted on the shaft, the material and precision of the journal are directly related to the wear resistance and running stability of the bearing. It is usually made of high-strength, high-hardness alloy steel or stainless steel to ensure good dimensional stability and fatigue resistance during long-term operation.
Bearing bush: The bearing bush is the component in the motor plain bearing that directly contacts the journal, and its design needs to consider good lubrication performance and wear resistance. Common bearing bush materials include bronze, cast iron, babbitt alloy, etc. These materials not only have sufficient strength and hardness, but also can reduce friction loss under good lubrication conditions.
Bearing liner: In order to improve the wear resistance and extend the service life of the bearing bush, a layer of anti-friction material layer, i.e., the bearing liner, is usually cast on the inner surface of the bearing bush. This layer of material is mostly self-lubricating materials, such as polytetrafluoroethylene (PTFE), graphite, etc., which can effectively reduce the friction coefficient, energy consumption and wear under dry friction or boundary lubrication conditions.
Sliding bearings are widely used in heavy load, low speed and impact load occasions due to their simple structure, large load capacity and strong adaptability. However, their disadvantages such as large friction resistance, high power consumption and the need for good lubrication system support cannot be ignored.

Structure and function of rolling bearings
In contrast, rolling bearings reduce friction and achieve efficient rotation by rolling the rolling elements (such as balls and rollers) between the inner and outer rings. Its basic structure consists of four parts: inner ring, outer ring, rolling element and protective positioning frame.

Inner ring and outer ring: The inner ring is fixed on the shaft, and the outer ring is installed on the bearing seat or housing, which together constitute the motion track of the rolling element. The materials of the inner and outer rings are mostly high-carbon chromium bearing steel to ensure sufficient hardness and wear resistance.
Rolling element: It is the core component of the rolling bearing, which transmits load and reduces friction through its rolling motion. Common rolling elements include ball bearings and roller bearings. Ball bearings are suitable for high-speed and light-load applications, while roller bearings are more suitable for heavy-load and low-speed applications.
Protective positioning frame: used to maintain the spacing between rolling elements to prevent them from contacting each other or getting stuck between the inner and outer rings, and also helps guide the correct movement trajectory of the rolling elements.
Rolling bearings are widely used in high-speed, high-precision, and light-load mechanical equipment due to their advantages such as low friction resistance, flexible starting, and easy maintenance. However, their manufacturing cost is relatively high, and they also have certain requirements for installation accuracy and lubrication conditions.