The different friction properties of bearings according to the bearing can be divided into: sliding oil-free bearings and rolling bearings.
Bearings that bear the load by sliding operation of shafts and bearings are called sliding oil-free bearings. According to the oil film formation principle of two relative running surface of the sliding oil-free bearing. can be divided into fluid dynamic pressure lubrication bearings (also known as dynamic pressure Bearings) and hydrostatic bearings (also known as hydrostatic bearings). It is generally discussed that hydrodynamic lubricated bearings, which carry the oil between the two surfaces through the relative operation of the shaft and the bearing, form enough pressure film to separate the two surface, thus withstanding the Load.