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What is a sliding oilless bearing

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  Bearings can be divided into sliding oil-free bearings and rolling bearings according to the friction properties of the bearings.
  A bearing that is subjected to sliding operation using a shaft and a bearing is called a sliding oil-free bearing. According to the sliding oil-free bearing, the principle of oil film formation on the two opposite running surfaces is different. Can be divided into fluid dynamic pressure lubrication bearings (also known as dynamic pressure bearings) and hydrostatic bearings (also known as hydrostatic bearings). Generally discussed is a fluid dynamic pressure lubricated bearing that carries oil between two surfaces by the relative operation of the shaft and the bearing to form a sufficient pressure film to separate the two surfaces to withstand the load.
  Under liquid lubrication conditions, the sliding surface is separated by the lubricating oil without direct contact, and the friction loss and surface wear can be greatly reduced, and the oil film also has a certain vibration absorbing capability. However, the starting friction resistance is large. The part of the shaft that is supported by the bearing is called the journal, and the part that matches the journal is called the bearing. The layer of friction reducing material cast on its inner surface in order to improve the frictional properties of the surface of the bearing pad is referred to as a bearing lining. The material of the bearing bush and bearing bushing is collectively referred to as a sliding oil-free bearing material. Commonly used sliding oil-free bearing materials are bearing alloys (also known as babbitt or white alloy), wear-resistant cast iron, copper-based and aluminum-based alloys, powder metallurgy materials, plastics, rubber, hardwood and carbon-graphite, PTFE. (PTFE), modified polyoxymethylene (POM), and the like. Sliding oil-free bearing applications are generally used under low-speed, heavy-duty conditions, or where it is difficult to maintain and fill lubricants.

  Compared with rolling bearings, sliding oil-free bearings have the advantages of high bearing capacity, good vibration resistance, stable and reliable operation, low noise and long service life. They are widely used in internal combustion engines, rolling mills, large motors and instruments, radars, astronomical telescopes, etc. aspect.
  Commonly used bearing materials are divided into metal materials and non-metal materials.
  (1), cast iron. Ordinary gray cast iron or wear-resistant gray cast iron with nickel, chromium and titanium alloy composition, or ductile iron can be used as a material for light-load low-speed bearing bushes. In these materials, a sheet-like or spheroidal graphite component is coated on the surface of the material to form a layer of lubricating graphite. After the surface of the wear-resistant cast iron is phosphating, a porous thin layer can be formed, which helps to improve the wear resistance.
  (2), bearing alloy. (usually babbitt or white alloy) bearing alloys are divided into two categories: one is based on tin, adding appropriate amount of bismuth and copper, called tin-based bearing alloys, such as ZChSnSb11-6; the other is Lead is the basic component, and an appropriate amount of tin and antimony is added, which is called a lead-based bearing alloy such as ZCnPbSn16-16.
  (3), copper alloy. Copper alloys can be divided into: cast lead bronze; cast tin zinc lead bronze; cast tin phosphor bronze; cast aluminum bronze; cast brass.
  (4), aluminum alloy. It is divided into two categories: low tin aluminum alloy, containing about 6.5% tin; high tin aluminum alloy, containing tin up to 20%.
  (5), ceramic metal. This is a bearing material that is pressed and sintered with different metal powders. The material is porous, and the pores account for about 10% to 35% of the volume. The immersion in the hot oil before use makes the pores full of lubricating oil. It has self-lubricating properties, also called oil-bearing bearings.
  (6), graphite. The graphite bearing bush can be pure graphite, its strength is low; plastic, resin, silver, copper or babbitt alloy can also be added to improve strength and improve adaptability.
  (7) Other non-metallic materials.
  1) Rubber. It is mainly used as a lubricant for water and is relatively dirty.
  2) Phenolic tape. It is a layered structure of cotton, asbestos or other rayon fabric bonded with phenolic resin.
  3) Nylon. Used on low load bearings.
  In dynamic pressure bearings, the frictional state between the sliding surfaces varies with operating conditions and lubrication properties. It is usually divided into the following three states:
  1, complete liquid friction
  The complete liquid friction state means that the two surfaces of the sliding oil-free bearing that are relatively sliding are completely separated by the lubricating oil film, and the oil film has a sufficient thickness to eliminate direct contact between the two friction surfaces. At this time, there is only friction between liquid molecules, so the coefficient of friction is small (f = 0.001 to 0.008), which significantly reduces friction and wear.
  2, boundary friction
  When the two sliding surfaces of the sliding oil-free bearing have lubricating oil, due to the adsorption of the lubricating oil and the friction surface, a very thin boundary oil film will be formed on the friction surface, which can withstand high pressure without damaging. . The thickness of the boundary oil film is smaller than one micron, which is not enough to separate the two friction surfaces. Therefore, when sliding relative to each other, the microscopic peaks of the two friction surfaces will break the oil film and form a local metal direct contact. The state is called the boundary friction state. In general, the boundary oil film can cover most of the friction surface. Although it does not completely eliminate the direct contact between the two friction surfaces like complete liquid friction, it can play a role in reducing wear. The friction coefficient f in this state is 0.008 to 0.01.
  3, dry friction
  The friction when there is no substance between the two friction surfaces is called the dry friction state, and in practice, there is no ideal dry friction. Because there are always oxide films on any metal surface, it is difficult to have pure metal contact (unless it is in a clean laboratory). Due to the dry friction state, a large amount of friction loss and severe wear will occur, so the dry friction state is not allowed in the sliding oil-free bearing, otherwise it will cause a strong temperature rise and burn the bearing bush.
  Complete liquid friction is the ideal condition for sliding oil-free bearings. For machines that are important and rotating at high speeds, ensure that the bearings operate in full liquid friction. These bearings are often referred to as liquid friction sliding oil-free bearings. The boundary friction often coexists with the semi-liquid friction state and the semi-dry friction state, and is generally referred to as a non-liquid friction state. For machines that are less important in low-speed and impact conditions, the bearings can be designed in a non-liquid friction state, called non-liquid friction sliding oil-free bearings.

  Anhui IFAG Hardware Accessories Technology Co., Ltd. provides you with: oilless bearings, sliding bearing, self-lubricating bearings, composite bearings;


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  Anhui IFAG Hardware Accessories Technology Co., Ltd.

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  Address: No. 1188, Huaihai Avenue, Xinzhan District, Hefei, Anhui, China

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