Bearings are the basic parts of machines and are widely used in the engineering industry. They are also supporting parts of various machines. There are different types of bearings and each type of bearing has its own characteristics.
To know more!
What is a warehouse?
The bearing is the part that supports the shaft, guides the rotation of the shaft and transports the load transmitted from the shaft to the structure. Bearing is an essential and widely used component and a fundamental part of the machinery industry. It is the supporting element of the rotating shaft or moving part of various machines, and it is also the supporting element that depends on the rolling body to achieve the rotation of the conveyor. It is also called machine joint.
Bearing Classification
1. Depending on whether or not there are rolling elements, bearings can be divided into roller bearings and sliding bearings.
According to the shape of the rolling elements, bearings can be divided into ball bearings, cylindrical roller bearings and tapered roller bearings.
2. According to the characteristics of bearings, they can be divided into centripetal bearings and thrust bearings.
Radial bearings are divided into radial ball bearings and radial roller bearings. Thrust bearings are divided into thrust ball bearings and thrust roller bearings.
Types of bearings and their properties
1. Deep groove ball bearings
Properties of deep groove ball bearings.
(1) Simple structure, low manufacturing cost, high manufacturing precision easy to achieve.
(2) Low coefficient of friction and high speed.
(3) Mainly used to support radial loads, but the radial clearance of the bearing increases. Due to the nature of angular contact ball bearings, they can support alternating axial loads in two directions.
(4) It is composed of more wave-shaped steel plate cages and more metal fixed cages for large bearings.
(5) They are the most representative bearings, widely used, very durable and do not require frequent maintenance.
(6) With a certain degree of alignment capability, the size and shape range can be changed in many ways.
2. Cylindrical roller bearings
Properties of cylindrical roller bearings.
(1) Because the rollers and the raceway are in linear contact, the radial load capacity is large and they can withstand high loads and shock loads.
(2) Low coefficient of friction, can be used for high-speed work, its limiting speed is close to deep groove ball bearings.
(3) N and NU type cylindrical roller bearings can be moved axially, can adapt to thermal expansion or installation errors caused by the change in the relative position of the shaft and housing, and can be used to support the free end.
(4) The machining effort on the shaft or base hole is high. The relative deviation of the outer ring axis that may be caused by bearing installation must be strictly controlled to avoid contact stress concentration.
(5) The inner and outer rings of the bearings can be separated to facilitate assembly and disassembly.
3. Tapered roller bearings
Properties of vortex ring roller bearings.
(1) The inner ring and outer ring of the bearing have a tapered raceway, the shape of the rollers is round table shape. The roller is in direct contact with the track and can withstand high combined radial and axial loads as well as axial loads. The axial load capacity increases with increasing contact angle.
(2) In the tapered roller design, the contact line between the roller and the raceway of the inner ring and outer ring must be extended beyond the intersection of the same point on the axis of the bearing used for rolling.
(3) Tapered roller bearings can be divided into single row, double row and four row and other different types according to the number of rollers installed. This type of bearing also uses more Imperial series products.
(4) The new design of tapered roller bearing adopts reinforced structure, larger roller diameter, longer roller length, more rollers and convex shape rollers, greatly improving capacity and service life. The contact of the large end surface and the large roller retaining edge is spherical and conical, which improves lubrication.
4. Thrust ball bearings
Properties of deep groove ball bearings.
(1) Thrust ball bearings are separable bearings with a pressure angle of 90°, which can be mounted individually and can only absorb axial loads.
(2) Low limit speed. Steel balls are pressed out of the raceway by centrifugal force and are easy to use, but are not suitable for high-speed operation.
(3) One-way bearing can bear one-sided axial load, two-way bearing can bear two-way axial load.
(4) The use of spherical seat ring thrust ball bearings with spherical alignment can eliminate the effects of installation errors.
5. Thrust roller bearings
Properties of deep groove ball bearings.
(1) Can only withstand unilateral axial loads and minor impacts.
(2) Large bearing rigidity, small space requirement, large axial load capacity and low sensitivity to shock loads.
(3) Suitable for low speeds, often used in work situations where thrust ball bearings cannot be used.
(4) When installing, make sure that the shaft and ring axes are not tilted.
6. Needle bearings
The characteristics of needle bearings.
(1) Needle bearings are radially small and have a very high radial load capacity. They do not support axial load and are therefore only used as free end supports.
(2) Promotes miniaturization and weight reduction of devices.
(3) When using needle bearings without an inner ring or without an outer ring, only with a caged needle bearing arrangement, the machining accuracy requirements of the mating pin or bore of the bearing housing must be met, the surface hardness must match the bearing collar race.
(4) They have a large coefficient of friction and are not suitable for higher speeds.
7. Plain bearings
The properties of plain bearings.
(1) Smooth, reliable and quiet operation of plain bearings.
(2) In liquid lubrication, the smooth surface is separated by the lubricating oil without direct contact. This can significantly reduce friction losses and surface wear. The oil film also has a certain vibration damping ability, but the initial friction resistance is large.
8. Magnetic Bearings
The properties of magnetic bearings.
(1) Compared with traditional ball, plain and oil film bearings, magnetic bearings have no mechanical contact and the rotor can reach high operating speeds.
(2) With the advantages of low mechanical wear, low energy consumption, low noise, long service life, no lubrication, no oil pollution, etc., especially for high speed, vacuum, ultra-clean and other special environments.
(3) The shaft type can be widely used in the fields of machining, turbomachinery, aerospace, vacuum engineering, rotor dynamics identification and testing, etc. It is considered a promising new type of wave.
How to choose different types of bearings?
1. Loading
(1) If radial loads (direction perpendicular to the axis) are mainly supported, select radial bearing. If mainly axial loads (in the same direction as the axis) are supported, choose the thrust bearing. Axial loads are also called axial loads.
(2) If the bearing supports a small load, choose a ball bearing; if the load is greater, choose a roller bearing.
(3) A bearing that supports radial and axial loads (synthetic load). If the synthetic load is small, choose deep groove ball bearing or angular contact ball bearing. If the load is greater, choose a tapered roller bearing.
(4) Generally, low speeds and high loads occur in plain bearings.
2. Rotation speed
(1) In general, under high-speed operating conditions, it is appropriate to use deep groove ball bearings, angular contact ball bearings and cylindrical roller bearings.
(2) At lower speeds, tapered roller bearings can be used.
(3) The limiting speed of thrust ball bearing is low and can only be used at lower speeds.
(4) For the same type of bearing, the smaller the size, the higher the allowable speed. When selecting bearings, care must be taken to ensure that the actual speed is less than the limiting speed.
3. Accuracy
(1) For spindles of machine tools, precision machines and instruments, etc., high concentricity of the rotating body is required. High-precision bearings of precision levels 5, 4, 2 and others should be used, including deep groove ball bearings, angular contact ball bearings, tapered roller bearings, cylindrical roller bearings and angular contact thrust ball bearings.
(2) High rotation accuracy is required, more frequent use of deep groove ball bearings, angular contact ball bearings, cylindrical roller bearings, etc.
(3) For most machines, choosing a 0 tolerance bearing is sufficient to meet the host's requirements.
4. Rigidity
(1) The elastic deformation of bearings is very small and cannot be taken into account in most machines. In some machines, such as machine tool spindles, however, bearing stiffness is an important factor. Generally, cylindrical roller bearings and tapered roller bearings should be chosen. Because these two types of bearings are under load, the rolling elements and the raceway touch each other at some points, so stiffness is low.
(2) Various types of bearings can also be preloaded to increase the rigidity of the support. For example, to prevent shaft vibration and increase the rigidity of the support, angular contact ball bearings and tapered roller bearings are often installed in advance with a certain axial force to prevent mutual compression.
5. Others
(1) If radial space is limited, you can choose between needle bearings or needle races as needed.
(2) Due to the vibration and noise of bearings, low-noise deep groove ball bearings can be used.
(3) When the bearing is required to have high rotational accuracy (such as a machine tool spindle) and when it is used in high-speed conditions, a bearing with higher accuracy than conventional bearings should be selected.
