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Several key points about bearing in mechanical design

wallpapers Tech 2020-05-29
Today we talk about some key points of bearings in mechanical design! Bearings are an important part of contemporary machinery and equipment. Its main function is to support the mechanical rotating body, reduce the friction coefficient during its movement, and ensure its rotation accuracy.
 
According to the different frictional properties of moving elements, bearings can be divided into rolling bearings and sliding bearings. Among them, rolling bearings have been standardized and serialized, but compared with sliding bearings, its radial size, vibration and noise are larger and the price is higher.
 
According to the load bearing direction, the bearings can be divided into radial bearings (bearing radial loads, also called radial bearings), thrust bearings (bearing axial loads) and radial thrust bearings (bearing radial and axial loads at the same time, and Called radial thrust bearings).
 
1. Sliding bearing
Sliding bearings: bearings that work under sliding friction. Sliding bearings work smoothly, reliably and without noise. Under the condition of liquid lubrication, the sliding surface is separated by lubricating oil without direct contact, which can greatly reduce friction loss and surface wear. The oil film also has a certain vibration absorption capacity, but the starting friction resistance is large.
The part of the shaft supported by the bearing is called the journal, and the part that matches the journal is called the bush. In order to improve the frictional properties of the bearing pad surface, the layer of anti-friction material cast on its inner surface is called a bearing bush. The materials of bearing bush and bearing lining are collectively called sliding bearing materials. The application of sliding bearing is generally under the condition of low speed and heavy load, or the operation part where it is difficult to maintain and replenish lubricating oil.
Sliding bearings can be divided into radial (centripetal) sliding bearings and thrust (axial) sliding bearings according to the direction of the load.
 
2. Rolling bearings
Rolling bearing is a kind of precise mechanical element that changes the sliding friction between the running shaft and the shaft seat into rolling friction, thereby reducing the friction loss. Rolling bearings are generally composed of four parts: inner ring, outer ring, rolling elements and cage.
The role of the inner ring is to cooperate with the shaft and rotate together with the shaft; the role of the outer ring is to cooperate with the bearing seat and play a supporting role; the rolling element is to evenly distribute the rolling element between the inner ring and the outer ring by means of the cage. Its shape, size and number directly affect the performance and life of the rolling bearing; the cage can evenly distribute the rolling elements, prevent the rolling elements from falling off, and guide the rolling elements to rotate for lubrication.
 
2.3 Type selection of rolling bearings
The size, direction and nature of the load on the bearing is the main basis for selecting the bearing type.
(1) Load size and nature: ball bearings should be used under light load and medium load; roller bearings should be used under heavy load or impact load.
(2) Load direction: For pure radial loads, deep groove ball bearings, cylindrical roller bearings or needle roller bearings can be used. For pure axial loads, thrust bearings can be used. When there is radial load and axial load, if the axial load is not too large, deep groove ball bearings, angular contact ball bearings with small contact angle, and tapered roller bearings can be used; if the axial load is large Two types of bearings with large contact angles can be selected; if the axial load is large and the radial load is small, the thrust angular contact bearing can be used, or the support structure of the radial bearing and the thrust bearing can be used.

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