In the mechanical design of the sliding bearing

Bearing on the shaft and the shaft parts, ensure the accuracy of the axis of rotation.According to the friction properties of bearing work, can be divided into sliding bearing and rolling bearing.Sliding bearing is stable, no noise, small radial size, impact resistance and bearing capacity big, etc.And is a standard parts, rolling bearing into batch production of low cost, convenient installation, wide range of applications.For beginners, type selection of rolling bearing;Life calculation;Combination design is difficult to grasp.
11-1 summary of sliding bearing
A, the type of sliding bearing
The direction of the sliding bearing according to its load bearing can be divided into:
(1) the radial sliding bearing, it mainly bear radial load.
(2) the thrust bearing, it only bear axial load. 
Sliding bearing according to the state of friction (lubrication) can be divided into liquid friction lubrication bearing and non liquid friction lubrication bearing.
(1) liquid friction bearing (completely liquid lubricated bearing) the principle of friction bearing is between journal and bearing friction surface has plenty of oil, the thickness of the lubricating oil is larger, the shaft and bearing surface completely separated.Thus a small friction coefficient, average friction coefficient = 0.001 ~ 0.008.Due to have always been able to keep a stable liquid lubrication state.This kind of bearing is suitable for high speed, high precision and overloading, etc.
(2) the liquid friction bearing (not completely liquid lubricated bearing)
Non liquid friction bearing on adsorption on extremely thin oil film on the surface of the shaft and bearing hole, single can't completely to separate two friction surface, have direct contact with the part surface.Thus friction coefficient is big, = 0.05 ~ 0.5.If the lubricating oil completely lost, the dry friction will appear.Friction, wear, and even agglutination.
Second, the characteristics of the sliding bearing
Advantages: (1) the high bearing capacity;(2) work stable and reliable, low noise;(3) the radial size;(4) high precision;(5) fluid lubrication, friction, less wear and tear;(6) the oil film have certain vibration absorbing ability
Disadvantages: (1) the fluid friction sliding bearing, friction is bigger, badly worn.(2) fluid friction sliding bearing in starting, driving, load, rotary speed as a bigger of the two cases are difficult to achieve fluid friction;(3) the fluid friction, sliding bearing design, manufacturing, maintenance cost is higher.
11-2 sliding bearing structure and materials
A, radial sliding bearing
1. The integral sliding bearing
Integral sliding bearing structure, as shown by the bearing and bearing bushing of 2, 1 bearing upper oil hole, whole bushing with oil groove, respectively for gas and oil for lubrication.This kind of bearing has simple structure, low price, but the shaft is not convenient for installation and wear of bearing radial clearance after unable to adjust.Used for light load low speed or intermittent work.
2. To open sliding bearing
To open sliding bearing structure, as shown by the bearing seat, bearing cover, to open four, double end studs and gasket.Bearing and the bearing cover joint flour step, in order to locate.Put here have gaskets, in order to adjust bearing radial clearance after wear and tear.Therefore, convenient installation and wide application.
3. Automatic self-aligning bearing
Structure as shown, the external surface of the bearing shell made of spherical shape, with the inner surface contact ball bearing, can automatically adapt to the shaft when bending deflection, can reduce the localized wear.Or can be used for a wide span between bearing shaft neck longer.
Second, the thrust bearing
Thrust bearing structure as shown in figure, can be divided into three types:
Solid thrust bearing, axis neck is bigger than the edge of the end in the middle of the pressure, the lubricant is not easy, poor lubrication condition.
End of the hollow sliding thrust bearing, axis neck hollow parts can save oil, the pressure is more uniform, the bearing capacity is not big.
Polycyclic thrust bearing, the pressure is uniform, can bear larger load.But the ring bearing range, ring number cannot too much.
Three, bearing materials
The main failure mode of the sliding bearing, wear and agglutination, fatigue damage, etc
1. So the bearing material requirements:
Is mainly considering bearing these failure forms, the requirements of bearing material as follows,
(1) enough tensile strength, fatigue strength and shock ability;
(2) good anti-friction resistance, abrasion resistance and bonding resistance;
(3) the good compliance, embedding and running-in;
(4) the good corrosion resistance, thermal chemical properties, heat transfer and thermal expansion and the slide (adsorption capacity for oil)
(5) good plasticity.Have to adapt to the shaft bending deformation and other geometric error.
(6) good manufacturability and economy, etc.
Bearing shell can be made of a material, also can cast a layer of metal line within the bearing surface.The bearing bush.