Rolling bearing and sliding bearing how to choose? - bearing knowledge

by:Waxing     2020-06-02
Bearing as a indispensable important components in mechanical products, plays an important role supporting axis of rotation. According to the different grinding quality bearings, the bearing can be divided into rolling friction bearing ( Referred to as rolling bearings) And sliding friction bearing ( Referred to as the sliding bearing) 。 Two types of bearings have different characteristics in the structure, advantages and disadvantages of each performance in use, want to combine practical consideration. The following of the rolling bearing and sliding bearing than performance comparison analysis. 01 structure and movement mode is rolling bearing and sliding bearing is the most obvious difference is that if there is a rolling body. Rolling bearings: is there a rolling body ( Ball, roller, tapered roller, needle) , backed up by its rotation axis of rotation, and the contact area is a point, rolling body, the more the more the contact point. Sliding bearing: no rolling body, rely on a smooth surface to support the axis of rotation, thus contact area is a plane. The structure of the different ways determines the movement of the rolling bearing is rolling, sliding bearing is sliding movement way, thus the friction situation is completely different. 02 carrying capacity is more overall, as a result of the sliding bearing confined area is large, its carrying capacity generally higher than that of rolling bearing, and rolling bearing to bear impact load ability is not high, but completely liquid due to oil film lubrication bearing cushion, the effect of vibration absorption, can withstand a larger impact load. When high speed rolling bearing in the roller of centrifugal force, to reduce its carrying capacity ( When high speed easy appear noise) 。 For dynamic pressure sliding bearing, the bearing capacity increases with the rotating speed increases. 03 friction coefficient and starting frictional resistance is the general working condition, the friction coefficient than sliding bearings of rolling bearings, and the numerical stability. The sliding bearing lubrication easily influenced by outside factors such as speed, vibration, friction coefficient variation range is larger. Startup, the stability of oil film has not been formed because of the sliding bearing, resistance than rolling bearing, but the static pressure sliding bearing starting work friction resistance and friction coefficient is very small. 04 applicable work speed is rolling bearing due to the limitation of centrifugal force and roller bearing temperature rise, speed not too high, generally applicable to medium and low speed working condition. Incomplete liquid lubricated bearing because of bearing heat and wear, work speed cannot be too high. Completely liquid lubricated bearing high speed performance is very good, especially when static pressure type that USES air as a sliding bearing, its rotational speed can reach 100000 r/min. Figure ( a) Rolling bearing; ( b) Sliding bearing of 05 power loss is due to the rolling bearing small friction coefficient, the general power loss is not big, than not completely liquid lubricated bearing, but when improper lubrication and installation. Completely liquid lubricated bearing friction power loss is low, but for static pressure sliding bearing, with the pump power losses, the total power losses may be higher than the dynamic pressure bearing. 06 is rolling bearing service life under the influence of material point corrosion and fatigue, fixed number of year of the general design for 5 ~ 10 years, or be replaced during the overhaul. Incomplete liquid lubricated bearing bushing wear serious, need to be replaced regularly. Completely liquid lubricated bearing life is infinite in theory, in fact because of the stress cycle, especially dynamic pressure sliding bearing, bearing shell material fatigue damage may occur. 07 rotary accuracy because of the small radial clearance, rolling bearing, rotating precision is generally high. Incomplete liquid lubricated bearing in boundary lubrication and mixed lubrication condition, operation is not stable, and more serious wear and tear, and precision is low. Completely liquid due to oil film lubrication bearing, buffer vibration absorption, high precision. Hydrostatic bearing rotation accuracy is higher. 08 the other side is rolling bearing the use of oil, grease or solid lubricant, the dosage is small, high speed when the dosage is bigger, the purity of the oil demand is high, therefore require seal, but bearing, and convenient to replace general journal does not require repair. For sliding bearing, except incomplete liquid lubricated bearing lubricant is commonly, liquid or gas amount is large, oily cleanliness requirements are very high, often bearing need to change, sometimes repair journal. The design of the serious shorten the service life of bearing, bearing problems.
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