The clearance and lubrication of bearing, you must understand that
Bearing clearance refers to the one bearing ring relative to the other one bearing ring radial movement of the total distance (radial internal clearance) or axial movement of the total distance (axial internal clearance).
Work clearance: Bearing practical work under the condition of the running clearance, the size of bearing rolling fatigue life, temperature rise and noise and other influential.
Original clearance: bearing without clearance
The clearance value is divided into the basic group, small clearance group (C2), clearance group (C3, C4). Large clearance group is applicable in the inner ring and the outer ring with the surplus amount is large, or if the temperature difference between inner and outer rings of large, deep groove ball bearings need bear large axial load or the need to improve the aligning performance, or need to improve bearing limit speed and reduce the friction torque of bearings and other occasions. Small clearance group is applicable to the higher rotation accuracy, the need for strict control of shell holes in the axial displacement and to reduce vibration and noise of the occasion.
Selection of bearing clearance, the general clearance group is zero or slightly positive.
The selection of bearing clearance is correct or not, the mechanical operation precision, bearing life, friction resistance, temperature rise, has a great influence on vibration and noise. Such as radial bearing clearance choice over an hour, will make the load bearing rolling body to increase the number of contact stress reduced, running more stable, but also increased friction resistance, temperature rise also increased. On the contrary, it is also.
Therefore, we need to consider the following factors in the selection of bearing clearance:
The changes will affect the tightness of the clearance value is matched with the bearing and the shaft hole of the shell 1. Generally after installation will reduce the clearance value.
2 bearing in operation, due to the different cooling condition of shaft and the housing, resulting in decreased temperature, clearance
3 as the shaft and the shell material of different thermal expansion coefficient to increase or decrease the clearance value.
Usually, the most suitable clearance basic radial bearing clearance work is stipulated in the standards. Under special conditions, not the basic set of clearance value, you can use the auxiliary clearance value, such as deep groove ball bearing the 3, 4, 5 groups suited to fit or inner and outer ring temperature too large mechanical components.
Install the appropriate clearance contributes to the normal work of rolling bearings. Clearance is too small, the rolling bearing temperature rise, is unable the normal work; the clearance is too large, large vibration equipment, rolling bearing noise.
The lubrication of bearing is divided into three kinds: grease lubrication, oil lubrication and solid lubrication.
1 grease lubrication
More for the bearing seat, sealing structure and lubrication facilities is simple, easy maintenance, in a certain extent, can prevent water, gas, dust and other impurities of the invasion. It consists of base oil, thickener and additive. (bearing Encyclopedia of micro channel: zcbk2014), of which, the base oil is a mineral oil, synthetic oil, which plays an important role in lubrication; thickening agent of lubricant temperature characteristics, water resistance, and play an important role; additive in lubricant enhanced antioxidant, anti rust performance.
Cone penetration of lubricating grease (penetration) is the performance of an indicator, said flow properties of lubricating grease. The bigger the value, the more soft the grease is not suitable for high temperature applications. The dropping point of lubricating grease is one of the indexes of its performance, which indicates the performance of the temperature. The higher the value, the higher the temperature is.
After installation, if the operation of the bearing is too little grease in the process, will make the raceway and rolling body surface between the lack of effective protection of oil film, the surface will be due to wear and bad. If too much, it will make the bearing in the process of running large heat, damage to the bearing. So, the inner one grease filled G
Among them, G: filling volume (g) D: bearing outside diameter (mm) B: bearing width (mm)
Ng: the ultimate speed of bearing grease (r/min) N: the actual working speed of the bearing (r/min)
When Ng/N<1.25, the filling amount of lubricating grease accounted for 1/3 of the bearing inner space.
When Ng/N>5, the filling amount of lubricating grease accounts for more than 2/3 of the inner space of the bearing.
2 oil lubrication
Common method of lubricating oil:
(1) oil bath lubrication
For low and medium speed bearing lubrication
(2) oil lubrication
Small bearings for high speed
(3) splash to oil lubrication
Bearing lubrication by splashing the gear on the shaft. Widely used in automobile gearbox, machine tool gear box, etc.
(4) circulating oil lubrication
(5) jet lubrication
(6) oil mist lubrication
(7) oil and gas lubrication
A piston type quantitative distributor is used to provide the oil regularly. The micro amount of the supply reduces the pollution to the surrounding environment, and the oil quantity is stable, the friction torque is small, and the temperature rise is low, and the oil is especially suitable for the high speed bearing.
Viscosity is one of the important indicators of lubricating oil, viscosity is too low, it is not easy to form oil film, and then cause the service life of the bearing is decreased; the viscosity is too high, it is due to the viscous resistance and cause fever, expand the power loss. Under the circumstances, the high speed of the selection of low viscosity lubricating oil.