Detailed explanation: How the oil film bearing housing works

    The oil film bearing seat is a radial sliding bearing seat with smooth oil as the smooth medium. The task principle is: during the rolling process, due to the rolling force, the roller shaft journal is forced to move, and the oil film bearing seat is center of gravity. Fairness with the center of gravity of the journal, so that the gap between the oil film bearing housing and the journal forms two areas, one is the diverging area (the gap is gradually increased along the direction of the journal rotation), and the other is the convergence area (along the journal) The direction of rotation is gradually reduced). When the rotating journal brings the viscous smooth oil from the diverging zone into the convergent zone, the bearing seat clearance becomes larger and smaller along the direction of the journal rotation, forming an oil wedge, which causes pressure in the smooth oil. The resultant force of the pressure at each point in the oil film along the rolling direction is the bearing capacity of the oil film bearing housing. When the rolling force is greater than the bearing capacity, the fair distance between the center of gravity of the journal and the center of gravity of the oil film bearing housing increases. In the asymmetry zone, the bearing seat clearance becomes steeper along the direction of the journal rotation, the minimum oil film thickness becomes smaller, the pressure in the oil film becomes larger, and the bearing capacity becomes larger until the rolling force reaches equilibrium, and the center of gravity of the journal is no longer offset, the oil film The bearing housing and the journal are completely separated by a smooth oil, which actually constitutes a fluid-smooth finish.
    From the mission principle of the oil film bearing housing, it is known that one of the most important parameters in the oil-membrane housing is the minimum oil film thickness. If the minimum oil film thickness value is too small, and the metal impurity particles in the smooth oil are too large, and the outer size of the metal particles is numerically larger than the minimum oil film thickness, the metal particles follow the minimum oil film thickness as the smooth oil passes the metal contact. When it is serious, it will burn tiles. In addition, if the minimum oil film thickness value is too small, when an accident such as a pile of steel is displayed, it is easy to form a metal contact between the journal and the oil film bearing seat to incur a burnt tile. The minimum oil film thickness value is related to the structural size and data of the oil film bearing housing, the machining accuracy of the coherent parts, the accuracy of the oil film bearing housing, the smooth oil and the rolling force.

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Key points for heavy-duty bearing selection

    The main points of heavy-duty bearing selection are basically the same as those for high-rigidity bearings.

The application of heavy-duty bearings must be considered in conjunction with the working characteristics of heavy-duty bearings. Heavy-duty bearings are often in high-stress conditions, and bearings are sensitive to high stresses. Therefore, all aspects of the application technology must strive to slow the stress of the bearing, and the stress reduction is very beneficial to extend the life of the bearing. For example, a high-load machine can multiply a single bearing of a certain fulcrum to two to withstand the radial load under the condition of the axial position, and the fulcrum is under the same workpiece condition despite the influence of load unevenness. The life of the two bearings is expected to increase by more than two times compared to the original single bearing. In fact, heavy-duty machines often use multiple bearings or multiple rows of bearings at one fulcrum to withstand radial loads.

  1. Heavy-duty bearing coordination, clearance and lubrication

The fit, clearance and lubrication of heavy-duty bearings must be considered uniformly.

In order to reduce the stress of heavy-duty bearings, it is desirable to have a thicker lubricating film layer, so it is preferred to use a higher viscosity lubricating oil or a higher viscosity oil as a base oil grease, and at the same time, in the case of ensuring good lubrication, The frictional torque due to the viscosity of the lubricant should not be too high.

The interference interference of the heavy-duty bearing rotating ferrule is larger than the normal situation, and this has an adverse effect on the deformation of the raceway and the bearing life. Therefore, if possible, it is desirable to reduce the interference properly, which requires lowering the mating surface. Roughness, while maintaining normal lubrication, because the lubrication fails, the excessive frictional torque on the surface of the heavy-duty lower raceway strengthens the creeping tendency of the mating surface, and even slips, although these phenomena occur mostly in the outer ring, but when severe The inner ring is also inevitable. The actual fit of the outer ring should not cause excessive gaps to prevent the grease from penetrating into the surface, which promotes the occurrence of slipping, and makes the ferrule easy to deform and reduce the bearing area of ​​the bearing.

Only after careful and effective measures are taken, it is allowed to appropriately reduce the interference of heavy bearings. However, although the interference is slightly reduced, the improvement of the bearing stress state is greater. Of course, the advantage of thickening the oil film is greater.

Due to the large contact area of ​​the rolling surface of the bearing under heavy load and the tight fit, the ferrule is close to the amount and deformation, so the clearance of the bearing is usually larger.

    2. Improve bearing conditions from host design

All drive shafts in the drive chain of the main engine should be taken at a higher speed until the drive speed reaches the working speed, and the mounting parts reserved for the main shaft bearings should be larger, which is convenient for selecting larger bearings. advantageous.

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General steps for maintaining bearing roll neck bearings

1) Track the position of the bearing in the mill and record it. Timken can provide customers with a roll neck bearing maintenance service record card that can be used to record the housing number, roll number, rack number, bearing position on the mill, outer ring bearing area and rolled product tonnage and bearing working hours Number of data. The record card should be updated at any time and is convenient for maintenance personnel to check. The bearing blanks can record bearing measurement data and other test details.

2) Remove the bearing housing from the roll and remove the bearing from the bearing housing. Whether it is to remove the bearing from the bearing housing or to carry out bearing inspections, special lifting methods and tools are required. Timken can provide customers with lifting tools and special lifting methods.

3) Clean the bearings. All flaking, water, residual lubricant and any other contaminants that cause severe wear on the bearings should be removed during the cleaning of the bearings. The cleaning method and cleaning agent used to clean the bearings are determined according to the size of the bearing to be cleaned or the number of bearings. Small bearings or a small number of bearings can be used with kerosene, mineral oil or other commercial solvents. For large bearings or large numbers of bearings, use a neutral oil with a viscosity of 22 cSt (or 100 SUS at 100 °F) at 40 °C in a cleaning tank.

4) Check the bearings, including visual inspections and minor repairs. On the outer surface of the inner ring or the surface of the roller on which the roller can be removed, if a small peeling or skin crack is found, the metal is usually peeled off by a sander and the edge of the peeling surface is polished.

5) The degree of bearing wear should be checked regularly, and the bearing wear can be evaluated by measuring the bearing clearance;

6) Inspect and repair the bearing housing as needed;

7) Put the bearing back into the bearing housing;

8) Inspect and repair the roll neck as needed;

9) Mount the bearing housing with the bearing onto the roll.

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Talking about: the use and maintenance of automobile bearings

    Maintenance instructions for automotive bearings:

The vehicle should work within the rated load range. If the overload is severe, the bearing will be overloaded directly, which will cause early failure of the bearing, and more serious will cause vehicle failure and personal safety accidents;
The bearing is prohibited from being subjected to abnormal impact loads;
Regularly check the state of use of the bearing, pay attention to observe whether there is abnormal noise and partial sharp temperature rise in the bearing part;
Regular or quantitative filling of lubricating oil or grease as required;
According to the condition of the vehicle, the lubricant should be completely replaced at least every six months, and the bearings should be inspected carefully;
Inspection under bearing maintenance condition: Clean the bearing under detachment with kerosene or gasoline, carefully observe whether there is sliding or creeping of the inner and outer cylindrical surfaces of the bearing, whether the inner and outer raceway surfaces of the bearing are peeling or pitting, rolling elements and holding Whether the frame is worn or deformed, etc., based on the comprehensive condition of the bearing inspection, determine whether the bearing can continue to be used.

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