Adjustment and preloading of rolling bearing clearance

The assembly of rolling bearings is a common operation in the assembly and repair work of the fitter, and the adjustment and preloading of the rolling bearing clearance is an important part of the rolling bearing assembly work. Accurately grasping the process concept of clearance adjustment and pre-tightening, and correctly applying this process in assembly work is the guarantee of the quality of bearing assembly work.

The clearance of the rolling bearing refers to the maximum amount of movement of the other ferrule in the radial or axial direction when one ferrule is fixed, so the clearance is divided into radial clearance and axial clearance.

When the rolling bearing is assembled, its play should not be too large or too small. If the clearance is too large, the number of rolling bodies that can bear the load at the same time is reduced, so that the load of the single rolling body is increased, thereby reducing the rotation precision of the bearing and reducing the service life; if the clearance is too small, the frictional force is increased, resulting in an increase The increased heat, which exacerbates wear and tear, also reduces the service life of the bearing. Therefore, many bearings must be tightly controlled and adjusted during assembly.

The pre-tightening is that when the bearing is assembled, an axial force is applied to the inner ring or the outer ring of the bearing to eliminate the bearing play and cause initial deformation of the rolling element in contact with the inner and outer rings. Preloading can improve the stiffness and rotation accuracy of the bearing under working conditions. For bearings with large load and high rotational accuracy, most of them work without clearance or even a small amount of interference. In this case, the bearings need to be pre-tensioned during assembly.

The adjustment and preloading of the clearance are usually carried out by means of a suitable axial relative displacement of the inner ring of the bearing to the outer ring.

It is not difficult to see from the above concept of the technology that the adjustment of the rolling bearing clearance can improve the bearing capacity and rotation accuracy of the bearing and improve the service life of the bearing. At the same time, the bearing friction will be intensified and the heat generation will increase. Therefore, it is necessary to ensure good lubrication and heat dissipation while adjusting the clearance or pre-tightening. If improperly adjusted or poorly lubricated, it will in turn increase bearing wear and reduce life. Therefore, the following problems must be noted in the correct adjustment and preloading of the rolling bearing clearance.

1. Assembly technical requirements are the fundamental basis for selecting assembly process methods

The adjustment of the rolling bearing clearance can effectively improve the bearing rotation precision, improve the bearing capacity of the bearing, prolong the service life of the bearing, and also effectively reduce the vibration and noise, but not all rolling bearings need to be installed during assembly. Adjustment. The pre-fastening can improve the bearing rigidity and the precision of the rotation, but at the same time, the friction is intensified, the lubricating oil film is destroyed and a large amount of heat is generated. Therefore, the pre-tightened bearing must be forcedly lubricated and cooled. This method is limited to It is a special process for the bearing rigidity and rotation precision requirements. It is only used in the machine tool spindle assembly. The bearing assembly of other transmission mechanisms is almost invisible.

Whether to adjust and pre-tighten the clearance in the rolling bearing assembly is determined according to the assembly technical requirements of the technical documents. Specifically, in the assembly technical requirements, the bearings with high requirements for high speed, heavy load or rotation accuracy are generally required to adjust the bearing clearance or preloading. Otherwise, the bearing clearance is maintained, and only the shaft is used for assembly. Just fix it. From the perspective of the type of bearing, the clearance of the tapered roller bearing, the angular contact bearing and the thrust bearing needs to be adjusted; for the general low-speed, light-load radial ball bearing, in most cases, the clearance is not required. Adjusted and only fixed axially.

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Thrust ball bearing installation stability maintenance problem solution

When inspecting the thrust ball bearings that have been removed during the regular inspection and operation of TIMKEN bearing equipment and the replacement of peripheral parts, it is necessary to determine in turn whether the secondary bearing parts can be reused and the usage is better. Also carefully investigate and record the removed bearings and appearance. In order to clarify and investigate the remaining amount of lubricant, the bearings should be cleaned well after sampling.

Next, check the raceway surface of the bearing, the condition of the rolling surface and the mating surface, and the wear state of the cage, etc., for damage and abnormality, especially to observe the running track of the raceway surface. To determine whether the bearing can be used again, it is necessary to consider the degree of damage to the thrust ball bearing, machine performance, importance, operating conditions, inspection cycle, etc.

If the bearing is found to be damaged or abnormal, please find out the cause according to the phenomenon of bearing damage and formulate countermeasures. In addition, the inspection results, if there are the following defects, TIMKEN bearings can no longer be used, need to replace the new bearings.

When grease is added to anti-friction bearings, high pressure theory may not be required unless it is used with great care. High pressure can damage bearings and waste grease. Excessive grease can cause high temperatures and create an invisible environment around the bearings. In most applications, ball or roller bearings are fully lubricated if the grease level is between one-third and one-half of the bearing capacity. The excess will usually be wasted by the sealed casing.

1. Are all requirements for the installation surface and installation site?

If there is foreign matter such as iron filings, burrs, dust, etc. in the thrust ball bearing, the bearing will generate noise and vibration during operation, and even damage the raceway and rolling elements. Therefore, before installing the bearings, you must ensure that the mounting surface and the installation environment are clean.

2. Must the bearings be cleaned before installation?

The surface of the bearing is coated with anti-rust oil. You must clean it with clean gasoline or kerosene, and then apply it with clean high-quality or high-speed high-temperature grease.

The effect of cleanliness on TIMKEN bearing life and vibration noise is very large.

But we must remind you that the fully enclosed bearings do not need to be cleaned and refueled.

3. How to choose grease?

Lubrication has a very important influence on the operation and life of the bearing.

Here is a brief overview of the general principles for selecting grease. Grease is made of base oil, thickener and additives. The grease performance of different types and different grades varies greatly. The allowable rotation limit is different. Be careful when selecting.

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Analysis of cleaning, overhaul and damage of timken deep groove ball bearings

First of all, some equipments require TIMKEN bearings to be particularly strict with their own clearance problems. If the clearance is too large, even if it is slightly larger, it will easily wear parts of the equipment, so it is only necessary to reduce Clearance to solve this problem, but another problem has arisen, that is, if the clearance is too small, the problem of heat dissipation, if the heat is not properly, it will easily lead to an increase in internal temperature and eventually cause the bearing to overheat and burn!

Secondly, it may be an excessive load (preload is too large). The speed is too high. The play is too small. There is water or other foreign matter invading. If the above two cases are not the case, the accuracy of the shaft and the bearing housing is poor, and the deflection of the shaft is large. Seeing this, I think everyone wants to know the solution. First, we should study the lubricant and lubrication method, choose the TIMKEN deep groove ball bearing lubricant, and its dosage, and correct the bearing selection. Research is to match, bearing clearance and preload, and to improve the seal. Check the accuracy of the shaft and bearing housing. Of course, if you have an expert next to you, let him operate and learn the best!

1, the cleaning of the bearing

When disassembling the lower bearing for inspection, first record the appearance of the deep groove ball bearing, confirm the residual amount of the lubricant, and then wash the bearing after sampling the lubricant for inspection. As a cleaning agent, gasoline and kerosene are commonly used.

The cleaning of the removed bearing is divided into coarse cleaning and fine fine washing. In the container, the metal mesh bottom is placed first, so that the bearing does not directly contact the container. When rough cleaning, if the bearing is rotated with dirt, it will damage the rolling surface of the bearing and should be noted. In the rough cleaning oil, use a brush to remove the grease and the adhesive. After it is almost clean, it is transferred to the fine wash.

Fine washing is to carefully clean the deep groove ball bearing while rotating in the cleaning oil. In addition, the cleaning oil should always be kept clean.

2. Inspection and judgment of bearings

In order to judge whether the removed bearing can be reused, check the bearing after cleaning, carefully check the raceway surface, the rolling surface, the state of the mating surface, the wear of the cage, the increase of the bearing clearance and whether there is dimensional accuracy. Falling damage, abnormality. For non-separable ball bearings, use one hand to support the inner ring and rotate the outer ring to check if it is smooth.

Separate bearings such as tapered roller bearings can be inspected separately for the rolling surfaces of the rolling elements and the outer ring.

Because large bearings cannot be rotated by hand, pay attention to the appearance of rolling elements, raceways, cages, ribs, etc. The higher the importance of bearings, the more careful inspection is required. fat.

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The importance of NSK bearing grease stability

In general, the amount of grease in the NSK bearing always exceeds the actual amount required to directly participate in the lubrication, in the cavity of the holder and the bearing cover, and forms a contour on the periphery of the rolling element. During this process, the bearing temperature rises rapidly due to the resistance of the excess grease. Although most of the excess grease is squeezed out at the beginning of the run, the grease that is squeezed into the raceway attachment may still be carried by the rolling element into the raceway. In the early stages of the bearing, most of the grease is squeezed out of the raceway very quickly (less than a minute), and the build-up grease is discharged a small amount while circulating along with the bearing rotor. At this time, the bearing temperature continues to rise until the excess bearing grease is completely discharged, which can be called the walking phase of the grease. According to the grease quality and filling amount in the bearing structure, this time may last for more than ten. Minutes, even hours.

After the remaining bearing grease is completely discharged, the remaining small amount of grease forms a thin layer of grease film on the mutual contact surface of the rolling element, the raceway and the cage, thereby entering the normal stage of the bearing. . At this time, the temperature gradually drops and reaches equilibrium. In other words, long-term lubrication is mainly borne by this layer of grease film. In addition, during the long-term operation of the bearing, the contour of the rolling element and the raceway and the grease on the cage are shrunk to separate a part of the base oil, and after flowing into the raceway, the lubrication is also supplemented. .

Different bearing greases are not the same in the contours of the bearings. It is necessary to form a contour that is relatively straightforward. The running time is short. In the long-term operation, the bearing temperature is low and stable. This is an ideal one. Grease is especially important for grease channeling.

Some so-called eddy-flow greases are not easy to form contours, and even if they are contoured, they are easy to collapse. At this time, the excess grease repeatedly returned to the raceway is in a state of being strongly stirred for a long time, and the bearing torque is large and the temperature is high. Unbalanced, noise may also be generated, and grease is also prone to deterioration and loss.

NSK bearing temperature rise treatment

When the bearing temperature rises, first judge whether it is malfunctioning. If it does rise, it should be treated as follows:

(1). Check the cooling water pressure, water flow and piping system is normal. If the water pressure is low, the filter may be clogged and cannot be disposed of in time. It can be shut down and put into use when it is confirmed that it can work.

(2). Check the oil pressure of the governor. If the oil pressure is low, the cooling water hydraulic valve may be closed.

(3). Check if the bearing has abnormal sound, NSK bearing and check if the bearing swing is abnormal.

(4). Observe the oil sample to see if there is any change in the oil color, and test it to see if it has deteriorated. If deterioration is confirmed, stop replacing the new oil.

(5). Check if the oil level is normal. If it is not normal, check if the oil drain valve is closed. If it is closed, it should be replenished. If the gasket is oily, it should be stopped.

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How to remove oil stains on TIMKEN bearings

TIMKEN has recently developed a new type of lubricant. In some applications, it is not possible to replenish the lubricant due to inaccessibility, or the operating environment requires very good antifouling properties. This new type of lubricant is ideal for these special situations. This solid lubricant (Solidoil) can be fully filled into the inner space of the TIMKEN bearing, enclosing the cage and rolling elements, which not only has no effect on the operation and operation of the TIMKEN bearing, but also greatly extends the service life of the TIMKEN bearing. .

The polymer material is a structure with numerous micropores that can hold up to 4 times more lubricant than usual. As the inner surface moves, the lubrication is slowly released, which ensures a balanced and consistent lubrication of each TIMKEN bearing.

The oil-filled polymer material is molded into the TIMKEN bearing. During the molding process, a very narrow gap is formed around the rolling elements and the raceway, allowing the TIMKEN bearing components to rotate freely. The oil that penetrates the gap provides good lubrication to the bearing from the beginning. This lubricant offers a number of advantages over conventional construction.

It is especially worth mentioning that, at any operating temperature, it ensures that the lubricant is evenly distributed on the surface of the TIMKEN bearing.

TIMKEN bearings are often used, oil can reduce the service life of the bearings, then how do we remove the oil on the TIMKEN bearings? The following teaches you how to easily remove the oil on the TIMKEN bearing.

Bearings hardened by soft dry oil or rust-proof paste should be immersed in hot oil of 100 ° C ~ 200 ° C, clamp the bearing with pliers, and brush the oil on the bearing with a brush. The soft dry oil or anti-rust paste is melted when heated to 100 ° C ~ 200 ° C, and is easily washed out from the gap of the bearing. Sometimes the bearing is shaken several times in the oil. Oil will also flow away from the gap.

When cleaning the radial spherical bearing of the TIMKEN bearing, the ball, the bead frame and the inner ring should be laterally turned out from the outer ring and then immersed in the hot oil. When the short cylindrical roller bearing is cleaned, the roller and the bead frame should also be cleaned. The inner ring and the outer ring are disengaged.

When hot oil is cleaned, the temperature of the oil should not exceed 20 °C.

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