Lubricating grease is indispensable in the operation of rolling bearings, and any maintenance of bearings cannot do without lubricating grease. Someone asked, is it better to have more lubricating grease? The answer is definitely no. Below are the precautions to be taken when using lubricating grease for bearings.

Excessive lubricating grease can actually pose many hazards during the maintenance of rolling bearings. Because lubricating grease has good adhesion, wear resistance, temperature resistance, rust resistance, and lubricity, it can improve high-temperature oxidation resistance, delay aging, dissolve carbon deposits, prevent the aggregation of metal debris and oil stains, and improve the wear resistance, pressure resistance, and corrosion resistance of machinery.

1. Installation of bearings

The correct installation of rolling bearings affects accuracy, lifespan, and performance. Therefore, the design and assembly department should conduct thorough research on the installation of bearings. I hope to install according to the homework standards. The items for homework standards are usually as follows:

(1) Cleaning bearings and their related components

(2) Check the dimensions and precision machining of related components

(3) Installation

(4) Inspection after installing the bearings

(5) Supply lubricant

2. Basic condition monitoring of bearings

During use, it is necessary to regularly monitor the basic external conditions of rolling bearings, such as temperature, vibration, and noise measurement. These regular inspections will detect potential problems early and prevent unexpected machine shutdowns, enabling production plans to be realized and improving factory productivity and efficiency.

3. Re lubrication of bearings

During operation, rolling bearings require proper re lubrication to achieve perfect performance. The methods of bearing lubrication are divided into grease lubrication and oil lubrication. In order for bearings to function well, the first step is to choose a lubrication method that is suitable for the usage conditions and purposes. If only lubrication is considered, the lubricity of oil lubrication has the advantage. However, grease lubrication has the advantage of simplifying the structure around the bearing.

4. Unloading of bearings

When rolling bearings reach their end of service life, they should be replaced.

Although rolling bearings can no longer be used, correctly removing the original bearings and replacing them with new ones in a timely manner can greatly promote the extension of the service life of the new bearings.

Bearing failure analysis is an important component of system engineering aimed at improving the reliability of working surfaces. The working function of bearings is defined by their specified losses, resulting in failure or non operation as a failure phenomenon. Bearing failures can be divided into two types based on their normal life failure and two early failures. This mainly analyzes the causes of early bearing failures caused by pitting and fatigue, and proposes improvement suggestions to improve the life and reliability of rolling bearings.

The fatigue failure of rolling bearings is a surface form of failure, mainly manifested as the initiation, propagation, and fracture processes of fatigue cracks, and the long-term effects of load failures under alternating conditions on the metal. The rolling bearing uses a cage made of glass fiber reinforced nylon 66, which is suitable for stable working temperatures not exceeding 120 degrees. When using oil lubrication for this type of bearing, if the oil contains additives, it may shorten the service life of the cage. When the temperature exceeds 120 degrees, aged lubricating oil will also shorten the life of the retainer. Therefore, it is important to observe and replace the lubricating oil as scheduled.

Sealed rolling bearings are lubricated with specially tested high-quality lithium based grease. This type of grease can withstand a high temperature of 120 degrees Celsius for a short period of time. If the stable operating temperature reaches 70 degrees or higher, the lifespan of standard lithium based grease will be shortened. To work frequently at high temperatures, special lubricating grease must be used, and attention should be paid to whether heat-resistant materials are needed as sealing devices. The operating temperature of standard contact seals cannot exceed 110 degrees. If high-temperature synthetic materials are used for sealing, it is also necessary to consider that this highly effective fluorinated material will release harmful gases and smoke beyond 300 degrees Celsius. Especially when using a welding gun to disassemble rolling bearings, it is important to pay attention to this point.

1. The ability of rolling bearings to withstand loads is much smaller than that of sliding bearings of the same volume, therefore, the radial size of their rolling bearings is larger. Therefore, sliding bearings are often used in situations that require large loads, small radial dimensions, and compact structures.

Bearing vibration and noise are significant, especially in the later stages of use., Therefore, in situations where precision bearings are highly required and vibration is not allowed, sliding bearings are generally preferred for better results.

3. Rolling bearings are particularly sensitive to foreign objects such as metal shavings. Once foreign objects are mixed in, they will produce intermittent large vibrations and noise, which can easily lead to damage. So the lifespan of rolling bearings also has a certain limit. In short, the lifespan of rolling bearings is shorter than that of sliding bearings.

The impact sound of rolling elements and its control method. When larger ball bearings or tapered roller bearings operate at low speeds under pure radial loads, the rolling elements in the non load zone will impact the cage or raceway and produce noise due to the small centrifugal force of the rolling elements. But as the speed increases, this sound will disappear. The control methods for the impact sound of rolling elements include: reducing the radial clearance appropriately and using bearings with a reasonable structure and flexible material cage.

Rolling sound of bearings and its control method Rolling sound is a harsh metal friction sound that can occur in cylindrical roller bearings in all situations, mostly occurring in larger grease lubricated bearings, but more likely to occur in lubricating grease with degraded base oil performance, and almost never occurs during oil lubrication.

First of all, if the structure is reasonably designed and progressiveness, the tapered roller bearing will have a longer life. The manufacturing of bearings generally involves multiple processing steps such as forging, heat treatment, turning, grinding, and assembly. The rationality, progressiveness and stability of each processing technology will also affect the service life of bearings. The heat treatment and grinding processes that affect the quality of finished bearings are often more directly related to bearing failure. In recent years, research on the deteriorated layer on the working surface of bearings has shown that the grinding process is closely related to the surface quality of bearings.

The metallurgical quality of bearing materials used to be the main factor affecting the early failure of tapered roller bearings. With the advancement of metallurgical technology, such as vacuum degassing of bearing steel, the quality of raw materials has been improved. The proportion of raw material quality factors in bearing failure analysis has significantly decreased, but it is still one of the main influencing factors of bearing failure. Whether the material selection is appropriate is still a factor that must be considered in bearing failure analysis.

The main task of bearing failure analysis is to identify the main factors causing roller bearing failure based on a large amount of background materials, analysis data, and failure forms, in order to propose targeted improvement measures, extend the service life of bearings, and avoid sudden early failures of bearings.

Before installing bearings, they should be cleaned with gasoline or kerosene, dried before use, and ensure good lubrication. Bearings are generally lubricated with grease or oil. When using grease lubrication, lubricating grease with superior properties such as impurity free, antioxidant, rust proof, and extreme pressure should be selected. The filling amount of lubricating grease should be 30% -60% of the volume of the bearing and bearing housing, and should not be too much. The double row bearings with sealed structure and the water pump shaft connecting bearings have been filled with lubricating grease and can be used directly by users without further cleaning.

When installing bearings, equal pressure must be applied on the circumference of the ring end face to press the ring in. Do not use tools such as pliers to directly strike the bearing end face to avoid damaging the bearing. In the case of small interference fit, a sleeve can be used to press the end face of the bearing ring at room temperature, and the sleeve can be tapped with a hammer to evenly press the ring through the sleeve. If installing in large quantities, hydraulic presses can be used. When pressing in, it should be ensured that the outer ring end face is tightly pressed against the outer shell shoulder end face, and the inner ring end face is tightly pressed against the shaft shoulder end face, with no gaps allowed.

The installation of bearings must be carried out under dry and clean environmental conditions. Before installation, carefully inspect the mating surface of the shaft and housing, the end face of the shoulder, the groove, and the processing quality of the connecting surface. All mating surfaces must be carefully cleaned and deburred, and the unprocessed surfaces of castings must be cleaned of molding sand. When the interference fit is large, oil bath heating or sensor heating bearing methods can be used for installation, with a heating temperature range of 80 ℃ -100 ℃ and a maximum temperature of 120 ℃. At the same time, nuts or other appropriate methods should be used to tighten the bearings to prevent them from contracting in the width direction after cooling, resulting in a gap between the ring and the shaft shoulder.

After the installation of the bearing, the clearance should be adjusted. The clearance value should be determined specifically based on different operating conditions and the size of the interference fit. If necessary, experiments should be conducted to determine. Double row roller bearings and water pump shaft bearings have their clearance adjusted at the factory and do not need to be adjusted during installation. After the installation of the bearing, a rotation test should be conducted. Firstly, it should be used for rotating the shaft or bearing box. If there are no abnormalities, the power should be used for no-load and low-speed operation. Then, depending on the operation situation, the rotation speed and load should be gradually increased, and noise, vibration, and temperature rise should be detected. If any abnormalities are found, the operation should be stopped and checked. It can only be delivered for use after the operation test is normal.

Contact fatigue failure is one of the common failure modes of various types of bearings, which is caused by the repeated action of cyclic contact stress on the bearing surface. The contact fatigue peeling on the surface of bearing parts is a process of fatigue crack initiation, propagation, and cracking. The initial contact fatigue crack first occurs at a relatively high orthogonal shear stress below the contact surface, and then extends to the surface to form pitting like peeling or small flake like peeling, the former being called pitting corrosion or pitting peeling; The latter is called shallow peeling. If the initial crack occurs at the boundary between the hardened layer and the core, causing early peeling of the hardened layer, it is called hardened layer peeling. It is one of the common failure modes on various bearing surfaces. The relative sliding friction between bearing components causes continuous loss of surface metal, which is called sliding friction. Continuous wear will cause changes in the size and shape of the parts, increase the clearance between the bearings, deteriorate the working surface morphology, thereby losing rotational accuracy and preventing the bearings from working properly. The forms of sliding wear can be divided into abrasive wear, adhesive wear, corrosive wear, micro motion wear, etc. Among them, the common ones are abrasive wear and adhesive wear.

Generally speaking, bearing installation is determined by the structure, size, installation part, and shape properties of the bearing. It is also important to lubricate and clean the bearings before installation

1、 Precautions for installation of bearings:

1. The fitting method between the bearing ring and the shaft is mostly transitional fitting, and the fitting between the bearing seat ring and the bearing seat hole is mostly clearance fitting. This fitting method is generally easy to install. The central axis of the bearing should be fixed on the shaft to avoid unnecessary wear caused by the relative rotation of the rings. In terms of the installation method of bearings here, there are more rotating installation methods, which can make the inner ring fit tighter.

2. When the outer ring of a cylindrical roller bearing is loosely matched with the bearing seat, and the inner ring is tightly matched with the shaft, a professional press used during bearing installation can be used to press the bearing onto the shaft first, and then install it together with the shaft and bearing into the bearing seat. When installing under pressure, pay attention to punching the surface of the inner ring of the bearing, and then pad it with a soft metal sleeve made of copper or soft steel. When assembling the sleeve with an inner diameter larger than the shaft neck diameter and an outer diameter smaller than the inner ring flange, avoid pressing it on the cage.

2、 Lubricating oil is an essential protective material for bearings. It can completely flush into the internal space of the bearing, enveloping the cage and rolling elements. It not only has no effect on the operation and work of cylindrical roller bearings, but also greatly extends the service life of the bearing. However, due to frequent use of lubricating oil, a certain amount of oil stains may be generated, and if the oil stains are not removed in time, it will affect the service life of the bearings, so it is necessary to remove the oil stains.

1. When cleaning bearings, the ball bearings, ball frames, and inner rings should be horizontally rotated out of the outer ring and then immersed in hot oil. When cleaning short cylindrical roller bearings, the rollers, ball frames, inner rings, and outer rings should also be separated.

Attention: When cleaning with hot oil, the temperature of the oil should not exceed 20 ℃.

2. Bearings hardened with soft dry oil or rust proof paste should be immersed in thermal oil at 100 ℃~200 ℃, clamped with pliers, and cleaned of oil stains on the bearings with a brush. Soft dry oil or rust proof paste melts when heated to 100 ℃~200 ℃, and is easily washed out from the gaps of the bearing. Sometimes, simply shake the bearing multiple times in the oil. Oil stains can also flow away from the gaps.

By using the above two methods, it is easy to remove oil stains from cylindrical roller bearings, in order to better utilize the lubricating oil, protect the bearings, and extend their service life. In most cases, bearing failure is caused by improper installation and lubrication. So, the installation and lubrication maintenance of bearings are important operations.

Reasons for clutch release bearing damage

Working conditions and forces of clutch release bearings

Separate bearings are subjected to axial loads, impact loads, and radial centrifugal forces during high-speed rotation during use. In addition, due to the thrust of the shift fork and the reaction force of the separation lever not being on the same straight line, they also form torsional moments. The clutch release bearing has poor working conditions, intermittent high-speed rotation and high-speed friction, high temperature, poor lubrication conditions, and no cooling conditions.

Reasons for clutch release bearing damage

The damage of clutch release bearings is closely related to the driver's operation, maintenance, and adjustment. The reasons for the damage are roughly as follows:

Excessive working temperature leads to overheating

Many drivers often half press the clutch when turning or decelerating, and some even place their foot on the clutch pedal after shifting gears; Some vehicles have excessive free range adjustment, resulting in incomplete clutch disengagement and a semi engaged and semi disengaged state. This state causes dry friction and generates a large amount of heat that is transferred to the release bearing. The shaft bears heat to a certain temperature, causing butter to melt or dilute and flow, further increasing the temperature of the release bearing. When the temperature reaches a certain level, it burns out.

Wear and tear due to lack of lubricating oil

The clutch release bearing is lubricated with butter. There are two ways to add butter. For the 360111 release bearing, when maintaining or removing the transmission, the back cover of the bearing should be opened and filled with grease, and then the back cover should be reinstalled; For the 788611K separable bearing, it can be disassembled and immersed in melted lubricating grease, cooled and removed to achieve lubrication. In practical work, drivers tend to overlook this point, resulting in a lack of oil in the clutch release bearing. The wear of separated bearings without or with little lubrication is often several to tens of times greater than the wear after lubrication. As wear increases, the temperature will also increase significantly, making it more susceptible to damage.

Free travel too small or too many times loaded

According to the requirements, a clearance of 2.5mm between the clutch release bearing and the release lever is generally suitable. The free stroke reflected on the clutch pedal is 30-40mm. If the free stroke is too small or there is no free stroke at all, it will cause the release lever and release bearing to be in a constant engagement state. According to the principle of fatigue failure, the longer the working time of the bearing, the more severe the damage; The more times the bearing is loaded, the easier it is for the separation bearing to experience fatigue failure. Moreover, the longer the working time, the higher the temperature of the bearings, making them more prone to burning and reducing the service life of the separation bearings.

In addition to the above three reasons, whether the separation lever is adjusted smoothly and whether the return spring of the separation bearing is in good condition also have a significant impact on the damage of the separation bearing.