1. Introduction
Bearings are components that fix and reduce the load friction coefficient during mechanical transmission. Its main function is to support the mechanical rotating body, in order to reduce the mechanical load friction coefficient of the equipment during the transmission process. According to the different friction properties of moving components, bearings can be divided into two categories: rolling bearings and sliding bearings.
Most bearings add lubricating oil to ensure smooth and reliable operation, with the aim of reducing internal friction and wear, preventing burning and sticking, and extending the fatigue life of bearings; Remove frictional heat or heat transmitted from the outside; At the same time, the oil film also has a certain ability to absorb vibrations. However, a major drawback of adding lubricating oil is the need for good sealing performance, otherwise leakage may occur. Some equipment with special requirements does not allow leakage of lubricating oil. Therefore, people replaced lubricating oil with other lubricating materials and invented oil-free bearings, which not only have the advantages of bearings containing lubricating oil, but also prevent environmental pollution caused by leakage.
2. Classification
Oil free bearings mainly include gas lubricated bearings, composite material lubricated bearings, water lubricated bearings, etc.
(1) Gas lubricated bearings:
Gas lubricated bearings are sliding bearings that use gas as a lubricant. The commonly used gas lubricant for Z is air, and nitrogen, argon, hydrogen, helium, etc. can also be used as needed. The mechanism of forming a load-bearing gas film in gas lubricated bearings is the same as that in liquid lubricated bearings. Gas lubricated bearings utilize the transmission, diffusion, viscosity, thermal conductivity, adsorption, and compressibility of gases to form a complete gas film between friction pairs under the effects of fluid dynamic pressure, static pressure, and compression, which has the function of supporting loads and reducing friction.
Gas lubricated bearings are generally divided into three types: gas dynamic pressure bearings, gas static pressure bearings, and gas extrusion bearings. The actual lubrication state of bearings often exists in the form of dynamic, static pressure, dynamic, compression, static, compression, and a mixed lubrication state of dynamic, static, and compression. The mechanism of forming a load-bearing gas film in gas lubricated bearings is the same as that in liquid lubricated bearings.
(2) Composite material lubricated bearings:
Due to the requirements of special production processes, some key equipment of industrial and mining enterprises operate under extremely harsh working conditions. Due to heavy equipment, high ambient temperature, high dust or acidic corrosive gases in the air. The lubrication of equipment brings many problems, with severe friction and wear. Currently, most of them still use traditional oil and grease lubrication, but in fact, these industrial and mining conditions have exceeded the scope of oil and grease lubrication, which is prone to bearing and other friction pairs being bitten or killed, causing serious wear and damage to parts and often leading to equipment shutdown.
The composite material used in composite lubrication bearings is a new type of anti extreme pressure solid lubrication material, composed of a metal substrate and a solid lubricant paste embedded in the holes or grooves of the substrate. During the friction process, the metal substrate bears the majority of the load. Through friction, the solid lubricant in the hole or groove transfers or transfers back to the friction surface, forming a well lubricated, firmly attached, and uniformly covered solid transfer film on the friction surface, greatly reducing friction and wear. As friction progresses, embedded solid lubricants are continuously provided to the friction surface, ensuring good lubrication of the friction pair during long-term operation.
(3) Water lubricated bearings:
Since the oil resource crisis in the 1970s and the increasing emphasis on environmental protection in recent years, hydraulic transmission technology has faced severe challenges, and water lubricated bearings have gradually been promoted and applied. Water lubricated bearings use water as the lubrication and working medium, which not only saves a large amount of oil, but also avoids the environmental pollution caused by traditional bearings that use oil as the lubrication medium.
At the same time, water has advantages such as no pollution, wide sources, safety, and flame retardancy, making it an ideal lubricating medium. Moreover, it can also reduce key issues such as friction, wear, vibration, noise, and non functional wear of the friction pair. Therefore, the research on water lubricated bearings has important theoretical research and application value for improving mechanical efficiency and protecting the environment, and has become a hot topic of concern in various countries.
3. Installation instructions
(1) It should be determined whether there are any scratches, protrusions, etc. on the mating surfaces of the shaft center and shaft shell.
Is there any dust or mold sand attached to the surface of the bearing shell.
Although it is a minor collision, protrusion, etc., if any, it needs to be removed with an oil grinding stone or fine sandpaper.
To avoid scratches during installation, a small amount of lubricating oil should be applied to the surface of the shaft and shaft housing. To install the bearing on the shaft, force must be applied on the inner ring, and to install the bearing on the bearing housing, force must be applied on the outer ring. When applying force to the bearing, it is important to be careful to ensure that the force is vertical and evenly distributed downwards, as a slight impact may cause damage to the bearing. Try to avoid hitting too far.
The retainer and sealing plate of oil-free bearing bearings cannot be subjected to force. The installation method of using a hammer and sleeve is a commonly used method, as it will damage the bearings, so do not directly hit them. Be sure to hit the sleeve in the middle as shown in the picture. The hammer should be lightly tapped. In mechanical construction, when both the inner and outer rings are tightly fitted, a cushion plate should be used to ensure that force can be applied to both the inner and outer rings simultaneously. If only the inner ring is pressed with force, the force must pass through the ball and press into the outer ring, thus causing scratches on the track surface. When installing bearings with large margins on the shaft, the method of heating the bearings to 80-90 degrees in clean oil to expand the inner diameter is widely adopted.
The hardness of bearings may decrease due to overheating, so it cannot exceed 100 degrees. At this time, the bearing must be suspended with steel wire or placed on a metal wire mesh or support plate, and must not be placed at the bottom of the groove. When the bearing reaches the desired temperature (below 100 degrees), it should be immediately taken out of the groove and quickly inserted into the shaft. The bearing will shrink as the temperature decreases, and sometimes there may be a gap between the shaft shoulder and the bearing end face. Therefore, tools need to be used to press the bearing towards the shaft direction.
4. Production process and principles
Due to the requirements of production technology, some key equipment of industrial and mining enterprises operate under extremely harsh working conditions. Due to the heavy equipment, high ambient temperature, high dust or acidic corrosive gases such as CO and sulfur dioxide in the air, there are many problems with the lubrication of the equipment, resulting in severe friction and wear. So far, most of the above-mentioned domestic enterprises still use traditional oil and grease lubrication, but in fact, these working conditions have exceeded the scope of oil and grease lubrication, which is prone to bearing and other friction pairs being bitten or killed, Causing severe component wear and damage, frequently leading to equipment shutdown.
In order to produce continuous operation, in addition to requiring the installation of multiple equipment for rotating repairs in the original design, a large number of maintenance personnel need to be invested. Severely restricting the improvement of productivity, spare parts and energy consumption have become significant obstacles to the development of production. Enterprises such as automobile manufacturing, cement production, and petrochemicals have all proposed requirements for providing special lubricating materials under complex operating conditions.
Therefore, research on embedded self-lubricating composite materials has highlighted its own characteristics in material formulation and preparation process, and the material performance has reached an advanced level, solving lubrication problems under special working conditions for enterprises and bringing significant economic and social benefits. However, due to various reasons, more domestic enterprises have not yet adopted it, and the above situation still exists.
Embedded self-lubricating composite material is a new type of extreme pressure resistant solid lubricating material, composed of a metal substrate and a solid lubricant paste embedded in the holes or grooves of the substrate. During the friction process, the metal substrate bears the majority of the load. Through friction, the solid lubricant in the hole or groove transfers or transfers back to the friction surface, forming a well lubricated, firmly attached, and uniformly covered solid transfer film on the friction surface, greatly reducing friction and wear. As friction progresses, embedded solid lubricants are continuously provided to the friction surface, ensuring good lubrication during long-term operation.
5. Development direction
(1) In order to expand the scope of use of gas lubricated bearings, with the main goal of improving bearing stiffness and bearing capacity, we will develop towards the development of high stiffness gas lubricated bearings in the future.
To meet the needs of high-tech and cutting-edge technology, we are developing towards high-precision and high-performance gas lubricated bearings.
In terms of design and technology, through research on the manufacturing process, working reliability, and practicality of gas lubricated bearings, we aim to develop bearings that can be mass-produced. The bearing performance should have the characteristics of simple structure, easy manufacturing, and reliable operation on related equipment.
The research on water lubricated bearings involves multiple disciplines such as mechanical design, tribology, materials science, surface engineering, fluid mechanics, lubrication and sealing. It is a comprehensive scientific research project, and currently, research on water lubricated bearings mainly focuses on the following aspects:
Establishment of water lubrication theory for high and low friction pairs based on various types of materials;
Research on water lubricated bearing materials with self-lubricating properties and good affinity with water;
Research on the tribological mechanism of water lubrication based on surface engineering;
The verification of theory requires particularly high experimental detection methods; For composite bearings, due to the complex working conditions such as temperature, load properties, and load types, there are numerous size specifications.
How to choose and design suitable materials according to different situations is a complex problem. The development of self-lubricating bearing materials under complex working conditions such as high temperature, heavy load, low speed, lining, and corrosiveness is an urgent task.
6. Application
SF-2 boundary lubricated bearings:
Acidic polymethylglyoxal has high wear resistance. When assembling bearings with oil storage pits arranged in a regular pattern, it must be coated with lubricating grease. It is particularly suitable for rotating and swinging movements under high loads and low speeds, as well as parts that are often opened and closed under load and are not easily lubricated by fluid. Under boundary lubrication conditions, it can be used for a long time without the need for oil maintenance. Adding oil during the process can prolong the service life of the bearings, Currently applicable to metallurgical machinery, mining machinery, water conservancy machinery, automotive parts, construction machinery, agricultural machinery, etc.
Oil free self-lubricating bearings:
This product is made from a steel plate as the substrate, with a sintered spherical bronze powder in the middle layer and a mixture of polytetrafluoroethylene [ptfe] and lead rolled on the surface layer. It has the characteristics of low friction coefficient, wear and corrosion resistance, oil-free self-lubricating, and long service life. Using it can reduce costs, reduce noise, and prevent sticking and slipping. It is widely used in various sliding parts of machinery such as printing machines, textile machines, hydraulic transport vehicles, tobacco machines, pharmaceutical machinery, fitness equipment, micro motors, cars, motorcycles, etc.
Metal based embedded solid self-lubricating bearings:
It is a novel lubricating bearing that combines the characteristics of metal bearings and self-lubricating bearings. The metal matrix bears the load, and a special formula of solid lubricating material plays a lubricating role. It has the characteristics of high load-bearing capacity, impact resistance, high temperature resistance, and strong self-lubricating ability. Traditional oil bearing: Due to its advantages of low noise and self-lubricating, oil bearing has become a new favorite of computer CPU fan bearings, with high market demand; In addition, with people's increasing demand for noise, the application of oil bearings in daily household appliances is also expanding.
The basic material requirements for bearings largely depend on their working performance. The selection of materials for manufacturing rolling bearings will have a significant impact on their performance and lifespan. In general, the main form of failure of rolling bearings is fatigue peeling under alternating stress, as well as loss of bearing accuracy due to friction and wear. In addition, there are also reasons such as cracks, indentations, and rust that cause abnormal damage to the bearings. Therefore, rolling bearings should have high resistance to plastic deformation, less friction and wear, good rotational accuracy, good dimensional accuracy and stability, and long contact fatigue life. And many of these properties are determined by the combination of materials and heat treatment processes.
2023 December 5th Week Marginal Product Recommendation:
MG-CR Filament Wound Plastic Self-lubricating Bearings:
High strength glass fiber with epoxy resin baked with PTFE and special fiber as bearing lining, the back material provides high load capacity and bearing lining ouers low friction under dry condition. Therefore, this special structure ouered an outstanding anti-wear feature and anti-impact performance, suitable for high load with high corrosion resistance application like lifting machinery, logistic machinery, agricultural machinery, and port machinery etc.
