Plastic sliding bearing technology and its application in the automotive industry

The difference between rolling bearings and sliding bearings

Under a certain load and speed and without lubrication conditions, the size of the friction coefficient of rolling bearings basically depends on the manufacturing accuracy of the ball, the inner and outer rings of the bearing and the matching clearance between each other. The size of the friction force has no direct relationship with the bearing material itself. Rolling bearings generally need regular external lubricant.And under the same load and speed and no lubrication conditions, the size of the friction coefficient of sliding bearing mainly depends on the self-lubrication performance of the bearing material itself. Because the sliding bearing material itself has good self-lubrication performance, it can work for a long time without refueling or with less oil.Because sliding bearings realize the self-lubrication technology of bearings, sliding bearings can realize the characteristics of self-lubrication and maintenance-free, which determines that sliding bearings are more and more used by engineering designers. 

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Bearing from the working principle can be divided into rolling bearings and sliding bearings, rolling bearing work is a rolling friction pair, and sliding bearing work is a sliding friction pair, which determines the rolling bearing and sliding bearing working friction coefficient difference of at least ten orders of magnitude or more.

Lubrication mechanism and limit PV value of sliding bearing

Sliding bearing in the initial work, because the contact surface of the shaft and bearing that is, the working face of the bearing sliding friction, the surface can form a lubrication film to separate the surface of the moving pair, after a short-term running-in sliding friction can be greatly reduced, at this time the surface of the moving pair is not directly in contact, so it also avoids wear.Sliding bearings are widely used in engineering because of their large bearing capacity, high rotation accuracy and anti-impact effect of lubricating film.

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Factors affecting the formation of lubricating film

The formation of lubricating film is the basic condition for the normal operation of sliding bearing. The factors affecting the formation of lubricating film include lubrication mode, relative speed of moving pair, physical properties of internal lubricant and surface roughness of moving pair, etc.An important measurement index of sliding bearing performance is the maximum limit PV value that the bearing can reach. Here P refers to the load of the bearing, while V represents the linear speed of the bearing operation.The greater the limit PV value of sliding bearing, the better the service performance of the bearing and the longer the life;The main factors affecting the limit PV value of sliding bearings are the self-lubricating performance, bearing capacity and temperature resistance of the bearing material itself.The external factors that affect the actual PV value of sliding bearings are mainly the load, operating speed, ambient temperature and matching accuracy of the bearing.

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Journal bearing technology and research and development direction

Sliding bearings can be divided into metal sliding bearings and non-metal sliding bearings according to materials.Metal sliding bearings can usually be divided into composite sliding bearings, metal-based sliding bearings, etc., and non-metal sliding bearings can usually be divided into engineering plastic sliding bearings, fiber wound bearings, etc. 

Composite sliding bearings are generally composed of three layers of structure: substrate layer + copper powder layer + antifriction layer;When working, part of the lubricating materials will slowly transfer to the surface of the grinding shaft. At this time, the friction pair between the bearing friction layer and the lubricating film on the surface of the grinding shaft is established. The friction coefficient decreases while the wear rate of the bearing also decreases.Metal-based sliding bearings can be generally divided into solid lubricant inlaid sliding bearings, bimetal sliding bearings and integral sliding bearings.

Non-metallic sliding bearing is the development direction of sliding bearing technology research at present, mainly including polymer engineering plastic bearing, and fiber wound bearing, etc.The development of polymer engineering plastic bearing technology almost includes all polymer modification technologies.From the manufacturing process, it can be divided into molding sintered plastic sliding bearings and injection molding plastic sliding bearings.The molded and sintered sliding bearings are generally restricted by low efficiency and low manufacturing accuracy, so their development space is relatively small and they are not suitable for mass production. 

Polymer engineering plastics modification technology, and injection molding plastic sliding bearing technology has been the rapid development of the world, USES the advanced polymer modification, filling in the high performance polymer special lubricants and high functional fiber, high performance polymer wear-resisting role as basic material, special lubricants lubrication to reduce the friction coefficient, enhancement effect on fiber and filler.Because the whole material of high polymer sliding bearing is modified self-lubricating modified material, it is superior to the metal composite bearing in terms of friction performance and service life of the bearing (the composite bearing friction material is only about 0.03mm on the surface).At present, VIIPLUS can provide high-performance polymer plastic bearings with long-term use temperature up to 250℃, and the bearings are resistant to almost all chemical media. LIN linear bearing sliding film has a very low coefficient of friction and allows a maximum operating speed of 10m/s.At present, EPB universal and EPB3 enhanced polymer plastic sliding bearings are the most widely used in the automotive industry. 

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Application technology of sliding bearing in automobile industry

Because of the superior self-embellishing performance of sliding bearings, it has been fully reflected in the automotive industry.At present, Chinese sliding bearings are almost applied to every automobile manufacturer in the world. Especially, the application of polymer plastic sliding bearings in automobiles has been increasingly widespread. It can be used in every part of automobiles.From the simplest hinge system of the car door to the complex and demanding parts of the mechanical structure, such as the steering gear in the car steering system to the gearshift in the transmission system and so on.In addition to having excellent mechanical properties and the advantages of free lubrication and dry operation, the price of engineering plastic sliding bearings is also very low.Compared to PTFE-coated metal sliding bearings, plastic sliding bearings can be up to 50% cheaper. 

Car door hinge system due to the use of EPB3 enhanced series of plastic sliding bearings, to overcome the metal sliding bearings due to rust caused by the increase of pulling force or noise phenomenon, and in the opening and closing is the car door or trunk cover is not any moment stuck phenomenon. 

The sliding bearing used in the automobile shock absorption system is very strict in terms of wear resistance, impact resistance and matching accuracy.If the wear resistance of sliding bearing is poor, it will lead to the aggravation of the wear of the outer sealing ring, the failure of the sealing ring will lead to the leakage of the hydraulic oil and the failure of the shock absorption function. Composite bearing (DP4 material) fully accepts the challenge of this harsh condition and is successfully used in all kinds of car shock absorbers. 

Due to the adoption of RPM4 support sleeve in the car steering system, the steering wheel in the whole steering process is more stable, even in the case of road conditions are very bad, but also to ensure the normal operation of the steering system.The excellent wear resistance and shock absorption of RPM4 has been proven in automotive steering systems. 

The application of high-performance polymer EPB4 plastic bearing in automobile braking system makes the driver more stable in the braking process, and can realize fast and steady braking even in emergency situations.Whether the car is steering smoothly or in the case of emergency steering, it can also ensure effective braking.The high hardness and wear resistance of the EPB4 material results in a long service life, especially due to the addition of high-performance lubricants and functional fibers. 

Due to the large dimensional tolerances of the sheet metal material or punched holes used in automotive seat systems, and the cold sheeting steel plate, however, the minimum clearance is required in seat systems to minimize noise.In order to solve this contradiction, the engineering plastic sliding bearings produced and provided by VIIPLUS are now being used more and more. 

At present, sliding bearing has been successfully applied in civil machinery, military machinery and aerospace and other fields, with the continuous expansion of the application field and the continuous improvement of work requirements, sliding bearing material technology, manufacturing and application technology has yet to be explored, researched and improved in our practice.

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