The spherical plain bearing is also called spherical plain bearing. The most typical structure is a radial spherical plain bearing composed of an outer ring with a spherical surface and an inner ring with an outer spherical surface. It has the characteristics of simple structure, small volume and large bearing capacity. Self-lubricating spherical plain bearing is a kind of spherical plain bearing with self-lubricating material. It has excellent characteristics such as small friction coefficient, long service life, impact resistance, corrosion resistance, and no need to add lubricant during the working process. It is widely used in construction machinery and trucks. , water conservancy facilities, aerospace, military machinery and other fields. Therefore, in some developed countries in the aviation industry such as the United States, France, Germany, and the United Kingdom, the research on self-lubricating spherical plain bearings started very early. The research on self-lubricating spherical plain bearings in my country started late, and the basic research is weak. Although some domestic products can replace foreign products in some fields, in general, there is still a big gap with similar foreign products in terms of product quality, performance and product serialization. , especially the self-lubricating spherical plain bearing technology used in some cutting-edge fields such as aerospace is close to blank, which has become an important bottleneck affecting my country's breakthroughs in these fields.

1 The development history of self-lubricating spherical plain bearings

Self-lubricating spherical plain bearings have been used in foreign countries for nearly a hundred years. my country only started research in this area in the 1970s, and now there is a big gap with advanced industrial countries. The performance of self-lubricating spherical plain bearings depends on the self-lubricating material, the treatment of the dual surface and the manufacturing process of the bearing. Foreign countries are far ahead in related aspects, and the technology is very mature.

1.1 Development of self-lubricating materials

Self-lubricating materials play an important role in self-lubricating spherical plain bearing technology, and the performance of self-lubricating materials directly affects the working performance and working life of self-lubricating spherical plain bearings.

The early self-lubricating spherical plain bearings prepared a lubricating film on the sliding surface to achieve the effect of reducing friction. For example, ELGES and NTN companies first conducted research in this regard. They coated the inner spherical surface of the outer ring or the outer spherical surface of the inner ring with a PTFE coating. , Prepare spherical plain bearings with small friction coefficient and high wear resistance.

SKF has developed a self-lubricating spherical plain bearing inlaid with solid lubricating material on the inner surface of the outer ring. This kind of spherical plain bearing has a small friction coefficient. Now this kind of self-lubricating spherical plain bearing is still used in some fields.

In 1955, White. Charles S and others in the United States invented a fabric-type self-lubricating material. This composite woven material is composed of fibers with low friction coefficient and other fibers, and the woven material is bonded with suitable materials. Since the base material is required to have the ability to resist deformation at higher operating temperatures, thermosetting resins are selected. Since the low-friction fiber material generally has poor adhesion, the weaving method is used to make most of the anti-friction fibers on the working surface of the pad, and at the same time make the fibers with better adhesion on the bonding surface. This kind of lubricating material At the same time, it has good anti-friction and bearing capacity. In addition, this braided lubricating material has strong designability, and a suitable braiding method can be adopted according to specific working conditions, and suitable braiding materials and matrix materials can be selected. This design idea is still one of the most basic design ideas of self-lubricating gaskets for self-lubricating spherical plain bearings.

In 1956, White. Charles S woven tetrafluoroethylene fibers and adhesive fibers into bearing lubricating materials, and filled them with adhesive resin sources to make fabric-type composite materials.

In 1958, Richard et al. also proposed a braided lubricating material. Braided self-lubricating liner is the main self-lubricating material for self-lubricating bearings at present, especially in cutting-edge fields such as aerospace and aviation. Perfect, forming a series of products that can adapt to a variety of working conditions, SKF's new self-lubricating liner used in its newly launched TX self-lubricating spherical plain bearing improves the performance of the self-lubricating liner by improving the fabric structure and base material. This self-lubricating liner has greatly improved the load-bearing, anti-wear, anti-friction and anti-moisture properties, as well as the working life of the liner, which makes the performance of TX self-lubricating spherical plain bearings compared with previous similar products and other company products. greatly improved. RBC's new self-lubricating liners with excellent performance are suitable for different working conditions such as high-speed light load, low-speed heavy load, high temperature, low friction, etc., and are also suitable for forming friction surfaces with steel, aluminum, titanium, etc. In general, foreign braided self-lubricating liners have been serialized and are suitable for applications under different working conditions (low speed and heavy load, high speed and high temperature, etc.).

Because the fabric structure self-lubricating liner is complicated and expensive, it also promotes the research on non-woven self-lubricating materials, especially injection-molded self-lubricating materials. In 1978, McClos key Albert R invented a PTFE fiber and phenolic resin non-woven self-lubricating gasket. In 2005, Ampuero Auza.Jamime A et al. invented a non-woven self-lubricating liner composed of fluoropolymer fibers and other wettable organic structural fibers. It can adapt to higher speeds and has a longer working life.

At present, the self-lubricating liners commonly used in the mass production of spherical plain bearings include fabric-type self-lubricating liners and injection-molded polymer anti-friction and anti-wear materials, as well as sintered porous materials (such as sintered bronze, which store lubricating oil or grease in the holes), Copper mesh-plastic composite materials, etc. These two types of self-lubricating liners are mainly used in civil machinery and equipment with low load and low transmission requirements.

In China, relevant universities, research institutes and enterprises have also done some research on woven structure self-lubricating gaskets. Fujian Longxi Bearing (Group) Co., Ltd. has not started to develop PTFE fabric self-lubricating materials since the 1980s. The load capacity exceeds 450MPa, the carrying capacity exceeds 200MPa, and the lowest friction coefficient reaches 0.03 under heavy load and low speed, and the performance index is at the leading domestic level.

In recent years, some domestic scholars have achieved certain results in the research of non-woven self-lubricating materials and their application in bearings, which have improved the bearing capacity, friction coefficient reduction, PV value limit, service life and other properties to varying degrees. . However, the research work on self-lubricating gaskets used in cutting-edge fields is still weak.

1.2 Development of Surface Treatment Technology

The self-lubricating gasket is generally pasted on the inner spherical surface of the outer ring of the spherical plain bearing, and the outer spherical surface of the inner ring is generally treated with special processes, such as chrome plating, ion implantation, ceramicization, etc., so that the self-lubricating gasket and the outer spherical surface of the inner ring form a friction pair , more excellent working performance can be obtained. The material of the inner ring of the self-lubricating spherical plain bearing can be stainless steel, aluminum alloy, and titanium alloy. The use of titanium alloy in the inner ring of self-lubricating spherical plain bearings can reduce the weight. Since the hardness of titanium alloy is lower than that of stainless steel and copper alloy, the outer spherical surface of the inner ring is more easily scratched during the working process, and the damaged outer spherical surface also accelerates the damage of the self-lubricating gasket. and wear. To this end, in 2005, Smith et al. proposed surface treatment on the outer spherical surface of the inner ring of the titanium alloy to form a nitride infiltration layer, and the surface roughness was reduced to less than 18 nm through processing; in 2006, Lopes et al. A TiN treatment layer is formed on the outer spherical surface of the inner ring. In order to improve the performance of self-lubricating spherical plain bearings, some scholars have proposed to use ceramic materials for the inner ring, so that the working pair formed with the self-lubricating gasket has better performance.

The material of the inner and outer rings of SKF self-lubricating spherical plain bearings for aviation is stainless steel, the outer ring is cold-extruded, the inner spherical surface of the outer ring is adhered with a PTFE fabric liner, and the outer spherical surface of the inner ring is treated with ceramic coating. The spherical plain bearing has higher bearing capacity and longer life.

2 Self-lubricating spherical plain bearing test

The main failure form of self-lubricating spherical plain bearings is wear. Therefore, it is a basic work to carry out the performance test of spherical plain bearings and study the friction and wear performance of spherical plain bearings. Can also play a guiding role in use.

A lot of work has been done in test methods, test equipment research and testing in China, but there is still a certain gap with foreign countries. There is still a lack of test machines with combined loading and combined motion. The test work, the test development is not enough, and the theoretical research is not deep enough.

2.1 Test method

The tests of spherical plain bearings mainly include static load test, dynamic load test, high temperature test, low temperature test, medium resistance test, etc. In China, the national industry standard drafted by Fujian Longxi Bearing (Group) Co., Ltd. The load test regulations, the dynamic and dynamic load and life test regulations of the spherical plain bearing; the technical specifications of foreign American navigation marks and EU navigation marks all stipulate the static load and dynamic load test of the spherical plain bearing.

2.2 Test equipment

The test equipment for spherical plain bearings mainly includes static load and dynamic load test equipment. The static load test equipment is generally transformed from a universal material testing machine, while the dynamic load test equipment needs to be specially developed. At present, there are constant load testing machines and alternating load testing machines. testing machine, combined motion and loading testing machine, and testing machine that can simulate high and low temperature, dust, water vapor and other environments. Fujian Longxi Bearing (Group) Co., Ltd. has invested a lot in test equipment. It has built a laboratory approved by CNAS, and has life performance of various types of spherical plain bearings under constant load, alternating load, high and low temperature, dust, and water vapor simulation environment. The test equipment can measure the friction coefficient, wear amount, temperature and other performance indicators online, and automatically draw the curve of friction and wear performance indicators and movement time. It is the most complete and largest spherical bearing performance laboratory in China, and has carried out a large number of spherical bearing life. A performance test test.

2.3 Analysis technology of friction and wear surface of self-lubricating spherical plain bearings

The friction and wear analysis techniques of self-lubricating spherical plain bearings mainly include surface and structure analysis and surface and atomic state analysis. Surface and structure analysis mainly uses transmission electron microscope and scanning electron microscope to observe the morphology and damage characteristics of the friction surface; use electron diffraction technology and X-ray diffraction technology to determine the surface structure and composition. The surface and atomic state analysis mainly includes Auger electron spectroscopy, photoelectric spectroscopy, scanning probe microscopy, scanning tunneling microscopy, atomic force microscopy, etc. to analyze the composition and distribution of the friction surface.

3 Conclusion

Self-lubricating spherical plain bearings have been used in many fields because of their large load capacity, light weight, no need for artificial lubrication, and excellent wear performance and friction torque. Since the domestic research level of it is not high, it is believed that with the gradual maturity of this product, the research work will become more and more in-depth, and self-lubricating spherical plain bearings will also be widely used.

The experimental research of spherical plain bearings is very important, which can prompt the friction and wear mechanism of spherical plain bearings, analyze the forms of friction and wear, accumulate the basis for the performance improvement and improvement of spherical plain bearings, and play a guiding role for the application of spherical plain bearings. Invest in and carry out in-depth experiments.