Research on Sealing of Hydraulic Shock Absorber Jin Jingyun, Ren Maolin, Zhang Yun, Zheng Jianyun, Shen Jianguo (Institute of Locomotive and Rolling Stock Technology, Ministry of Railways, Changzhou 213011, China) With the improvement of the running speed of locomotives, the safety and reliability of railway transportation are particularly Important hydraulic shock absorbers are important components of rolling stock and play an important role in improving the running quality of rolling stock, reducing vibration and extending the life of components. At present, the technical performance of the domestic damper can not meet the requirements of the speed-increasing passenger car, which restricts the development of railway technology. The main reason and analysis of the damper failure. 1.1 The main reason for the failure of the current railway hydraulic damper technology is from the former Soviet Union. The technical model developed, this type of hydraulic damper is designed for locomotives with a speed of less than 80km per hour. It cannot meet the needs of higher speed locomotives. According to the DFn of the Shanghai Locomotive Depot in early 1997. According to the statistics of diesel locomotives, 23 domestic hydraulic dampers were replaced due to early failure during the 7-month operation, of which 20 were vertical and lateral oil dampers, accounting for 87% of the total replacement, the shortest time. The three lateral hydraulic dampers and one vertical hydraulic damper only used one minor repair period (30,000 km). According to statistics, in the failed hydraulic damper, the failure due to oil leakage More than 95% of oil leakage is the main cause of failure of hydraulic shock absorbers.
1.2 Failure Cause Analysis The hydraulic damper that failed after disassembly inspection found that the piston rod seal was worn or missing, the piston rod and guide sleeve were worn, and the chrome plating of the piston rod was peeled off. Obviously, the pair of friction pairs of the piston rod and the seal are not matched. According to the test report of the dynamic performance of the speed-up locomotive provided by the Ministry of Railways, the main characteristics of the damper after the speed increase are the high frequency and low amplitude. The vibration superimposed components are significantly more, which is extremely unfavorable to the life of the damper piston rod seal. The friction lubrication mechanism shows that when the motion starts and the movement speed is very low, it is too late to form a lubricating film, the seal and the piston rod In the case of dry friction or boundary friction: 2000-04-26 Fund Project: Ministry of Railways Science and Technology Development Plan (9717) rubbed state, the seal is extremely easy to grind when running at a low speed, the elastic connection at both ends of the hydraulic shock absorber is relatively misaligned It is not large, and the lateral force is small when the reciprocating motion is in the axial direction. The vibration frequency is low, and the impact load is small. When the vehicle speed is increased, the relative between the wheel pair and the bogie frame, between the bogie frame and the vehicle body. The large amplitude of movement makes the relative misalignment between the elastic joints at both ends of the oil damper installed between them large, that is, the lateral force of the oil damper is large, the piston rod seal and
The domestic hydraulic damper seals are made of oil-resistant rubber and have poor wear resistance. According to the relevant information, even in the case of good lubrication conditions, it can not meet the life expectancy of the damper. The design of the seal structure can not meet the requirements. The wear of the seal is inevitable during the use of the damper. Therefore, In the design, the compensation problem after the seal wear must be considered. The practical application shows that the domestic hydraulic damper seal structure can not meet the matching requirements of the friction material process. The piston rod material of the domestic hydraulic damper friction pair adopts 45 steel The surface is chrome-plated, the surface roughness is large, and the seal is made of cyanide rubber. According to the test, it is difficult to meet the requirements. The geographical environment of China is very large, and the temperature is as low as -40 °C (the international train temperature is lower). , up to 40 ° C, temperature difference of 80 ° C, which puts high requirements on the viscosity and oil properties of the oil, the lubricating properties and the adaptability of the sealing material. The lubrication performance of the oil is good, and the seal and the piston rod are rubbed. The wear resistance of the secondary has a great influence. If the oil has good adaptability to the sealing material, the anti-aging time of the sealing member can be prolonged. Most of the domestic hydraulic shock absorbers use transformer oil, and the performance indexes of the oil are difficult to meet the requirements of the speed-up locomotive. 2 The new hydraulic damper seal friction vice research can be seen through the above analysis, to solve the vibration reduction The leakage problem of the seal friction pair must be studied from the design and material process 2.1 high frequency and low amplitude vibration in the design.
The optimum surface roughness range is 0. åŸm0.2m should adopt the wear self-compensating sealing structure.
Pressure damper piston rod follower rubber corrugated coring seal pseal) sealing structure design adopts the scheme, which is characterized by the use of two seals, the first passage is the seal seal combination, which utilizes the high elasticity of the rubber O-ring Wear-compensation and low friction and high wear resistance of PTFE filling, prolong the service life of the friction pair. The second channel is the follower and the rubber bellows. When the piston rod vibrates at high frequency and low amplitude, The follower vulcanizes on the rubber bellows with the rubber bellows. At this time, there is no relative motion between them, only low frequency with few times and less probability; when the large vibration exceeds a certain range of displacement, the limit cover limits The movement of the follower prevents the follower rubber bellows from being fatigued and broken by the tensile force, so as to generate relative motion, thereby avoiding the relative high frequency and low amplitude vibration between the piston rod and the seal, and reducing the seal. Wear and tear.
There are generally three types of seals between: (1) direct contact between steel and steel between piston and cylinder liner; (2) seal between piston and cylinder liner with piston ring; (3) seal between piston and cylinder liner Ring, guide ring seal (see) We adopt the third scheme, which is characterized by small friction factor, wear resistance, less leakage, long service life of friction pair. 2.2 Material technology The sealing material should be low friction and wear resistant material.
The special treatment of the surface of the piston rod requires better wear resistance and self-lubricating of the surface of the piston rod. 2.2.1 Materials and processes of the piston rod Considering the wear angle, the piston rod should have wear resistance and corrosion resistance. The main factors affecting the wear resistance of the friction pair between the piston rod and the seal are: (1) Surface roughness of the sliding surface The roughness of the sliding surface has an optimum range of influence on the wear resistance. Too large or too small is not conducive to the wear life of the friction pair, and the optimum range value varies with the state of material movement between the friction pairs. Through relevant experimental research, it is concluded that the friction coefficient between the friction state of the friction pair and the friction of the steel friction is much greater than the friction coefficient of the fluid friction, and the wear life of the dry friction is much smaller than that of the fluid friction. Grinding life.
The lubricating oil of the damping oil has good compatibility with the sealing material and can improve the wear life of the sealing member.
Self-lubricating properties of piston rod materials According to relevant research, a layer of nickel-based alloy (nickel-chromium borosilicate) is sprayed on the surface of the piston rod, and the wear resistance is several times that of the chrome-plated piston rod. The structure of the nickel-based alloy layer is Y. -Ni solid solution NisBCrBCmG, CnG and other compounds, microscopic 1060, soft matrix (nickel based) dispersed with high hardness compound hard spots, is a porous structure, this structure is excellent in self-lubricating, sealing The material has good wear resistance. For this purpose, the surface of the piston rod is sprayed with a layer of nickel-based alloy material, the thickness of the sprayed layer is 0.2mm, and the surface roughness ranges from 0. åŸm~0.2Mm 2.2.2 The material of the cylinder tube The material of the process cylinder is made of steel No. 35 or No. 20. The inner hole of the pressure cylinder adopts the honing or rolling process. According to the friction and wear mechanism and the test result, the value of the surface roughness of the inner hole after honing or rolling is required to achieve the best matching test. The optimal value range is Q1um~ 0.3m 3 new hydraulic damper seal test evaluation shock absorber seal test assessment points endurance test and loading test.
The purpose of the endurance test is to conduct a durability test on the sealing performance and life of the new hydraulic damper. The test was carried out on a self-developed fatigue test bench. The test program was: amplitude 4mm, frequency 5Hz~15Hz after 22<106 times, 6.6 piston rod and dust ring 1.2< 1C7 test size 35-i2mm Leakage refers to the presence or absence of leakage after an endurance test for 24 hours.
★ As well, no wear and tear, no leakage; ▲ is good, slightly worn, slightly deformed.
Table 2 Shock Absorber Loading Test Record Table Shock Absorber Vehicle Shock Absorber Seal (6 months later) Joint and other damping properties Traveling kilometers leaking with live rubber to connect its asymmetry rate Model No. No. No. 6 loadings of 3 6 (6 months oil heads before and after the month before the month) No good, no wear, no aging, no good, no wear, no aging, no good, no wear, no aging, no good, no wear, no aging. Normal, no good, no wear, no aging, normal, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no. No wear, no aging, normal, no good, no wear, no aging, no good, no wear, no aging, no normal, no wear, no aging, no normal, no wear, no aging, no normal, no wear, no aging, normal, similar, imported oil damper. Advanced level, can replace imported products.
(2) The annual demand shock absorbers of the whole road are about 30,000. According to the average import price of more than 3,000 yuan per year, it is necessary to import hundreds of millions of yuan per year from abroad. Therefore, the development of the new hydraulic shock absorber has been successful. It can reverse the current situation of large-scale import of shock absorbers, which can save a lot of foreign exchange for the country and has significant social and economic benefits.
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