This paper briefly introduces the structural principle and technical characteristics of the special "high pressure oil seal" for steering gear (commonly known as Deng oil seal). A new design idea to prevent the leakage of working fluid is discussed. After more than four years of practical application, it proves the advanced and reliable nature of this oil seal, and also shows that it has a very broad application prospect in the fields of hydraulic, pneumatic, lubrication, automobile and so on. This invention won the national invention patent.
Description: Special oil seal for steering gear
In 1930s, Dr. shell of Karl Froy Dembeck Company invented the world's first iron-shell cowhide oil seal for the dynamic sealing device of transmission shaft in order to solve the problem of shaft lubrication and sealing under the condition of high-speed rotation, and based on this, a lip-shaped rubber skeleton oil seal was developed. In the early 1980s, Mather and National of the United States successively developed PTFE oil seals. The successful development of these oil seals has greatly promoted the development of machinery industry and sealing technology. In hydraulic (system) devices, rubber-plastic oil seals with working pressure of 16-40kpa have been used in China, and the main types are: O-ring (NBR. FKM)； Rotary oil seals of internal and external frames (No.fkm.acm.epdm); Rotating shaft hydraulic return oil seal (No. FKM . ACM)； And (working pressure is 1-3 MPa) lip oil seal and reciprocating oil seal. However, with the rapid development of machinery industry, medium and high pressure hydraulic (system) devices (such as hydraulic engineering machinery, automobile hydraulic power steering gear, hydraulic pump, etc.) are applied. ) is more and more widely used, and the oil seal at the sealing part of the sealing (system) device often leads to the fluid working medium "crossing the boundary" because it can not meet the working conditions. Leakage can be divided into internal leakage and external leakage. Internal leakage will reduce the efficiency of the hydraulic system, which can not guarantee the required working pressure and can not work, while external leakage will lead to environmental pollution and even damage to mechanical parts. Oil seal can be divided into transmission seal and static seal, which can be distinguished according to the relative movement of the connecting part of the seal pair when the machine is running. In the long-term production practice, in order to prevent the external leakage of the dynamic seal part of the automobile hydraulic power steering gear (steering gear) more reliably (before the repair period), our company successfully developed the special "high pressure oil seal" for the steering gear.
1 background technology
(1) At present, the hydraulic seals of most automobile hydraulic power steering gears (steering gears) are skeleton lip oil seals, mostly made of rubber and plastic. Under the centripetal force of the clamping spring, the interference between the inner diameter of the lip and the outer diameter of the movable shaft is large, which will accelerate mutual wear.
(2) Rubber-plastic oil seal has corrosion resistance, high and low temperature resistance, poor friction reduction and easy aging.
(3) Under high pressure, the friction surface formed by the oil seal lip at the seal is large, and the static friction resistance is large, which is easy to cause the seal coupling to bite or creep.
2 Causes of oil leakage in hydraulic power steering gear (steering gear)
(1) The oil label for booster pump is incorrect or contains impurities; (2) The discharge valve on the booster pump is not adjusted to the correct pressure range; (3) The outer surface of the movable shaft has been worn or scraped, and corrosion spots appear. (4) Oil seals (mostly made of rubber) are resistant to high pressure, high and low temperature, wear, poor corrosion resistance, aging or lip wear. (5) The shaft sleeve is worn, the clearance of the rotary valve shaft is too large, and the radial runout is large, resulting in oil leakage of the oil seal. (6) Fatal direction: For taxis and long-distance buses, the probability is high. Turn the steering wheel to the stop point left or right to form an oil return closed loop and generate high pressure.
3 Characteristics of Deng Oil Seal
Deng oil seal is made of polymer composite material as anti-wear carrier. Compared with rubber oil seal, it has wear resistance (friction coefficient is 0.02-0.04 in the case of liquid lubrication), pressure resistance: 15Mpa (for steering gear, it is not taboo to kill the rudder, because when the oil pressure reaches 7- 14 MPa, the pressure limiting valve will automatically open) and high and low temperature resistance: 15 MPa. There is surface contact between the inner circular surface of the wear-resistant layer and the outer circular surface of the movable shaft, which hardly causes wear on the movable shaft. Under pressure, the corresponding radial interference can be obtained automatically in the radial direction of the lower lip, which is insensitive to the radial runout of the rotating (reciprocating) shaft and has good adhesion. The oil seal adapts to the maximum linear velocity of 4m/s. The corrosion resistance is better than the original rubber oil seal, and its normal service life is 1-3 times that of rubber oil seal.
4 application examples
The taxi steering gear repaired by Deng Oil Seal (E Enshi E Q84342, E Q03287, Jingmen E HT2098, E HT2096, Suzhou su E9290, Chengdu Chuan AMA353) has been used for more than 2 years, and the mileage has reached more than 400,000 kilometers (steering gear warranty, new car warranty 65438). It is enough to prove that "Deng oil seal" is far superior to other oil seals (including foreign brands) in the application field of automobile power steering gear.
5 conclusion
Orientation machine is a precise part of automobile. After years of digestion and absorption, the design, cold working and heat treatment process of orienteering machine in China have been greatly improved, but it has not kept up in the field of hydraulic sealing. From the analysis of statistical data, almost all steering gear failures are caused by oil seals, and other parts are not easy to be damaged. It can be said that the quality of oil seal is the bottleneck restricting the quality of steering gear, and the service life of oil seal is directly related to the service life of steering gear. "Deng oil seal" will certainly play an important role in building high-quality steering gear.