1. Low temperature and viscosity temperature: The opera […]
1. Low temperature and viscosity temperature: The operating temperature range of hydraulic transmission oil is very wide, generally -40 ℃ ~ 17 ℃. The function of the automatic transmission is very sensitive to the viscosity of the hydraulic transmission oil. The components that make up the automatic transmission have different viscosity requirements for the hydraulic transmission oil. From the perspective of improving the transmission efficiency of the torque converter and the sensitivity of the control system, the viscosity is low; to meet the lubrication requirements of the gears and bearings, and to reduce the leakage of the hydraulic control system and the oil pump, the viscosity of the hydraulic transmission oil cannot be exceeded. low. Therefore, the hydraulic transmission oil must take into account a variety of functions, with appropriate viscosity and good low temperature, viscosity temperature.
2, thermal oxidation stability: thermal oxidation stability of hydraulic transmission oil is an extremely important problem in use, because the hydraulic transmission oil is used at a very high temperature, such as thermal oxidation stability is not good, it will produce sludge, paint Membrane and sediment, a small amount of sediment will affect the operation of the pipeline and valve of the automatic transmission hydraulic control mechanism, and the acid or peroxide generated by oxidation in the oil will also damage the bearing and rubber sealing material. Therefore, the thermal oxidation stability of the hydraulic transmission oil is strictly required. The thermal oxidation stability of various specifications of hydraulic transmission oil is mostly evaluated by "oxidation test".
3, anti-wear or extreme pressure anti-wear: in order to ensure the long-term normal operation of the planetary gear mechanism, bearings, gaskets and oil pumps of the automatic transmission, the hydraulic transmission oil must be well lubricated. The contact surfaces of the main parts in the shifting mechanism are mostly steel and steel, steel and bronze. The hydraulic transmission oil should ensure good wear resistance to the friction pairs of different materials. The abrasion resistance of the hydraulic transmission oil is evaluated by the four-ball machine wear test, the Timken wear test and the vane pump test.
4. Adaptability to rubber materials: Hydraulic transmission oil should not excessively expand, shrink and harden the sealing materials such as nitrile rubber, propylene rubber and silicone rubber used in the automatic transmission mechanism, otherwise oil leakage and other hazards will occur. . The suitability of hydraulic transmission oils and rubber sealing materials is assessed by a rubber immersion test.
5. Friction characteristics: The clutch of the automatic hydraulic transmission shifting actuator is a wet multi-plate friction clutch. As the friction medium, the hydraulic transmission oil requires a static and dynamic friction coefficient matched with the friction plate, otherwise the shift performance will be affected.
6. Anti-foaming property: The foam generated by the hydraulic transmission oil is extremely harmful to the hydraulic transmission system. The foam reduces the transmission efficiency of the torque converter; the foam affects the accuracy of the automatic control system; the compressibility of the foam causes the hydraulic system to fluctuate and fall, and even the oil supply is interrupted.