Hydraulic oil is the hydraulic medium used in the hydraulic system using liquid pressure energy. It plays the role of energy transfer, anti-wear, system lubrication, corrosion prevention, rust prevention and cooling in the hydraulic system. For hydraulic oil, first of all, the hydraulic device should meet the requirements of liquid viscosity at the working temperature and starting temperature, because the viscosity change of lubricating oil is directly related to the hydraulic action, transfer efficiency and transfer accuracy, but also the viscosivity and shear stability of the oil should meet the various needs put forward by different uses. There are many kinds of hydraulic oils and different classification methods. For a long time, it has been customary to classify them by use, and also according to the type of oil, chemical composition or flammability. These classification methods only reflect the income of oil products, but they are not systematic, and it is difficult to understand the relationship and development between oil products.
The hydraulic system of automobile and construction machinery uses hydraulic oil as the working medium. The flow rate of oil in this kind of hydraulic system is not large and the pressure is high, so it is called hydrostatic transmission. The quality of hydraulic oil will greatly affect the working reliability and service life of hydraulic system. Usually the quality requirements for hydraulic oil are as follows:
1) Suitable viscosity and good viscosivity and temperature performance, in order to ensure that the working temperature changes under the condition of accurate and sensitive power transmission, and can ensure the normal lubrication of hydraulic components.
2) It has good rust resistance and oxidation resistance stability, and is not easy to oxidize and deteriorate under high temperature and high pressure conditions, with long service life.
3) It has good foam resistance, so that the foam produced by the oil is easy to disappear under the working condition of constant mechanical stirring, so as to make the power transmission stable and avoid the accelerated oxidation of hydraulic oil.
