The suitable viscosity can ensure the formation of a su […]
The suitable viscosity can ensure the formation of a sufficiently thick oil film under the dynamic pressure state of the elastic fluid, so that the gear has sufficient load bearing capacity and reduces the tooth surface wear. The gears are working in a mixed lubrication state. In the hydrodynamic lubrication state, the viscosity of the gear oil determines the thickness of the lubricating film. The viscosity of the gear oil is high, and the thickness of the elastic fluid lubricant film is large. Therefore, gear oil with higher viscosity should be used for heavy load and high impact load on the tooth surface. The viscosity index is high and the oil viscosity is high at high temperatures. It is easy to form an oil film and has high load carrying capacity. The higher the viscosity index, the smaller the viscosity changes with temperature, which ensures that a sufficient lubricant film is formed at the higher tooth surface operating temperature.
Extreme pressure wear resistance
Extreme pressure wear resistance is the most important performance of gear oil. The gear is in the transmission, the contact surface between the tooth and the tooth is not large, the pressure of the meshing part is high, any conditions are harsh, and any requirement is high. Gears that work under heavy loads are especially double-sided gears and spiral bevel gears, as well as worm gears. In order to cause scratches, gluing, pitting and wear on the tooth surface. Gear oils should have good extreme pressure and wear resistance. Under high speed, low heavy load and impact load, the gear oil should be tested to form the lubricating oil film to prevent direct contact between the gear metal working faces. . If the extreme pressure and wear resistance of the gear oil is poor, the tooth surface will be damaged by light, and the tooth surface will be scratched, peeled off, or even glued, which seriously affects the normal operation of the gear transmission mechanism.
When the two gear working faces are engaged, the working face is completely separated by the gear oil in the case of a small negative pressure. This is a hydrodynamic lubrication state, and the frictional resistance is determined by the viscosity of the gear oil. When the conforming increases, the meshing tooth surface changes elastically, the viscosity of the lubricating oil increases rapidly under pressure, and a very thin elastic hydrodynamic membrane can be quickly formed, and the friction working surface can still be separated, so that the hydrodynamic lubrication and the elastic fluid The dynamic lubrication is related to the viscosity of the green field. When the compound sentence needs to be enlarged, the convex part of the gear surface will be broken and the direct contact will occur. It is impossible to have a complete oil film between the working faces of the gear. The lubrication can only rely on the gear oil. The medium-polar molecule adsorbs one or several layers of molecules on the surface of the metal to form a convenient adsorption film, which can be formed by physical or chemical adsorption. When the high temperature and high pressure work is added, the boundary adsorption film is desorbed. At this time, the lubrication between the gear working surfaces depends on the active component of the gear oil reacting with the tooth surface metal to form a chemical reflection film softer than the metal working surface, filling The unevenness of the metal surface is that the surface is smooth, and the frictional sliding shearing motion is performed in the chemical reaction film to prevent the metal surface from being strained. The state in which the adsorption film and the reflection film are lubricated is referred to as a boundary lubrication state.
Since the high-speed operation of the gear generates a large heat, the oil temperature rises, the oxidation speed of the oil is accelerated, and the oil is deteriorated, so that the gear is worn and corroded. Therefore, the gear oil should have good oxidation stability. The gear oil is heated by the heat generated by the frictional working surface during operation, and is also exposed to the air. Water and catalytic metals are therefore easily oxidized. Gear oil will lose its original properties after oxidative deterioration, not only can not guarantee the normal operation of the gear transmission mechanism, but also the acid produced by oxidation will corrode the metal and oxidize the sludge. The paint film is deposited on the surface of the gear, and the periodontal abscess affects the normal lubrication of the gear. Therefore, the oxidation performance of the gear oil determines the service life of the oil.
The shearing effect of the gear on the gear oil caused by the operation is a change in viscosity. In particular, the viscosity index improver added to the oil is most susceptible to shearing, so the gear oil should have good shear stability. .