Factors Affecting Gear Lubrication
Temperature: When the temperature drops, the lubricant will thicken. When the temperature rises, it becomes thinner. Therefore, a low viscosity lubricating oil is required under low temperature conditions, and a heavy oil is required under high temperature conditions to prevent dry friction between metal and metal.
Speed: The faster the sliding and turning speed, the less time it takes to squeeze the lubricant between the gears. At the same time, the lubricating oil is more likely to agglomerate and thicken under high-speed operation. Therefore: high viscosity (heavy oil) for low speed and low viscosity oil (slight oil) for high speed.
Load (pressure): High viscosity oils are more resistant to heavy loads than thin oils and prevent metal-to-metal collisions. Therefore: light loads require low viscosity lubricants, and high loads require high viscosity lubricants.
Impact load: For example, the rhythm force emitted by the engine, which requires a relatively heavy oil to prevent the boundary lubrication caused by the instantaneous fragmentation of the oil film, because only a small amount of lubricating oil can be left. In this case, a lubricating oil containing an extreme pressure additive (EP) is required.
Gear type: When spur, helical, herringbone and bevel gear pairs are used, sliding and turning create an effective film formation that slows direct contact between the engaged teeth. On non-equal shaft drives such as turbine worms and hypoid gears, the direction of relative sliding operation is not conducive to maintaining the oil film. On this transmission, boundary lubrication often occurs in a large amount. Therefore, there is still a need for still heavy oil on the turbine vortex device and the large eccentric amount of the hyperbolic gear transmission. When these transmissions are subjected to heavy loads and high pressures, it is necessary to select lubricants with high oil film properties (high viscosity), smoothness, lubricity or even extreme pressure additives.