What are the lubrication methods of the gearbox?

Just like other rotating equipment, gearboxes rely on lubrication to reduce friction, as well as cooling functions to achieve good operation and longevity. For the type of lubrication used and the typical lubrication cycle, the gear manufacturer will provide recommendations. However, in fact, the requirements for gearbox lubrication depend on the environmental conditions to which the gearbox is exposed, whether it is properly maintained, and whether it is overloaded.
Grease lubrication:
　Suitable for low-speed operation, but compared to oil, it provides less cooling. Moreover, this is not recommended for continuous operation or heavy load applications, or even at low speeds.
　When performing lubrication, it is very important to use the right amount of lubrication, and for that, it is very important. Using too little grease will hinder the formation of a lubricating film, but too much lubricating oil-especially grease-will increase viscous resistance and power loss.

Oil splash lubrication:
This is usually used for helical gears, spur gears and bevel gear reducers. This method is also called an oil bath. Because it uses a fuel tank filled (or partially filled) with oil. When the gears rotate, they enter the oil bath. And splash the oil into other gears and bearings. But if the gear teeth are completely submerged, a condition called "stirring" occurs.
Essentially, agitation refers to when the gears or bearings must work hard to "inject" lubricant. An image metaphor is to take a walk along the edge of the beach. It is relatively easy to walk when the height of the water is only at the bare feet. But if the height of the water is higher than the knee, then it takes more effort to walk.
The effectiveness of splash lubrication largely depends on the speed of the gears. A general rule of thumb is that in order to make splash lubrication effective, the tangent velocity should be at least 3 m/s.
Forced oil lubrication:
For high-speed applications, forced oil lubrication is the first choice. Among them, including oil mist, oil spray, oil droplets. In the oil mist method, the oil is atomized so that it penetrates all areas of the gear. And other internal structures.
In contrast, the oil spraying method is a method of directly applying lubricating oil to gears or other parts. However, this method is not always very effective. Because high centrifugal force will affect the direction of oil spray.
The dripping method is to directly pump or "drip" the oil into the required surface. A pump draws lubricating oil from the oil tank, and then transfers the oil into the gears or bearings through the internal pipeline system. Such a method is usually the splash (also known as oil bath) method, and some parts may be difficult to be infiltrated by oil through the splash method.
Regardless of the lubrication method used, it is very important to select the appropriate type of lubrication for the performance of the gearbox. When choosing the parameters involved in the lubricant, viscosity is the most important.
The viscosity of a lubricant is too high for the application (that is, the lubricant is too "viscous") and will not flow effectively. Because the gear teeth protect the meshing surface and provide cooling. But providing lubrication with too low viscosity will not be able to provide an effective thickness of the film to prevent metal collisions between the contact surfaces.

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