Archive for the ‘FAG Bearings Lubrication’ tag
FAG Roller Bearings and Their Lubrication.
Purpose of the Lubrication
Lubricants are typically used to allow a moving part to slide over another part without contacting each other. The lubricant lays in-between the parts and keeps them separate. Oil lubricants have the added advantage of removing heat as they flows past a surface.At close magnification, all machine parts are manufactured with surface roughness. If two parts touch each other, the first contact is made by the high points of roughness. If one of the parts was moving, its high points would smash into the high points of the other and material would be ripped out from both.
Figure 1 shows an exaggerated representation of surface roughness.To keep moving parts, such as shafts and bearings, apart lubricant is injected between the surfaces. The lubricant puts a film between the parts so that when one moves over the other the film is wide enough to prevent contact. Figure 2 shows two parts, one of which is moving. In-between the two parts is a lubricant film that separates the high points of surface roughness in each. The parts can now move without one damaging the other.
Principles of How FAG Roller Bearings Lubrication Works
Roller bearings trap a thin lubricant film between the rolling element and the race on which they roll. The thin film keeps the two parts separated through a mechanism known as hydrodynamic lubrication.
Figure 3 shows the principle of hydrodynamic lubrication. When a lubricant film is present and one part moves over the other, the lubricant gets wedged between the two parts. The ‘wedge’ acts to squeeze the parts apart and they ride over each other on a pressurised layer of lubricant. A secondary lubrication mechanism also occurs in which the loaded part acts to squeeze the lubricant away from the supporting surface. The lubricant internal tension holds it together and presents a resistance to the squeezing action.
In the case of FAG roller bearings, as the rolling element moves along the race it creates a pressure ‘wedge’ of lubricant in front of itself. Figure 4 explains how hydrodynamic lubrication and squeeze fag bearing lubrication work together in rolling element bearings. The lubricant is a critical element in good roller bearing operation. It must retain its lubricating properties in a range of operating conditions. For it to form a layer that continually separates the parts it must be clean, it must retain its internal tension and cohesiveness, (its willingness to remain together) while still lubricating the parts.
