The sintered plain bearing is one of the oldest products of powder metallurgy. Sintered plain bearings have proven themselves in all areas of technology for decades. Their good bearing properties are determined by the high manufacturing precision and the porosity of the sintered material. These two characteristics are of particular importance for the function as a self-lubricating plain bearing.

A wear-free sliding movement can only occur if a lubricant separates the moving surfaces. A good bearing therefore depends not only on the properties of the bearing metals, but also on the lubricant, which must be in the right place at the right time to separate the moving surfaces.

The supply of lubricant and the formation of the lubricating film are therefore crucial for the function of the plain bearing. With solid bearing metals, it is necessary to provide lubricant feeds to the bearing location and holes, grooves and pockets in the bearing to guide the lubricant to, or hold it where it is needed.

Our sintered plain bearings are characterized by their permeable pore space – space for the impregnation and flow of liquid lubricants and for filling with solid lubricants. The system of interconnected pores ensures that the liquid lubricant reliably reaches where it is supposed to be effective – in the bearing gap. The shaft and bearing are circular, but differ slightly in their diameters; this creates what is known as bearing clearance. The fact that the shaft and bearing do not have a common center creates a wedge shape for the lubrication gap. The lubricant is carried along by the moving part of the bearing in such a way that a flow in the same direction is established.

As the sketches show, a hydrodynamic system is created so that the lubricating wedge is filled with lubricant without the need for any force other than the start of the rotary movement.

These sintered plain bearings are therefore a simple, maintenance-free design element with high functional reliability and performance as well as good emergency running properties.

When still, the shaft rests against the wall of the oil-filled plain bearing. At the point of contact between the shaft and the bearing, a small oil deposit forms due to capillary action and elastic deformation of the bearing, which assists the start of the shaft movement.

In the operating state, the resulting displacement creates a lubricating wedge under pressure. Within the pressure peak, the porous bearing shell is completely filled with oil. The pressure gradient within the bearing shell causes oil to equalize. Oil flows within the bearing shell to the areas not under pressure, from where it re-enters the lubricating chamber.

When the bearing is stopped again, the oil in the lubrication chamber is drawn back into the porous bearing shell by capillary action.