In sliding bearings, a sliding movement takes place between shaft and axle. Possible bearing types are plain, unlubricated or grease lubricated plain bearings, hydrodynamic and hydrostatic sliding bearings. The sliding resistance of the bearing is dependent by solid friction, mixed friction or fluid friction.
In hydrodynamik bearings, the oil film between the shaft and the bearing is generated by the rotation of the shaft inside the bearing by a special geometry creating a pumping action inside the bearing. Mixed friction therefore prevails in these phases. Only at higher speed, a complete oil film forms and the friction is reduced.
In hydrostatic bearings external pumps fill the oil pockets of the slide bearings by high pressure with a constant oil flow. This ensures that shaft and bearing don't have direct contact at any time. Due to the constant full lubrication fluid friction is created, which is lower than the solid friction. The sliding bearings work with very little wear and tear and are extremely durable.
Due to the increased complexity of the external lubricant circuit, this type of plain bearing lubrication is used, especially in large machines. The pump technology delivers high, consistent pressure and works reliably over a long period of time.