A COMBINED HYDROSTATIC HYDRODYNAMIC BEARING BASED ON ELASTIC DEFORMATION

Servo cylinders with hydrostatic bearings are employed when ultimate speed, low friction, or high precision are required. These advantages are opposed by a considerable leakage loss and high costs. The latter are caused by the high component precision required in order to avoid excessive leakage and to obtain high stiffness of the bearing. In this paper an alternative concept to realize such bearings with a considerable cost reduction potential is investigated. The sleeve is made of Polyetheretherketon (PEEK). A hydrostatic difference pressure or / and a hydrodynamic pressure deforms the PEEK sleeve such that a conical stabilizing sealing gap is created. A possible mechanical design is shown and the characteristics are analysed. To study the characteristics of the bearing system the finite element suite Abaqus is used. A Reynolds User Element is developed and included into Abaqus for the simulation of the fluid structure interaction. The Reynolds equation is discretised by finite elements and solved simultaneously with the mechanical model. With the developed user element in Abaqus, static and quasi-static analyses of mechanical models (linear, non-linear or inelastic material behaviour) containing lubrications gaps can be performed efficiently. The preliminary results showed the feasibility of the concept and, generally, the potentials of plastics as a flexible material to employ elastic deformation for the creation of lubrication effects.