An Infinite-Stiffness Aerostatic Thrust Bearing

Abstract

By using an active restrictor, an infinite-stiffness aerostatic thrust bearing is realized. The active restrictor employed is called an Aerostatically Controlled Restrictor (ACR). The ACR is a kind of pressure-feedback active restrictor, therefore, electric supply is not needed for controlling the thrust bearing. The restriction gap is controlled actively by a restriction ring supported by an aerostatic ring-supporting bearing incorporated into the thrust bearing. The diameter of the bearing surface is 130 mm. The static stiffness of the aerostatic bearing can be zero for a thrust load less than 400 N. The static stiffness can also be positive or negative by changing the stiffness of the ring-supporting bearing. The step response shows that the settling time is about 5 ms. The frequency response shows that the dynamic compliance is less than 1 nm/N when the frequency of the applied load is lower than 2 Hz. The stability of the thrust bearing is 10 nm. Thus the aerostatic thrust bearing reported in this paper can be used in practice as the infinite-stiffness bearing.