Analysis of Damping Characteristics of Hydrostatic Air Bearing by Using One-Dimensional Bearing Model (1st Report, Damping Characteristics of a Bearing with Two Feeding Hole Restrictions)

Abstract

For the purpose of developing a gas bearing with the highest possible damping, we clarify the damping characteristics of a one-dimensional gas bearing model in relation to the squeeze number, feeding port area, restriction type and land width. The bearing has static stiffness K_st at zero squeeze number and dynamic stiffness K_dy at infinite squeeze number. Between zero and infinite squeeze numbers, we find that the damping becomes negative if K_st is larger than K_dy, and that the maximum damping is proportional to K_dy-K_st. We also find that K_dy is proportional to the static pressure. Thus, in order to increase damping, it is most effective to increase the feeding port area for both increasing the bearing static pressure, i. e., K_dy, and reducing K_st. A simple approximated formula to predict the maximum damping and associated optimal squeeze number is proposed. The limit of the potential damping ratio of gas bearings is also discussed.