Development of High Stiffness Hydrostatic Thrust Bearing by Movable Land.

Hydrostatic bearings are frequently adopted on precision machines because of their high bearing performance. However, still more improvement of the bearing stiffness is required to respond to the development of precision instruments. There exist already some methods to realize high bearing stiffness such as load dependent resistors so far. In this paper, we propose a new method to achieve the higher bearing stiffness with a simple mechanism. The principle of this arrangement is to perform the bearing clearance change by the land displacement in addition to the usual shaft displacement. The bearing structure is designed so that the land moves automatically depending on the bearing load change accompanied with oil pressure variation. The properties of this bearing are analyzed and a non-dimensional variable to lead to optimum bearing design and operating conditions is derived. With the bearing performance test, infinite bearing stiffness is confirmed between load carrying capacity of 0.4 to 0.9 under the non-dimensional variable of 1.15.