Fluid bearing device

Abstract

A spindle motor comprises a hollow shaft 13 having one end formed with a thrust plate 15, and a sleeve 12 provided to face the shaft 13 through a radial fluid bearing clearance R therebetween, wherein a thrust fluid bearing S is formed between the opposite flat surfaces 15 s of the thrust plate 15 and the sleeve 12 facing the flat surfaces 15 s. In addition, the hollow shaft 13 has a connection portion 30 at the lower end formed in a concave shape, such that the thrust plate 15 is guided by the inner peripheral surface of the connection portion 30 such that it is coaxial with the shaft 15, and fixed to the shaft 13 by fitting the cylindrical portion 20 b of a set screw 20 to the through hole 15 b of the thrust plate 15 and the connection portion 30.

What is claimed is:  
     
         1 . A fluid bearing device comprising a hollow shaft having one end formed with a connection portion and a thrust plate, the thrust plate having at least one flat surface, wherein a thrust fluid bearing is formed between the at least one flat surface and a mating member facing the at least one flat surface, and a sleeve provided to face the shaft through a radial fluid bearing clearance therebetween, the connection portion being formed in one of convex and concave shapes, and the thrust plate being guided by the connection portion such that it is coaxial with the shaft, and fixed through screw-tightening to a threaded hole extending through the shaft.  
     
     
         2 . The fluid bearing device of  claim 1 , wherein the threaded hole extending through the hollow shaft functions as a thread hole for clamping to fix to the hub an article to be mounted.  
     
     
         3 . The fluid bearing device of  claim 1 , wherein the thrust plate is formed in a disk shape to have a center formed with a through hole, and has a thickness up to 1.5 mm, and the thrust plate has opposite flat surfaces in which grooves for generating dynamic pressure are formed with the depth up to 12 μm by way of coining process.