Shaft member for fluid dynamic bearing device and manufacturing method for shaft member

Abstract

Grinding is performed on an outer peripheral surface of a shaft member while rotationally driving the shaft member under a state in which both end surfaces of the shaft member are sandwiched between a pair of support portions. A convex surface is formed on one axial end surface of the shaft member or an end surface of one of the pair of support portions, and a flat surface is formed on the other of the one axial end surface of the shaft member and the end surface of the one of the pair of support portions. The flat surface and an apex of the convex surface are brought into contact with each other to support one axial end portion of the shaft member.

1 - 7 . (canceled) 
     
     
         8 . A fluid dynamic bearing device, comprising:
 a shaft member;   a bearing sleeve having an inner periphery on which the shaft member is inserted; and   a radial bearing portion support the shaft member by dynamic pressure of a film of an oil filled into a radial bearing gap between an outer peripheral surface of the shaft member and an inner peripheral surface of the bearing sleeve,   wherein a convex surface is formed on an end surface on one axial end side of the shaft member.   
     
     
         9 . The fluid dynamic bearing device according to  claim 8 , wherein the convex surface of the shaft member does not slide in contact another member. 
     
     
         10 . The fluid dynamic bearing device according to  claim 8 ,
 wherein the shaft member comprises:
 a shaft portion having the convex surface; and 
 a flange portion provided on an end portion on another axial end side of the shaft member, 
   the fluid dynamic bearing device further comprises:
 a tubular housing having an inner peripheral surface on which the bearing sleeve is fixed; 
 a lid member closing an opening portion of the housing on the another axial end side of the shaft member; 
 a first thrust bearing portion support the shaft member by dynamic pressure of a film of the oil filled into a thrust bearing gap between one end surface of the flange portion of the shaft member and an end surface of the bearing sleeve; and 
 a second thrust bearing portion support the shaft member by dynamic pressure of a film of the oil filled into a thrust bearing gap between another end surface of the flange portion and an end surface of the lid member.