Method for assembling bearing of spindle motor

Abstract

A method for assembling a bearing structure is provided. The bearing structure includes a housing of a cylindrical shape with one closed end, made up of a cylindrical portion and a cap portion. The method includes the steps of inserting a shaft integrated with a rotor hub into a sleeve and fixing a stopper member to the distal end of the shaft so as to make a hub assembly, inserting the sleeve into the housing, exerting a force on the sleeve to move toward the bottom of the housing until an end surface of the sleeve abuts the stopper member, pulling one of the housing and the hub assembly from the other relatively in the axial direction by a predetermined distance, and fixing the sleeve to the housing.

1 . A method for assembling a bearing of a spindle motor, the bearing comprising: 
 a housing of a cylindrical shape with one closed end, made up of a cylindrical portion and a cap portion for closing one end of the cylindrical portion;    a sleeve of a hollow cylindrical shape fixed to the inner surface of the housing;    a shaft inserted in the sleeve in a rotatable manner;    a rotor hub having substantially a disk shape formed integrally with the shaft and connected to the proximal end of the shaft at the middle portion; and    a stopper member fixed to the distal end of the shaft so as to be positioned at the bottom side of the housing, wherein    a radial gap is formed between the sleeve and the shaft, and an axial gap is formed between the opening end surface of the housing and the rotor hub as well as between the stopper member and an end surface of the sleeve, the method comprising the steps of:    (a) inserting the shaft integrated with the rotor hub into the sleeve and fixing the stopper member to the distal end of the shaft so as to make a hub assembly;    (b) inserting the sleeve into the housing;    (c) exerting a force on the sleeve to move toward the bottom of the housing until an end surface of the sleeve abuts the stopper member;    (d) pulling one of the housing and the hub assembly from the other relatively in the axial direction by a predetermined distance; and    (e) fixing the sleeve to the housing.    
   
   
       2 . The method according to  claim 1 , wherein the housing is formed to have a wall thickness that is thinner at the cap portion than at the cylindrical portion.  
   
   
       3 . The method according to  claim 1 , wherein lubricating oil is kept between the opening end surface of the housing and the rotor hub so that a thrust fluid dynamic pressure bearing is formed.  
   
   
       4 . The method according to  claim 1 , wherein lubricating oil is kept between the opening end surface of the housing and the rotor hub as well as between the stopper member and the end surface of the sleeve so that thrust fluid dynamic pressure bearings are formed.  
   
   
       5 . The method according to  claim 1 , wherein the step (b) includes inserting the sleeve into the housing until the opening end surface of the housing abuts the rotor hub, and the step (d) includes pulling one of the housing and the hub assembly from the other relatively in the axial direction by a distance that is equal to an axial gap between the opening end surface of the housing and the rotor hub plus an axial gap between the stopper member and an end surface of the sleeve after assembling.  
   
   
       6 . The method according to  claim 1 , wherein the sleeve is made of a ferromagnetic material or a material containing a ferromagnetic material, and the step (c) includes placing a magnet outside the bottom of the housing so as to exert the force on the sleeve.  
   
   
       7 . The method according to  claim 1 , wherein the step (c) includes applying an inertial force to the housing and the hub assembly as a lump so as to exert the force on the sleeve.  
   
   
       8 . The method according to  claim 1 , wherein the step (b) includes applying an adhesive to the outer surface of the sleeve or the inner surface of the housing before inserting the sleeve into the housing, and the steps (c) and (d) are performed before the adhesive is cured, and the step (e) includes curing the adhesive to fix the sleeve to the housing.  
   
   
       9 . The method according to  claim 8 , further comprising the step, between the steps (d) and (e), of curing a part of the adhesive between the outer surface of the sleeve and the inner surface of the housing as temporary fixing.  
   
   
       10 . The method according to  claim 8 , wherein the step (b) includes applying an adhesive that is cured in a short time for temporary fixing to a part and applying an adhesive that is cured in a long time to the other part of the outer surface of the sleeve or the inner surface of the housing.  
   
   
       11 . The method according to  claim 1 , further comprising the step, after the step (e), of filling lubricating oil in a space including a radial gap formed between the sleeve and the shaft and an axial gap between the opening end surface of the housing and the rotor hub as well as between the stopper member and an end surface of the sleeve.  
   
   
       12 . The method according to  claim 9 , further comprising the step, after the step (e), of filling lubricating oil in a space including a radial gap formed between the sleeve and the shaft and an axial gap between the opening end surface of the housing and the rotor hub as well as between the stopper member and an end surface of the sleeve.