Rotating device and a method for manufacturing a rotating device

Abstract

In a rotating device, a recording disk is mounted on a hub. A base rotatably supports the hub via a bearing unit. A core is fixed to the base with a ring portion and a plurality of teeth, with coils wound there around. The bearing unit includes a cylindrical portion that surrounds a radial dynamic pressure groove. The base includes an integrated surrounding portion protruding toward the hub, with the ring portion glued there around. The base further includes an integrated increasing-thickness portion arranged outside of the surrounding portion such that the increasing-thickness portion becomes thicker the closer it is to the surrounding portion. The cylindrical portion is surrounded by the surrounding portion, the surrounding portion is surrounded by the increasing-thickness portion, and a surface of the increasing-thickness portion at least partly overlaps the radial dynamic pressure groove in the axial direction.

What is claimed is: 
     
         1 . A rotating device, comprising:
 a hub on which a recording disk is to be mounted;   a base rotatably supporting the hub via a fluid dynamic bearing unit; and   a core fixed to the base, the core having a ring portion and a plurality of teeth that radially extend from the ring portion;   coils wound around the plurality of teeth, wherein   the fluid dynamic bearing unit includes a cylindrical portion that surrounds a radial dynamic pressure groove,   the base includes a surrounding portion that protrudes toward the hub, the surrounding portion being guided through a central hole of the ring portion of the core, the ring portion of the core being glued to an outer circumference of the surrounding portion, and the fluid dynamic bearing unit being inserted into and glued in a bearing hole formed on an inner surface of the surrounding portion,   the base further including an increasing-thickness portion arranged continuously and radially outwardly of the surrounding portion such that the less the distance between a part of the increasing-thickness portion and the surrounding portion is, the thicker the part of the increasing-thickness portion becomes, the surrounding portion and the increasing-thickness portion being integrated in the base, and
 the cylindrical portion surrounding the radial dynamic pressure groove is surrounded by the surrounding portion, the surrounding portion is surrounded by the increasing-thickness portion, and, given that axial coordinates are defined in an axial direction along a rotating axis of the hub, a range of the axial coordinates of a surface of the increasing-thickness portion toward the hub at least partly overlaps a range of the axial coordinates of the radial dynamic pressure groove. 
   
     
     
         2 . The rotating device according to  claim 1 , wherein the coils are formed so that a distance between the coils and the increasing-thickness portion is greater than a predetermined distance. 
     
     
         3 . The rotating device according to  claim 1 , wherein the coils have a decreasing-thickness portion, the thickness of which decreases in accordance with a profile of the increasing-thickness portion. 
     
     
         4 . The rotating device according to  claim 1 , wherein the increasing-thickness portion is formed so that the hub maintains a predetermined height even if a test impact load of 1200 G is applied. 
     
     
         5 . The rotating device according to  claim 1 , wherein the increasing-thickness portion is formed so that the following equation is satisfied: 
       
         
           
             
               
                 
                   
                     
                       
                         H 
                          
                         
                           ( 
                           x 
                           ) 
                         
                       
                       
                         H 
                         0 
                       
                     
                     ≥ 
                     
                       
                         k 
                          
                         
                           ( 
                           
                             x 
                             
                               x 
                               0 
                             
                           
                           ) 
                         
                       
                       
                         - 
                         1.2 
                       
                     
                   
                 
                 
                   
                     ( 
                     
                       equation 
                        
                       
                           
                       
                        
                       1 
                     
                     ) 
                   
                 
               
             
           
         
         where x is a distance between a part of the increasing-thickness portion and a rotational axis of the hub, x 0  is a predetermined reference distance, H(x) is a thickness of the increasing-thickness portion at the distance x, H 0  is a predetermined reference thickness, and k is a predetermined constant. 
       
     
     
         6 . The rotating device according to  claim 1 , wherein the base has a coil-facing portion arranged to be adjacent to the increasing-thickness portion, which is located outside of the increasing-thickness portion in a radial manner, and arranged to face the coils in the direction along the rotational axis of the hub, and
 a portion of the hub that faces the coils in the direction along the rotational axis of the hub is thicker than the coil-facing portion.   
     
     
         7 . The rotating device according to  claim 1 , wherein, when a coordinate is defined along the rotational axis of the hub, the coordinate range of the core at least partly overlaps the coordinate range of a portion where the bearing unit touches the surrounding portion. 
     
     
         8 . The rotating device according to  claim 1 , wherein the bearing unit is formed so that a diameter of a portion where the bearing unit touches the surrounding portion is greater than a diameter of another portion. 
     
     
         9 . The rotating device according to  claim 1 , wherein a space on the hub-side of the base is filled with a gas, which includes a predetermined ratio of Helium, and
 a through hole is provided on the base, and   a seal member is provided along an edge of the through-hole on a surface of the base opposite to the hub.   
     
     
         10 . The rotating device according to  claim 1 , further comprising a ring-shaped thrust ring, the center of which is along the rotational axis of the hub, the ring-shaped thrust ring being fixed to the hub, and
 the thrust ring has a substantially flat hub-facing surface that faces the hub in the direction along the rotational axis of the hub, and   a part of the hub-facing surface is in contact with the hub and the other part, when the hub rotates, suppresses the motion of the hub in the direction along the rotational axis of the hub in cooperation with the bearing unit.   
     
     
         11 . The rotating device according to  claim 10 , wherein the thrust ring is made of a material, the hardness of which substantially is equal to that of the hub.