Spindle motor assembly with polymeric motor shaft and hub

Abstract

A spindle motor assembly ( 18 ) includes a polymeric motor shaft ( 20 ), a polymeric hub ( 22 ) to support a rotating disc ( 24 ), and a stator ( 40 ) disposed in an internal cavity defined by the hub. A resilient snap-in retainer ( 62 ) is molded to the motor shaft ( 20 ) to hold the hub ( 22 ) in place. A surface of the polymeric hub and an opposing surface of the polymeric motor shaft form a hydrodynamic bearing.

What is claimed is:  
     
         1 . A spindle motor assembly comprising a polymeric motor shaft, a polymeric hub to support a rotating disc, and a stator disposed in an internal cavity defined by the hub, wherein a surface of the polymeric hub and an opposing surface of the polymeric motor shaft form a hydrodynamic bearing.  
     
     
         2 . The spindle motor assembly of  claim 1  including a snap-in retainer molded to the hub to hold the disc in place.  
     
     
         3 . The spindle motor assembly of  claim 1  including a fastener molded to the hub to hold the disc in place.  
     
     
         4 . The spindle motor assembly of  claim 1  including a snap-in retainer molded to the motor shaft to hold the hub in place.  
     
     
         5 . The spindle motor assembly of  claim 4  wherein the snap-in retainer is resilient.  
     
     
         6 . The spindle motor assembly of  claim 1  wherein the stator includes coils and wherein a magnet is connected to the hub such that during operation of the disc drive, the magnet interacts with the coils to cause rotational movement of the hub about the motor shaft.  
     
     
         7 . The spindle motor assembly of  claim 6  wherein the magnet is attached to a back-iron connected to the hub.  
     
     
         8 . The spindle motor assembly of  claim 7  including a flux conducting ring disposed at an outer perimeter of a horizontal extension of the motor shaft.  
     
     
         9 . The spindle motor assembly of  claim 1  including pressure generating features formed in the polymeric motor shaft, wherein during operation of the spindle motor assembly, the journal bearing and pressure generating features create a pressure gradient in a gap between the surface of the motor shaft and the opposing surface of the hub.  
     
     
         10 . The spindle motor assembly of  claim 9  wherein the pattern of pressure generating features includes spiral grooves formed in the motor shaft.  
     
     
         11 . The spindle motor assembly of  claim 9  wherein the pattern of pressure generating features includes Rayleigh steps formed in the motor shaft.  
     
     
         12 . The spindle motor assembly of  claim 1  including a solid lubricant disposed on a surface of the hub that comes into contacts the motor shaft during operation during operation of the spindle motor assembly.  
     
     
         13 . The spindle motor assembly of  claim 1  including a solid lubricant disposed on a surface of the motor shaft that comes into contact with the hub during operation of the spindle motor assembly.  
     
     
         14 . A computer disc drive comprising: 
 a spindle motor assembly including a polymeric motor shaft having a pattern of pressure generating features, a polymeric hub to support a rotating disc, and a stator disposed in an internal cavity defined by the hub, wherein a surface of the polymeric hub and an opposing surface of the polymeric motor shaft form a hydrodynamic bearing, and wherein during operation of the disc drive, the journal bearing and pressure generating features create a pressure gradient in a gap between the surface of the motor shaft and the opposing surface of the hub.    
     
     
         15 . The disc drive of  claim 14  including a snap-in retainer molded to the motor shaft to hold the hub in place.  
     
     
         16 . The disc drive of  claim 14  wherein the stator includes coils and wherein a magnet is connected to a back-iron attached to the hub and a flux conducting ring is disposed at an outer perimeter of a horizontal extension of the motor shaft, wherein during operation of the disc drive, the magnet interacts with the coils to cause rotational movement of the hub about the motor shaft, and the flux conducting ring forms a thrust bearing.  
     
     
         17 . A method of assembling a spindle motor assembly for a computer disc drive, the method comprising: 
 positioning a hub over a motor shaft;    pressing the hub downward so that an extension on the hub contacts a snap-in retainer molded to the motor shaft; and    allowing the snap-in retainer to spring back to hold the hub in place.    
     
     
         18 . The method of  claim 17  further including: 
 holding a disc in place with a snap-in retainer molded to the hub.  
 
     
     
         19 . The method of  claim 17  wherein the hub defines an internal cavity for a stator when the hub is held in place by the snap-in retainer.  
     
     
         20 . A spindle motor assembly comprising a polymeric motor shaft, a polymeric hub to support a rotating disc, a stator disposed in an internal cavity defined by the hub, and means for holding the hub in place with respect to the motor shaft.  
     
     
         21 . A spindle motor assembly comprising a motor shaft, a hub to support a rotating disc, a stator disposed in an internal cavity defined by the hub, a hydrodynamic bearing between a surface of the motor shaft and an opposing surface of the hub and means for creating a pressure gradient in a gap between the surface of the motor shaft and the opposing surface of the hub.