Spindle motor assembly for disc drives

Abstract

A novel spindle motor assembly is disclosed that utilizes a fixed shaft and places the motor rotor components on the outside wall of the spindle hub directly below its disc stack supporting flange. The structure disclosed provides a compact yet powerful motor having a relatively low profile.

What is claimed is:  
     
         1 . A spindle motor assembly comprising: 
 a fixed shaft;    a spindle hub journaled coaxially about the fixed shaft, the spindle hub having inner and outer surfaces, an enlarged thickness flange portion having a support surface for supporting a disc stack and a second surface located opposite the first surface, and a reduced thickness rotor carrying portion located adjacent the second surface of the flange portion;    a pair of spaced apart bearings for rotatably coupling the spindle hub to the fixed shaft, each said bearing having an inner race secured to the fixed shaft and an outer race secured to the inner surface of the spindle hub;    magnet means carried by the outer surface of the rotor carrying portion of the spindle hub, the magnet means having a plurality of poles and forming the rotor portion of the spindle motor; and    stator means having a plurality of fixed windings for cooperating with the magnet means to rotate the spindle hub with respect to the shaft.    
     
     
         2 . A spindle motor assembly as recited in  claim 1  further comprising a Hall effect sensor fixedly positioned adjacent the magnet means to detect passage of the poles to control commutation.  
     
     
         3 . A spindle motor assembly as recited in  claim 2  wherein said magnet means includes an annular ring formed of a magnet material, the annular ring being magnetized to have a multiplicity of poles and each pole is magnetized to generate fields having two separate orientations.  
     
     
         4 . A spindle motor assembly as recited in  claim 2  further comprising a base plate for mounting the spindle motor assembly to a disc drive housing, and wherein the base plate carries the stator means and the Hall effect sensor.  
     
     
         5 . A spindle motor assembly as recited in  claim 1  wherein said magnet means includes: 
 an annual ring formed of a magnet material, the annular ring being magnetized to have a multiplicity of poles; and  
 a ferric ring secured to the outer surface of the rotor carrying portion of the spindle hub for carrying the magnetic ring.  
 
     
     
         6 . A spindle motor assembly for rotating a disc stack within a disc drive having a drive housing, the spindle motor assembly comprising: 
 a fixed shaft fixedly coupled to the drive housing;    a spindle hub journaled coaxially about the fixed shaft, the spindle hub having, 
 inner and outer surfaces,  
 an enlarged thickness flange portion having a first surface for supporting the disc stack and a second surface opposing the first surface, the first and second flange surfaces forming a portion of the outer surface of the spindle hub, and  
 a reduced thickness rotor carrying portion located adjacent the second surface of the flange portion;  
   a pair of spaced apart bearings for rotatably coupling the spindle hub to the fixed shaft, each said bearing having an inner race secured to the fixed shaft and an outer race secured to the inner surface of the spindle hub;    magnet means carried by the outer surface of the rotor carrying portion, the magnet means having a plurality of poles, the magnet means forming the rotor portion of the spindle motor; and    stator means having a plurality of fixed windings for cooperating with the magnet means to rotate the spindle hub with respect to the shaft.    
     
     
         7 . A spindle motor as recited in  claim 6  wherein the drive housing forms a well into which the magnet means and stator means may be recessed.  
     
     
         8 . A spindle motor assembly as recited in  claim 7  further comprising a base plate for mounting the assembly to the drive housing and wherein the shaft and the stator means are carried by the base plate.