The invention relates to a spindle motor having a fluid dynamic bearing system used particularly for driving the storage disks of hard disk drives, having a baseplate, a stationary bearing bush disposed in an opening in the baseplate, a shaft rotatably supported in an axial bore in the bearing bush by means of the fluid dynamic bearing system, a hub connected to the shaft, and an electromagnetic drive system. In order to increase the stiffness of the motor system, according to the invention the bearing bush is provided with a flange that is fixed in the opening in the baseplate and whose outside diameter is distinctly larger than the outside diameter of the bearing bush. Instead of a flange at the outer diameter of the bearing bush there can be provided a sleeve at the base plate which receives the bearing bush at least partly.
1. A spindle motor ( 10 ; 110 ) having a fluid dynamic bearing system, having a baseplate ( 12 ), a stationary bearing bush ( 14 ; 114 ) disposed in an opening in the baseplate, a shaft ( 18 ) rotatably supported in an axial bore in the bearing bush by means of the fluid dynamic bearing system, a hub ( 22 ) connected to the shaft, and an electromagnetic drive system ( 30 , 32 ), characterized in that the bearing bush ( 14 ; 114 ) has a flange ( 16 ; 116 ) that is fixed in the opening in the baseplate ( 12 ) and whose outside diameter is substantially larger than the outside diameter of the bearing bush, and that a damping element ( 34 ; 134 ) is disposed at a joint between the flange ( 16 ; 116 ) and the baseplate ( 12 ) and/or the flange ( 116 ) and the bearing bush ( 14 ; 114 ).
2. A spindle motor according to claim 1 , characterized in that the outside diameter of the flange ( 16 ; 116 ) is at least 1.5 times the outside diameter of the bearing bush.
3. A spindle motor according to claim 1 , characterized in that the outside diameter of the flange ( 16 ; 116 ) is substantially the same as the outside diameter of the hub ( 22 ).
4. A spindle motor according to claim 1 , characterized in that the flange ( 16 ) is integrally formed with the bearing bush ( 14 ).
5. A spindle motor according to claim 1 , characterized in that the flange 116 comprises a ring connected to the bearing bush ( 114 ).
6. A spindle motor according to claim 5 , characterized in that at least one interface between the flange ( 16 ; 116 ) and the baseplate ( 12 ) and/or between the flange ( 116 ) and the bearing bush ( 114 ) is conical in shape.
7. A spindle motor according to claim 5 , characterized in that the damping element ( 34 ) is disposed between the outside diameter of the flange ( 116 ) and the inside diameter of the opening in the baseplate ( 12 ).
8. A spindle motor according to claim 5 , characterized in that the damping element ( 134 ) is disposed between the inside diameter of the flange ( 116 ) and the outside diameter of the bearing bush ( 114 ).
9. A spindle motor according to claim 1 , characterized in that the flange ( 16 ; 116 ) is made of a material having an elasticity module E>=70 GPa.
10. A spindle motor according to claim 1 , characterized in that the flange ( 16 ; 116 ) is made either of metal, of a metal alloy, of a ceramic material or of a plastic.
11. A spindle motor according to claim 1 , characterized in that the damping element ( 34 ) is disposed between the outside diameter of the flange ( 16 ) and the inside diameter of the opening in the baseplate ( 12 ).
12. A spindle motor according to claim 1 , characterized in that the damping element ( 34 ; 134 ) has a thickness of between 10 and 100 μm.
13. A spindle motor according to claim 1 , characterized in that the damping element ( 34 ; 134 ) is made of a viscoelastic material.
14. A spindle motor according to claim 13 , characterized in that the damping element is made of a viscoelastic polymer foil.
15. A spindle motor according to claim 1 , characterized in that the damping element ( 34 ; 134 ) is connected to the flange and the baseplate or the bearing bush by means of bonding.
16. A spindle motor according to claim 1 , wherein the fluid dynamic bearing system is configured to drive a storage disk of a hard disk drive.