Lubricated limiter for fluid dynamic bearing motor
View Patent ↗In one example, a FDB motor having a top-cover attached, EM biased bearing system is provided. The motor includes a shaft and rotor disposed for relative rotation, and an axial limiter for restricting axial movement of the rotor with respect to the shaft, wherein the axial limiter is wet or lubricated during contact. The limiter is spatially fixed with respect to one of the shaft or the rotor and disposed with an axial end surface opposing a surface portion spatially fixed with respect to the other of the shaft or the rotor to form a gap therebetween. The gap may be filled with a fluid such as bearing lubricant, thereby providing a lubricated or wet contact surface to restrict axial movement of the shaft and rotor. Additionally, one or both surfaces may include a groove or slot to provide circulation of fluid through the gap.
1. A fixed shaft, fluid dynamic bearing motor system, comprising:
a shaft and rotor disposed for relative rotation about an axis of rotation; and
a limiter for restricting axial movement of the rotor with respect to the shaft, the limiter having an axial end surface opposing a surface portion of one of the shaft and the rotor, wherein a gap is formed between the axial end surface and the opposing surface portion, the gap being filled with a fluid during relative rotation of the shaft and rotor.
2. The system of claim 1 , further including an electromagnetic assembly for providing a magnetic bias along an axial direction.
3. The system of claim 1 , wherein the rotor includes a sleeve and a hub, the sleeve forming a bearing surface with the shaft.
4. The system of claim 1 , wherein the shaft is supported at both ends.
5. The system of claim 1 , wherein the shaft is spatially fixed with respect to a thrust cup and the thrust cup includes the limiter.
6. The system of claim 1 , wherein the axial end surface includes at least one groove formed therein.
7. The system of claim 1 , wherein at least one of the axial end surface and the opposing surface portion includes at least one groove formed therein.
8. The system of claim 7 , liquid is circulated through the gap during relative rotation of the axial end surface and opposing surface due to the at least one groove.
9. The system of claim 8 , wherein the fluid in the gap is further circulated through a fluid dynamic bearing between the shaft and rotor.
10. The system of claim 1 , wherein the limiter further forms part of a capillary seal within the fluid dynamic bearings system.
11. The system of claim 1 , further including a top-cover attached to the shaft.
12. The system of claim 1 , wherein the limiter is integral with a portion of the shaft or the rotor.
13. The system of claim 1 , wherein the limiter is spatially fixed with respect to one of the shaft and the rotor.
14. The system of claim 13 , wherein the opposing surface portion is spatially fixed to the other of the shaft and the rotor.
15. The system of claim 2 , wherein the cross-sectional shape of the limiter is chosen from the group including a square and a flat rectangle.
16. A fixed shaft, fluid dynamic bearing motor system, comprising:
a shaft and rotor disposed for relative rotation about an axis of rotation; and
a limiter for restricting axial movement of the rotor with respect to the shaft, the limiter spatially fixed with respect to one of the shaft or the rotor and having an axial end surface opposing a surface portion spatially fixed with respect to the other of the shaft and the rotor, wherein a gap is formed between the axial end surface and the opposing surface portion, the gap being filled with a fluid during relative rotation of the shaft and rotor;
wherein the cross-sectional shape of the limiter has a reduced axial length.
17. A method of manufacturing a fixed shaft, fluid dynamic bearing motor system, comprising the steps of:
disposing a shaft and rotor for relative rotation about an axis of rotation;
spatially fixing a limiter with respect to one of the shaft and the rotor;
spatially fixing an axial end surface of the limiter opposing a surface portion with respect to the other of the shaft or the rotor;
forming a gap between the axial end surface and the opposing surface portion; and
filling the gap with a fluid during relative rotation of the shaft and rotor.
18. The method of claim 17 , further comprising magnetically basing the system along an axial direction with an electromagnetic assembly.
19. The method of claim 17 , further comprising forming a bearing surface with the shaft via a sleeve and a hub.
20. The method of claim 17 , further comprising supporting the shaft at both ends.
21. The method of claim 17 , further comprising spatially fixing the shaft with respect to a thrust cup and a thrust cup that includes the limiter.
22. The method of claim 17 , further comprising forming a groove on the axial end surface.
23. The method of claim 17 , further comprising forming a groove on at least one of the axial end surface and the opposing surface portion.
24. The method of claim 23 , further comprising creating a circulation of liquid through the gap during relative rotation of the axial end surface and opposing surface.
25. The method of claim 24 , further comprising circulating the fluid through a fluid dynamic bearing between the shaft and rotor.
26. The method of claim 17 , further comprising optimizing the ratio of grooved surfaces to non-grooved surfaces on at least one of the axial end of the limiter and the surface portion of the limiter for power loss.
27. The method of claim 17 , further comprising creating a pressure in the fluid that is greater than ambient pressure during relative rotation.