Fluid dynamic pressure bearing for spindle motors and storage disk drive devices and having ridge portions between grooves in the fluid dynamic pressure bearing

1. A fluid dynamic bearing comprising:

a shaft component; and

a bearing sleeve component, said bearing sleeve component and said shaft component being rotatably supported with respect to each other;

wherein at least one of said components is made of steel comprising by weight C: 0.6-1.20%; Si: 1.0% or less; Mn: 1.0% or less; Cr: 10.5-18.0%; Mo: 1.0% or less; S: 0.03% or less; and Fe, and wherein said at least one of said components further comprises a fluid dynamic bearing surface having a plurality of electrochemically machined hydrodynamic pressure generating grooves with raised substantially straight top ridge portions remaining between said grooves,

wherein a profile view of said fluid dynamic bearing surface comprises substantially straight top ridge portions, a substantially straight sloped side portion, and a bottom portion.

2. A fluid dynamic bearing according to claim 1 , wherein said steel is stainless steel.

3. A fluid dynamic bearing according to claim 1 , wherein said steel is heat treated prior to the electrochemical machining of said hydrodynamic pressure generating grooves.

4. A fluid dynamic bearing according to claim 3 , wherein said steel is polished prior to the electrochemical machining of said hydrodynamic pressure generating grooves.

5. A fluid dynamic bearing according to claim 1 , wherein said fluid dynamic bearing surface viewed in a perpendicular cross-section further comprises a substantially straight top ridge portion, substantially straight sloped walls and a bottom portion.

6. A fluid dynamic bearing according to claim 5 , wherein said substantially straight top ridge portion is connected to said substantially straight sloped walls by substantially arcuate portions, and wherein a length of each of said substantially arcuate portions in a direction parallel to said substantially straight top ridge portion is 20 μm or less, and a length of each of said substantially arcuate portions in a direction parallel to said substantially straight sloped wall is 1.0 μm or less.

7. A fluid dynamic bearing according to claim 5 , wherein each of said substantially straight sloped walls has a length, said length being 75%-90% of a length of a line segment tangential to said substantially straight sloped wall and cut by a line tangential to said substantially straight top ridge portion and a line tangential to a deepest point of a corresponding groove.

8. A fluid dynamic bearing according to claim 1 , wherein surface roughness of said raised top ridge portions is Ra 0.11 μm or less.

9. A fluid dynamic bearing according to claim 1 , wherein a variation in depths of said pressure generating grooves is 0.4 μm or less.

10. A fluid dynamic bearing according to claim 1 , wherein said steel further comprises by weight Pb: 0.001% or less, as an unavoidable impurity.

11. A fluid dynamic bearing according to claim 1 further comprising an end plate enclosing said bearing sleeve component, said end plate having a fluid dynamic bearing surface having a plurality of electrochemically machined hydrodynamic pressure generating grooves with raised top ridge portions remaining between said grooves.

12. A fluid dynamic bearing according to claim 11 , wherein said end plate is made of steel comprising by weight C: 0.6-1.20%; Si: 1.0% or less; Mn: 1.0% or less; Cr: 10.5-18.0%; Mo: 1.0% or less; S: 0.03% or less; and Fe.

13. A fluid dynamic bearing according to claim 12 , wherein said steel further comprises by weight Pb: 0.001% or less, as an unavoidable impurity.

14. A spindle motor having a fluid dynamic bearing, said spindle motor comprising:

a motor base;

a bearing sleeve fixedly secured to said motor base;

a stator secured to said motor base;

a rotating shaft, said rotating shaft being rotatably supported with respect to said bearing sleeve;

a rotor hub mounted on said rotating shaft; and

a rotor magnet secured to said rotor hub, said rotor magnet working together with said stator to generate a rotating magnetic field,

wherein at least one of said rotating shaft and said bearing sleeve is made of steel comprising by weight C: 0.6-1.20%; Si: 1.0% or less; Mn: 1.0% or less; Cr: 10.5-18.0%; Mo: 1.0% or less; S: 0.03% or less; and Fe, and wherein said at least one of said rotating shaft and said bearing sleeve further comprises a fluid dynamic bearing surface having a plurality of electrochemically machined hydrodynamic pressure generating grooves with raised substantially straight top ridge portions remaining between said grooves,

wherein a profile view of said fluid dynamic bearing surface comprises substantially straight top ridge portions, a substantially straight sloped side portion, and a bottom portion.

15. A spindle motor according to claim 14 , wherein said steel is stainless steel.

16. A spindle motor according to claim 14 , wherein said steel is heat treated prior to the electrochemical machining of said hydrodynamic pressure generating grooves.

17. A Spindle motor according to claim 16 , wherein said steel is polished prior to the electrochemical machining of said hydrodynamic pressure generating grooves.

18. A spindle motor according to claim 14 , wherein said fluid dynamic bearing surface viewed in a perpendicular cross-section further comprises a substantially straight top ridge portion, substantially straight sloped walls and a bottom portion.

19. A spindle motor according to claim 18 , wherein said substantially straight top ridge portion is connected to said substantially straight sloped walls by substantially arcuate portions, and wherein a length of a line segment tangential to said substantially straight sloped wall and cut by a line tangential to said substantially straight top ridge portion and a line tangential to a deepest point of a corresponding groove.

20. A spindle motor according to claim 18 , wherein each of said substantially straight sloped walls has a length, said length being 75%-90% of a length of a line segment tangential to said substantially straight sloped wall and cut by a line tangential to said substantially straight top ridge portion and a line tangential to a deepest point of a corresponding groove.

21. A spindle motor according to claim 14 , wherein surface roughness of said raised top ridge portions is Ra 1.0 μm or less.

22. A spindle motor according to claim 14 , wherein a variation in depths of said pressure generating grooves is 0.4 μm or less.

23. A spindle motor, according to claim 14 , wherein said steel further comprises by weight Pb: 0.001% or less, as an unavoidable impurity.

24. A spindle motor according to claim 14 , further comprising an end plate enclosing said bearing sleeve component, said end plate having a fluid dynamic bearing surface having a plurality of electrochemically machined hydrodynamic pressure generating grooves with raised top ridge portions remaining between said grooves.

25. A spindle motor according to claim 24 , wherein said end plate is made of steel comprising by weight C: 0.6-1.20%; Si: 1.0% or less; Mn: 1.0% or less; Cr: 10.5-18.0%; Mo: 1.0% or less; S: 0.03% or less; and Fe.

26. A spindle motor according to claim 25 , wherein said steel further comprises by weight Pb: 0.001% or less, as an unavoidable impurity.

27. A spindle motor having a fluid dynamic bearing, said spindle motor comprising: a motor base;

a fixed shaft mounted on said motor base;

a stator secured to said motor base;

a rotating bearing sleeve, said rotating bearing sleeve being rotatably supported with respect to said fixed shaft;

a rotor hub mounted on said rotating bearing sleeve; and

a rotor magnet secured to said rotor hub, said rotor magnet working together with said stator to generate a rotating magnetic field,

wherein at least one of said fixed shaft and said rotating bearing sleeve is made of steel comprising by weight C: 0.6-1.20%; Si: 1.0% or less; Mn: 1.0% or less; Cr: 10.5-18.0%; Mo: 1.0% or less; S: 0.03% or less; and Fe, and wherein said at least one of said fixed shaft and said rotating bearing sleeve further comprises a fluid dynamic bearing surface having a plurality of electrochemically machined hydrodynamic pressure generating grooves with raised substantially straight top ridge portions remaining between said grooves,

wherein a profile view of said fluid dynamic bearing surface comprises substantially straight top ridge portions, a substantially straight sloped side portion, and a bottom portion.

28. A spindle motor according to claim 27 , wherein said steel is stainless steel.

29. A spindle motor according to claim 27 , wherein said steel is heat treated prior to the electrochemical machining of said hydrodynamic pressure generating grooves.

30. A spindle motor according to claim 29 , wherein said steel is polished prior to the electrochemical machining of said hydrodynamic pressure generating grooves.

31. A spindle motor according to claim 27 , wherein said fluid dynamic bearing surface viewed in a perpendicular cross-section further comprises a substantially straight top ridge portion, substantially straight sloped walls and a bottom portion.

32. A spindle motor according to claim 31 , wherein said substantially straight top ridge portion is connected to said substantially straight sloped walls by substantially arcuate portions, and wherein a length of a line segment tangential to said substantially straight sloped wall and cut by a line tangential to said substantially straight top ridge portion and a line tangential to a deepest point of a corresponding groove.

33. A spindle motor according to claim 31 , wherein each of said substantially straight sloped walls has a length, said length being 75%-90% of a length of a line segment tangential to said substantially straight sloped wall and cut by a line tangential to said substantially straight top ridge portion and a line tangential to a deepest point of a corresponding groove.

34. A spindle motor according to claim 27 , wherein surface roughness of said raised top ridge portions is Ra 1.0 μm or less.

35. A spindle motor according to claim 27 , wherein a variation in depths of said pressure generating grooves is 0.4 μm or less.

36. A spindle motor according to claim 27 , wherein said steel further comprises by weight Pb: 0.001% or less, as an unavoidable impurity.

37. A spindle motor according to claim 27 , further comprising an end plate enclosing said bearing sleeve component, said end plate having a fluid dynamic bearing surface having a plurality of electrochemically machined hydrodynamic pressure generating grooves with raised top ridge portions remaining between said grooves.

38. A spindle motor according to claim 37 , wherein said end plate is made of steel comprising by weight C: 0.6-1.20%; Si: 1.0% or less; Mn: 1.0% or less; Cr: 10.5-18.0%; Mo: 1.0% or less; S: 0.03% or less; and Fe.

39. A spindle motor according to claim 38 , wherein said steel further comprises by weight Pb: 0.001% or less, as an unavoidable impurity.

40. A disk drive storage device comprising:

a spindle motor having a fluid dynamic bearing, said spindle motor including

a motor base;

a fixed shaft mounted on said motor base;

a stator secured to said motor base;

a rotating bearing sleeve, said rotating bearing sleeve being rotatably supported with respect to said fixed shaft;

a rotor hub mounted on said rotating bearing sleeve; and

a rotor magnet secured to said rotor hub, said rotor magnet working together with said stator to generate a rotating magnetic field;

a storage disk mounted for rotation on said rotor hub of said spindle motor; and a data head executing read/write operations on said storage disk,

wherein at least one of said fixed shaft and said rotating bearing sleeve is made of steel comprising by weight C: 0.6-1.20%; Si: 1.0% or less; Mn: 1.0% or less; Cr: 10.5-18.0%; Mo: 1.0% or less; S: 0.03% or less; and Fe, and wherein said at least one of said fixed shaft and said rotating bearing sleeve further comprises a fluid dynamic bearing surface having a plurality of electrochemically machined hydrodynamic pressure generating grooves with raised substantially straight top ridge portions remaining between said grooves,

wherein a profile view of said fluid dynamic bearing surface comprises substantially straight top ridge portions, a substantially straight sloped side portion, and a bottom portion.

41. A disk drive storage device according to claim 40 , wherein said steel is stainless steel.

42. A disk drive storage device according to claim 40 , wherein said steel is heat treated prior to the electrochemical machining of said hydrodynamic pressure generating grooves.

43. A disk drive storage device according to claim 42 , wherein said steel is polished prior to the electrochemical machining of said hydrodynamic pressure generating grooves.

44. A disk drive storage device according to claim 40 , wherein said fluid dynamic bearing surface viewed in a perpendicular cross-section further comprises a substantially straight top ridge portion, substantially straight sloped walls and a bottom portion.

45. A disk drive storage device according to claim 44 , wherein said substantially straight top ridge portion is connected to said substantially straight sloped walls by substantially arcuate portions, and wherein a length of a line segment tangential to said substantially straight sloped wall and cut by a line tangential to said substantially straight top ridge portion and a line tangential to a deepest point of a corresponding groove.

46. A disk drive storage device according to claim 44 , wherein each of said substantially straight sloped walls has a length, said length being 75%-90% of a length of a line segment tangential to said substantially straight sloped wall and cut by a line tangential to said substantially straight top ridge portion and a line tangential to a deepest point of a corresponding groove.

47. A disk drive storage device according to claim 40 , wherein surface roughness of said raised top ridge portions is Ra 1.0 μm or less.

48. A disk drive storage device according to claim 40 , wherein a variation in depths of said pressure generating grooves is 0.4 μm or less.

49. A disk drive storage device according to claim 40 , wherein said steel further comprises by weight Pb: 0.001% or less, as an unavoidable impurity.

50. A disk drive storage device according to claim 40 , wherein said spindle motor further comprises an end plate enclosing said bearing sleeve component, said end plate having a fluid dynamic bearing surface having a plurality of electrochemically machined hydrodynamic pressure generating grooves with raised top ridge portions remaining between said grooves.

51. A disk drive storage device according to claim 50 , wherein said end plate is made of steel comprising by weight C: 0.6-1.20%; Si: 1.0% or less; Mn: 1.0% or less; Cr: 10.5-18.0%; Mo: 1.0% or less; S: 0.03% or less; and Fe.

52. A disk drive storage device according to claim 51 , wherein said steel further comprises by weight Pb: 0.001% or less, as an unavoidable impurity.

53. A disk drive storage device comprising:

a spindle motor having a fluid dynamic bearing, said spindle motor including

a motor base;

a bearing sleeve fixedly secured to said motor base;

a stator secured to said motor base;

a rotating shaft, said rotating shaft being rotatably supported with respect to said bearing sleeve;

a rotor hub mounted on said rotating shaft; and

a rotor magnet secured to said rotor hub, said rotor magnet working together with said stator to generate a rotating magnetic field,

a storage disk mounted for rotation on said rotor hub of said spindle motor; and a data head executing read/write operations on said storage disk,

wherein at least one of said rotating shaft and said bearing sleeve is made of a steel comprising by weight C: 0.6-1.20%; Si: 1.0% or less; Mn: 1.0% or less; Cr: 10.5-18.0%; Mo: 1.0% or less; S: 0.03% or less; and Fe, and wherein said at least one of said rotating shaft and said bearing sleeve further comprises a fluid dynamic bearing surface having a plurality of electrochemically machined hydrodynamic pressure generating grooves with raised substantially straight top ridge portions remaining between said grooves,

wherein a profile view of said fluid dynamic bearing surface comprises substantially straight top ridge portions, a substantially straight sloped side portion, and a bottom portion.

54. A disk drive storage device according to claim 53 , wherein said steel is stainless steel.

55. A disk drive storage device according to claim 53 , wherein said steel is heat treated prior to the electrochemical machining of said hydrodynamic pressure generating grooves.

56. A disk drive storage device according to claim 55 , wherein said steel is polished prior to the electrochemical machining of said hydrodynamic pressure generating grooves.

57. A disk drive storage device according to claim 53 , wherein said fluid dynamic bearing surface viewed in a perpendicular cross-section further comprises a substantially straight top ridge portion, substantially straight sloped walls and a bottom portion.

58. A disk drive storage device according to claim 57 , wherein said substantially straight top ridge portion is, connected to said substantially straight sloped walls by substantially arcuate portions, and wherein a length of a line segment tangential to said substantially straight sloped wall and cut by a line tangential to said substantially straight top ridge portion and a line tangential to a deepest point of a corresponding groove.

59. A disk drive storage device according to claim 57 , wherein each of said substantially straight sloped walls has a length, said length being 75%-90% of a length of a line segment tangential to said substantially straight sloped wall and cut by a line tangential to said substantially straight top ridge portion and a line tangential to a deepest point of a corresponding groove.

60. A disk drive storage device according to claim 53 , wherein surface roughness of said raised top ridge portions is Ra 1.0 μm or less.

61. A disk drive storage device according to claim 53 , wherein a variation in depths of said pressure generating grooves is 0.4 μm or less.

62. A disk drive storage device according to claim 53 , wherein said steel further comprises by weight Pb: 0.001% or less, as an unavoidable impurity.

63. A disk drive storage device according to claim 53 , wherein said spindle motor further comprises an end plate enclosing said bearing sleeve component, said end plate having a fluid dynamic bearing surface having a plurality of electrochemically machined hydrodynamic pressure generating grooves with raised top ridge portions remaining between said grooves.

64. A disk drive storage device according to claim 63 , wherein said end plate is made of steel comprising by weight C: 0.6-1.20%; Si: 1.0% or less; Mn: 1.0% or less; Cr: 10.5-18.0%; Mo: 1.0% or less; S: 0.03% or less; and Fe.

65. A disk drive storage device according to claim 64 , wherein said steel further comprises by weight Pb: 0.001% or less, as an unavoidable impurity.

66. A method for manufacturing of a fluid dynamic bearing having a shaft component and a bearing sleeve component, said method comprising the steps of:

forming at least one component of said fluid dynamic bearing of a steel comprising by weight C: 0.6-1.20%; Si: 1.0% or less; Mn: 1.0% or less; Cr: 10.5-18.0%; Mo: 1.0% or less; S: 0.03% or less; and Fe, said steel further having eutectic carbon particles of 10 μm or less in diameter;

heat treating said at least one component by tempering and annealing;

polishing said heat treated component; and

electrochemically machining said heat treated and polished component to form a plurality of hydrodynamic pressure generating grooves with raised substantially straight top ridge portions remaining between said grooves,

wherein a profile view of said fluid dynamic bearing surface comprises substantially straight top ridge portions, a substantially straight sloped side portion, and a bottom portion.

67. A method for manufacturing of a fluid dynamic bearing according to claim 66 , wherein said steel further comprises by weight Pb: 0.001% or less, as an unavoidable impurity.