Fluid dynamic bearing system and a spindle motor having a fluid dynamic bearing system
View Patent ↗A fluid dynamic bearing including a bearing bush having a central bearing bore in which a shaft is rotatably supported. Surfaces of the shaft and of the bearing bore that face each other are separated from one another by a bearing gap filled with a bearing fluid. A first radial bearing section and a second radial bearing section are disposed along the bearing gap, between which a separator section is disposed. The width of the bearing gap varies with its axial length. The bearing gap has a first inner width ib 1 and a second inner width ib 2 in the region of the first and of the second radial bearing section on the sides facing the separator section, a first outer width ab 1 and a second outer width ab 2 on the sides remote from the separator section. According to the invention, the differences resulting from the inner widths and the outer widths, ib 1 −ab 1 and ib 2 −ab 2 , lie in an interval of a−t to a+t, where a is greater than zero and t is greater than a.
1. A fluid dynamic bearing comprising a bearing bush ( 10 , 210 ) having a central bearing bore ( 11 , 211 ) and a shaft ( 12 , 212 ) disposed in the bearing bore,
wherein the surfaces of the shaft ( 12 , 212 ) and of the bearing bore ( 11 , 211 ) that are facing each other are separated from one another by a bearing gap ( 14 , 214 ) filled with a bearing fluid, and wherein the shaft ( 12 , 212 ) and the bearing bush ( 10 , 210 ) are rotatable with respect to each other,
wherein a first radial bearing section ( 14 a , 214 a ) and a second radial bearing section ( 14 c , 214 c ) are disposed along the bearing gap ( 14 , 214 ), and a separator section ( 14 c , 214 c ) is disposed between the radial bearing sections, and
wherein the bearing gap ( 14 , 214 ) has
a first inner width ibl and a second inner width ib 2 in the region of the first and of the second radial bearing section ( 14 a , 14 c ; 214 a , 214 c ) on the sides facing the separator section ( 14 b , 214 b ) and
a first outer width ab 1 and a second outer width ab 2 on the sides remote from the separator section ( 14 b , 214 b ),
wherein spatial differences ib 1 −ab 1 and ib 2 −ab 2 lie within a tolerance range of a−t micrometers to a+t micrometers, where a>0 and t>a.
2. A fluid dynamic bearing according to claim 1 , wherein a=0.15 micrometers and t=0.5 micrometers.
3. A fluid dynamic bearing according to claim 1 , wherein the average gap width of the bearing gap ( 14 , 214 ) is between 2 and 5 micrometers.
4. A fluid dynamic bearing according to claim 1 , wherein the bearing bore ( 11 , 211 ) has a varying diameter along the radial bearing sections ( 14 a , 14 c ; 214 a , 214 c ).
5. A fluid dynamic bearing according to claim 1 , wherein the shaft ( 12 , 212 ) has a varying diameter along the radial bearing sections ( 14 a , 14 c ; 214 a , 214 c ).
6. A fluid dynamic bearing according to claim 1 , wherein, along the first bearing section ( 14 a , 214 a ), the bearing gap ( 14 ; 214 ) has a diameter D 1 at an outer end that is smaller than a diameter D 2 at an inner end, and wherein the diameter of the bearing gap ( 14 ; 214 ) increases continuously between D 1 and D 2 .
7. A fluid dynamic bearing according to claim 1 , wherein, along the second radial bearing section ( 14 c ; 214 c ), the bearing gap ( 14 ; 214 ) has a diameter D 3 at an outer end that is smaller than a diameter D 4 at an inner end, and wherein the diameter of the bearing gap ( 14 ; 214 ) increases continuously between D 3 and D 4 .
8. A spindle motor preferably for driving a hard disk drive comprising:
a stationary motor component,
a rotating motor component that is rotatably supported with respect to the stationary motor component about a central rotational axis ( 50 ; 250 ),
a fluid dynamic bearing comprising a bearing bush ( 10 , 210 ) having a central bearing bore ( 11 , 211 ) and a shaft ( 12 , 212 ) disposed in the bearing bore,
wherein the surfaces facing each other of the shaft ( 12 , 212 ) and of the bearing bore ( 11 , 211 ) are separated from one another by a bearing gap ( 14 , 214 ) filled with a bearing fluid, and wherein the shaft ( 12 , 212 ) and the bearing bush ( 10 , 210 ) are rotatable with respect to one another,
wherein a first radial bearing section ( 14 a , 214 a ) and a second radial bearing section ( 14 c , 214 c ) are disposed along the bearing gap ( 14 , 214 ), and a separator section ( 14 c , 214 c ) is disposed between the radial bearing sections, and
the bearing gap ( 14 , 214 ) has
a first inner width ibl and a second inner width ib 2 in the region of the first and of the second radial bearing section ( 14 a , 14 c ; 214 a , 214 c ) on the sides facing the separator section ( 14 b , 214 b ) and
a first outer width abl and a second outer width ab 2 on the sides remote from the separator section ( 14 b , 214 b ),
wherein the spatial differences ib 1 −ab 1 and ib 2 −ab 2 lie within a tolerance range of a−t micrometers to a+t micrometers, where a>0 and t>a, and
an electromagnetic drive unit having a stator ( 40 ; 240 ) that is disposed on the stationary motor component, and an annular rotor magnet ( 42 ; 242 ), that is disposed on the rotating motor component lying opposite the stator.
9. A spindle motor according to claim 8 , wherein the stationary motor component has a bearing bush ( 10 ) disposed in a baseplate ( 36 ).
10. A spindle motor according to claim 8 , wherein the stationary motor component comprises a first bearing component ( 226 ) disposed in a baseplate ( 236 ), a shaft ( 212 ) held in the first bearing component and a second bearing component ( 216 ) fixed to the shaft.
11. A spindle motor according to claim 8 , wherein the rotating motor component comprises a shaft ( 12 ) and a hub ( 38 ) connected to the shaft.
12. A spindle motor according to claim 8 , wherein the rotating motor component comprises a rotor component ( 238 ) having a bearing bush ( 210 ).