Spindle motor having a fluid dynamic bearing system and a stationary shaft

Abstract

The invention relates to a spindle motor having a fluid dynamic bearing system comprising axial and radial bearings that contains a rotor component ( 14 ) which encloses a stationary shaft ( 12 ), which in turn is connected at both its ends to axially aligned bearing parts ( 16; 18 ) that are fashioned such that they form capillary sealing gaps ( 32; 34 ), a recirculation channel ( 28 ) filled with bearing fluid that connects the remote regions of the bearing to each other, and an electromagnetic drive system ( 42, 44 ) for driving the rotor component.

The invention claimed is: 
     
       1. A spindle motor having a fluid dynamic bearing system comprising:
 a stationary shaft ( 12 ;  212 ;  312 ) that is held directly or indirectly in a baseplate ( 10 ,  210 ;  310 ), 
 a rotor component ( 14 ,  114 a;  214 ;  314 a-c) rotatably supported with respect to the shaft about a rotational axis ( 46 ;  246 ;  346 ), 
 a bearing gap ( 20 ,  220 ;  320 ) open at both ends filled with a bearing fluid that separates the adjoining surfaces of the shaft ( 12 ;  212 ;  312 ), the rotor component ( 14 ,  114 a;  214 ;  214 a-c) and at least one first bearing part ( 16 ,  216 ;  316 ) from one another, a first radial bearing ( 22 a,  222 a;  322 a) and a second radial bearing ( 22 b,  222 b;  322 b) formed between the opposing axially extending bearing surfaces of the shaft ( 12 ;  212 ;  312 ) and the rotor component ( 14 ,  114 a;  214 ;  314 a-c), 
 an axial bearing ( 26 ,  226 ;  326 ) formed between the opposing radially extending bearing surfaces of the rotor component ( 14 ,  114 a;  214 ;  314 a-c) and the first bearing part ( 16 ,  216 ;  316 ) connected to the baseplate, 
 a recirculation channel ( 28 ;  128 ;  228 ;  328 ) filled with bearing fluid that connects the remote regions of the bearing to each other, and 
 an electromagnetic drive system ( 42 ,  44 ;  342 ,  244 ) for driving the rotor component, and 
 characterized in that the recirculation channel ( 28 ,  128 ;  228 ) ends in a gap ( 21 ) radially outside of the bearing gap ( 20 ) of the axial bearing ( 26 ), the width of the gap ( 21 ) being greater than the width of the bearing gap ( 20 ). 
 
     
     
       2. A spindle motor according to  claim 1 , characterized in that the rotor component consists of an inner, sleeve-shaped rotor component ( 114 a;  314 a) and an outer cup-shaped rotor component ( 144 b;  314 b). 
     
     
       3. A spindle motor according to  claim 2 , characterized in that the inner, sleeve-shaped rotor component ( 314 a) is enclosed by a further, sleeve-shaped rotor component ( 314 c) on which the outer cup-shaped rotor component ( 314 b) is disposed. 
     
     
       4. A spindle motor according to  claim 1 , characterized in that it only contains one rotating, mechanical rotor component ( 14 ;  214 ) taking the form of a hub/bearing bush arrangement. 
     
     
       5. A spindle motor according to  claim 1 , characterized in that the first bearing part ( 216 ) is integrally formed with the shaft ( 212 ) as one piece. 
     
     
       6. A spindle motor according to  claim 1 , characterized in that a second bearing part ( 18 ;  318 ) is integrally formed with the shaft ( 12 ) as one piece. 
     
     
       7. A spindle motor according to  claim 1 , characterized in that the rotor component ( 14 ,  114 a;  214 ;  314 a-c) has surfaces that are fashioned such that, together with surfaces of the second bearing part ( 18 ;  218 ;  318 ), they form a sealing gap ( 32 ;  232 ;  332 ) of a capillary gap seal. 
     
     
       8. A spindle motor according to  claim 1 , characterized in that the rotor component ( 14 ,  114 a;  214 ;  314 a-c) has surfaces that are fashioned such that, together with surfaces of a first bearing part ( 16 ;  216 ;  316 ), they form a sealing gap ( 34 ;  234 ;  334 ) of a capillary gap seal. 
     
     
       9. A spindle motor according to  claim 1 , characterized in that the recirculation channel ( 328 ) is disposed in the rotor component ( 314 a) or between the rotor components ( 314 a,  314 c) and connects the sealing gap ( 334 ) radially outside the axial bearing ( 226 ) to a section of the bearing gap ( 320 ) located radially outside a dynamic pumping seal. 
     
     
       10. A spindle motor according to  claim 1 , characterized in that the recirculation channel ( 28 ,  128 ;  228 ) is disposed at an incline to the rotational axis ( 46 ), which, on rotation of the rotor component, causes a centrifugal force to be exerted on the bearing fluid held in the recirculation channel, the centrifugal force transporting the bearing fluid through the recirculation channel ( 28 ,  128 ;  228 ) in the direction of arrow ( 29 ). 
     
     
       11. A spindle motor according to  claim 10 , characterized in that the recirculation channel ( 28 ,  128 ;  228 ) is inclined at an angle of 5 to 15 degrees with respect to the rotational axis ( 46 ). 
     
     
       12. A spindle motor according to  claim 10 , characterized in that the centrifugal force exerted on the bearing fluid due to the inclined recirculation channel ( 28 ,  128 ;  228 ) acts in the same direction as a pumping force exerted on the bearing fluid due to an overall pumping effect of the axial bearing ( 26 ;  126 ;  226 ;  326 ) and the radial bearings ( 22 a,  22 b;  122 a,  122 b;  222 a,  222 b;  322 a,  322 b). 
     
     
       13. A spindle motor according to  claim 12 , characterized in that the pumping force generated by the centrifugal force is directed to the axial bearing ( 26 ). 
     
     
       14. A spindle motor according to  claim 12 , characterized in that the centrifugal force is at least twice as big as the force exerted on the bearing fluid due to the overall pumping effect of the axial bearing ( 26 ) and the radial bearings ( 22 a,  22 b). 
     
     
       15. A spindle motor according to  claim 1 , characterized in that a dynamic pumping seal ( 36 ;  236 ;  336 ) is formed between opposing radially extending surfaces of the rotor component ( 14 ,  114 ;  214 ;  314 ) and a second bearing part ( 18 ;  218 ;  318 ) connected to the shaft. 
     
     
       16. A spindle motor according to  claim 15 , characterized in that the dynamic pumping seal ( 36 ;  236 ;  336 ) is formed between a radially extending end face of the rotor component ( 14 ,  114 a;  214 ;  314 a) and an adjoining radially extending end face of the second bearing part ( 18 ;  218 ;  318 ). 
     
     
       17. A spindle motor according to  claim 15 , characterized in that the dynamic pumping seal ( 36 ;  236 ;  336 ) is disposed substantially perpendicular and the sealing gap ( 32 ;  232 ;  332 ) of the gap seal is substantially parallel to the rotational axis ( 46 ;  246 ;  346 ). 
     
     
       18. A spindle motor according to  claim 1 , characterized in that the baseplate ( 10 ;  310 ) has a ferromagnetic ring ( 40 ;  340 ) that lies axially opposite a rotor magnet ( 44 ;  344 ) of the electromagnetic drive system and is magnetically attracted by this magnet and that they generate a magnetic force that is directed in the opposite direction to a bearing force generated by the axial bearing ( 26 ;  326 ). 
     
     
       19. A spindle motor according to claim  18  1, characterized in that the electromagnetic drive system comprises a stator arrangement ( 42 ;  342 ) which is disposed at an axial offset with respect to the a rotor magnet ( 44 ;  344 ) and generate a magnetic force that is directed in the opposite direction to a bearing force generated by the axial bearing ( 26 ;  326 ). 
     
     
       20. A spindle motor according to  claim 1 , characterized in that adjacent surfaces of the second bearing part ( 18 ) and the rotor component  14  form a further axial bearing ( 25 ). 
     
     
       21. A spindle motor according to  claim 1 , characterized in that a further bearing part ( 19 ) connected to the rotor component adjoins the second bearing part ( 18 ), a pumping seal ( 36 ) being disposed between the two bearing parts ( 18 ,  19 ) and a sealing gap being disposed between the bearing part ( 19 ) and the shaft ( 12 ). 
     
     
       22. A spindle motor having a fluid dynamic bearing system comprising:
 a stationary shaft ( 12 ;  212 ;  312 ) that is held directly or indirectly in a baseplate ( 10 ,  210 ;  310 ), 
 a rotor component ( 14 ,  114 a;  214 ;  314 a-c) rotatably supported with respect to the shaft about a rotational axis ( 46 ;  246 ;  346 ), 
 a bearing gap ( 20 ,  220 ;  320 ) open at both ends filled with a bearing fluid that separates the adjoining surfaces of the shaft ( 12 ;  212 ;  312 ), the rotor component ( 14 ,  114 a;  214 ;  214 a-c) and at least one first bearing part ( 16 ,  216 ;  316 ) from one another, a first radial bearing ( 22 a,  222 a;  322 a) and a second radial bearing ( 22 b,  222 b;  322 b) formed between the opposing axially extending bearing surfaces of the shaft ( 12 ;  212 ;  312 ) and the rotor component ( 14 ,  114 a;  214 ;  314 a-c), 
 an axial bearing ( 26 ,  226 ;  326 ) formed between the opposing radially extending bearing surfaces of the rotor component ( 14 ,  114 a;  214 ;  314 a-c) and the first bearing part ( 16 ,  216 ;  316 ) connected to the baseplate, 
 a recirculation channel ( 28 ;  128 ;  228 ;  328 ) filled with bearing fluid that connects the remote regions of the bearing to each other, and 
 an electromagnetic drive system ( 42 ,  44 ;  342 ,  244 ) for driving the rotor component, 
 characterized in that the recirculation channel ( 28 ,  128 ;  228 ) ends in a gap ( 21 ) radially outside of the bearing gap ( 20 ) of the axial bearing ( 26 ), and 
 further characterized in that the width of the gap ( 21 ) is greater than or equal to the width of the bearing gap ( 20 ) of the axial bearing ( 26 ) plus the depth of the bearing patterns of the axial bearing ( 26 ). 
 
     
     
       23. A spindle motor having a fluid dynamic bearing system comprising:
 a stationary shaft ( 12 ;  212 ;  312 ) that is held directly or indirectly in a baseplate ( 10 ,  210 ;  310 ), 
 a rotor component ( 14 ,  114 a;  214 ;  314 a-c) rotatably supported with respect to the shaft about a rotational axis ( 46 ;  246 ;  346 ), 
 a bearing gap ( 20 ,  220 ;  320 ) open at both ends filled with a bearing fluid that separates the adjoining surfaces of the shaft ( 12 ;  212 ;  312 ), the rotor component ( 14 ,  114 a;  214 ;  214 a-c) and at least one first bearing part ( 16 ,  216 ;  316 ) from one another, a first radial bearing ( 22 a,  222 a;  322 a) and a second radial bearing ( 22 b,  222 b;  322 b) formed between the opposing axially extending bearing surfaces of the shaft ( 12 ;  212 ;  312 ) and the rotor component ( 14 ,  114 a;  214 ;  314 a-c), 
 an axial bearing ( 26 ,  226 ;  326 ) formed between the opposing radially extending bearing surfaces of the rotor component ( 14 ,  114 a;  214 ;  314 a-c) and the first bearing part ( 16 ,  216 ;  316 ) connected to the baseplate, 
 a recirculation channel ( 28 ;  128 ;  228 ;  328 ) filled with bearing fluid that connects the remote regions of the bearing to each other, and 
 an electromagnetic drive system ( 42 ,  44 ;  342 ,  244 ) for driving the rotor component, and 
 a sealing gap ( 32 ;  332 ) for sealing the bearing gap ( 20 ,  220 ;  320 ) which is covered by an annular cover ( 30 ,  130 ;  330 ) connected to the rotor component ( 14 ;  114 a;  314 c) that, together with the second bearing part ( 18 ;  318 ), forms a labyrinth seal ( 48 ;  348 ). 
 
     
     
       24. A spindle motor according to  claim 23 , characterized in that the annular cover ( 330 ) is formed by the rotor component. 
     
     
       25. A spindle motor according to  claim 23 , characterized in that the sealing gap ( 32 ) is formed between an inner circumferential surface of the cover ( 130 ) and an outer circumferential surface of the second bearing part ( 18 ). 
     
     
       26. A spindle motor according to  claim 23 , characterized in that the sealing gap ( 32 ;  332 ) is formed between an inner circumferential surface/end face of the rotor component ( 14 ,  114 a;  214 ;  314 a;  314 c) and an outer circumferential surface/end face of the second bearing part ( 18 ;  218 ;  318 ). 
     
     
       27. A spindle motor according to  claim 23 , characterized in that the sealing gap ( 34 ;  234 ;  334 ) is formed between an outer circumferential surface of the rotor component ( 14 ,  114 a;  214 ;  314 a;  314 c) and an inner circumferential surface of the first bearing part ( 16 ;  216 ;  316 ). 
     
     
       28. A spindle motor according to  claim 23 , characterized in that surfaces of the rotor component ( 14 ,  144 a;  214 ) or the cover ( 130 ) and the second bearing part ( 18 ;  218 ) forming the sealing gap ( 32 ;  232 ) extend substantially parallel to the rotational axis ( 46 ;  246 ) or are inclined at an acute angle to the rotational axis. 
     
     
       29. A spindle motor according to  claim 23 , characterized in that surfaces of the rotor component ( 14 ,  114 a;  214 ;  314 a;  314 c) and the first bearing part ( 16 ;  216 ;  316 ) forming the sealing gap ( 34 ;  234 ;  334 ) extend substantially parallel to the rotational axis ( 46 ;  246 ;  346 ) or are inclined at an acute angle to the rotational axis. 
     
     
       30. A hard disk drive comprising a spindle motor for rotatably driving at least a storage disk, and means for writing on and reading data from the storage disk, the spindle motor having a fluid dynamic bearing system and comprising:
 a stationary shaft ( 12 ;  212 ;  312 ) that is held directly or indirectly in a baseplate ( 10 ,  210 ;  310 ), 
 a rotor component ( 14 ,  114 a;  214 ;  314 a-c) rotatably supported with respect to the shaft about a rotational axis ( 46 ;  246 ;  346 ), 
 a bearing gap ( 20 ,  220 ;  320 ) open at both ends filled with a bearing fluid that separates the adjoining surfaces of the shaft ( 12 ;  212 ;  312 ), the rotor component ( 14 ,  114 a;  214 ;  214 a-c) and at least one first bearing part ( 16 ,  216 ;  316 ) from one another, a first radial bearing ( 22 a,  222 a;  322 a) and a second radial bearing ( 22 b,  222 b;  322 b) formed between the opposing axially extending bearing surfaces of the shaft ( 12 ;  212 ;  312 ) and the rotor component ( 14 ,  114 a;  214 ;  314 a-c), 
 an axial bearing ( 26 ,  226 ;  326 ) formed between the opposing radially extending bearing surfaces of the rotor component ( 14 ,  114 a;  214 ;  314 a-c) and the first bearing part ( 16 ,  216 ;  316 ) connected to the baseplate, 
 a recirculation channel ( 28 ;  128 ;  228 ;  328 ) filled with bearing fluid that connects the remote regions of the bearing to each other, and 
 an electromagnetic drive system ( 42 ,  44 ;  342 ,  244 ) for driving the rotor component, 
 characterized in that the recirculation channel ( 28 ,  128 ;  228 ) ends in a gap ( 21 ) radially outside of the bearing gap ( 20 ) of the axial bearing ( 26 ), and 
 further characterized in that the width of the gap ( 21 ) is greater than or equal to the width of the bearing gap ( 20 ) of the axial bearing ( 26 ) plus the depth of the bearing patterns of the axial bearing ( 26 ). 
 
     
     
       31. A spindle motor having a fluid dynamic bearing system comprising:
 a stationary shaft ( 12 ;  212 ;  312 ) that is held directly or indirectly in a baseplate ( 10 ,  210 ;  310 ), 
 a rotor component ( 14 ,  114 a;  214 ;  314 a-c) rotatably supported with respect to the shaft about a rotational axis ( 46 ;  246 ;  346 ), 
 a bearing gap ( 20 ,  220 ;  320 ) open at both ends filled with a bearing fluid that separates the adjoining surfaces of the shaft ( 12 ;  212 ;  312 ), the rotor component ( 14 ,  114 a;  214 ;  214 a-c) and at least one first bearing part ( 16 ,  216 ;  316 ) from one another, a first radial bearing ( 22 a,  222 a;  322 a) and a second radial bearing ( 22 b,  222 b;  322 b) formed between the opposing axially extending bearing surfaces of the shaft ( 12 ;  212 ;  312 ) and the rotor component ( 14 ,  114 a;  214 ;  314 a-c), 
 an axial bearing ( 26 ,  226 ;  326 ) formed between the opposing radially extending bearing surfaces of the rotor component ( 14 ,  114 a;  214 ;  314 a-c) and the first bearing part ( 16 ,  216 ;  316 ) connected to the baseplate, 
 a recirculation channel ( 28 ;  128 ;  228 ;  328 ) filled with bearing fluid that connects the remote regions of the bearing to each other, and 
 an electromagnetic drive system ( 42 ,  44 ;  342 ,  244 ) for driving the rotor component, 
 characterized in that the recirculation channel ( 28 ,  128 ;  228 ) is disposed in the rotor component ( 14 ;  114 a;  214 ) and connects a sealing gap ( 34 ) radially outside the axial bearing ( 26 ) to a section of the bearing gap ( 20 ) adjacent to a dynamic pumping seal ( 136 ).