In-pivot stepper motor for ball screw cam elevator mechanism for cold storage data storage device
An approach to a reduced-head hard disk drive (HDD) involves an actuator subsystem that includes a ball screw cam assembly wherein the number of starts of a multi-start screw equals the number of balls riding in a corresponding start. A stepper motor may be disposed within the screw, to drive rotation of the screw, which drives translation of an actuator arm assembly so that a corresponding pair of read-write heads can access different magnetic-recording disks of a multiple-disk stack. The actuator subsystem may further include a cam locking mechanism for coupling and decoupling the actuator arm with a coil support structure and corresponding voice coil, so that the cam mechanism is able to move under the control of a voice coil motor when input/output operations are performed and is able to move the actuator arm assembly during translation operations.
1. An actuator system for a reduced-head hard disk drive (HDD), the system comprising:
a ball screw cam assembly;
a head-stack assembly (HSA) translatably coupled with the cam assembly;
a multi-phase claw-pole stepper motor disposed within and affixed to a screw of the cam assembly, and configured to drive rotation of the screw to drive translation of the HSA along an axis of the screw; and
a fixed shaft around which the stepper motor is positioned;
wherein the stepper motor is rotatable about the fixed shaft to drive the rotation of the screw, the stepper motor comprising:
a hollow tubular permanent magnet, affixed to inner diameter of the screw, that operates as a rotor of the stepper motor,
at least one circular coil disposed within the tubular permanent magnet, and
at least one pair of mated claw-pole structures, disposed within the tubular permanent magnet and in which the at least one coil is disposed, that operate collectively as a stator of the stepper motor.
2. The actuator system of claim 1 , wherein the stepper motor further comprises:
two circular coils disposed within the tubular permanent magnet in a stacked formation; and
a pair of mated claw-pole structures in which a respective coil is disposed.
3. The actuator system of claim 1 , wherein each of the claw-pole structures is configured with five claw-pole teeth.
4. The actuator system of claim 1 , wherein the cam assembly and the disposed stepper motor are configured as an actuator pivot cartridge in the HDD.
5. The actuator system of claim 4 , further comprising:
a pair of head-stack assembly (HSA) pivot bearing assemblies positioned within the pivot cartridge.
6. The actuator system of claim 5 , further comprising:
a pair of cam bearing assemblies positioned within the pivot cartridge outside of the HSA pivot bearing assemblies.
7. The actuator system of claim 1 , further comprising:
a flexible cable assembly (FCA), electrically coupled with head-stack assembly (HSA), comprising a vertical loop providing for translation of the HSA.
8. A hard disk drive comprising the actuator system of claim 7 .
9. The actuator system of claim 1 , wherein the ball screw cam assembly comprises:
a hollow screw comprising at least three starts,
a ball bearing assembly comprising a same number of balls as starts, wherein each ball rides in a corresponding start, thereby forming a plane on which the balls ride perpendicular to the axis of the screw.
10. The actuator system of claim 1 , further comprising:
one or more proximity sensors coupled with the HSA; and
a magnetic encoder strip positioned in close proximity to the one or more proximity sensors, and configured to provide a magnetic field for sensing by the one or more proximity sensors.
11. The actuator system of claim 10 , wherein:
the one or more proximity sensors comprises a plurality of Hall-effect sensors mounted in a quadrature configuration which, in conjunction with the magnetic encoder strip, provides sine and cosine signals for sensing a direction of movement of the HSA and zero-crossing points of the sine-cosine waveforms for sensing an amount of displacement of the HSA.
12. A hard disk drive comprising the actuator system of claim 10 .
13. A hard disk drive comprising the actuator system of claim 1 .
14. A multi-phase claw-pole stepper motor configured to rotate about a fixed shaft, the stepper motor comprising:
a hollow tubular permanent magnet that operates as a rotor;
at least two circular coils disposed within the tubular permanent magnet in a stacked formation; and
a pair of mated claw-pole structures in which each respective circular coil is disposed, disposed within the tubular permanent magnet, that operate collectively as a stator.
15. A hard disk drive (HDD) head-stack assembly (HSA) pivot assembly comprising the multi-phase claw-pole stepper motor of claim 14 disposed within a ball screw cam assembly and configured to drive rotation of the cam assembly to drive vertical translation of the HSA.
16. A method for vertically translating a head-stack assembly (HSA) in a hard disk drive (HDD) to access multiple magnetic-recording disks, the method comprising:
driving a stepper motor disposed within a ball screw cam assembly comprising a multi-start screw, thereby rotating the screw about a coaxial fixed shaft;
allowing a planar multi-ball bearing assembly that is coupled with the HSA to translate vertically, in response to rotating the screw, by each of a particular number of balls of the bearing assembly riding in a corresponding respective start of the same particular number of starts of the multi-start screw; and
while the bearing assembly is translating, sensing the vertical position of the HSA.
17. A reduced-head hard disk drive (HDD), comprising:
recording means for storing digital information;
reading/writing means for reading from and writing to the recording means;
means for moving the reading/writing means to access portions of the recording means;
rotating means for rotating cam means about a fixed shaft for translating the reading/writing means from one recording means to another recording means; and
means for sensing a vertical position of the reading/writing means.
18. An actuator system for a reduced-head hard disk drive (HDD), the system comprising:
a ball screw cam assembly;
a head-stack assembly (HSA) translatably coupled with the cam assembly;
a stepper motor disposed within and affixed to a screw of the cam assembly, and configured to drive rotation of the screw to drive translation of the HSA along an axis of the screw;
one or more proximity sensors coupled with the HSA; and
a magnetic encoder strip positioned in close proximity to the one or more proximity sensors, and configured to provide a magnetic field for sensing by the one or more proximity sensors.
19. The actuator system of claim 18 , wherein:
the one or more proximity sensors comprises a plurality of Hall-effect sensors mounted in a quadrature configuration which, in conjunction with the magnetic encoder strip, provides sine and cosine signals for sensing a direction of movement of the HSA and zero-crossing points of the sine-cosine waveforms for sensing an amount of displacement of the HSA.
20. A hard disk drive comprising the actuator system of claim 18 .