Electrostatic microactuator with electrically isolated movable portion and associated drive circuitry

• US 6,853,517 B2
• Filed: 02/13/2003
• Issued: 02/08/2005
• Est. Priority Date: 02/13/2003
• Status: Expired due to Term

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co), Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Hitachi Global Storage Technologies Netherlands BV (Western Digital Corporation)
• Inventors: Hirano, Toshiki, Yang, Henry Hung
• Primary Examiner(s): HEINZ, ALLEN J
• Application Number:
  US10/367,022
• Publication Number:
  US 20040160702A1
• Time in Patent Office: 726 Days
• Field of Search: 3602943-2946
• US Class Current: 360/294.3
• CPC Class Codes: G11B 5/5552 using fine positioning means for track acquisition separate from the coarse (e.g. track changing) positioning means

Abstract

A bidirectional electrostatic rotary microactuator has two sets of fixed electrodes, one set for driving the microactuator counterclockwise and the other set for driving it clockwise, and a rotatable frame that has movable electrodes attached to its outer wall and interleaved between the fixed electrodes. A layer of insulating material is located between the outer wall to which the movable electrodes are attached and the remainder of the frame so that the movable electrodes are electrically isolated. The frame is maintained at ground electrical potential and the movable electrodes at a fixed non-zero electrical potential. The microactuator is driven by applying a plus or minus voltage to one set of fixed electrodes and the opposite voltage to the other set, while maintaining the movable electrodes at a fixed non-zero voltage. The microactuator is usable as a secondary actuator in a disk drive for fine positioning the read/write head.

Claims

1. A disk drive comprising:

a magnetic recording disk having a plurality of data tracks;

a read/write head for reading data from and writing data to the disk;

a primary actuator for coarse positioning the head over a selected track; and

an electrostatic secondary actuator connected to the head and the primary actuator for fine positioning the head over the selected track, the secondary actuator comprising;

a substrate attached to the primary actuator;

a plurality of electrically conductive stationary electrodes formed on the substrate; and

a movable member formed of electrically conductive material and having (a) a frame connected to the substrate and supporting the head, and (b) a plurality of electrically conductive movable electrodes, the frame and supported head being connected to but electrically isolated from the movable electrodes.

2. The disk drive of claim 1 wherein the disk drive includes an air-bearing slider, wherein the read/write head is located on the slider, and wherein the slider is bonded to the frame.

3. The disk drive of claim 1 wherein the primary actuator includes an arm and a suspension attached to the end of the arm, and wherein the substrate of the secondary actuator is attached to the suspension.

4. The disk drive of claim 1 wherein the secondary actuator is a rotary actuator further comprising a post fixed to the substrate, and wherein the frame of the movable member is connected to the post by a plurality of flexible springs, the springs permitting rotation of said frame about said post.

5. The disk drive of claim 1 wherein the movable member of the secondary actuator further comprises (c) a layer of electrically insulating material connecting the movable electrodes to the frame.

6. The disk drive of claim 5 wherein the electrically insulating material comprises a cured photosensitive polymeric material.

7. The disk drive of claim 1 further comprising an electrical device coupled to the movable electrodes for maintaining a fixed non-zero voltage to the movable electrodes when the disk drive is operating.

8. The disk drive of claim 1 wherein the stationary electrodes comprise first and second sets of spaced apart stationary branches, and wherein the movable electrodes comprise spaced apart movable branches interleaved in the spacings between the stationary branches.

9. The disk drive of claim 8 wherein the each movable electrode is interleaved between a stationary electrode of the first set and a stationary electrode of the second set.

10. The disk drive of claim 8 further comprising driver circuitry coupled to the electrostatic actuator, said driver circuitry providing a voltage to the first set of stationary branches in a range between +V and −

V volts and a voltage to the second set of stationary branches in a range between +V and −

V volts.

11. The disk drive of claim 10 wherein the frame is maintained at ground electrical potential and the movable electrodes at a fixed non-zero electrical potential when the disk drive is operating.

12. The disk drive of claim 11 wherein the movable electrodes are maintained at a fixed non-zero electrical potential of −

V volts.

13. The disk drive of claim 12 wherein V is approximately 30 volts.

14. A disk drive comprising:

a base;

a rotatable magnetic recording disk mounted to the base and having a plurality of data tracks;

a read/write head for reading data from and writing data to the disk;

a head carrier for supporting the head near the surface of the disk;

a primary rotary actuator mounted to the base;

an arm having one end attached to the primary rotary actuator;

an electrostatic secondary rotary actuator attached to the other end of said arm and supporting the head carrier, the secondary rotary actuator comprising (a) a substrate attached to said other end of said arm;

(b) first and second sets of spaced apart electrically conductive stationary electrode branches fixed on said substrate;

(c) a central post fixed on the substrate;

(d) a plurality of flexible spring elements extending laterally from the post;

(e) an electrically conductive frame attached to the ends of the spring elements and rotatable about said post, said frame supporting said head carrier and having first and second side walls facing respective first and second sets of stationary branches;

(f) electrically insulating material attached to said first and second side walls; and

(g) a plurality of electrically conductive movable electrode branches attached to the electrically insulating material on said first side wall and interleaved in the spacings between the stationary branches of the first and second stationary sets; and

electrical driver circuitry responsive to a control signal and coupled to the secondary rotary actuator for providing a voltage to each of the first and second sets of stationary branches in a range between +V and −

V volts and for maintaining the movable branches at a fixed non-zero electrical potential, the electrically conductive frame being maintained at electrical ground potential as a result of its electrical isolation by said electrically insulating material.

15. The disk drive of claim 14 wherein V is approximately 30, and wherein said fixed non-zero electrical potential is approximately −

30 volts.

16. The disk drive of claim 14 wherein the electrically insulating material comprises a layer of cured photosensitive polymeric material.

17. The disk drive of claim 14 wherein the head carrier is an air-bearing slider.

18. The disk drive of claim 14 further comprising a bonding platform attached to the frame and supporting the head carrier.

19. The disk drive of claim 14 wherein the movable electrode branches are attached to an outer wall, and wherein the electrically insulating material interconnects said outer wall with said first and second side walls.

20. The disk drive of claim 19 wherein said outer wall and said first and second side walls include extending ribs, wherein the ribs on each side wall are interlocked with the ribs on said outer wall, said interlocking ribs being electrically isolated from each other by the electrically insulating material.

22. The microactuator of claim 20 wherein the electrically insulating material comprises a layer of cured photosensitive polymeric material.

23. The microactuator of claim 20 wherein each movable electrode branch is interleaved between a fixed electrode branch of the first set and a fixed electrode branch of the second set.

21. A rotary electrostatic microactuator comprising:

a substrate having an electrically insulating surface;

first and second sets of spaced apart electrically conductive fixed electrode branches fixed on said insulating substrate surface;

a central post fixed on said insulating substrate surface;

a plurality of flexible spring elements extending laterally from the post;

an electrically conductive frame attached to the ends of the spring elements and rotatable about said post, said frame having inner and outer walls;

electrically insulating material attached to said inner and outer walls and electrically isolating the inner wall from the outer wall;

a plurality of spaced apart electrically conductive movable electrode branches attached to the outer wall and interleaved in the spacings between the fixed electrode branches;

whereby the movable electrode branches are connected to but electrically isolated from the electrically conductive rotatable frame.