CN-121999808-A - Hard disk drive voice coil motor actuator with low density wire coil and high density coil reinforcement

Abstract

A Voice Coil Motor Assembly (VCMA), such as for a hard disk drive, includes a low density voice coil and a high density coil reinforcement disposed inside the wire coil. The low density voice coil is configured to increase the second coil torsional mode frequency of the VCMA using copper clad aluminum or aluminum wire so that it is closer to the second torsional mode frequency of the actuator arm. At the same time, the high density reinforcement is constructed using steel or copper or zinc to increase the mass of the VCMA with respect to its center of mass about its axis of rotation to compensate for the lower density wire. When viewed under client chassis vibration conditions, and in accordance with the Position Error Signal (PES), the non-trivial peaks in the PES spectrum due to the second coil torsional mode are largely eliminated, and the power of the PES is reduced to about half.

Inventors

• Eguchi Kenhiko
• Jiang Kouyi

Assignees

• 西部数据技术公司

Dates

Publication Date

20260508

Application Date

20250612

Priority Date

20241106

Claims (20)

1. 1. A data storage device, the data storage device comprising: A magnetic disk medium rotatably mounted on the spindle; a head slider including a read-write head configured to write to and read from a disk medium of the disk media, and A rotary actuator configured to move the head slider about a pivot to access a portion of the disk medium via actuation of a Voice Coil Motor (VCM) assembly, the VCM assembly comprising: A voice coil including a coil of wire having a first density, and A stiffener disposed inside the wire coil, the stiffener comprising a material having a second density greater than the first density.
2. 2. The data storage device of claim 1, wherein the voice coil is configured to increase a torsional mode frequency of a VCM assembly including wires having a density higher than the first density relative to the torsional mode frequency of the VCM assembly.
3. 3. The data storage device of claim 2, wherein: the VCM assembly further includes a plurality of arms extending from the carriage, and The torsion mode is a second coil torsion mode of the VCM assembly that corresponds to a structural dynamics mode in which the carriage and the plurality of arms tilt in one direction and the VCM assembly tilts in an opposite direction.
4. 4. The data storage device of claim 3, wherein the voice coil is configured to bring the second torsional mode frequency of the VCM assembly closer to a second torsional mode frequency of the plurality of arms.
5. 5. The data storage device of claim 1, wherein the stiffener having the higher second density is configured to increase the mass of the VCM assembly with respect to a center of mass of the VCM assembly about its axis of rotation to compensate for the wire having the lower first density.
6. 6. The data storage device of claim 5, wherein the stiffener is positioned radially inside the wire coil such that a center of mass of the stiffener in a direction opposite a torsional axis of motion is substantially proximate the torsional axis of motion.
7. 7. The data storage device of claim 1, wherein: The wire is composed of a material from the group consisting of (i) copper clad aluminum and (ii) aluminum, and The stiffener material is composed of a material from the group consisting of (i) stainless steel, (ii) copper or copper alloy, and (iii) zinc-aluminum alloy.
8. 8. A Voice Coil Motor (VCM) assembly, the VCM assembly comprising: A voice coil including a coil of wire having a first density, and A stiffener disposed inside the wire coil, the stiffener comprising a material having a second density greater than the first density.
9. 9. The VCM assembly of claim 8, wherein the voice coil is configured to increase a torsional mode frequency of the VCM assembly relative to a torsional mode frequency of a VCM assembly including a voice coil including wires having a density higher than the first density.
10. 10. The VCM assembly of claim 9, further comprising: a plurality of arms extending from the carriage, and Wherein the torsion mode is a second coil torsion mode of the VCM assembly that corresponds to a structural dynamics mode in which the carriage and the plurality of arms are tilted in one direction and the voice coil is tilted in an opposite direction.
11. 11. The VCM assembly of claim 10, wherein the voice coil is configured to bring the second torsional mode frequency of the VCM assembly closer to a second torsional mode frequency of the plurality of arms.
12. 12. The VCM assembly of claim 8, wherein the reinforcement having the higher second density is configured to increase the mass of the VCM assembly with respect to a center of mass of the VCM assembly about its axis of rotation to compensate for the wire having the lower first density.
13. 13. The VCM assembly of claim 12, wherein the stiffener is positioned radially inside the wire coil such that a center of mass of the stiffener in a direction opposite the torsional axis of motion is substantially near the torsional axis of motion.
14. 14. The VCM assembly of claim 8, wherein: The wire is composed of a material from the group consisting of (i) copper clad aluminum and (ii) aluminum.
15. 15. The VCM assembly of claim 14, wherein: the stiffener material is composed of a material from the group consisting of (i) stainless steel, (ii) copper or copper alloy, and (iii) zinc-aluminum alloy.
16. 16. A hard disk drive comprising the VCM assembly according to claim 15.
17. 17. A method of manufacturing a voice coil motor assembly, the method comprising: Forming a voice coil including a wire coil, wherein the wire has a first density, the voice coil being configured to increase a second coil torsional mode frequency of the voice coil motor assembly relative to a second coil torsional mode frequency of a voice coil including a wire having a density higher than the first density, and A stiffener is disposed inside the wire coil, wherein the stiffener comprises a material having a second density greater than the first density and is configured to substantially balance a center of mass of the voice coil motor assembly about its axis of rotation.
18. 18. The method according to claim 17, wherein: the voice coil is formed from a wire material from the group consisting of (i) copper clad aluminum and (ii) aluminum, and Providing the stiffener includes providing a stiffener material composed of a material from the group consisting of (i) stainless steel, (ii) copper or copper alloy, and (iii) zinc-aluminum alloy.
19. 19. A Hard Disk Drive (HDD), the HDD comprising: A magnetic disk medium rotatably mounted on the spindle; for reading from a disk medium of the disk media and means for writing to a disk medium of the disk media; and A rotary actuator configured to move the means for reading and writing to access portions of the disk media via actuation of a Voice Coil Motor (VCM) assembly, the VCM assembly comprising: A voice coil including a wire coil; A reinforcement member provided inside the wire coil; a plurality of arms extending from the carriage, and Means for increasing a second coil torsional mode frequency of the VCM assembly relative to a second coil torsional mode frequency of the VCM assembly that does not otherwise include such means, the second coil torsional mode frequency corresponding to a structural dynamics mode in which the sledge and the plurality of arms are tilted in one direction and the voice coil is tilted in an opposite direction.
20. 20. The HDD of claim 19, wherein: The means for increasing the second coil torsional mode frequency of the VCM assembly is configured to bring the second torsional mode frequency of the VCM assembly closer to a second torsional mode frequency of the plurality of arms, and The VCM assembly also includes means for substantially balancing a center of mass of the VCM assembly about its axis of rotation.

Description

Hard disk drive voice coil motor actuator with low density wire coil and high density coil reinforcement Technical Field Embodiments of the present invention may relate generally to data storage devices, such as hard disk drives, and in particular to methods for improving the structural dynamics of voice coil motor assemblies in hard disk drives. Background Hard Disk Drives (HDDs) are nonvolatile storage devices that are housed in a protective enclosure and store digitally encoded data on one or more circular magnetic disks having a magnetic surface. When the HDD is in operation, each magnetic-recording disk is rapidly rotated by the spindle system. Data is read from and written to the magnetic recording disk using a read-write transducer (or read-write "head") positioned by an actuator over a particular location of the disk. The read/write heads use a magnetic field to write data to and read data from the surface of the magnetic recording disk. The write head operates by using a current flowing through its coil, thereby generating a magnetic field. The electrical pulses are sent to the write head in different modes of positive and negative current. The current in the coil of the write head creates a local magnetic field in the gap between the head and the disk, which in turn magnetizes a small area on the recording medium. The HDD includes at least one Head Gimbal Assembly (HGA) and a suspension, the Head Gimbal Assembly (HGA) typically including a slider housing a read/write head. Each slider is attached to a free end of the suspension, which in turn extends from a rigid arm suspension of the actuator. Several actuator arms may be combined to form a single movable unit, i.e. a Head Stack Assembly (HSA), typically having a rotary pivot bearing system. The suspension of a conventional HDD typically includes a relatively rigid load beam having a mounting plate at its base end that is attached to the actuator arm and its free end mounts a flexure that carries the slider and its read and write heads. As networked computing systems grow in number and functionality, so too does the demand for data storage system capacity. Cloud computing and large-scale data processing further increase the demand for digital data storage systems capable of transmitting and containing large amounts of data. For this reason, increasing the storage capacity of the HDD is one of the continuous targets of HDD technology evolution. In contemporary HDDs, operating vibration (also referred to as "client box vibration") is one of the most significant contributors to Track Misregistration (TMR), where TMR generally refers to the variance of the position of the track following/servo head relative to where it should be, i.e., the deviation of the read/write head from the data track center. Key contributors to operating vibration are (a) acoustic excitation caused by air pressure fluctuations from the cooling fan and (b) external vibration transmitted structurally. Any method that may be described in this section is a method that may be practiced, but is not necessarily a method that has been previously conceived or pursued. Therefore, unless otherwise indicated, any approaches described in this section are not to be construed so as to qualify as prior art merely by virtue of their inclusion in this section. Drawings Embodiments are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements and in which: FIG. 1 is a plan view illustrating a Hard Disk Drive (HDD) according to one embodiment; FIG. 2 is a perspective view illustrating a Voice Coil Motor (VCM) assembly according to one embodiment; FIG. 3A is a perspective view illustrating the structural dynamics of a VCM assembly; FIG. 3B is a schematic diagram illustrating a second coil torsional mode of the VCM assembly of FIG. 3A; FIG. 4 is a perspective view illustrating a VCM assembly according to one embodiment, and Fig. 5 is a flowchart illustrating a method of manufacturing a voice coil motor assembly according to one embodiment. Detailed Description Generally, a method of improving structural dynamics of an actuator system in a hard disk drive is described. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention described herein. It will be apparent, however, that the embodiments of the invention described herein may be practiced without these specific details. In other instances, well-known structures and devices may be shown in block diagram form in order to avoid unnecessarily obscuring the embodiments of the invention described herein. Introduction to the invention Terminology Reference herein to "an embodiment," "one embodiment," etc., is intended to mean that a particular feature, structure, or characteristic described is included in at least one embodime