Voice coil motor composite magnet assembly containing low coercivity magnet material

Abstract

To provide an alternative to rare earth magnetic materials for use in VCM of HDD while considering cost and environmental issues.SOLUTION: In a voice coil motor (VCM), a composite magnet assembly 200 includes: a coil; a first yoke 202a having a coil side facing the coil on a first side; a first low coercivity permanent magnet 204a positioned between the coil and the coil side of the first yoke and having a yoke side facing the first yoke and a coil side facing the yoke side; and a first high coercivity permanent magnet 205a adjacent to the coil side of the first low coercivity permanent magnet. The second side of the opposite side of the coil is similarly constructed. A permeance coefficient of the VCM allows for magnetic stability of a low coercivity magnetic material, and if a relative thickness of a magnet material so dictates by design, an additional high coercivity permanent magnet is bonded to the coil side of each of the first and second yokes and adjacent to the yoke side of the low coercivity permanent magnet.SELECTED DRAWING: Figure 2A

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present invention relate generally to voice coil motors, and more particularly to hard disk drive rotary voice coil actuators having composite magnet assemblies including low coercivity magnetic materials. [Background technology]

[0002] A hard disk drive (HDD) is a non-volatile storage device that stores digitally encoded data on one or more circular disks that are housed in a protective enclosure and have magnetic surfaces. When an HDD is in operation, each magnetic recording disk is rapidly rotated by a spindle system. Data is read from and written to the magnetic recording disks using a read-write head (or "transducer") housed on a slider that is positioned over specific locations on the disks by an actuator. The read-write head uses a magnetic field to write data to and read data from the surface of the magnetic recording disk. The write head works by generating a magnetic field using an electric current that flows through the coil of the write head. Electrical pulses are sent to the write head with different patterns of positive and negative currents. The electric current in the coil of the write head creates a localized magnetic field across the gap between the head and the magnetic recording disk, which in turn magnetizes small areas on the recording medium.

[0003] Typically, a voice coil motor (VCM) is a type of actuator employed in HDDs to move a read-write head to access a portion of a corresponding magnetic recording disk for reading and writing operations. VCMs rely on permanent magnets for their own persistent magnetic field. Such field is typically strongest at the magnet surface and decreases with distance therefrom, and thus the magnetic flux density decreases with distance from the magnet as well. Additionally, the cost of permanent magnets is typically proportional to the corresponding grade of magnet and the material from which the magnet is made, with higher grades indicating stronger magnets. Rare earth magnets are strong permanent magnets made from alloys of rare earth elements, typically neodymium magnets and samarium cobalt magnets, for example. Historically, rare earth magnets have been implemented in VCMs of HDDs because they are the strongest type of permanent magnets from which magnets are made and generate a much stronger magnetic field than other types. With respect to rare earth materials, environmental concerns as well as cost concerns exist since they are typically extracted from ores that may contain radioactive materials such as thorium, and extracting the required rare earths typically requires the use of significant amounts of carcinogenic compounds such as ammonia, hydrochloric acid, and sulfuric acid. In view of the above, alternatives to rare earth magnetic materials for use in the VCM of HDDs may be desirable.

[0004] The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Thus, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section. [Brief description of the drawings]

[0005] Embodiments are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numbers refer to similar elements and in which: [Figure 1] 1 is a plan view illustrating a hard disk drive (HDD) according to an embodiment. [Figure 2A] FIG. 2 is a perspective view illustrating a compound magnet assembly for a voice coil motor according to an embodiment. [Figure 2B] FIG. 2B is a side view illustrating the compound magnet assembly of FIG. 2A according to an embodiment. [Figure 3A] FIG. 2 is a side view illustrating a single skin compound magnet assembly for a voice coil motor (VCM) according to an embodiment. [Figure 3B] FIG. 2 is a side view illustrating a dual skin compound magnet assembly for a voice coil motor (VCM) according to an embodiment. [Figure 4] FIG. 1 is a flow diagram illustrating a method of assembling a voice coil motor according to an embodiment. [Diagram 5] FIG. 1 is a flow diagram illustrating a method of assembling a voice coil motor according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] In general, an approach to a voice coil motor (VCM) actuator having a composite magnet assembly including low coercivity magnetic materials for use in hard disk drives (HDDs) and the like is described. In the following specification, 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 are represented in block diagram form in order to avoid unnecessarily obscuring the embodiments of the invention described herein.

[0007] introduction term References herein to "an embodiment," "one embodiment," and the like are intended to mean that the particular feature, structure, or characteristic being described is included in at least one embodiment of the invention. However, instances of such phrases do not necessarily all refer to the same embodiment.

[0008] It will be understood that the term "substantially" describes features that are largely or approximately structured, configured, dimensioned, etc., but that manufacturing tolerances and the like may result in situations where in practice the structure, configuration, dimensions, etc. are not always or necessarily precisely as described. For example, if one describes a structure as being "substantially vertical," the term is assigned its obvious meaning such that the sidewalls are for all practical purposes vertical, but may not be at exactly 90 degrees.

[0009] Terms such as "optimal," "optimize," "minimal," "minimize," "maximum," "maximize," and the like may not have a specific value associated with them, but when such terms are used herein, those of skill in the art are intended to understand that such terms include affecting values, parameters, metrics, and the like in a beneficial direction consistent with the entirety of this disclosure. For example, describing some value as a "minimum" does not require that the value actually be equal to a theoretical minimum (e.g., zero), but should be understood in a practical sense in that the corresponding goal would be to move the value in a beneficial direction toward the theoretical minimum.

[0010] context Recall that alternatives to rare earth magnetic materials for use in the VCM of HDDs may be desirable. New classes of magnetic materials are entering the market in which certain rare earth materials are reduced or eliminated. These materials can enable significant performance, but at the expense of lower magnetic coercivity (H C , a measure of a ferromagnetic material's ability to withstand an external magnetic field without being demagnetized. This characteristic is due to the relatively low permeance coefficient (P C , i.e., magnetic flux density B d and magnetic field strength H dThis, together with the magnet's operating point or "operating slope" on the BH curve, or essentially the material utilization efficiency, poses implementation challenges for this new class of magnetic materials. Specifically, low coercivity magnetic materials have a relatively low P C The application of this technique entails the risk of demagnetization, and the P C is highly dependent on the geometry of the system components, e.g., the pancake shape of the VCM in a typical HDD.

[0011] Composite magnet assembly for voice coil motor Therefore, one challenge identified with implementing low coercivity magnetic materials in the VCM of HDDs is how to increase the permeance coefficient of such VCMs to allow for magnetic stability of these new magnetic materials. According to embodiments, the weakest areas of the low coercivity magnets are effectively replaced with high coercivity magnets, increasing the P C In the context of, the outer surface of the magnet is the weakest region. Stated differently, this approach effectively replaces the material in the unstable regions (of low coercivity material) with a more stable high coercivity material.

[0012] Figure 2A is a perspective view illustrating a compound magnet assembly for a voice coil motor according to an embodiment, and Figure 2B is a side view illustrating the compound magnet assembly of Figure 2A according to an embodiment. The assembly 200 includes a first yoke 202a (e.g., a steel plate) having an air side or coil side that faces a coil (not shown) when installed, a first low coercivity permanent magnet 204a positioned between the coil and the coil side of the first yoke 202a and having a yoke side facing the first yoke 202a and a coil side opposite the yoke side, and a first high coercivity permanent magnet 205a adjacent the coil side of the first low coercivity magnet 204a. Similarly, the other side of the assembly 200 comprises a second yoke 202b having an air side, or coil side facing the coil when installed, a second low coercivity permanent magnet 204b positioned between the coil and the coil side of the second yoke 202b and having a yoke side facing the second yoke 202b and a coil side opposite the yoke side, and a second high coercivity permanent magnet 205b adjacent the coil side of the second low coercivity magnet 204b. Each of the permanent magnets 204a, 205a, 204b, 205b comprises a permanent magnet magnetized to have a north magnetic pole and an adjacent south magnetic pole on each side of a boundary line. The assembly 200 is designed to be a component of a voice coil motor (VCM) for use in hard disk drives (see HDD 100 in FIG. 1), and the like, and further comprises a coil (see coil 306 in FIG. 3A-3B) positioned between the two sides of the assembly 200. Thus, the volume of magnetic material in the weakest region of each of the relatively magnetically unstable low coercivity magnets 204a, 204b is effectively replaced with the volume of magnetic material of the corresponding magnetically stable high coercivity magnets 205a, 205b. Note the contrast with the magnet arrangement of the Halbach array, which is configured to increase the magnetic field and therefore increase the P contrary to the intended purpose of the embodiments described herein. C Additionally, Halbach arrays specifically require magnetic components whose fields are oriented approximately perpendicular to the orientation of the main magnet field, where, according to embodiments, the high and low coercivity fields are aligned.

[0013] As a non-limiting example, a "low coercivity magnet," such as each of the low coercivity magnets 204a, 204b, is a magnet that has a typical coercivity (H) of less than about 10,000 Oersteds (10 kOe) at ambient temperature. Cn ), and a "high coercivity magnet," such as each of high coercivity magnets 205a, 205b, refers to a permanent magnet having a typical coercivity (H Cn ) around the circumference of the high coercivity magnets 205a, 205b. Additionally, although the shape, profile, and footprint of each of the high coercivity magnets 205a, 205b preferably substantially covers the corresponding low coercivity magnets 204a, 204b by area, the shape of each permanent magnet is not necessarily identical and may vary from implementation to implementation. For example, material cost savings may be realized when the high coercivity magnets have a slightly smaller footprint / profile than the low coercivity magnets, e.g., about 1 millimeter (mm) smaller around the circumference of the high coercivity magnets, while still maintaining suitability for the intended purpose.

[0014] 3A is a side view illustrating a single skin compound magnet assembly for a voice coil motor (VCM) according to an embodiment. Assembly 300 is generally referred to herein as a "single skin" magnet assembly because it uses only a single high coercivity magnet 205a, 205b to cover and enhance the efficiency and stability of each of the corresponding low coercivity magnets 204a, 204b, whereby single skin assembly 300 is configured similarly to assembly 200 (FIGS. 2A-2B), and similarly assembly 200 is equivalently represented by the diagram of FIG. 3A. Thus, the assembly 300 comprises a first yoke 302a (e.g., a steel plate) having coil sides 302a-c facing the coil 306, a first low coercivity permanent magnet 304a positioned between the coil 306 and the coil sides 302a-c of the first yoke 302a and having yoke sides 304a-y facing the first yoke 302a and coil sides 304a-c opposite the yoke sides 304a-y, and a first high coercivity permanent magnet 305a adjacent the coil sides 304a-c of the first low coercivity magnet 304a. Similarly, the other side of the assembly 300 comprises a second yoke 302b (e.g., a steel plate) having a coil side 302b-c facing the coil 306, a second low coercivity permanent magnet 304b positioned between the coil 306 and the coil side 302b-c of the second yoke 302b and having a yoke side 304b-y facing the second yoke 302b and a coil side 304b-c opposite the yoke side 304b-y, and a second high coercivity permanent magnet 305b adjacent the coil side 304b-c of the second low coercivity magnet 304b. According to an embodiment, the first high coercivity permanent magnet 305a and the second high coercivity permanent magnet 305b each include a rare earth element (as non-limiting examples, a neodymium-based alloy such as NdFeB, or a samarium-based alloy such as SmCo or SmFeN), and the first low coercivity permanent magnet 304a and the second low coercivity permanent magnet 304b each include a non-rare earth element (as non-limiting examples, an iron nitride-based alloy, or an iron-nickel-based alloy).Additionally, each of the first low coercivity permanent magnet 304a and the second low coercivity permanent magnet 304b may include a reduced rare earth magnet, whereby a relatively small amount of rare earth material (e.g., Nd) is still used, but is largely / mostly replaced with a different element and / or other rare earth elements are eliminated and replaced with other elements. It should be noted that the foregoing permanent magnet compositions are presented as non-limiting examples, as such types of low coercivity permanent magnets are still under development.

[0015] Thus, according to an embodiment, the first low-coercivity permanent magnet 304a is bonded (or glued or attached or otherwise coupled) to the coil sides 302a-c of the first yoke 302a, and the second low-coercivity permanent magnet 304b is bonded (or glued or attached or otherwise coupled) to the coil sides 302b-c of the second yoke 302b. Continuing, according to an embodiment, the first high-coercivity permanent magnet 305a is likewise bonded to the coil sides 304a-c of the first low-coercivity magnet 304a, and the second high-coercivity permanent magnet 305b is likewise bonded to the coil sides 304b-c of the second low-coercivity magnet 304b.

[0016] According to the single-skin embodiment of the assembly 300, the P of the air side (also referred to as the coil side 304a-c, 304b-c) of each of the low-coercivity permanent magnets 304a, 304b C is the P of the steel side (also referred to as the yoke side 304a-y, 304b-y) C At some point in the design of the increasingly thicker high coercivity permanent magnets 305a, 305b (and correspondingly thinner low coercivity permanent magnets 304a, 304b while maintaining the overall thickness of the magnets), the air side of each of the low coercivity permanent magnets 304a, 304b is no longer at its limit (i.e., the P of the air side surface C However, P on the yoke side surface CInstead, for stability purposes, the system is now limited by the interface of each of the low coercivity permanent magnets 304a, 304b and the corresponding steel plate (also referred to as yokes 302a, 302b), rather than at the low coercivity permanent magnets 304a / 305a / high coercivity permanent magnets 304b / 305b interfaces. Thus, at this design point (as a non-limiting example, P C approaching 1.2) and therefore a double skin or "sandwich" design is preferred to continue to improve the stability of the magnetic system.

[0017] 3B is a side view illustrating a double skin compound magnet assembly for a voice coil motor (VCM) according to an embodiment. The assembly 350 is generally referred to herein as a "double skin" magnet assembly because a pair of high coercivity magnets 355a / 357a, 355b / 357b are used to sandwich each of the corresponding low coercivity magnets 354a, 354b to further enhance efficiency and stability. Thus, the assembly 350 comprises a first yoke 352a (e.g., a steel plate) having a coil side 352a-c facing the coil 356, a first low coercivity permanent magnet 354a positioned between the coil 356 and the coil side 352a-c of the first yoke 352a and having a yoke side 354a-y facing the first yoke 352a and a coil side 354a-c opposite the yoke side 354a-y, and a first high coercivity permanent magnet 355a adjacent the coil side 354a-c of the first low coercivity magnet 354a. Similarly, the other side of the assembly 350 comprises a second yoke 352b (e.g., a steel plate) having a coil side 352b-c facing the coil 356, a second low coercivity permanent magnet 354b positioned between the coil 356 and the coil side 352b-c of the second yoke 352b and having a yoke side 354b-y facing the second yoke 352b and a coil side 354b-c opposite the yoke side 354b-y, and a second high coercivity permanent magnet 355b adjacent to the coil side 354b-c of the first low coercivity magnet 354b.

[0018] According to an embodiment, the assembly 350 further comprises a third high coercivity permanent magnet 357a bonded (or glued, attached or otherwise coupled) to the coil side 352a-c of the first yoke 352a and adjacent to the yoke side 354a-y of the first low coercivity permanent magnet 354a, and a fourth high coercivity permanent magnet 357b bonded (or glued, attached or otherwise coupled) to the coil side 352b-c of the second yoke 352b and adjacent to the yoke side 354b-y of the second low coercivity permanent magnet 354b. Thus, according to the embodiment, the first low coercivity permanent magnet 354a is joined to the coil side 357a-c of the third high coercivity permanent magnet 357a, and the second low coercivity permanent magnet 354b is joined to the coil side 357b-c of the fourth high coercivity permanent magnet 357b. Continuing, according to the embodiment, the first high coercivity permanent magnet 355a is joined to the coil side 354a-c of the first low coercivity permanent magnet 354a, and the second high coercivity permanent magnet 355b is joined to the coil side 354b-c of the second low coercivity permanent magnet 354b.

[0019] According to the assembly 300 of FIG. 3A, in terms of the relative thickness of each low coercivity permanent magnet 304a, 304b, 354a, 354b to each of the corresponding high coercivity permanent magnets 305a, 305b, 355a / 357a, 355b / 357b, the majority of the magnet volume remains in the respective low coercivity permanent magnets 304a, 304b, 354a, 354b. As a non-limiting example, a suitable thickness ratio for a single skin configuration may be about 25-33% high coercivity permanent magnets (skins) to 67-75% low coercivity permanent magnets (cores). As another non-limiting example in the context of a double skin configuration, a suitable thickness ratio may be up to about 50% for the low coercivity permanent magnets (cores) to about 33% for each of the high and low coercivity permanent magnets (each core and two skins). This approach is believed to be of little or diminishing benefit beyond the thickness of such high coercivity permanent magnets.

[0020] How to Assemble a Voice Coil Motor Figure 4 is a flow diagram illustrating a method of assembling a voice coil motor according to an embodiment. For example, the method of Figure 4 may be employed to assemble a VCM having compound magnets as illustrated and described elsewhere herein. That is, the method of Figure 4 may be employed to assemble a VCM having compound magnets 204a / 205a, 204b / 205b (Figures 2A-2B) and / or compound magnets 304a / 305a, 304b / 305b (Figure 3A).

[0021] At block 402, a first low coercivity permanent magnet material is bonded to a coil side of a first yoke, the first low coercivity permanent magnet material having a yoke side facing the first yoke and a coil side opposing the yoke side. For example, the material of the first low coercivity permanent magnet 204a (FIGS. 2A-2B), 304a (FIG. 3A) is bonded to the coil side (FIGS. 2A-2B) 302a-c (FIG. 3A) of the first yoke 202a (FIGS. 2A-2B), 302a (FIG. 3A), and the first low coercivity permanent magnet material 204a, 304a has a yoke side (FIGS. 2A-2B), 304a-y (FIG. 3A) facing the first yoke 202a, 302a, and a coil side (FIGS. 2A-2B) 304a-c (FIG. 3A) facing the yoke side 304a-y.

[0022] At block 404, a first high coercivity permanent magnet material is bonded to the coil side of a first low coercivity magnet material. For example, the material of the first high coercivity permanent magnet 205a (FIGS. 2A-2B), 305a (FIG. 3A) is bonded to the coil side 304a-c of the first low coercivity magnet 204a, 304a.

[0023] In block 406, the first low coercivity permanent magnet material and the first high coercivity permanent magnet material are magnetized to form the first low coercivity permanent magnet and the first high coercivity permanent magnet. For example, the material of the first low coercivity permanent magnet 204a, 304a and the material of the first high coercivity permanent magnet 205a, 305a are appropriately magnetized when joined to the first yoke 202a, 302a to form the first low coercivity permanent magnet 204a, 304a and the first high coercivity permanent magnet 205a, 305a.

[0024] Similarly, blocks 402-406 can be executed to assemble a similar sub-assembly for the opposing magnet-yoke portion of the VCM, which can be assembled with another similar sub-assembly to form a top-bottom pair of the VCM.

[0025] 5 is a flow diagram illustrating a method of assembling a voice coil motor according to an embodiment. For example, the method of FIG. 5 may be employed to assemble a VCM having compound magnets as illustrated and described elsewhere herein. That is, the method of FIG. 5 may be employed to assemble a VCM having compound magnets 357a / 354a / 355a, 357b / 354b / 355b (FIG. 3B).

[0026] At block 502, a first high coercivity permanent magnet material is bonded to a coil side of a first yoke, the first high coercivity permanent magnet material having a yoke side facing the first yoke and a coil side opposing the yoke side. For example, the material of the first high coercivity permanent magnet 357a (FIG. 3B) is bonded to the coil sides 352a-c (FIG. 3B) of the first yoke 352a (FIG. 3B).

[0027] At block 504, a first low coercivity permanent magnet material is bonded to a coil side of a first high coercivity permanent magnet material, the first low coercivity permanent magnet material having a yoke side facing the first yoke and a coil side opposite the yoke side. For example, the material of the first low coercivity permanent magnet 354a (FIG. 3B) is bonded to the material of the first high coercivity permanent magnet 357a.

[0028] At block 506, a second high coercivity permanent magnet material is bonded to the coil side of the first low coercivity magnet material. For example, the material of the second high coercivity permanent magnet 355a (FIG. 3B) is bonded to the material of the first low coercivity permanent magnet 354a.

[0029] At block 508, the first low coercivity permanent magnet material and the first and second high coercivity permanent magnet materials are magnetized to form a first low coercivity permanent magnet, a first high coercivity permanent magnet, and a second high coercivity permanent magnet. For example, the material of the first low coercivity permanent magnet 354a and the material of the first and second high coercivity permanent magnets 355a, 357a are appropriately magnetized when joined to the first yoke 352a to form the first low coercivity permanent magnet 354a and the first and second high coercivity permanent magnets 355a, 357a.

[0030] Similarly, blocks 502-508 can be executed to assemble a similar sub-assembly for the opposing magnet-yoke portion of the VCM, which can be assembled with another similar sub-assembly to form a top-bottom pair of the VCM.

[0031] The above approach effectively replaces the magnetic material volume in the weakest region of each of the relatively magnetically unstable low coercivity magnets with the magnetic material volume of the corresponding magnetically stable high coercivity magnet. This allows for the implementation of low coercivity (e.g., non-rare earth or low rare earth) magnetic materials in the VCM of the HDD, which are associated with cost and / or environmental savings, while maintaining a suitable permeance coefficient by enabling the magnetic stability of these newer magnetic materials.

[0032] Illustrative physical description of the operating context Embodiments may be used in the context of a digital data storage device (DSD), such as a hard disk drive (HDD). Thus, according to an embodiment, a plan view illustrating a conventional HDD 100 is shown in FIG. 1 to help explain how a conventional HDD typically operates.

[0033] FIG. 1 illustrates the functional arrangement of components of a HDD 100, including a slider 110b that includes a magnetic read-write head 110a. Collectively, the slider 110b and the head 110a may be referred to as a head slider. The HDD 100 includes at least one head gimbal assembly (HGA) 110 that includes the head slider, a lead suspension 110c that is typically attached to the head slider via a flexure, and a load beam 110d that is attached to the lead suspension 110c. The HDD 100 also includes at least one recording medium 120 that is rotatably mounted on a spindle 124, and a drive motor (not visible) that is attached to the spindle 124 to rotate the medium 120. The read-write head 110a, which may also be referred to as a transducer, includes a write element and a read element for writing and reading information stored on the medium 120 of the HDD 100, respectively. The medium 120 or multiple disk media may be secured to a spindle 124 with a disk clamp 128 .

[0034] The HDD 100 further includes an arm 132 attached to the HGA 110, a carriage 134, and a voice coil motor (VCM) including an armature 136 including a voice coil 140 attached to the carriage 134, and a stator 144 including a voice coil magnet (not shown). The VCM armature 136 is attached to the carriage 134 and is configured to move the arm 132 and HGA 110 to access portions of the media 120, all collectively mounted on a pivot shaft 148 with an intervening pivot bearing assembly 152. In a HDD with multiple disks, the carriage 134 may be referred to as an "E-block" or comb because the carriage is arranged to carry an array of interlocking arms that give the carriage the appearance of a comb.

[0035] An assembly comprising a head gimbal assembly (e.g., HGA 110), including a flexure to which a head slider is coupled, an actuator arm (e.g., arm 132) and / or a load beam to which the flexure is coupled, and an actuator (e.g., VCM) to which the actuator arm is coupled, may be collectively referred to as a head-stack assembly (HSA). However, an HSA may include more or less components than those described. For example, an HSA may refer to an assembly that further includes electrical interconnect components. In general, an HSA is an assembly configured to move a head slider to access portions of a medium 120 for read and write operations.

[0036] With further reference to FIG. 1 , electrical signals including write signals to and read signals from head 110a (e.g., current to the voice coil 140 of the VCM) are transmitted by a flexible cable assembly (FCA) 156 (or “flex cable,” or “flexible printed circuit” (FPC)). The interconnect between flex cable 156 and head 110a may include an arm-electronics (AE) module 160, which may have on-board preamplifiers for the read signal, as well as other read channel and write channel electronics. The AE module 160 may be mounted to the carriage 134 as shown. The flex cable 156 may be coupled to an electrical connector block 164, which in some configurations provides electrical communication through an electrical feedthrough provided by an HDD enclosure 168. The HDD housing 168 (or "enclosure base" or "base plate" or simply "base" or "motor base assembly"), together with the HDD cover, provides a semi-sealed (or, in some configurations, hermetically sealed) protective enclosure for the information storage components of the HDD 100.

[0037] A disk controller including a digital-signal processor (DSP) and other electronic components including servo electronics provide electrical signals to the drive motor, the voice coil 140 of the VCM, and the head 110a of the HGA 110. The electrical signals provided to the drive motor enable the drive motor to rotate providing a torque to the spindle 124, which is then transferred to the medium 120 attached to the spindle 124. As a result, the medium 120 rotates in a direction 172. The rotating medium 120 forms a cushion of air that acts as an air bearing on which the air-bearing surface (ABS) of the slider 110b rides so that the slider 110b flies above the surface of the medium 120 without contacting the thin magnetic recording layer on which the information is recorded. Similarly, in HDDs where a lighter-than-air gas such as helium is utilized as a non-limiting example, the rotating medium 120 creates a cushion of gas that acts as a gas or fluid bearing on which the slider 110b rides.

[0038] An electrical signal provided to the voice coil 140 of the VCM enables the head 110a of the HGA 110 to access the track 176 on which information is to be recorded. Thus, the armature 136 of the VCM swings through an arc 180 to enable the head 110a of the HGA 110 to access various tracks on the medium 120. Information is stored on the medium 120 in a number of radially nested tracks arranged in sectors on the medium 120, such as sector 184. Correspondingly, each track is made up of a number of sectorized track portions (or "track sectors"), such as sectorized track portion 188. Each sectorized track portion 188 may include the recorded information and a header that includes error correction code information and a servo burst signal pattern, such as an ABCD servo burst signal pattern, which is information identifying the track 176. When accessing track 176, a read element of head 110a of HGA 110 reads a servo burst signal pattern that provides a position-error-signal (PES) to the servo electronics, which enables head 110a to follow track 176 by controlling an electrical signal provided to the voice coil 140 of the VCM. Upon locating track 176 and identifying a particular sectored track portion 188, head 110a reads information from track 176 or writes information to track 176 in response to instructions received by a disk controller from an external agent, e.g., a microprocessor of a computer system.

[0039] The electronic architecture of an HDD includes numerous electronic components, such as a hard disk controller (HDC), an interface controller, an arm electronics module, a data channel, a motor driver, a servo processor, a buffer memory, etc., each performing its respective function for the operation of the HDD. Two or more of such components may be combined on a single integrated circuit board referred to as a "system on a chip" (SOC). Some, but not all, of such electronic components are typically located on a printed circuit board that is coupled to the bottom side of the HDD, such as the HDD housing 168.

[0040] References herein to hard disk drives, such as HDD 100 illustrated and described with reference to FIG. 1, may encompass information storage devices that may be referred to as "hybrid drives." A hybrid drive generally refers to a storage device that has the functionality of both a traditional HDD (see, e.g., HDD 100) combined with a solid-state storage device (SSD) that uses non-volatile memory, such as electrically erasable and programmable flash or other solid-state (e.g., integrated circuit) memory. Because the operation, management, and control of different types of storage media are typically different, the solid-state portion of a hybrid drive may include its own corresponding controller functionality, and the controller functionality may be integrated into a single controller along with the HDD functionality. A hybrid drive may be designed and configured to operate and utilize the solid-state portion in several ways, such as by using the solid-state memory as a cache memory, as a non-limiting example, to store frequently accessed data, to store I / O intensive data, and the like. Additionally, a hybrid drive may be essentially designed and configured as two storage devices, a traditional HDD and an SSD, in a single enclosure, with either one or multiple interfaces for host connection.

[0041] Augmentations and Alternatives In the foregoing description, the embodiments of the present invention have been described with reference to numerous specific details that may vary from implementation to implementation. Thus, various modifications and changes may be made without departing from the broader spirit and scope of the embodiments. Thus, the sole and exclusive referent of what is the invention, and what the applicants intend to be the invention, is the set of claims originating from this application, in the specific form from which such claims originate, including any subsequent amendments. The definitions expressly set forth herein for the terms contained in such claims shall govern the meaning of the terms as used in the claims. Hence, any limitations, elements, characteristics, features, advantages or attributes not expressly recited in the claims should in no way limit the scope of such claims. Hereby, the specification and drawings are to be regarded as illustrative, and not restrictive.

[0042] Additionally, certain process steps may be described herein in a particular order, and alphabetic and alphanumeric symbols may be used to identify certain steps. Unless specifically stated herein, embodiments are not necessarily limited to any particular order of performing such steps. In particular, symbols are used merely for convenient identification of steps, and are not intended to specify or require a particular order of performing such steps.

Claims

1. A voice coil motor (VCM), A coil and a first yoke having a coil side facing the coil; a first low coercivity permanent magnet positioned between the coil and the coil side of the first yoke, the first low coercivity permanent magnet having a yoke side facing the first yoke and a coil side opposing the yoke side; a first high coercivity permanent magnet adjacent to the first low coercivity magnet on the coil side; a second yoke having a coil side facing the coil; a second low coercivity permanent magnet positioned between the coil and the coil side of the second yoke, the second low coercivity permanent magnet having a yoke side facing the second yoke and a coil side opposing the yoke side; a second high coercivity permanent magnet adjacent to the coil side of the second low coercivity magnet.

2. 2. The VCM of claim 1, wherein the first low-coercivity permanent magnet is joined to the coil side of the first yoke, and the second low-coercivity permanent magnet is joined to the coil side of the second yoke.

3. 3. The VCM of claim 2, wherein the first high coercivity permanent magnet is bonded to the coil side of the first low coercivity permanent magnet, and the second high coercivity permanent magnet is bonded to the coil side of the second low coercivity permanent magnet.

4. a third high coercive force permanent magnet joined to the coil side of the first yoke and adjacent to the yoke side of the first low coercive force permanent magnet; 2. The VCM of claim 1, further comprising: a fourth high coercivity permanent magnet joined to the coil side of the second yoke and adjacent to the yoke side of the second low coercivity permanent magnet.

5. 5. The VCM of claim 4, wherein the first low coercivity permanent magnet is joined to a coil side of the third high coercivity permanent magnet, and the second low coercivity permanent magnet is joined to a coil side of the fourth high coercivity permanent magnet.

6. 6. The VCM of claim 5, wherein the first high coercivity permanent magnet is bonded to the coil side of the first low coercivity permanent magnet, and the second high coercivity permanent magnet is bonded to the coil side of the second low coercivity permanent magnet.

7. Each of the first and second high coercivity permanent magnets has a normal coercivity (H) of greater than 10 kilo Oersteds (10 kOe) at ambient temperature. Ｃｎ ) Each of the first and second low coercivity permanent magnets has a normal coercivity (H) of less than 10 kilo Oersteds (10 kOe) at ambient temperature. Ｃｎ 2. The VCM of claim 1 .

8. A hard disk drive (HDD), A plurality of disk media rotatably mounted on a spindle motor; a plurality of head sliders, each housing a read-write transducer configured to read from and write to at least one of the plurality of disk media; a voice coil motor (VCM) assembly configured to move the plurality of head sliders to access a portion of the disk medium, the VCM assembly comprising: A coil and a first yoke having a coil side facing the coil; a first low coercivity permanent magnet positioned between the coil and the coil side of the first yoke, the first low coercivity permanent magnet having a yoke side facing the first yoke and a coil side opposing the yoke side; a first high coercivity permanent magnet adjacent to the first low coercivity magnet on the coil side; a second yoke having a coil side facing the coil; a second low coercivity permanent magnet positioned between the coil and the coil side of the second yoke, the second low coercivity permanent magnet having a yoke side facing the second yoke and a coil side opposing the yoke side; a second high coercivity permanent magnet adjacent to the coil side of the second low coercivity magnet;

9. 9. The HDD of claim 8, wherein the first low-coercivity permanent magnet is joined to the coil side of the first yoke, and the second low-coercivity permanent magnet is joined to the coil side of the second yoke.

10. 10. The HDD of claim 9, wherein the first high coercivity permanent magnet is joined to the coil side of the first low coercivity permanent magnet, and the second high coercivity permanent magnet is joined to the coil side of the second low coercivity permanent magnet.

11. a third high coercive force permanent magnet joined to the coil side of the first yoke and adjacent to the yoke side of the first low coercive force permanent magnet; 9. The HDD of claim 8, further comprising: a fourth high coercivity permanent magnet joined to the coil side of the second yoke and adjacent to the yoke side of the second low coercivity permanent magnet.

12. 12. The HDD of claim 11, wherein the first low-coercivity permanent magnet is joined to a coil side of the third high-coercivity permanent magnet, and the second low-coercivity permanent magnet is joined to a coil side of the fourth high-coercivity permanent magnet.

13. 13. The HDD of claim 12, wherein the first high coercivity permanent magnet is joined to the coil side of the first low coercivity permanent magnet, and the second high coercivity permanent magnet is joined to the coil side of the second low coercivity permanent magnet.

14. Each of the first and second high coercivity permanent magnets has a normal coercivity (H) of greater than 10 kilo Oersteds (10 kOe) at ambient temperature. Ｃｎ ) Each of the first and second low coercivity permanent magnets has a normal coercivity (H) of less than 10 kilo Oersteds (10 kOe) at ambient temperature. Ｃｎ 9. The HDD of claim 8 .

15. 1. A method of assembling a voice coil motor (VCM), the method comprising: forming a first subassembly, bonding a first low coercivity permanent magnet material to a coil side of a first yoke, the first low coercivity permanent magnet material having a yoke side facing the first yoke and a coil side opposing the yoke side; joining a first high coercivity permanent magnet material to the coil side of the first low coercivity magnet material; forming a first sub-assembly by magnetizing the first low coercivity permanent magnet material and the first high coercivity permanent magnet material to form a first low coercivity permanent magnet and a first high coercivity permanent magnet.

16. forming a second subassembly according to the method of claim 15; The method of claim 15 , further comprising assembling the first sub-assembly and the second sub-assembly together.

17. 17. A voice coil motor constructed according to the method of claim 16.

18. 1. A method of assembling a voice coil motor (VCM), the method comprising: forming a first subassembly, bonding a first high coercivity permanent magnet material to a coil side of a first yoke, the first high coercivity permanent magnet material having a yoke side facing the first yoke and a coil side opposing the yoke side; bonding a first low coercivity permanent magnet material to the coil side of the first high coercivity magnet material, the first low coercivity permanent magnet material having a yoke side facing the first yoke and a coil side opposite the yoke side; joining a second high coercivity permanent magnet material to the coil side of the first low coercivity magnet material; and magnetizing the first high coercivity permanent magnet material, the first low coercivity permanent magnet material, and the second high coercivity permanent magnet material to form a first high coercivity permanent magnet, a first low coercivity permanent magnet, and a second high coercivity permanent magnet.

19. forming a second subassembly according to the method of claim 17; The method of claim 18 , further comprising assembling the first sub-assembly and the second sub-assembly together.

20. 20. A voice coil motor constructed according to the method of claim 19.

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