Magnetic bearing for data storage device

Abstract

To provide a hard disc not necessarily requiring an oil-based lubricant and driven by a motor having a magnetic bearing.SOLUTION: A hard disk drive 100 includes: a base deck 102 that is coupled to a cover; a motor assembly 108 that is coupled to the base deck; and a magnetic recording medium 106 that is coupled to the motor assembly, and a horizontal magnetic bearing component is formed by a first magnetic pole 132 and a second magnetic pole 134. A vertical magnetic bearing component is formed by a third magnetic pole 138 and a fourth magnetic pole 140. The motor assembly has a magnetic bearing having the horizontal magnetic bearing component and the vertical magnetic bearing component.SELECTED DRAWING: Figure 3

Description

Summary of the Invention [Problem to be solved by the invention]

[0001] In a specific embodiment, the hard disk drive includes a base deck coupled to a cover, a motor assembly coupled to the base deck, and a magnetic recording medium coupled to the motor assembly, the motor assembly including a magnetic bearing having a horizontal magnetic bearing component and a vertical magnetic bearing component.

[0002] In certain embodiments, the motor assembly includes a stationary component coupled to or including a first magnetic pole having a first magnetic polarity. The motor assembly includes a rotating component coupled to or including a second magnetic pole having a second magnetic polarity that repels the first magnetic polarity. The first and second magnetic poles are positioned relative to one another to form a first pair of repelling magnetic poles to form a horizontal magnetic bearing component. The motor assembly includes a second pair of repelling magnetic poles to form a vertical magnetic bearing component.

[0003] In a specific embodiment, a base deck for a hard disk drive includes a floor portion and a sidewall portion. A motor assembly is coupled to the floor portion and includes a stationary component and a rotating component. The motor assembly includes a magnetic bearing having a horizontal magnetic bearing component and a vertical magnetic bearing component. The magnetic bearing is positioned so that the rotating component levitates and does not contact the stationary component.

[0004] While multiple embodiments are disclosed, other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which further shows and describes illustrative implementations of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 shows an exploded perspective view of a hard disk drive according to a specific embodiment of the present disclosure. [Figure 2]FIG. 2 illustrates a top view of the hard disk drive of FIG. 1, according to certain embodiments of the present disclosure. [Figure 3] FIG. 3 shows a schematic cross-sectional side view of a motor according to certain embodiments of the present disclosure. [Figure 4] FIG. 4 shows a schematic top view of a portion of the motor of FIG. 3, in accordance with certain embodiments of the present disclosure. [Figure 5] FIG. 5 shows a schematic cross-sectional side view of a motor according to certain embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0006] While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. However, the intention is not to limit the disclosure to the particular embodiments described, but instead to cover all modifications, equivalents, and alternatives falling within the scope of the appended claims.

[0007] Detailed Description Data storage devices, such as hard disk drives, use rotatable motors to rotate magnetic media. These motors typically include fluid dynamic bearings or ball bearings. However, both types of bearings use lubricants, including oil, which can leak from the motor and degrade the performance of the data storage device. Therefore, certain embodiments of the present disclosure are directed to motors that do not necessarily require oil-based lubricants. More specifically, certain embodiments feature motors having magnetic bearings.

[0008] Figure 1 shows an exploded perspective view of hard disk drive 100, having a base deck 102 and a top cover 104 that form an enclosure that houses the various components of hard disk drive 100. Figure 2 shows a top view of hard disk drive 100. Not all components shown in Figure 1 are shown in Figure 2, and vice versa.

[0009] The hard disk drive 100 includes a magnetic recording medium 106 (individually referred to as a magnetic recording medium) coupled to a motor assembly 108 by a disk clamp 110. The hard disk drive 100 also includes an actuator assembly 112 that positions a read / write head 114 over data tracks 116 of the magnetic recording medium 106. During operation, the motor assembly 108 rotates the magnetic recording medium 106 while the actuator assembly 112 is driven by a voice coil motor assembly 118 to rotate a pivot bearing 120.

[0010] The read / write head 114 writes data to the magnetic recording medium 106 by generating and emitting a magnetic field toward the magnetic recording medium 106 that induces magnetic polarization transitions on the desired data track 116. The magnetic polarization transitions are representative of data. The read / write head 114 senses (or "reads") the magnetic polarization transitions with a magnetic transducer. As the magnetic recording medium 106 rotates adjacent to the read / write head 114, the magnetic polarization transitions induce a changing magnetic field in the magnetic transducer of the read / write head 114. The magnetic transducer converts the changing magnetic field into a read signal that is sent to a preamplifier and then to a read channel for processing. The read channel converts the read signal into a digital signal that is processed and then provided to a host system (e.g., a server, laptop computer, desktop computer).

[0011] Figure 3 shows a cross-sectional side view of the hard disk drive 100 and the motor assembly 108. Figure 4 shows a top view of a portion of the motor assembly 108. The motor assembly 108 includes stationary and rotating components. As explained in more detail below, the rotating components rotate relative to the stationary components of the motor assembly 108 and function together to form bearings that enable smooth rotation of the motor assembly 108. The bearings shown in Figure 3 are magnetic bearings, as opposed to fluid dynamic or ball bearings.

[0012] 3, the stationary component is a shaft 122 (e.g., a cylindrical shaft), and the rotating component is a rotor 124, which may have a toroidal shaped structure that at least partially surrounds the shaft 122. The shaft 122 extends between the floor of the base deck 102 and the top cover 104. For example, the shaft 122 may be coupled to the floor by fastening (e.g., gluing, welding, press fitting, fastening) the shaft 122 to the floor. The shaft 122 may also be coupled to the top cover 104 through different means, such as by fasteners 125.

[0013] The rotor 124 is coupled to or includes a hub 126. The magnetic recording medium 106 is coupled to the hub 126. Thus, as the hub 126 rotates, the magnetic recording medium 106 and the rotor 124 also rotate. The specific shapes and relative positions of the components of the motor assembly may differ from those shown in the figures. For example, the rotor 124 may have a single inner surface facing the shaft 122 such that the gap between the shaft 122 and the rotor 124 is uniform along most or all of the shaft 122.

[0014] The rotor 124 is rotated by an electromagnetic motor portion of the motor assembly 108. In certain embodiments, the motor assembly 108 includes magnets 128 (e.g., permanent magnets) and stator windings 130. When the stator windings 130 are selectively energized (e.g., by applying current to the stator windings 130), the magnets 128 interact with the magnetic field generated by the energized stator windings 130 to rotate the hub 126. The magnets 128 may be formed as a single annular ring or as multiple individual magnets spaced about the hub 126. The magnets 128 are magnetized to form two or more magnetic poles. Further details regarding the electromagnetic motor portion are described in U.S. Pat. No. 9,196,294, which is incorporated herein by reference for the purpose of providing additional details regarding the electromagnetic motor portion of the motor assemblies described herein.

[0015] As described above, the components coupled to the shaft 122 and rotor 124 (or portions thereof) form a magnetic bearing, as opposed to a fluid bearing or a ball bearing. In particular, the magnetic bearing is formed by one or more pairs of repelling magnetic poles positioned at various locations along the shaft 122 and rotor 124. These repelling magnetic poles levitate or suspend the rotor 124 such that a gap (e.g., an air gap) exists between the shaft 122 and rotor 124 and such that the shaft 122 and rotor 124 do not physically contact each other. Because the shaft 122 and rotor 124 do not contact each other, the motor assembly 108 does not necessarily require the use of lubricant between the shaft 122 and rotor 124 components.

[0016] As mentioned above, lubricant can leak from the motor and into the hard disk drive enclosure. The leaked lubricant can contaminate hard disk drive components, causing errors or even failure. Furthermore, lubricant properties (e.g., viscosity, damping) can change with temperature, resulting in overall performance changes depending on the hard disk drive's environment. Furthermore, during a shock event, motor components with fluid dynamic or ball bearings come into contact with each other (e.g., metal-to-metal contact), which can cause metal chips and affect the performance of the motor and hard disk drive 100. For example, metal chips can become lodged in the interface between the magnetic recording medium 106 and the read / write head 114.

[0017] The use of magnetic bearings helps to alleviate some of the problems mentioned above with fluid bearings and ball bearings, and further allows for the use of motor assemblies with reduced height or diameter compared to motors with fluid bearings or ball bearings.

[0018] 3, the magnetic bearing of the motor assembly 108 includes a horizontal magnetic bearing component and a vertical magnetic bearing component. The horizontal magnetic bearing component is formed by one or more pairs of magnetic poles (e.g., a first magnetic pole 132 and a second magnetic pole 134) that are horizontally spaced apart from one another and have repelling polarities. For example, both the first magnetic pole 132 and the second magnetic pole 134 can have positive or negative polarities such that they repel each other (and thus the shaft 122 and rotor 124 components).

[0019] The first magnetic pole 132 can be coupled to or form part of the shaft 122. For example, a magnet can be coupled to the shaft 122 to form the first magnetic pole 132. As another example, the shaft 122 itself can be magnetized to form the first magnetic pole 132. In certain embodiments, a limited portion of the shaft 122 is magnetized as opposed to the entire shaft 122.

[0020] The second magnetic pole 134 may be coupled to or form part of the rotor 124. For example, a magnet may be coupled to the rotor 124 to form the second magnetic pole 134. As another example, the rotor 124 itself may be magnetized to form the second magnetic pole 134. In certain embodiments, a limited portion of the rotor 124 is magnetized as opposed to the entire rotor 124.

[0021] Because of the repelling magnetic poles, and because the rotor 124 at least partially surrounds the shaft 122 (as shown in FIG. 4 ), the horizontal magnetic bearing components help maintain a horizontal spacing 136 between the shaft 122 and the rotor 124. In other words, the repelling magnetic poles help maintain an air gap between the two components so that the shaft 122 and the rotor 124 do not contact each other. During operation of the motor assembly 108 (e.g., by selectively energizing the stator windings 130), the rotor 124 can rotate about the shaft 122 without contacting the shaft 122 and without requiring lubricant to smooth the rotation. Although only one pair of repelling magnetic poles is indicated by reference numerals in FIG. 3 , the horizontal magnetic bearing components can include multiple pairs of repelling magnetic poles and help maintain a horizontal spacing between the components.

[0022] The vertical magnetic bearing component is formed, at least in part, by a lower pair of magnetic poles (e.g., third pole 138 and fourth pole 140) that are vertically spaced apart from one another and have repelling magnetic poles. For example, both third pole 138 and fourth pole 140 can have positive or negative polarities so as to repel one another.

[0023] The third magnetic pole 138 can be coupled to or form part of the floor of the base deck 102. For example, a magnet or magnetized structure (e.g., a boss-like structure) can be coupled to the base deck 102 to form the third magnetic pole 138. As another example, a portion of the body of the base deck 102 can be magnetized to form the third magnetic pole 138.

[0024] The fourth magnetic pole 140 may be coupled to or form part of the rotor 124. For example, a magnet may be coupled to the rotor 124 to form the fourth magnetic pole 140. As another example, the rotor 124 itself may be magnetized to form the fourth magnetic pole 140.

[0025] The vertical magnetic bearing assembly may further include an upper pair of magnetic poles 142, having vertically spaced apart, repelling magnetic poles. In the embodiment shown in Figure 3, the upper pair of magnetic poles 142 are coupled to or formed by the shaft 122 and the rotor 124, respectively. For example, the shaft 122 may include or be coupled to a cap-like structure 144 or a portion extending horizontally from the shaft 122. This cap-like structure 144 may be coupled to or form the magnetic pole.

[0026] Because the force generated by the repulsion of the upper pair of magnetic poles 142 is in the opposite direction to the force generated by the repulsion of the lower pair of magnetic poles, the vertical magnetic bearing components help maintain vertical spacing between the shaft 122 and the rotor 124, and between the rotor 124 and both the base deck 102 and the top cover 104. In other words, the repulsive magnetic poles help maintain the air gap between these components so that they do not contact one another. For example, the two pairs of magnetic poles vertically suspend or levitate the rotor 124. During operation of the motor assembly 108 (e.g., by energizing the stator windings 130), the rotor 124 can rotate about the shaft 122 without contacting the shaft 122, the floor of the base deck 102, and the top cover 104, and without the need for lubricants to smooth its rotation.

[0027] 5 shows a side cross-sectional view of a portion of a hard disk drive 200 having an alternative design for a motor assembly 202. Similar to the motor assembly 108 shown in FIGS. 3 and 4, the motor assembly 202 includes a stationary component, a rotating component, and a magnetic bearing having a horizontal magnetic bearing component and a vertical magnetic bearing component.

[0028] 5, the stationary component is a sleeve 204 (e.g., a cylindrical sleeve with a central opening), and the rotating component is a rotor 206 including a shaft 208. The sleeve 204 extends from the floor of the base deck. For example, the sleeve 204 can be coupled to the floor by fastening (e.g., gluing, welding) the sleeve 204 to the floor.

[0029] The rotor 206 is coupled to or includes a hub 210. A magnetic recording medium is coupled to the hub 210 so that when the hub 210 rotates, the magnetic recording medium and the rotor 206 also rotate. The specific shapes and relative positions of the components of the motor assembly may differ from those shown in the figures. For example, the sleeve 204 may have a single inner surface facing the shaft 208 so that the gap between the shaft 208 and the sleeve 204 is uniform along the shaft 208.

[0030] The rotor 206 is rotated by an electromagnetic motor portion of the motor assembly 202. In certain embodiments, the motor assembly 202 includes magnets 212 (e.g., permanent magnets) and stator windings 214. When the stator windings 214 are selectively energized, the magnetic field of the magnets 212 interacts with the magnetic field generated by the energized stator windings 214 to rotate the hub 210. The magnets 212 may be formed as a single annular ring or as multiple individual magnets spaced apart around the hub 210. The magnets 212 are magnetized to form two or more magnetic poles.

[0031] As described above, components coupled to (or part of) the sleeve 204 and rotor 206 form magnetic bearings, as opposed to fluid bearings or ball bearings. In particular, the magnetic bearings are formed by pairs of repelling magnetic poles positioned at various components along the sleeve 204 and rotor 206. These repelling magnetic poles levitate, or float, the rotor 206 such that there is a gap (e.g., an air gap) between the sleeve 204 and rotor 206, and the sleeve 204 and rotor 206 do not physically contact one another. Because the sleeve 204 and rotor 206 do not contact one another, the motor assembly 202 does not necessarily need to apply lubricant between the sleeve 204 and rotor 206 components.

[0032] In the example of the motor assembly 202 shown in FIG. 5, the magnetic bearing of the motor assembly 202 includes a horizontal magnetic bearing component and a vertical magnetic bearing component. The horizontal magnetic bearing component is formed by one or more pairs of magnetic poles 216 having individual magnetic poles spaced apart horizontally and having repelling magnetic poles. In a particular embodiment, the horizontal magnetic bearing component includes an upper pair of magnetic poles and a lower pair of magnetic poles. Each pair of magnetic poles 216 can have two positive or negative magnetic poles that repel each other.

[0033] One of the magnetic poles can be coupled to or form part of the sleeve 204. For example, a magnet can be coupled to the sleeve 204 to form the first magnetic pole. As another example, the sleeve 204 itself can be magnetized to form the first magnetic pole.

[0034] Another magnetic pole may be coupled to or form part of the rotor 206. For example, a magnet may be coupled to the rotor 206 to form a second magnetic pole having the same polarity as the first magnetic pole. As another example, the rotor 206 itself may be magnetized to form the second magnetic pole. In certain embodiments, the shaft 208 of the rotor 206 includes the magnetic pole. As shown in FIG. 5, the shaft 208 is positioned within a central opening of the sleeve 204.

[0035] Because of the repelling magnetic poles, and because the shaft 208 is at least partially surrounded by the sleeve 204, the horizontal magnetic bearing components help maintain a horizontal spacing between the sleeve 204 and the rotor 206. In other words, the repelling magnetic poles help maintain an air gap between the two components so that the sleeve 204 and the rotor 206 do not contact each other. During operation of the motor assembly 202, the rotor 206 can rotate about the sleeve 204 without contacting the rotor 206 and without requiring a lubricant to smooth the rotation.

[0036] The vertical magnetic bearing component is formed by one or more pairs of magnetic poles 218 that are vertically spaced apart from one another and have repelling magnetic poles. For example, the vertical magnetic bearing component may include a lower pair of repelling magnetic poles and an upper pair of repelling magnetic poles.

[0037] The lower pair of magnetic poles 218 may be coupled to or form part of the sleeve 204 and a portion of the rotor 206 that extends below a portion of the sleeve 204. For example, magnets may be coupled to the sleeve 204 and the rotor 206 to form the opposing magnetic poles 218. As another example, all or a portion of the sleeve 204 and the rotor 206 may be magnetized to form the opposing magnetic poles 218.

[0038] The upper pair of magnetic poles 218 may be coupled to or form part of the sleeve 204 and the portion of the rotor 206 that extends above the sleeve 204. For example, magnets may be coupled to the sleeve 204 and the rotor 206 to form the opposing magnetic poles. As another example, all or part of the sleeve 204 and the rotor 206 may be magnetized to form the opposing magnetic poles.

[0039] Because the force generated by the repulsion of the upper pair of magnetic poles is in the opposite direction to the force generated by the repulsion of the lower pair of magnetic poles, the vertical magnetic bearing components help maintain vertical spacing between the sleeve 204 and the rotor 206, and between the rotor 206 and both the base deck and the top cover. In other words, the repulsive magnetic poles help maintain the air gap between these components so that they do not contact one another. For example, the two pairs of magnetic poles cause the rotor 206 to float or levitate. During operation of the motor assembly 202, the rotor 206 can rotate within the sleeve 204 without contacting the sleeve 204, the floor of the base deck, or the top cover, and without the need for lubricants to smooth its rotation.

[0040] The magnetic bearings described above allow the rotating parts of the motor assembly to rotate relative to the fixed parts without contacting each other and without necessarily requiring lubricated bearings. In magnetic bearings, the rotating parts can float or levitate. As described above, the magnetic poles can be generated by separate magnets coupled to the motor assembly parts or by magnetizing the parts themselves. The amount of magnetic field force required to levitate the rotating parts can depend on, among other factors, the mass of the rotating parts and the desired spacing between the parts (typically on the order of millimeters). In certain embodiments, the various magnetic poles are generated by permanent magnets or electromagnets.

[0041] In certain embodiments, the motor assembly is fully assembled before being attached to the base deck. In other embodiments, only a subset of the components of the motor assembly are assembled together before being secured to the base deck. Once secured to the base deck, the remaining components of the motor assembly can be assembled. Once assembled, other components of the hard disk drive can be coupled to the base deck and the motor assembly.

[0042] In certain embodiments, the motor assembly can be used to perform various methods. As an example, the motor assembly can be used to rotate a magnetic recording medium, with the rotating portion of the motor assembly levitating or floating relative to the stationary portion of the motor assembly. Thus, the rotating portion can rotate and levitate simultaneously.

[0043] Although the above-described embodiment incorporates a magnetic bearing in the motor assembly that rotates the magnetic recording medium, the magnetic bearing can be incorporated in other components or assemblies, such as a pivot bearing. As described above, the motor assembly 108 rotates the magnetic recording medium 106 while the actuator assembly 112 is driven by the voice coil motor assembly 118 to orbit around the pivot bearing 120. The pivot bearing traditionally uses ball bearings positioned in a cage and at least partially submerged in lubricant. As with hydrodynamic bearings, the lubricant in the pivot bearing can leak from the pivot bearing and contaminate the hard disk drive. Therefore, in certain embodiments, the pivot bearing 120 can include a magnetic bearing instead of a ball bearing. As with the motor assembly described above, the magnetic bearing in the pivot bearing 120 can include one or more pairs of magnetic poles. The magnetic poles can repel each other, creating an air gap between the stationary and rotating components of the pivot bearing 120.

[0044] Various modifications and additions can be made to the disclosed embodiments without departing from the scope of the present disclosure. For example, while the above-described embodiments refer to particular features, the scope of the present disclosure also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present disclosure is intended to include all alternatives, modifications, and variations as fall within the scope of the claims, and all equivalents thereof.

Claims

1. A hard disk drive, a base deck coupled to the cover; a motor assembly coupled to the base deck, the motor assembly including a stationary component having a sleeve and a rotating component having a shaft; a magnetic recording medium coupled to the motor assembly; the motor assembly includes a magnetic bearing having a horizontal magnetic bearing component and a vertical magnetic bearing component, the vertical magnetic bearing component including an upper repulsive magnetic pole pair and a lower repulsive magnetic pole pair; Hard disk drive.

2. 2. The hard disk drive of claim 1, wherein the horizontal magnetic bearing assembly includes a first pair of repelling magnetic poles.

3. 2. The hard disk drive of claim 1, wherein the shaft is coupled to a hub, and the magnetic recording medium is coupled to the hub.

4. 4. The hard disk drive of claim 3, wherein the shaft includes a first magnetic pole having a first magnetic polarity, and the sleeve includes a second magnetic pole having a second magnetic polarity that repels the first magnetic polarity.

5. The hard disk drive of claim 1 , wherein the stationary component and the rotating component are spaced apart from each other.

6. The hard disk drive of claim 1 , wherein the motor assembly is lubricant-free.

7. 2. The hard disk drive of claim 1, wherein a first portion of the shaft forms one part of the upper repelling pole pair and a first portion of the sleeve forms another part of the upper repelling pole pair.

8. 8. The hard disk drive of claim 7, wherein the second portion of the shaft forms one part of the lower repelling pole pair and the second portion of the sleeve forms another part of the lower repelling pole pair.

9. 9. The hard disk drive of claim 8, wherein a third portion of the shaft forms one part of the horizontal magnetic bearing assembly and a third portion of the sleeve forms another part of the horizontal magnetic bearing assembly.

10. 2. The hard disk drive of claim 1, wherein the shaft includes a first magnetic pole having a first magnetic polarity, the sleeve includes a second magnetic pole having a second magnetic polarity identical to the first magnetic polarity, and the first magnetic pole and the second magnetic pole form the horizontal magnetic bearing component.

11. The hard disk drive of claim 1 , wherein the motor assembly further comprises a stator coil.

12. The hard disk drive of claim 1 , wherein the sleeve is coupled to the base deck.

13. The hard disk drive of claim 1 , wherein the motor assembly does not include a fluid dynamic bearing.

14. 2. The hard disk drive of claim 1, wherein the pair of upper repelling magnetic poles is formed by separate magnets coupled to the shaft and the sleeve, respectively.

15. 2. The hard disk drive of claim 1, wherein the pair of upper repelling magnetic poles is formed by magnetized portions of the shaft and the sleeve.

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