Disk drive having a disk clamp with openings directly radially outboard of fasteners

A disk drive includes a spindle motor attached to a disk drive base. The spindle motor includes a hub that rotates about a spindle rotation axis. An annular disk is mounted on the hub. A clamp contacts a top surface of the hub. The clamp includes first and second pluralities of openings therethrough. The clamp is attached to the hub by a plurality of fasteners, each of the plurality of fasteners passing through one of the first plurality of openings. Each of the second plurality of openings has a closed outer periphery within the clamp. Each of the first plurality of openings is disposed directly between the spindle rotation axis and a corresponding one of the second plurality of openings.

BACKGROUND

The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board (PCB) attached to a disk drive base of the HDA. The head disk assembly includes at least one disk (such as a magnetic disk, magneto-optical disk, or optical disk), which is clamped to a rotating hub of a spindle motor. A head stack assembly (HSA) is actuated to position heads adjacent the major surfaces of the disk(s), to read and write information stored thereon. The printed circuit board assembly includes electronics and firmware for controlling the rotation of the spindle motor, for controlling the actuation and position of the HSA, and for providing a data transfer channel between the disk drive and its host.

The head stack assembly typically includes an actuator, at least one head gimbal assembly (HGA), and a flex cable assembly. Each HGA includes a head for reading and writing data from and to an adjacent disk surface. In magnetic recording applications, the head typically includes an air bearing slider and a magnetic transducer that comprises a writer and a read element. The magnetic transducer's writer may be of a longitudinal or perpendicular design, and the read element of the magnetic transducer may be inductive or magnetoresistive. In optical and magneto-optical recording applications, the head may include a minor and an objective lens for focusing laser light on an adjacent disk surface.

The spindle motor typically includes the rotating hub (on which annular disks are mounted and clamped), a magnet attached to the hub, and a stator. Various coils of the stator are selectively energized to form an electromagnetic field that pulls/pushes on the magnet, thereby rotating the hub. Rotation of the spindle motor hub results in rotation of the mounted disks.

Many contemporary disk clamps are attached to the spindle motor hub by screws that are arranged in a circle around the spindle motor shaft (e.g. a non-rotating shaft). When the screws are tightened, they cause the clamping pressure to be non-uniform, such that the regions near each screw exert higher clamping pressure and the areas between the screws exert lower clamping pressure. Such non-uniform clamping pressure may produce an undesirably large sinusoidal warping of the clamped disk(s). The resulting curvature of the disk surface is known as “disk crown”.

Disk crown due to non-uniform clamping can modulate and affect the microscopic spacing between the disk surface and the adjacent read/write head. Such microscopic spacing affects the performance of the head in reading and writing, and so excessive disk crown can adversely affect the performance and signal to noise ratio (SNR) associated with disk drive operations. Therefore, there is a need in the art for a disk drive design having a disk clamp that exerts a more uniform clamping pressure on the disk(s).

The screws that attach a contemporary disk clamp to the spindle motor hub typically do not force the disk clamp to lie flat against a top surface of the spindle motor hub in the region around each screw. There is a good reason why; in many designs some finite vertical or tilt clearance between the clamp and the top surface of the spindle motor hub may be required so that the torque on the screws can vary the clamping pressure applied to the annular disk. However, it may be desirable to decrease the sensitivity of clamping pressure on screw torque, for example to decrease manufacturing variation in clamping pressure. Therefore, there is a need in the art for a disk drive design having a disk clamp that can reduce the sensitivity of clamping pressure on screw torque.

Also, some particulate and other contamination may escape from the screws and screw holes in the spindle motor hub, via the previously described finite vertical or tilt clearance between the clamp and the top surface of the spindle motor hub. Such contaminants, if excessive, may cause head crash or otherwise decrease the reliability of the disk drive if they spread within the head disk assembly (e.g. by being spun off by the centrifugal force associated with spindle hub rotation). Therefore, there is a need in the art for a disk drive design having a disk clamp that can better contain contamination that may escape from the screws and screw holes in the spindle motor hub.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1is an exploded perspective view of a disk drive100according to an embodiment of the present invention. The disk drive100includes a head disk assembly (HDA)104and a printed circuit board assembly (PCBA)102. The PCBA102includes conventional circuitry for processing signals and controlling the operations of the disk drive100. The HDA104includes a base108and a cover110attached to the base108to collectively house at least one annular disk150, a head stack assembly (HSA)120rotatably attached to the base108, and a spindle motor130attached to the base108. The spindle motor130rotates a hub132about a spindle rotation axis134, for the hub132may be cylindrical and rotated at a constant angular velocity. The annular disk150is mounted on, is clamped to, and rotates with, the hub132. In certain embodiments, the disk drive100ofFIG. 1may include a plurality of annular disks150that are mounted on the hub132of the spindle130. For example, annular disk150may be a top disk under which one or more additional disks may be mounted on the hub132of the spindle130. The disk(s)150may comprise an aluminum, glass, or ceramic substrate, for example with the substrate being coated with a NiP under-layer, a thin-film magnetic layer, a diamond-like amorphous carbon protective layer, and a very thin lubricant layer.

In the embodiment ofFIG. 1, the HSA120comprises a swing-type or rotary actuator122. At least one actuator arm124may be cantilevered from the actuator122. The rotary actuator122may be fabricated of a metal material such as aluminum, stainless steel, magnesium, beryllium, or an alloy thereof, by casting and/or forging. The HSA120also includes at least one head gimbal assembly (HGA)126, a flex cable127, and a flex cable bracket128fixed to the base108. The HGA126supports a head (not visible in this view) adjacent to the annular disk150, for writing and reading data to and from the annular disk150.

In magnetic recording hard disk drive applications, the head may include a magneto resistive sensor for reading data from disk150, and a longitudinal or perpendicular type inductive transducer for writing data to disk150. In optical or magneto-optical recording applications, the head may include an objective lens for focusing laser light upon the recording media surface. The storage capacity of the disk drive100may be increased by the use of additional annular disks150and by the HSA120having correspondingly more HGAs126supported by multiple actuator arms124.

In the embodiment ofFIG. 1, a voice coil motor (VCM) may include top and bottom VCM plates182,184mounted to the base108. One or both of the VCM plates may include a permanent magnet (e.g. permanent magnet180). The VCM plates182,184form a yoke to carry magnetic flux from the permanent magnet(s). The coil123of the actuator122may be disposed between the top and bottom VCM plates182and184to cause rotation of the HSA120about a pivot axis121, in response to an electrical current passed through the coil123.

In this way, the VCM controllably positions the head(s) of the HSA120relative to the annular disk150for writing and/or reading data. The angular range of HSA pivoting may be limited by one or more stops, and the HSA may be held adjacent a stop by a latch (e.g. actuator latch168). In certain embodiments, the cover110may include an opening for a breather filter116and a covering118for a larger opening for use in servo writing the annular disk150. The base108may be attached to the cover110by means of screws or another conventional fastening method.

FIG. 2is a top perspective view of a disk clamp152according to an embodiment of the present invention. The clamp152includes a first plurality of openings210,212,214,216, therethrough. The clamp152also includes a second plurality of openings220,222,224,226, therethrough. Each of the second plurality of openings220,222,224,226has a closed outer periphery within the clamp152. The clamp152may comprise a metal such as steel, aluminum, and/or alloys thereof. For example, steel may be stainless steel, spring steel, etc.

In the embodiment ofFIG. 2, each of the first plurality of openings210,212,214,216is disposed directly between the center240of the clamp152, and a corresponding one of the second plurality of openings220,222,224,226. In this context, “directly between” means radially between and circumferentially aligned. That is, any radius extending from center240of the clamp152and intersecting one of the first plurality of openings210,212,214,216, will also intersect the corresponding one of the second plurality of openings220,222,224,226. This is not necessarily true vice versa; for example, in the embodiment ofFIG. 2, each of the first plurality of openings210,212,214,216is smaller than corresponding ones of the second plurality of openings220,222,224,226. Note that in the embodiment ofFIG. 2, the center240of the clamp152lies in an optional central hole242. In certain embodiments, such an arrangement of the second plurality of openings220,222,224,226with respect to the first plurality of openings210,212,214,216may substantially improve the uniformity of clamping pressure applied by the clamp152to the clamped annular disk (e.g. annular disk150ofFIG. 1).

In the embodiment ofFIG. 2, each of the second plurality of openings220,222,224,226is large enough to include (enclose within its contour) an arc that spans at least 50° about the corresponding one of the first plurality of openings210,212,214,216. Preferably but not necessarily, each of the second plurality of openings220,222,224,226is large enough to include (enclose within its contour) an arc that spans 70° to 120° about the corresponding one of the first plurality of openings210,212,214,216. In certain embodiments, such arcuate dimensional ranges may further improve the uniformity of clamping pressure applied by the clamp152to the clamped annular disk (e.g. annular disk150ofFIG. 1).

In the embodiment ofFIG. 2, the clamp152includes a clamp outer periphery260and a clamp inner region270. Each of the first plurality of openings210,212,214,216is disposed in the clamp inner region270. The clamp outer periphery260is connected to the clamp inner region270by a plurality of spokes that are disposed between two of the second plurality of openings220,222,224,226. For example, spoke280is disposed between openings220and226, and spoke282is disposed between openings220and222. In the embodiment ofFIG. 2, the clamp outer periphery260, the clamp inner region270, and the plurality of spokes (e.g. spokes280and282), are all a single component having material continuity rather than being an assembly of sub-components.

The exploded view ofFIG. 1depicts how the clamp152ofFIG. 2may be assembled with other components of a disk drive (e.g. disk drive100). Now referring to bothFIG. 1andFIG. 2, the clamp152contacts a top surface of the hub132, and the clamp152is attached to the hub132by a plurality of fasteners136. Each of the plurality of fasteners136passes through one of the first plurality of openings210,212,214,216. For example, each of the plurality of fasteners136may be a screw that extends into a corresponding threaded hole in the hub132.

Now referring toFIGS. 1 and 2, each of the first plurality of openings210,212,214,216is disposed directly between the spindle rotation axis134and a corresponding one of the second plurality of openings220,222,224,226. In this context, “directly between” means radially between and circumferentially aligned. That is, any radius extending normally from the spindle rotation axis134and intersecting one of the first plurality of openings210,212,214,216, will also intersect the corresponding one of the second plurality of openings220,222,224,226. Still referring toFIGS. 1 and 2, each of the second plurality of openings220,222,224,226is disposed directly outboard from a corresponding one of the plurality of fasteners136, along a radius extending from the spindle rotation axis134.

Now referring again toFIG. 1, the hub132is shown to also optionally include a plurality of balance weight receptacles (e.g. note that the top surface of the hub has eight peripheral holes, rather than merely the four holes that are aligned to receive the fasteners136). In the embodiment ofFIG. 2, the clamp152optionally includes a third plurality of openings230,232,234,236, each of which being preferably aligned with a corresponding one of the plurality of balance weight receptacles in the hub132. Such alignment may allow a balance weight to be inserted in a chosen balance weight receptacle via one of the third plurality of openings, after the clamp152has been fastened to the hub132.

In certain alternative embodiments of the present invention, each of the second plurality of openings220,222,224,226may be aligned with a corresponding one of the plurality of balance weight receptacles in the hub132. Such alignment may allow a balance weight to be inserted in a chosen balance weight receptacle of the hub132via one of the second plurality of openings220,222,224,226, after the clamp is fastened to the hub132, even where the clamp lacks a third plurality of openings.

FIG. 3is a radial cross-sectional view of a portion of a spindle motor hub132, conventional disk clamp300, fastener136, annular disks150,350, and spacer rings354,356, according to the prior art. The fastener136is a screw that passes through a first opening310in the conventional disk clamp300, and extends into a threaded hole382of the hub132. An inner region370of the conventional clamp300receives a downward force from the fastener136, which, in turn, provides a clamping pressure between the outer periphery360of the conventional clamp300and the top disk150. However, the downward force from the fastener136is not always sufficient to cause contact between the inner region370of the conventional clamp300and a top surface380of the hub132. For example, a vertical or tilt clearance390exists between the inner region370of the conventional disk clamp300and the top surface380of the hub132. The threaded hole382, and the interaction between the fastener136and the threaded hole382, may be a source of contamination (e.g. particulate contamination). The vertical or tilt clearance390may facilitate such contaminants to spread within the disk drive, which may cause head crash or otherwise decrease the reliability of the disk drive.

FIG. 4is a radial cross-sectional view of a portion of a spindle motor hub132, novel disk clamp400, fastener136, annular disks150,350, and spacer rings354,356, according to an embodiment of the present invention. In the embodiment ofFIG. 4, the fastener136is a screw that passes through a first opening410in the novel disk clamp400, and extends into a threaded hole382of the hub132. In the embodiment ofFIG. 4, a top surface380of the hub132defines a surface normal that is parallel to the spindle rotation axis (e.g. spindle rotation axis134ofFIG. 1), and that is parallel to a screw longitudinal axis of the threaded hole382in the hub132.

In the embodiment ofFIG. 4, the clamp400is in contact with the hub132contiguously around the first opening410, so that the first opening410is contiguously encircled by such contact. For example, the clamp inner region470is in contact with the top surface380of the hub132. The clamp outer periphery460contacts and applies a clamping pressure to the annular disk150, but the clamp outer periphery460is not in contact with the top surface of the hub132. Note that in the embodiment ofFIG. 4, a first thickness of the clamp400, that is measured parallel to the spindle rotation axis at the clamp outer periphery460, is preferably but not necessarily greater than a second thickness of the clamp400that is measured parallel to the spindle rotation axis in the clamp inner region470. In certain embodiments, such an inequality may improve the uniformity of clamping pressure applied by the outer periphery460to the annular disk150.

In the embodiment ofFIG. 4, the first opening410is disposed directly between the center of the clamp400(to the left ofFIG. 4as drawn), and a second opening420through the clamp400. That is, the second opening420is disposed directly outboard from the fastener136inFIG. 4. This arrangement may improve the circumferential uniformity of clamping pressure applied by the clamp400to the clamped annular disk (e.g. annular disk150).

In the foregoing specification, the invention is described with reference to specific exemplary embodiments, but those skilled in the art will recognize that the invention is not limited to those. It is contemplated that various features and aspects of the invention may be used individually or jointly and possibly in a different environment or application. The specification and drawings are, accordingly, to be regarded as illustrative and exemplary rather than restrictive. For example, the word “preferably,” and the phrase “preferably but not necessarily,” are used synonymously herein to consistently include the meaning of “not necessarily” or optionally. “Comprising,” “including,” and “having,” are intended to be open-ended terms.