WO2000065588A1

WO2000065588A1 - Improved motor and spindle design

Info

Publication number: WO2000065588A1
Application number: PCT/US2000/010845
Authority: WO
Inventors: Ben Huang
Original assignee: Castlewood Systems, Inc.
Priority date: 1999-04-22
Filing date: 2000-04-21
Publication date: 2000-11-02

Abstract

A disk drive system for clamping the hub (78) of the disk (66). The system improves the performance and maintains the small form factor of the spindle motor (34) and disk drive (26) by moving the clamping magnet (138) radially outward of the cavity (131) such that the stator windings (132) and bearings (127, 128) are enlarged. Accordingly, the stator windings (132) can be enlarged so as to increase the resistance of the stator. Furthermore, the added room in the cavity (131) allows a larger spacing between the bearings (127, 128) so as to provide increased stability to the spindle shaft (124) and a reduced motor rocking frequency to the spindle and removable disk.

Description

IMPROVED MOTOR AND SPINDLE DESIGN

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims benefit of U.S. Patent Application Serial No. 60/130,834, entitled "Improved Motor and Spindle Design," filed April 22, 1999, under 37 C.F.R. §1.78, the full disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION The present invention generally relates to data recording disk drives and more specifically to spindle drives for removable hard disk cartridges. With the increasing use of mobile computers, there is a greater desire for thin, yet powerful removable disk drives. However, such slim-line disk drives have posed problems which have not been adequately solved by the conventional disk drives.

The disk drive height for removable cartridge drives depends, in part, on the overall spindle motor height, which is primarily dictated by bearing thickness, bearing spacing, and the height of the spindle shaft that engages and locates the disk on the rotor. In order to effectively clamp onto a removable disk cartridge, conventional spindle motors typically use a clamping mechanism, such as a clamping magnet to hold the disk onto the spindle drive. Such clamping magnets however, typically occupies the same space that is used for the stator windings and the top bearings. Consequently, the size of the stator windings must be decreased, which decreases the efficiency, resistance, and torque produced by the spindle motor. In addition to the reduced efficiency of the stator windings, the top bearing must also be moved lower to accommodate the clamping magnet. Moving the top bearing down decreases the height of the spindle, but also detrimentally decreases the stability of the spindle shaft and increases the rocking frequency of the rotating disk.

Accordingly, what is needed is a disk drive that has a spindle motor which provides sufficient torque and stability while maintaining a low height form factor.

SUMMARY OF THE INVENTION The present invention provides systems, devices, and methods for providing improved stability and motor resistance while maintaining a small form factor. The systems of the present invention maintain the small form factor of the spindle motor and disk drive by moving the clamping magnet adjacent an outer periphery of the rotor. By moving the clamping magnet, the inner cavity for housing the stator windings and bearings is increased. Accordingly, the stator windings can be enlarged so as to increase the resistance of the stator windings. Furthermore, the added room in the cavity allows a larger spacing between the upper and lower bearings so as to provide increased stability to the spindle shaft and a reduced motor rocking frequency to the spindle and removable disk.

In one aspect, the present invention provides a spindle motor for use with a removable media. The spindle motor includes a spindle shaft and bearings which rotatably support the spindle shaft. A rotor is coupled to the spindle shaft. A clamping magnet is disposed on an outer surface of the rotor to hold the removable media. The radial position of an outside edge of the clamping magnet (in relation to the spindle shaft) is greater than a radial position of the rotation assembly. In a specific configuration, the rotor defines an interior cavity for housing a rotation assembly that rotates the rotor.

In another aspect, the present invention provides a system for use with a removable cartridge. The system includes a spindle shaft and a rotor coupled to the spindle shaft. A clamping magnet is positioned along an outer surface of the rotor such that an outside diameter of the clamping magnet is substantially equal to the diameter of the rotor.

In yet another aspect, the present invention provides a method of rotating a recording medium. The method comprises placing a hub of the recording medium onto a spindle shaft. A rotor is engaged against the hub of the recording medium and the hub is clamped to the rotor with a clamping magnet. The rotor and the clamped hub are rotated with a rotation assembly. A radial position of an outside edge of the clamping magnet is greater than a radial position of the rotation assembly. Other aspects, features, and advantages of the present invention will become apparent upon consideration of the following detailed description and the accompanying drawings, in which like reference designations represent like features throughout the figures.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic illustration of a video system including a high definition television and an external disk drive. Fig. 1A is a perspective view of an external disk drive for use with a removable rigid recording disk cartridge, according to the principles of the present invention.

Fig. IB is a perspective view of an internal disk drive similar to the external drive of Fig. 1A, in which the internal drive is adapted for insertion into a standard bay of a computer.

Fig. 2 is a perspective view of the internal disk drive of Fig. IB, in which a cover of the disk drive has been removed to show a receptacle for the removable cartridge and some of the major drive components. Fig. 3 is a perspective view of a removable cartridge housing a rigid magnetic recording disk.

Fig. 3 A is a top view of the cartridge of Fig. 3, showing an upper cartridge housing.

Fig. 3B is a bottom view of the cartridge of Fig. 3, showing a lower cartridge housing.

Fig. 3C is a top view illustrating the cartridge of Fig. 3 being inserted into the receptacle of the internal drive of Fig. 2, and also shows how a door actuation shaft of the receptacle engages a door opening link to open the door of the cartridge.

Fig. 4 is a perspective view of an arm supporting a pair of read/write heads, the arm being pivotally positioned by a voice coil motor.

Fig. 5 is a simplified perspective view of the internal drive of Fig. 2, in which the voice coil motor and arm have been removed to show the cartridge release linkage and the head retract linkage.

Fig. 5 A is a top view of the internal drive of Fig. 2, and illustrates the position of the cartridge release linkage and head retract linkage when the cartridge is removed from the receptacle.

Fig. 5B is a top view of the internal drive of Fig. 2, and illustrates the position of the cartridge release linkage and head retract linkage when a cartridge is inserted in the receptacle and the voice coil motor positions the heads along the recording surface.

Fig. 5C is a top view of the internal drive of Fig. 2, and illustrates the position of the cartridge release linkage and head retract linkage when a cartridge is to be removed from the receptacle and the voice coil motor has moved the heads to an intermediate position along a head load ramp to allow the disk to safely spin down. Fig. 5D is a top view of the internal drive of Fig. 2, showing the voice coil motor releasing the cartridge from the receptacle by moving the heads to a release position, so that the arm articulates the cartridge release linkage and a biasing system expels the cartridge. Fig. 5E is a detailed top view showing how a tab of the head retract linkage limits the travel of the arm so that the data transfer head is not damaged by contact with the hub of the disk.

Fig. 6A is a cross-sectional side view of the internal drive of Fig. 2 with the cartridge partially inserted, showing the engaging surfaces of the cartridge and the receptacle which ensure that the cartridge aligns with the spindle motor, and also showing the cover springs which bias the forward end of the cartridge downward, and the base springs which bias the rear end of the cartridge upward.

Fig. 6B is a cross-sectional view similar to Fig. 6A, in which the cartridge is latched in the receptacle. Fig. 7A and 7B are functional block diagrams which schematically illustrate the signal processing and power circuitry of the internal drive;

Fig. 8 illustrates a spindle motor having a clamping magnet disposed on a rotor;

Fig. 9 illustrates a spindle motor and clamping magnet in accordance with the present invention; and

Fig. 10 illustrates an alternative embodiment of the spindle motor and clamping magnet.

DESCRIPTION OF THE SPECIFIC EMBODIMENT The cartridges used with these disk drives will preferably contain a single, two-sided rigid magnetic recording disk which is capable of storing at least about 2.2 gigabytes of data, preferably being capable of storing at least about 5.0 gigabytes of data, and most preferably being capable of storing 13.0 gigabytes of data or more. The devices and methods of the present invention may find applications for storing a wide variety of data for use with notebook computers, desktop computers, TiVo systems, digital VCRs, computer kiosks, more powerful computer workstations, and the like. The cartridges, disk drive systems, and methods of the present invention are particularly well suited for use in recording, archiving, playing back digital video data, and for fabricating video storage systems. Due to the low cost, large capacity, and archivability provided by the recording system of the present invention, a standard length movie in a format suitable for high definition television ("HDTV") may be stored using no more than two cartridges, and ideally may be stored on a single cartridge having a single, two sided hard disk. While the present invention is shown and described with a hard disk cartridge and a fixed spindle drive, the present invention is also applicable for use with moveable spindle drives, optical disk drives, DVD disks, DVD players, audio compact disks, compact disk players, Digital VCRs, TiVo systems, and the like.

As schematically illustrated in Fig. 1, a video system 2 includes a high definition television ("HDTV") 4 which is coupled to an external disk drive 10. External drive 10 will read recorded digital data from a removable disk cartridge, and will transmit the data to HDTV 4. No general purpose computer need be coupled between external drive 10 and HDTV 4, although such a general purpose computer may be incorporated into video system 2 to allow flexible manipulation of the video data. In the exemplary embodiment, external drive 10 is less than 2 in. by less than 5V in. by less than 7 in. The small size of the drive (and the small size of the disks on which the movies are stored) helps decrease the overall space which is required for both the video system and the associated movie library.

Referring now to Figs. 1 A and IB, external disk drive 10 and internal disk drive 20 will share many of the same components. However, external drive 10 will include an enclosure 12 adapted for use outside a personal computer, high definition television, or some other data manipulation or display device. Additionally, external drive 10 will include standard I/O connectors, parallel ports, and/or power plugs similar to those of known computer peripheral or video devices.

Internal drive 20 will typically be adapted for insertion into a standard bay of a computer. In some embodiments, internal drive 10 may instead be used within a bay in a HDTV, thereby providing an integrated video system. Internal drive 20 may optionally be adapted for use with a bay having a form factor of 2.4 inches, 1.8 inches, 1 inch, or with any other generally recognized or proprietary bay. Regardless, internal drive 20 will typically have a housing 22 which includes a housing cover 24 and a base plate 26.

As illustrated in Fig. IB, housing 24 will typically include integral springs 28 to bias the cartridge downward within the receiver of housing 22. It should be understood that while external drive 10 may be very different in appearance than internal drive 20, the external drive will preferably make use of base plate 26 and most or all mechanical, electromechanical, and electronic components of internal drive 20. Cover 24 may be modified for use with external drive 10 so that a label on the cartridge is at least partially visible through a window along the upper surface of enclosure 12 when the cartridge is in the drive. Many of the components of internal drive 20 are visible when cover 22 has been removed, as illustrated in Fig. 2. In this exemplary embodiment, a voice coil motor 30 positions first and second heads 32 along opposed recording surfaces of the hard disk while the disk is spun by spindle drive motor 34. As will be described more fully below, the spindle drive motor will typically comprise a brushless DC motor, and the spindle drive structure will preferably rotate at a fixed position. A release linkage 36 is mechanically coupled to voice coil motor 30, so that the voice coil motor effects release of the cartridge from housing 22 when heads 32 move to a release position on a head load ramp 38. Head load ramp 38 is preferably adjustable in height above base plate 26. While the head load ramp is shown mounted to the base, in other embodiments, the head load ramp can be mounted to a side wall of the disk drive. A more complete description of the head load ramp can be found in co-pending U.S. Patent Application No. 09/454,182, filed December 22, 1999, the complete disclosure of which is incorporated by reference.

A head retract linkage 40 helps to ensure that heads 32 are retracted from the disk and onto head load ramp 38 when the cartridge is removed from housing 22. Head retract linkage 40 may also be used as an inner crash stop to mechanically limit travel of heads 32 toward the hub of the disk.

Base 26 preferably comprises a steel sheet metal structure in which the shape of the base is substantially fully defined by stamping. Bosses 42 are stamped into base 26 to engage and accurately position lower surfaces of the cartridge housing. To help ensure accurate centering of the cartridge onto spindle drive 34, rails 44 maintain the cartridge above the associated spindle until the cartridge is inserted to the appropriate depth, whereupon the cartridge descends under the influence of cover springs 28 and the force imparted by the user. This brings the hub of the disk down into engagement with spindle drive 34. A latch 46 of release linkage 36 engages a detent of the cartridge to restrain the cartridge within housing 22.

A cartridge for use with internal drive 20 is illustrated in Fig. 3. Generally, cartridge 60 includes a front edge 62 and rear edge 64. A disk 66 (see Fig. 3A) is disposed within cartridge 62, and access to the disk is provided through a door 68. Optionally, a ridge may extend from rear edge of the cartridge to facilitate insertion and/or removal of the cartridge, and to avoid any interference between the housing surrounding the receptacle and the user's fingers. The door of the drive may include a corresponding bulge to accommodate such a ridge. An anti-rattle mechanism, ideally having a two-part arm (one portion comprising polymer molded integrally with the door, the other portion comprising a metal and extending from the polymer portion over the hub of the disk) prevents the disk from rattling within the cartridge when the cartridge is removed from the drive.

As can be understood most clearly with reference to Figures 3A and B, a housing 70 of cartridge 60 is generally formed from an upper housing portion 72 and a lower housing portion 74. An opening 76 in lower housing portion 74 provides access to a disk hub 78 for rotating engagement between the disk and spindle drive 34. Detent 80 of cartridge 60 is also illustrated in each of Figs. 3-3B. This detent is engaged by latch 46 of internal drive 20 to restrain cartridge 60 in the receptacle of the disk drive. As can generally be understood with reference to Fig. 3C, door 68 is automatically opened when cartridge 60 is inserted into internal drive 20. Door 68 is opened by engagement between shaft 48 of the drive and a link 82 of the cartridge. Link 82 rotates a door assembly 84 about a cartridge pivot 86. In the exemplary embodiment, a ramp 88 on the inner surface of cartridge housing 70 deflects an arm of the door assembly to resiliently bias the disk against the cartridge housing and prevent rattling of (and the associated damage to) the disk when the cartridge is removed from internal drive 20.

As can be understood with reference to Figs. 2 and 4, heads 32 are supported by an arm 90 which is pivotally mounted to base plate 26. Arm 90 is rotationally positioned by voice coil motor 30, and the arm generally defines a proximal end 92 and a distal end 94. Heads 32 are mounted to resilient arm extensions 96 at the distal end of arm 90. Heads 32 are oriented towards each other for reading opposed recording surfaces of the disk, and lifting wires 98 angle distally and laterally from arm extensions 96. This allows the wires to ride on head load ramp 38 while heads 32 are disposed adjacent the recording surface, and facilitates smoothly transferring the heads between the head load ramp and the recording surface. Alternatively, the lifting wires may extend laterally to a bend, and then distally from the bend, rather than being angled.

Heads 32 will often be separated from the spinning recording surface of disk 66 by a thin layer of air. More specifically, the data transfer head often glides over the recording surface on an "air bearing," a thin layer of air which moves with the rotating disk. Although recording densities are generally enhanced by minimizing the thickness of this air bearing, often referred to as the glide height, excessive contact between the head and the disk surface can decrease the reliability of the recording system. To avoid a head crash (in which the data transfer head contacts and damages the disk), the voice coil motor will generally position heads 32 on head load ramp 38 whenever the disk is rotating at insufficient velocity to maintain a safe glide height.

As can be understood with reference to Figs. 5 and 5 A, tab 100 of arm 90 is disposed between release linkage 36 and head retract linkage 40. The structure and operation of these linkages will be described with reference to Figs. 5A-5D.

When no cartridge is disposed in internal drive 20, and when no power is supplied to voice coil motor 30, biasing springs 102a, 102b urge arm 90 to an intermediate or parked position 104, as illustrated in Fig. 5 A. As cartridge 60 is inserted into the receptacle of internal drive 20, the cartridge rotates a head retract pivot 106. Head retract pivot 106, in turn, moves a slider 108 rearward, away from tab 100 of arm 90, so that the voice coil motor is free to pivot the arm from parked position 104 to selectively read data tracks from the recording surface of the disk, as illustrated in Fig. 5B. Cartridge 60 is held in the receiver of internal drive 20 by engagement of latch 46 with detent 80, as is also illustrated in Fig. 5B. Figs. 5C and 5D illustrate the use of voice coil motor 30 to effect release of cartridge 60 from the receiver of internal drive 20. Prior to release of the cartridge 60 from the receiver of internal drive 20, voice coil motor 30 pivots arm 90 to move the heads from disk 66 to head load ramp 38. As described above, wires 98 engage the ramp while the heads are still disposed along the recording surface of the disk. This arrangement provides a smooth transfer of the heads between their gliding position over the recording surface and their parked position along the head load ramp. Wires 98 will generally support heads 32 with the heads separated from the adjacent surface of head load ramp 38 to minimize wear and avoid contamination of the head surface.

Conveniently, a tab 110 of head retract slider 108 prevents arm 90 from moving too far radially inward. Specifically, tab 110 engages tab 100 of arm 90 before the head moves dangerously close to the center of the spinning disk. Biasing spring 102 may help to resiliently rebound arm 90 away from the disk hub to a safe position, or a resilient material may be provided on tab 110 of slider 108, or on tab 100 of arm 90. Regardless, the use of the head retract linkage system as an inner crash stop can avoid the additional cost and complexity of providing a dedicated fixed inner crash stop structure.

Referring now to Fig. 5E, when cartridge 60 is positioned in the receptacle of internal drive 20, tab 110 of head retract linkage 40 is positioned so as to act as an inner crash stop. In other words, tab 100 of arm 90 will engage tab 1 10 of head retract linkage 40 to prevent heads 32 from moving radially inward beyond the recording surface of disk 66. This prevents damage to the heads from contact with hub 78 of disk 66, and also keeps the heads over a surface which is moving with sufficient linear velocity to maintain a safe glide height. Advantageously, where tab 100 of arm 90 impacts tab 110 of the head retract linkage with a significant amount of inertia, as might occur from a transient signal error to the voice coil motor, biasing spring 102 of the head retract linkage may help resiliently rebound the heads back to a safe position away from hub 78.

Once the heads are safely parked along the head load ramp 38 at park position 104, disk 66 may be safely spun down without fear of the heads crashing into the recording surface. Spindle drive 32 may slow the rotation of disk 66 using a brake mechanism to minimize delay. In some embodiments, the kinetic energy from rotating disk 66 and spindle drive 32 may be converted to electrical energy by using the spindle drive motor as a generator. This electrical energy can be stored in a capacitor or the like, and may be used to drive voice coil motor 30 after a shut down, particularly after an emergency shut down when normal power for the voice coil motor is otherwise not available. Hence, the electrical energy generated from the residual kinetic energy of the drive system, which is sometime referred to as "back-EMF," is particularly advantageous for preventing heads 32 from crashing into the recording surface when spindle motor 32 loses power without warning, as the back-EMF can be used to move the heads to the head load ramp.

Regardless of whether voice coil motor 30 actuates arm 90 from a standard power supply or using back-EMF, disk 66 will generally be slowed to a safe cartridge handling speed while heads 32 are disposed at park position 104. In most embodiments, disk 66 will come to a complete stop while cartridge 60 is disposed within internal drive 20. Generally, this will take between about 0.5 and 10.0 seconds, disk 66 preferably slowing from its normal operating speed in about 5.0 seconds.

Once disk 66 has slowed and/or stopped, voice coil motor 30 pivots arm 90 so that tab 100 of the arm engages and moves a release slider 112 of release linkage 36, as illustrated in Fig. 5D. Biasing spring 102b prevents inadvertent actuation of release linkage 36, and the voice coil motor 30 overcomes the biasing spring to move head 32 from park position 104 to a release position 1 14. As tab 100 slides release slider 112, the release slider rotates a release pivot 1 16. Rotation of release pivot 116, in turn, slides latch 46 rearward, disengaging the latch from detent 80 of cartridge 60. Therefore, voice coil motor 30 (which is generally adapted for accurate positioning of heads 32 along the recording surface of disk 66) is also used to effect movement of release linkage 36 so as to release the cartridge from the receiver of internal drive 20.

After cartridge 60 is unlatched from the receiver of internal drive 20, the cartridge will normally be expelled from the receiver by a biasing system. The use of the biasing system can be understood with reference to Figs. 5D, 6A, and 6B. During insertion, cover springs 28 urge forward edge 62 of cartridge 60 downward, while rear edge 64 remains elevated so long as the cartridge rides along rails 44. As the user slides cartridge 60 manually into the receiver, head retract link 40 places the attached biasing spring 102 under tension. Once disk 66 is substantially aligned with spindle drive 34, the cartridge housing is clear of rails 44. More specifically, rear side indentations 118 (see Fig. 3) allow rear edge 64 of the cartridge to drop downward.

The downward movement of rear edge 64 is opposed by base springs 120. These base springs generally comprise simple wire structures screwed or otherwise fastened to base 26, and the upward urging force imposed on cartridge 60 by the base springs is again manually overcome during insertion. As base springs 120 are compressed against base 26, latch 46 slides into detent 80, so that the latch restrains cartridge 60 within the receiver of internal drive 20. Simultaneously, spindle drive 34 aligns with and engages the hub of disk 66. Spindle drive 34 includes a protruding, tapering nose and a magnetic chuck, while a corresponding countersunk armature is provided at the hub of disk 66. This arrangement promotes centering and alignment of disk 66 on spindle drive 34, and helps ensure a secure driving engagement between these two structures. As described above, the door of the cartridge opens automatically during insertion of the cartridge, while actuation of head retract linkage 40 during insertion also frees arm 90 to move heads 32 from head load ramp 38, and to position recording surfaces 122 along the opposed major surfaces of disk 66.

Base springs 120 and the head retract linkage used to expel the disk from the receptacle of internal drive 20. Once voice coil motor 30 actuates release linkage 36 so as to disengage latch 46 from detent 80, engagement between rails 44 and rear indents 118 generally prevents the cartridge from sliding out of the housing along the plane of the disk. Instead, base springs 120 first urge rear edge 64 of cartridge 60 upward, safely disengaging spindle drive 34 from the hub of the disk. Once these driving structures are disengaged, biasing spring 102b of head retract linkage 40 urges cartridge 60 out of the receiver, and also ensures that arm 90 is safely positioned with heads 32 along head load ramp 38. Generally, the biasing system will slide the cartridge rearward until a portion of the cartridge extends from the drive, so that the cartridge can be easily removed and replaced manually by the user.

Figs. 7A and 7B are functional block diagrams which schematically illustrate the data transfer and power distribution scheme of the drive, respectively. Fig. 7A schematically illustrates the major control and data transfer structures and connections of the drive. The component interaction which allows the use of back-EMF for actuation of the voice coil motor can generally be understood with reference to Fig. 7B. The structure and operation of the voice coil motor operated release linkage is more fully described in co-pending U.S. Patent Application Serial No. 08/970,867 (Attorney Docket No. 18525-000900), filed November 14, 1997, the full disclosure of which is incorporated herein by reference.

Referring now to Figs. 8 to 10, the present invention further provides an improved spindle motor assembly 34 for engaging and rotating the hub 78 of the disk 66. The spindle motor 34 includes a spindle shaft 124 coupled to a rotor 126. The spindle shaft can be rotatable or fixed. The spindle shaft 124 is configured to enter an opening 79 in the hub of the rotatable disk (Fig. 3B), while a surface of the rotor 126 is adapted to engage the hub 78 of the rotatable disk 66. Top bearings 127a, 127b, and bottom bearings 128a, 128b allow the rotor 126 to rotate relative to the base of the disk drive 26. Spindle motor 34 can be mounted to the base in a variety of ways. One exemplary method is described further in U.S. Patent No. 09/971,033, filed November 14, 1997, the complete disclosure of which is incorporated by reference.

The rotating driving force in the rotor 126 is generated by rotation assembly 130. The rotation assembly 130 is typically housed within a cavity 131 defined by the rotor 126, bearings 126, 128, and base 133. The movement of the rotor 126 is typically achieved through generation of a rotary magnetic field formed by a stator core 132 that is excited by electricity supplied through a stator coil 134. In the configuration illustrated, the stator core 132 and stator coil 134 are fixed. A plurality of driving magnets 136 are positioned on a portion of the rotor 126 around the stator core 132. Delivery of an electric current through the stator coil 134 causes the driving magnets (and attached rotor 126) to rotate the disk hub 66.

To improve the clamping between the rotor 126 and the disk hub 78, a clamping magnet 138 is typically positioned within a recess 140 along the outer surface of the rotor 126. In most configurations, the surface of the rotor and the clamping magnet provide a substantially planar surface which engages the hub 78 of the disk. In other configurations, however, the outer surface of the rotor 126 and the top surface of the clamping magnet 138 can be on different planes such that the magnet or rotor does not contact the hub of the disk. In the exemplary embodiment shown in Fig. 9, the clamp magnet 138 is positioned along the outermost periphery of the rotor 126. However, as shown in Fig. 10 the clamping magnet 138 can be positioned near the outermost portion of the rotor, and does not have to be positioned along the very outermost point. The clamping magnet can be attached continuously around the rotor in an annular pattern (Fig. 2) or can be positioned discontinuously around the rotor (Fig. 5). The clamping magnet(s) 138 can be attached to the rotor 126 with adhesives, or any other conventional or proprietary means, such as screws, rivets, or the like.

Most embodiments of the present invention position the clamp magnet 138 away from the stator coil 134 and closer to the periphery of the rotor 126. By moving the clamp magnet adjacent the outermost portion of the rotor, the stability of the clamping force with the hub can be increased without substantially increasing the size of the magnet. Moreover, as shown in Figs. 9 and 10, moving the clamping magnet 138 radially away from the spindle shaft 124 increases the size of the cavity 131. Consequently, the stator windings or coil 134 can be enlarged and the top bearings 127a, 127b can be moved closer to the center of the disk. The larger stator coil provides a larger motor resistance and larger motor torque. Additionally, moving top bearings 127a, 127b close to disk 66 provides an increased stability to the spindle shaft 124 and reduces the rocking frequency of the rotating disk 66.

Moving the clamping magnet 138 near the outer periphery of the rotor 126 provides at least two benefits. First, because the inner cavity 131 of rotor 126 can be been increased while the overall form factor of the spindle motor 34 is maintained, a more efficient motor can be created without increasing the overall spindle motor size. Second, moving the clamp magnet 138 toward the periphery provides enough space in the cavity to aftow the overall height of the spindle motor 34 to be reduced (H₂ and H₃ < Hi₎ while still maintaining similar performance characteristics (torque, stability, or the like) of the spindle motor. Because the cavity is not limited by the clamping magnet, a same sized stator coils and bearing spacings of Fig. 8 can be used in the "slim-line" spindle motor of Figs. 9 and 10. It has been found that the overall height of the spindle motor can be reduced approximately fifty percent in overall height, while still maintaining the same performance characteristics.

In use, the hard disk cartridge is inserted into the receptacle of the disk drive, as described above. A hub of the recording medium is placed onto the spindle shaft 124. A rotor surface is engaged against the hub of the recording medium and the hub is clamped to the rotor with a clamping magnet. An electrical current is delivered through the stator coil and the rotor is rotated. As discussed above, the clamping magnet is preferably moved to a radially outward position on the rotor so as to increase the size of the cavity. The magnet is typically positioned at a greater radial distance from the spindle than the stator coil and bearings so as to maximize the size of the stator coil and bearing spacing for the given form factor of the spindle motor.

While the exemplary embodiments have been described in some detail, by way of example and for clarity of understanding, a variety of modifications, changes, and adaptations will be obvious to those of skill in the art. The present invention is not limited to these exemplary embodiments and the scope of the present invention is limited solely by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A spindle motor for use with a removable media, the spindle motor comprising: a spindle shaft; bearings which rotatably support the spindle shaft; a rotor coupled to the spindle shaft; a rotation assembly configured to rotate the rotor; and a clamping magnet disposed the rotor to hold the removable media, wherein a radial position of an outside edge of the clamping magnet is greater than a radial position of the rotation assembly.

2. The spindle motor of claim 1 wherein the bearings comprise upper bearings and lower bearings.

3. The spindle motor of claim 1 wherein the rotor comprises a recessed portion that receives the clamping magnet.

4. The spindle motor of claim 3 wherein the rotor defines an outer surface and the clamping magnet defines a top surface, wherein the outer surface of the rotor and the top surface of the clamping magnet define a substantially planar surface.

5. The spindle motor of claim 1 wherein the spindle shaft is rotatable.

6. The spindle motor of claim 1 wherein the spindle motor is fixed.

7. The spindle motor of claim 1 wherein the removable media is a removable hard disk cartridge.

8. The spindle motor of claim 1 wherein the rotation assembly comprises a stator core, a stator coil, and a plurality of driving magnets.

9. The spindle motor of claim 8 wherein the driving magnets comprise an inner portion and a mounting portion, wherein the clamping magnet has a radial position greater than the radial position of the inner portion of the driving magnets.

10. The spindle motor of claim 8 wherein the stator coil comprises electromagnetic windings.

11. The spindle motor of claim 8 wherein the clamping magnet is positioned above the driving magnets.

12. The spindle motor of claim 1 wherein the clamping magnet is annular shaped.

13. The spindle motor of claim 1 wherein the clamping magnet is discontinuously spaced around the periphery of the rotor.

14. The spindle motor of claim 1 wherein the clamping magnet is positioned along a periphery of the rotor.

15. The spindle motor of claim 1 wherein the rotor defines an inner cavity, wherein the rotation assembly is disposed within the inner cavity.

16. A spindle motor for use with a removable cartridge, the spindle motor comprising: a spindle shaft; a rotor coupled to the spindle shaft, the rotor defining a diameter; and a clamping magnet positioned on the rotor such that an outside diameter of the clamping magnet is substantially equal to the diameter of the rotor.

17. The spindle motor of claim 16 further comprising a stator coil and a driving magnet, wherein the stator coil and driving magnet are disposed within an inner cavity that is defined by the rotor.

18. The spindle motor of claim 16 wherein an inside diameter of the clamping magnet is spaced farther from the spindle shaft than the stator coil.

19. A method of rotating a recording medium, the method comprising: placing a hub of the recording medium onto a spindle shaft; engaging a rotor against the hub of the recording medium; clamping the hub to the rotor with a clamping magnet; and rotating the rotor and the clamped hub with a rotation assembly, wherein a radial position of an outside edge of the clamping magnet is greater than a radial position of the rotation assembly.

20. The method of claim 19 wherein the rotor is coupled to the spindle shaft with bearings.

21. The method of claim 20 wherein the clamping magnet is positioned along an outer periphery of the rotor.