Abstract:
Systems and methods from loading/unloading a data head for a disk drive provide for more efficient use of disk space. A method of loading/unloading a data head for a disk drive comprises determining a disk phase of a spinning disk arrangement, determining a loading/unloading position based on the disk phase, and loading or unloading the data head on or from, respectively, the spinning disk arrangement based on the determined disk phase. The determining a disk phase may be based on zero crossing of voltages for a three-phase motor associated with the spinning disk arrangement.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application claims priority under 35 U.S.C. §119(e) from U.S. Provisional Application Ser. No. 60/744,983, filed Apr. 17, 2006, incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to the field of disk drives. More specifically, the invention relates to systems, methods and devices for loading or unloading a data head on or from, respectively, a disk. 
     Disk drives, as may be found in computers and like devices, typically include one or more disks with a surface on which data may be written. The data can then be read from the same disk when retrieval of the data is desired. The reading and writing of the data is accomplished by a data head which can take the form of a transducer. A single transducer can read, write or both. 
     In order to read or write, the data head must be positioned slightly above the spinning disk with an air bearing between the data head and the disk surface. When not in use, the data head may be positioned off the disk and safely stowed so as not to contact and damage the disk surface. 
     When positioning the data head above the disk or removing the data head from the disk, there is a danger of contact with the disk surface and resulting damage to the disk and data. To avoid this result, most disks are provided with a landing zone along the perimeter of the disk.  FIG. 1  illustrates one such disk. The disk  10  includes a usable portion  12  on which data may be written and a landing zone  14  along the perimeter. Thus, for loading of the data head, the data head is moved to the landing zone  14  to form the air bearing and subsequently moved to the desired region of the usable portion. Similarly, for unloading, the data head is moved to the landing zone  14  with the air bearing intact and then removed from the disk  10 . However, this arrangement results in a large area of the surface of the disk  10  being rendered unusable by designation as a landing zone  14 . 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention overcome the above-described shortcomings in the prior art. 
     In one aspect of the invention, a method of loading/unloading a data head for a disk drive comprises determining a disk phase of a spinning disk arrangement, determining a loading/unloading position based on the disk phase, and loading or unloading the data head on or from, respectively, the spinning disk arrangement based on the determined disk phase. 
     In one embodiment, the disk phase includes at least one range of phases. The at least one range of phases may be an arc. In a preferred embodiment, each arc covers between 10 and 60 degrees of the perimeter of the spinning disk arrangement. In a further preferred embodiment, each arc covers between 20 and 50 degrees of the perimeter of the spinning disk arrangement. In a most preferred embodiment, each arc covers between 30 and 40 degrees of the perimeter of the spinning disk arrangement. 
     In one embodiment, the determining a disk phase is based on zero crossing of voltages for a three-phase motor associated with the spinning disk arrangement. The three-phase motor may have six zero crossings associated with each phase. 
     In another aspect, the invention relates to a disk drive arrangement comprising a spinning disk arrangement, a data head mounted on a data arm, and a controller adapted to load or unload the data head onto or from the spinning disk arrangement. The controller is adapted to determine a disk phase of the spinning disk arrangement, determine a loading/unloading position based on the disk phase, and load or unload the data head on or from, respectively, the spinning disk arrangement based on the determined disk phase. 
     In another aspect, the invention relates to a computer program product, embodied on a computer-readable medium, for displaying content on a device. The computer program product comprises computer code for determining a disk phase of a spinning disk arrangement, computer code for determining a loading/unloading position based on the disk phase, and computer code for loading or unloading the data head on or from, respectively, the spinning disk arrangement based on the determined disk phase. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a prior art disk; 
         FIG. 2  is a block diagram illustrating a disk drive arrangement according to an embodiment of the present invention; 
         FIG. 3  is a plan view of a disk drive arrangement according to an embodiment of the present invention; 
         FIG. 4  is a plan view of a disk according to an embodiment of the present invention; and 
         FIG. 5  is a chart exemplarily illustrating zero voltage crossings for a spindle motor for use with embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 2 , an embodiment of a disk drive arrangement according to an embodiment of the invention is illustrated as a block diagram. The disk drive arrangement  100  includes a disk module  110  with one or more disks. Each disk in the disk module  110  is adapted to spin about a central axis. The disks in the disk module  110  may spin as a single unit. 
     The spin rate of the disks in the disk module  110  can vary depending on various factors, including processor speed, disk data density and disk size. Various disk modules  110  can have spin rates of, for example, 3600, 5200, 7200, 10,000 or 15,000 revolutions per minute (rpm). For a disk module  110  having a spin rate of 15,000 rpm, the disk makes one revolution in approximately 4 milliseconds (ms). 
     The disk drive arrangement  100  is provided with a spindle motor  130  coupled to the disk module  110 . The spindle motor  130  drives the spinning of the disks of the disk module  110 . The specific design of the spindle motor  130  may vary from one disk drive arrangement to another. 
     In addition to the spindle motor  130 , the disk drive arrangement  100  also includes an arm actuator  140 . The arm actuator  140  drives a data head assembly to be positioned either on or off the disk. The arm actuator  140  is adapted to move the data head to any desired radial position on the disk. 
     A drive controller  120  is coupled to the spindle motor  130  and the arm actuator  140  to control the operation of the disk drive arrangement  100 . The drive controller  120  may also be coupled to other components of the disk drive arrangement  100  not shown in the illustrated example of  FIG. 2 . The drive controller  120  may be implemented in a variety of manners including, but not limited to, a software module or firmware. 
     Referring now to  FIG. 3 , an embodiment of the disk module  110  is illustrated in greater detail. The disk module  110  includes a disk  112  on which data may be contained in the form of magnetic bits, for example. The disk  112  may be of a variety of sizes such as, for example, 3.5-inch diameter or 5.25-inch diameter disk. Those skilled in the art will understand that, in addition to size, such disks may vary in many factors, including, for example, in the material of which they are formed and the density of data they can accommodate. The disk  112  is adapted to spin about a central spindle  132  driven by the spindle motor described above. 
     The disk module  110  is provided with an arm assembly  142  adapted to read from and write to the disk  112 . The arm assembly  142  exemplarily illustrated in  FIG. 3  includes an arm  146  adapted to pivot about an arm pivot  144 . The arm  146  may contain a data head on its free end. The data head may be a transducer adapted to manipulate or detect the magnetic material of the disk  112  to read or write data. The arm assembly  142  is also referred to in the art as a slider assembly. 
     A ramp  148  is provided in the disk module  110  to allow the arm to move onto and off the disk  112  in a gradual manner. In this regard, the ramp  148  is positioned proximate to the outer edge of the disk  112 . 
     Thus, during operation, when a read or write procedure is to be started, the spindle motor first spins the disk to a desired spin rate. As noted above, disk modules may be designed for various spin rates, such as 3600, 5200, 7200, 10,000 or 15,000 rpm. The data head is then positioned to the desired position above the disk  112 . In moving the data head to this position, the arm is moved from its rest position (such as at the top of the ramp  148 ) down the ramp  148  toward the outer perimeter of the disk by use of the arm actuator. In this regard, the ramp  148  may be a wedge-shaped component which terminates at the outer perimeter of the disk  112  at approximately the desired height of the data head relative to the surface of the disk  112 . As the arm  146  moves down the ramp  148  and above the disk  112 , an air bearing is formed between the data head and the spinning disk  112  above the landing zone (as described above with reference to  FIG. 1 ). Now, the data head can be moved to the desired position in the usable portion of the disk  112 . 
     Similarly, when the data head is to be removed from the disk, the arm  146  is moved such that the data head is in the landing zone and onto the ramp. The spinning of the disk  112  is then stopped. 
     In accordance with embodiments of the present invention, the region of the disk rendered unavailable for data storage by designation as part of the landing zone is reduced. In this regard, as exemplarily illustrated in  FIG. 4 , the landing zone is determined based on the phase of the disk. For example, the embodiment of the disk  400  illustrated in  FIG. 4 , includes three landing zones  420  at portions of the perimeter of the disk  400 , increasing the size of the usable portion  410  of the disk  400 . 
     Thus, as the disk is spinning, the disk phase is determined, and the loading or unloading position on the disk (or landing zone) is determined based on the disk phase. The loading or unloading of the data head onto the disk is then initiated so that the data head loads or unloads at the loading or unloading position on the disk. 
     In one embodiment, the disk phase is determined by monitoring or detection of the zero voltage crossings of a three-phase spindle motor. Three-phase motors are well known in the art and do not require additional description here. 
     The zero crossings of a three-phase motor are based on the winding pattern of the motor. In one embodiment, a spindle motor has twelve zero crossings per revolution, corresponding to six zero crossings with each of the three phases of the motor. For an ideal (theoretical) three-phase motor, the zero-crossings are equally spaced. However, in real three-phase motors, slight variations in the windings cause the zero crossings to deviate from the ideal timing. Such deviations can be small, such as on the order of microseconds. 
       FIG. 5  is a chart illustrating the timing pattern of the zero crossings for one revolution of a three-phase motor with twelve zero crossings per revolution. The horizontal axis of the chart indicates the zero crossings in succession during a revolution. The vertical axis of the chart indicates the deviation in the timing from the ideal of each zero crossing. Thus, the first zero crossing occurs approximately seven microseconds later than expected, while the second zero crossing occurs approximately five microseconds earlier than expected. Similar timings are illustrated for each of the other ten zero crossings. With the spindle motor driving the disk at a constant spinning rate, the pattern of the zero crossings repeats for each revolution. Minor perturbations may be experienced due to electrical noise, but the pattern is not significantly affected. 
     Within a single revolution, the pattern repeats three times. With the pattern recorded, a loading/unloading zone may be associated with a point in the pattern. For example, with the zero crossing pattern illustrated in  FIG. 5 , the second, eighth and fourteenth zero crossings may be selected to correspond to the loading/unloading zone. Thus, the arm actuator is timed to load or unload the data head from the disk when the disk phase corresponds to one of the three zero crossings associated with the loading/unloading zone. 
     In other embodiments, a single zero crossing may be uniquely identified. In this regard, a single loading/unloading zone may be allocated to correspond to the single zero crossing. Further embodiments may include any practical number of loading/unloading zones corresponding to the practical number of identifiable zero crossings. 
     Thus, small regions on the perimeter of the disk may be associated with the loading or unloading of the data head, while the remainder of the perimeter of the disk is available for data storage. In the illustrated embodiment, the loading/unloading zones  420  ( FIG. 4 ) are formed as arcs along the perimeter. In one embodiment, each arc of loading/unloading zone  420  has a radial width of between 100 and 1000 microns. In one example, for a disk having a spin rate of 15,000 rpm, the length of each arc may encompass between 10 and 60 degrees of rotation of the perimeter of the disk, preferably between 20 and 50 degrees, and more preferably between 30 and 40 degrees. 
     In one embodiment, with the disk having a spin rate of 6,000 rpm, each revolution takes approximately ten (10) ms. The accuracy of measurement of the disk phase using the timing of the zero crossings may be between 200 nanoseconds and 2 microseconds. Further, the accuracy with which the arm and data head can be loaded or unloaded may be between 100 and 500 microseconds. With these inaccuracies, each loading/unloading regions should account for approximately five percent (5%) of the perimeter region. Thus, in embodiments having three loading/unloading zones, approximately fifteen percent (15%) of the perimeter region is allocated for loading/unloading zones. For disks with faster spinning rates, a larger portion of the arc may be required. 
     Thus, up to eighty-five percent (85%) of the perimeter region can be recovered for use for data storage rather than loading/unloading zone. 
     The foregoing description of embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variation are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modification as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.