Patent Application
20070247945
This invention relates to the field of hard disk drives, and more particularly to a method for providing a bulk erase tool having a portion of reduced field strength.
Hard disk drives are used in almost all computer system operations. In fact, most computing systems are not operational without some type of hard disk drive to store the most basic computing information such as the boot operation, the operating system, the applications, and the like. In general, the hard disk drive is a device which may or may not be removable, but without which the computing system will generally not operate.
The basic hard disk drive model was established approximately 50 years ago and resembles a phonograph. That is, the hard drive model includes a storage disk or hard disk that spins at a standard rotational speed. An actuator arm with a suspended slider is utilized to reach out over the disk. The arm carries a head assembly that has a magnetic read/write transducer or head for reading/writing information to or from a location on the disk. The complete head assembly, e.g., the suspension and head, is called a head gimbal assembly (HGA).
In operation, the hard disk is rotated at a set speed via a spindle motor assembly having a central drive hub. Additionally, there are circumferential tracks evenly spaced at known intervals across the disk. When a request for a read of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head reads the information from the disk. In the same manner, when a request for a write of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head writes the information to the disk.
Over the years, the disk and the head have undergone great reductions in their size. Much of the refinement has been driven by consumer demand for smaller and more portable hard drives such as those used in personal digital assistants (PDAs), MP3 players, and the like. For example, the original hard disk drive had a disk diameter of 24 inches. Modern hard disk drives are much smaller and include disk diameters 3.5 to 1 inches (and even smaller 0.8 inch). Advances in magnetic recording are also primary reasons for the reduction in size.
Advances in magnetic recording are also primary reasons for the reduction in size. For example, advances have led to storage capacities in the range of 120 gigabytes (GB) per square inch of disk real estate. Thus, multi-hard disk drives have capacities in the range hundreds of gigabytes. In the present environment, even small improvements in storage techniques can produce large absolute changes in total capacity. For example, a 4% improvement in the capacity of a 250 GB hard disk drive results in an extra 10 GB of additional storage capacity. This is more than the original capacity of hard disk drives offered in the late 1990's.
After assembling the mechanical components to form the hard disk drive, servo patterns are written on the new disks to prepare the hard disk drives for customer use. However, there are cases when the servo patterns have to be re-written. In those cases, existing servo patterns have to be erased before new servo patterns may be re-written. For example, servo patterns have to be rewritten when the initial servo writing fails, if the servo writing was successful, but the disk drive fails functional tests, or if complete or partial disassembly and reassembly of the mechanical components is needed.
Generally, a bulk erase tool is a magnetic device used to erase the (servo or other) patterns on the disk of a hard disk drive. The advantage of using the bulk erase tool over using the head erase within the hard disk drive is the fast and easy operation of the bulk erase tool. For example, a head erase of the disk may take 20 minutes while a bulk erase of the disk may only take 10 seconds.
However, as disk coercivity becomes higher, the required magnetic field in the bulk erase tool also becomes higher and increases the possibility of damaging the motor magnet and heads of the hard disk drive. For example, one problem with the conventional bulk erase tool design is that the difference between the field at motor magnet and the field at the ID track is too small, i.e., the slope of the erase field curve is not sharp enough. If the drive is inserted deep inside the bulk eraser to erase the ID track then the motor magnet is also exposed to a strong magnetic field which leads to demagnetization of the motor magnet. However, if the drive insertion is adjusted such that no demagnetization of the motor magnet occurs, then the erase field acting on the ID track of the disk is not strong enough to completely erase the disk resulting in residual disk signals. These un-erased tracks have to head-erased which is time-consuming process.
A method for providing a bulk erase tool having a portion of reduced field strength is provided. A bulk erase tool is received. The bulk erase tool has a first polarity top main magnet, a first polarity bottom main magnet, a second polarity top main magnet and a second polarity bottom main magnet. At least one first polarity cancel magnet is provided at a portion of each of the second polarity top and bottom main magnets. Additionally, at least one second polarity cancel magnet is provided at a portion of each of the first polarity top and bottom main magnets. In so doing, the bulk erase tool field strength at a first portion of the bulk erase tool is reduced.
a is a block diagram of one half of an exemplary bulk erase tool in accordance with one embodiment of the present invention.
b is a side sectional view of a complete exemplary bulk erase tool having both top and bottom magnet sets and the optional tray in accordance with one embodiment of the present invention.
Reference will now be made in detail to the alternative embodiment(s) of the present invention, a method for providing a bulk erase tool having a portion of reduced field strength. While the invention will be described in conjunction with the alternative embodiment(s), it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.
Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention.
Embodiments described herein provide a bulk erase tool design for both perpendicular (PR) and longitudinal (LR) recording media using an in-plane magnetic erase field. Moreover, unlike prior bulk erase tools, the present bulk erase tool will not demagnetize the motor magnet. Additionally, because the design provides sharp transition of the erase field with the cancel magnets collocated with the main erase magnets, the field strength near the motor magnet is lowered. At the same time, the field strength is increased near the data track. In other words, embodiments described herein provide a sharp transition of the erase field in the bulk erase tool.
With reference now to
In the exemplary
In the embodiment shown, arm 125 has extending from it at least one cantilevered electrical lead suspension (ELS) 127. It should be understood that ELS 127 may be, in one embodiment, an integrated lead suspension (ILS) that is formed by a subtractive process. In another embodiment, ELS 127 may be formed by an additive process, such as a circuit integrated suspension (CIS). In yet another embodiment, ELS 127 may be a flex-on suspension (FOS) attached to base metal or it may be a flex gimbal suspension assembly (FGSA) that is attached to a base metal layer. The ELS may be any form of lead suspension that can be used in a data access storage device, such as a HDD. A magnetic read/write transducer 131 or head is mounted on a slider 129 and secured to a flexible structure called “flexure” that is part of ELS 127. The read/write heads magnetically read data from and/or magnetically write data to disk 115. The level of integration called the head gimbal assembly (HGA) is the head and the slider 129, which are mounted on suspension 127. The slider 129 is usually bonded to the end of ELS 127.
ELS 127 has a spring-like quality, which biases or presses the air-bearing surface of the slider 129 against the disk 115 to cause the slider 129 to fly at a precise distance from the disk as the disk rotates and air bearing develops pressure. The ELS 127 has a hinge area that provides for the spring-like quality, and a flexing interconnect that supports read and write traces through the hinge area. A voice coil 133, free to move within a conventional voice coil motor magnet assembly 134 (top pole not shown), is also mounted to arms 125 opposite the head gimbal assemblies. Movement of the actuator comb 121 by controller 119 causes the head gimbal assemblies to move along radial arcs across tracks on the disk 115 until the heads settle on their set target tracks. The head gimbal assemblies operate in a conventional manner and always move in unison with one another, unless drive 111 uses multiple independent actuators (not shown) wherein the arms can move independently of one another.
In general, the load/unload drive refers to the operation of the ELS 127 with respect to the operation of the disk drive. That is, when the disk 115 is not rotating, the ELS 127 is unloaded from the disk. For example, when the disk drive is not in operation, the ELS 127 is not located above the disk 115 but is instead located in a holding location on L/UL ramp 197 away from the disk 115 (e.g., unloaded). Then, when the disk drive is operational, the disk(s) are spun up to speed, and the ELS 127 is moved into an operational location above the disk(s) 115 (e.g., loaded). In so doing, the deleterious encounters between the slider and the disk 115 during non-operation of the HDD 111 are greatly reduced. Moreover, due to the movement of the ELS 127 to a secure off-disk location during non-operation, the mechanical ship shock robustness of the HDD is greatly increased.
With reference now to
Referring now to
In one embodiment, the first polarity cancel magnet 325 is embedded into a portion of the second polarity main magnet 320 and the second polarity cancel magnet 315 is embedded into a portion of the first polarity main magnet 310. Although, the first polarity cancel magnet 325 and the second polarity cancel magnet 315 are embedded in the main magnets in one embodiment, the cancel magnets may similarly be placed in openings formed in the main magnets, removably coupled with the main magnets, glued, or otherwise deployed to adjacent positions at an approximate front center portion of the main magnets of the bulk erase tool 300. However, the term embedded is used herein as one embodiment provided for purposes of brevity and clarity.
The first polarity cancel magnet 325 and the second polarity cancel magnet 315 provide reduced bulk erase tool field strength at a first portion 340 of the bulk erase tool 300. The graph of the magnetic field is clearly shown in
Beneficially, the bulk erase tool field strength is reduced at the first portion 340 of the bulk erase tool 300 thereby providing reduced demagnetization characteristics of the bulk erase tool with respect to a motor magnet, such as spindle motor 117, of a hard disk drive.
Moreover, the first and second polarity cancel magnets, 325 and 315 respectively, also provide an increase in the bulk erase tool field strength at a second portion 350 of the bulk erase tool 300. In general, the bulk erase tool field strength is increased at the second portion 350 of the bulk erase tool 300 to provide increased data erase characteristics of the bulk erase tool with respect to a data track of a disk of a hard disk drive.
Referring now to
Optionally, bulk erase tool 360 also includes the optional tray 375 for aligning the hard disk drive 111 to be erased. Although the tray 375 is shown in a location in the gap 385 of the bulk erase tool 360, it is understood that the tray 375 may be located in a plurality of arrangements with respect to the bulk erase tool 360. In general, the gap 385 refers to the distance (or gap length) between the upper magnets and the lower magnets.
In one embodiment, the gap 385 distance is adjustable such that a hard disk drive 111 and the tray 375 can be inserted through the gap 385. For example, in
With reference now to
Referring now to
Thus, when comparing graph 400 to graph 500 it becomes apparent that by changing the location of the cancel magnets 315 and 325, e.g., being collocated with the main magnets 310 and 320, the canceling effect occurs at the front knee of the curve of the erase field which increases the slope of the field. Therefore, if the field at the motor magnet is the same (e.g., 2650 G), the embodiments described herein can apply an additional 1000 G or more of the field to the ID tracks of the disk 115. For example, when the size of the cancel magnet is optimized such that it provides strong canceling field but does not generate any undershoot of the field.
In one embodiment, the disclosed design shows at least 1000 G improvement in the magnitude of the erase field with a magnet size such as, but not limited to, between approximately 50-150 millimeters. In one embodiment, the magnet grade is neomax-50. However, the disclosed magnet grade is provided as an example not as a limitation, and is stated herein merely for purposes of brevity and clarity.
With reference now to
With reference to 602 of
Referring now to 604 of
With reference now to 606 of
Advantageously, as shown in
In one embodiment, the reduction of the bulk erase tool field strength is approximately at a front center portion of the bulk erase tool. However, the reduction in the field strength does not necessarily need to occur in the front center portion of the bulk erase tool 360. The cancel magnets 325 and 315 can be placed in almost any location along the abutment of the top and bottom main magnets 310 and 320 of the bulk erase tool 360. Thus, the use of the front center portion is merely for purposes of brevity and clarity.
Moreover, the at least one first and second polarity cancel magnets, 325 and 315, also provide an increase in the bulk erase tool field strength at a second portion 350 of the bulk erase tool. In so doing, the increase of the bulk erase tool field strength at the second portion 350 of the bulk erase tool 300 significantly increases the data erase characteristics of the bulk erase tool 300 with respect to the data track 225 of the disk 115 of the hard disk drive 111 without deleteriously affecting the magnet motor 117.
Thus, embodiments of the present invention provide a method for providing a bulk erase tool having a portion of reduced field strength. Moreover, embodiments provide a method for providing a bulk erase tool having a portion of reduced field strength that significantly reduces motor magnet demagnetization. Additionally, embodiments provide a method for providing a bulk erase tool having a portion of increased field strength that significantly increases the erase capabilities of the bulk erase tool in regard to both longitudinal and perpendicular recorded media. In so doing, the disk in a hard disk drive is more quickly, efficiently, and properly erased while deleterious magnetic effects on the motor magnet are reduced.
While the method of the embodiment illustrated in flowchart 600 show specific sequences and quantity of steps, the present invention is suitable to alternative embodiments. For example, not all the steps provided for in the methods are required for the present invention. Furthermore, additional steps can be added to the steps presented in the present embodiment. Likewise, the sequences of steps can be modified depending upon the application.
The alternative embodiment(s) of the present invention, a method for providing a bulk erase tool having a portion of reduced field strength is thus described. While the present invention has been described in particular embodiments, it should be appreciated that the present invention should not be construed as limited by such embodiments, but rather construed according to the below claims.
