Abstract:
A hard disk drive bypass channel architecture incorporates enhanced cooling for voice coil motors. A cooling slot formed in a bypass channel component that is adjacent to the VCM alleviates VCM overheating problems. The slot compromises airflow from the bypass channel to provide sufficient secondary flow to cool the VCM and actuator coil area. The slot may be formed in the integrated wall of the spoiler or diverter. The spoiler has an extension in which the cooling slot is formed.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates in general to hard disk drives and, in particular, to an improved system, method, and apparatus for enhanced cooling of voice coil motors in hard disk drives. 
     2. Description of the Related Art 
     Data access and storage systems generally comprise one or more storage devices that store data on magnetic or optical storage media. For example, a magnetic storage device is known as a direct access storage device (DASD) or a hard disk drive (HDD) and includes one or more disks and a disk controller to manage local operations concerning the disks. The hard disks themselves are usually made of aluminum alloy or a mixture of glass and ceramic, and are covered with a magnetic coating. Typically, one to five disks are stacked vertically on a common spindle that is turned by a disk drive motor at several thousand revolutions per minute (rpm). Hard disk drives have several different typical standard sizes or formats, including server, desktop, mobile (2.5 and 1.8 inches) and microdrive. 
     A typical HDD also uses an actuator assembly to move magnetic read/write heads to the desired location on the rotating disk so as to write information to or read data from that location. Within most HDDs, the magnetic read/write head is mounted on a slider. A slider generally serves to mechanically support the head and any electrical connections between the head and the rest of the disk drive system. The slider is aerodynamically shaped to glide over moving air in order to maintain a uniform distance from the surface of the rotating disk, thereby preventing the head from undesirably contacting the disk. 
     A slider is typically formed with an aerodynamic pattern of protrusions on its air bearing surface (ABS) that enables the slider to fly at a constant height close to the disk during operation of the disk drive. A slider is associated with each side of each disk and flies just over the disk&#39;s surface. Each slider is mounted on a suspension to form a head gimbal assembly (HGA). The HGA is then attached to a semi-rigid actuator arm that supports the entire head flying unit. Several semi-rigid arms may be combined to form a single movable unit having either a linear bearing or a rotary pivotal bearing system. 
     The head and arm assembly is linearly or pivotally moved utilizing a magnet/coil structure that is often called a voice coil motor (VCM). The stator of a VCM is mounted to a base plate or casting on which the spindle is also mounted. The base casting with its spindle, actuator VCM, and internal filtration system is then enclosed with a cover and seal assembly to ensure that no contaminants can enter and adversely affect the reliability of the slider flying over the disk. When current is fed to the motor, the VCM develops force or torque that is substantially proportional to the applied current. The arm acceleration is therefore substantially proportional to the magnitude of the current. As the read/write head approaches a desired track, a reverse polarity signal is applied to the actuator, causing the signal to act as a brake, and ideally causing the read/write head to stop and settle directly over the desired track. 
     During operation, the VCM is prone to heat up to maintain fast seek times in high performance server class disk drives. Accordingly, the temperature of the VCM must be monitored since excessive temperature can degrade performance of the drive. In some operating environments and severe cases, the high temperatures generated by disk drives can melt the coil insulation and coating, thus resulting in catastrophic failures in the drive, such as outgassing, contamination, etc. 
     Some disk drives utilize a bypass channel to regulate airflow within the disk drive. With bypass architecture, the airflow is stripped from the disk pack, commonly by a diverter or spoiler, and diverted into the bypass channel. Ideally, the bypass channel should have no interruptions or leakage in order to maintain the airflow momentum throughout the channel. Unfortunately, this poses a dilemma for temperature-sensitive areas of the drive, such as the VCM, since bypass channels allow little or no flow into the VCM area. Thus, an improved airflow solution that satisfies the multiple and sometimes conflicting interests of bypass architecture would be desirable. 
     SUMMARY OF THE INVENTION 
     Embodiments of a system, method, and apparatus for enhanced cooling of VCMs in hard disk drives are disclosed. The invention helps alleviate overheating problems with VCMs by slightly compromising the airflow from the bypass channel. Sufficient secondary flow is provided to cool the VCM and actuator coil area. In one embodiment, the spoiler or diverter forms an integrated wall with the bypass channel that serves as an extension to the channel wall, which may be cast into the base casting of the disk drive enclosure. The spoiler, as a channel wall extension, is provided with a cooling slot that can be varied according to the cooling capacity required for specific disk drives and designs. The invention provides a significant increase in coil cooling capacity for slot geometries over previous designs with no slot provided. 
     The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the present invention, taken in conjunction with the appended claims and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the features and advantages of the present invention, which will become apparent, are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof that are illustrated in the appended drawings which form a part of this specification. It is to be noted, however, that the drawings illustrate only some embodiments of the invention and therefore are not to be considered limiting of its scope as the invention may admit to other equally effective embodiments. 
         FIG. 1  is a plan view of one embodiment of a disk drive constructed in accordance with the present invention; 
         FIG. 2  is an isometric view of the disk drive of  FIG. 1  and is constructed in accordance with the present invention; 
         FIG. 3  is a plot of coil power and temperature for disk drives; and 
         FIG. 4  is a high level flow diagram of a method in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 and 2 , one embodiment of a system, method, and apparatus for an information storage system comprising a magnetic hard disk file or drive  111  for a computer system is shown. Drive  111  has an outer housing including a base  113  and top cover (not shown). The housing contains a disk pack having at least one media disk, e.g., magnetic disk  115 . The disks  115  are rotated (see arrows  205 ) by a spindle motor assembly having a central drive hub  117 . An actuator  121  comprises a plurality of parallel actuator arms  125  in the form of a comb that is pivotally mounted to base  113  about a pivot assembly  123 . A controller  119  is also mounted to base  113  for selectively moving the comb of arms  125  relative to disk  115 . 
     Each arm  125  has extending from it at least one cantilevered load beam and suspension  127 . A magnetic read/write transducer or head is mounted on a slider  129  and secured to a flexure that is flexibly mounted to each suspension  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 . 
     Suspensions  127  bias 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. A voice coil  133  free to move within a voice coil motor magnet assembly (not shown) is also mounted to arms  125  opposite the head gimbal assemblies. Movement of the actuator  121  (indicated by arrow  135 ) moves the head gimbal assemblies along radial arcs across tracks on the disk  115  until the heads settle on their respective 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. 
     The disks  115  define an axis  201  of rotation and a radial direction  207 . The disks  115  have a downstream side  213  wherein air flows away from the disks  115 , and an upstream side  215  wherein air flows toward the disks  115 . The drive  111  also has a bypass channel  219  located in the housing  113  for directing the air flow generated by rotation of the disks  115  from the downstream side  213  of the disk pack or disks  115  to the upstream side  215  of the disks  115 . In this way the airflow substantially bypasses the actuator  121  and voice coil motor assembly. 
     In the embodiment shown, the bypass channel  219  is located between an outer perimeter  217  of the housing  113  and the actuator  121 , such that the bypass channel  219  completely circumscribes the actuator  121 . The elements that define the bypass channel  219  may be integrally formed (e.g., cast) with the base  113 . In some HDD designs where there is insufficient space to implement a full bypass channel (shown) the bypass channel  219  may be abbreviated (not shown), which is known as a partial bypass. Furthermore, in order to help the bypass airflow negotiate substantial angular changes (channel bends), one or more turning vanes may be placed in those areas. 
     The drive  111  also may comprise a slot  300  that is located adjacent to the voice coil motor assembly. The slot  300  is designed to be integrated and work with the bypass channel  219  for diverting a portion of the overall airflow toward and through the voice coil motor assembly. The bypass channel  219  includes inner and outer walls  301 ,  303  that define the conduit for the airflow. The slot  300  comprises an opening that is formed in the inner wall  301  next to the magnet, and may comprise a same axial dimension as that of the inner wall  301 . The slot  300  may span a linear gap (i.e., generally in a radial direction relative to the disk  115 ) of approximately 1 mm to 20 mm. For example, a typical 3.5-inch server class drive the gap may comprise about 5 mm. As shown in the drawings, the slot  300  may comprise a flat rectangular hole. 
     As shown in the illustrated embodiment of  FIGS. 1 and 2 , the slot  300  in the inner wall  301  of the bypass channel  219  is located on the downstream side  213  (reference  FIG. 1 ) of the media disk  115 . The slot  300  may be defined between a spoiler or diverter  311 , which forms an integrated wall with the bypass channel  219 , and the inner wall  301  formed in the base casting  113 . An extension  313  extends from the diverter  311  toward the inner wall  301 . The distance between the end of the extension  313  on the diverter  311  defines the cooling slot  300 . The location and size of the slot  300  may be varied according to the cooling capacity required for the VCMs of specific disk drives and designs. 
     As shown in  FIG. 3 , the invention provides a significant increase in coil cooling capacity for slot geometries over previous designs with no slot provided. For example, plot  321  depicts the coil temperature in a conventional disk drive having no cooling slot, while plot  323  depicts a drive equipped with the cooling slot of the present invention. 
     Referring now to  FIG. 4 , the invention also comprises a method of directing airflow in a disk drive. In one embodiment the method comprises providing the disk drive with a media disk, an actuator having a voice coil motor assembly, and a bypass channel (step  401 ); directing airflow around the actuator with the bypass channel (step  403 ); diverting a portion of the airflow from the bypass channel directly toward the voice coil motor assembly for cooling the voice coil motor assembly (step  405 ); before ending as indicated. The method may further comprise other embodiments as shown and described herein. 
     While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.