Abstract:
A bearing system having variably grooved radial and thrust bearing with reduced groove angle near bearing entry is described. In an embodiment, the bearing system includes a housing. The bearing system also includes a shaft centrally located in the housing. The bearing system additionally includes a rotor portion that is adapted to be rotated about the shaft and contained within the housing. The bearing further includes a variably angled groove disposed on an internal surface of the bearing system. The variably angled groove reduces ingestion of air in the bearing system during operation of the bearing system.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to spindle motors having fluid dynamic bearings. More precisely, the present invention relates to a spindle motor having a variably grooved radial and thrust bearing with a reduced groove angle.  
       BACKGROUND OF THE INVENTION  
       [0002]     Hard disk drives are used in almost all computer system operations, and recently even in consumer electronic devices such as digital cameras, video recorders, and audio (MP3) players. 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. However, some computer systems exist in which the hard drive function is performed by compact flash memory.  
         [0003]     The basic hard disk drive model was established approximately 50 years ago. The hard drive model includes a plurality of storage disks or hard disks vertically aligned about a central core that can spin at a wide range of standard rotational speeds depending on the computing application in which the hard disk drive is being used. Commonly, the central core is comprised, in part, of a spindle motor for providing rotation of the hard disks at a defined rotational speed. A plurality of magnetic read/write transducer heads, commonly one read/write transducer head per surface of a disk, where a head reads data from and writes data to a surface of a disk, are mounted on actuator arms.  
         [0004]     Data is formatted as written magnetic transitions (information bits) on data tracks evenly spaced at known intervals across the disk. An actuator arm is utilized to reach out over the disk to or from a location on the disk where information is stored. The complete assembly at the extreme of the actuator arm, e.g., the suspension and magnetic read/write transducer head, is known as a head gimbal assembly (HGA).  
         [0005]     In operation, pluralities of hard disks are rotated at a set speed via a spindle motor assembly having a central drive hub. Current types of spindle motors include, but are not limited to, various types of bearing systems having a rotating or fixed shaft. Additionally, there are channels or tracks evenly spaced at known intervals across the disks. When a request for a read of a specific portion or track is received, the hard disk drive aligns a head, via the actuator 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 drive aligns a head, via the actuator arm, over the specific track location and the head writes the information to the disk.  
         [0006]     Many of today&#39;s hard disk drives, particularly those hard disk drives that are designed to operate at high revolutions, e.g., above 10,000 rpm, include a spindle motor comprising, in part, a fluid dynamic bearing (FDB). An FDB may have a rotating sleeve (fixed shaft) or a rotating shaft (fixed sleeve). It is well known in the art that an FDB provides improved functionality and performance compared with a spindle motor having a ball bearing system.  
         [0007]     In particular, it is common for an FDB with a rotating or fixed shaft to be configured with internally disposed grooves that may be configured in, but is not limited to, a herringbone-pattern or a spiral pattern. Grooves (recesses or troughs) and lands (non-recessed areas) are oriented in such an arrangement as to cause pressure between the rotor and stator and it is this pressure that allows the rotor to spin in a stable manner around the shaft, ideally without contact between the stator and the rotor. It is also common for the rotor to be symmetrical from top to bottom. As the rotor spins, upon which the grooves may be located, the grooves cause pressurization of the fluid (oil, air, or other substance) inside the FDB. This allows the rotor to spin freely around the fixed shaft. This is similar to being suspended in oil, with no solid contact between the stator and the rotor.  
         [0008]     With reference to a herringbone-patterned FDB, it is common for one of the grooves to be longer than the other grooves, referred to as the unbalanced length or portion. The reason for the unbalanced length is to accommodate the oil air interface (OAI), also referred to as the meniscus. A fixed shaft design (FSD) type of a fluid dynamic bearing (FDB) enables the rotor to spin very smoothly around the shaft. A FSD type FSB is commonly, but not always, implemented in high end server or enterprise type hard disk drives, e.g., those hard disk drives having extremely high capacity and fast rotating speeds. These types of hard disk drives are commonly implemented in server farms and hard disk drive farms. It is not uncommon for a hard disk drive configured with a FSD FDB to reach rotating speeds in excess of 15,000 rpm.  
         [0009]     Most fixed shaft design fluid dynamic bearings (FSD FDBs) currently available have groove angles that are constant, relative to bearing shaft perpendicularity. It is well known in the art that the groove angle and bearing stiffness are interrelated. Bearing stiffness within an FDB describes the tendency/ability of the bearing to restore itself, e.g., correct itself relative to a force applied. This is commonly referred to as radial stiffness. Radial stiffness correlates to bearing groove angle. As the groove angle is decreased, bearing stiffness is reduced and when the groove angle is increased, radial stiffness increases. It is also well knows that a groove angle of approximately twenty degrees provides maximum stiffness without detrimentally affecting FDB operation. It is noted that when the groove angle exceeds twenty degrees, the stiffness decreases. It is also well known that a groove angle of less than five degrees will render most FDBs inoperable.  
         [0010]     It is well known that when there is an oil and air interface, there is surface tension between the two substances. It is this surface tension that stabilizes the oil in the bearing. When the oil air interface (OAI) is located among grooves, the interface may deform such that it is drawn into the grooves. This is problematic because this is where the danger of air ingestion can occur. With reference to the oil air interface (OAI), the OAI is substantially horizontal when the bearing is not in operation, relative to the vertical axis of the FDB. During FDB operation, the OAI exhibits a wobbly or wave-like shape, similar to a sinusoidal waveform, such that the OAI rises and falls within the bearing system. As the motor is spinning, the oil is drawn into the grooves and pushed outward over the lands. Further, as the speed of the motor increases, the wave-like phenomenon of the OAI becomes extreme, such that the surface of the OAI can form cusps, as shown in prior art  FIGS. 8, 9 ,  10  and  11 .  
         [0011]      FIG. 7  is an isometric view of the fluid/liquid  10  in a typical FDB, if one could make rigid the fluid and remove all the metal parts there from. FDB fluid  10  shows a spiral pattern  8  that is representative of grooves that would be disposed upon a surface of the thrust bearing of an FDB. FDB liquid  10  also shows a herringbone pattern  9  that is representative of grooves that would be located on a journal or radial surface of the shaft of the FDB. Also shown in FDB fluid  10  is an oil air interface (OAI)  7 . OAI  7  is located near the opening of an FDB when the FDB is idle, and the OAI migrates into the herringbone groove pattern during operation of the FDB. It is noted that the groove angles are constant with the exception of the rounding near the apex of herringbone pattern  9 .  
         [0012]      FIG. 8  shows a line  11  representing an oil air interface in which a bearing system is at rest.  FIG. 9  shows a line  12  representing an oil air interface in which the bearing system is now rotating.  FIG. 9  also includes a cusp  22  that is formed as the fluid is drawn into a groove within the bearing system as the rotational speed of the rotor increases.  FIG. 10  includes a line  13  representing an oil air interface in which the bearing system is rotating faster than the bearing system shown in  FIG. 9 .  FIG. 10  also includes a cusp  23 , formed by the fluid being drawn into a groove in which cusp  23  is deeper and sharper than cusp  22  of  FIG. 9 . The cusp increase is caused by the increased rotational speed of the rotor within the bearing system. It is well knows that increased rotational speeds can cause the OAI to become very sharp, such that it can draw air into the liquid.  FIG. 11  illustrates such an occurrence.  FIG. 11  includes a line  14  representing an oil air interface in which the bearing system is rotating faster than that shown in  FIG. 10 .  FIG. 11  also includes a cusp  24 , formed by the fluid being drawn into a groove, in which the cusp is deeper and sharper that cusp  24  of  FIG. 9 .  FIG. 11  further includes a plurality of bubbles  34  formed as a result of cusp  24  peaking because of increased rotating speed of the bearing system.  
         [0013]     When air is drawn into the liquid, this is very detrimental to the operation and function of the FDB. For the liquid, e.g., oil, to operate properly, the liquid needs to be very incompressible, thus providing high stiffness during operation. Incompressibility refers to the characteristic of the liquid to resist change in volume as a result of a pressure applied thereto. When air bubbles are formed in a liquid, the liquid becomes gummy or mushy, similar to hydraulic brakes when air gets into the brake fluid, such that it is quite difficult to apply firm pressure.  
         [0014]     During FDB operation, there is a capillary number that is a key parameter in this type of flow phenomenon, e.g., the formation of a cusp. The capillary number is derived from the viscosity of the liquid times speed with which the grooves pass the stator divided by surface tension. The higher the value of the capillary number, the greater the chance of air ingestion occurring during operation.  
         [0015]     Accordingly, many of today&#39;s currently available FDBs are prone to the phenomenon of air ingestion. Thus, a need exists for an FDB that can substantially reduce instances of air ingestion occurring during operation.  
       SUMMARY OF THE INVENTION  
       [0016]     Embodiments of the present invention provide such a fluid dynamic bearing that can reduce instances of air ingestion. In an embodiment, a bearing system having variably grooved radial and thrust bearing with reduced groove angle near bearing entry is described. In an embodiment, the bearing system includes a housing. The bearing system also includes a shaft centrally located in the housing. The bearing system additionally includes a rotor portion that is adapted to be rotated about the shaft and contained within the housing. The bearing further includes a variably angled groove disposed on an internal surface of the bearing system. The variably angled groove reduces ingestion of air in the bearing system during operation of the bearing system.  
         [0017]     These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention:  
         [0019]      FIG. 1  is a block diagram of a hard disk drive including a spindle motor upon which embodiments of the present invention may be practiced.  
         [0020]      FIG. 2  is a cross section view of a bearing system in a spindle motor implementable in the hard disk drive of  FIG. 1  in accordance with embodiments of the present invention.  
         [0021]      FIG. 3  is an illustration of herringbone-patterned grooves implementable in the bearing system of  FIG. 2 , in accordance with embodiments of the present invention.  
         [0022]      FIG. 4  is an illustration of spiral-patterned grooves implementable in the bearing system of  FIG. 2 , in accordance with embodiments of the present invention.  
         [0023]      FIG. 5  is a graph illustrating stiffness of a bearing system as it relates to groove angle, in accordance with embodiments of the present invention.  
         [0024]      FIG. 6A  is a profile of a rectangular groove shape implementable in the bearing system of  FIG. 2 , in accordance with embodiments of the present invention.  
         [0025]      FIG. 6B  is a profile of a rounded groove shape implementable in the bearing system of  FIG. 2 , in accordance with embodiments of the present invention.  
         [0026]      FIG. 6C  is a profile of a saw tooth groove shape implementable in the bearing system of  FIG. 2 , in accordance with embodiments of the present invention.  
         [0027]      FIG. 6D  is a profile of a stepped groove shape implementable in the bearing system of  FIG. 2 , in accordance with embodiments of the present invention.  
         [0028]      FIG. 7  is an isometric view of the fluid in a conventional fluid dynamic bearing system if all the metal was removed.  
         [0029]      FIG. 8  is an initial sequential illustration of an oil air interface of the fluid dynamic bearing of  FIG. 7  in which the bearing system is idle.  
         [0030]      FIG. 9  is a subsequent sequential illustration of the oil air interface of  FIG. 8  of the fluid dynamic bearing of  FIG. 7  in which the bearing system is rotating and which shows the formation of a cusp.  
         [0031]      FIG. 10  is a subsequent sequential illustration of the oil air interface of  FIG. 9  of the fluid dynamic bearing of  FIG. 7  in which the bearing is rotating faster than that shown in  FIG. 9 , and which shows a more pronounced cusp than in  FIG. 9 .  
         [0032]      FIG. 11  is a subsequent sequential illustration of the oil air interface  FIG. 10  of the fluid dynamic bearing of  FIG. 7  in which the bearing is rotating at near maximum speed and which shows a cusp having a peak that can cause the ingestion or injection of air into the fluid.  
     
    
     DETAILED DESCRIPTION  
       [0033]     A method and system for reducing air ingestion during operation of a fluid dynamic bearing of a hard disk drive is described. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It is noted that one skilled in the art will comprehend that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the present invention.  
         [0034]     Some portions of the detailed descriptions, which follow, are presented in terms of procedures, steps, logic blocks, processing, and other symbolic representations of operations that can be performed in the operation of a hard disk drive. These descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. A procedure, executed step, logic block, process, etc., is here, and generally, conceived to be a self-consistent sequence of steps, instructions, or fabrications leading to a desired result. The steps are those requiring physical manipulations of physical entities and/or quantities. Usually, though not necessarily always, these entities take the form of structures, components, and/or circuits utilized in the operation of a hard disk drive.  
         [0035]     It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical entities and are merely convenient labels applied to these entities. It is noted that throughout the present invention, discussions are presented that refer to actions and/or processes of a tracing in conjunction with a load beam of a suspension during hard disk drive operation or other such data storage enabling devices.  
         [0036]     The present invention is discussed primarily in the context of a high performance hard disk drive, such as those operating near or above 10,000 revolutions per minute. In the present implementation, the high performance hard disk drive described herein and upon which embodiments of the present invention are practiced contains five hard disks and, accordingly, ten read/write heads. Embodiments of the present invention can be readily implemented in conventionally sized high performance hard disk drives, e.g., 3.5 inch, as well as diminutively sized hard disk drives, including those of low profile height. Embodiments of the present invention are well suited to be used with alternative types of hard disk drives including, but which is not limited to, low profile hard drives (e.g., 1.8 inch form factor HDDs), embedded hard disk drives, hard disk drives having a fewer or greater numbers of hard disks and fewer or greater numbers of read/write heads and other data storage devices that have the capability to access a data storage device and upon which data can be stored and/or from which data can be manipulated.  
         [0037]      FIG. 1  shows a schematic of a hard disk drive  111  in which embodiments of the present invention can be implemented. Hard disk drive  111  can be a conventionally sized high performance hard disk drive, a low profile high performance hard disk drive such as a 1.8-inch form factor or other high performance hard disk drives. It is particularly noted that embodiments of the present invention are well suited for implementation in most hard disk drives including, but not limited to, conventionally sized (e.g., 3.5 inch) hard disk drives, low profile hard disk drives, miniature hard disk drives, and micro drive hard disk drives. It is further noted that embodiments of the present invention are also well suited for implementation in, but which are not limited to, automotive navigation systems, spindle motors for high-density optical disks and polygon scanner motors.  
         [0038]     Hard disk drive  111  includes an outer housing or base  113  containing one (shown) or more magnetic disks  115 . Hard disk drive  111  also includes a cover (not shown) for enclosing housing  113 . In an implementation, hard disk drive  111  can be configured with five hard disks  115  and ten read/write heads  108 . In another implementation, hard disk drive  111  can be configured with three hard disks  115  and five read/write heads  108 . Alternatively, hard disk drive  111  may have greater numbers or fewer numbers of hard disks  115 , and as such would have greater or fewer numbers of read/write heads  108 .  
         [0039]     Disks  115  are suitably fixed to a central drive hub assembly  133  of a spindle motor assembly  100  that rotates about a suitable bearing system  110 . An actuator  101  includes a plurality of actuator arms  104  (one shown) in the form of a comb that is pivotally mounted above a pivot assembly  103 . A controller  119  is also coupled to base  113  for selectively moving the actuator arm  104  relative to disk  115 . A spindle motor assembly  100  having a central drive hub  133  rotates magnetic disks  115 .  
         [0040]     Within spindle motor assembly  100  there is a bearing system  110  containing a shaft and sleeve assembly. In accordance with embodiments of the present invention, bearing system  110  can be a fixed shaft/rotating sleeve shaft design fluid dynamic bearing (FSD FDB) system. In still another embodiment, bearing system  110  can be a rotating shaft/fixed sleeve fluid dynamic bearing (FDB) system.  
         [0041]     In the embodiment shown in  FIG. 1 , actuator arm  104  has extending there from a cantilevered load beam or suspension  106 , a magnetic read/write transducer or head  108  mounted on a slider secured to a flexure that is flexibly mounted to each suspension  106 . Read/write head  108  magnetically reads data from and magnetically writes data to disk  115 . The head gimbal assembly is read/write head and slider  108  mounted on suspension  106 . Suspension  106  has a spring like quality for biasing or urging the slider against the disk to enable the creation of air bearing film, or air bearing surface, between the slider and the disk surface. A voice coil  116  housed within a conventional voice coil motor magnet (VCM) assembly  117  (top pole not shown) having a magnet  118  (not shown) is also mounted to actuator arm  104  opposite the head gimbal assembly. Movement of the actuator  101  by controller  119  moves the head gimbal assembly radially across tracks on the disks  115  (inwardly as indicated by arrow  136   i  and outwardly as indicated by arrow  136   o  ) until heads  108  settle on the target tracks.  
         [0042]      FIG. 2  is a cross-section block diagram of a bearing system upon which embodiments of the present may be practiced, in accordance with embodiments of the present invention.  FIG. 2  shows a fixed shaft design (FSD) fluid dynamic bearing (FDB)  110  having a fixed central shaft  241  around which a rotor  240  rotates. A barrier film  262  is substantially equidistant between opening end  270 , located at one end of bearing  110  and an apex  271 , located at an opposing end of bearing system  110 . Barrier film  262  is provided to resist the flow of the fluid contained therein, so as to prevent the fluid from escaping bearing system  110 .  
         [0043]     Bearing system  110  also includes a plurality of grooves  250  and  260 , in accordance with embodiments of the present invention. Grooves  250  are shown in a cross-section view and grooves  260  are shown in a top view. In an embodiment, grooves  250  are configured in a herringbone pattern  251 . Grooves  250  are commonly, but not always, located on journal surfaces of shaft  241 . Alternatively, grooves  250  may be disposed on an inner surface of rotor  240 . In an embodiment, grooves  260  are configured in a spiral pattern  261 . Grooves  260  are commonly, but not always located on the thrust surfaces of bearing system  110 . It is noted that although only one set of grooves  260  is shown in detail, there are two individual sets of grooves  260 , in which a set of grooves  260  is interposed between opening  270  and rotor  250  of bearing system  110 . A second set of grooves  260  is interposed between apex  271  and rotor  250  of bearing system  110 .  
         [0044]      FIG. 2  also includes an exploded view of grooves  250 , shown in dotted circle  280 , and grooves  260 , shown in solid circle  290 . Within circle  280 , shown are grooves  250  configured in a herringbone pattern  251 , in an embodiment of the present invention. Within circle  290 , shown are grooves  260  appearing as a spiral pattern  261 , in another embodiment of the present invention. It is noted that while grooves  250  and  260  are primarily discussed in a herringbone or spiral groove pattern, these patterns are exemplary, and as such should not be construed as a limitation as to their shape or design. It is further noted that circle  290  is representative of the shape of bearing system  110 .  
         [0045]      FIG. 3  is a plan view of grooves  250  in a herringbone pattern  251  in accordance with embodiments of the present invention. In an embodiment, grooves  250 , shown in herringbone pattern  251 , can be configured such that a plurality of groove angles may be implemented in the fabrication of a fixed shaft design fluid dynamic bearing, in accordance with embodiments of the present invention. In an embodiment of the present invention, grooves  250  may be disposed on a surface of shaft  241  of bearing system  110 . In an alternative embodiment, grooves may be disposed on a surface of rotor  240  of bearing system  110 . Herringbone pattern  251  includes an outer boundary  249  and an inner boundary  248 . Herringbone pattern  251  includes a plurality of grooves  250  and lands  252 , in accordance with embodiments of the present invention.  
         [0046]     Within herringbone pattern  251  of grooves  250 , shown are a first and second set of groove angles. First or initial groove angle  310  is located toward an opening  305  of bearing system  110  in which grooves  250  may be implemented. Initial groove angle  310  can be, but is not limited to, approximately five degrees. In an embodiment of the present invention, groove angle is five degrees. In an alternative embodiment, groove angle  310  may range from zero degrees to ten degrees. Groove angle  310  can be constant until reaching a second groove angle, groove angle  311 , shown as discreet jump point  375 , in accordance with embodiments of the present invention. Groove angle  311  can be, but is not limited to, twenty degrees. Groove angle  311  can be constant until reaching an apex  377  of herringbone pattern  251  in accordance with embodiments of the present invention. In an embodiment, apex  377  can be, but is not limited to ninety degrees. Alternatively, groove angle  310  can be greater or smaller than five degrees, groove angle  311  can be greater or smaller than twenty degrees, and apex  377  can be greater or smaller than ninety degrees.  
         [0047]     It is noted that if the smooth bearing surface is stationary, the grooves would move from right to left. For stationary grooves, the smooth rotor would move from left to right.  
         [0048]     Still referring to  FIG. 3 , it is noted that the width of grooves  250  are narrow at opening  305  and widen at discreet jump point  375  and then widen again at discreet jump point  376 . The width of grooves  250  is related to the groove angle of groove  250  dependent upon the point of reference. It is particularly noted that in an embodiment of the present invention, groove angle  310  is five degrees and groove angle  311  is twenty degrees.  
         [0049]     Advantageously, by implementing a groove pattern  251  having a variable groove angle, e.g., groove angles  310  and  311 , embodiments of the present invention provide, with the initial groove angle, a means for a gradual building of pressure within the bearing system  110 , although a groove angle of five degrees does not provide desired rotational support of the bearing system. Therefore, embodiments of the present invention further provide a second groove angle that does provide desired rotational support of the bearing system  110  when under operation. This variable grove angle provides both a reduction in air injection/ingestion and proper rotational stability for the bearing system  110  in which grooves  250  may be implemented.  
         [0050]      FIG. 4  is a plan view of grooves  260  in a spiral pattern  261  in accordance with embodiments of the present invention. In an embodiment, grooves  260 , shown in spiral pattern  261 , can be configured such that a plurality of groove angles may be implemented in the fabrication of a fixed shaft design fluid dynamic bearing, in accordance with embodiments of the present invention. Spiral pattern  261  includes a plurality of grooves  260 , and lands  262 , in accordance with embodiments of the present invention. In an embodiment of the present invention, grooves  260  may be disposed on a surface of shaft  241  of bearing system  110 . In an alternative embodiment, grooves  260  may be disposed on a surface of rotor  240  of bearing system  110   
         [0051]     Within spiral pattern  261  of grooves  260 , shown are a first and second set of groove angles. First or initial groove angle  410  is located toward an opening  405  of bearing system  110  in which grooves  260  may be implemented. Initial groove angle  410  can be, but is not limited to, approximately five degrees. Groove angle  410  can be an initial angle, shown at a continuously increasing groove angle jump point  475 , and which is continuously increased until reaching a second groove angle, groove angle  411 , shown as continuously increasing jump point  476 , in accordance with embodiments of the present invention. Groove angle  411  can be, but is not limited to, twenty degrees. Groove angle  411  can be continuously increased until reaching an apex  477  of spiral pattern  261  in accordance with embodiments of the present invention. In an embodiment, apex  477  can be, but is not limited to ninety degrees. Alternatively, groove angle  410  can be greater or smaller than five degrees, groove angle  411  can be greater or smaller than twenty degrees, and apex  477  can be greater or smaller than ninety degrees.  
         [0052]     It is noted that if the smooth bearing surface is stationary, the grooves would move from right to left. For stationary grooves, the smooth rotor would move from left to right.  
         [0053]     Still referring to  FIG. 4 , it is noted that the width of grooves  260  is narrow at the opening  405  and widen at jump point  475  and continuously widen until reaching jump point  476 . The width of grooves  260  is related to the groove angle of groove  260  dependent upon the point of reference. It is particularly noted that in an embodiment of the present invention, groove angle  410  is approximately five degrees and groove angle  411  is approximately twenty degrees.  
         [0054]     Advantageously, by implementing a groove pattern  261  having a variable groove angle, e.g., groove angles  410  and  411 , embodiments of the present invention provide with the initial groove angle, a means for a gradual building of pressure within the bearing system  110 , although a groove angle of five degrees does not provide desired rotational support of the bearing system. Therefore, embodiments of the present invention further provide a second groove angle that does provide desired rotational support of the bearing system  110  when under operation. This variable groove angle provides both a reduction in air injection/ingestion and proper rotational stability for the bearing system  110  in which grooves  260  may be implemented.  
         [0055]      FIG. 5  is a graph depicting stiffness of a bearing system  110  as it relates to the groove angle of the grooves disposed therewithin. Graph  500  is representative of bearing stiffness of a bearing system in which grooves  250  or grooves  260  can be implemented. Graph  500  includes an axis  501  representing stiffness and an axis  502  representing the groove angle. Graph  500  also includes a line  503  representing the stiffness of a bearing system, e.g., bearing system  110 , dependent upon the groove angle of a groove, e.g., groove  250  or groove  260  of FIGS.  3  or  4 , respectively. As shown, line  503  shows that the stiffness of bearing system  110  is at its softest when the groove angle is less than five degrees. As the groove angle increases, the stiffness of the bearing system  110  increases to an optimum stiffness, shown as point  505 . It is noted that point  505 , indicating optimum stiffness correlates to point  504  on axis line  502 . Point  504  represents a groove angle of approximately twenty degrees.  
         [0056]     It is noted that a groove angle far exceeding twenty degrees can detrimentally affect the function of a bearing system  110 . These detrimental affects can include, but is not limited to, increased friction, increased running torque, increased possibility of bearing seizure, and an increased tendency to draw air into the bearing.  
         [0057]     Referring collectively to  FIGS. 6A-6D , shown are various profile views of grooves that may be implemented as grooves  250  and/or grooves  260 . It is noted that the profile views shown in  FIGS. 6A-6D  are exemplary in nature and should not be construed as a limitation of the present invention.  
         [0058]      FIG. 6A  shows a rectangular shaped groove  610  in which the sidewalls of groove  610  are perpendicular to an apex  611 , in accordance with embodiments of the present invention.  
         [0059]      FIG. 6B  shows a round shaped groove  620  in which the sidewalls are also perpendicular and in which an apex  621  of groove  620  is rounded, similar to an arc, in accordance with embodiments of the present invention.  
         [0060]      FIG. 6C  shows a saw-tooth shaped groove  630  in which one sidewall is perpendicular and in which the other sidewall is tapered to meet the other sidewall at apex  622 , in accordance with embodiments of the present invention.  
         [0061]      FIG. 6D  shows a step shaped groove  640  in which the sidewalls are perpendicular to a first apex  641  and a second apex  642 , in accordance with embodiments of the present invention.  
         [0062]     It is noted that groove shapes  610 ,  620 ,  630  and/or  640  may each be implemented as grooves  250  and/or grooves  260  in accordance with embodiments of the present invention. It is further noted that many well-known techniques and methods may be implemented in the formation of groove shapes  610 ,  620 ,  630  and  640  as grooves  250  or  260 . Examples of groove shape formation can include, but is not limited to, reactive ion etching, ion milling, sputtering, coining, ECM (electro-chemical machining), ECDM (electrochemical discharge machining), ECAM (electro-chemical arc machining), powder metallurgical processes and sintering processes.  
         [0063]     Advantageously, embodiments of the present invention can substantially reduce air ingestion that may occur during operation of the bearing system in a high-performance hard disk drive. Further advantageous is that embodiments of the present invention provide this reduction while maintaining optimum bearing system performance and accordingly hard disk drive performance. Additionally advantageous is that the variable angled grooves described herein and being implemented in, for example, a fluid dynamic bearing in an enterprise type hard disk drive, is readily adaptable for application with alternative types of bearing systems as well as other products using a spindle motor in which a fixed shaft design fluid dynamic bearing in accordance with embodiments of the present invention can be implemented.  
         [0064]     The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications 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.