Abstract:
A method of lubricating a bearing for an actuator pivot of a storage device, the method including receiving an assembled bearing for an actuator pivot of a storage device, applying a volume of soap-free oil onto a bearing component of the assembled bearing, and dispensing a predetermined volume of soap-containing grease into a bearing cage.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. provisional application No. 61/857,476, filed Jul. 23, 2013, the disclosure of which is hereby incorporated by reference. 
    
    
     FIELD 
     The present disclosure relates generally to data storage devices and in particular, to a method of lubricating bearings of an actuator pivot in a data storage device by applying oil to the raceways prior to exercising the bearing. 
     BACKGROUND 
     Information storage devices are used to retrieve and/or store data in computers and other consumer electronics devices. A magnetic hard disk drive is an example of an information storage device that includes one or more heads that can both read and write, but other information storage devices also include heads—sometimes including heads that cannot write. For convenience, all heads that can read are referred to as “read heads” herein, regardless of other devices and functions the read head may also perform (e.g. writing, flying height control, touch down detection, lapping control, etc.). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A general architecture that implements the various features of the disclosure will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate implementations of the disclosure and not to limit the scope of the disclosure. Throughout the drawings, reference numbers are reused to indicate correspondence between referenced elements. 
         FIG. 1  a top perspective view of a disk drive capable of being assembled using one or more implementations of the present application. 
         FIG. 2  is a top perspective view of a head actuator capable of being assembled using one or more implementations of the present application. 
         FIGS. 3A and 3B  are a cut-away perspective views of an actuator pivot bearing capable of being assembled using one or more implementations of the present application. 
         FIG. 4  is a flow chart illustrating an example embodiment of a method for lubricating an actuator pivot bearing according to an implementation of the present application. 
         FIG. 5  is a flow chart illustrating another example embodiment of a method for lubricating an actuator pivot bearing according to an implementation of the present application. 
         FIG. 6  is a flow chart illustrating another example embodiment of a method for lubricating an actuator pivot bearing according to an implementation of the present application. 
         FIG. 7  is a flow chart illustrating another example embodiment of a method for lubricating an actuator pivot bearing according to an implementation of the present application. 
     
    
    
     DETAILED DESCRIPTION 
     In a modern magnetic hard disk drive device, each read head is a sub-component of a head gimbal assembly (HGA), which is discussed in greater detail below with reference to an example embodiment. The HGA, in turn, is a sub-component of a head stack assembly (HSA) that typically includes a plurality of HGAs, a head actuator, and a flex cable. 
     The head actuator of the HSA is pivotally attached to a base of the disk drive, for example by an actuator pivot bearing cartridge that allows the HSA to pivot. The relative position of other disk drive components limits such pivoting to a limited angular range. The actuator pivot bearing cartridge typically includes a lubricant such as grease. Currently actuator pivot bearings are assembled dry. Once bearing assembly is completed, grease is added to pockets in the bearing cage. This grease typically includes two components: (1) oil, and (2) an oil “carrier” which is frequently referred to as thickener, urea, or soap. In some implementations, the soap is required to hold the oil in place in the bearing cage until it is needed. The bearing is then spun or rotated to distribute the oil, from the grease, across the balls and the raceways of the bearing. This process pulls oil from the initial grease volume. The oil from the grease inherently includes some of the grease soap. 
     This process may create several challenges. The first challenge is that of the pivot life of bearings which don&#39;t have the physical space to add the desired amount of grease. Specifically, with the development of very thin drives, the bearing profile has been decreased substantially. This directly impacts the capacity of the grease that can be physically included in the acceptable areas of a bearing. As volume of grease in the bearings may be decreased pivot bearing, and consequently, drive life may be impacted. 
     A second challenge with this process is the possibility of bearing torque disturbances. Disk drive actuator pivot bearings are often used in an oscillating application while, the large majority of all other ball bearing applications are primarily rotational applications. A phenomenon that has been discovered in these oscillating applications, which is not observed in a rotational application, is the development of what is referred to as a “grease bump” (GB). These GBs may result from a concentration of the grease soap in the bearing raceway which builds up over time at the edges of the seek zone of the actuator range. 
     In view of these changes, implementations of the present application may provide a method for charging or lubricating the bearings of a pivot assembly. 
       FIG. 1  provides a top perspective view of a disk drive  100  capable of being assembled using one or more implementations of the present application, with the disk drive cover removed to enable viewing of certain internal disk drive components. The disk drive  100  includes a disk drive base  102 . The disk drive  100  further includes a spindle  106 , rotatably mounted on the disk drive base  102 , for rotating at least one disk  104  that is mounted on the spindle  106 . In certain embodiments, disk drive  100  may have only a single disk  104 , or alternatively, two or more disks. The rotation of the disk(s)  104  establishes air flow through an optional recirculation filter  108 . The disk drive  100  may optionally also include an adsorbent filter  130  for helping to remove contaminants from the internal atmosphere within the disk drive, if and after such contaminants have entered the internal atmosphere within the disk drive. 
     In the embodiment of  FIG. 1 , the disk drive  100  further includes a head actuator  110  that is pivotably mounted on disk drive base  102  by an actuator pivot bearing  120 . The head actuator  110  includes a plurality of actuator arms (e.g. actuator arm  114 ), each supporting a head gimbal assembly (e.g. HGA  118 ). For example, the HGA  118  may be attached to a distal end of the actuator arm  114  by the well-known conventional attachment process known as swaging. Preferably the disk drive  100  will include one HGA  118  per disk surface, but depopulated disk drives are also contemplated in which fewer HGAs are used. In  FIG. 1 , the HGAs  118  is shown demerged from the disk  104 , so that the disks do not obscure the HGAs from view. In such position, the HGAs would be supported by a conventional head loading ramp (not shown in  FIG. 1  so that the view of the HGAs will not be obstructed). 
     The distal end of the HGA  118  includes a conventional read head (too small to be seen in the view of  FIG. 1 ) for reading and writing data from and to a magnetic disk (e.g. disk  104 ). The read head may optionally include a ceramic slider substrate and a read/write transducer that may be an inductive magnetic write transducer merged with a magneto-resistive read transducer (e.g. a tunneling magneto-resistive read transducer). Note: Any head that includes a read transducer is referred to as a “read head” herein, even if the head also includes other structures for performing other functions (e.g. writer, microactuator, heater, lapping guide, etc.). Note also that in certain optical disk drives, it is possible for a read head to include an objective lens rather than a read transducer. 
     Also in the embodiment of  FIG. 1 , a magnet  112  may provide a magnetic field for a voice coil motor to pivot the head actuator  110  about the actuator pivot bearing  120  through a limited angular range, so that the read head of HGA  118  may be desirably positioned relative to one or more tracks of information on the disk  104 . 
       FIG. 2  is a top perspective view of a head actuator  200  capable of being assembled using one or more implementations of the present application. The head actuator  200  includes an actuator body  210 . In the embodiment of  FIG. 2 , actuator arms  230 ,  232 ,  236  extend from the actuator body  210  in a first direction, while a voice coil support  212  and a voice coil  204  extend from the actuator body  210  in a second direction that is approximately opposite the first direction. An electrical current driven through the voice coil  204  may interact with a magnetic field from a permanent magnet within the disk drive (e.g. magnet  112  of  FIG. 1 ), to create a torque to pivot and control the angular position of the head actuator  200 . 
     In the embodiment of  FIG. 2 , the actuator arms  230 ,  232 ,  236  support head gimbal assemblies (HGAs)  240 ,  242 ,  244 ,  246 . Specifically, the actuator arm  230  supports the HGA  240 , the actuator arm  232  supports the HGAs  242  and  244 , and the actuator arm  236  supports the HGA  246 . In the embodiment of  FIG. 2 , each of the HGAs  240 ,  242 ,  244 , and  246 , in turn, supports a read head. For example, the HGA  246  includes a flexure  270  that supports a read head  280  and that includes conductive traces to facilitate electrical connection to the read head  280 . A terminal region  278  of the flexure  270  may be electrically connected to a flex cable  260 , which runs to an external connector, and upon which a pre-amplifier chip  262  may optionally be mounted. 
     In the embodiment of  FIG. 2 , the actuator body  210  includes a bore  214  therein, and an actuator pivot bearing  220  disposed at least partially within the bore  214 . As will be described in more detail later in this specification, the actuator pivot bearing  220  may include an inner shaft that is fixed to the disk drive base (e.g. disk drive base  102  of  FIG. 1 ), and a rotatable outer portion that may be attached to the actuator body  210 . For example, in certain embodiments, the actuator pivot bearing  220  may include a rotatable outer sleeve that is press-fit into the bore  214  of the actuator body  210 , and/or held in place within the bore  214  of the actuator body  210  by a conventional tolerance ring. Alternatively, the actuator pivot bearing  220  may be held within the bore  214  of the actuator body  210  by a conventional C-clip. Alternatively, the actuator pivot bearing  220  may instead have rotatable outer bearing races that are directly bonded to an inner surface of the bore  214  in the actuator body  210 , for example, by a conventional adhesive. 
       FIG. 3A  is a cut-away perspective view of an actuator pivot bearing  300  capable of being assembled using one or more implementations of the present application.  FIG. 3B  also depicts the actuator pivot bearing  300 , except with certain sub-components partially rotated (after the cut-away) for better visibility. Now referring to  FIGS. 3A and 3B , the actuator pivot bearing  300  includes a fixed inner bearing shaft  302 , and a bearing cap  310  attached to an upper portion  304  of the fixed inner bearing shaft  302 . A lower portion  306  of the fixed inner bearing shaft  302  has a bottom flange  320 . In this context and as shown in  FIGS. 3A and 3B , a “flange” is a location of substantially increased diameter along the fixed inner bearing shaft  302 . 
     In the embodiment of  FIGS. 3A and 3B , the actuator pivot bearing  300  also includes an upper ball bearing  350 , which includes an upper bearing inner race  352  and an upper bearing outer race  354 . Also in the embodiment of  FIGS. 3A and 3B , the actuator pivot bearing  300  includes a lower ball bearing  360 , which has a lower bearing inner race  362  and a lower bearing outer race  364 . In the embodiment of  FIGS. 3A and 3B , a lubricant wets at least one surface of the upper ball bearing  350  and/or the lower ball bearing  360 . For example, oil and/or grease may wet the surface of the upper bearing inner race  352 , the upper bearing outer race  354 , the lower bearing inner race  362 , and/or the lower bearing outer race  364 . 
     In the present context, a lubricant is said to “wet” a surface if adhesive forces between the lubricant and the surface (which encourage the lubricant to spread across the surface) exceed cohesive forces within the lubricant (which encourage the lubricant to ball up and therefore avoid increased contact with the surface at the lubricant&#39;s edges). However, if the cohesive forces are stronger than the adhesive forces, then the lubricant is said to not wet the surface. 
     Now referring again to  FIGS. 3A and 3B , an upper surface  322  of the bottom flange  320  of the lower portion  306  of the fixed inner bearing shaft  302  is shown to face the upper ball bearing  350  and/or the lower ball bearing  360  and therefore faces the lubricant that wets one or more surfaces of the upper ball bearing  350  and/or the lower ball bearing  360 . Also in the embodiment of  FIGS. 3A and 3B , the bearing cap  310  has an underside  312  and an outer surface  314 . The underside  312  of the bearing cap  310  is shown in  FIGS. 3A and 3B  to face the upper ball bearing  350  and/or the lower ball bearing  360  and therefore faces the lubricant that wets one or more surfaces of the upper ball bearing  350  and/or the lower ball bearing  360 . 
     In the embodiment of  FIGS. 3A and 3B , the actuator pivot bearing  300  optionally includes a rotatable outer bearing sleeve  340  fixed to the actuator body (e.g. actuator body  210  of  FIG. 2 ) so that the actuator pivot bearing  300  may be considered as an actuator pivot bearing “cartridge.” In the embodiment of  FIGS. 3A and 3B , the actuator pivot bearing cartridge  300  has an internal cartridge space  342  that is bounded by an inner surface  344  of the rotatable outer bearing sleeve  340 , the underside  312  of the bearing cap  310 , and the upper surface  322  of the bottom flange  320 . Note that the inner surface  344  of the rotatable outer bearing sleeve  340  is shown in  FIGS. 3A and 3B  to face the internal cartridge space  342 . The upper ball bearing  350  and the lower ball bearing  360  are disposed within the internal cartridge space  342 , and hence the lubricant is also disposed within the internal cartridge space  342 . Additionally, a grease cage or grease retaining element  370  may be provided within the internal cartridge space  342  to hold the grease. 
       FIG. 4  illustrates an example embodiment of a method for lubricating an actuator pivot bearing, such as the actuator pivot bearing  300  discussed above, according to an implementation of the present application. At  405  of  FIG. 4 , the actuator pivot bearing is dry assembled using conventional techniques. The assembly of the pivot bearing may be performed using automatic or computer controlled manufacturing techniques or may be performed using manual or human controlled manufacturing techniques. Once the actuator pivot bearing is dry assembled in  405 , pure oil or soap-free oil (i.e. oil without any soap) is applied to one or more components of the pivot bearing in  410 . 
     For example, soap-free or soap-less oil may be applied to the raceways and/or ball bearings  350 ,  360  of the pivot bearings  300 . In some implementations, the application of pure oil or soap-free oil may be performed by submerging bearing components in the pure or soap-free oil. In some implementations, the application of pure or soap-free oil may be performed by providing the pure or soap-free oil to the components directly. In some implementations, the application of pure or soap-free oil is applied using one or more computer assisted applicators to provide precise control of application location and application volume. Additionally, in some implementations, the pure or soap-free oil is applied using a manual applicator. 
     Once the pure or soap-free oil has been applied to the bearing components such as the raceways and/or ball bearings  350 ,  360 , the bearing is exercised or spun to distribute the pure or soap-free oil within the actuator pivot bearing  300  in  415 . In some implementations the bearing may be exercised by being rotated in one direction through an entire range of motion. In some implementations the bearing may be rotated through more or less than an entire range of motion. In some implementations, the bearing may be exercised by rotating the bearing in one direction and in some implementations the bearing may be exercised by rotating the bearing back and forth in two or more directions in an oscillating manner. In some implementations, the bearing may be exercised using a computer-controlled or automated apparatus. In some implementations, the bearing may be manually exercised by a person with or without the use of an apparatus. Once the actuator pivot bearing has been exercised and the pure or soap-free oil distributed in  415 , grease may be added to pockets in the bearing cage or grease retainer  370  in  420 . 
     In some implementations, initially “wetting” bearing surfaces with pure or soap-free oil, and then exercising the bearing, may allow the oil in the grease to stay within the grease in the bearing cage or grease retainer  370  until it is needed which may increase retention of the grease in the desired pockets of the bearing cage or grease retainer until necessary. The above process of lubricating an actuator pivot bearing is merely provided as an example implementation and alternative implementations are discussed below. 
       FIG. 5  illustrates another example embodiment of a method for lubricating an actuator pivot bearing, such as the actuator pivot bearing  300  discussed above, according to an implementation of the present application. Referring to  FIG. 5 , the pure oil or soap-free oil (i.e. oil without any soap) is applied to one or more components of an unassembled pivot bearing  300  in  505 . 
     For example, soap-free or soap-less oil may be applied to the raceways and/or ball bearings  350 ,  360  of the pivot bearings  300 . In some implementations, the application of pure oil or soap-free oil may be performed by submerging bearing components in the pure or soap-free oil. In some implementations, the application of pure or soap-free oil may be performed by providing the pure or soap-free oil to the components directly. In some implementations, the application of pure or soap-free oil is applied using one or more computer assisted applicators to provide precise control of application location and application volume. Additionally, in some implementations, the pure or soap-free oil may be applied to the ball bearings manually. 
     Once the pure or soap-free oil has been applied to the bearing components such as the raceways and/or ball bearings  350 ,  360 , the actuator pivot bearing is assembled using conventional techniques in  510 . The assembly of the pivot bearing may be performed using automatic or computer controlled manufacturing techniques or may be performed using manual or human controlled manufacturing techniques. 
     Once the actuator pivot bearing is assembled in  510 , the bearing is exercised or spun to distribute the pure or soap-free oil within the actuator pivot bearing  300  in  515  and grease may be added to pockets in the bearing cage or grease retainer  370  in  520 .  515  and  520  may be performed in substantially the same fashion as described above with respect to  415  and  420 . 
       FIG. 6  illustrates an example embodiment of a method for lubricating an actuator pivot bearing, such as the actuator pivot bearing  300  discussed above, according to an implementation of the present application. Referring to  FIG. 6 , the actuator pivot bearing is dry assembled using conventional techniques in  605 . The assembly of the pivot bearing may be performed using automatic or computer controlled manufacturing techniques or may be performed using manual or human controlled manufacturing techniques. Once the actuator pivot bearing  300  is dry assembled in  605 , grease may be added to pockets in the bearing cage or grease retainer  370  in  610 . 
     Once the grease has been added to the pockets in the bearing cage or grease retainer  370  in  610 , pure oil or soap-free oil (i.e. oil without any soap) is applied to one or more components of the pivot bearing in  615 . For example, soap-free or soap-less oil may be applied to the raceways and/or ball bearings  350 ,  360  of the pivot bearings  300 . In some implementations, the application of pure oil or soap-free oil may be performed by submerging bearing components in the pure or soap-free oil. In some implementations, the application of pure or soap-free oil may be performed by providing the pure or soap-free oil to the components directly. In some implementations, the application of pure or soap-free oil is applied using one or more computer assisted applicators to provide precise control of application location and application volume. Additionally, in some implementations, the pure or soap-free oil is applied using a manual applicator. 
     Once the pure or soap-free oil has been applied to the bearing components, such as the raceways and/or ball bearings  350 ,  360 , the bearing is exercised or spun to distribute the pure or soap-free oil within the actuator pivot bearing  300  in  620 . In some implementations the bearing may be exercised by being rotated in one direction through an entire range of motion. In some implementations, the bearing may be rotated through more or less than an entire range of motion. In some implementations, the bearing may be exercised by rotating the bearing in one direction and in some implementations the bearing may be exercised by rotating the bearing back and forth in two or more directions in an oscillating manner. In some implementations, the bearing may be exercised using a computer-controlled or automated apparatus. In some implementations, the bearing may be manually exercised by a person with or without the use of an apparatus. 
     Again, initially “wetting” bearing surfaces with pure or soap-free oil, and then exercising the bearing, may allow the oil in the grease to stay within the grease in the bearing cage or grease retainer  370  until it is needed which may increase retention of the grease in desired pockets until necessary. The above process of lubricating an actuator pivot bearing is merely provided as an example implementation and alternative implementations are discussed below. 
       FIG. 7  illustrates another example embodiment of a method for lubricating an actuator pivot bearing, such as the actuator pivot bearing  300  discussed above, according to an implementation of the present application. Referring to  FIG. 7 , grease may be added to pockets in the bearing cage or grease retainer  370  of an unassembled bearing  300  in  705 . 
     Once the grease is added to the bearing cage or grease retainer  370  of the unassembled bearing  300  in  705 , the actuator pivot bearing is assembled using conventional techniques in  710 . The assembly of the pivot bearing may be performed using automatic or computer controlled manufacturing techniques or may be performed using manual or human controlled manufacturing techniques 
     Once the actuator pivot bearing is assembled in  710 , pure oil or soap-free oil (i.e. oil without any soap) is applied to one or more components of the pivot bearing in  715 . For example, soap-free or soap-less oil may be applied to the raceways and/or ball bearings  350 ,  360  of the pivot bearings  300 . In some implementations, the application of pure oil or soap-free oil may be performed by submerging bearing components in the pure or soap-free oil. In some implementations, the application of pure or soap-free oil may be performed by providing the pure or soap-free oil to the components directly. In some implementations, the application of pure or soap-free oil is applied using one or more computer assisted applicators to provide precise control of application location and application volume. Additionally, in some implementations, the pure or soap-free oil is applied using a manual applicator. 
     Once the pure or soap-free oil has been applied to the bearing components, such as the raceways and/or ball bearings  350 ,  360 , the bearing is exercised or spun to distribute the pure or soap-free oil within the actuator pivot bearing  300  in  720 .  720  may be performed in substantially the same fashion as described above with respect to  620 . 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the protection. Indeed, the novel methods and apparatuses described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the protection.