Abstract:
An apparatus and associated method is provided for holding an inner race of a bearing stationary with respect to rotational movement while leaving a hub that is fixed in rotation with an outer race of the bearing unencumbered. The hub is excited by contactingly engaging it with a predetermined mechanical force. The resonance response of the hub to the excitation is determined and used to characterize the bearing qualitatively.

Description:
BACKGROUND 
       [0001]    Machinery and methods employed in the manufacturing industry have been continuously shaped by a number of market and business forces. For example, many manufactured products today are relatively more complex than those in the past, as high technology electronics have proliferated and become integrated even into commonly used consumer goods. Flexibility is key to a manufacturer&#39;s survival, as smaller lot runs of products having different feature sets must be produced on the same production line. And while the functional capabilities and the number of offered features continually grows, miniaturization and portability are equally important market factors as well. Add to the mix the fact that price demands have forced a greater emphasis on manufacturing efficiency to the extent that processing station cycle time is often scrutinized to a fraction of a second. 
         [0002]    To evolve in the face of these and other factors, manufacturers must continually strive to replace manual operations with highly-complex and processor-controlled automated systems. Factory reengineering efforts must be employed to perform inspections at the component level and to permit assembling components just-in-time, instead of batch processing the components as has been done in the past. To the extent possible, product design and process capability analyses must be directed toward building quality into the process, thereby reducing if not eliminating the amount of inspection activities. 
         [0003]    Illustrative embodiments of the claimed invention are directed to the manufacture of an actuator assembly that operably supports a data transfer member adjacent a storage medium in a data storage device. The actuator assembly employs a cartridge bearing having a stationary shaft affixed to a base at one end and to a cover at the other end, the base and cover cooperatively forming an enclosure. An actuator body, sometimes referred to as an “e-block,” is affixed to an external mount of the cartridge bearing and is thereby journaled in rotation with respect to the storage medium. The rotary motion of the actuator permits selectively locating the data transfer member adjacent any of a plurality of different data storage locations across the storage medium. 
         [0004]    Static bearing characteristics, such as stiffness, are determined according to some previously attempted solutions by first assembling the actuator assembly together. That is, the body is assembled to the cartridge bearing and the body/bearing subassembly is assembled to the enclosure in order to test the bearing. The assembly time alone, which can easily take fifteen minutes to complete manually, is the critical path by far when such solutions are employed to sample bearings. The disassembly time is a harsh penalty to pay on finding a nonconformance when such solutions are employed in product assembly. What the related art solutions are lacking is a way to test static characteristics of the bearing at the component level. 
       SUMMARY 
       [0005]    Claimed embodiments are generally directed to bearing testing for qualitatively characterizing a bearing. 
         [0006]    In some embodiments an apparatus and associated method is provided for holding an inner race of a bearing stationary with respect to rotational movement while leaving a hub that is fixed in rotation with an outer race of the bearing unencumbered. The hub is excited by contactingly engaging it with a predetermined mechanical force. The resonance response of the hub to the excitation is determined and used to characterize the bearing qualitatively, such as but not limited to characterizing the bearing stiffness. 
         [0007]    These and various other features and advantages which characterize the claimed embodiments will become apparent upon reading the following detailed description and upon reviewing the associated drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is an isometric view of a data storage device that is constructed in accordance with embodiments of the present invention. 
           [0009]      FIG. 2  is an exploded isometric view of the e-block and cartridge bearing in the actuator assembly of the data storage device of  FIG. 1 . 
           [0010]      FIG. 3  is a cross sectional view of the cartridge bearing of  FIG. 2 . 
           [0011]      FIG. 4  is an isometric view of a bearing tester that is constructed in accordance with embodiments of the present invention. 
           [0012]      FIG. 5  is a partial cross sectional view of the bearing while being tested in the bearing tester of  FIG. 4 . 
           [0013]      FIG. 6  is a functional block diagram of the bearing tester of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Referring to the drawings as a whole, and for now in particular to  FIG. 1  which is an isometric view of a data storage device  100  that is constructed in accordance with embodiments of the present invention. A base  102  and a cover  104  (partially cutaway) with a sealing member interposed therebetween provide a sealed enclosure for a number of components. These components include a spindle motor  108  that has one or more data storage mediums (sometimes referred to as “discs”)  110  affixed thereto in rotation. 
         [0015]    Adjacent the disc  110  is an actuator assembly  112  that pivots by being supported by a cartridge bearing  114 . The actuator assembly  112  includes an eblock  115  having a cantilevered actuator arm  116  supporting a load arm  118  that, in turn, supports a read/write transducer (or “head”)  120  in a data transfer relationship with the adjacent disc  110 . 
         [0016]    A recording surface of the disc  110  is divided into a plurality of tracks over which the head  120  is moved. The tracks can have head position control information written to embedded servo sectors. Between the embedded servo sectors are data sectors for storing user data. The head  120  stores input data to the tracks and retrieves output data from the tracks. The output data can be previously stored user data or it can be servo data used to position-control the head  120  relative to a desired track. 
         [0017]    The actuator assembly  112  is positionally controlled by a voice coil motor (VCM)  124  that includes an actuator coil  126  immersed in a magnetic field generated by a magnet assembly  128 . A pair of steel plates  130  (pole pieces) mounted above and below the actuator coil  126  provides a magnetically permeable flux path for a magnetic circuit of the VCM  124 . During operation of the data storage device  100  current is passed through the actuator coil  126  forming an electromagnetic field, which interacts with the magnetic circuit of the VCM  124 , causing the actuator  112  to move the head  120  radially across the disc  110 . 
         [0018]    To provide the requisite electrical conduction paths between the head  120  and data storage device control circuitry, head wires of the head  120  are affixed to a flex circuit  132 . The flex circuit  132  is routed at one end from the load arms  118  along the actuator arms  116 , and is secured to a flex connector  134  at the other end. The flex connector  134  Supports the flex circuit  132  where it passes through the base  102  and into electrical communication with a printed circuit board assembly (“PCBA”)  135 , mounted to the underside of the base  102 . A preamplifier/driver (preamp)  136  conditions read/write signals passed between the control circuitry and the head  120 . 
         [0019]      FIG. 2  is a partially exploded isometric view of the eblock  115  and cartridge bearing  114  portions of the actuator assembly  112 . The eblock  115  defines a bore  140  that is sized to matingly engage an external mount  142  of the cartridge bearing  114  so that the eblock  115  and mount  142  are operably affixed together in rotation. 
         [0020]      FIG. 3  depicts a cross sectional view of the eblock  115  operably mounted to the cartridge bearing  114 . In these illustrative embodiments the cartridge bearing  114  has a shaft  144  defining an externally threaded proximal end  146  for stationary attachment to the base  102  ( FIG. 1 ), and an internally threaded distal end  148  for stationary attachment to the cover  104  ( FIG. 1 ). The stationary shaft  144  also defines an internal mount  150  that is sized to matingly engage inner races  152  of each of two bearings  154  so that the inner races  152  are operably stationary too. Outer races  156  thereby operably rotate relative to the stationary shaft  144 , with a hub  158  affixed to the outer races  156  in rotation together. As discussed, the external mount  142  (see also  FIG. 2 ) is sized to matingly engage the bore  140  in the eblock  115  so that they are operably affixed together in rotation. In this manner, the eblock  115  is pivotable around the stationary shaft  144 . 
         [0021]      FIG. 4  is an isometric view of a bearing tester  162  that is constructed in accordance with the claimed embodiments. A base  164  defines an upstanding surface  166  against which a bearing  114  under test is abuttingly fixtured. The base  164  supports a cylinder  168 , such as a fluid-cylinder, that has an extensible shaft  170  to compressingly engage the bearing  114  against the surface  166 . Alternatively, the cylinder  168  might be electrically or magnetically operated. 
         [0022]    A stanchion  172  extends upwardly from the base  164  with a pivot  174  at an upper end thereof supporting a pendulum  176  that pivots in the path of a fixtured bearing  114 . The pendulum  176  includes an impact hammer  178  of a known mass and which has an integrated accelerometer for indicating the acceleration with which the impact hammer  178  impacts against the bearing  114  during testing. 
         [0023]      FIG. 5  is a top sectional view of the bearing  114  fixtured in the bearing tester  164 . As described, the bearing  114  is compressingly engaged between the extensible shaft  170  and the upstanding surface  166 . The latter defines a protuberant feature  180  that is sized to matingly engage a counterbore portion of the internal thread feature at the distal end  148  in order to precisely locate a bearing  114  for testing. The extensible shaft  170  is annular in its cross section so as to clearingly disengage the external thread feature at the proximal end  146 . Thus, the opposing fixture members, the protuberant feature  180  of the surface  166  and the extensible shaft  170 , hold the shaft  144  and inner races  152  stationary with respect to rotational movement while leaving the hub  158  and outer races  156  unencumbered. 
         [0024]    However, the depicted embodiments for the bearing  114  and the opposing fixture members are illustrative and not limiting of the claimed embodiments. In alternative equivalent embodiments different fixture members can be provided in conjunction with different bearing  114  constructions, such as one having opposing protuberant features for a bearing  114  with an internal thread feature at both ends thereof. 
         [0025]      FIG. 5  also depicts the impact hammer  178  precisely at the moment that it impacts (or “pings”) the external mount  142  of the hub  158 . Because the mass and acceleration of the impact hammer  178  are known, the impact imparts a predetermined mechanical force that excites the hub  158 . A non-contacting motion sensing measurement device  182  is positioned radially opposite the impact hammer  178  at the point of impact to observe the resonance response of the hub  158  to the excitation. The resonance response can be used to qualitatively characterize the bearing  112  in terms of its radial stiffness. 
         [0026]      FIG. 6  is a functional block diagram depicting illustrative embodiments of the bearing tester  162  of  FIG. 4 . As discussed above, the bearing  114  is fixtured so as to hold stationary the shaft  144  with respect to rotation, while leaving the hub  158  unencumbered. The impact hammer  178  delivers a mechanical excitation of a known predetermined force in block  184 . The motion sensing measurement device, such as a laser Doppler vibrometer (“LDV”), detects the resonance response of the hub  158  to the mechanical excitation in block  186 . The output signal from the LDV is analyzed in block  188  to provide results in a useful format. In these illustrative embodiments the signal analyzer performs a Fourier transformation on the LDV signature signal to produce a mechanical bode plot showing the resonance and phase relationship of the hub  158  in response to the excitation. Measured values can be compared to a predetermined threshold constructed across all frequencies of interest in order to qualitatively characterize a bearing  114  under test. 
         [0027]    Generally, the embodiments described contemplate a bearing tester wherein a fixture operably holds an inner race of a bearing stationary with respect to rotational movement but leaves an external mount of the bearing unencumbered. The bearing tester also possesses a means for characterizing the bearing qualitatively in relation to an observed direct resonance response of the bearing to an excitation. 
         [0028]    For purposes of this description and meaning of the appended claims, the phrase “means for characterizing” expressly means the structural aspects of the embodiments disclosed herein and the structural equivalents thereof. For example, without limitation, the disclosed testing of a bearing having the structural configuration depicted in  FIG. 5  is illustrative of and not limiting of the present embodiments as claimed. For example, one may choose to test a bearing having externally threaded features or internally threaded features at both proximal and distal ends of the bearing, and incorporating appropriate fixture members to matingly engage such alternative embodiments is within the contemplated scope of the claimed embodiments. In another example, the fixture members can support the bearing longitudinally with respect to the impact hammer&#39;s path of travel in order to test a bearing&#39;s longitudinal stiffness. 
         [0029]    However, the meaning of “means for characterizing” expressly does not include previously attempted solutions that first assemble the bearing into an actuator assembly or some subassembly, or where the mechanical excitation does not contactingly engage the bearing external mount such as in bode testing performed at the HAA level or in a shaker table excitation method. 
         [0030]    It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and function of various embodiments of the invention, this detailed description is illustrative only, and changes may be made in detail, especially in matters of structure and arrangements of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. For example, the particular elements may vary in type or arrangement without departing from the spirit and scope of the present invention. 
         [0031]    In addition, although the embodiments described herein are directed to a cartridge bearing, it will be appreciated by those skilled in the art that the claimed subject matter is not so limited and various other applications can utilize the present embodiments without departing from the spirit and scope of the claimed invention.