Abstract:
A data access assembly with a load arm formed from an Mn—Cu alloy is disclosed. The load arm may be supported by and actuator arm formed from a common Mn—Cu damping alloy, which has a composition (X)Fe-(A)Mn—(B)Cu—(C)Ni. In one embodiment, X is substantially 73, A is substantially 20, B is substantially 5 and C is substantially 2, wherein A, B, C and X represent the weight percent of the respective elements in the composition.

Description:
RELATED APPLICATIONS  
       [0001]    This application claims priority to U.S. Provisional Application No. 60/415,876 filed Oct. 3, 2002, entitled ALLOY FOR IMPROVED ARM/SUSPENSION DAMPING. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates generally to the field of data storage devices, and more particularly, but not by way of limitation, to an actuator assembly with improved damping.  
         BACKGROUND  
         [0003]    Data storage devices are used for data storage in modem electronic products ranging from digital cameras to network systems. A data storage device includes a mechanical portion, which typically includes a storage medium and a movable data access mechanism, and electronics mounted to the mechanical portion. The printed circuit board assembly controls functions of the mechanical portion while providing a communication interface between the data storage device and its host.  
           [0004]    The mechanical portion of the data storage device may include a data storage disc rotated at a constant speed by a spindle motor assembly and a position controllable actuator assembly, which supports a read/write head that selectively writes data to and reads data from the disc.  
           [0005]    The data storage device market continues to place pressure on the industry for data storage devices with improved throughput performance. Reducing settle time of the head, coming on track following a seek, improves throughput performance. Minimizing actuator assembly vibration reduces settle time for improved throughput performance. As such, challenges remain and a need persists for actuator assemblies less susceptible to induced vibration.  
         SUMMARY OF THE INVENTION  
         [0006]    In accordance with one embodiment, a data storage device has a load arm formed from a Mn—Cu damping alloy. The damping alloy load arm has a composition (X)Fe-(A)Mn—(B)Cu—(C)Ni. In some embodiments, X is substantially 73, A is substantially 20, B is substantially 5 and C is substantially 2, wherein A, B, C and X represent the weight percent of the respective elements in the composition. In some embodiments, the load arm may form part of an actuator assembly in which the load arm is supported by an actuator arm which may also be formed from a similar Mn—Cu damping alloy. The actuator arm may be formed as part of an actuator E-block.  
           [0007]    Adaptation of the Mn—Cu damping alloy to the E-block and load arm of the data storage device improves performance of the data storage device by reducing the effects of vibration energy experienced by the actuator assembly, thereby promoting a more rapid settle time following a seek.  
           [0008]    These and various other features and advantages that characterize the claimed invention will be apparent upon reading the following detailed description and upon review of the associated drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a top plan view of a data storage device that incorporates an actuator assembly less susceptible to induced vibration.  
         [0010]    [0010]FIG. 2 is a functional block diagram of a circuit for controlling operation of the data storage device of FIG. 1.  
         [0011]    [0011]FIG. 3 is a top plan view of a mechanical portion of an actuator assembly of the data storage device of FIG. 1.  
         [0012]    [0012]FIG. 4 is a perspective view of the mechanical portion of the actuator assembly of the data storage device of FIG. 1.  
         [0013]    [0013]FIG. 5 is a process flow chart of a method of assembling the actuator assembly of the data storage device of FIG. 1.  
         [0014]    [0014]FIG. 6 is a partial cutaway plan view of a load arm of the actuator assembly of FIG. 3.  
         [0015]    [0015]FIG. 7 is a partial cutaway elevational view of the load arm of the actuator assembly of FIG. 6.  
     
    
     DETAILED DESCRIPTION  
       [0016]    Referring now to the drawings, FIG. 1 provides a top plan view of one embodiment of a data storage device  100  in which the principles of the present invention may be applied. This data storage device  100  includes a rigid base deck  102 , which cooperates with a top cover  104  (shown in partial cutaway) to form a sealed housing for a mechanical portion of the data storage device  100  (also referred to as disc drive  100 ). Typically, the mechanical portion of the data storage device  100  is referred to as a head-disc assembly  106 . A spindle motor  108  rotates one or more of magnetic data storage discs  110  at a constant high speed, each disc  110  having at least one recording surface  111 . A rotary actuator assembly  112  (also referred to herein as actuator  112 ) supports one or more read/write heads  114  (also referred to herein as heads  114 ) adjacent the disc(s)  110 . The actuator  112  is rotated through application of current to a voice coil  116  of a voice coil motor (VCM)  118 . The voice coil includes a lead  120  for receiving current to power the coil.  
         [0017]    During data transfer operations with a host device (not shown), the actuator  112  moves the heads  114  to data tracks  121 , one shown (also referred to as an information track  121 ) on the surfaces of the discs  110  to write data to and read data from the discs  110 . When the data storage device  100  is deactivated, the actuator  112  removes the heads  114  from the data tracks  121  to a home position  122  of the disc  110 ; the actuator  112  is then confined by latching a toggle latch  124 .  
         [0018]    Command and control electronics, as well as other interface and control circuitry for the data storage device  100 , may be provided on a printed circuit board assembly  126  mounted to the underside of the base deck  102 . A primary component for use in conditioning read/write signals passed between the command and control electronics of printed circuit board assembly  126  and the read/write head  114  is a preamplifier/driver (preamp)  128 , which prepares a read signal acquired from the information track  121  by the read/write head  114  for processing by read/write channel circuitry (not separately shown) of the printed circuit board assembly  126 . The preamp  128  is attached to a flex circuit  130  with conductors (not separately shown) conducting signals between the read/write head  114  and the preamp  128 , and between the preamp  128  and the printed circuit board assembly  126  during data transfer operations.  
         [0019]    Position-controlling of the read/write heads  114  is provided in this embodiment by the voice coil motor  118  operating under the control of a servo control circuit  132  (FIG. 2) programmed with servo control code, which collectively forms a servo control loop.  
         [0020]    Turning to FIG. 2, one contemplated embodiment of a servo control circuit  132  includes a micro-processor controller  134  (also referred to herein as controller  134 ), a memory  136 , a buffer memory  138 , a demodulator (DEMOD)  140 , an application specific integrated circuit (ASIC) hardware-based servo controller (“servo engine”)  142 , a digital to analog converter (DAC)  144  and a motor driver circuit  146 . Optionally, the controller  134 , the memory  136 , and the servo engine  142  are portions of an application specific integrated circuit  148 . The buffer memory  138  of the memory  136  is used for storage of information collected or calculated during operation of the data storage device  100 .  
         [0021]    The components of the servo control circuit  132  are utilized to facilitate track following algorithms for the actuator  112  (of FIG. 1) and more specifically for controlling the voice coil motor  118  in position-controlling the read/write head  114  relative to the selected information track  121  (of FIG. 1).  
         [0022]    The demodulator  140  conditions head position control information transduced from the information track  121  of the disc  110  to provide position information of the read/write head  114  relative to the disc  110 . The servo engine  142  generates servo control loop values used by the controller  134  in generating command signals such as seek signals used by the voice coil motor  118  in executing seek commands. Control loop values are also used to maintain a predetermined position of the actuator  112  during data transfer operations.  
         [0023]    The command signals generated by the controller  134  and passed by the servo engine  142  are converted by the digital to analog converter  144  to analog control signals. The analog control signals are used by the motor driver circuit  146  in position-controlling the read/write head  114  relative to the selected information track  121 , during track following, and relative to the surface of the disc  110  during seek functions.  
         [0024]    It should, of course, be understood that the present invention may be applicable in data storage devices other than those described above and in the attached drawings, and using a servo control system other that that described above and illustrated, without departing from the spirit of the present invention.  
         [0025]    Returning to FIG. 1, during seek operations, as well as track following operations, stability of the read/write head  114  is an important consideration for either an effective read of data from or write of data to the information tracks  121 . By having both the actuator arm  113  and a load arm  115  of the actuator assembly  112  as well as the base deck  102  and the cover  104  formed from the same material, a common coefficient of thermal expansion and frequency response is shared by the members of the actuator  112  most influencing head stability.  
         [0026]    Control of noise and vibration of material is taken into account when designing the data storage device  100 . Therefore, the development of damping materials suitable for structural parts that are easy to process and recycle is beneficial for use in the manufacture and operation of components of the head-disc assembly  106  of the data storage device  100 . From among developed damping alloys, Mn—Cu damping alloys show satisfactory mechanical properties and damping capacity to improve performance of the data storage device  100  by reducing the effects of vibration energy experienced by the head-disc assembly  106 , thereby promoting a more rapid settle time following a seek.  
         [0027]    The Mn—Cu damping alloy, which has a nominal composition of Mn-20; Cu-5; Ni-2; and Fe-balance (% weight), shows both a high damping capacity and a high strength suitable for use in producing the actuator arm  113 , the load arm  115 , as well as the base deck  102 , and the top cover  104 . The damping capacity of the Mn—Cu damping alloy increases to a high level below a certain temperature and the damping level also varies sensitively to the changes in vibration frequency and strain amplitude. By the peak-shift method the thermal activation energy for the twin boundaries responsible for the low-temperature damping peak is calculated to be 4.88×10 4  J/mol. The tensile strength of the Mn—Cu damping alloy is 500 MPa.  
         [0028]    [0028]FIG. 3 shows a bearing assembly  117  secured to an E-block  119  of the actuator  112 . In a preferred embodiment, the actuator arm  113  is a portion of the E-block  119  that supports the load arm  115 . In a preferred embodiment both the E-block  119  and the load arm  115  are formed from a common Mn—Cu damping alloy.  
         [0029]    It is noted however, an election of the E-block  119  configuration as an illustrative example of a presentation of the actuator arm  113  that incorporates a Mn—Cu damping alloy, for use in the data storage device  100  of FIG. 1, does not serve as a limitation of the present invention. Alternative configurations of actuator arms incorporating the Mn—Cu damping alloy may be selected for use in the actuator  112  of the data storage device lie within the scope of the present invention.  
         [0030]    [0030]FIG. 4 shows the E-block supporting a plurality of actuator arms  113  formed from the Mn—Cu damping alloy of the present invention. The number of actuator arms  113  incorporated in the actuator  112  of the data storage device fails to serve as a limitation of the present invention. Actuator arms presented in an E-block configuration is a convenient form for presentation of the present invention.  
         [0031]    [0031]FIG. 5 shows a process flow chart  200  for a method of assembling an actuator assembly (such as  112 ). The process commences with start step  202 . At process step  204 , a read/write head (such as  114 ) is secured to a Mn—Cu damping alloy load arm (such as  115 ). At process step  206 , the Mn—Cu damping alloy load arm, with the read/write head secured thereon, is attached to a Mn—Cu damping alloy actuator arm (such as  113 ) of an Mn—Cu damping alloy E-block (such as  119 ), and a bearing assembly (such as  117 ) is affixed to the Mn—Cu damping alloy E-block at process step  208 .  
         [0032]    At process step  210 , a flex circuit assembly (such as  130 ) with an attached preamp (such as  128 ) is fastened to the Mn—Cu damping alloy E-block and connected to the read/write head. At process step  212 , a voice coil (such as  116 ) mounted to the Mn—Cu damping alloy E-block and interconnected with the flex circuit, which concludes the process at process step  214 .  
         [0033]    [0033]FIG. 6 shows a suspension portion  150  of the load arm  115  attached to a load beam portion  152  of the load arm  115 . The suspension portion  150  communicates with the read/write head  114  (FIG. 1) to secure the read/write head  114  to the load arm  115 , while the load beam portion  152  communicates with the actuator arm  113  (FIG. 1) to secure the load arm  115  to the E-block  119  (FIG. 1).  
         [0034]    The suspension portion  150  and the load beam portion  152  are each formed from the Mn—Cu damping alloy having the compassion of Mn-20; Cu-S; Ni-2; and Fe-balance (% weight).  
         [0035]    [0035]FIG. 7 shows the suspension portion  150  of the load arm  115 , which includes a gimbal spring  154  coupled to the load beam  152 . The gimbal spring  154  flexibly supports the read/write head  114  relative to the load beam  152 . A load button  156  of the load beam  152  applies a load force to the upper surface of the read/write head  114  and defines a gimbal pivot axis about which the read/write head  114  can pitch, and a pivot axis about which the read/write head can roll, relative to the recording surface  111  of the disc  110  of FIG. 1.  
         [0036]    Accordingly, embodiments of the present invention are generally directed to an actuator assembly (such as  112 ) of a data storage device (such as  100 ), wherein a load arm (such as  115 ) of the actuator assembly is a Mn—Cu damping alloy load arm, and wherein the Mn—Cu damping alloy load arm is supported by a Mn—Cu damping alloy actuator arm (such as  113 ).  
         [0037]    In a preferred embodiment, the Mn—Cu damping alloy actuator arm is a portion of an E-block (such as  119 ) in which the E-block is formed from a Mn—Cu damping alloy.  
         [0038]    For purposes of the appended claims, it will be understood that the disclosed method corresponding to the recited steps for element includes the steps shown by the flow chart shown in FIG. 5.  
         [0039]    It will be clear that the present invention is well adapted to attain the ends and advantages mentioned as well as those inherent therein. While presently preferred embodiments have been described for purposes of this disclosure, numerous changes may be made which will readily suggest themselves to those skilled in the art and which are encompassed in the appended claims.