Abstract:
A mounting interface for a spindle motor allows the optimization of the spindle dynamics. The mounting interface provides a steadfast relationship between a motor and a baseplate, wherein the mounting interface includes at least three surface points forming a single plane acting as a common boundary between the motor and the baseplate. The three surface points may be pads, and the pads may be coupled to the baseplate or to the mount flange. The three surface points provide reduced contact area between the mount flange and the baseplate, and the reduced contact area lowers the rigidity of the mount flange and the resonant frequencies. The surface area of the pads and the material of the pads is chosen to reduce acoustical noise. In addition, a damping ring may be provided for dissipating distortion energy between the motor, baseplate and/or mount flange.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates in general to a spindle motors for disk drives, and more particularly to a mounting interface for a spindle motor. 
     2. Description of Related Art 
     Disk drive data storage devices are a popular medium for storing digital data. Disk drive data storage devices typically include at least one rotating disk, wherein digital data are written to and read from a thin layer of magnetizable material on the surface of the rotating disks. Write and read operations are performed through a transducer which is carried in a slider body. The slider and transducer are sometimes collectively referred to as a head, and typically a single head is associated with each disk surface. The heads are selectively moved under the control of electronic circuitry to any one of a plurality of circular, concentric data tracks on the disk surface by an actuator device. Each slider body includes a self-acting hydrodynamic air bearing surface. As the disk rotates, the disk drags air beneath the air bearing surface, which develops a lifting force that causes the slider to lift and fly several micro-inches above the disk surface. 
     In the current generation of disk drive products, the most commonly used type of actuator is a rotary moving coil actuator. The disks themselves are typically mounted in a “stack” on the hub structure of a brushless DC spindle motor. The rotational speed of the spindle motor is precisely controlled by motor drive circuitry which controls both the timing and the power of commutation signals directed to the stator windings of the motor. 
     More recently, personal computers have become more popular and are commonly located within the work space of the system user. This has prompted an increase in awareness of acoustic noise generated by the disk drives located within the personal computers. In certain markets, the amount of acoustic noise allowable in the work place is closely regulated. Accordingly, it has become common for system manufacturers to impose a “noise budget” on manufacturers of major system components, such as disk drives, which limits the amount of acoustic noise that such components can contribute to the overall noise of the system. 
     One of the principal sources of noise in disk drive data storage devices is the spindle motor which drives the disks at a constant speed. Typical spindle motor speeds have been in the range of 3600 RPM. Current technology has increased spindle motor speeds to 4800 RPM, 7200 RPM and above. Analysis of various types of disk drives has brought to light several different modes of acoustic noise generation which are attributable to the spindle motor and its control logic. 
     One mode of noise generation is sympathetic vibration of the disk drive housing in response to the rotating mass of the spindle motor. Another mode of acoustic noise generation is electromagnetic disturbances caused by the excitation of the stator mass by the application and removal of the commutation pulses that are used to drive the motor and control its speed. The commutation pulses are time, polarization-selected DC current pulses which are directed to sequentially selected stator windings. The rapid rise and fall times of these pulses act as a striking force and set up sympathetic vibrations in the stator structure. 
     Prior art attempts to reduce or eliminate noise include controlling the resonant frequency and damping vibrations. For example, in U.S. Pat. No. 5,376,850, acoustic noise is reduced by uncoupling the stator from hard contact with the stationary portion of the shaft. A plurality of O-rings interposed radially between the stator and the shaft of the spindle motor. Also, a non-metallic washer is positioned at one end of the shaft and an axial O-ring is positioned at the other end of the shaft. 
     Other attempts have been directed at shifting resonant frequencies. For example, in U.S. Pat. No. 5,625,511, the spindle motor shaft is formed with stepped surfaces to reduce disk drive acoustic noise by tuning the torsional frequency of the spindle motor shaft away from the driving frequency of the motor. 
     The above prior art is directed to solving the problems originating from only one type of vibration mode. However, other types of vibration modes may cause undesirable drive dynamics, e.g., track misregistration and vibro-acoustic disturbances. Elastic vibration of the mount flange and/or the baseplate in a disk drive can cause these types of undesirable drive dynamics. 
     Yet another problem involves the mounting of the spindle motor and the drive baseplate. Often there are deformities on the baseplate or the motor mount that can affect the stability of the baseplate/mount, which can thereby also contribute to undesirable drive dynamics. 
     It can be seen that there is a need for a method and apparatus that allows the optimization of the drive dynamics. 
     It can also be seen that there is a need for a mounting interface between the baseplate and the motor mount that stabilizes the baseplate/mount. 
     It can also be seen that there is a need for a method and apparatus for dissipating distortion energy emanating from the vibration modes for the disk drive motor. 
     SUMMARY OF THE INVENTION 
     To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a mounting interface for a spindle motor. 
     The present invention solves the above-described problems by providing a method and apparatus that allows the optimization of the spindle dynamics. The mounting interface is disposed between the baseplate and the motor mount and stabilizes the baseplate/mount. 
     A system in accordance with the principles of the present invention includes a mounting interface for providing a steadfast relationship between a motor and a baseplate, wherein the mounting interface includes at least three surface points forming a single plane acting as a common boundary between the motor and the baseplate. 
     Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the at least three surface points further includes pads. 
     Another aspect of the present invention is that the at least three surface points are coupled to the baseplate. 
     Another aspect of the present invention is that the motor includes a mount flange, wherein the at least three surface points are coupled to the mount flange. 
     Another aspect of the present invention is that the at least three surface points provide reduced contact area between the mount flange and the baseplate, the reduced contact area lowering the rigidity of the mount flange and the resonant frequencies. 
     Another aspect of the present invention is that the at least three surface points have a surface area, the surface area being chosen to reduce acoustical noise. 
     Another aspect of the present invention is that the at least three surface points are formed using a predetermined material, the predetermined material being chosen to reduce acoustical noise. 
     Another aspect of the present invention is that a damping ring is provided for dissipating distortion energy between the motor, baseplate and/or mount flange. 
     These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the drawings in which like reference numbers represent corresponding parts throughout: 
         FIG. 1  shows a schematic diagram of a data storage system suitable for practicing the present invention; 
         FIG. 2  shows top view of system of  FIG. 1 ; 
         FIG. 3  illustrates the spindle motor sitting in the baseplate; 
         FIG. 4  a mount flange according to the prior art; 
         FIG. 5  illustrates a mount flange that includes the mounting interface according to the present invention; 
         FIG. 6  illustrates a view looking down at a portion the baseplate having a mounting interface according to the present invention; 
         FIG. 7  illustrates one embodiment of the mounting interface wherein the mounting interface includes a mount pad formed integral with the baseplate; 
         FIG. 8  illustrates an alternative embodiment of the mounting interface wherein the mounting interface includes a mount pad formed integral with the baseplate; 
         FIG. 9  illustrates a damping ring coupled to the mount flange according to the present invention; 
         FIG. 10  illustrates a second embodiment of a damping ring coupled to a mount flange according to the present invention; 
         FIG. 11  illustrates a third embodiment of a damping ring coupled to the baseplate according to the present invention; 
         FIG. 12  illustrates a fourth embodiment of a damping ring coupled to the baseplate according to the present invention; 
         FIG. 13  illustrates a fifth embodiment of a damping ring coupled to the mount flange according to the present invention; and 
         FIG. 14  illustrates a sixth embodiment of a damping ring coupled to the baseplate according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description of the exemplary embodiment, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration the specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized as structural changes may be made without departing from the scope of the present invention. 
     The present invention provides a mounting interface between a disk drive spindle motor and the drive baseplate which enables optimization of spindle dynamics. This is achieved by providing a means to shift resonant frequencies to a desired location and by providing a more repeatable boundary condition for the spindle motor. A damping ring may be used for dissipating distortion energy between the motor, baseplate and/or mount flange. 
       FIG. 1  shows a schematic diagram of a data storage system  10  suitable for practicing the present invention. System  10  includes a plurality of magnetic recording disks  12 . Each disk has a plurality of concentric data tracks. Disks  12  are mounted on a spindle motor shaft  14  which is connected to a spindle motor  16 . Motor  16  is mounted to a chassis  18 . The disks  12 , spindle  14 , and motor  16  include a disk stack assembly  20 . 
     A plurality of sliders  30  having read/write heads are positioned over the disks  12  such that each surface of the disks  12  has a corresponding slider  30 . Each slider  30  is attached to one of the plurality of suspensions  32  which in turn are attached to a plurality of actuator arms  34 . Arms  34  are connected to a rotary actuator  36 . Alternatively, the arms  34  may be an integral part of a rotary actuator comb. Actuator  36  moves the heads in a radial direction across disks  12 . Actuator  36  typically includes a rotating member  38  mounted to a rotating bearing  40 , a motor winding  42  and motor magnets  44 . Actuator  36  is also mounted to chassis  18 . Although a rotary actuator is shown in the preferred embodiment, a linear actuator could also be used. The sliders  30 , suspensions  32 , arms  34 , and actuator  36  include an actuator assembly  46 . The disk stack assembly  20  and the actuator assembly  46  are sealed in an enclosure  48  (shown by dashed line) which provides protection from particulate contamination. 
     A controller unit  50  provides overall control to system  10 . Controller unit  50  typically contains a central a processing unit (CPU), memory unit and other digital circuitry. Controller  50  is connected to an actuator control/drive unit  56  which in turn is connected to actuator  36 . This allows controller  50  to control the movement of sliders  30  over disks  12 . The controller  50  is a connected to a read/write channel  58  which in turn is connected to the heads of the sliders  30 . This allows controller  50  to send and receive data from the disks  12 . Controller  50  is connected to a spindle control/drive unit  60  which in turn is connected to spindle motor  16 . This allows controller  50  to control the rotation of disks  12 . A host system  70 , which is typically a computer system, is connected to the controller unit  50 . System  70  may send digital data to controller  50  to be stored on disks  12 , or may request that digital data be read from disks  12  and sent to the system  70 . The basic operation of DASD units is well known in the art and is described in more detail in Magnetic Recording Handbook, C. Dennis Mee and Eric D. Daniel, McGraw Hill Book Company, 1990. 
       FIG. 2  shows a top view of system  10 . A loading ramp member  80  is located at the edge of the disk stack assembly  20 . Member  80  automatically unloads the sliders  30  from the disks  12  as actuator  36  moves the sliders  30  to the outer disk position. To unload a slider or head means to move it a vertical distance away from its corresponding disk surface. The ramp  80  is optional. Alternatively, the sliders  30  may be placed permanently in the loaded position between the disks. 
       FIG. 3  illustrates the spindle motor sitting in the baseplate  300 . In  FIG. 3 , the motor  310  includes a mount flange  312  for interfacing with the baseplate  320 . A mounting interface  330  is provided between the baseplate  320  and the motor mount flange  312  for stabilizing the baseplate/mount. As shown in  FIG. 3 , the mounting interface  330  includes mount pads  332  that are coupled or made integral with the mount flange  312 . Those skilled in the art will recognize that the mounting interface  330  may instead be coupled or made integral with the baseplate  320 . Hereinafter, the term “coupled” as used with respect to the mounting interface  330  to the mount flange  312  or to the baseplate  320  will be understood to refer generically to both a joining together of the mount interface  330  to the mount flange  312  or to the baseplate  320 , or to the mounting interface  330  being formed as a constituent portion of the baseplate  320  or mount flange  312 . 
     Geometrically, three points define a plane. In the case of the mount interface  330 , any surface off of the plane, i.e., due to manufacturing tolerances, will result in a variation of the interface condition which could affect the dynamic performance of the spindle. The mounting interface  330  therefore provides a stable mount between the mount flange  312  and the baseplate  320 . Further, although the mounting interface  330  in  FIG. 3  is illustrated as being a pad  332 , those skilled in the art will recognize from the above discussion that the mounting interface  330  may include any structure providing three surface points defining a plane. 
       FIG. 4  illustrates a mount flange  400  according to the prior art. The mount flange  400  of  FIG. 4  engages the baseplate so that the mount flange  400  contacts the baseplate over a 360 degree annular surface. Thus, any contaminant bump or flatness problem on the baseplate or motor mount flange  400  surface affects the interface condition at the mount surface  410  when a mount flange  400  contacts the surface area of the baseplate. 
       FIG. 5  illustrates a mount flange  500  that includes the mounting interface  510  according to the present invention. As illustrated in  FIG. 5 , the mounting interface  510  includes three mount pads  512 ,  514 ,  516  that provide the interface to the drive baseplate. The reduced interface contact area provided by the three pads  512 ,  514 ,  516  changes the spindle motor boundary conditions to lower the dynamic rigidity of the mount flange  500 . This results in lower resonant frequencies for troublesome vibration modes. By shifting the resonant frequency in this manner, interaction between resonant frequency and excitation frequency of the motor can be avoided to improve acoustics and track follow performance. The three mount pads  512 ,  514 ,  516  provide a frequency reduction of approximately 80 Hz. However, those skilled in the art will recognize that the invention is not meant to be limited to the particular embodiment shown in  FIG. 5 , but that the size of the mount pads  512 ,  514 ,  516  and the material selected for the mount pads  512 ,  514 ,  516  are parameters that allow optimization of the desired frequency shift. 
     In addition, the three mount pads  512 ,  514 ,  516  provide a more consistent mount interface. As discussed above, any contaminant bump or flatness problem on the baseplate or motor mount surface affects the interface condition when a mount flange  500  contacts the baseplate over a large surface area  410 . For example, the spindle design  400  shown in  FIG. 4  may contact the baseplate over a 360 degree annular surface. However, the three pads  512 ,  514 ,  516  of the mount flange  500  shown in  FIG. 5  significantly reduces the likelihood of this problem. 
       FIG. 6  illustrates a view looking down at a portion the baseplate  600  having a mounting interface  602  according to the present invention. In  FIG. 6 , the baseplate  600  has an angular ring  610  where the motor mount flange (not shown) may be seated. The mounting interface of  FIG. 6  includes three pads  620 ,  622 ,  624  that are coupled or made integral with the baseplate  600 . Again, the reduced interface contact area provided by the three pads  620 ,  622 ,  624  changes the spindle motor boundary conditions to lower the dynamic rigidity of the mount flange. This results in lower resonant frequencies for troublesome vibration modes. However, those skilled in the art will recognize that the mounting interface  602  may include any structure providing three points defining a plane as described above. 
       FIG. 7  illustrates one embodiment  700  of the mounting interface  710  wherein the mounting interface  710  includes a mount pad  720  formed integral with the baseplate  730 . The baseplate  730  is cast according to a predetermined design specification, and then the pad  720  is formed by machining three surfaces  740 ,  742 ,  744  of the baseplate  700 . The pad  720  is formed with a generally rectangular shape. However, those skilled in the art will recognize that the invention is not meant to be limited to the geometry illustrated in  FIG. 7 , but that other pad geometries are possible within the scope of the present invention. 
       FIG. 8  illustrates an alternative embodiment  800  of the mounting interface  810  wherein the mounting interface  810  includes a mount pad  812  formed integral with the baseplate  820 . The baseplate  820  is cast according to a predetermined design specification, and then the pad  812  is formed by machining surfaces  830 ,  832 ,  834 ,  836  of the baseplate. In  FIG. 8 , the surface  836  adjacent the pad is also machined to form a pad having a curved surface  840 . However, those skilled in the art will recognize that the invention is not meant to be limited to the geometry illustrated in  FIG. 8 , but that other pad geometries are possible within the scope of the present invention. 
     In addition to providing a reduced surface area for lowering the resonant frequency associated with disk drive, a damping ring may be provided to dissipate distortion energy. For certain troublesome vibration modes of the spindle motor, elastic deformation of the mount flange may occur that entails transverse bending of the mount flange between any two of the three pads. The damping ring acts as a constrained layer damper by being sandwiched between the baseplate and the motor mount flange. Accordingly, the amplitude of vibration will be reduced to cause lower acoustic output of the disk drive.  FIGS. 9–14  illustrate different embodiments of the damping ring according to the present invention. However, those skilled in the art will recognize that the invention is not meant to be limited to these illustrated embodiments, but rather other damping ring embodiments are possible within the scope of the present invention. 
       FIG. 9  illustrates a damping ring  910  coupled to the mount flange  912  according to the present invention. In  FIG. 9 , a partial cross-section of the mount flange  912  and the baseplate  914  are shown. The mount flange  912  is shown having a mount pad  920  according to the present invention. The damping ring  910  is provided to dissipate distortion energy caused by the vibration of the mount flange  912 . The damping ring  910  includes a notch (not shown) wherein the mount pad  920  is disposed. Accordingly, the damping ring  910  surrounds the mount pad  920  on three sides. An inner, vertical portion  930  of the damping ring  910  rests against the back of the mount pad  920 . The damping ring  910  actually extends slightly below the plane of the bottom of the mount pad  920  so that the damping ring  910  contacts the baseplate  914  and is slightly compressed when the motor is installed. However, the damping ring  910  does not reside between the mount pad  920  and the baseplate  914 . Thus, the geometric location and stability of the motor and mount flange  912  is not affected by the damping ring, i.e., there is still solid metal-to-metal contact between the motor/mount flange  912  and the baseplate  914 . Those skilled in the art will recognize that the damping ring  910  may be formed in a single ring with cutouts for the mount pads  920 . 
       FIG. 10  illustrates a second embodiment of a damping ring  1010  coupled to a mount flange  1012  according to the present invention. In  FIG. 10 , a partial cross-section of the mount flange  1012  and the baseplate  1014  are again shown with the mount flange  1012  having a mount pad  1020 . The damping ring  1010  is provided to dissipate distortion energy caused by the vibration of the mount flange  1012 . The damping ring  1010  includes a notch (not shown) wherein the mount pad  1020  is disposed therebetween. Accordingly, the damping ring  1010  surrounds the mount pad  1020  on three sides. An inner, vertical portion  1030  of the damping ring  1010  rests against the back of the mount pad  102 . In addition, an outer, vertical portion  1032  is provided for engaging with the side wall  1033  of the baseplate  1014 . The outer, vertical portion  1032  dissipates energy resulting from sheer distortion between the baseplate  1014  and the mount flange  1012 . The outside diameter of the mount flange  1012  is recessed radially  1034  to allow room for the damping ring  1010 , but the recessed portion  1034  does not extend into the region of the mount pads  1020 . Thus, the mount pads  1020  still locate the motor in the horizontal (x-y) plane as well as vertical direction. Preferably the damping ring  1010  is a relatively soft, elastomeric material, therefore it can be slightly compressed into the bore of the baseplate  1014  when installed. However, those skilled in the art will recognize that other types of soft or compressible may be used without departing from the scope of the present invention. 
       FIG. 11  illustrates a third embodiment of a damping ring  1110  coupled to the baseplate  1114  according to the present invention. In  FIG. 11 , a partial cross-section of the mount flange  1112  and the baseplate  1114  are shown. The mount flange  1112  is shown having a mount pad  1120 . The damping ring  1110  is coupled to the baseplate  1114  to dissipate distortion energy caused by the vibration of the mount flange  1112  therewith. The damping ring  1110  includes a notch (not shown) wherein the mount pad  1120  is disposed. Accordingly, the damping ring  1110  surrounds the mount pad  1120  on three sides. An inner, vertical portion  1130  of the damping ring  1110  rests against the lip  1150  of the baseplate  1114 . 
       FIG. 12  illustrates a fourth embodiment of a damping ring  1210  coupled to the baseplate  1214  according to the present invention. In  FIG. 12 , a partial cross-section of the mount flange  1212  and the baseplate  1214  are shown. The mount flange  1212  is shown having a mount pad  1220 . The damping ring  1210  is coupled to the baseplate  1214  to dissipate distortion energy caused by the vibration of the mount flange  1212  therewith. The damping ring  1210  includes a notch (not shown) wherein the mount pad  1220  is disposed and the damping ring  1210  surrounds the mount pad  1220  on three sides. An outer, vertical portion  1232  of the damping ring  1210  rests against a face  1233  of the baseplate and a lateral portion  1236  extends over a top surface  1252  of the baseplate  1214 . The outer, vertical portion  1232  dissipates energy resulting from sheer distortion between the baseplate  1214  and the mount flange  1212 . 
       FIG. 13  illustrates a fifth embodiment of a damping ring  1310  coupled to the mount flange  1312  according to the present invention. In  FIG. 13 , the damping ring  1310  includes an outer, vertical portion  1332  that rests against a face  1333  of the baseplate  1314  for dissipating energy resulting from sheer distortion between the baseplate  1314  and the mount flange  1312 . At a position where the mount flange  1312  overhangs the baseplate  1314 , the damping ring  1310  includes a seal  1370  for acting as a barrier between the baseplate  1314  and the mount flange  1312  to prevent outside contamination from entering the disk enclosure. 
       FIG. 14  illustrates a sixth embodiment of a damping ring  1410  coupled to the baseplate  1414  according to the present invention. In  FIG. 14 , the damping ring  1410  includes an outer, vertical portion  1432  that rests against a face  1433  of the baseplate  1414  for dissipating energy resulting from sheer distortion between the baseplate  1414  and the mount flange  1412 . At a position where the mount flange  1412  overhangs the baseplate  1414 , the damping ring  1410  includes a seal  1470  for providing a seal between the baseplate  1414  and the mount flange  1412  to prevent outside contamination from entering the disk enclosure. 
     In summary, the present invention provides a mounting interface between the baseplate and the motor mount for stabilizing the baseplate/mount. The mounting interface includes mount pads that are coupled or made integral with the mount flange or the baseplate. The mounting interface provides a stable mount between the mount flange and the baseplate by providing three points defining a plane that is generally parallel to the plane of the mount flange and/or the baseplate. A damping ring may be used for dissipating distortion energy between the motor, baseplate and/or mount flange. 
     The foregoing description of the exemplary embodiment of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not with this detailed description, but rather by the claims appended hereto.