Abstract:
An apparatus for reducing vibration and noise in a disc drive spindle motor comprising a first supporting member abutting a first portion of a stator and a second support member abutting a second portion of the stator.

Description:
[0001]    This application claims benefit of United States Provisional Application No. 60/247,096, entitled FIXED-END STATORS FOR REDUCING ACOUSTIC NOISE, filed Nov. 9, 2000 which is hereby incorporated by reference in its entirety. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention relates to the field of stator assemblies of the type used in concert with high-speed spindle elements. More specifically, the invention relates to stator assemblies utilized in a disc drive system.  
         BACKGROUND OF THE INVENTION  
         [0003]    Disc drive memory systems have been used in computers for many years for storage of digital information. Information is recorded on concentric memory tracks of a magnetic disc medium, the actual information being stored in the form of magnetic transitions within the medium. The discs themselves are rotatably mounted on a spindle. The information is accessed using read/write heads generally located on a pivoting arm that moves radially over the surface of the disc. The read/write heads or transducers must be accurately aligned with the storage tracks on the disc to ensure proper reading and writing of information.  
           [0004]    During operation, the discs are rotated at very high speeds within an enclosed housing by using an electric motor generally located inside a hub that supports the discs. One type of motor in common use is known as an in-hub or in-spindle motor. Such in-spindle motors typically have a spindle mounted by using two ball or hydrodynamic bearing systems to a motor shaft disposed in the center of the hub. Generally, such motors include a stator comprising a plurality of “teeth” arranged in a circle. The teeth each support a coil that may be sequentially energized to polarize the stator. A plurality of permanent magnets are disposed on a rotor in alternating polarity adjacent the stator. As the coils disposed on the stators are sequentially energized in alternating polarity, the magnetic attraction and repulsion of each stator to the adjacent magnets on the rotor cause the spindle to rotate, thereby rotating the disc and passing the information storage tracks beneath the head.  
           [0005]    [0005]FIG. 1 is a sectional view of a prior art hydrodynamic bearing spindle motor  100 . The spindle motor  100  includes a stationary shaft  102 , a hub  104  and a stator  106 . The shaft  102  is fixed and attached to a base  108 . The hub  104  is supported by the shaft  102  through a bearing  110  for rotation about the shaft  102 . The bearing  110  is, for example, a hydrodynamic bearing.  
           [0006]    The hub  104  includes a disc carrier flange  112  that supports a disc pack (not shown) for rotation about the shaft  104 . The disc pack is held on the disc carrier flange  112  by a disc clamp (not shown). A plurality of permanent magnets  114  are attached to an inner surface  116  of the hub  104 , with the hub  104  and the magnets  114  acting as a rotor for the spindle motor  100 .  
           [0007]    The stator  106  is generally formed of a stack of stator laminations  118  that form a plurality of stator “teeth” that are each wound with an associated stator winding  120 . The stator  106  is generally retained in the base  108  by fasteners, adhesives or other conventional methods. In the embodiment illustrated in FIG. 1, the stator  106  is disposed in a pocket  122  formed in the base  108 . The stator  106  is cantilever mounted at its inner circumference  124  to the base  108 . The distal end  126  of each “tooth” of the stator  106  is unsupported.  
           [0008]    As the coils  120  on the stator  106  are sequentially energized to generate a rotational force, the stator  106  vibrates. The vibration that occurs tends to produce an acoustic noise that is irritating to many users and conveys the appearance of an inferiorly constructed unit.  
           [0009]    Therefore, there is a need in the art to minimize the vibrations and noise contribution produced by the stator during motor operation.  
         SUMMARY OF THE INVENTION  
         [0010]    A disc drive spindle motor having improved acoustic properties is provided. In one embodiment, the disc drive spindle motor includes a base, a shaft, a rotor and a stator. A bearing interconnects the rotor with the shaft and allows the rotor to rotate about the shaft. The stator includes a plurality of “teeth” supported by a stationary support member. Each tooth has a coil wound thereover. At least two annular supports positioned beneath the stator support a first portion and a second portion of the stator. Furthermore, the first portion of the stator is bonded to the support housing. By supporting both of the portions, vibrations in the stator are substantially reduced, thereby reducing acoustic noise generated by the motor. To optimize the reduction of vibration, slots can be formed in the annular supports such that the size and spacing of the slots alter the resonant frequency of the motor vibrations. As such, the invention may be used to tune the vibration frequency of the stator away from the resonant frequencies of other components of the motor. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The teachings of the invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:  
         [0012]    [0012]FIG. 1 is a sectional view of a prior art spindle motor;  
         [0013]    [0013]FIG. 2 is a sectional view of a hydrodynamic bearing spindle motor in accordance with the present invention;  
         [0014]    [0014]FIG. 3 is a horizontal cross-section of one embodiment of a stator in accordance with the invention;  
         [0015]    [0015]FIG. 4 is a detailed sectional view of the stator shown in FIG. 3, taken along lines  4 - 4 ; and  
         [0016]    [0016]FIGS. 5A, 5B,  5 C and  5 D are series of plan sections of the housing with the stator removed. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    The invention comprises a spindle motor for a disc drive data storage device wherein the stator assembly is supported within the base of the device to reduce acoustic noise. FIG. 2 is a sectional view of a hydrodynamic bearing spindle motor  200  in accordance with the present invention. The spindle motor  200  comprises a motor support base  202 , a stationary shaft  204 , a hub  206  and a stator  208 . Formed within the motor support base  202  are a pair of annular supports  210  and  212  for supporting the stator  208 . The annular supports  210  and  212  form concentric circles equidistant from the centrally located shaft  204 . These annular supports are formed to support the stator  204  about the stator&#39;s first and second external diameters. Other elements and components of the motor such as the permanent magnets  214 , the stator laminations  216  and the associated stator windings  218  are common to other motors of this type.  
         [0018]    [0018]FIG. 3 is a horizontal cross-section of one embodiment of the stator  208  as supported by supports  210  and  212 . The stator is supported by at least two annular supports  210  and  212  and bonded to at least one of the supports  210  and  212 . The stator  208  comprises a lamination of a plurality of metal plates  302  (a top view of one plate  302  is shown). Each plate  302  is die cut to have an annular portion  304  with a plurality of “T-shaped” teeth  306 A- 306 P extending radially from the annular portion  304 . Each tooth  306 A- 306 P comprises a radially extending portion  308  and an end portion  310 . For simplicity only, tooth  306 A contains reference numbers for portions  308  and  310 . Each of the teeth  306 A- 306 P have a winding  218  wrapped about the radially extending portion  308 . The inventive stator supports  210  and  212  respectively support the annular portion  304  and the end portion  310  of the stator  208 , i.e., the stator  208  is supported on either side of each winding  312 . The phase windings  312  can have a number of winding configurations. Some examples of phase windings that may benefit from the invention are discussed in U.S. patent Ser. No. 08/469,643, entitled IRONLESS HYDRODYNAMIC SPINDLE MOTOR, filed Jun. 6, 1995 by Dunfield et al., and in U.S. patent Ser. No. 08/400,661, entitled HYDRODYNAMIC SPINDLE MOTOR HAVING DISTRIBUTED WINDINGS, filed Mar. 8,1995 by Dunfield et al., both of which are commonly assigned and are hereby incorporated by reference in their entireties.  
         [0019]    [0019]FIG. 4 is a detailed sectional view of the stator  208  of FIG. 2. This figure depicts in detail a section of the stator  208  and the base  202  comprising the first diameter support  210  (e.g., an inner support), the second diameter support  212  (e.g., an outer support) and a section of the first diameter support housing  400  bonded to the stator  208 . The second diameter support  212  may also be bonded (e.g., using epoxy) to the stator  208 . The stator windings  218  shown are suspended in a trough  404  without contacting the motor support base  202 . In this embodiment of the invention, the motor support base  202  is bonded to the annular portion  304  of the stator  208  using an epoxy  402 . The support given by both the first diameter support  210  and second diameter support  212  prevents the stator  208  from vibrating. Both the first diameter and second diameter supports  210  and  212  may be segmented or solid in nature. In either case, the supports  210  and  212  follow the annular shape of the stator  208  and as such, form concentric rings equidistant from the central point  304  as shown in FIG. 3.  
         [0020]    [0020]FIG. 5A through 5D depict sections of a plan view showing a portion of the motor base  202 . The portion of the motor base  202  depicted is a portion wherein the stator  208  sits and is supported by a first diameter annular support  210  and a second diameter annular support  212  support ring having a trough  404  for the stator&#39;s windings formed therebetween. FIGS. 5A, 5B,  5 C and  5 D each show alternative embodiments of the present invention having combinations of both segmented and solid annular supports  410  and  412 . Each of the annular supports  410  and  412  themselves may be either formed in the motor support base  202  or added later as separate components.  
         [0021]    [0021]FIG. 5A depicts a portion of the housing base  202  comprising a pair of solid annular supports  410  and  412 .  
         [0022]    [0022]FIG. 5B depicts a portion of a housing base  500  having a slotted second annular support  502  and a solid first annular support  504 , where the second and first supports  502  and  504  are separated by a trough  506 .  
         [0023]    [0023]FIG. 5C depicts a portion of a housing base  508  comprising a solid second annular support  510  and a slotted first annular support  512  where the second and first supports  510  and  512  are separated by a trough  512 .  
         [0024]    [0024]FIG. 5D depicts a portion of a housing base  516  comprising a slotted second annular support  518  and a slotted first support  520  where the second and first supports  518  and  520  are separated by a trough  522 .  
         [0025]    The slotted supports  502 ,  512 ,  518  and  520  may be formed as a casting or machined into the motor support base. The choice of which specific combination to be used is dependent upon the type of motor being chosen for the particular application. Each type of motor may have a separate set of components which may be unique to the motor&#39;s application. This difference in motors may create a variance in the resonance frequency of the motor&#39;s component elements. As such, the motor housing&#39;s support may resonate at a different frequency, depending on the motor component&#39;s resonance frequency. By knowing the excitation frequencies of the motor and other drive components, the choice of motor support housing may be determined. The underlying theory behind the selection of the type of motor support housing, whether it be solid or slotted stator supports, is directly dependent upon the excitation frequencies of the other motor or drive components associated with the motor. By choosing a motor support base design whose known resonant frequency is far different from that of the excitation frequencies of the other motor elements, the potential for creating resonating noise and vibration is significantly reduced.  
         [0026]    The relative size and shape of the slots  524  and support portion  526  of each slotted support  502 ,  512 ,  518  and  520  can be optimized to alter the resonant frequency of the motor.  
         [0027]    The motor shown in the illustrated embodiment is an “outer rotor” type motor where the rotor rotates about the stator. Those skilled in the art will understand that the invention also applied to “inner rotor” type motors where the rotor is located within the stator. With either motor-type, the invention supports the stator in at least two locations to reduce the vibration of the motor.  
         [0028]    Although the invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, the placement of one or more segmented or solid annular ring members as supports under the stator or in a supporting configuration of the stator can be configured in a variety of ways and can include a combination of the embodiments discussed above. The embodiments shown in the figures are provided by way of example only.