Patent Document

BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a method of manufacturing a base for a hard disk drive. 
         [0002]    There is a conventional base for a hard disk drive as shown in  FIGS. 5 and 6 .  FIG. 5  is a plan view of a base used for casing parts of a hard disk drive and  FIG. 6  is a sectional view of the base of  FIG. 5 . 
         [0003]    As shown in  FIG. 5  and  FIG. 6 , a base  101  for a hard disk drive has a recess  103  for mounting a motor and a through-hole  105  formed at the center of the recess  103 . 
         [0004]    The motor has a spindle passed through the through-hole  105  of the recess  103  of the base  101  and is fixed to the recess  103  by screws and the like. However, fixing work using screws and the like is complicated and needs a large number of parts. 
         [0005]    In contrast, there is a base as shown in  FIG. 7 .  FIG. 7  is a sectional view partly showing a base  107  on which a motor  115  is mounted. The base  107  of  FIG. 7  has a through-hole  109  and a motor holder  111 . The motor holder  111  is formed by press and has a cylindrical shape communicating with the through-hole  109 . The motor holder  111  includes two depressions  113  each having an annular shape formed by circumferentially cutting on the inner circumferential surface thereof. The motor holder  111  holds the motor  115  fitted and fixed via adhesive  117  to the inner circumferential surface thereof. 
         [0006]    The solidified adhesive  117  engages with the depressions  113 . This enables to easily and securely fix the motor  115  to the motor holder  111  without using screws and the like. 
         [0007]    Under this structure, however, the depressions  113  must be cut additionally after press-forming the motor holder  111 . This requires high dimensional accuracy to improve the machining accuracy. Namely, the quality of the base  107  greatly depends on the press accuracy, requiring highly sophisticated technique for press accuracy control. 
         [0008]    If the cutting is carried out after plating treatment of the base  107 , the base material of the motor holder  111  is exposed at the treated surface. This causes fatal adverse effect such as corrosion affecting the hard disk drive performance. Therefore, attention to the fatal adverse effect is required. 
         [0009]    The cutting generates burrs, so measures against the burrs are also required. 
         [0010]    As this result, manufacturing efficiency and yield of the hard disk drive may be lowered, to have a disadvantage in cost. 
       Patent Literature 1: Japanese Patent Application Laid-Open Publication No. 09-120669 
     Patent Literature 2: Japanese Patent Application Laid-Open Publication No. 08-153386 
     SUMMARY OF THE INVENTION 
       [0011]    A problem solved by the invention is that highly sophisticated technique for accuracy control, attention to deficiencies such as corrosion causing fatal adverse effect which affects a hard disk drive performance and measures against burrs are required and manufacturing efficiency and yield are lowered to have disadvantage in cost. 
         [0012]    In order to accomplish the object, the present invention is mainly characterized by at least one depression pressure-formed on an inner circumferential surface of a motor holder. 
         [0013]    A base for a hard disk drive according to the present invention includes a motor holder having at least one depression pressure-formed on an inner circumferential surface thereof, so that it requires no cutting for forming a depression and enables to facilitate accuracy control, and suppress deficiencies such as corrosion, because no base material is exposed. In addition to this, no measures against burrs also are required. Consequently, the base can improve manufacturing efficiency and yield of the base and the hard disk drive and have an advantage in cost. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  shows a finished base for a hard disk drive according to an embodiment of the present invention in which  FIG. 1(   a ) is a plan view of the base,  FIG. 1(   b ) is a sectional view taken along a line SA-SA of  FIG. 1(   a ), and  FIG. 1(   c ) is an enlarged sectional view partly showing the base of  FIG. 1(   a ). 
           [0015]      FIG. 2(   a ) is a plan view showing a panel after forming semi-formed depressions according to the embodiment,  FIG. 2(   b ) is a sectional view taken along a line SB-SB of  FIG. 2(   a ), and  FIG. 2(   c ) is an enlarged sectional view partly showing the panel of  FIG. 2(   a ). 
           [0016]      FIG. 3(   a ) is a plan view showing a panel after the punching process before forming the motor holder,  FIG. 3(   b ) is a sectional view taken on line SC-SC of  FIG. 3(   a ), and  FIG. 3(   c ) is an enlarged sectional view partly showing the panel. 
           [0017]      FIG. 4(   a ) is an enlarged sectional view partly showing the panel and a pressing machine before a press in a holder forming process and  FIG. 4(   b ) is a sectional view after the press. 
           [0018]      FIG. 5  is a plan view showing a base for a hard disk drive according to a related art. 
           [0019]      FIG. 6  is a sectional view showing the base of  FIG. 5 . 
           [0020]      FIG. 7  is an enlarged sectional view partly showing a base for a hard disk drive mounting a motor according to another related art. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    The present invention improves manufacturing efficiency and yield of a base and a hard disk drive and has an advantage in cost by pressure-forming depressions on a motor holder of a base for a hard disk drive. 
       First Embodiment 
     Base for a Hard Disk Drive 
       [0022]      FIG. 1  shows a finished base  1  for a hard disk drive according to an embodiment of the present invention in which  FIG. 1(   a ) is a plan view of the base  1 ,  FIG. 1(   b ) is a sectional view taken along a line I-I of  FIG. 1(   a ), and  FIG. 1(   c ) is an enlarged sectional view partly showing the base of  FIG. 1(   a ). 
         [0023]    The base  1  includes a panel  3  made of, for example, SPCE which is a cold-rolled steel sheet for deep drawing as a kind of SPC material. The panel  3  is shaped by press and has a circular protrusion  5  and a through-hole  7 . The protrusion  5  has a circular shape in a plan view of  FIG. 1(   a ) and protrudes from a second face, opposite to a first face, of other portion of the panel  3  in thickness direction of the panel  3 . The circular through-hole  7  is punched at the center of the protrusion  5 . The panel  3  includes a motor holder  9  integrally formed on the panel  3  for holding a motor for the hard disk drive corresponding to the through-hole  7 . The motor holder  9  has a cylindrical shape with a circular shape in a cross section, communicating with the through-hole  7 . The motor holder  9  protrudes from a first face of the protrusion  5  of the panel  3  in a thickness direction of the panel  3  with a specified height. The motor holder  9  has a thickness TB which is slightly thinner than the thickness TP of the panel  3  by ironing at the time of press. 
         [0024]    The motor holder  9  has grooves  13  and  15  serving as depressions on the inner circumferential surface  11  thereof. The grooves  13  and  15  are formed by pressure-forming such as press. Each of the grooves  13  and  15  has an annular shape along the inner circumferential surface  11  of the motor holder  9 . Namely, the grooves are circumferentially formed. The grooves  13  and  15  are separated from and parallel with each other in the height direction of the motor holder  9 . According to the present embodiment, therefore, two grooves  13  and  15  as a plurality of depressions are provided in sequence in the height direction of the motor holder  9 . The grooves  13  and  15  of the present embodiment have substantially same shape, depth, and width. 
         [0025]    According to the present embodiment, the motor holder  9 , as is the case of  FIG. 7 , holds a motor for the hard disk drive fitted and fixed to the inner circumferential surface  11  thereof through an adhesive (not shown). Since the solidified adhesive, therefore, engages with grooves  13  and  15 , the motor can be easily and securely fixed to the motor holder  9  without using any screws and the like. 
       Manufacturing Method 
       [0026]      FIGS. 2 to 4  relate to a method of manufacturing the base  1  for the hard disk drive.  FIG. 2(   a ) is a plan view showing the panel  3  after forming semi-formed grooves  17  and  19 ,  FIG. 2(   b ) is a sectional view taken along a line II-II of  FIG. 2(   a ), and  FIG. 2(   c ) is an enlarged sectional view partly showing the panel  3  of  FIG. 2(   a ).  FIG. 3(   a ) is a plan view showing the panel  3  after the punching process before forming the motor holder  9 ,  FIG. 3(   b ) is a sectional view taken on line III-III of  FIG. 3(   a ), and  FIG. 3(   c ) is an enlarged sectional view partly showing the panel  3 .  FIG. 4(   a ) is an enlarged sectional view partly showing the panel  3  and a pressing machine before a press in a holder forming process and  FIG. 4(   b ) is a sectional view after the press. 
         [0027]    As shown in  FIGS. 2(   a ) to  2 ( c ) and  3 ( a ) to  3 ( c ), semi-formed grooves  17  and  19  are formed on the protrusion  5  of the panel  3 . Then, the panel  3  is pressed as shown in  FIGS. 4(   a ) and  4 ( b ). As this result, the finished grooves  13  and  15  can be formed on the inner circumferential surface  11  of the motor holder  9  as shown in  FIGS. 1(   a ) to  1 ( c ). 
         [0028]    The grooves  13  and  15  are formed by a groove semi-forming process corresponding to a depression semi-forming process incorporated into or separated from a series of pressing processes of the base  1 . 
         [0029]    According to the present embodiment, semi-formed grooves  17  and  19  are formed in the groove semi-forming process as shown in  FIGS. 2(   a ) to  2 ( c ). In the groove semi-forming process, two semi-formed grooves  17  and  19 , as a plurality of semi-formed depression, concentric with the center of the protrusion  5  are formed by press as pressure-forming such that the outer semi-formed groove  19  is arranged at outside of the inner semi-formed groove  17 . 
         [0030]    Then, in the punching process by press, a hole  21  concentric with the semi-formed grooves  17  and  19  is formed on the inside of the semi-formed groove  17  as shown in  FIG. 3 . The diameter of the hole  21  is set to be smaller than the diameter of a punch used in a motor holder forming process later discussed. 
         [0031]    The shape and the size of the semi-formed grooves  17  and  19  have the following relationship. The semi-formed groove  17  has a triangular cross section and the semi-formed groove  19  has a trapezoidal cross section. The bottom  23  of the semi-formed groove  17  has no or least plane. The bottom  25  of the semi-formed groove  19  is a plane of width B. Semi-formed grooves  17  and  19  have inner gentle slopes  27  and  29  and outer steep slopes  31  and  33  opposite to the gentle slopes  27  and  29  in the cross section of  FIGS. 2 and 3  respectively. 
         [0032]    The gradient angle θ 1  of the gentle slope  27  is greater than the gradient angle θ 2  of the gentle slope of 29 relative to a horizontal line, so that the relationship between the gradient angles θ 1  and θ 2  can be represented with θ 1 &gt;θ 2 . The gradient angle θ 3  of the steep slope  31  is greater than the gradient angle θ 4  of the steep slope  33 , so that the relationship between the gradient angles θ 3  and θ 4  can be represented with θ 3 &gt;θ 4 . The relationships between the gradient angles θ 1  and θ 3  of the slopes  27  and  31  and between the gradient angles θ 2  and θ 4  of the slopes  29  and  33  can be represented with θ 1 &lt;θ 3  and θ 2 &lt;θ 4 , respectively. 
         [0033]    The semi-formed grooves  17  and  19  have substantially same depth H in a vertical direction as shown in  FIG. 3 . The opening width W 1  of the inner semi-formed groove  17  is formed to be relatively smaller than the opening width W 2  of the outer semi-formed groove  19 , and the relationship between the width W 1  and W 2  can be represented with W 1 &lt;W 2 . 
         [0034]    The differences in size and shape between the semi-formed grooves  17  and  19  are capable of adjusting the size and shape of finished grooves  13  and  15  with the elongation of the panel  3  caused by press at the time of the holder forming process. That is, difference among the gradient angles θ 1  and θ 2  of gentle slopes  27  and  29  and gradient angles θ 3  and θ 4  of steep slopes  31  and  33  and difference between opening width W 1  and W 2  are provided to bring the sectional shape in the width direction (which is a vertical direction in  FIG. 1 ) of finished grooves  13  and  15  to be symmetrical and to bring finished grooves  13  and  15  to have an equal size and shape after the motor holder  9  is formed. In contrast, if it is allowed to have a difference in size and shape of finished grooves, it may employ semi-finished grooves equal to each other in size and shape having same slope inclinations, opening widths, and depths. In addition, it may employ single semi-formed groove or three or more semi-formed grooves as a plurality of semi-formed grooves, i.e., single finished groove or a plurality of finished grooves. In the case of employing three or more semi-formed grooves, all the inclinations, opening widths, and depths of the semi-finished grooves are set stepwise to be gradually changed toward outside so as to unify the finished grooves after forming the motor holder. 
         [0035]    Then, in the holder forming process, the motor holder  9  is formed as shown in  FIG. 4  after pressure-forming semi-formed grooves  17  and  19 . 
         [0036]    The holder forming process is carried out by a pressing machine. The pressing machine includes an upper die  35  and a lower die  37 . The upper die  35  is provided with a punch  39  slidably arranged in a hole thereof. The lower die  37  is provided with a hole  41 . The punch  39  and the hole  41  are concentrically arranged. The punch  39  lowers as shown in  FIGS. 4(   a ) and  4 ( b ) to the panel  3  grasped between the upper die  35  and the lower die  37  to form the holder  9 . 
         [0037]    The punch  39  of the upper die  37  has a diameter D which is smaller than that of the hole  41  of the lower die  39 . The clearance S as a difference between the punch  39  of the diameter D and a hole  41  of the lower die  37  is set to be smaller than the thickness t of the panel  3  according to the present embodiment, the clearance S is set to about 0.1 mm, for example. Consequently, the panel  3  is ironed between the punch  39  and the hole  41  and the thickness of the motor holder  9  is formed to be thinner than thickness t of other portion. 
         [0038]    Because the panel  3  is elongated at the portion of the motor holder  9  due to the holder forming process, the semi-formed grooves  17  and  19  which differ in size and shape from each other as described above becomes finished grooves  13  and  15  which are uniform in size and shape as shown in  FIG. 1 . 
         [0039]    The base  1  after forming the motor holder  9  with grooves  13  and  15  is plated for maintaining the surface cleanliness. Alternatively, the base  1  before forming the motor holder  9  may be plated. Even if semi-finished grooves are formed a plated base, forming the semi-finished grooves by press enables to prevent the base from exposing the base material to maintain the cleanliness of the plated surface. Namely, it may form the semi-finished grooves before and after plating the base. 
         [0040]    According to the present embodiment, the grooves  13  and  15  are pressure-formed on the inner circumferential surface  11  of the motor holder  9  by press. Therefore, no cutting is required and accuracy control can be facilitated. Pressure-forming the grooves  13  and  15  by press prevent from exposing the base material unlike cutting grooves, so that deficiencies such as corrosion, etc. are suppressed and no measures against burrs and the like are required. Consequently, manufacturing efficiency and yield of the base  1  and the hard disk drive can be improved and it can have an advantage in cost. 
         [0041]    Each of the grooves  13  and  15  has an annular shape along the inner circumferential surface  11  of the motor holder  9 , so that adhesives can be engaged with the grooves  13  and  15  on the entire inner circumference of the inner circumferential surface  11  of the motor holder  9 . Therefore, still securely fixing can be achieved. 
         [0042]    Two grooves  13  and  15  separated from each other are provided in sequence in the height direction of the motor holder  9 , so that adhesives can be engaged at two grooves  13  and  15  and still securely fixing can be achieved. 
         [0043]    The motor for the hard disk drive is fixed to the motor holder  9 , so that it is possible to suppress deficiencies which exert fatal effects on the hard disk drive performance such as corrosion and outgassing due to gas such as air that remain in blowholes. This enables to assemble the hard disk drive with the cleanliness in a satisfactory condition. 
         [0044]    The method of manufacturing the base  1  is provided with the groove semi-forming process in which semi-formed grooves  17  and  19  are pressure-formed by press on the panel  3  and the holder forming process in which the motor holder  9  is formed after pressure-forming the semi-formed grooves  17  and  19  to form grooves  13  and  15  on the inner circumferential surface of the motor holder  9 . Therefore, the grooves  13  and  15  can be easily formed on the inner circumferential surface  11  of the motor holder  9  by pressure-forming. 
         [0045]    In the groove semi-forming process, the inner and outer semi-formed grooves  17  and  19  are formed concentrically and at the same time, the opening width W 1  of the inner semi-formed groove  17  is formed to be relatively smaller than the opening width W 2  of the outer semi-formed groove  19 . Therefore, the size of grooves  13  and  15  can be formed equally after processing the motor holder  9  with the elongation of the panel  3  due to press of the holder forming process at once. 
         [0046]    In the groove semi-forming process, the gradient angles θ 1  and θ 3  of the inner slopes  27  and  29  are smaller than the gradient angles θ 2  and θ 4  of outer slopes  31  and  33  in the semi-formed grooves  17  and  19 , respectively. The cross-sectional shape of the grooves  13  and  15  in the width direction (the vertical direction in  FIG. 1(   c )) can be formed to be symmetrical with the elongation of the panel  3  due to press of the holder forming process. 
         [0047]    In the groove semi-forming process, the depth of the inner semi-formed groove  17  may be formed to be relatively larger than that of the outer semi-formed groove  19  on the outer circumferential side. 
         [0048]    In the groove semi-forming process, a bottom plane of width equal to the outer semi-formed groove on the outer circumferential side may be employed to the inner semi-formed groove. 
         [0049]    At the same time, the inclinations of inner slopes and outer slopes may be set to be same, respectively. In this case, the opening width and depth of finished grooves may be varied. 
         [0050]    Grooves  13  and  15  can be processed by pressure-forming using fluid pressure, etc. after forming the motor holder  9 . 
         [0051]    The depression is only required to engage with adhesives and is not limited to a groove. Namely, it may employ a grid formed from grooves crossing each other, a knurled-surface, and other various forms instead of the groove. 
         [0052]    For the base material, SPCC for general purpose and SPCD for drawing may be used as other SPC material instead, and SUS (stainless steel) material instead of SPCE for deep drawing.

Technology Category: y