Abstract:
A clamp ring detaching method of detaching from a motor hub a clamp ring fastened to the motor hub, the clamp ring comprising a plurality of hub pressing portions contacting the outer circumferential surface of the motor hub and connecting portions which connect the hub pressing portions, each connecting portion having a concave portion, the method including pressing portions of at least one of the concave portions, which are displaced from a center of the concave portion, outwards in a radial direction of the clamp ring in order to remove the clamp ring from the motor hub.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2005-119852, filed Apr. 18, 2005, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a method of detaching a clamp ring that is fixed to a motor hub of, for example, a magnetic disk device by means of shrink fitting; a tool for detaching such a clamp ring; and a method for manufacturing a magnetic disk device.  
         [0004]     2. Description of the Related Art  
         [0005]     There is known a magnetic disk device in which a medium is turned and information is read from and written to a recording surface of the medium. In recent years, the magnetic disk device has been made into such a compact size (for example, around 0.85 inches) as to be loaded on a mobile device such as a cellular phone.  
         [0006]      FIG. 12  is a cross-sectional view of a 0.85-inch magnetic disk device.  
         [0007]     As shown in  FIG. 12 , the 0.85-inch magnetic disk device includes a part called a motor hub  200 , which is fixed to a rotator of a motor. The motor hub  200  rotates as a rotating shaft of the motor, and a disk-shaped medium  201  is fixed to the outer circumference thereof.  
         [0008]     A clamp ring  202  is used for fixing the medium  201 . The clamp ring  202  is attached to the motor hub  200 , and presses the medium  201  onto a support portion  200   a  of the motor hub  200  to prevent the medium  201  from rotating or moving on the motor hub  200 .  
         [0009]     Meanwhile, in the manufacture of a magnetic disk device, the magnetic disk device is in some cases disassembled and reassembled according to evaluation results of functions and operations after assembly. For this reason, it is desired for the method of fixing the medium  201  that the medium  201  can be detached from the motor hub  200 .  
         [0010]     Accordingly, two kinds of fixing method currently proposed by those skilled in the art are introduced in  FIGS. 13 and 14 .  
         [0011]      FIG. 13  is a view showing a configuration of a magnetic disk device in which the clamp ring  202  has been attached by a thread fastening method.  
         [0012]     As shown in  FIG. 13 , the medium  201  in the magnetic disk device is fixed onto the motor hub  200  by the clamp ring  202  that is screwed to the motor hub  200 . Accordingly, thread grooves  203  are formed on the outer circumference of the motor hub  200  and the inner circumference of the clamp ring  202 , respectively. In the case of the thread fastening method, the clamp ring  202  can be detached from the motor hub  200  only by loosening screws.  
         [0013]      FIG. 14  is a view showing a configuration of a magnetic disk device in which the clamp ring  202  has been attached by a shrink fitting method.  
         [0014]     As shown in  FIG. 14 , the medium  201  in the magnetic disk device is fixed onto the motor hub  200  by the clamp ring  202  that is shrink-fitted to the motor hub  200 . Meanwhile, the inner diameter of the clamp ring  202  used herein at a room temperature is smaller than the outer diameter of the motor hub  200 .  
         [0015]     In the case when the clamp ring  202  is shrink-fitted to the motor hub  200 , the clamp ring  202  is first heated and expanded. At the moment when the inner diameter of the clamp ring  202  becomes larger than the outer diameter of the motor hub  200 , the clamp ring  202  is mounted on the motor hub  200 . Then, the clamp ring  202  is naturally or forcibly made back to a room temperature. Thereby, the clamp ring  202  shrinks, and gets in a state of being fastened to the motor hub  200 . In the case of the shrink fitting method, the clamp ring  202  can be detached from the motor hub  200  only by expanding the inner diameter of the clamp ring  202  (for example, refer to Jpn. Pat. Appln. KOKAI Publication No. 8-297910).  
         [0016]     However, the 0.85-inch magnetic disk device has a problem that the structure thereof is limited by its narrow internal space, so that the thread fastening method cannot be applied thereto. Therefore, the only way is to use the shrink fitting method for the 0.85-inch magnetic disk device. However, the clamp ring fixed by the shrink fitting method has a problem that it is more difficult to detach the clamp ring than in the thread fastening method.  
       BRIEF SUMMARY OF THE INVENTION  
       [0017]     Accordingly, an aspect of the present invention is to provide a clamp ring detaching method, a clamp ring detaching tool, and a method of manufacturing a magnetic disk device, for enabling to easily detach a clamp ring fixed by a fitting method that prevents relative movement.  
         [0018]     The clamp ring detaching method, the clamp ring detaching tool, and the method of manufacturing a magnetic disk device according to the present invention are configured as described below for example,  
         [0019]     (1) A clamp ring detaching method of detaching from a motor hub a clamp ring fastened to the motor hub, the clamp ring comprising a plurality of hub pressing portions contacting the outer circumferential surface of the motor hub and connecting portions which connect the hub pressing portions, each connecting portion having a concave portion, the method comprising: pressing portions of at least one of the concave portions, which are displaced from a center of the concave portion, outwards in a radial direction of the clamp ring in order to remove the clamp ring from the motor hub.  
         [0020]     (2) A clamp ring detaching tool to be used when detaching from a motor hub a clamp ring fastened to the motor hub, the clamp ring comprising a plurality of hub pressing portions contacting the outer circumferential surface of the motor hub and connecting portions which connect the hub pressing portions, each connecting portion having a concave portion, the tool comprising: a pressing portion which presses those portions of at least one of the concave portions which are displaced from a center of the concave portion, at the same time outwards in a radial direction of the clamp ring.  
         [0021]     (3) A method of manufacturing a magnetic disk device, having detaching from a motor hub a clamp ring fastened to the motor hub, the clamp ring comprising a plurality of hub pressing portions contacting the outer circumferential surface of the motor hub and connecting portions which connect the hub pressing portions, each connecting portion having a concave portion, the detaching comprising: pressing portions of at least one of the concave portions, which are displaced from a center of the concave portion, outwards in a radial direction of the clamp ring in order to remove the clamp ring from the motor hub.  
         [0022]     According to the invention, a clamp ring fixed to a motor hub can be easily detached.  
         [0023]     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0024]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.  
         [0025]      FIG. 1  is a cross-sectional view of a magnetic disk device according to a first embodiment of the present invention;  
         [0026]      FIG. 2  is a cross-sectional view of a motor hub according to the first embodiment;  
         [0027]      FIG. 3  is a plan view of a clamp ring according to the first embodiment;  
         [0028]      FIG. 4  is a configuration diagram of an attaching/detaching device according to the first embodiment;  
         [0029]      FIG. 5A  is a front view of a heater head and attaching/detaching heads according to the first embodiment;  
         [0030]      FIG. 5B  is a plan view of the heater head and the attaching/detaching heads according to the first embodiment;  
         [0031]      FIG. 6  is a cross-sectional view of an attaching/detaching pin according to the first embodiment;  
         [0032]      FIG. 7A  is a view showing a stress applied to the clamp ring when the clamp ring is detached by use of the attaching/detaching pins according to the first embodiment;  
         [0033]      FIG. 7B  is a view showing a stress applied to the clamp ring when the clamp ring is detached by use of the attaching/detaching pins according to the first embodiment;  
         [0034]      FIG. 7C  is a view showing a stress applied to the clamp ring when the clamp ring is detached by use of the attaching/detaching pins according to the first embodiment;  
         [0035]      FIG. 8A  is a view showing a stress applied to the clamp ring when the clamp ring is detached by use of cylindrical attaching/detaching pins;  
         [0036]      FIG. 8B  is a view showing a stress applied to the clamp ring when the clamp ring is detached by use of the cylindrical attaching/detaching pins;  
         [0037]      FIG. 8C  is a view showing a stress applied to the clamp ring when the clamp ring is detached by use of the cylindrical attaching/detaching pins;  
         [0038]      FIG. 9A  is a process chart in case of detaching the clamp ring by a detaching method according to a second embodiment of the present invention;  
         [0039]      FIG. 9B  is a process chart in case of detaching the clamp ring by the detaching method according to the second embodiment;  
         [0040]      FIG. 9C  is a process chart in case of detaching the clamp ring by the detaching method according to the second embodiment;  
         [0041]      FIG. 10  is a plan view of a clamp ring according to a third embodiment of the present invention;  
         [0042]      FIG. 11A  is a process chart in case of detaching the clamp ring by a detaching method according to the third embodiment;  
         [0043]      FIG. 11B  is a process chart in case of detaching the clamp ring by the detaching method according to the third embodiment;  
         [0044]      FIG. 11C  is a process chart in case of detaching the clamp ring by the detaching method according to the third embodiment;  
         [0045]      FIG. 12  is a cross-sectional view of a 0.85-inch magnetic disk device;  
         [0046]      FIG. 13  is a configuration view of a magnetic disk device in which a clamp ring has been attached by a thread fastening method; and  
         [0047]      FIG. 14  is a configuration view of a magnetic disk device in which a clamp ring has been attached by a shrink fitting method. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0048]     First to third embodiments of the present invention will be illustrated in more details with reference to the accompanying drawings hereinafter.  
         [0000]     (First Embodiment)  
         [0049]     First, a first embodiment will be explained hereinafter.  
         [0000]     [Configuration of Magnetic Disk Device  1 ] 
         [0050]      FIG. 1  is a cross-sectional view of a magnetic disk device  1  according to the first embodiment of the invention.  
         [0051]     As shown in  FIG. 1 , the magnetic disk device  1  includes: a medium  10  serving as a recording medium; a spindle motor  20  to turn the medium  10 ; a motor hub  30  serving as a rotating shaft of the spindle motor  20 ; a clamp ring  40  to fix the medium  10  to the motor hub  30 ; a magnetic head  50  to read and write information from and into the medium  10 ; a base  60  to which the spindle motor  20  is assembled; and a cover  70  to cover the medium  10 , the spindle motor  20 , the motor hub  30 , the clamp ring  40 , and the magnetic head  50 .  
         [0052]     The medium  10  is of a disk shape, and an attachment hole  10   a  for inserting the motor hub  30  therein is provided on a radial central portion of the medium. As the medium  10 , a magnetic disk such as a hard disk is used.  
         [0053]     The spindle motor  20  is configured by a fixed shaft  21 , a fluid dynamic bearing  22 , a bearing seal  23 , a permanent magnet  24 , and a stator  25 , and the spindle motor generates a turning force around the fixed shaft  21  in the permanent magnet  24 .  
         [0054]     The fixed shaft  21  is of a cylindrical shape, and has the base  60  fixed with a screw  61  to one end surface thereof and has the cover  70  fixed with a screw  71  to the other end surface thereof. The fluid dynamic bearing  22  is configured by an inner ring  22   a  to be mounted on the outer circumferential surface of the fixed shaft  21 , and an outer ring  22   b  arranged rotatably on the outer circumferential surface of the inner ring  22   a . The bearing seal  23  is provided on an end surface of the fluid dynamic bearing  22  at the side of the cover  70 . The permanent magnet  24  is fixed onto the outer circumference of the motor hub  30 . The stator  25  is arranged at the outer circumferential side of the permanent magnet  24 .  
         [0055]     The motor hub  30  is of a substantially cylindrical shape, and is mounted on the outer circumferential surface of the outer ring  22   b  of the fluid dynamic bearing  22 . Thereby, when the spindle motor  20  is actuated, the motor hub  30  rotates around the fixed shaft  21  by the turning force generated in the permanent magnet  24 .  
         [0056]      FIG. 2  is a cross-sectional view of the motor hub  30  according to the first embodiment.  
         [0057]     As shown in  FIG. 2 , the motor hub  30  has, on the outer circumferential surface thereof, an attachment portion  31  for attaching the medium  10  thereto, a clamped portion  32  for mounting the clamp ring  40  thereon (the outer circumferential surface of the motor hub  30 ), and a support portion  33  for supporting the medium  10 .  
         [0058]     Meanwhile, the width of the attachment portion  31  is slightly smaller than the thickness of the medium  10 . Consequently, when the clamp ring  40  is mounted on the clamped portion  32 , the end surface of the clamp ring  40  presses the medium  10 .  
         [0059]      FIG. 3  is a plan view of the clamp ring  40  according to the first embodiment.  
         [0060]     As shown in  FIG. 3 , the clamp ring  40  is mounted on the motor hub  30  by shrink fitting, and presses the media  10  to the support portion  33  of the motor hub  30 . The clamp ring  40  includes; four hub pressing portions  41  that contact the clamped portion  32  of the motor hub  30  and four connecting portions  42  that connect the hub pressing portions  41  adjacent in the circumferential direction of the clamp ring  40 . Each connecting portion  42  has a concave portion  44  that form an empty space  43  between the clamp ring  40  and the outer circumferential surface of the motor hub  30 .  
         [0061]     In the present embodiment the clamp ring  40  is composed of four hub pressing portions  41  and four connecting portions  42 . The numbers of the hub pressing portions  41  and the numbers of the connecting portions  42  are not limited to four.  
         [0062]     The inner circumferential surface of the hub pressing portions  41  is made of a part of a cylindrical surface. The inner diameter of the hub pressing portions  41  is formed smaller than the outer diameter of the motor hub  30  at a room temperature such that the hub pressing portions can be shrink-fitted to the motor hub  30 .  
         [0063]     The inner circumferential surface of the connecting portions  42  is made of a part of a cylindrical surface smaller than the inner circumferential surface of the hub pressing portions  41 . Thereby, the connecting portions  42  are thinner than the hub pressing portions  41 . Note that the shape of the connecting portions  42  is not limited to a cylindrical surface so far as it is a smooth curved shape not so as to be subject to stress concentration.  
         [0064]     As shown in  FIG. 1 , the magnetic head  50  is configured by a head main body  51  that reads and writes information from and into the medium  10 , and a swing arm  52  that swings the head main body  51  on the medium  10 .  
         [0000]     [Configuration of Attaching/Detaching Device  100 ] 
         [0065]      FIG. 4  is a configuration diagram of an attaching/detaching device  100  according to the first embodiment.  
         [0066]     As shown in  FIG. 4 , the attaching/detaching device (detaching device)  100  includes a first positioning platform  101 , a second positioning platform  102 , a bed  103 , a first transfer mechanism  104 , a heater head  105 , a second transfer mechanism  106 , four attaching/detaching heads  107  (only two illustrated), a third transfer mechanism  108 , a control unit  109 , and an input unit  110 . The first positioning platform  101  positions the clamp ring  40 , and the second positioning platform  102  positions the base  60  having the spindle motor  20  assembled therein. The bed  103  supports the first and second positioning platforms  101 ,  102 . The first transfer mechanism  104  transfers the bed  103  in a horizontal direction (direction X in the figure). The heater head  105  receives the clamp ring  40  from the first positioning platform  101  and heats the clamping ring  40 . The second transfer mechanism  106  transfers the heater head  105  in a vertical direction (direction Z in the figure). The attaching/detaching heads  107  attach and detach the clamp ring  40  to and from the motor hub  30  assembled in the spindle motor  20  of the base  60  positioned by the second positioning platform  102 . The third transfer mechanism  108  transfers the attaching/detaching heads  107  in the horizontal and vertical directions. The control unit  109  controls the first, second, third transfer mechanisms  104 ,  106 ,  108 . The input unit  110  is provided for inputting instructions from an operator to the control unit  109 .  
         [0067]      FIG. 5A  is a front view of the heater head  105  and the attaching/detaching heads  107  according to the first embodiment, and  FIG. 5B  is a plan view of the heater head  105  and the attaching/detaching heads  107  according to the first embodiment.  
         [0068]     As shown in  FIGS. 5A and 5B , the heater head  105  includes a heater  111  and a vacuum device  112 . The heater  111  heats the clamp ring  40  received from the first positioning platform  101  up to a shrink fitting temperature. The vacuum device  112  generates an absorbing force for absorbing and holding the clamp ring  40  to the under surface of the heater head  105  through a plurality of absorbing holes (not shown) formed in the heater head  105 .  
         [0069]     As a consequence, the heater head  105  receives the clamp ring  40  from the first positioning platform  101 , heats the clamping ring  40  up to the shrink fitting temperature, and supplies the heated clamping ring to the motor hub  30  on the base  60  positioned by the second positioning platform  102 .  
         [0070]     On the outer circumferential surface of the heater head  105 , groove portions  113  are arranged at an interval of 90 degrees along the horizontal direction. Parts of the clamp ring  40  absorbed and held by the heater head  105  are exposed from the respective groove portions  113 .  
         [0071]     The attaching/detaching heads  107  are arranged at an interval of 90 degrees at the same height, and have a configuration such that the third transfer mechanism  108  moves the attaching/detaching heads close to and away from the shaft center of the spindle motor  20  positioned by the second positioning platform  102 .  
         [0072]     In the end portions of the detaching/detaching heads  107 , there are arranged substantially vertically attaching/detaching pins  114  for adding a pressing force to the clamp ring  40  when attaching and detaching the clamp ring  40  to and from the motor hub  30 .  
         [0073]      FIG. 6  is a cross-sectional view of the attaching/detaching pin  114  according to the first embodiment.  
         [0074]     As shown in  FIG. 6 , the attaching/detaching pin (detaching tool)  114  is of a substantially trapezoidal cross section as a whole, which has substantially the same curvature radius as that of the connecting portions  42  of the clamp ring  40 . On the lower ends of the attaching/detaching pins  114 , plane-shaped first pressing surfaces (pressing surfaces)  115   a  (illustrated in only  FIG. 5A ) are formed. On both the end portions of the attaching/detaching pins  114  in the circumferential direction of the clamp ring  40 , there are formed second pressing surfaces (pressing surfaces)  115   b  having substantially the same radius of curvature as that of the inner circumferential surface of the connecting portions  42  of the clamp ring  40 . Further, on the radial inside and the radial outer side of the clamp ring  40  in the attaching/detaching pins  114 , a surface  115   c  which connects the second pressing surfaces  115   b  is formed, the surface  115   c  having a larger radius of curvature than the second pressing surfaces  115   b . Meanwhile, the surface  115   c  may be a plane surface.  
         [0075]     The first pressing surfaces  115   a  press down the clamp ring  40  exposed from the groove portions  113  of the heater head  105  when the clamp ring  40  is attached to the motor hub  30 . The second pressing surfaces  115   b  press the inner circumferential surface of the concave portions  44  of the connecting portions  42  of the clamp ring  40  to the radial outer side when the clamp ring  40  is detached from the motor hub  30 .  
         [0000]     [Method of Manufacturing Magnetic Disk Device  1 ] 
         [0076]     The spindle motor  20  having the motor hub  30  is assembled into the base  60 , and the medium  10  is mounted on the support portion  33  of the motor hub  30 . Thereby, the motor hub  30  is inserted into the attachment hole  10   a  of the medium  10 , and the clamped portion  32  protrudes from the attachment hole  10   a  to the opposite side of the base  60 .  
         [0077]     Then, the clamp ring  40  is attached to the clamped portion  32  protruding from the attachment hole  10   a  of the medium  10 , and further the magnetic head  50  is assembled, so that the cover  70  is finally attached. The following method of attaching the clamp ring  40  and method of detaching the clamp ring  40  are part of the processes in the method of manufacturing the magnetic disk device  1 .  
         [0000]     [Method of Attaching Clamp Ring  40 ] 
         [0078]     A method of attaching the clamp ring  40  in the case where the clamp ring  40  is attached to the clamped portion  32  of the motor hub  30  by the shrink fitting method will be explained hereinafter.  
         [0079]     When the clamp ring  40  is to be attached to the motor hub  30 , the clamp ring  40  is first supplied onto the first positioning platform  101 , wherein the clamp ring  40  is positioned. Further, as another process, the base  60  to which the spindle motor  20  having the motor hub  30  has been assembled is supplied onto the second positioning platform  102 , wherein the base  60  is positioned.  
         [0080]     Next, the bed  103  is moved by the first transfer mechanism  104 , and the first positioning platform  101  is set to a processing position. The processing position is the position where the clamp ring  40  is attached to and detached from the motor hub  30 .  
         [0081]     Then, the heater head  105  is lowered by the second transfer mechanism  106 , and the clamp ring  40  positioned on the first positioning platform  101  is absorbed and held to the under surface of the heater head  105  by the vacuum device  112 .  
         [0082]     Next, the heater head  105  is moved upward, and at the same time, the clamp ring  40  is heated. Note that the heater head  105  is heated by the heater  111  before the heater head  105  absorbs and holds the clamp ring  40 .  
         [0083]     Subsequently, the bed  103  is moved by the first transfer mechanism  104 , and the second positioning platform  102  is set to the processing position. Note that, before the second positioning platform  102  is set to the processing position, the medium  10  is attached to the clamped portion  31  of the motor hub  30  assembled in the base  60 .  
         [0084]     Next, the heater head  105  is lowered by the second transfer mechanism  106 , and the clamp ring  40  whose inner diameter has been expanded by heating from the heater head  105  is mounted on the supported portion  33  of the motor hub  30 . Thereby, the clamped portion  32  of the motor hub  30  is inserted into the clamp ring  40 .  
         [0085]     Then, the attaching/detaching heads  107  are moved close to the shaft center of the spindle motor  20  by the third transfer mechanism  108 . When the attaching/detaching pins  114  of the attaching/detaching heads  107  arrive at a specified position in the groove portions  113  of the heater head  105 , the attaching/detaching heads  107  are lowered by the third transfer mechanism  108 , so that the upper surface of the clamp ring  40  is pressed by the first pressing surfaces  115   a  of the attaching/detaching pins  114 . At the same time when the pressing of the clamp ring  40  starts, the heater head  105  is moved upward by the second transfer mechanism  106 .  
         [0086]     Thereafter, the clamp ring  40  is cooled down to a room temperature. Then, the inner diameter of the hub pressing portions  41  of the clamp ring  40  becomes smaller. As a consequence, the clamp ring  40  is attached to the clamped portion  32  of the motor hub  30  by the shrink fitting method. In this manner, the medium  10  is fixed onto the support portion  33  of the motor hub  30 .  
         [0000]     [Method of Detaching Clamp Ring  40 ] 
         [0087]     Next, explanation will be given to a method of detaching the clamping ring  40  in the case where the clamp ring  40  has been attached to the clamped portion  32  of the motor hub  30  by the shrink fitting method.  
         [0088]     When, in the assembly of the magnetic disk device  1 , the medium  10 , the spindle motor  20 , the motor hub  30 , and the clamp ring  40  are assembled in the base  60 , an evaluation experiment on functions and actions is carried out at that point.  
         [0089]     If any failure is found in this evaluation experiment, the base  60  having the medium  10  and others assembled therein is transferred to the attaching/detaching device  100 , so that the clamp ring  40  is detached.  
         [0090]     When the clamp ring  40  is detached from the motor hub  30 , the base  60  having the medium  10  and others assembled therein is first supplied onto the second positioning platform  102 , wherein the base  60  is positioned.  
         [0091]     Next, the bed  103  is moved by the first transfer mechanism  104 , and the second positioning platform  102  is set to the processing position. At this moment, the attaching/detaching heads  107  have already been set so that the attaching/detaching pins  114  correspond to the empty spaces  43  between the outer circumferential surface of the motor hub  30  and the inner circumferential surface of the connecting portions  42  of the clamp ring  40 .  
         [0092]     Next, the attaching/detaching heads  107  are lowered by the third transfer mechanism  108 , and the attaching/detaching pins  114  are inserted into the empty spaces  43  between the outer circumferential surface of the motor hub  30  and the inner circumferential surface of the connecting portions  42  of the clamp ring  40 .  
         [0093]     Then, the four attaching/detaching heads  107  are moved to the radial outer side of the clamp ring  40  at the same time, and the two portions displaced by the same distance to both the sides from the center in the concave portions  44  of the connecting portions  42  of the clamp ring  40  are pressed by the two second pressing surfaces  115   b  of the attaching/detaching pins  114 , respectively.  
         [0094]     Thereby, the inner diameter of the hub pressing portions  41  of the clamp ring  40  expands, and there occurs an empty space C (illustrated in only  FIG. 7C ) between the outer circumferential surface of the motor hub  30  and the inner circumferential surface of the hub pressing portions  41 . When the pushing amount of the connecting portions  42  by the attaching/detaching pins  114  becomes a predetermined value, the heater head  105  is lowered by the second transfer mechanism  106 , and the clamp ring  40  is absorbed and held to the under surface of the heater head  105 .  
         [0095]     At the same time, the heater head  105  and the attaching/detaching heads  107  are moved upward by the second and third transfer mechanisms  106 ,  108 , and the clamp ring  40  is pulled out from the clamped portion  32  of the motor hub  30 . Through the above procedures, the removal of the clamp ring  40  is completed. Meanwhile, the detached clamp ring  40  is disposed.  
         [0096]     What is important herein is that when the inner diameter of the hub pressing portions  41  of the clamp ring  40  is expanded, the two portions displaced by the same distance to both the sides from the center in the concave portions  44  of the connecting portions  42  are pressed by use of the attaching/detaching pins  114  according to the present embodiment. The other members, from which the clamp ring  40  has been removed, are subjected to a step of attaching new clamp ring  40  to them.  
         [0000]     [Simulations] 
         [0097]     Next, the distribution of a pressure applied to the clamp ring  40  by using the attaching/detaching pins  114  according to the embodiment, and the distribution of a pressure applied to the clamp ring  40  by using cylindrical attaching/detaching pins  114 A are examined by simulations. In  FIGS. 7A  to  7 C and  FIGS. 8A  to  8 C, portions wherein a pressure occurs are shown by arrows.  
         [0098]      FIGS. 7B  to  7 C each are a view showing a stress applied to the clamp ring  40  when the clamp ring  40  is detached by use of the attaching/detaching pins  114  according to the first embodiment.  
         [0099]     Before the attaching/detaching pins  114  contact the clamp pin  40 , a pressure occurs at the both end portions (only one end portion illustrated) of the hub pressing portions  41  as shown by the arrow in  FIG. 7A . This shows that the hub pressing portions  41  tighten up the motor hub  30 .  
         [0100]     When the connecting portions  42  are expanded by 10 μm to the radial outer side by means of the attaching/detaching pins  114 , the pressure that occurred at the hub pressing portions  41  has disappeared as shown in  FIG. 7B . This shows that the tightening of the motor hub  30  by the hub pressing portions  41  has been released.  
         [0101]     It is known that when the connecting portions  42  are further expanded by 40 μm (50 μm from the initial state) to the radial outer side by means of the attaching/detaching pins  114 , a 30-μm empty space C is formed between the outer circumferential surface of the motor hub  30  and the inner circumferential surface of the hub pressing portions  41 , as shown in  FIG. 7C . This shows that the clamp ring  40  is ready to be detached from the motor hub  30 .  
         [0102]      FIGS. 8A  to  8 C each are a view showing a stress applied to the clamp ring  40  when the clamp ring  40  is detached by use of cylindrical attaching/detaching pins  114 A. As the attaching/detaching pins  114 A, pins are used that have a sufficiently small radius of curvature in comparison with the radius of curvature of the inner circumferential surface of the connecting portions  42 .  
         [0103]     It is found that, before the attaching/detaching pins  114 A contact the clamp pin  40 , a pressure occurs at the both end portions (only one end portion illustrated) of the hub pressing portions  41  as shown by the arrow in  FIG. 8A . This shows that the hub pressing portions  41  tighten up the motor hub  30 .  
         [0104]     It is found that, when the connecting portions  42  are expanded by 10 μm to the radial outer side by means of the attaching/detaching pins  114 A, the pressure that has been applied to both the end portions of the hub pressing portions  41  decreases, and another pressure occurs at the central portion of the hub pressing portions  41 , as shown in  FIG. 8B . This shows that the tightening of the motor hub  30  by the hub pressing portions  41  is still not released.  
         [0105]     It is known that, when the connecting portions  42  are further expanded by 20 μm (30 μm from the initial state) to the radial outer side by means of the attaching/detaching pins  114 A, the pressure applied to the central portion of the hub pressing portions  41  increases as shown in  FIG. 8C . This shows that the tightening of the motor hub  30  by the hub pressing portions  41  increases.  
         [0106]     From the simulations in  FIGS. 7A  to  7 C and  FIGS. 8A  to  8 C, it has been apparent that, when the attaching/detaching pins  114  according to the embodiment are used, in other words, when the two portions away by the same distance to both the sides from the center in the inner circumferential surface of the connecting portions  42  are pressed at the same time, the empty space C is formed between the outer circumferential surface of the motor hub  30  and the inner circumferential surface of the hub pressing portions  41  with a small pushing amount.  
         [0000]     (Operation by Present Embodiment)  
         [0107]     According to the method of detaching the clamp ring  40 , the attaching/detaching pins  114  of the clamp ring  40 , and the method of manufacturing the magnetic disk device  1 , the two portions away by the same distance to both the sides from the center in the inner circumferential surface of the concave portions  44  of the connecting portions  42  are pressed when the clamp ring  40  is detached from the motor hub  30 . When these two portions are pressed, the connecting portions  42  are expanded in the circumferential direction, and the circumferential length of the clamp ring  40  is expanded.  
         [0108]     Because the empty space C is formed between the outer circumferential surface of the motor hub  30  and the inner circumferential surface of the hub pressing portions  41  with a small pushing amount, the removal work of the clamp ring  40  is simplified, and the time required for detaching the clamp ring  40  is shortened.  
         [0109]     In the present embodiment, the attachment and detachment of the clamp ring  40  is carried out by the single attaching/detaching device  100 , but it may be carried out by separate devices. When the attachment and detachment of the clamp ring  40  is carried out by separate devices, there is no need to stop an assembly line, which makes it possible to increase the efficiency of assembly.  
         [0110]     As a device for attaching the clamp ring  40 , a magnetic disk device assembly device described in Japanese Patent Application No. 2004-247618 may be employed.  
         [0111]     In the present embodiment, the center of the concave portions  44  of the connecting portions  42  is in the plan view of the clamp ring  40 .  
         [0000]     (Second Embodiment)  
         [0112]     Next, a second embodiment will be explained hereinafter. Herein, with regard to the same configuration and function as those in the first embodiment, explanations thereof are omitted.  
         [0113]      FIGS. 9A  to  9 C each are a process chart in case of detaching the clamp ring  40  by a detaching method according to the second embodiment of the present invention.  
         [0000]     [Method of Detaching Clamp Ring  40 ] 
         [0114]     When the clamp ring  40  is to be detached from the motor hub  30 , the cylindrical attaching/detaching pins  114 A are first inserted into the respective empty spaces  43  between the motor hub  30  and the connecting portions  42 , as shown in  FIG. 9A .  
         [0115]     Next, as shown in  FIG. 9B , the inner circumferential surface of the concave portions  44  of the connecting portions  42  is pressed in the arrow direction by the attaching/detaching pins  114 A. Thereby, the connecting portions  42  that are thin in the clamp ring  40  are expanded in the circumferential direction by plastic deformation, so that the circumferential length of the clamp ring  40  is expanded.  
         [0116]     Subsequently, as shown in  FIG. 9C , the outer circumferential surface of the connecting portions  42  is pressed in the arrow direction by the attaching/detaching pins  114 A, and the clamp ring  40  is formed so as to become substantially circular. As a consequence, the empty space C is formed between the outer circumferential surface of the motor hub  30  and the inner circumferential surface of the hub pressing portions  41 , and the clamp ring  40  is ready to be detached from the motor hub  30 .  
         [0117]     Even when the method of the present embodiment is used, the clamp ring  40  attached to the motor hub  30  by the shrink fitting method can be detached easily, and consequently, the time required for detaching the clamp ring  40  is shortened.  
         [0000]     (Third Embodiment)  
         [0118]     Next, a third embodiment will be explained hereinafter. Herein, with regard to the same configuration and function as those in the first embodiment, explanations thereof are omitted.  
         [0119]      FIG. 10  is a plan view of a clamp ring  40 B according to the third embodiment of the present invention, and  FIGS. 11A  to  11 C each are a process chart in case of detaching the clamp ring  40 B by a detaching method according to the third embodiment.  
         [0000]     [Configuration of Clamp Ring  40 B] 
         [0120]     As shown in  FIG. 10 , the clamp ring  40 B according to the embodiment includes notch portions  45  for respectively engaging with the attaching/detaching pins  114 A, in the outer circumferential surface of the hub pressing portions  41  according to the above embodiment. These notch portions  45  are arranged to be adjacent to two opposing connecting portions  42   a ,  42   a.    
         [0000]     [Method of Detaching Clamp Ring  40 B] 
         [0121]     When the clamp ring  40 B is to be detached from the motor hub  30 , the attaching/detaching pins  114 A are first engaged respectively to the notch portions  45  formed in the respective hub pressing portions  41  of the clamp ring  40 B, as shown in  FIG. 11A .  
         [0122]     Next, as shown in  FIG. 11B , the notch portions  45  are pressed in the arrow direction by the attaching/detaching pins  114 A. Then, the connecting portions  42   a ,  42   a  that are near the notch portions  45  deform, and the central portions thereof protrude in the direction going away from the outer circumferential surface of the motor hub  30 . Thereby, the two connecting portions  42   b ,  42   b  that are away from the notch portions  45  are expanded in the circumferential direction, so that the circumferential length of the clamp ring  40 B is expanded.  
         [0123]     Subsequently, as shown in  FIG. 1C , the outer circumferential surfaces of the connecting portions  42   a ,  42   a  protruding in the direction going away from the outer circumferential surface of the motor hub  30  are pressed by the respective attaching/detaching pins  114 A in the arrow direction, i.e., to the radial inner side of the clamp ring  40 B, and the clamp ring  40 B is formed so as to become substantially circular. Thereby, the empty space C is formed between the outer circumferential surface of the motor hub  30  and the inner circumferential surface of the hub pressing portions  41 , and the clamp ring  40  is ready to be detached from the motor hub  30 .  
         [0124]     Even when the method of the present embodiment is used, the clamp ring  40  attached to the motor hub  30  by the shrink fitting method can be detached easily, and consequently, the time required for detaching the clamp ring  40  is shortened.  
         [0125]     Note that the method of expanding the connecting portions in the circumferential direction is not limited to the second and third embodiments, but any other method may be employed.  
         [0126]     The present invention is not limited to the above embodiments, but the present invention may be embodied by appropriately modifying the constituent elements thereof without departing from the spirit or essential characteristics thereof. It is also possible to extract various stages of invention by appropriate combinations of plural constituent elements disclosed in each of the embodiments. For example, some constituent elements may be deleted from all the elements shown in the embodiments. Furthermore, the constituent elements of different embodiments may be appropriately combined.  
         [0127]     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.