Patent Publication Number: US-2015062750-A1

Title: Rotating device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to a rotating device. 
     2. Description of the Related Art 
     As to disk drive devices like hard disk drives which are a kind of rotating devices, for example, a structure is disclosed in which a hub where multiple magnetic recording disks are to be mounted is supported by a sleeve encircling a fixed shaft, and is rotated together with the sleeve (see, for example, JP 2003-139129 A, JP 2010-261580 A, JP 2012-087867 A). In addition, a structure is also disclosed in which the hub is supported at an end of a freely rotatable shaft, and is rotated together with the shaft (see, for example, JP 2012-87861 A). 
     In the aforementioned structures, as to the hub and the sleeve, for example, one end of the sleeve is fixed to a hole of the hub by interference fitting, such as press-fitting or thermal insert. According to such interference fitting, however, there is a possibility that the sleeve is deformed, and the rotation of the hub and that of the magnetic recording disk mounted on the hub become unstable due to the deformation. 
     Hence, in order to suppress a deformation of the sleeve, the hole of the hub and the sleeve may be fixed by loose fit with the aid of a bond, etc. In this case, however, it is necessary to, for example, fit the sleeve in the hole of the hub and to maintain the bonding position by a jig, etc., until the bond is cured. Hence, there is a possibility that due to an attachment of the jig and a detachment thereof, the production efficiency decreases. 
     The present disclosure has been made in view of the aforementioned circumstances, and it is an objective of the present disclosure to provide a rotating device which can suppress a deformation of a component without a reduction of a production efficiency, and which can stably rotate a rotating body. 
     SUMMARY OF THE INVENTION 
     To accomplish the above objective, a rotating device according to a first aspect includes: a stationary body; a rotating body formed with an opening encircling a rotation axis; a fluid dynamic bearing mechanism which supports the rotating body relative to the stationary body, and which has a portion at one end side fitted in and fixed to the opening; a support portion that protrudes from an outer circumference of the fluid dynamic bearing mechanism to support the rotating body; and an abutting portion provided at the rotating body so as to abut the support portion, in which: the support portion includes a flange protruding outwardly in a radial direction from the outer circumference of the fluid dynamic bearing mechanism; and the abutting portion includes a step that is a recess which is formed along an open end of the opening and into which at least a part of the flange enters. 
     To accomplish the above objective, a rotating device according to a second aspect of the present disclosure includes: a stationary body; a rotating body formed with an opening encircling a rotation axis; a fluid dynamic bearing mechanism which supports the rotating body relative to the stationary body, and which has a portion at one end side fitted in and fixed to the opening; a support portion that protrudes from an outer circumference of the fluid dynamic bearing mechanism to support the rotating body; and an abutting portion provided at the rotating body so as to abut the support portion, in which: the support portion includes a flange that protrudes outwardly in a radial direction from an outer circumference of the fluid dynamic bearing mechanism, and an annular portion extending from an outer circumference of the flange in an axial direction toward the rotating body; and the abutting portion includes an annular groove which is provided so as to surround the opening, and with which the annular portion is engaged. 
     To accomplish the above objective, a rotating device according to a third aspect of the present disclosure includes: a stationary body; a rotating body formed with an opening encircling a rotation axis; a fluid dynamic bearing mechanism which supports the rotating body relative to the stationary body, and which has a portion at one end side fitted in and fixed to the opening; a support portion that protrudes from an outer circumference of the fluid dynamic bearing mechanism to support the rotating body; and an abutting portion provided at the rotating body so as to abut the support portion, in which: the support portion includes a tapered supporting inclined face inclined relative to the rotation axis; and the abutting portion includes a tapered abutting inclined face which is formed on an inner circumference of the opening and which is inclined along the supporting inclined face. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating an example general structure of a disk drive device according to a first embodiment; 
         FIG. 2  is a general cross-sectional view illustrating the disk drive device of the first embodiment; 
         FIG. 3  is a general cross-sectional view illustrating a disk drive device according to a second embodiment; 
         FIG. 4  is a general cross-sectional view illustrating a disk drive device according to a third embodiment; and 
         FIG. 5  is a general cross-sectional view illustrating a disk drive device according to a fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments to carryout the present disclosure will be explained below with reference to the accompanying drawings. In the respective figures, the same component will be denoted by the same reference numeral, and the duplicated explanation thereof will be omitted. The dimension of a component in each figure is enlarged or scaled-down as needed to facilitate understanding. In addition, a part of a component not important to explain the embodiment will be omitted n each figure. 
     A disk drive device that is a rotating device according to an embodiment of the present disclosure allows, for example, magnetic recording disks recording data magnetically to be mounted, and rotates and drives the magnetic recording disks. Such a disk drive device is utilized as, for example, a hard disk drive. 
     First Embodiment 
     Structure of Disk Drive Device 
       FIG. 1  illustrates an example structure of a disk drive device  100  according to this embodiment, and a general whole structure will be explained first. 
     The disk drive device  100  includes a top cover  10 , a base  20 , a data reader/writer  22 , magnetic recording disks  24 , a clamper  26 , and a shaft  30 . 
     In the following explanation, with the top cover  10  being attached to the base  20 , the top-cover- 10  side is defined as an upper side, while the base- 20  side is defined as a lower side. In addition, a direction parallel to a rotation axis R of the magnetic recording disks  24  is defined as an axial direction, and an arbitrary direction passing through the rotation axis R on a plane perpendicular to the rotation axis R is defined as a radial direction. In the radial direction, a side distant from the rotation axis R is defined as an outer circumference side, while a side close to the rotation axis R is defined as an inner circumference side. Those notations are not intended to limit the posture of the disk drive device  100  when in use, and the disk drive device  100  can be used in any arbitrary posture. 
     (Top Cover) 
     The top cover  10  is a thin plate in a substantially rectangular shape, and includes a screw through-holes  10 A provided in the circumference, a cover protrusion  10 B protruding downwardly toward the base  20 , and a center hole  10 C provided in the center of the cover protrusion  10 B. The cover protrusion  10 B is provided around the rotation axis R. 
     The top cover  10  is formed in a predetermined shape by, for example, pressing an aluminum sheet or a steel sheet, and a surface process like plating may be performed on the top cover  10  to suppress a corrosion. The top cover  10  is fixed to an upper face of the base  20  by peripheral screws  11  fitted in the respective screw through-holes  10 A. The top cover  10  and the base  20  are fixed together so as to air-tightly seal the interior of the disk drive device  100 . A center screw  12  is fitted in the center hole  10 C, and the center screw  12  is engaged with a retainer hole  30 A of the shaft  30  fixed to the base  20 . 
     (Base) 
     The base  20  includes a bottom plate  20 A forming the bottom of the disk drive device  100 , and an outer circumference wall  20 B formed along the outer circumference of the bottom plate  20 A so as to surround an area where the magnetic recording disks  24  are to be mounted. Screw holes  20 C engaged with the respective peripheral screws  11  are provided in the upper face of the outer circumference wall  20 B. 
     The top cover  10  is fixed to the upper face of the outer circumference wall  20 B of the base  20  by the peripheral screws  11 . A disk retaining space  28  defined by the bottom plate  20 A of the base  20 , the outer circumference wall  20 B thereof, and the top cover  10  is air-tightly sealed and isolated from an external environment, and is filled with a clean gas like air having dusts, etc., eliminated. Hence, foreign materials like dusts are prevented from sticking to the magnetic recording disks  24 , and a possibility of a false operation of the disk drive device  100  is reduced. 
     The base  20  is formed by die-casting of, for example, an aluminum alloy, but the material and the forming method are not limited to those examples. The base  20  may be formed by pressing a sheet metal of, for example, stainless-steel or aluminum. In the case of pressing, an emboss work may be performed so as to form convexities on the upper side of the base  20 . When the emboss work is performed on the predetermined portion, a deformation of the base  20  can be suppressed. 
     In addition, the base  20  may have a surface process layer like nickel plating or a coating layer like an epoxy resin, and may be have the bottom plate  20 A formed of equal to or greater than two laminated sheets. Still further, the base  20  may have a part formed of a resin. 
     (Magnetic Recording Disk) 
     The magnetic recording disk  24  is, for example, a 3.5-inch magnetic recording disk formed of an aluminum alloy and having a diameter of substantially 90 mm. An engagement hole formed at the center and having a diameter of, for example, 25 mm is engaged with the circumference of a hub  50 . According to the disk drive device  100 , for example, three to six magnetic recording disks  24  are to be mounted on the hub  50  and are rotated and driven. The multiple magnetic recording disks  24  are fixed to the hub  50  by the clamper  26  with spacers being present therebetween. 
     (Data Reader/Writer) 
     The data reader/writer  22  includes an unillustrated recording/playing head, a swing arm  22 A, a pivot assembly  22 B, and a voice coil motor  22 C. The recoding/playing head is attached to the tip of the swing arm  22 A, records data in the magnetic recording disk  24 , or reads the data therefrom. The pivot assembly  22 B supports the swing arm  22 A in a swingable manner to the base  20  around a head rotating axis S. The voice coil motor  22 C allows the swing arm  22 A to swing around the head rotating axis S to move the recording/playing head to a desired location over the top face of the magnetic recording disk  24 . The pivot assembly  22 B and the voice coil motor  22 C are configured by a conventionally well-known technology of controlling the position of a head. 
     &lt;Structure of Bearing Mechanism&gt; 
       FIG. 2  is a cross-sectional view of the disk drive device  100  taken along a line A-A in  FIG. 1 , and is a general cross-sectional view illustrating an example bearing mechanism of the disk drive device  100 . 
     The disk drive device  100  includes the base  20 , the shaft  30 , a housing  40 , a stator core  42 , coils  44 , the hub  50 , a yoke  52 , a magnet  54 , a sleeve  60 , and a cap  62 . The base  20 , the shaft  30 , the housing  40 , the stator core  42 , and the coils  44  form an example stationary body. In addition, the hub  50 , the yoke  52 , and the magnet  54  form an example rotating body, and the sleeve  60  is an example bearing body. Still further, the shaft  30  and the housing  40  form an example shaft body. The bearing body and the shaft body are rotatable relative to each other, and form a bearing unit. 
     In the disk drive device  100 , a lubricant  70  is applied between the shaft  30  and the sleeve  60 , and between the housing  40  and the sleeve  60 , and the sleeve  60  is freely rotatable relative to the stationary body like the shaft  30  together with the hub  50  fixed to and supported by the sleeve  60 . 
     (Base) 
     The base  20  includes a protruding portion  20 D protruding from the bottom cylindrically around the rotation axis R as viewed from the top. The protruding portion  20 D protrudes upwardly toward the hub  50  from the bottom, and the stator core  42  is fixed to the outer circumference of the protruding portion  20 D. The base  20  is formed with a center hole  20 E along the inner circumference of the protruding portion  20 D around the rotation axis R, and the center hole  20 E fixes and supports the housing  40 . 
     The base  20  may have an inner area including the protruding portion  20 D and an outer area encircling the inner area, the inner area and the outer area being formed as separate bodies. In this case, it is desirable that the inner area should be formed of a material having a higher Young&#39;s modulus than that of the material forming the outer area. In this case, the boundary between the inner area and the outer area is provided at, for example, the outer circumference side from the outer edge of the hub  50 . 
     (Shaft) 
     The shaft  30  includes the retainer hole  30 A and a top flange  30 B at an upper-end side, and has the lower end fixed to a shaft hole  40 A of the housing  40  by, for example, interference fitting. As to the interference fitting, for example, the shaft  30  is fitted in the shaft hole  40 A by press-fitting or thermal insert. Alternatively, the shaft  30  is fitted by cooling fit of letting the shaft  30  cooled by a liquid nitrogen, fitted in the shaft hole  40 A and returned to a normal temperature. In the interference fitting of the shaft  30  with the shaft hole  40 A of the housing  40 , bonding may be also applied. 
     The shaft  30  is formed in a substantially cylindrical shape by cutting or grinding of a ferrous material like stainless-steel, such as SUS 420 J2, SUS 430, or SUS 303. The shaft  30  may be quenched to increase the hardness, and the outer circumference and the lower face of the top flange  30 B may be polished to improve the dimensional precision. In addition, the shaft  30  may be formed of other materials like a resin, or may be formed by other techniques, such as pressing or molding. 
     The retainer hole  30 A is provided in the upper end of the shaft  30 , and retains thereinside the center screw  12  that is a fastener holding the top cover  10 . For example, the center screw  12  is engaged with a female screw formed in the retainer hole  30 A, thereby being joined with the shaft  30 . 
     The top flange  30 B is provided at the upper-end side of the shaft  30 , and is formed in an annular shape as viewed from the top. In this embodiment, the shaft  30  and the top flange  30 B are formed integrally with each other, and may formed as separate pieces and joined together by, for example, bonding. 
     (Housing) 
     The housing  40  includes the shaft hole  40 A into which the shaft  30  is fitted, a support portion  40 B fixing and supporting the shaft  30 , and an annular portion  40 C protruding upwardly from the outer circumference of the support portion  40 B and encircling the lower end of the sleeve  60 . 
     The housing  40  has the support portion  40 B and the annular portion  40 C formed integrally with each other. Since both portions are integrated together, the manufacturing error of the housing  40  can be reduced, and a joining work can be omitted. In addition, a deformation of the housing  40  relative to a shock load can be suppressed. However, the housing  40  can be formed by joining multiple pieces in accordance with the application of the disk drive device  100  and the restriction over designing, etc. 
     The housing  40  is formed by cutting of a metal material like stainless-steel, such as SUS 430, or a brass. However, the housing  40  can be formed of other materials like a resin and may be formed by other techniques, such as pressing and molding in accordance with the application of the disk drive device  100  and the restriction over designing, etc. 
     (Stator Core) 
     The stator core  42  includes an annular portion, and, for example, 12 salient poles extending from the annular portion outwardly in the radial direction. The stator core  42  can be formed by, for example, laminating and caulking 5 to 30 magnetic steel sheets each having a thickness of, for example, 0.2 to 0.35 mm. An insulation coating, such as electrodeposition coating or powder coating, is applied to the surface of the stator core  42 . Note that the stator core  42  may be a solid core formed by conjugating magnetic powders in a predetermined shape. 
     The stator core  42  is fixed and supported by the stationary body. In this embodiment, the stator core  42  has the lower end of the inner circumference of the annular portion joined with a step provided on the protruding portion  20 D of the base  20  by press-fitting, bonding or a combination thereof. In addition, the inner circumference of the annular portion of the stator core  42  may be bonded and fixed to the outer circumference of the annular portion  40 C of the housing  40 . According to the structure in which the stator core  42  is fixed to both of the base  20  and the housing  40 , the annular portion of the stator core  42  is fixed and supported with a wide area in the axial direction, and thus a vibration of the stator core  42  can be suppressed. 
     (Coil) 
     The coil  44  is formed by winding a conductor wire around each salient pole of the stator core  42  by a predetermined number of turns. The conductor wire is, for example, a core wire like soft copper having a surface coated with an insulation layer like an urethane resin. A lubrication substance to reduce the friction resistance is applied to the surface of the conductor wire. The lubrication substance is, for example, polyamide compound. 
     The coils  44  are electrically connected to the conductor wire of an unillustrated flexible printed circuit board provided on the upper face or the back face of the bottom plate  20 A of the base  20 . When drive currents are caused to flow through the coils  44  from an unillustrated drive circuit through the flexible printed circuit board, magnetic fields are generated along the salient poles. 
     (Hub) 
     The hub  50  includes a center hole  50 A, a cylindrical portion  50 B, a mount portion  50 C, and a step portion  50 D. The magnetic recording disks  24  are to be mounted on the mount portion  50 C, and the sleeve  60  is fitted in the center hole  50 A. Hence, the hub  50  is freely rotatable around the rotation axis R together with the sleeve  60 . 
     The center hole  50 A is a through-hole in the axial direction around the rotation axis R, and the upper end of the sleeve  60  is fitted therein through the lower opening. The cylindrical portion  50 B is formed annularly at the outer circumference of the hub  50 , and is engaged with the engagement hole of the magnetic recording disk  24 . The mount portion  50 C is formed annularly so as to protrude outwardly in the radial direction from the lower end of the cylindrical portion  50 B, and the multiple magnetic recording disks  24  are mounted on the mount portion  50 C with the spacers  25  being present therebetween. The magnetic recording disks  24  are held between the clamper  26  and the mount portion  50 C, thereby being fixed to the cylindrical portion  50 B with the spacers  25 . The step  50 D is provided annularly at the lower opening of the center hole  50 A, and is formed as a step abutting a flange  60 A of the sleeve  60  fitted in the center hole  50 A to support the sleeve  60 . When the lower face of the step  50 D abuts and is engaged with the upper face of the flange  60 A of the sleeve  60 , the hub  50  and the sleeve  60  are fixed together with both components being positioned. That is, the hub  50  is formed so as to maintain the position of the bearing unit in the axial direction relative to the sleeve  60  by the weight of the hub  50 . 
     The hub  50  is formed of a non-ferrous material like an aluminum alloy, a ferrous material like stainless-steel, or a resin material like LCP (Liquid Crystal Polymer), or, a composite material thereof. In addition, the hub  50  may have a surface layer like plating or coating. Such a surface layer suppresses a peeling of fine residues sticking to the processed face of the hub  50 . 
     In this case, an airflow generating portion may be provided between the lower face of the mount portion  50 C of the hub  50  and the base  20 . In this case, airflow generating grooves in, for example, herringbone shape or spiral shape are formed in the lower face of the mount portion  50 C of the hub  50  or the upper face of the base  20  facing the mount portion  50 C. The airflow generating grooves are formed so as to generate airflow of directing a gas present between the mount portion  50 C of the hub  50  and base  20  to the interior side when the hub  50  rotates. For example, according to such airflow generating grooves, a dispersion of the lubricant  70  toward the disk retaining space  28  can be suppressed. 
     (Spacer) 
     As explained above, the multiple magnetic recording disks  24  are fixed between the clamper  26  and the mount portion  50 C of the hub  50  with the spacers  25  being present therebetween. The spacer  25  separates the two magnetic recording disks  24  in the axial direction. The spacer  25  is formed in a hollow ring shape, and has the hollow portion engaged with the cylindrical portion  50 B of the hub  50 . The spacer  25  is formed by, for example, cutting a ferrous material like stainless-steel SUS 303. 
     (Clamper) 
     The clamper  26  is formed in a substantially hollow disk shape, and is formed by, for example, cutting a ferrous material like stainless-steel SUS 303. The clamper  26  is fixed to the upper face of the hub  50  by, for example, a clamper screw  27 , and the lower face of the circumference of the clamper  26  abuts the upper face of the uppermost magnetic recording disk  24 , thereby fixing the magnetic recording disks  24  to the cylindrical portion  50 B of the hub  50 . 
     (Yoke) 
     The yoke  52  is formed in a substantially cylindrical shape around the rotation axis R, and is bonded to and fixed to the inner circumference of the cylindrical portion  50 B of the hub  50 . The yoke  52  is formed by pressing or cutting, etc., of a ferrous material with soft magnetism. In addition, plating or coating may be applied to the surface of the yoke  52 . The magnet  54  is fixed to the inner circumference of the yoke  52 . 
     (Magnet) 
     The magnet  54  is formed in a substantially cylindrical shape around the rotation axis R, and has the outer circumference fixed to the inner circumference of the yoke  52  by, for example, bonding. The magnet  54  is formed of, for example, a ferrite-based magnetic material or a rare-earth-material-based magnetic material, and contains a resin like polyamide as a binder. The magnet  54  may be formed of a lamination of, for example, a ferrite-based magnetic layer and a rare-earth-material-based magnetic layer. 
     The magnet  54  has, for example, 8 or 16 magnetic poles formed in the inner circumference in the circumferential direction, and those magnetic poles are provided so as to face the outer circumferences of the salient poles of the stator core  42  with a gap in the radial direction. 
     A surface layer like electrodeposition coating or spray coating is applied to the surface of the magnet  54 . Such a surface layer suppresses an oxidization of the magnet  54  and a peeling of the surface. 
     (Sleeve) 
     The sleeve  60  is an annular member that retains at least a part of the shaft body including the shaft  30 , the top flange  30 B, and the housing  40  in a manner freely rotatable, and is sometimes referred to as a bearing body in the following explanation. The sleeve  60  encircles the upper-end portion of the shaft  30 , and is freely rotatable relative to the shaft  30  and the housing  40  together with the hub  50  supported by and fixed to the sleeve  60 . 
     The center hole  50 A of the hub  50  has an internal diameter larger than an outer diameter of the portion of the sleeve  60  fitted in the center hole  50 A, and the sleeve  60  is fitted in the center hole  50 A of the hub  50  by loose fit. When the hub  50  and the sleeve  60  are joined by loose fit, in comparison with interference fitting, a deformation of the hub  50  and that of the sleeve  60  can be suppressed, thus making the operation of the disk drive device  100  stable. 
     Provided on the outer circumference of the sleeve  60  is the annular flange  60 A protruding outwardly in the radial direction and abutting and being engaged with the step  50 D provided along the lower open end of the center hole  50 A of the hub  50 . The sleeve  60  is inserted in the center hole  50 A of the hub  50  from the upper end of the sleeve  60  until the flange  60 A abuts and is engaged with the step  50 D. A bond is applied to at least either one of the inner circumference of the center hole  50 A of the hub  50  and the portion of the sleeve  60  fitted in the center hole  50 A, and the hub  50  and the sleeve  60  are fixed together by bonding. Since the step  50 D of the hub  50  and the flange  60 A of the sleeve  60  abut and are engaged with each other, the hub  50  and the sleeve  60  can be maintained at predetermined positions until the bond is cured. 
     According to this embodiment, since the hub  50  and the sleeve  60  are fixed together by loose fitting and bonding, a deformation of the hub  50  and that of the sleeve  60 , etc., can be suppressed. In addition, since the step  50 D of the hub  50  and the flange  60 A of the sleeve  60  abut and are engaged with each other, the hub  50  and the sleeve  60  are held at predetermined positions even if no jig to maintain the position of the hub  50  is utilized. Hence, in comparison with a case in which no step and no flange are provided and the hub  50  and the sleeve  60  are held at predetermined positions using a jig, etc., maintaining the position of the hub  50  until the bond is cured, attachment and detachment of the jig can be eliminated, and thus a reduction of the production efficiency can be avoided. 
     The shape of the step  50 D of the hub  50  and that of the flange  60 A of the sleeve  60  may be different shapes from those of this embodiment as long as the sleeve  60  can support the hub  50 . 
     The sleeve  60  includes, in addition to the flange  60 A, a shaft encircling portion  60 B, a shaft hole  60 C, a flange encircling portion  60 D, a seal portion  60 E, and a communication channel  60 F. 
     The shaft encircling portion  60 B encircles, in the axial direction from the upper face of the support portion  40 B of the housing  40  to the lower end of the top flange  30 B of the shaft  30 , the shaft  30  fitted in the shaft hole  60 C. The shaft  30  is fitted in the shaft hole  60 C. The flange encircling portion  60 D protrudes upwardly from the circumference of the upper end of the shaft encircling portion  60 B, and encircles the top flange  30 B of the shaft  30 . The seal portion  60 E is a tapered face provided in the outer circumference of the lower end side of the shaft encircling portion  60 B, and seals the lubricant  70  with the annular portion  40 C of the housing  40 . The seal portion  60 E is formed so as to increase the gap with the annular portion  40 C of the housing  40  toward the upper space. The communication channel  60 F causes a space between the top flange  30 B and the upper face of the shaft encircling portion  60 B and a space between the upper face of the support portion  40 B of the housing  40  and the lower face of the shaft encircling portion  60 B to be in communication with each other, and reduces a pressure difference applied to the lubricant  70  in an area where the lubricant  70  is present. 
     The sleeve  60  is formed by, for example, cutting and machining a metal like stainless-steel SUS 430 or brass. The sleeve  60  may have a surface layer formed by, for example, electroless nickel plating. 
     According to this embodiment, each component of the sleeve  60  are integrally formed, but each component may be formed separately and then joined together as needed. For example, the sleeve  60  may have an internal component retaining the shaft  30  and an external component joined with the hub  50 , and the internal component and the external component may be formed separately and then joined together. 
     (Lubricant and Sealing Structure) 
     Predetermined gaps are formed between the shaft body and the bearing body so as to apply the lubricant. In this embodiment, the lubricant  70  is applied between the shaft  30  and the sleeve  60 , between the housing  40  and the sleeve  60 , and in the communication channel  60 F of the sleeve  60 . The lubricant  70  contains a base oil to which a fluorescent material is added. Hence, when the lubricant  70  leaks from the gap between the components, if light with a predetermined wavelength is emitted, such a leakage can be easily detected. 
     The top flange  30 B has the upper-end side face tapered so as to increase a gap with the inner circumference of the flange encircling portion  60 D toward the upper space. As a result, provided between the upper-end side face of the top flange  30 B of the shaft  30  and the inner circumference of the flange encircling portion  60 D of the sleeve  60  is a first tapered space increasing the gap in the radial direction toward the upper space. In the first tapered space, a first gas-liquid interface  71  of the lubricant  70  is formed. In the first tapered space between the upper-end side face of the top flange  30 B and the inner circumference of the flange encircling portion  60 D of the sleeve  60 , force by a capillary phenomenon acts on the lubricant  70  toward the bottom direction where the gap becomes narrow, and thus the lubricant  70  is retained between the shaft  30  and the sleeve  60 . 
     In a part of the inner circumference of the flange encircling portion  60 D of the sleeve  60  facing the side face of the top flange  30 B of the shaft  30 , first pump seal grooves  60 G in a herringbone shape, a spiral shape, etc., are formed. The first pump seal grooves  60 G generate dynamic pressure to cause the lubricant  70  to flow downwardly, thereby suppressing a rise of the first gas-liquid interface  71  of the lubricant  70  and a leakage of the lubricant  70 . The first pump seal grooves  60 G may be formed in the side face of the top flange  30 B of the shaft  30 . 
     The seal portion  60 E of the sleeve  60  is, as explained above, formed in a tapered shape increasing the gap with the inner circumference of the annular portion  40 C of the housing  40  toward the upper space. As a result, provided between the inner circumference of the annular portion  40 C of the housing  40  and the seal portion  60 E of the sleeve  60  is a second tapered space increasing the gap in the radial direction toward the upper space. A second gas-liquid interface  72  of the lubricant  70  is formed in the second tapered space. In the second tapered space between the inner circumference of the annular portion  40 C of the housing  40  and the seal portion  60 E of the sleeve  60 , force by a capillary phenomenon acts on the lubricant  70  toward the bottom direction where the gap becomes narrow, and thus the lubricant  70  is retained between the housing  40  and the sleeve  60 . 
     In addition, provided in the outer circumference of the lower face of the shaft encircling portion  60 B of the sleeve  60  are second pump seal grooves  60 H formed in a herringbone shape or spiral shape, etc. The second pump seal grooves  60 H generate dynamic pressure causing the lubricant  70  to flow to the internal side, thereby suppressing a rise of the second gas-liquid interface  72  of the lubricant  70  and a leakage of the lubricant  70 . The second pump seal grooves  60 H may be provided in the upper face of the support portion  40 B of the housing  40 . 
     (Cap) 
     The sleeve  60  is provided with the cap  62  in a substantially cylindrical shape having the circumference engaged with the outer circumference of the flange encircling portion  60 D of the sleeve  60 . The cap  62  covers the first gas-liquid interface  71  formed between the top flange  30 B of the shaft  30  and the flange encircling portion  60 D of the sleeve  60 , and prevents the lubricant  70  from splashing in the device. The cap  62  is formed by, for example, cutting and machining of a ferrous material or a resin material. 
     (Dynamic Pressure Generating Portion) 
     At least either one of the shaft body and the bearing body is provided with radial dynamic pressure generating grooves that generate dynamic pressure to the lubricant. In this embodiment, between the outer circumference of the shaft  30  and the inner circumference of the shaft encircling portion  60 B of the sleeve  60 , a first radial dynamic pressure generating portion  81  and a second radial dynamic pressure generating portion  82  are formed at the upper end side of the shaft  30  and the lower end side thereof, respectively. The first radial dynamic pressure generating portion  81  and the second radial dynamic pressure generating portion  82  are provided so as to be spaced apart from each other in the axial direction. 
     Provided in the inner circumference of the shaft encircling portion  60 B of the sleeve  60  at a location corresponding to the first radial dynamic pressure generating portion  81  are first radial dynamic pressure generating grooves  60 I in a herringbone shape or spiral shape, etc. In addition, provided in the inner circumference of the shaft encircling portion  60 B of the sleeve  60  at a location corresponding to the second radial dynamic pressure generating portion  82  are second radial dynamic pressure generating grooves  60 J in a herringbone shape or spiral shape, etc. Either one of or both of the first radial dynamic pressure generating grooves  60 I and the second radial dynamic pressure generating grooves  60 J may be provided in the outer circumference of the shaft  30 . 
     Thrust dynamic pressure generating grooves that generate dynamic pressure to the lubricant are provided in either one of the shaft body and the bearing body. In this embodiment, a first thrust dynamic pressure generating portion  83  is provided between the lower face of the top flange  30 B of the shaft  30  and the upper face of the shaft encircling portion  60 B of the sleeve  60 . First thrust dynamic pressure generating grooves  60 K in a herringbone shape or spiral shape are formed in the upper face of the shaft encircling portion  60 B of the sleeve  60 . The first thrust dynamic pressure generating grooves  60 K may be provided in the lower face of the top flange  30 B of the shaft  30 . 
     In addition, a second thrust dynamic pressure generating portion  84  is provided between the upper face of the support portion  40 B of the housing  40  and the lower face of the shaft encircling portion  60 B of the sleeve  60 . Second thrust dynamic pressure generating grooves  60 L in a herringbone shape or spiral shape, etc., are provided in the lower face of the shaft encircling portion  60 B of the sleeve  60  at the inner-circumference side. The second thrust dynamic pressure generating grooves  60 L may be provided in the upper face of the support portion  40 B of the housing  40 . 
     When the sleeve  60  rotates together with the hub  50  relative to the shaft  30 , the first and second radial dynamic pressure generating portions  81 ,  82 , and the first and second thrust dynamic pressure generating portions  83 ,  84  generate respective dynamic pressures to the lubricant  70 . The sleeve  60  is supported by the dynamic pressures to the lubricant  70  in the axial direction and the radial direction in a non-contact manner with the shaft  30  and the housing  40 , and rotates. 
     The first and second radial dynamic pressure generating grooves  60 I,  60 J, and the first and second thrust dynamic pressure generating grooves  60 K,  60 L are formed by, for example, pressing, ball rolling, electro-chemical machining, and cutting and machining that controls the position of a cutting tool with a piezoelectric element, but may be individually formed through different techniques. 
     (Manufacturing Process) 
     Next, an explanation will be given of a manufacturing process of the disk drive device  100 . 
     First, the lower end of the shaft  30  is fitted in the shaft hole  60 C of the sleeve  60 , the housing  40  is fixed to the lower end of the shaft  30 , and the lubricant  70  is applied. Next, the cap  62  is fixed to the upper end of the sleeve  60 . The shaft  30  and the housing  40 , the sleeve  60  and the cap  62 , and, the base  20  and the housing  40  are fixed by press-fitting, bonding or a combination thereof, respectively. As a result, a bearing unit is manufactured. 
     In addition, the yoke  52  and the magnet  54  are bonded and fixed to the lower face of the hub  50 . Next, a bond like a curable resin is applied to at least either one of the inner circumference of the center hole  50 A of the hub  50  and the outer circumference of the sleeve  60 . Subsequently, until the flange  60 A of the sleeve  60  abuts the step  50 D of the hub  50 , the sleeve  60  is inserted in the center hole  50 A of the hub  50  from the upper end of the sleeve  60 . 
     With the step  50 D of the hub  50  and the flange  60 A of the sleeve  60  abutting with each other and the hub  50  being supported by the sleeve  60 , ultraviolet rays are emitted to the hub  50  and the sleeve  60 . The bond applied to the respective components and the bond, etc., pushed out from the gap between the center hole  50 A of the hub  50  and the outer circumference of the sleeve  60  are tentatively cured by emitted ultraviolet rays. 
     Furthermore, the support portion  40 B of the housing  40  is bonded and fixed to the center hole  20 E of the base  20  to which the stator core  42  and the coils  44  are bonded and fixed. 
     Subsequently, the disk drive device  100  are left in a high-temperature bath at a temperature of, for example, 80 to 100 degrees for one to three hours, and when the bond is permanently cured, the respective components are completely fixed. 
     The above-explained manufacturing process is merely an example, and the disk drive device  100  can be manufactured through different manufacturing processes. For example, at least one step in the insertion of the shaft  30 , the fixing of the housing  40 , the application of the lubricant  70 , and the fixing of the cap  62  may be carried out after the sleeve  60  is bonded to the hub  50 . 
     Still further, the disk drive device  100  is assembled with the magnetic recording disks  24 , the clamper  26 , and the data reader/writer  22 , etc., and the top cover  10  is fixed to the upper face of the base  20 . At this time, the disk retaining space  28  is filled with clean gas having dusts, etc., eliminated, and is air-tightly sealed. 
     After the above-explained processes, the disk drive device  100  is thus manufactured through predetermined performance inspection processes. The sequence of the above-explained processes can be changed as needed. 
     As explained above, according to the disk drive device  100  of the first embodiment, the hub  50  and the sleeve  60  are bonded and fixed by loose fit, and thus a deformation of the hub  50  and that of the sleeve  60  can be suppressed. In addition, since the hub  50  and the sleeve  60  are fixed with the step  50 D of the hub  50  and the flange  60 A of the sleeve  60  abutting and being engaged with each other, the positional precision of the hub  50  and the sleeve  60  can be maintained even if no jig, etc., to maintain the position of the hub  50  is utilized in the assembling. As explained above, a deformation of the hub  50  and that of the sleeve  60  are suppressed, and the positional precision thereof at the time of assembling are ensured without decreasing the production efficiency. Therefore, the disk drive device  100  that improves the operation stability can be provided. 
     Second Embodiment 
     Next, an explanation will be given of a second embodiment of the present disclosure with reference to the drawings. The same structural component as that of the above-explained embodiment will be denoted by the same reference numeral, and the duplicated explanation thereof will be omitted. 
       FIG. 3  is a general structural diagram illustrating an example disk drive device  200  of the second embodiment. In  FIG. 3 , the left part relative to the rotation axis R of the A-A cross section in  FIG. 1  is illustrated, and the top cover  10 , the magnetic recording disks  24 , the spacer  25 , and the clamper  26 , etc., are omitted. 
     According to the disk drive device  200  of the second embodiment, the step  50 E of the hub  50  is provided at the upper opening of the center hole  50 A. In addition, a flange  60 M that is a supporting portion of the sleeve  60  is provided so as to protrude outwardly in the radial direction from the outer circumference of the upper-end-side portion of the sleeve  60 . The flange  60 M is provided so as to protrude outwardly in the radial direction between the upper end of the shaft encircling portion  60 B and the lower end portion of the flange encircling portion  60 D in the outer circumference of the sleeve  60 . 
     The inner diameter of the center hole  50 A of the hub  50  is larger than the outer diameter of the portion of the sleeve  60  fitted in the center hole  50 A of the hub  50 , and the hub  50  and the sleeve  60  are fixed by loose fit. As to the hub  50  and the sleeve  60 , first, a bond is applied to at least either one of the inner circumference of the center hole  50 A of the hub  50  and the outer circumference of the sleeve  60 . Next, the sleeve  60  is fitted in the center hole  50 A of the hub  50  from the lower end of the sleeve  60  until the step  50 E and the flange  60 M abut and are engaged with each other. Hence, the hub  50  and the sleeve  60  are fixed at a predetermined position. Subsequently, the shaft  30  is fitted in the shaft hole  60 C of the sleeve  60  from the lower end of the shaft  30 , the housing  40  is fixed to the lower end of the shaft  30 , and the lubricant  70  is applied. In addition, the cap  62  is fixed to the upper end of the sleeve  60 . 
     As explained above, according to the second embodiment, the hub  50  and the sleeve  60  can be fixed with an excellent positional precision although no jig, etc., to maintain the position of the hub  50  is used. Therefore, the disk drive device  200  that has the operation stability improved can be provided without decreasing the production efficiency. 
     Third Embodiment 
     Next, a third embodiment of the present disclosure will be explained with reference to the drawings. The same structural component as that of the above-explained embodiment will be denoted by the same reference numeral, and the duplicated explanation thereof will be omitted. 
       FIG. 4  is a general structural diagram illustrating an example disk drive device  300  of the third embodiment. In  FIG. 4 , the left part relative to the rotation axis R in the A-A cross section of  FIG. 1  is illustrated, and the top cover  10 , the magnetic recording disks  24 , the spacer  25 , the clamper  26 , etc., are omitted. 
     According to the disk drive device  300  of the third embodiment, a support portion  60 N protruding outwardly in the radial direction from the outer circumference of the sleeve  60  is provided on the upper part of the annular portion  40 C of the housing  40  in the axial direction. 
     The support portion  60 N of the sleeve  60  includes a flange  60 N 1  protruding outwardly in the radial direction from the outer circumference of the sleeve  60 , and an annular portion  60 N 2  extending toward the hub  50  from the outer circumference of the flange  60 N 1  in the direction of the rotation axis. In addition, the hub  50  includes an annular groove  50 F provided around the lower opening of the center hole  50 A and engaged with the annular portion  60 N 2  of the support portion  60 N. 
     The internal diameter of the center hole  50 A of the hub  50  is larger than the outer diameter of the portion of the sleeve  60  fitted in the center hole  50 A of the hub  50 , and the hub  50  and the sleeve  60  are fixed together by loose fit. As to the hub  50  and the sleeve  60 , first, a bond is applied to at least either one of the inner circumference of the center hole  50 A of the hub  50  and the outer circumference of the sleeve  60 . Next, the sleeve  60  is inserted in the center hole  50 A of the hub  50  from the upper end of the sleeve  60  until the annular portion  60 N 2  of the support portion  60 N is engaged and fitted with the annular groove  50 F. Hence, the hub  50  and the sleeve  60  are fixed at a predetermined position. 
     As explained above, according to the third embodiment, the hub  50  and the sleeve  60  can be fixed with an excellent positional precision although no jig, etc., to maintain the position of the hub  50  is used. Therefore, the disk drive device  300  that has the operation stability improved can be provided without decreasing the production efficiency. 
     The support portion  60 N may be provided at the upper-end side of the sleeve  60 , and the annular portion  60 N 2  may extend downwardly from the outer circumference of the flange  60 N 1 . In this case, the annular groove  50 F to be engaged with the annular portion  60 N 2  is provided around the upper opening of the center hole  50 A of the hub  50 . According to such a structure, the sleeve  60  is inserted in the center hole  50 A of the hub  50  from the lower end of the sleeve  60  until the annular portion  60 N 2  of the support portion  60 N is engaged and fitted with the annular groove  50 F. When the annular groove  50 F and the annular portion  60 N 2  abut and are engaged with each other, the hub  50  and the sleeve  60  are fixed at a predetermined position. 
     Fourth Embodiment 
     Next, an explanation will be given of a fourth embodiment of the present disclosure with reference to the drawings. The same structural component as that of the above-explained embodiment will be denoted by the same reference numeral, and the duplicated explanation thereof will be omitted. 
       FIG. 5  is a general structural diagram of a disk drive device  400  of the fourth embodiment. In  FIG. 5 , the left part relative to the rotation axis R in the A-A cross section of  FIG. 1  is illustrated, and the top cover  10 , the magnetic recoding disks  24 , the spacer  25 , the clamper  26 , etc., are omitted. 
     The sleeve  60  includes a support portion  60 P protruding outwardly in the radial direction from the outer circumference of the sleeve  60 . The support portion  60 P includes a tapered supporting inclined face  60 Q inclined relative to the rotation axis R. In addition, the center hole  50 A of the hub  50  where the sleeve  60  is fitted includes an abutting inclined face  50 G in a tapered shape inclined along the supporting inclined face  60 Q. 
     As to the hub  50  and the sleeve  60 , first, a bond is applied to at least either one of the abutting inclined face  50 G of the hub  50  and the supporting inclined face  60 Q of the sleeve  60 . Next, the sleeve  60  is inserted in the center hole  50 A of the hub  50  from the lower end of the sleeve  60  until the abutting inclined face  50 G and the supporting inclined face  60 Q abut and are engaged with each other. Hence, the hub  50  and the sleeve  60  are fixed at a predetermined position. 
     As explained above, according to the fourth embodiment, the hub  50  and the sleeve  60  can be fixed with an excellent positional precision although no jig, etc., to maintain the position of the hub  50  is used. Therefore, the disk drive device  400  that has the operation stability improved can be provided without decreasing the production efficiency. 
     The abutting inclined face  50 G and the supporting inclined face  60 Q may be provided so as to be inclined in opposite directions to those of this embodiment. In this case, as to the hub  50  and the sleeve  60 , the sleeve  60  is inserted in the center hole  50 A of the hub  50  from the upper end of the sleeve  60  until the abutting inclined face  50 G and the supporting inclined face  60 Q abut and are engaged with each other. Hence, the hub  50  and the sleeve  60  are fixed at a predetermined position. 
     Rotating devices according to the embodiments were explained above, but the present disclosure is not limited to the aforementioned embodiments, and permit various modifications and improvements without departing from the scope of the present disclosure.