JP2007263225A - Fluid bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To contribute to higher rotating accuracy and lower cost of a fluid bearing device by improving the fixing accuracy and fastening strength of a hub portion relative to a shaft portion. <P>SOLUTION: The hub portion 9 into which the shaft portion 2 is inserted is injection molded of a resin composition using polyphenylene sulfide (PPS) as a base resin. The hub 9 engages with an outer peripheral face 2a of the shaft portion 2 at its recessed portion 12 provided in a region where it is fixed to the hub portion 9, in the axial and circumferential directions to prevent its come-off and rotation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device.

  The fluid dynamic bearing device supports a rotating member rotatably with a lubricating film of fluid generated in a bearing gap by relative rotation between the bearing member and the rotating member. This hydrodynamic bearing device has characteristics such as high-speed rotation, high rotation accuracy, and low noise. In recent years, by utilizing the characteristics, information devices such as magnetic disk devices such as HDD and FDD, CD-ROM, CD It is widely used as a bearing for a spindle motor mounted on a disk device such as an optical disk device such as R / RW or DVD-ROM / RAM, or a magneto-optical disk device such as MD or MO.

  This type of hydrodynamic bearing includes a hydrodynamic bearing provided with dynamic pressure generating means for generating dynamic pressure in a fluid (for example, lubricating oil) in a bearing gap, and a so-called circular bearing (not provided with dynamic pressure generating means). The bearing surface is roughly divided into a bearing having a perfect circular shape.

  For example, in the hydrodynamic bearing device incorporated in the above spindle motor, a radial bearing portion that supports a shaft portion (shaft member) constituting the rotating member in the radial direction is provided, and the radial bearing portion is configured by a dynamic pressure bearing. There are many cases. In addition, this type of hydrodynamic bearing device is provided with a thrust bearing portion that supports the rotating member in the thrust direction. As the thrust bearing portion, a hydrodynamic bearing is used, and one end of the shaft portion is contact-supported. A structure bearing (so-called pivot bearing) may be used.

The spindle motor is provided with a hub portion (disc hub) for supporting the disc. The hub portion is formed of a metal material that is separate from the shaft portion, and is fixed to one end outer diameter side of the shaft portion by appropriate means such as press-fitting, welding, shrink fitting, or plastic flow processing. Further, a clamper that clamps the disk between the hub portion and the hub portion is fixed to the shaft portion, and this clamper is screwed and fixed to, for example, a screw hole provided on the inner diameter side of the fixing portion with the hub portion of the shaft portion. (See, for example, Patent Document 1).
JP 2000-235766 A

  With the recent increase in capacity of disk devices, the recording / reproducing density of disks has been increasing. Along with this, high rotational accuracy without shaft runout is required for a hydrodynamic bearing device for a spindle motor. Also, in a hydrodynamic bearing device mounted on a disk device such as an HDD, high fastening strength is also required between the hub portion and the shaft portion on which the disk is mounted so that high rotational accuracy of the disk can be maintained.

  In the conventional configuration, the thickness of the region of the shaft portion serving as the fixing portion of the hub portion is thin because a screw hole is provided on the inner diameter side thereof. Therefore, when fixing with a method that involves press-fitting, such as press-fitting or plastic flow processing, the fixed part may be deformed with press-fitting, and high-temperature heating is required, such as welding or shrink fitting. When fixing by the method, there is a risk of thermal deformation. Therefore, in the conventional configuration, it is difficult to ensure the assembly accuracy and fastening strength of the hub portion with respect to the shaft portion and meet the demand for higher rotational accuracy.

  On the other hand, with the recent price reduction of disk devices, the demand for cost reduction for hydrodynamic bearing devices has become more severe.

  An object of the present invention is to increase the assembly accuracy and fastening strength of the hub portion with respect to the shaft portion, and to increase the rotational accuracy of the hydrodynamic bearing device. Another object of the present invention is to reduce the cost of the hydrodynamic bearing device.

  In order to solve the above problems, a hydrodynamic bearing device according to the present invention includes a bearing member, a rotating member that rotates relative to the bearing member, and a lubricating film for fluid generated in a radial bearing gap between the bearing member and the rotating member. A radial bearing portion that rotatably supports the rotating member in the radial direction, and the rotating member is inserted into the inner periphery of the bearing member, and has a shaft portion having a screw hole at one end, and an outer peripheral surface of the shaft portion. A hub portion fixed to the outer diameter side of the screw hole, and the hub portion is injection-molded with resin by inserting the shaft portion, and the hub portion is, of the outer peripheral surface of the shaft portion, The concave portion provided in the fixing region with the hub portion is engaged with the shaft portion in the axial direction and the circumferential direction. Examples of the hub portion here include a disk hub or a turntable that supports a magnetic disk or the like.

  As described above, when the shaft portion is inserted and the hub portion is injection-molded (insert molding), the assembly accuracy with respect to the shaft portion can be increased only by increasing the mold accuracy. The hub portion is engaged with the shaft portion in the axial direction and the circumferential direction by a recess provided in a fixing region with the hub portion on the outer peripheral surface of the shaft portion, Is prevented from rotating, and the fastening strength with the shaft is increased. Also, with insert molding, the hub part can be molded and assembled in a single process, which reduces manufacturing costs. If resin is used as the injection material, the hub part can be made of metal. Compared with this, weight reduction and cost reduction can be achieved.

  The concave portion provided in the shaft portion can be easily formed by machining such as cutting, for example, from the viewpoint of suppressing machining costs and preventing deformation associated with the formation of the concave portion to increase the assembly accuracy of the hub portion. For example, it can be configured by an annular groove and a flat surface formed in a partial region of the groove bottom surface of the annular groove. Or a recessed part can be comprised by the annular groove | channel and the flat surface formed in the partial area | region of the outer peripheral surface of the axial part connected to this annular groove. When the hub part is injection-molded, the portion that is filled and solidified in the concave part of the shaft part is engaged with both side walls of the annular groove in the axial direction, so that the relative movement of the hub part to both sides in the axial direction is prevented. By being regulated and engaging with the flat surface in the circumferential direction, relative movement of the hub portion relative to both sides in the circumferential direction with respect to the shaft portion is regulated. Accordingly, the hub portion is prevented from coming off and prevented from rotating with respect to the shaft portion at the same time, and the fastening strength between the hub portion and the shaft portion is increased.

  Since the hub part also requires its own strength, the resin used for injection molding is a base resin made of particularly high-strength polyphenylene sulfide (PPS) or liquid crystal polymer (LCP), among resins that can be injection molded. The resin composition is preferably used.

  The hydrodynamic bearing device according to the present invention can be preferably used for a motor having a stator coil and a rotor magnet. In particular, the hydrodynamic bearing device of the present invention has the above-described characteristics, and therefore, a mobile disk device. It can be preferably used for a spindle motor mounted on the motor.

  As mentioned above, according to this invention, the assembly precision and fastening strength of the hub part with respect to a shaft part can be improved, and the high rotational precision of a hydrodynamic bearing device can be achieved. Further, the cost of the hydrodynamic bearing device including the hub portion can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 conceptually shows one configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device (fluid dynamic pressure bearing device) 1 according to the present invention. This spindle motor is used in a disk drive device such as an HDD, and is a stator that is opposed to a hydrodynamic bearing device 1 that rotatably supports a rotating member 3 having a shaft portion 2 via, for example, a radial gap. A coil 4 and a rotor magnet 5 and a bracket 6 are provided. The stator coil 4 is attached to the inner periphery of the bracket 6, and the rotor magnet 5 is attached to the outer periphery of the rotating member 3. The housing 7 of the hydrodynamic bearing device 1 is attached to the inner periphery of the bracket 6. Although not shown, the rotating member 3 holds one or a plurality of disk-shaped information recording media (hereinafter simply referred to as disks) such as magnetic disks. When the stator coil 4 is energized, the rotor magnet 5 is rotated by the electromagnetic force between the stator coil 4 and the rotor magnet 5, and accordingly, the rotating member 3 and the disk held by the rotating member 3 are integrated with the shaft portion 2. Rotate to.

  FIG. 2 shows an example of the hydrodynamic bearing device 1 used in the spindle motor. The hydrodynamic bearing device 1 includes a bearing member 10 and a rotating member 3 that rotates relative to the bearing member 10 as main components. In this embodiment, the bearing member 10 includes a housing 7 and a bearing sleeve 8 held inside the housing 7. For convenience of explanation, the description will be made with the side on which the bottom 7b of the housing 7 is provided as the lower side and the opposite side in the axial direction as the upper side.

  The housing 7 includes a side portion 7a formed in a substantially cylindrical shape with a metal material or a resin material, and a bottom portion 7b that closes the lower end opening of the side portion 7a. A tapered outer wall 7a3 that gradually increases in diameter upward is formed on the outer periphery of the side portion 7a. A step portion 7a4 to which the bottom portion 7b is fixed is formed on the inner diameter side of the lower end of the side portion 7a. Except for this step portion 7a4, the inner peripheral surface 7a1 of the side portion 7a is formed in a straight cylindrical surface having the same diameter. Yes. The bottom portion 7b is fixed to the inner periphery of the step portion 7a4 by an appropriate means such as bonding, press-fitting, press-fitting adhesion, welding, or the like according to the forming material.

  In the housing 7, the entire surface or a partial annular region of the upper end surface 7 a 2 of the side portion 7 a becomes the thrust bearing surface of the first thrust bearing portion T 1. A plurality of dynamic pressure grooves arranged in a spiral shape are formed. The dynamic pressure groove may be formed on the lower end surface 9a1 of the hub portion 9 that faces the upper end surface 7a2 of the housing 7 via the thrust bearing gap. The dynamic pressure groove shape may be formed in a spiral shape or a herringbone shape, for example.

  The bearing sleeve 8 is formed, for example, in a cylindrical shape with a porous body made of sintered metal, in particular, a sintered body of sintered metal mainly composed of copper, and is press-fitted and bonded to a predetermined position on the inner peripheral surface 7a1 of the housing 7. Alternatively, it is fixed by means such as press-fit adhesion. Note that the bearing sleeve 8 can be formed of not only a sintered metal but also a metal material other than a porous body, for example, a soft metal such as brass.

  The inner peripheral surface 8a of the bearing sleeve 8 is provided with two upper and lower regions that are radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2, and are separated from each other in the axial direction. For example, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 as shown in FIG. 3A are formed. The upper dynamic pressure groove 8a1 is formed axially asymmetric with respect to the axial center m (the axial center of the upper and lower inclined groove regions), and the axial dimension X1 of the upper region is lower than the axial center m. It is larger than the axial dimension X2 of the side region. On the other hand, the lower dynamic pressure grooves 8a2 are formed symmetrically in the axial direction, and the axial dimensions of the upper and lower regions thereof are respectively equal to the axial dimension X2. In this case, when the shaft member 2 rotates, the pulling force (pumping force) of the lubricating oil by the dynamic pressure groove is relatively larger in the upper dynamic pressure groove 8a1 than in the lower symmetrical dynamic pressure groove 8a2. As the dynamic pressure groove shape, other known shapes such as a spiral shape can also be formed. Note that one or a plurality of axial grooves 8b1 are formed over the entire length in the axial direction on the outer peripheral surface 8b of the bearing sleeve 8. In this embodiment, the three axial grooves 8b1 are circumferential. It is formed at equal intervals.

  In addition, a thrust bearing surface of the second thrust bearing portion T2 is formed in a part or all of the annular region of the lower end surface 8c of the bearing sleeve 8, and the region serving as the thrust bearing surface includes, for example, FIG. A spiral-shaped dynamic pressure groove 8c1 as shown in FIG. The dynamic pressure groove shape can be formed in a spiral shape or a herringbone shape, for example. Further, the thrust bearing surface (dynamic pressure groove) may be formed on the upper end surface 11a of the flange portion 11 that is opposed to the thrust bearing gap.

  The rotating member 3 includes a shaft portion 2 that is inserted into the inner periphery of the bearing sleeve 8, a hub portion (disc hub) 9 that is insert-molded with resin by inserting the shaft portion 2, and the shaft portion 2. And a flange portion 11 fixed to the lower end of the.

  The shaft portion 2 is formed in a substantially cylindrical shape with a metal material such as stainless steel. A screw hole 2a1 is provided in the inner periphery of the upper end portion of the shaft portion 2a, and a clamper (not shown) that clamps the disk between the hub portion 9 and the screw hole 2a1 is fixed by screwing. Also, a screw hole 2a2 is provided in the inner periphery of the lower end portion of the shaft portion 2, and a metal flange portion 11 is screwed and fixed to prevent the shaft portion 2 from coming off. The outer peripheral surface 2 a of the shaft portion 2 is formed in a smooth cylindrical surface without a dynamic pressure groove or the like except for a region serving as a fixing portion of the hub portion 9.

  A recess 12 as shown in FIGS. 2 and 4 is formed by machining such as cutting in a region of the outer peripheral surface 2a of the shaft portion 2 that serves as a fixing portion of the hub portion 9. Is filled with a resin material constituting the hub portion 9 and solidified. In the present embodiment, the recess 12 is formed in an annular groove 12a provided over the entire circumference in one or a plurality of locations (one location in the illustrated example) in the axial direction, and a partial region of the groove bottom surface of the annular groove 12a. And the formed flat surface 12b. In the present embodiment, the two flat surfaces 12b are formed in a region facing each other by 180 degrees. Each flat surface 12b is formed parallel to the axis. The portion of the hub portion 9 filled and solidified in the recess 12 is engaged with both side walls of the annular groove 12a in the axial direction, so that the relative movement of the hub portion 9 in the axial direction with respect to the shaft portion 2 is restricted. In addition, by engaging the flat surface 12b in the circumferential direction, relative movement of the hub portion 9 to both sides in the circumferential direction with respect to the shaft portion 2 is restricted. As a result, the hub part 9 can be prevented from coming off and prevented from rotating with respect to the shaft part 2 at the same time, and the fastening strength between the hub part 9 and the shaft part 2 can be increased. It should be noted that the depth and axial width of the annular groove 12a and the size of the flat surface 12b do not adversely affect the fastening strength when the clamper is screwed and fixed, and prevent the hub portion 9 from coming off and preventing rotation. It is set so as to be an appropriate value that can be secured (for example, the deepest part is about half the thickness). Further, in the illustrated example, the flat surfaces 12b are provided at two places in the circumferential direction opposed to each other by 180 degrees. However, they can be provided at one place or three places or more in the circumferential direction.

  The hub part 9 includes a disk part 9a disposed above the housing 7, a cylindrical part 9b extending axially downward from the outer peripheral part of the disk part 9a, and a disk mounting surface provided on the outer periphery of the cylindrical part 9b. 9c and a flange 9d. A disk (not shown) is fitted on the outer periphery of the disk portion 9a and placed on the disk mounting surface 9c. Then, the disc is sandwiched between a clamper (not shown).

  The inner peripheral surface 9b1 of the tubular portion 9b of the hub portion 9 is between the outer wall 7a3 of the side portion 7a of the housing 7 and an annular seal space in which the radial dimension is gradually reduced upward from the lower end side of the housing 7. S is formed. The seal space S communicates with the outer diameter side of the thrust bearing gap of the first thrust bearing portion T1 when the rotating member 3 rotates.

  As the resin material for molding the hub portion 9, any resin can be used as long as it can be injected, whether it is a crystalline resin or an amorphous resin. However, polyphenylene sulfide (PPS) or liquid crystal that is particularly high in strength and excellent in dimensional stability. A resin composition having a polymer (LCP) as a base resin is used. If necessary, the base resin may be blended with one or two or more kinds of fillers such as a reinforcing material (in any form such as a fiber or powder) or a conductive material.

  In addition to the above, as the base resin, in addition to crystalline resins such as polyether ether ketone (PEEK) and polybutylene terephthalate (PBT), for example, polysulfone (PSU), polyether sulfone (PES) Amorphous resins such as polyphenylsulfone (PPSU) and polyetherimide (PEI) can also be used. These are only examples of usable base resins, and other known resin materials can of course be used as the base resins.

  Further, if the weight or the like is not particularly a problem, a metal can be used as the injection material. As the metal material, for example, a low melting point metal material such as a magnesium alloy or an aluminum alloy can be used. In this case, the strength can be further improved as compared with the case of using a resin material. In addition, so-called MIM molding may be employed in which after the injection molding with a mixture of metal powder and binder, degreasing and sintering. In addition, ceramics can also be used.

  In the hydrodynamic bearing device 1 having the above-described configuration, when the rotating member 3 rotates, the regions provided separately at the two upper and lower positions serving as the radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8 are the outer peripheral surface 2a of the shaft portion 2 respectively. And through a radial bearing gap. As the rotating member 3 rotates, the lubricating film generated in the radial bearing gap is enhanced in oil film rigidity by the dynamic pressure action of the dynamic pressure groove, and the rotating member 3 is supported in a non-contact manner so as to be rotatable in the radial direction. . As a result, the first radial bearing portion R1 and the second radial bearing portion R2 that support the rotating member 3 in a non-contact manner so as to be rotatable in the radial direction are formed.

  Further, when the rotating member 3 rotates, a region serving as a thrust bearing surface of the upper end surface 7a2 of the housing 7 faces the lower end surface 9a1 of the hub portion 9 via a predetermined thrust bearing gap, and the lower end surface of the bearing sleeve 8 A region serving as a thrust bearing surface of 8c faces the upper end surface 11a of the flange portion 11 via a predetermined thrust bearing gap. As the rotating member 3 rotates, the lubricating oil film formed in both thrust bearing gaps is enhanced in its oil film rigidity by the dynamic pressure action of the dynamic pressure groove, and the rotating member 3 is supported in a non-contact manner so as to be rotatable in both thrust directions. Is done. Thereby, the 1st thrust bearing part T1 and the 2nd thrust bearing part T2 which support the rotation member 3 in the thrust direction so that rotation is possible non-contactingly are formed.

  In this embodiment, since the hub portion 9 is injection-molded by inserting the shaft portion 2, the assembly accuracy with respect to the shaft portion 2 can be increased only by increasing the mold accuracy, and the molding and the assembly are performed in the same process. Since this is possible, the manufacturing cost can be reduced. Further, the shaft portion 2 is provided with a recess 12, the hub portion 9 is engaged with the shaft portion 2 in the axial direction by the annular groove 12 a of the recess 12, and the hub portion 9 is circumferentially connected to the shaft portion 2 by the flat surface 12 b. Since it is engaged in the direction (tangential direction), the hub part 9 is prevented from coming off and prevented from rotating, and the fastening strength between the shaft part 2 and the hub part 9 can be increased.

  In the above description, an example in which the flat surface 12b constituting the concave portion 12 is formed in a partial region of the groove bottom surface of the annular groove 12a that also constitutes the concave portion 12 is illustrated, but for example, as shown in FIG. The surface 12b can also be formed in a partial region of the outer peripheral surface of the shaft portion 2 connected to the annular groove 12a. In this case, in the region where the annular groove 12a is formed, the shaft portion 2 has a perfect circular section, and in the region where the flat surface 12b is formed, the shaft portion 2 has a D-cut shape. In this configuration, compared to the configuration shown in FIG. 4, the flat surface 12b can be provided on the outer diameter side, so that the area of the flat surface can be increased. Can be made strong. In FIG. 5, the flat surface 12b is provided in a region connected to the annular groove 12a. However, as long as the flat surface 12b is in an axial region serving as a fixing portion of the hub portion 9, It can also be provided in regions separated in the axial direction.

  Although one embodiment of the present invention has been described above, the configuration of the present invention can be preferably applied not only to the hydrodynamic bearing device 1 having the above configuration but also to hydrodynamic bearing devices having other configurations. Hereinafter, other configuration examples of the hydrodynamic bearing device will be described, but the same reference numerals are assigned to the components having the same functions and operations as those shown in FIG.

  FIG. 6 shows a second embodiment of the hydrodynamic bearing device 1 according to the present invention. The hydrodynamic bearing device 1 in the illustrated example is an embodiment shown in FIG. 2 in that a bearing member constituted by a separate housing 7 (side 7a) and a bearing sleeve portion 8 is constituted by an integral bearing member 17. And the configuration is different. In this way, by using the bearing member 17 as a single component, the cost can be further reduced by reducing the number of components and the number of assembly steps. In this case, radial bearing portions R1 and R2 are formed between the inner peripheral surface 17a of the bearing member 17 and the outer peripheral surface 2a of the shaft portion 2, and the upper end surface 17b of the bearing member 17 and the lower end surface 9a1 of the hub portion 9 Thrust bearing portions T1 and T2 are formed between the lower end surface 17c of the bearing member 17 and the upper end surface 11a of the flange portion 11, respectively.

  FIG. 7 shows a third embodiment of a hydrodynamic bearing device according to the present invention. In the illustrated hydrodynamic bearing device 1, a seal member 19 in which a shaft portion 21 and a flange portion 22 that mainly constitute a rotating member are integrally formed, and a seal space S is fixed to an inner periphery of one end of the housing 7. 2 in that it is formed between the inner peripheral surface 19a of the shaft portion 21 and the outer peripheral surface 21a of the shaft portion 21 and the thrust bearing portion is formed in the thrust bearing gap that faces both end surfaces 22a and 22b of the flange portion 22. The configuration shown in FIG. In this embodiment, the bearing member is composed of a separate housing 7 (side portion 7a) and the bearing sleeve 8. However, like the one shown in FIG. It can also be configured.

  In the above description, the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2 are exemplified by the configuration in which the dynamic pressure action of the lubricating oil is generated by the dynamic pressure grooves having a herringbone shape or a spiral shape. Is not limited to this.

  For example, although illustration is omitted, one or both of the radial bearing portions R1 and R2 are, for example, so-called step bearings or radial bearings in which a plurality of axial grooves are provided at equal intervals in the circumferential direction in a region serving as a radial bearing surface. You may employ | adopt what is called a multi-arc bearing etc. which provided the some circular arc surface in the area | region used as a bearing surface. In addition, one or both of the thrust bearing portions T1 and T2 are, for example, so-called step bearings, so-called wave bearings (step-type bearings) in which a plurality of radial grooves are provided at predetermined intervals in the circumferential direction in a region serving as a thrust bearing surface. May also be used.

  In the above description, the form in which both the first radial bearing portion R1 and the second radial bearing portion R2 are configured by dynamic pressure bearings has been exemplified. However, one of the first radial bearing portion R1 and the second radial bearing portion R2 is exemplified. Alternatively, both may be constituted by a perfect circle bearing (not shown).

  Further, in the above description, the configuration in which the thrust bearing portion is constituted by a dynamic pressure bearing has been exemplified. However, the thrust bearing portion is formed such that one end of the shaft portion 2 has a convex spherical shape, and the shaft end is the bearing member 10 (housing 7). It is also possible to use a so-called pivot bearing that is in contact with and supported by the bottom 7b.

  In the above description, the lubricating oil is exemplified as the fluid that fills the inside of the hydrodynamic bearing device 1, but other than that, for example, a gas such as air, a magnetic fluid, or the like can be used.

It is sectional drawing which shows notionally the spindle motor for disk apparatuses. It is sectional drawing which shows 1st Embodiment of a hydrodynamic bearing apparatus. (A) is a sectional view of the bearing sleeve, and (b) is a view showing a lower end surface of the bearing sleeve. It is an expanded sectional view of the one end part of a shaft part. It is an expanded sectional view which shows the other structural example of the one end part of a axial part. It is sectional drawing which shows 2nd Embodiment of a hydrodynamic bearing apparatus. It is sectional drawing which shows 3rd Embodiment of a hydrodynamic bearing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid bearing apparatus 2 Shaft part 3 Rotating member 7 Housing 8 Bearing sleeve 9 Hub part 10 Bearing member 12 Recess 12a Ring groove 12b Flat surface R1, R2 Radial bearing part T1, T2 Thrust bearing part S Seal space

Claims (5)

The rotating member is rotatably supported in the radial direction by a bearing member, a rotating member that rotates relative to the bearing member, and a fluid lubricating film formed in a radial bearing gap between the bearing member and the rotating member. A radial bearing portion, and the rotating member is inserted into an inner periphery of the bearing member, and has a shaft portion having a screw hole at one end portion, and an outer peripheral surface of the shaft portion on an outer diameter side of the screw hole. In a hydrodynamic bearing device having a fixed hub portion,
The hub portion is injection-molded with resin by inserting the shaft portion, and the hub portion is a recess provided in a fixed region with the hub portion on the outer peripheral surface of the shaft portion. And a hydrodynamic bearing device that is engaged in a circumferential direction.   The hydrodynamic bearing device according to claim 1, wherein the concave portion includes an annular groove and a flat surface formed in a partial region of the groove bottom surface of the annular groove.   The hydrodynamic bearing device according to claim 1, wherein the concave portion includes an annular groove and a flat surface formed in a partial region of the outer peripheral surface of the shaft portion connected to the annular groove.   2. The hydrodynamic bearing device according to claim 1, wherein the resin is a resin composition based on polyphenylene sulfide or a liquid crystal polymer.   A motor comprising the hydrodynamic bearing device according to claim 1, a stator coil, and a rotor magnet.

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