JP5064083B2 - Method for manufacturing hydrodynamic bearing device - Google Patents

Description

  The present invention relates to a method for manufacturing a hydrodynamic bearing device in which a shaft member is rotatably supported by a lubricating film formed in a bearing gap.

  Due to its high rotational accuracy and quietness, the hydrodynamic bearing device is an information device, for example, a magnetic disk drive device such as HDD, an optical disk drive device such as CD-ROM, CD-R / RW, DVD-ROM / RAM, MD, MO, etc. Suitable for small motors such as fan motors used for spindle motors such as magneto-optical disk drive devices, etc., polygon scanner motors for laser beam printers (LBP), color wheels for projectors, cooling fans for electrical equipment, etc. It can be used.

  For example, a hydrodynamic bearing device disclosed in Patent Document 1 includes a bottomed cylindrical housing, a bearing sleeve fixed to the inner periphery of the housing, a shaft member inserted into the inner periphery of the bearing sleeve, and a shaft member. A fixed disk hub. A radial bearing gap is formed between the inner peripheral surface of the bearing sleeve and the outer peripheral surface of the shaft member, and a thrust bearing gap is formed between the upper end surface of the housing and the disk hub.

JP 2006-207787 A

  In such a hydrodynamic bearing device, the dimensional accuracy such as the squareness between the radial bearing surface formed on the inner peripheral surface of the bearing sleeve and the thrust bearing surface formed on the upper end surface of the housing is important. If this dimensional accuracy is not sufficient, the width accuracy of the radial bearing gap and the thrust bearing gap is lowered, which may adversely affect the rotation accuracy, bearing rigidity, and the like. In order to increase the dimensional accuracy, it is necessary to process the housing and the bearing sleeve with high accuracy, improve the accuracy of the jig used to assemble both members, and improve the assembly accuracy. However, such highly accurate processing and assembly leads to a rise in manufacturing cost and a decrease in production efficiency.

  The subject of this invention is providing the manufacturing method of the hydrodynamic bearing apparatus which can raise dimensional accuracy, such as a squareness of a radial bearing surface and a thrust bearing surface, simply and at low cost.

In order to solve the above problems, the present invention is formed on a housing having a cylindrical side portion, a bearing sleeve fixed to the inner periphery of the housing, and an end surface on one axial side of the side portion of the housing. A thrust bearing gap that faces the thrust bearing surface, a radial bearing gap that faces a radial bearing surface that is formed on the inner peripheral surface of the bearing sleeve, and an end portion on one axial side of the outer peripheral surface of the side portion of the housing A hydrodynamic bearing device provided with a tapered surface provided in the vicinity and gradually reduced in diameter toward the other in the axial direction, and a seal space that faces the tapered surface and prevents leakage of lubricant inside the bearing to the outside. a method for manufacturing, the bearing sleeve is arranged on the inner periphery of the housing, inserting the male into the inner periphery of the bearing sleeve, with no supporting said housing from the other axial side Push the end surface of one axial side of the housing on the other side in the axial direction in the male, the housing, setting the bearing sleeve, and the male, the small-diameter by the amount of press-fitting margin of the outer circumferential surface of the housing the Rukoto reduced in diameter to the housing by press-fitting to the inner periphery of the female mold which is, as well as molding the radial bearing surface against the inner circumferential surface of the bearing sleeve on the outer peripheral surface of the male, the housing the inner peripheral surface and a step of crimping and fixing the outer peripheral surface of the bearing sleeve, in a state in which the tapered surface of the housing in the female support from the other axial side, one axial side of the housing in the male by pressing the end face of the axial direction, in which a step of molding the thrust bearing surface to the end surface of one axial side of the housing. Incidentally, the bearing surface here means a portion facing the bearing gap, and it does not matter whether a dynamic pressure generating portion is formed on this surface (the same applies to the following description).

  Thus, according to the manufacturing method of the present invention, the radial bearing surface formed on the bearing sleeve and the thrust bearing surface formed on the side of the housing can be molded with the same mold. By accurately machining the dimensional accuracy, the dimensional accuracy such as the squareness and the deflection accuracy can be increased. In addition, by pressing and fixing the inner peripheral surface of the housing side and the outer peripheral surface of the bearing sleeve with this molding pressure, the dimension between the radial bearing surface and the thrust bearing surface when the housing and the bearing sleeve are assembled. A situation in which the accuracy deteriorates can be avoided. Further, according to this manufacturing method, since the housing and the bearing sleeve can be fixed in the mold for molding the radial bearing surface and the thrust bearing surface, the radial bearing surface and the thrust bearing in the sub-assemblies of the housing and the bearing sleeve are provided. Dimensional accuracy such as surface accuracy and perpendicularity of the surface can be increased. Therefore, the dimensional accuracy required for the housing and the bearing sleeve before assembly is relaxed, and the processing cost of these members can be reduced.

  When the thrust dynamic pressure generating part that generates dynamic pressure action on the lubricating film in the thrust bearing gap is molded by the compression force at the time of molding the thrust bearing surface, the processing man-hours are reduced, the manufacturing cost is reduced, and the production efficiency is reduced. Improvement is achieved. Further, the same effect as described above can be obtained even if a radial dynamic pressure generating portion that generates a dynamic pressure action on the lubricating film in the radial bearing gap is molded by the pressing force at the time of molding the radial bearing surface.

  Further, when the housing of the hydrodynamic bearing device has a seal surface facing a seal space that prevents the lubricant inside the bearing from leaking to the outside, the seal surface is formed by the type of the radial bearing surface and the thrust bearing surface. If the molding is performed with the pressing force at the time of molding, the number of processing steps is reduced, and the manufacturing cost is reduced and the production efficiency is improved. Further, according to this manufacturing method, the molding of each bearing surface and the molding of the seal surface can be performed with the same mold, so that the dimensional accuracy of the seal surface with respect to each bearing surface can be increased. Thereby, the precision of the seal space formed at the time of rotation of a shaft member is raised, and the improvement of a sealing performance is achieved.

  As described above, according to the method for manufacturing a fluid dynamic bearing device of the present invention, the dimensional accuracy such as the perpendicularity between the radial bearing surface and the thrust bearing surface can be set with high accuracy easily and at low cost.

  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 (dynamic pressure bearing device 1) to which the manufacturing method of the present invention is applied. This spindle motor for information equipment is used in a disk drive device such as an HDD, and includes a hydrodynamic bearing device 1 and, for example, a stator coil 4 and a rotor magnet 5 that are opposed to each other with a gap in the radial direction. Yes. The stator coil 4 is attached to the outer peripheral side inner peripheral surface 6 a of the bracket 6, and the rotor magnet 5 is attached to the outer periphery of the disk hub 3 provided in the hydrodynamic bearing device 1. The disk hub 3 holds one or more disk-shaped information recording media (not shown) such as magnetic disks. A housing 7 of the hydrodynamic bearing device 1 is mounted on the inner periphery of the bracket 6. When the stator coil 4 is energized, the rotor magnet 5 is rotated by an exciting force generated between the stator coil 4 and the rotor magnet 5, and accordingly, the disk hub 3 and the disk are rotated.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a shaft member 2, a flange-shaped disk hub 3 provided on the shaft member 2, a bearing sleeve 8 with the shaft member 2 inserted on the inner periphery, and a bearing sleeve 8 held on the inner periphery. And a bottomed cylindrical housing 7. For convenience of explanation, the following description will be given with the opening side of the housing 7 as the upper side and the closing side as the lower side.

  In the hydrodynamic bearing device 1, radial bearing portions R 1 and R 2 that support the shaft member 2 and the disk hub 3 in the radial direction are formed between the outer peripheral surface 2 a of the shaft member 2 and the inner peripheral surface 8 a of the bearing sleeve 8. Is done. A thrust bearing portion T that supports the shaft member 2 and the disc hub 3 in the thrust direction is formed between the lower end surface 3a1 of the base portion 3a of the disc hub 3 and the upper end surface 8b of the bearing sleeve 8.

  The shaft member 2 is formed by cutting or forging a metal material such as stainless steel. The outer peripheral surface 2a of the shaft member 2 is formed in a smooth cylindrical surface having no dynamic pressure generating portion, and is opposed to the inner peripheral surface 8a of the bearing sleeve 8 via a radial bearing gap.

  The disk hub 3 is formed of, for example, a metal material, and is fixed to the upper end of the shaft member 2 by means such as adhesion, press-fitting, or press-fitting with an adhesive (hereinafter referred to as press-fitting adhesion). The disc hub 3 includes a base portion 3a having a substantially disc shape, a peripheral wall portion 3b extending axially downward from the outer peripheral portion of the base portion 3a, a flange portion 3c provided on the outer periphery of the peripheral wall portion 3b, and a disc mounting surface. 3d. A magnetic disk or the like (not shown) is placed on the disk mounting surface 3d. A rotor magnet 5 is attached to the outer peripheral surface 3b1 of the peripheral wall 3b.

  A retaining member 9 is provided on the inner periphery of the peripheral wall 3 b of the disk hub 3. The retaining member 9 is formed in a ring shape having a substantially L-shaped cross section by press molding of a metal material, for example, a soft metal such as brass, and is provided on a step portion 3e provided at the upper end portion of the inner peripheral surface of the peripheral wall portion 3b. It is fixed by appropriate means such as adhesion and welding. The inner peripheral surface 9a of the retaining member 9 is formed in a tapered surface shape whose diameter is gradually increased upward, and the inclination angle of this surface with respect to the axial direction is set smaller than the tapered surface 7a4 of the opposing housing 7. . As a result, a tapered seal space S is formed between the inner peripheral surface 9a of the retaining member 9 and the tapered surface 7a4 of the housing 7, with the radial width gradually reduced upward. In addition to the pull-in action by the capillary force of the seal space S, the lubricating fluid in the seal space S that has flowed in the outer diameter direction due to the centrifugal force is moved upward by the inner peripheral surface 9a of the tapered retaining member 9, that is, inside the bearing. By being pushed to the side, leakage of the lubricating fluid to the outside is surely prevented.

  The housing 7 is formed by forging a metal material such as brass, for example, and integrally includes a side portion 7a formed in a cylindrical shape and a bottom portion 7b that closes one end opening of the side portion 7a. In the present embodiment, the side portion 7a and the bottom portion 7b are integrally formed. However, after these are formed separately, they may be fixed together by means such as adhesion, welding, or welding. Further, the method of forming the housing 7 is not limited to forging, and can be formed by, for example, pressing or machining.

  The upper end surface 7a1 of the side portion 7a functions as a thrust bearing surface B facing the thrust bearing gap, and a dynamic pressure groove 7a10 arranged in a spiral shape as a thrust dynamic pressure generating portion is formed on this surface (see FIG. 4). ). A radial shoulder surface 7a3 and a tapered surface 7a4 that is gradually reduced in diameter downward from the inner diameter end of the shoulder surface 7a3 are provided in the upper portion of the outer peripheral surface of the side portion 7a. A cylindrical surface 7a5 is provided. The shoulder surface 7a3 engages with the upper end surface 9b of the retaining member 9 and restricts the shaft member 2 and the disc hub 3 from coming off. The taper surface 7a4 forms an annular seal space S whose radial dimension is gradually reduced upward with the inner peripheral surface 9a of the retaining member 9 fixed to the disk hub 3. The seal space S communicates with an outer diameter side of a thrust bearing gap of a thrust bearing portion T described later. The cylindrical surface 7a5 is fixed to the inner peripheral surface of the bracket 6 by adhesion or the like.

  The bearing sleeve 8 is formed in a cylindrical shape with a porous body made of sintered metal, in particular, a sintered metal porous body mainly composed of copper, and is press-fitted into a predetermined position on the inner peripheral surface 7a2 of the housing 7, It is fixed by means such as adhesion or press-fit adhesion. The bearing sleeve 8 can be formed of a metal material such as a copper alloy in addition to the sintered metal.

  The inner peripheral surface 8a of the bearing sleeve 8 functions as a radial bearing surface A facing the radial bearing gap, and is arranged in a herringbone shape as a radial dynamic pressure generating portion in two regions separated in the axial direction of this surface. Dynamic pressure grooves 8a1 and 8a2 are formed (see FIG. 3). Further, one or a plurality of axial grooves 8d1 are formed on the outer peripheral surface 8d of the bearing sleeve 8, and a radial groove 8c1 communicating with the axial groove 8d1 is formed on the lower end surface 8c. The axial grooves and the radial grooves may be formed on the inner peripheral surface 7a2 and the inner bottom surface 7b1 of the housing 7. Alternatively, an axial groove and a radial groove may be formed on both the bearing sleeve 8 side and the housing 7 side.

  The fluid dynamic bearing device 1 is completed by filling the internal space of the fluid dynamic bearing device 1 configured as described above with, for example, lubricating oil as a lubricating fluid. Since the volume of the seal space S is set in a range that can absorb the volume change due to the temperature change within the expected use range of the lubricating oil filled in the bearing, the oil level is always held in the seal space S. The

  When the shaft member 2 rotates, the dynamic pressure grooves 8a1 and 8a2 formed on the inner peripheral surface 8a of the bearing sleeve 8 generate a dynamic pressure action on the lubricating oil in the radial bearing gap, so that the shaft member 2 and the disc hub 3 Are formed in the radial bearing portions R1 and R2. At the same time, the dynamic pressure groove 7a10 formed in the upper end surface 7a1 of the housing 7 generates a dynamic pressure action on the lubricating oil in the thrust bearing gap so that the shaft member 2 and the disk hub 3 can rotate in the thrust direction. A supporting thrust bearing portion T is formed.

  Further, as shown in FIG. 2, the axial groove 8d1 formed on the outer peripheral surface 8d of the bearing sleeve 8 and the radial groove 8c1 formed on the lower end surface 8c allow the lower end of the radial bearing gap and the bearing sleeve 8 to By communicating the gap between the upper end surface 8b and the lower end surface 3a1 of the base portion 3a of the disk hub 3, the pressure balance in the internal space can be properly maintained. Furthermore, in this embodiment, as shown in FIG. 3, the dynamic pressure groove 8a1 of the inner peripheral surface 8a of the bearing sleeve 8 is axially asymmetric with respect to the annular smooth portion formed in the axially intermediate portion, specifically The axial dimension X1 of the upper region from the annular smooth portion is larger than the axial dimension X2 of the lower region (X1> X2). For this reason, when the shaft member 2 rotates, the pulling force (pumping force) of the lubricating oil by the dynamic pressure groove 8a1 is relatively larger in the upper region than in the lower region. Due to the differential pressure of the pulling force, the lubricating oil filled in the radial bearing gap flows downward, and flows in the gap between the radial groove 8c1 → the axial groove 8d1 → the bearing sleeve 8 and the base 3a of the disk hub 3. Then, it returns to the radial bearing gap again. Thus, by forcibly circulating the lubricating oil in the radial bearing gap, it is possible to more effectively prevent the generation of a local negative pressure in the internal space of the bearing device. When there is no need to force the lubricating oil to flow through the radial bearing gap as described above, the shape of the dynamic pressure groove 8a1 may be formed symmetrically with respect to the annular smooth portion.

  Hereinafter, a method for assembling the housing 7 and the bearing sleeve 8, a radial bearing surface A, a thrust bearing surface B, a radial dynamic pressure generating portion (dynamic pressure grooves 8a1, 8a2), and a thrust dynamic pressure generating portion ( A method of forming the dynamic pressure groove 7a10) will be described with reference to FIG.

  The mold used in this process is composed of a male mold 10 and a female mold 20. The male mold 10 includes a large diameter part 11 and a small diameter part 12. Formed on the end surface 11a of the large-diameter portion 11 is a molding portion 11a1 for forming a thrust dynamic pressure generating portion (dynamic pressure groove 7a10). Formed portions 12a1 and 12a2 for forming radial dynamic pressure generating portions (dynamic pressure grooves 8a1 and 8a2) are formed on the outer peripheral surface 12a of the small diameter portion 12.

  The female die 20 has an inner peripheral surface 20 a corresponding to the outer peripheral shape of the housing 7. The inner peripheral surface 20a is formed on a tapered inner peripheral surface 20a1 corresponding to the tapered surface 7a4 on the outer periphery of the housing 7, a cylindrical inner peripheral surface 20a2 corresponding to the cylindrical surface 7a5 on the outer periphery of the housing 7, and a shoulder surface 7a3 on the outer periphery of the housing 7. And a corresponding receiving surface 20a3. The tapered inner peripheral surface 20a1 and the cylindrical inner peripheral surface 20a2 are set to have a smaller diameter than the tapered surface 7a4 and the cylindrical surface 7a5 by a press-fit allowance described later.

  First, as shown in FIG. 5A, the bearing sleeve 8 is inserted into the inner periphery of the housing 7, and the lower end surface 8 c of the bearing sleeve 8 is brought into contact with the inner bottom surface 7 b 1 of the housing 7 for positioning. At this time, the inner peripheral surface 7a2 of the housing 7 and the outer peripheral surface 8d of the bearing sleeve 8 are in a light press-fitted state in which they are fitted through a minute gap or slightly fitted through a press-fitting allowance. In order to improve the fixing force between the housing 7 and the bearing sleeve 8, an adhesive may be interposed in advance on these fixing surfaces.

  Next, as shown in FIG. 5B, the small diameter portion 12 of the male mold 10 is inserted into the inner periphery of the bearing sleeve 8, and the end surface 11 a of the large diameter portion 11 is brought into contact with the upper end surface 7 a 1 of the housing 7. At this time, the outer peripheral surface 12a of the small-diameter portion 12 and the inner peripheral surface 8a of the bearing sleeve 8 are a gap fit that is fitted through a minute gap.

  Next, as shown in FIG. 5C, the housing 7, the bearing sleeve 8, and the male mold 10 are press-fitted into the inner periphery of the female mold 20. Thereby, the outer peripheral surface of the housing 7 receives a pressing force in the inner diameter direction (indicated by a horizontal arrow in FIG. 5C). This compression force is transmitted to the bearing sleeve 8 through the housing 7, and the inner peripheral surface 8 a of the bearing sleeve 8 is pressed against the outer peripheral surface 12 a of the small-diameter portion 12 of the male mold 10, whereby the bearing sleeve 8 that becomes the radial bearing surface A is obtained. The inner peripheral surface 8a is molded. At the same time, the inner peripheral surface 8a of the bearing sleeve 8 is pressed against the molding portions 12a1 and 12a2 provided on the outer peripheral surface 12a of the small-diameter portion 12, thereby causing a radial dynamic pressure generating portion (dynamic pressure groove) on the inner peripheral surface 8a. 8a1, 8a2) are molded (indicated by vertical dotted lines in FIG. 5C). Moreover, the housing 7 and the bearing sleeve 8 are pressure-bonded and fixed by this compression force. Further, the tapered inner peripheral surface 20a1 of the female die 20 is pressed against the outer periphery of the housing 7 by this compression force, whereby the tapered surface 7a4 of the housing 7 is molded.

  Further, the end surface 11a of the large-diameter portion 11 of the male mold 10 is supported in a state where the tapered inner peripheral surface 20a1 and the receiving surface 20a3 of the female mold 20 support the tapered surface 7a4 and the shoulder surface 7a3 of the outer periphery of the housing 7 in the axial direction. By pressing against the upper end surface 7a1 of the housing 7 (indicated by a vertical arrow in FIG. 5C), the upper end surface 7a1 of the housing 7 serving as the thrust bearing surface B is molded. At the same time, a thrust dynamic pressure generating portion (dynamic pressure groove 7a10) is molded on the upper end surface 7a1 by pressing the molding portion 11a1 provided on the end surface 11a of the large diameter portion 11 against the upper end surface 7a1 of the housing 7. (Indicated by a horizontal dotted line in FIG. 5C).

  5C, the bottom portion 7b of the housing 7 is not supported by the mold. Therefore, when the tapered surface 7a4 and the upper end surface 7a1 of the housing 7 are molded, the deformation (extension) generated in the housing side portion 7a can be absorbed on the bottom side 7b side.

  Thereafter, the discharge is performed from the inner periphery of the female die 20 in a state where the small diameter portion 12 of the male die 10 is inserted into the subassemblies of the housing 7 and the bearing sleeve 8. Thereby, the compression force by the inner peripheral surface 20a of the female die 20 is released, and the radial bearing surface A (the inner peripheral surface 8a of the bearing sleeve 8) pressed against the outer peripheral surface of the small-diameter portion 12 of the male die 10 is expanded. In addition, a minute gap is formed between them. Due to the formation of this minute gap, when the small-diameter portion 12 of the male mold 10 is discharged from the inner periphery of the sub-assembly product, the dynamic pressure grooves 8a1 and 8a2 formed in the radial bearing surface A and the outer peripheral surface 12a of the small-diameter portion 12 are formed. It is possible to prevent the formed portions 12a1 and 12a2 from interfering with each other and avoid damage to the dynamic pressure grooves 8a1 and 8a2.

  As described above, according to the manufacturing method of the present invention, the radial bearing surface A (the inner peripheral surface 8a of the bearing sleeve 8) and the thrust bearing surface B (the upper end surface 7a1 of the housing side portion 7a) are molded with the same mold. Therefore, the dimensional accuracy of each bearing surface can be increased by setting the molding surface of the mold for molding them with high accuracy. Specifically, by increasing the dimensional accuracy such as the perpendicularity and runout accuracy between the end surface 11a of the large-diameter portion 11 of the male mold 10 and the outer peripheral surface 12a of the small-diameter portion 12, the perpendicularity and runout between the bearing surfaces are increased. Accuracy and the like can be increased.

  Further, the inner peripheral surface 7a1 of the housing 7 and the outer peripheral surface 8d of the bearing sleeve 8 are pressure-bonded and fixed by the pressing force at the time of molding of each bearing surface. The situation where dimensional accuracy deteriorates can be avoided. In addition, since the molding of the bearing surface and the fixing of the housing 7 and the bearing sleeve 8 are performed with the same mold, the dimensional accuracy of each bearing surface in the sub-assemblies can be increased. The dimensional accuracy required for the sleeve 8 can be relaxed, and the cost can be reduced. Note that the radial bearing surface A, the thrust bearing surface B, and the crimping and fixing of the housing 7 and the bearing sleeve 8 are not necessarily performed at the same time. It is desirable to perform these steps simultaneously.

  In addition, as described above, by molding the thrust dynamic pressure generating portion (dynamic pressure groove 7a10) and radial dynamic pressure generating portions (dynamic pressure grooves 8a1, 8a2) with the pressing force at the time of mold forming, the processing man-hours can be reduced. Therefore, the manufacturing cost can be reduced and the production efficiency can be improved. Further, by molding the taper surface 7a4 that becomes the seal surface of the housing 7 with this compression force, the number of processing steps can be further reduced. Further, since the molding of each bearing surface and the molding of the seal surface are performed with the same mold, the dimensional accuracy of the seal surface with respect to each bearing surface can be increased, so that the formation accuracy of the seal space S is increased, and the seal The performance is improved.

  The manufacturing method of the present invention is not limited to the above. For example, in the above, the small diameter portion 12 of the male mold 10 is inserted into the inner periphery of the housing 7 and the bearing sleeve 8, and these are press-fitted into the inner periphery of the female mold 20. Is inserted into the inner periphery of the female mold 20, the small diameter portion 12 of the male mold 10 is inserted into the inner periphery of the bearing sleeve 8, and the bearing sleeve 8 and the male mold 10 are press-fitted into the inner periphery of the housing 7. The compression force as described above can also be obtained.

  The hydrodynamic bearing device to which the manufacturing method of the present invention is applied is not limited to the above. FIG. 6 shows another example of a hydrodynamic bearing device (dynamic pressure bearing device 21) to which the manufacturing method of the present invention is applied. In the following description, parts having the same configuration and function as those of the above embodiment are given the same reference numerals, and the description thereof is omitted.

  In this dynamic pressure bearing device 21, a flange portion 2b is provided at the lower end of the shaft member 2, and a first thrust bearing is provided between the upper end surface 7a1 of the housing side portion 7a and the lower end surface 3a1 of the base portion 3a of the disk hub 3. A portion T1 is formed, and a second thrust bearing portion T2 is formed between the lower end surface 8c of the bearing sleeve 8 and the upper end surface 2b1 of the flange portion 2b. Further, a seal space S is formed between the inner peripheral surface 3b2 of the peripheral wall portion 3b of the disk hub 3 and the tapered surface 7a4 on the outer periphery of the housing side portion 7a.

  In the above embodiment, the herringbone-shaped dynamic pressure groove is formed as the radial dynamic pressure generating portion and the spiral-shaped dynamic pressure groove is formed as the thrust dynamic pressure generating portion. However, the present invention is not limited to this. For example, a spiral dynamic pressure groove, a multi-arc bearing, or a step bearing may be formed as the radial dynamic pressure generating portion. Further, as the thrust dynamic pressure generating portion, a herring vane-shaped dynamic pressure groove, a step bearing, or a wave bearing (a step bearing having a wave shape) may be formed.

  Alternatively, the inner peripheral surface 8a of the bearing sleeve 8 is a perfect circular outer peripheral surface not provided with a dynamic pressure groove or a circular arc surface as a dynamic pressure generating portion, and the perfect outer periphery of the shaft member 2 facing the inner peripheral surface 8a. A so-called perfect circle bearing can be constituted by the surface 2a.

  Further, in the above embodiment, the radial bearing portions R1 and R2 are provided separately in the axial direction. Alternatively, only one of the radial bearing portions R1 and R2 may be provided.

  In the above embodiment, the radial dynamic pressure generating part is formed on the bearing sleeve 8 side and the thrust dynamic pressure generating part is formed on the housing 7 side. You may form in the outer peripheral surface 2a of the member 2, and the lower end surface 3a1 of the base 3a of the disc hub 3. FIG.

  In the above, lubricating oil is used as the lubricating fluid, but other fluids that can generate a dynamic pressure action in each bearing gap, for example, gas such as air, magnetic fluid, or lubricating grease are used. You can also

  The method for manufacturing a hydrodynamic bearing device according to the present invention is not limited to a spindle motor used in a disk drive device such as an HDD as described above, but is used under a high-speed rotation, such as a spindle motor for driving a magneto-optical disk of an optical disk. The present invention can also be applied to a hydrodynamic bearing device that is used for a small motor for an information device, a rotating shaft support in a polygon scanner motor of a laser beam printer, or a fan motor for a cooling fan of an electric device.

It is sectional drawing which shows the spindle motor incorporating the dynamic pressure bearing apparatus. 1 is a cross-sectional view showing a fluid dynamic bearing device 1. 3 is an axial sectional view of a bearing sleeve 8. FIG. FIG. 6 is a top view of the housing 7. (A)-(c) is sectional drawing which shows the manufacturing process of the subassembly product of the housing 7 and the bearing sleeve 8. FIG. 3 is a cross-sectional view of the hydrodynamic bearing device 21. FIG.

Explanation of symbols

1 Hydrodynamic bearing device (fluid bearing device)
2 Shaft member 3 Disc hub 4 Stator coil 5 Rotor magnet 6 Bracket 7 Housing 7a Side 7a10 Dynamic pressure groove 8 Bearing sleeve 9 Retaining member 10 Male 11 Large diameter 12 Small diameter 20 Female A Radial bearing surface B Thrust bearing Surface R1, R2 Radial bearing part T Thrust bearing part S Seal space

Claims (3)

A housing having a cylindrical side portion, a bearing sleeve fixed to the inner periphery of the housing, a thrust bearing gap formed on an end surface on one axial side of the side portion of the housing and facing a thrust bearing surface; A radial bearing gap formed on the inner peripheral surface of the bearing sleeve and facing a radial bearing surface and an end portion on one axial side of the outer peripheral surface of the side portion of the housing are provided gradually toward the other axial direction. A method for manufacturing a hydrodynamic bearing device comprising a tapered surface having a reduced diameter and a seal space that faces the tapered surface and prevents leakage of lubricant inside the bearing to the outside ,
Disposing the bearing sleeve on the inner periphery of the housing and inserting a male mold on the inner periphery of the bearing sleeve;
In a state where the housing is not supported from the other side in the axial direction, an end surface on one side in the axial direction of the housing is pushed into the other side in the axial direction with the male mold, and the housing, the bearing sleeve, and the male mold are moved to the housing. the Rukoto min press-fitting margin of the outer circumferential surface only by press-fitting to the inner periphery of the female mold set in a small diameter reduced in diameter to the housing, presses the inner circumferential surface of the bearing sleeve on the outer peripheral surface of the male while molding the radial bearing surface Te, a step of bonding and fixing the outer peripheral surface of the bearing sleeve and the inner peripheral surface of the housing,
While supporting the tapered surface of the housing from the other axial side the female, by pressing the end surface of one axial side of the housing in the axial direction in the male, the one axial side of the housing And a step of molding the thrust bearing surface on the end surface.   2. The method of manufacturing a hydrodynamic bearing device according to claim 1, wherein a thrust dynamic pressure generating portion for generating a dynamic pressure action on a lubricating film in a thrust bearing gap is molded by a pressing force at the time of molding the thrust bearing surface.   The method of manufacturing a hydrodynamic bearing device according to claim 1, wherein a radial dynamic pressure generating portion that generates a dynamic pressure action on a lubricating film in a radial bearing gap is molded by a pressing force at the time of molding the radial bearing surface.

Images