JP2008185140A - Dynamic pressure bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dynamic pressure bearing device which excels in workability and has a housing or a hub forming high-precision thrust dynamic pressure grooves. <P>SOLUTION: In the dynamic pressure bearing device, the periphery of a housing 71 is comprised of a dynamic pressure generation member 712 and a peripheral body 711 which are separately formed, and the two parts can be formed from different materials by different processing methods. Since the peripheral body does not face the thrust bearing clearance and is not required to have a superior wear resistance property, the moldability of the peripheral body 711 can be improved by forming it with soft metal forging. Moreover, the dynamic pressure generation member 712 can be formed in a simple shape and can be machined comparatively easily even with a hard metal, and the wear resistance property can be improved without causing cost increases or machining time lengthening. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device that rotatably supports a shaft member by a hydrodynamic action of 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, Suitable for small motors such as spindle motors for magneto-optical disk drive devices such as MOs, polygon scanner motors for laser beam printers (LBP), color wheel motors for projectors, or fan motors used for cooling electrical equipment Can be used.

  In Patent Document 1, a housing having a cylindrical side portion, a bearing sleeve fixed to the inner periphery of the housing, a shaft member rotatably inserted into the inner periphery of the bearing sleeve, and a flange shape on the shaft member are disclosed. The hydrodynamic bearing device includes a hub provided with a rotor magnet and having a thrust bearing gap formed between the end surface of the housing side and the end surface of the hub. In this dynamic pressure bearing device, the housing is formed by forging a metal material, and a thrust dynamic pressure groove is formed on the end surface of the side portion of the housing by molding.

JP 2006-207787 A

  When the housing is formed by forging as described above, a relatively soft material such as brass may be used in order to improve workability. When the housing is formed of a soft metal in this way, the wear resistance is inferior, so the portion of the housing that faces the thrust bearing gap is worn by sliding against the end face of the opposite hub, and the thrust bearing function is reduced. As a result, there is a risk of lowering the supporting force in the thrust direction due to this. In particular, when the thrust dynamic pressure generating portion is formed in this portion as described above, the thrust dynamic pressure generating portion is worn out, so that the support force in the thrust direction may be significantly reduced.

  Such inconvenience can be solved by forming the housing by a cutting process capable of processing a hard material with high accuracy. However, for example, the housing of a hydrodynamic bearing device as shown in Patent Document 1 has a complicated shape in which a tapered surface that forms a seal space is formed on the outer peripheral surface. If a housing having such a complicated shape and made of hard metal is formed by cutting, the cost increases and the production efficiency decreases.

  Also, the hub that faces the housing through the thrust bearing gap often has a complicated shape, such as requiring a mounting portion for mounting the rotor magnet. For this reason, when the hub is formed of a metal material, the same problem as described above occurs.

  An object of the present invention is to provide a hydrodynamic bearing device including a metal housing or hub excellent in wear resistance and formability.

  In order to solve the above problems, the present invention generates a hydrodynamic action on a housing having a cylindrical side portion, a thrust bearing gap facing an end surface of the side portion of the housing, and a lubricating film formed in the thrust bearing gap. In the hydrodynamic bearing device provided with the thrust dynamic pressure generating portion to be made, the side portion of the housing includes a dynamic pressure generating member in which the thrust dynamic pressure generating portion is formed, a side body formed by plastic processing of a metal material, It is characterized by comprising.

  As described above, in the dynamic pressure bearing device of the present invention, the dynamic pressure generating member including the thrust dynamic pressure generating portion requiring wear resistance and the other side main body are separately formed, so that It can be formed with different materials and processing methods. According to this, since the side part body does not face the thrust bearing gap and wear resistance is not so much required, the formability is improved by forming the side part body by plastic processing (for example, forging or pressing) of soft metal. be able to.

  Thus, if the part which has the complicated shape of a housing side part is formed in the side part main body with high moldability, a dynamic pressure generating member can be made into a simple shape. As a result, even if the dynamic pressure generating member is made of a hard metal, it can be cut relatively easily, so that it is possible to improve wear resistance without incurring an increase in cost and an increase in manufacturing time. In addition, by simplifying the shape of the dynamic pressure generating member, the support structure when molding the thrust dynamic pressure generating part is simplified and it becomes easier to pressurize, so the thrust dynamic pressure generating part can be accurately formed. Can do.

  In addition, dynamic pressure action is generated in the shaft member, the hub provided in a flange shape on the shaft member, to which the rotor magnet is attached, the thrust bearing gap facing the end surface of the hub, and the lubricating film formed in the thrust bearing gap Also in the hydrodynamic bearing device provided with the thrust dynamic pressure generating portion to be made, the hub is composed of a dynamic pressure generating member obtained by molding the thrust dynamic pressure generating portion and a hub body formed by plastic processing of a metal material. Thus, the same effect as described above can be obtained.

  As described above, according to the present invention, it is possible to obtain a hydrodynamic bearing device including a housing or a hub that is excellent in workability and in which thrust dynamic pressure grooves are formed with high accuracy.

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

  FIG. 1 conceptually shows a configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device 1 according to a first embodiment of the present invention. 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 hub 3 provided in the fluid dynamic bearing device 1. The 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 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 hub 3 provided on the shaft member 2, a bearing sleeve 8 with the shaft member 2 inserted on the inner periphery, and a cup that holds the bearing sleeve 8 on the inner periphery. Shaped 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.

  As will be described in detail later, in this hydrodynamic bearing device 1, a radial bearing portion that supports the shaft member 2 and the hub 3 in the radial direction between the outer peripheral surface 2 a of the shaft member 2 and the inner peripheral surface 8 a of the bearing sleeve 8. R1 and R2 are formed. A thrust bearing portion T that supports the shaft member 2 and the hub 3 in the thrust direction is formed between the lower end surface 3a1 of the base portion 3a of the 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 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, press-fitting (hereinafter referred to as press-fitting adhesion) with an adhesive interposed therebetween. The hub 3 includes a base portion 3a having a substantially disc shape, a peripheral wall portion 3b extending axially downward from an 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 disk mounting surface 3d. And. 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 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 angle with respect to the axial direction is set smaller than the tapered surface 71a2 of the opposing housing 7. Thus, a tapered seal space S is formed between the inner peripheral surface 9a of the retaining member 9 and a tapered surface 71a2 of the housing 7 to be described later, 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 includes a side portion 71 formed in a cylindrical shape and a bottom portion 72 that closes one end opening of the side portion 71. The housing side portion 71 includes a substantially cylindrical side body 711 and a dynamic pressure generating member 712 fixed to the upper end surface 711d of the side body 711. In this embodiment, the side body 711 and the bottom 72 are integrally formed. However, after these are formed separately, they may be fixed by any means such as adhesion, welding, or welding.

  The side body 711 is formed by plastic processing of a relatively soft metal material, and is formed by, for example, brass forging. A tapered surface 711 b that gradually increases in diameter upward is provided at the upper part of the outer peripheral surface of the side body 711, and a cylindrical surface 711 c is provided at the lower part of the outer peripheral surface of the side body 711. The taper surface 711b 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 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 711c is fixed to the inner peripheral surface of the bracket 6 by adhesion or the like. In addition, the processing method of the side part main body 711 is not restricted to a forging process, For example, it can also form by press work.

  The dynamic pressure generating member 712 is formed in an annular shape having a rectangular cross section by cutting a relatively hard metal material such as stainless steel. The dynamic pressure generating member 712 is fixed to the upper end surface 711d of the side body 711 by means such as adhesion, welding, or pressure welding. As shown in FIG. 4, dynamic pressure grooves 712a1 arranged in a spiral shape are formed on the upper end surface 712a of the dynamic pressure generating member 712 as a thrust dynamic pressure generating portion. The dynamic pressure groove 712a1 can be formed by molding, for example. The inner peripheral surface 712c of the dynamic pressure generating member 712 has the same diameter as the inner peripheral surface 711a of the side body 711, and the inner peripheral surface 71a of the cylindrical side housing 71 is formed by these inner peripheral surfaces 712c and 711a. Form. The dynamic pressure generating member 712 protrudes to the outer diameter from the outer diameter end of the upper end surface 711d of the side body 711, and the lower end surface 712b of this protruding portion is axially aligned with the upper end surface 9b of the retaining member 9 The shaft member 2 and the hub 3 are prevented from coming off.

  As described above, the housing side portion 71 of the hydrodynamic bearing device 1 according to the present invention is configured by integrating the side body 711 formed by plastic working and the dynamic pressure generating member 712 formed by cutting. Is done. As a result, the side body 711 does not face the thrust bearing gap and wear resistance is not so much required. Therefore, the side body 711 having a complicated shape formed with the tapered surface 711b and the like is formed by plastic processing of soft metal. be able to. Therefore, the formation of the side body 711 is facilitated, and the manufacturing cost can be reduced.

  Further, by forming a part having a complicated shape of the housing side part 71 with the side body 711 having high formability and making it a separate member from the dynamic pressure generating part, the dynamic pressure generating member 712 has a simple shape (for example, a circular shape). Annular). As a result, even if the dynamic pressure generating member 712 is formed of a hard metal having good wear resistance, it can be cut relatively easily, so that the thrust bearing gap is not increased without incurring an increase in cost and an increase in manufacturing time. The wear resistance of the facing upper end surface 712a, particularly the dynamic pressure groove 712a1, can be improved. In addition, since the dynamic pressure generating member 712 has a simple shape, the support structure when the dynamic pressure groove 712a1 is molded is simplified and can be easily pressurized. It can be formed well.

  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 71a 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, other porous materials, or the like in addition to the sintered metal.

  On the inner peripheral surface 8a of the bearing sleeve 8, as shown in FIG. 3, dynamic pressure grooves 8a1 and 8a2 arranged in a herringbone shape are formed as radial dynamic pressure generating portions in two regions separated in the axial direction. Is done. 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. These axial grooves and radial grooves may be formed on the inner peripheral surface 71 a and the inner bottom surface 72 a 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 within a range in which the volume change due to temperature change or pressure change within the expected use range of the lubricating oil filled in the bearing can be absorbed, the oil level is always in the seal space S. Retained.

  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, thereby causing the shaft member 2 and the hub 3 to move. Radial bearing portions R1 and R2 that are rotatably supported in the radial direction are formed. At the same time, the dynamic pressure groove 712a1 formed on the upper end surface 712a of the dynamic pressure generating member 712 generates a dynamic pressure action on the lubricating oil in the thrust bearing gap, thereby rotating the shaft member 2 and the hub 3 in the thrust direction. A thrust bearing portion T that is freely supported 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 axial clearance between the upper end surface 8b and the lower end surface 3a1 of the base 3a of the hub 3, the pressure balance in the internal space can be maintained appropriately. 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 of the first radial bearing portion R1 flows downward, and the radial bearing gap of the second radial bearing portion → the radial groove 8c1 → the axial groove 8d1 → It flows through the path of the axial gap between the bearing sleeve 8 and the hub 3 and 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. The relationship between the axial dimensions can be reversed (X1 <X2) as long as no negative pressure is generated. Further, when it is not necessary 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.

  The present invention is not limited to the above embodiment. Hereinafter, other embodiments of the present invention will be described. 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.

  FIG. 5 shows a hydrodynamic bearing device 21 according to a second embodiment of the present invention. In this dynamic pressure bearing device 21, the hub 3 is composed of a hub body 31 and a dynamic pressure generating member 32. The dynamic pressure generating member 32 is formed in an annular shape by cutting of stainless steel or the like, and the lower end surface thereof forms a lower end surface 3a1 of the base portion 3a of the hub 3, and a thrust dynamic pressure generating portion is formed on the lower end surface. It is formed. This thrust dynamic pressure generating portion forming region is opposed to the upper end surface 71b of the side portion 71 of the housing 7 formed in a smooth surface via a thrust bearing gap of the first thrust bearing portion T1. The hub body 31 is formed by, for example, brass forging, and a dynamic pressure generating member 32 is fixed to a predetermined position of the hub body 31 by an appropriate means such as adhesion, welding, or pressure welding. The housing 7 includes a substantially cylindrical side portion 71 that is open at both ends in the axial direction, and a bottom member 72 that closes one end opening portion of the side portion 71. The tapered surface 71c and the cylindrical surface 71d of the housing side portion 71 in the dynamic pressure bearing device 21 of the present embodiment are respectively the tapered surface 71a2 and the cylindrical surface 71a3 of the housing side portion 71 in the dynamic pressure bearing device 1 of the above embodiment. Correspond.

  Further, in the dynamic pressure bearing device 21, the disc-shaped flange portion 10 is fixed to the lower end of the shaft member 2. The upper end surface 10a of the flange portion 10 faces the lower end surface 8c of the bearing sleeve 8 via a thrust bearing gap of the second thrust bearing portion T2. When the shaft member 2 and the hub 3 rotate, a dynamic pressure action is generated in the lubricating film in the thrust bearing gaps of the first and second thrust bearing portions T1 and T2, and the shaft member 2 and the hub 3 are rotatably supported in a non-contact manner. Is done. As described above, the thrust bearing portions T1 and T2 are formed at two locations separated in the axial direction, so that the bearing rigidity, particularly the moment rigidity is enhanced. In this embodiment, the seal space S is formed between the tapered surface 71 c of the housing side portion 71 and the cylindrical inner peripheral surface 3 b 2 of the peripheral wall portion 3 b of the hub 3.

  The shape or the like of the dynamic pressure generating member is not limited to the above embodiment, and can be changed as appropriate. For example, the dynamic pressure generating member 712 in the housing side portion 71 of the dynamic pressure bearing device 1 shown in FIG. Alternatively, the dynamic pressure generating member 32 provided on the hub 3 of the dynamic pressure bearing device 1 shown in FIG. 5 may be thickened so that the upper end surface of the dynamic pressure generating member 32 is exposed to the upper end surface of the hub 3.

  Further, 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, but this is not restrictive. 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 herringbone-shaped dynamic pressure groove, a step bearing, or a wave bearing (a step bearing having a wave shape) may be formed.

  Further, in the above embodiment, the radial bearing portions R1 and R2 are provided separately in the axial direction. However, the present invention is not limited thereto, and for example, they may be continuously formed in the axial direction. Alternatively, only one of the radial bearing portions R1 and R2 may be provided.

  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

  In the above embodiment, a disk is placed on the hub 3 and the hydrodynamic bearing devices 1 and 21 are used for a spindle motor used in a disk drive device such as an HDD. However, the present invention is not limited to this. For example, a polygon mirror may be attached to or integrated with the hub 3, and the dynamic pressure bearing devices 1 and 21 may be used for supporting the rotating shaft of a polygon scanner motor of a laser beam printer. Alternatively, a color wheel can be mounted on the hub 3 and the dynamic pressure bearing devices 1 and 21 can be used for supporting the rotating shaft of the color wheel motor of the projector. Alternatively, a fan may be installed (integrated) in the hub 3 and the dynamic pressure bearing devices 1 and 21 may be used for the fan motor.

It is sectional drawing which shows the spindle motor incorporating the dynamic pressure bearing apparatus. It is sectional drawing which shows the hydrodynamic bearing apparatus 1 which concerns on this invention. 3 is an axial sectional view of a bearing sleeve 8. FIG. 6 is a top view of a dynamic pressure generating member 712. FIG. It is sectional drawing of the hydrodynamic bearing apparatus 21 which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Shaft member 3 Hub 4 Stator coil 5 Rotor magnet 6 Bracket 7 Housing 71 Side part 72 Bottom part 711 Side part main body 712 Dynamic pressure generating member 712a1 Dynamic pressure groove (thrust dynamic pressure generating part)
8 Bearing sleeve 9 Retaining member 31 Hub body 32 Dynamic pressure generating member R1, R2 Radial bearing portion T Thrust bearing portion S Seal space

Claims (4)

A dynamic motor comprising a housing having a cylindrical side part, a thrust bearing gap facing an end surface of the side part of the housing, and a thrust dynamic pressure generating part for generating a dynamic pressure action on a lubricating film formed in the thrust bearing gap. In the pressure bearing device,
A hydrodynamic bearing device, characterized in that a side portion of the housing is composed of a dynamic pressure generating member forming the thrust dynamic pressure generating portion and a side main body formed by plastic processing of a metal material. A shaft member, a hub provided in a flange shape on the shaft member, to which a rotor magnet is attached, a thrust bearing gap facing the end surface of the hub, and a thrust that generates a dynamic pressure action on a lubricating film formed in the thrust bearing gap In the hydrodynamic bearing device provided with the hydrodynamic pressure generating part,
A hydrodynamic bearing device, characterized in that a hub includes a dynamic pressure generating member that forms the thrust dynamic pressure generating portion and a hub body that is formed by plastic processing of a metal material.   The dynamic pressure bearing device according to claim 1, wherein the dynamic pressure generating member is formed by cutting a metal material.   The hydrodynamic bearing device according to claim 1, wherein the thrust dynamic pressure generating portion is formed by molding.

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