JP2007016850A - Dynamic pressure bearing device and motor provided with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dynamic pressure bearing device and a motor provided with it in which a positioning reference-plane of the bearing device relative to a motor-side member is accurately finished. <P>SOLUTION: In a housing 9, an outside-periphery step 9f is formed between a sealing surface 9d formed at the upper end on the outside-periphery and a cylindrical surface 9e formed at the lower end of the outside periphery, and nearly cylindrical protrusions 10 extending axially downward are formed on the end surface 9f1 of the outside periphery step 9f. Thus, the region for formation of the end surface 9f1 adjacent to the protrusion 10 constitutes a relief. The end surface 10a of the protrusions 10 is opposed and parallel to a first thrust-bearing surface 9a, and is finished by e. g. press working to ensure a parallelism relative to the first thrust-bearing surface 9a of at most 10μm, and a flatness of at most 10μm in the end surface 10a itself. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device that rotatably supports a shaft member in a non-contact manner by a hydrodynamic action of a fluid generated in a bearing gap. This type of bearing device includes information devices such as magnetic disk drive devices such as HDD, optical disk drive devices such as CD-ROM, CD-R / RW, DVD-ROM / RAM, and magneto-optical disk drive devices such as MD and MO. It can be suitably used for a spindle motor such as a laser scanner, a polygon scanner motor of a laser beam printer (LBP), a color wheel of a projector, or an electric device such as a small motor such as an axial fan.

  In addition to high rotational accuracy, the various motors are required to have high speed, low cost, low noise, and the like. One of the components that determine the required performance is a bearing that supports the spindle of the motor. In recent years, the use of a hydrodynamic bearing having characteristics excellent in the required performance has been studied or actually used. Yes.

For example, in a hydrodynamic bearing device incorporated in a spindle motor of a disk drive device such as an HDD, both the radial bearing portion that supports the shaft member in the radial direction and the thrust bearing portion that supports the axial direction are configured by the hydrodynamic bearing. There is. As a thrust bearing portion in this type of dynamic pressure bearing device, for example, a dynamic pressure groove as a dynamic pressure generating portion is formed in an axial end surface of a bearing sleeve or a housing, and these axial end surfaces and a shaft opposed thereto are formed. One that forms a thrust bearing gap between both end surfaces of a flange portion of a member is known (see, for example, Patent Document 1).
JP 2003-239951 A

  This type of bearing device is composed of various parts including a bearing sleeve, a housing, and a shaft member, and each component is required to ensure the high bearing performance required as the performance of information equipment increases. Efforts are being made to improve the processing accuracy and assembly accuracy. On the other hand, with the trend of lowering the price and downsizing of information equipment, there is an increasing demand for cost reduction and downsizing of this type of bearing device.

  When the hydrodynamic bearing device is used by being incorporated in a disk drive device or the like as described above, not only the assembly accuracy between the components of the hydrodynamic bearing device, but also the motor (components) incorporating the same is high. Assembly accuracy is required. In such a case, a reference surface (hereinafter referred to as “reference surface”) for determining the relative position between the components of the fluid dynamic bearing device and the motor side member is referred to as the fluid dynamic bearing device side (for example, A method of assembling the motor-side member and the hydrodynamic bearing device with respect to this surface is effective.

  This type of reference surface is required to have high shape accuracy such as high parallelism to the thrust bearing surface or high flatness of the thrust bearing surface. However, at present, it is difficult to finish such a reference surface with high accuracy.

  An object of the present invention is to finish a positioning reference surface with a motor-side member in this type of hydrodynamic bearing device with high accuracy.

  In order to solve the above-described problems, the present invention includes a shaft member, a thrust bearing portion that applies a floating force in the thrust direction to the shaft member by a dynamic pressure action of a fluid generated in a thrust bearing gap, and a shaft member inserted in the inner periphery. A sleeve portion and a housing portion disposed on the outer diameter side of the sleeve portion, and incorporated in the motor, wherein the housing portion defines a relative axial position between the motor side member; and Provided is a fluid dynamic bearing device including a relief portion adjacent to a reference surface. The member on the motor side is sufficient if it is a component of the motor, and includes, for example, a member for fixing the stator coil of the motor. Moreover, the housing part here is a structural member of a hydrodynamic bearing apparatus, and the shape is not ask | required.

  As described above, the present invention is characterized in that a reference surface that defines an axial relative position with a member on the motor side is provided in the housing portion, and a relief portion is provided adjacent to the reference surface. With this configuration, the area can be reduced compared to the reference surface when no escape portion is provided. Therefore, for example, even when the reference surface is press-finished, it is possible to increase the surface pressure at the time of pressing on the reference surface and easily improve the shape accuracy of the finished surface. Alternatively, when finishing the reference surface by machining, increase the shape accuracy of the finished surface (reference surface) by reducing the processing area to reduce the amount of heat generated during processing (for example, during cutting) or suppressing tool wear. be able to. In any case, by finishing the reference surface with high accuracy, the relative position in the axial direction with respect to the motor-side member of the hydrodynamic bearing device can be accurately defined, and the bearing performance or motor performance is improved. be able to.

  In particular, when the reference surface is formed by plastic processing such as press working or forging, the relief portion adjacent to the reference surface plays a role of escaping plastic deformation of the reference surface. Therefore, it is possible to further improve the shape accuracy of the finished surface serving as the reference surface.

  When providing a thrust bearing surface facing the thrust bearing gap in the housing portion, the parallelism of the reference surface with respect to the thrust bearing surface is 10 μm or less from the viewpoint of ensuring positioning (assembly) accuracy with the motor side member. Is preferably 5 μm or less. Here, the degree of parallelism is the amount of deviation of a planar feature (referred to here as a reference plane) from a geometric plane parallel to a reference plane (referred to here as a thrust bearing surface). The size is determined when the interval between the two parallel planes is minimized when the plane feature (reference plane) is sandwiched between two geometrically correct planes parallel to the reference plane (thrust bearing surface). It is expressed by the interval between two planes.

  Similarly, the flatness of the reference surface is preferably 10 μm or less, more preferably 5 μm or less. Here, the flatness is defined as the distance between the two parallel planes is the minimum when the plane feature (the plane that is the target of the flatness, which here refers to the reference plane) is sandwiched between two parallel geometrically correct planes. In this case, it is expressed by an interval between two planes. The thrust bearing surface mentioned here may be any one that faces the thrust bearing gap that generates the dynamic pressure action, and it does not matter whether there is a dynamic pressure groove for generating the dynamic pressure action.

  As an arrangement mode of the reference surface and the relief portion, for example, a configuration in which the reference surface and the relief portion are arranged in parallel in the circumferential direction can be configured. Alternatively, a configuration in which the reference surface and the relief portion are arranged in parallel in the radial direction can be configured.

  The fluid dynamic bearing device having the above configuration can be suitably provided as a motor including the fluid dynamic bearing device, a stator coil, and a rotor magnet that generates an exciting force between the stator coil. In particular, when used by incorporating in a motor that applies a thrust force in the direction opposite to the thrust force in the thrust direction by the thrust bearing portion to the shaft member, the thrust balance of the shaft member can be maintained with high accuracy. Is preferable.

  As described above, according to the present invention, the positioning reference surface with the motor-side member in this type of hydrodynamic bearing device can be finished with high accuracy.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  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 is used in a disk drive device such as an HDD, and is opposed to a hydrodynamic bearing device 1 that supports a rotating member 3 having a shaft member 2 in a non-contact manner in a rotatable manner, for example, via a radial gap. A stator coil 4, a rotor magnet 5, and a bracket 6 are provided. The stator coil 4 is attached to the coil attachment portion 6 c of the bracket 6, and the rotor magnet 5 is attached to the outer periphery of the rotating member 3. The hydrodynamic bearing device 1 is fixed to the inner periphery of the bracket 6. Although not shown, the rotating member 3 holds one or more disk-shaped information recording media (hereinafter simply referred to as disks) such as magnetic disks. In the spindle motor configured as described above, when the stator coil 4 is energized, the rotor magnet 5 is rotated by the exciting force generated between the stator coil 4 and the rotor magnet 5. The disk held by the member 3 rotates integrally with the shaft member 2.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a sleeve portion 8, a housing portion 9 disposed on the outer diameter side of the sleeve portion 8, a rotating member 3 that rotates relative to the sleeve portion 8 and the housing portion 9, and a housing portion 9. And a lid member 12 for sealing one end in the axial direction. For the sake of convenience of explanation, of the openings of the housing part 9 formed at both ends in the axial direction, the side sealed by the lid member 12 is the lower side, and the side opposite to the sealing side is the upper side.

  The rotating member 3 includes, for example, a hub portion 11 disposed on the opening side of the housing portion 9 and a shaft member 2 inserted into the inner periphery of the sleeve portion 8.

  The hub part 11 is formed of, for example, metal, a disk part 11a that covers the opening side (upper side) of the housing part 9, a cylindrical part 11b that extends axially downward from the outer peripheral part of the disk part 11a, and an outer periphery of the cylindrical part 11b. The disc mounting surface 11c and the flange portion 11d are provided. In this case, when the rotating member 3 is rotated, a finishing process for increasing the perpendicularity of the disk mounting surface 11c with respect to the outer peripheral surface 2a of the shaft member 2 is performed in consideration of the deflection accuracy of the disk placed on the disk mounting surface 11c. It is also possible to apply to the disk mounting surface 11c. Similarly, in order to increase the perpendicularity of the lower end surface 11a1 of the disk portion 11a with respect to the outer peripheral surface 2a of the shaft member 2 from the viewpoint of suppressing variation in the thrust bearing gap of the first thrust bearing portion T1 described later when the rotating member 3 rotates. It is also possible to apply the finishing process to the lower end surface 11a1. A disk (not shown) is fitted on the outer periphery of the disk portion 11a and placed on the disk mounting surface 11c. Then, the disc is held on the hub portion 11 by an appropriate holding means (such as a clamper) not shown. Of course, the hub portion 11 is not limited to metal, and may be formed by, for example, resin injection molding.

  The shaft member 2 is formed integrally with the hub portion 11 in this embodiment, and has a flange portion 2b as a separate member at the lower end thereof. The flange portion 2b is made of metal and is fixed to the shaft portion of the shaft member 2 by means such as screw connection. The shaft member 2 can be formed separately from the hub portion 11, but in that case, for example, the shaft member 2 is made of metal and a hub in consideration of assembly accuracy (perpendicularity etc.) with the hub portion 11. The hub 11 is preferably molded (insert molded) with the portion 11 made of resin and the shaft member 2 as an insert part.

  The sleeve portion 8 can be formed of a metal such as a copper alloy such as brass or an aluminum alloy, or can be formed of a porous body made of a sintered metal. In this embodiment, a sintered metal porous body mainly composed of copper is formed in a cylindrical shape.

  A region where a plurality of dynamic pressure grooves are arranged as a radial dynamic pressure generating portion is formed on the entire inner surface or a partial cylindrical region of the inner peripheral surface 8 a of the sleeve portion 8. In this embodiment, for example, as shown in FIG. 3, two regions where a plurality of dynamic pressure grooves 8a1 and 8a2 are arranged in a herringbone shape are formed apart from each other in the axial direction.

  As the thrust dynamic pressure generating portion, for example, although not shown, a region where a plurality of dynamic pressure grooves are arranged in a spiral shape is formed on the entire lower surface 8c of the sleeve portion 8 or a partial annular region. This dynamic pressure groove forming region is opposed to the upper end surface 2b1 of the flange portion 2b as a second thrust bearing surface, and is rotated between the upper end surface 2b1 and the second thrust bearing portion T2 when the shaft member 2 (rotating member 3) is rotated. (See FIG. 2).

  The housing part 9 is formed in a cylindrical shape with metal or resin. In this embodiment, the housing part 9 has a shape in which both ends in the axial direction are opened, and one end side is sealed with the lid member 12. A first thrust bearing surface 9a is provided on the entire end surface (upper end surface) or a partial annular region on the other end side. In this embodiment, a region in which a plurality of dynamic pressure grooves 9a1 are arranged in a spiral shape is formed on the first thrust bearing surface 9a as a thrust dynamic pressure generating portion, for example, as shown in FIG. This first thrust bearing surface 9a (region where the dynamic pressure groove 9a1 is formed) is opposed to the lower end surface 11a1 of the disk portion 11a of the hub portion 11, and a first to be described later between the lower end surface 11a1 when the rotating member 3 rotates. A thrust bearing gap of the thrust bearing portion T1 is formed (see FIG. 2).

  The lid member 12 that seals the lower end side of the housing portion 9 is formed of metal or resin, and is fixed to an inner peripheral side step portion 9 b provided on the inner periphery of the lower end of the housing portion 9. Here, the fixing means is not particularly limited, and for example, means such as adhesion (including loose adhesion, press-fit adhesion), press-fit, welding (for example, ultrasonic welding), welding (for example, laser welding), combinations of materials and requirements. Can be appropriately selected in accordance with the fixing strength, sealing performance, and the like.

  The outer peripheral surface 8b of the sleeve portion 8 is fixed to the inner peripheral surface 9c of the housing portion 9 by appropriate means such as adhesion (including loose adhesion and press-fit adhesion), press-fitting, and welding.

  On the outer periphery of the housing portion 9, a tapered seal surface 9 d that gradually increases in diameter upward is formed. The tapered sealing surface 9d is an annular shape having a radial dimension gradually reduced from the sealing side (downward) to the opening side (upward) of the housing part 9 between the inner peripheral surface 11b1 of the cylindrical part 11b. A seal space 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 shaft member 2 and the hub portion 11 are rotated.

  A cylindrical surface 9e having a constant diameter is formed at the lower end of the outer periphery of the housing portion 9. In this embodiment, the cylindrical surface 9e serves as an adhesive fixing surface with the inner peripheral surface 6a of the bracket 6. When the bracket 6 described later is attached, the cylindrical surface 9e is adhesively fixed to the inner peripheral surface 6a with an adhesive (see FIG. 2). reference).

  An axially intermediate position on the outer periphery of the housing portion 9, in the illustrated example, an outer peripheral side step portion 9 f is formed between the seal surface 9 d and the cylindrical surface 9 e. For example, as shown in FIG. 5, one or a plurality of convex portions 10 protruding downward in the axial direction from the end surface 9 f 1 of the outer peripheral step 9 f are formed in the outer peripheral step 9 f. In this case, the end surface 9f1 formation region of the outer peripheral side stepped portion 9f excluding the convex portion 10 is a relief portion adjacent to the convex portion 10. In this embodiment, the convex portion 10 has a substantially columnar shape, and is provided at three locations at equal intervals in the circumferential direction on the end surface 9f1 of the outer peripheral side step portion 9f.

  The end surface 10a of the convex portion 10 serves as a positioning reference surface when the bracket 6 described later is attached, and is formed so as to face the first thrust bearing surface 9a and be parallel to the first thrust bearing surface 9a. Specifically, the parallelism of the end surface 10a with respect to the first thrust bearing surface 9a is preferably 10 μm or less, and more preferably 5 μm or less. The flatness of the end face 10a is preferably 10 μm or less, more preferably 5 μm or less.

  The above-described end surface 10a and the convex portion 10 provided with the end surface 10a can be formed simultaneously with the formation of the housing portion 9 by, for example, metal forging. In this case, since only the convex portion 10 provided with the end surface 10a protrudes from the end surface 9f1 of the outer peripheral side step portion 9f, for example, after the forging, the end surface 10a is surface-finished by press working or the like. The molding surface) is only the end surface 10a. Further, the relief portion (end surface 9f1 formation region) adjacent to the convex portion 10 functions as a portion that absorbs (releases) plastic deformation of the convex portion 10 during pressing. For this reason, for example, the press area can be reduced compared to the case where the entire end surface 9f1 of the outer peripheral side stepped portion 9f is used as a reference surface without providing the convex portion 10, thereby increasing the press surface pressure of the end surface 10a. be able to. Therefore, it is possible to form the end surface 10a having high shape accuracy (parallelism, flatness), and to manage the axial interval between the end surface 10a and the first thrust bearing surface 9a with high accuracy. Become.

  The end surface 10a finished with high accuracy as described above functions as an axial positioning reference surface when the bracket 6 which is a member on the motor side is attached. In this embodiment, as shown in FIG. 2, the end surface 6 b of the bracket 6 is brought into contact with the convex end surface 10 a of the housing portion 9, thereby determining the axial position of the housing portion 9 with respect to the bracket 6. In this state, for example, the cylindrical surface 9e of the housing portion 9 is bonded and fixed to the inner peripheral surface 6a of the bracket 6 so that the dynamic pressure bearing device 1 is positioned with respect to the bracket 6 with high accuracy and the dynamic pressure bearing device 1 is used. Is built into the motor side.

  Further, in this embodiment, the positioning of the hydrodynamic bearing device 1 with respect to the bracket 6 enables the axial position of the disk provided on the hub portion 11 (the disk mounting surface 11c thereof) to be set with high accuracy. Thereby, the facing distance between the disk and the disk head can be properly managed, and the reading or writing accuracy of the disk information by the disk head can be improved.

  Further, since the axial positioning of the hydrodynamic bearing device 1 with respect to the bracket 6 is performed with high accuracy, the axial relative position of the rotor magnet 5 with respect to the stator coil 4 fixed to the bracket 6 can be set accurately. Therefore, the axial displacement between the stator coil 4 and the rotor magnet 5 disposed in the radial direction can be minimized, and the axial pulling force due to this displacement is irregularly applied to the rotating member 3. The situation given can be avoided as much as possible. Therefore, it is possible to manage the thrust bearing gap between the first thrust bearing portion T1 and the second thrust bearing portion T2, which will be described later, appropriately and with high accuracy, and to improve the bearing performance.

  The inside of the hydrodynamic bearing device 1 having the above configuration is filled with lubricating oil, and the oil level of the lubricating oil is always maintained in the seal space S. Various types of lubricating oil can be used. In particular, a lubricating oil provided for a fluid dynamic bearing device for a disk drive device such as an HDD is required to have a low evaporation rate and a low viscosity. For example, dioctyl seba Ester lubricants such as Kate (DOS) and Dioctyl Azetate (DOZ) are suitable.

  In the dynamic pressure bearing device 1 having the above-described configuration, when the shaft member 2 (rotating member 3) rotates, a region (a region where the dynamic pressure grooves 8a1 and 8a2 are formed at the upper and lower two locations) that becomes the radial bearing surface of the inner peripheral surface 8a of the sleeve portion 8. ) Is opposed to the outer peripheral surface 2a of the shaft member 2 via a radial bearing gap. As the shaft member 2 rotates, the lubricating oil in the radial bearing gap is pushed toward the axial center of the dynamic pressure grooves 8a1 and 8a2, and the pressure rises. The first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner in the radial direction are configured by the dynamic pressure action of the dynamic pressure grooves 8a1 and 8a2, respectively.

  At the same time, a thrust bearing gap between the first thrust bearing surface 9a (dynamic pressure groove 9a1 formation region) of the housing portion 9 and the lower end surface 11a1 of the hub portion 11 (disk portion 11a) facing the first thrust bearing surface 9a, and the sleeve portion 8 is formed in the thrust bearing gap between the lower end surface 8c (dynamic pressure groove forming region) 8 and the upper end surface 2b1 of the flange portion 2b facing the lower end surface 8c by the dynamic pressure action of the dynamic pressure groove. . The first thrust bearing portion T1 and the second thrust bearing portion T2 that support the rotating member 3 in the thrust direction in a non-contact manner are configured by the pressure of these oil films.

  Although the first embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and other configurations can be adopted. Hereinafter, another configuration example of the hydrodynamic bearing device will be described. Note that, in the drawings shown below, parts and members that have the same configuration and function as those of the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 8 shows a hydrodynamic bearing device 21 according to a second embodiment of the present invention. This dynamic pressure bearing device 21 is also used by being incorporated in a disk driving spindle motor such as an HDD shown in FIG. 1, and constitutes a motor together with, for example, the stator coil 4, the rotor magnet 5, and the bracket 6 shown in FIG. The hydrodynamic bearing device 21 mainly includes a sleeve portion 28, a housing portion 29, and a rotating member 23 that rotates relative to the sleeve portion 28 and the housing portion 29. In this embodiment, the sealing side (bottom 29b side) of the housing part 29 will be described as the lower side, and the side opposite to the sealing side will be described as the upper side.

  The rotating member 23 is mainly composed of the shaft member 22 and the hub portion 11. Among these, the shaft member 22 is formed in a shaft shape having the same diameter with a metal material such as stainless steel.

  The sleeve portion 28 is formed separately from the housing portion 29, for example, in a cylindrical shape made of a sintered metal porous body mainly composed of copper, and includes bonding (including loose bonding and press bonding), press fitting, welding, and the like. The fixing means is fixed at a predetermined position on an inner peripheral surface 29c of the housing portion 29 described later.

  In this embodiment, as described above, a thrust bearing gap is formed only between the first thrust bearing surface 29a of the housing portion 29 and the lower end surface 11a1 of the disk portion 11a facing the first thrust bearing surface 29a. Thus, the thrust bearing gap is not formed. Therefore, the sleeve portion 28 in the second embodiment has a plurality of dynamic pressure grooves as shown in FIG. 3 on its inner peripheral surface 28a, while the upper end surface and the lower end surface are smooth surfaces having no dynamic pressure grooves. Become.

  The housing portion 29 has a bottomed cylindrical shape, and is formed by forging a metal material such as stainless steel. The housing portion 29 has a shape in which the housing portion 9 and the lid member 12 shown in FIG. 2 are integrated, and one end in the axial direction is sealed by a bottom portion 29b.

  A thrust bearing surface 29a is formed on the entire or partial annular region of the opening side end surface (upper end surface) of the housing portion 29. Although not shown as a thrust dynamic pressure generating portion on the thrust bearing surface 29a, for example, A region where dynamic pressure grooves are arranged in the same shape as in FIG. 4 is formed. This thrust bearing surface (dynamic pressure groove forming region) 29a is opposed to the lower end surface 11a1 of the disk portion 11a of the hub portion 11, and between the lower end surface 11a1 when the shaft member 22 (rotating member 23) rotates. A thrust bearing gap of the portion T11 is formed (see FIG. 8).

  On the outer periphery of the upper portion of the housing portion 29, a tapered seal surface 29d that gradually increases in diameter upward is formed. This seal surface 29d and the inner peripheral surface 11b1 of the cylindrical portion 11b provided on the hub portion 11 are formed. Between the two, a tapered seal space S that gradually decreases upward is formed. A cylindrical surface 29e having a constant diameter is formed at the lower end of the outer periphery of the housing portion 29, and is fixedly bonded to the inner peripheral surface 6a via an adhesive when the bracket 6 described later is attached.

  Further, the inner periphery of the lower end of the cylindrical portion 11b of the hub portion 11 is engaged with the housing portion 29 in the axial direction when the shaft member 22 (rotating member 23) is relatively displaced in the axial direction, so that the shaft member 22 is engaged. A locking member 31 for locking is attached.

  An outer peripheral step 29f is formed between the seal surface 29d and the cylindrical surface 29e on the outer periphery of the housing portion 29. For example, as shown in FIG. 8, the outer peripheral step 29f has one or a plurality of convex portions 30 protruding from the end surface 29f1 of the outer peripheral step 29f downward in the axial direction (three in this embodiment). It is formed. In this case, the formation region of the end surface 29 f 1 excluding the convex portion 30 becomes a relief portion adjacent to the convex portion 30.

  The end surface 30a of the convex portion 30 is a reference surface when the bracket 6 to be described later is attached, and is formed so as to face the first thrust bearing surface 29a and be parallel to the first thrust bearing surface 29a. Even in this case, only the convex portion 30 provided with the end surface 30a protrudes from the end surface 29f1 of the outer peripheral side stepped portion 29f, thereby reducing the finishing area (press area) and increasing the press surface pressure. it can. Accordingly, as in the first embodiment, the end surface 30a having high shape accuracy (parallelism and flatness) can be obtained, and the axial interval between the end surface 30a and the first thrust bearing surface 29a can be managed with high accuracy. It becomes possible to do.

  The end surface 30a finished with high accuracy as described above functions as an axial positioning reference surface when the bracket 6 which is a member on the motor side is attached. In this embodiment, unlike the first embodiment, the end surface 6b of the bracket 6 is not brought into direct contact with the end surface 30a of the convex portion 30, but a positioning jig (not shown) is brought into contact. The axial position of the housing part 29 with respect to the bracket 6 is determined. Then, after fixing the annular locking member 31 to the inner periphery of the lower end of the cylindrical portion 11b, the bracket 6 is positioned as shown in FIG. 6, that is, the position where the end surface 6b is separated from the end surface 30a serving as the reference surface by a predetermined distance in the axial direction. Thus, the housing part 29 is fixed to the bracket 6.

  Accordingly, also in this embodiment, the axial positioning of the housing portion 29 with respect to the bracket 6 can be performed with high accuracy, and the same operational effects as in the first embodiment (the thrust bearing gap is properly and accurately managed, the disk head Can improve the reading or writing accuracy of disc information.

  In particular, in this type of hydrodynamic bearing (so-called single thrust type hydrodynamic bearing), the axial position of the stator coil 4 and the axial position of the rotor magnet 5 are shifted so as to press the rotary member 23 downward. A force is applied to maintain a balance with the levitation force by the first thrust bearing portion T11. Therefore, the axial displacement of the dynamic pressure bearing device 21 with respect to the bracket 6 can be performed with high accuracy, whereby the amount of deviation in the axial direction between the stator coil 4 and the rotor magnet 5 can be managed more strictly. The thrust balance of the rotating member 23 can be maintained with high accuracy.

  In the above embodiments (first and second embodiments), the housing portions 9 and 29 and the sleeve portion 8 are formed separately, and the sleeve portions 8 and 28 are fixed to the housing portions 9 and 29. In the above description, the fluid dynamic bearing devices 1 and 21 are described. However, the fluid dynamic bearing devices 1 and 21 may be configured by integrating them. In that case, the integral part of the housing parts 9 and 29 and the sleeve parts 8 and 28 can be formed by resin injection molding, or can be formed by metal forging.

  Moreover, in the above embodiment (1st, 2nd embodiment), the convex part 10 was made into substantially cylindrical shape, and this convex part 10 was formed in the end surface 9f1 of the outer peripheral side step part 9f at three places at equal intervals in the circumferential direction. Although the case has been described, it is of course possible to adopt other forms (hereinafter, the convex portion 30 is also common). For example, FIG. 6 shows a case where three convex portions 13 having a rectangular cross section are formed at equal intervals in the circumferential direction. In this case, the outer peripheral side step portion 9f has a shape in which a plurality of nuisances as so-called relief portions are provided between the adjacent convex portions 13 and 13. Further, the end surface 13a of the convex portion 13 becomes the reference surface. Or FIG. 7 has illustrated the case where the annular convex part (ridge part) 14 was provided in the outer-diameter side of the outer peripheral side step part 9f. In this case, the outer peripheral side step portion 9f has a shape (a relief portion) in which the inner peripheral side excluding the convex portion 14 is concave over the entire circumference. Moreover, the end surface 14a which makes the annular shape of the convex portion 14 becomes the reference surface. Of course, as long as the area of the end face is smaller than the area of the end face provided with the convex portion 10 (the end face 9f1 of the outer peripheral step 9f in FIG. It can be provided intermittently in the radial direction.

  In the first and second embodiments, the case where the convex portion 10 is formed on the outer peripheral side step portion 9f provided between the seal surface 9d and the cylindrical surface 9e is exemplified. As long as 10a functions as a reference surface that defines the relative position in the axial direction between the motor 6 and other members on the motor side, it can be formed at any location. As a place where the convex portion 10 can be formed other than the stepped portion, for example, the axial end surface 9g located on the side opposite to the first thrust bearing surface 9a (sealing side) of the housing portion 9, particularly the axial end surface of the housing portion 9 (See FIGS. 2 and 5 to 7).

  In the above embodiment, the case where the end surface 10a serving as the reference surface is finished by press working has been described, but the present invention is similarly applied even when other finishing work such as cutting work is used. can do.

  Moreover, in the above embodiment, the radial bearing portions R1, R2 and the thrust bearing portions T1, T2, T11 are exemplified as a configuration in which the dynamic pressure action of the lubricating fluid is generated by the dynamic pressure grooves having a herringbone shape or a spiral shape. However, the present invention is not limited to this.

  For example, although not shown in the drawings as radial bearing portions R1 and R2, a so-called step-like dynamic pressure generating portion in which axial grooves are formed at a plurality of locations in the circumferential direction of the sleeve portion 8 or in the circumferential direction. A so-called multi-arc bearing in which a plurality of arc surfaces are arranged and a wedge-shaped radial clearance (bearing clearance) is formed between the outer peripheral surfaces 2a and 22a of the opposing shaft members 2 and 22 may be employed. .

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

  Further, at least one of the thrust bearing portions T1, T2, and T11 is also omitted in the figure, but a plurality of radial groove-shaped dynamic pressure grooves are provided at predetermined intervals in the circumferential direction in a region that becomes a thrust bearing surface. A so-called step bearing or a corrugated bearing (where the step mold is a corrugated bearing) can also be used.

  In the above description, the case where the radial bearing surface (inner peripheral surface 8a) and the thrust bearing surfaces 9a and 29a are formed on the sleeve portions 8 and 28 and the housing portions 9 and 29 are described. The bearing surface on which the dynamic pressure generating portion is formed is not limited to the fixed-side member, and may be provided, for example, on the shaft member 2, the flange portion 2 b, or the hub portion 11 side (rotation side) facing them.

  Further, in the above description, the lubricating oil is exemplified as the fluid that fills the inside of the hydrodynamic bearing device 1 and causes the hydrodynamic action in the radial bearing gap or the thrust bearing gap. A fluid capable of generating a dynamic pressure action, for example, a gas such as air, a fluid lubricant such as a magnetic fluid, or lubricating grease may be used.

It is sectional drawing of the spindle motor incorporating the dynamic pressure bearing apparatus which concerns on 1st Embodiment of this invention. It is sectional drawing of the hydrodynamic bearing apparatus which concerns on 1st Embodiment. It is sectional drawing of a sleeve part. It is the upper end view which looked at the housing part from the direction of arrow A. FIG. 6 is a perspective view of the housing part as seen from the direction of arrow B. It is a perspective view which shows the other structure of a housing part. It is a perspective view which shows the other structure of a housing part. It is sectional drawing of the hydrodynamic bearing apparatus which concerns on 2nd Embodiment of this invention.

Explanation of symbols

1, 21 Dynamic bearing device 2, 22 Shaft member 3, 23 Rotating member 4 Stator coil 5 Rotor magnet 6 Bracket 6a Inner peripheral surface 6b End surface 8 Sleeve portion 9, 29 Housing portion 9a, 29a First thrust bearing surface 9a1 Dynamic pressure Groove 9d Sealing surface 9e Cylindrical surface 9f, 29f Outer peripheral side step portion 9f1, 29f1 End surface 10, 13, 14, 30 Protruding portion 10a, 13a, 14a, 30a End surface 11 Hub portion 11a Disk portion 11b Tubular portion 11c Disk mounting surface 31 Locking member R1, R2 Radial bearing portion T1, T2, T11 Thrust bearing portion S Seal space

Claims (6)

A shaft member, a thrust bearing portion that imparts a thrust force in the thrust direction to the shaft member by the dynamic pressure action of fluid generated in the thrust bearing gap, a sleeve portion in which the shaft member is inserted on the inner periphery, and an outer diameter side of the sleeve portion A hydrodynamic bearing device incorporated in a motor.
The hydrodynamic bearing device, wherein the housing portion includes a reference surface that defines an axial relative position with a member on the motor side, and a relief portion adjacent to the reference surface.   The hydrodynamic bearing device according to claim 1, wherein the reference surface is formed by plastic working.   The hydrodynamic bearing device according to claim 1, wherein a thrust bearing surface facing the thrust bearing gap is provided in the housing portion, and a parallelism of the reference surface with respect to the thrust bearing surface is 10 μm or less.   The hydrodynamic bearing device according to claim 1, wherein the flatness of the reference surface is 10 μm or less.   The hydrodynamic bearing device according to claim 1, wherein the reference surface and the relief portion are arranged in parallel in a circumferential direction or a radial direction.   A hydrodynamic bearing device according to any one of claims 1 to 5, a stator coil, and a rotor magnet that generates an exciting force between the stator coils, opposite to the thrust force in the thrust direction by the thrust bearing portion. A motor in which an axial thrust force is applied to a shaft member.

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