JP2006207787A - Housing for dynamic pressure bearing device and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a housing for dynamic pressure bearing device and a manufacturing method therefor, heightening the shape accuracy of this type of housing at a low cost. <P>SOLUTION: After a sealing surface 7d and a cylindrical outer peripheral surface 7e provided in the outer periphery of the housing are formed by forging, an inner peripheral surface 7c is formed by forging. In the process of forming the inner peripheral surface, punching is performed from the thin side of a housing raw material 7' (the counter-thrust bearing surface 7a side) to the thick side (the thrust bearing surface 7a side). Thus, the perpendicularity of the thrust bearing surface 7a based on the inner peripheral surface 7c or the outer peripheral surface 7e is finished to 20 μm or less. The coaxiality of the sealing surface 7d based on the inner peripheral surface 7c or the outer peripheral surface 7e is finished to 20 μm or less. The coaxiality of the outer peripheral surface 7e based on the inner peripheral surface 7c is finished to 20 μm or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a housing for a hydrodynamic bearing device and a method for manufacturing the same. The hydrodynamic bearing device referred to here is an information device, for example, a magnetic disk device such as an HDD, an optical disk device such as a CD-ROM, CD-R / RW, or DVD-ROM / RAM, or a magneto-optical disk device such as an MD or MO. This is suitable for a spindle motor, a polygon scanner motor of a laser beam printer (LBP), and other small motors.

  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 rotating member in the radial direction and the thrust bearing portion that supports the thrust direction in the thrust direction are configured by the hydrodynamic bearing. There is. As a thrust bearing portion in this type of dynamic pressure bearing device, for example, both end surfaces of a flange portion of a shaft portion provided on a rotating member, and opposite surfaces thereof (an end surface of a bearing sleeve, a thrust member fixed to a housing, or It is known that a dynamic pressure groove as a dynamic pressure generating portion is formed on either one of the end surfaces of the lid member and the like, and a thrust bearing gap is formed between both surfaces (see, for example, Patent Document 1).
JP 2003-239951 A

  Recently, in order to cope with an increase in information recording density and high-speed rotation in information equipment, the spindle motor for the information equipment has been required to have higher rotational accuracy. Higher rotational accuracy is also required for the hydrodynamic bearing device incorporated in the motor.

  In order to improve the rotational accuracy (bearing performance) of the hydrodynamic bearing device, it is important to manage the radial bearing gap and the thrust bearing gap in which dynamic pressure is generated with high accuracy. For this reason, high dimensional accuracy is required for the components of the hydrodynamic bearing device involved in the formation of the bearing gaps.

  On the other hand, recently, with the aim of reducing the size of the bearing device and reducing the number of parts, the thrust bearing gap is formed between the end surface of the housing and the end surface of the rotating member (for example, a disk hub) facing the housing. It is being considered to form.

  In this case, in order to achieve high rotational accuracy of the bearing device, high dimensional accuracy is required not only for the shaft member and the bearing sleeve but also for the end surface region that becomes the thrust bearing surface of the housing. Alternatively, excellent high shape accuracy is required between other housing constituent surfaces. However, in the existing processing method, since the processing cost is remarkably increased, it is difficult to achieve higher accuracy.

  An object of the present invention is to provide a housing for a hydrodynamic bearing device with improved shape accuracy.

  Another object of the present invention is to provide a method of manufacturing a housing for a hydrodynamic bearing device that can increase the shape accuracy of this type of housing at low cost.

  In order to solve the above problems, the present invention is a cylindrical forged product, comprising a thrust bearing surface that forms a thrust bearing gap with a rotating member to be supported, and is based on an inner peripheral surface or an outer peripheral surface. A thrust bearing device housing having a perpendicularity of 20 μm or less is provided. The perpendicularity here refers to a reference axis line (here, a line connecting the centers of cross-sectional contour lines in each cross section of the inner peripheral surface or the outer peripheral surface; hereinafter simply referred to as an axial line of the inner peripheral surface or the outer peripheral surface). This is the magnitude of the deviation of a planar feature (referred to here as a thrust bearing surface) that should be parallel from a right-angled geometric plane, which is the reference axis (inner or outer axis) When the plane shape (thrust bearing surface) is sandwiched between two geometric parallel planes perpendicular to the plane, the distance between the two planes is expressed as the distance between the two parallel planes being minimized. The thrust bearing surface referred to here is sufficient if it 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.

  In order to solve the above-mentioned problems, the present invention provides a cylindrical forged product, in which a seal is formed between a thrust bearing surface that forms a thrust bearing gap with the rotating member to be supported, and the rotating member. There is provided a housing for a hydrodynamic bearing device, including a seal surface that forms a space, and the coaxiality of the seal surface with respect to the inner peripheral surface or the outer peripheral surface is 20 μm or less. The coaxiality here is an axis that should be on the same straight line as the reference axis (in this case, the axis of the inner or outer peripheral surface) (here, a line connecting the centers of the cross-sectional contour lines in each cross section of the seal surface) In the following, the magnitude of the deviation from the reference axis of the seal surface) is simply referred to as the reference axis (inner peripheral surface or outer peripheral surface) including all of the above axes (seal surface axis). Of the geometrically correct cylinders that are coaxial with the axis), the diameter of the smallest cylinder is represented.

  In order to solve the above-mentioned problem, the present invention is a cylindrical forged product comprising a thrust bearing surface that forms a thrust bearing gap with a rotating member to be supported, with the inner peripheral surface as a reference. A hydrodynamic bearing device housing in which the coaxiality of the outer peripheral surface is 20 μm or less is provided. The concentricity here refers to the magnitude of the deviation from the reference axis of the axis (here, the axis of the outer peripheral surface) that should be collinear with the reference axis (here, the axis of the inner peripheral surface). In other words, the size is expressed by the diameter of the smallest cylinder among geometrically correct cylinders that are coaxial with the reference axis (the axis of the inner peripheral surface) including all of the above-mentioned axes (the axis of the outer peripheral surface).

  The geometric deviation (shape accuracy) between the housing constituent surfaces is defined based on the inventor's knowledge described below.

  The perpendicularity of the thrust bearing surface with respect to the inner circumferential surface or the outer circumferential surface greatly affects the accuracy of the thrust bearing gap between the thrust bearing surface and the end surface of the rotating member facing the thrust bearing surface. That is, when the perpendicularity of the thrust bearing surface exceeds 20 μm, the difference between the large and small portions of the thrust bearing gap becomes significant. For this reason, the bearing loss increases at a location where the bearing clearance is small, for example, the rotational torque of the shaft member is increased compared to other locations, and the bearing rigidity is reduced at locations where the bearing clearance is large, compared to other locations. (NRRO) may be deteriorated. In addition, after the motor is started, the time required for the rotating member to rise increases, and sliding wear during that time may increase, which may adversely affect the bearing life. From such a viewpoint, in the present invention, the perpendicularity of the thrust bearing surface based on the inner peripheral surface or the outer peripheral surface is set to 20 μm or less.

  Further, the coaxiality of the seal surface with respect to the inner peripheral surface or outer peripheral surface of the housing is important when a seal space is formed between the seal surface and the rotating member facing the seal surface. If this coaxiality is not sufficient (over 20 μm), even if the bearing sleeve is assembled to the housing with high accuracy, the sealing surface of the housing should be the surface on the rotating member side that should face this surface. On the other hand, it is difficult to dispose them at regular intervals. As a result, the seal gap in the seal space formed between the two surfaces varies in the circumferential direction, which may lead to a decrease in seal performance. From this point of view, in the present invention, the coaxiality of the seal surface based on the inner peripheral surface or the outer peripheral surface is set to 20 μm or less.

  Further, as described above, the inner peripheral surface of the housing is a reference for assembling the rotating member (shaft portion) with respect to the bearing sleeve, whereas the outer peripheral surface of the housing is assembled with the bearing sleeve and the rotating member on the housing. This is a position reference when the hydrodynamic bearing device is incorporated into the motor. Therefore, if the concentricity between both surfaces is poor (exceeds 20 μm), for example, the assembly accuracy with respect to the fixed side member (bracket, etc.) of the motor will be lowered. It may adversely affect the rotation accuracy of the motor, for example, it will be difficult to manage. From this viewpoint, in the present invention, the coaxiality of the outer peripheral surface with respect to the inner peripheral surface of the housing is set to 20 μm or less.

  In addition to this, the shape accuracy of the housing to be satisfied includes, for example, the perpendicularity of the thrust bearing surface with respect to the axis of the seal surface, and this perpendicularity is preferably 20 μm or less. As another shape accuracy to be satisfied, for example, there is runout of the seal surface based on the axis of the inner peripheral surface, and this runout is desirably 20 μm or less. Further, as another shape accuracy to be satisfied, for example, there is a contour degree of the seal surface, and it is desirable that this contour degree is 20 μm or less. It is sufficient that the geometrical deviation (perpendicularity, surface runout, degree of contour) regarding these seal surfaces satisfies at least one of them, but it is more preferable that two or more of the geometrical deviations are satisfied.

  In order to solve the above-mentioned problems, the present invention provides a seal that forms a seal space between a rotating bearing and a thrust bearing surface that forms a thrust bearing gap between the rotating member to be supported and a cylindrical shape. When manufacturing a housing for a hydrodynamic bearing device having a surface, a method for manufacturing a housing for a hydrodynamic bearing device including a step of forging the outer peripheral surface of the housing and then forging the inner peripheral surface is provided.

  The cylindrical housing is often formed with a thicker thickness on the thrust bearing surface side than on the anti-thrust bearing surface side, for example, for the purpose of securing a thrust bearing area. In such a case, for example, if the outer peripheral surface is forged after forging the inner peripheral surface of the housing, the hole previously formed in the inner periphery may be deformed, and the accuracy of this hole may not be maintained, In addition, it may be difficult to form the thick part. On the other hand, if the inner peripheral surface is forged after the outer peripheral surface of the housing is forged as in the present invention, this problem can be solved and the thrust bearing surface can be formed with high accuracy. In addition, since these moldings are performed by forging, the cycle time can be shortened compared to machining such as turning, and the material cost can be reduced by increasing the ratio of the amount of material after processing to the amount of material before forming. It becomes. In addition, there is no generation of swarf etc. compared to machining such as turning, and the generation of burrs can be suppressed, so that it is possible to further reduce costs by simplifying cleaning work and eliminating the need for deburring. .

  Forging of the inner peripheral surface of the housing is usually performed by punching the housing material in the axial direction. At this time, it is preferable to punch the housing material from the axially anti-thrust bearing surface side toward the thrust bearing surface side. According to this method, deformation on the thrust bearing surface side due to punching can be reduced. Therefore, it is possible to mold the inner peripheral surface while maintaining the shape of the outer peripheral surface formed earlier with high accuracy.

  The housing for a hydrodynamic bearing device manufactured through the above procedure can be provided, for example, as having excellent shape accuracy (perpendicularity, coaxiality, inclination) between the housing constituent surfaces.

  The housing may be configured such that a dynamic pressure generating portion is formed on the thrust bearing surface. In this case, the rotating member is supported in a non-contact manner in the thrust direction by the dynamic pressure action of the fluid generated in the thrust bearing gap between the thrust bearing surface of the housing and the end surface of the rotating member facing the housing.

  Further, the housing may be configured such that both ends in the axial direction are opened, a thrust bearing surface is provided on one end side, and the other end side is sealed with a lid member.

  The housing having the above-described configuration can be provided as, for example, a fluid dynamic bearing device having the housing. The hydrodynamic bearing device can also be provided as a motor provided with the hydrodynamic bearing device.

  As described above, according to the present invention, each component surface of the housing, including the thrust bearing surface of the housing for the hydrodynamic bearing device, can be processed with high accuracy, and the thrust formed between the housing and the rotating member. The bearing gap can be managed with high accuracy. In addition, by adopting forging as the processing means at that time, it becomes possible to reduce the processing cost.

  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 the hydrodynamic bearing device 1 that rotatably supports the rotating member 3 including the shaft portion 2 through a gap in the radial direction, for example. The stator coil 4 and the rotor magnet 5 and the motor bracket 6 are provided. The stator coil 4 is attached to the outer periphery of the motor bracket 6, and the rotor magnet 5 is attached to the outer periphery of the rotating member 3. The housing 7 of the hydrodynamic bearing device 1 is fixed to the inner periphery of the motor bracket 6. The rotating member 3 holds one or a plurality of disk-shaped information recording media (hereinafter simply referred to as disks) such as magnetic disks. In the spindle motor configured as described above, when the stator coil 4 is energized, the rotor magnet 5 is rotated by the electromagnetic force generated between the stator coil 4 and the rotor magnet 5. The disk D held by the member 3 rotates integrally with the shaft portion 2.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a housing 7, a bearing sleeve 8 fixed to the housing 7, and a rotating member 3 that rotates relative to the housing 7 and the bearing sleeve 8 as main components. For convenience of explanation, in the housing 7 openings formed at both ends in the axial direction, the side sealed by the lid member 11 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 9 that covers the opening side of the housing 7 and a shaft portion 2 that is inserted into the inner periphery of the bearing sleeve 8.

  The hub portion 9 includes a disc portion 9a that covers the opening side (upper side) of the housing 7, a cylindrical portion 9b that extends axially downward from the outer peripheral portion of the disc portion 9a, and a disk that is provided on the outer periphery of the cylindrical portion 9b. A mounting surface 9c and a flange 9d are provided. A disc (not shown) is fitted on the outer periphery of the disk portion 9a and placed on the disc mounting surface 9c. Then, the disc is held on the hub portion 9 by appropriate holding means (such as a clamper) not shown.

  The shaft portion 2 is formed integrally with the hub portion 9 in this embodiment, and includes a flange portion 10 as a separate member at the lower end thereof. The flange portion 10 is made of metal and is fixed to the shaft portion 2 by means such as screw connection.

  The bearing sleeve 8 is formed in a cylindrical shape, for example, with a porous body made of sintered metal, in particular, a sintered metal porous body mainly composed of copper.

  A dynamic pressure groove as a radial dynamic pressure generating portion is formed on the entire inner surface 8a of the bearing sleeve 8 or a partial cylindrical region. 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. In the formation region of the upper dynamic pressure groove 8a1, the dynamic pressure groove 8a1 is formed to be axially asymmetric with respect to the axial center m (the axial center of the upper and lower inclined groove regions). The axial dimension X1 of the upper region is larger than the axial dimension X2 of the lower region.

  For example, although not shown in the drawing, a region in which a plurality of dynamic pressure grooves are arranged in a spiral shape is formed on the entire lower surface 8c of the bearing sleeve 8 or a partial annular region. This dynamic pressure groove forming region is opposed to the upper end surface 10a of the flange portion 10 as a thrust bearing surface, and the thrust of the second thrust bearing portion T2 is between the upper end surface 10a and the shaft portion 2 (rotating member 3) when rotating. A bearing gap is formed (see FIG. 2).

  The housing 7 is formed in a cylindrical shape with a metal material such as stainless steel. The housing 7 has a shape in which both ends in the axial direction are opened, and the other end is sealed with a lid member 11. A thrust bearing surface 7 a is provided on the entire end surface (upper end surface) or a partial annular region on one end side. In this embodiment, a region in which a plurality of dynamic pressure grooves 7a1 are arranged in a spiral shape is formed on the thrust bearing surface 7a as a thrust dynamic pressure generating portion, for example, as shown in FIG. This thrust bearing surface 7a (dynamic pressure groove 7a1 formation region) is opposed to the lower end surface 9a1 of the disk portion 9a of the hub portion 9, and a first thrust bearing described later between the lower end surface 9a1 and the rotating member 3 when rotating. A thrust bearing gap of the portion T1 is formed (see FIG. 2).

  The lid member 11 that seals the other end side of the housing 7 is formed of a metal material or a resin material, and is fixed to a step portion 7 b provided on the inner peripheral side of the other end of the housing 7. Here, the fixing means is not particularly limited, and for example, means such as adhesion (including loose adhesion and press-fit adhesion), press-fit, welding (for example, ultrasonic welding), welding (for example, laser welding), combinations of materials and requirements. It can be appropriately selected according to the assembled strength, sealing performance and the like.

  The outer peripheral surface 8b of the bearing sleeve 8 is fixed to the inner peripheral surface 7c of the housing 7 by appropriate means such as bonding (including loose bonding and press-fitting bonding), press-fitting, and welding.

  On the outer periphery of the housing 7, a tapered seal surface 7 d that gradually increases in diameter upward is formed. The tapered seal surface 7d forms an annular seal space S whose radial dimension is gradually reduced from the sealing side of the housing 7 upward from the inner peripheral surface 9b1 of the cylindrical portion 9b. 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 portion 2 and the hub portion 9 are rotated.

  A cylindrical outer peripheral surface 7e having a constant diameter is formed at the lower end of the outer periphery of the housing 7. The cylindrical outer peripheral surface 7e is fixed to the inner peripheral surface 6a of the motor bracket 6 by means such as adhesion or press-fitting, whereby the dynamic pressure bearing device 1 is incorporated into the motor.

  The hydrodynamic bearing device 1 is filled with lubricating oil including the internal pores of the bearing sleeve 8 (pores of the porous body tissue). The oil level of the lubricating oil is always maintained in the seal space S.

  When the shaft portion 2 (rotating member 3) rotates, a region (a region where two dynamic pressure grooves 8a1 and 8a2 are formed) on the inner peripheral surface 8a of the bearing sleeve 8 is formed on the outer peripheral surface 2a of the shaft portion 2. And through a radial bearing gap. As the shaft portion 2 rotates, the lubricating oil in the radial bearing gap is pushed into the axial center m 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 portion 2 in a non-contact manner are configured by the dynamic pressure action of the dynamic pressure groove.

  At the same time, the thrust bearing clearance between the thrust bearing surface 7a (dynamic pressure groove 7a1 formation region) of the housing 7 and the lower end surface 9a1 of the hub portion 9 (disk portion 9a) opposed thereto, and below the bearing sleeve 8 An oil film of lubricating oil is formed in the thrust bearing gap between the end surface 8c (dynamic pressure groove forming region) and the upper end surface 10a of the flange portion 10 facing the end surface 8c by the dynamic pressure action of the dynamic pressure groove. The pressure of these oil films forms a first thrust bearing portion T1 and a second thrust bearing portion T2 that support the rotating member 3 in a non-contact manner in the thrust direction.

  Hereinafter, an example of the manufacturing method of the housing 7 which comprises the fluid dynamic bearing apparatus 1 is demonstrated based on FIG.

  In this embodiment, the housing 7 is manufactured through three steps: an outer peripheral surface forming step (A), an inner peripheral surface forming step (B), and a thrust bearing surface forming step (C).

(A) Outer peripheral surface forming step First, after the wire is linearized, a cylindrical blank material cut to an appropriate size is cold forged (compressed) in a pair of molds (not shown), and the outer periphery of the housing 7 Surfaces (seal surface 7d and cylindrical outer peripheral surface 7e) are formed. Note that the cold forging method is not limited to the above-described upsetting, and various forming methods such as forward extrusion or a combination of forward extrusion and upsetting can be used.

(B) Inner peripheral surface shaping | molding process Next, the inner peripheral surface 7c of the housing 7 which should be shape | molded by cold forging of housing raw material 7 'which shape | molded the sealing surface 7d and the cylindrical outer peripheral surface 7e on the outer periphery. For example, as shown in FIG. 5, the die used is a die 16 that restrains the outer peripheral surface of the housing material 7 ′ and an upper punch that restrains the housing material 7 ′ in the axial direction from the thrust bearing surface 7a to be molded. 17 and a lower punch (rod) 18 having a molding surface 18a corresponding to the inner peripheral surface 7c of the housing 7 to be molded. As shown in the figure, in a state where the housing material 7 ′ is constrained in the radial direction and the axial direction, the rod 18 is raised (in the direction of the arrow in the figure), and the inner peripheral portion of the housing material 7 ′ is moved to the lower end side (anti-thrust). Punching is performed from the bearing surface 7a side) toward the upper end side (thrust bearing surface 7a side). As a result, the housing material 7 ′ is opened at both ends in the axial direction, and the inner periphery thereof is molded into a shape that follows the molding surface 18a (the inner peripheral surface 7c of the finished product). In this embodiment, the inner peripheral surface 7c and the stepped portion 7b of the finished product are simultaneously formed by using the rod 18 having the formed portion 18b corresponding to the stepped portion 7b in addition to the forming surface 18a of the inner peripheral surface 7c. The

  Thus, by forging the outer peripheral surface of the housing 7 prior to the forging of the inner peripheral surface 7c, undesired deformation of the housing material 7 ′, particularly the thick portion (upper side in the figure), during pressurization. Undesirable deformation can be avoided, and the shape of the seal surface 7d provided on the outer periphery can be maintained with high accuracy.

(C) Thrust bearing surface forming step After the above steps (A) and (B), the thrust bearing surface 7a of the housing 7 to be formed is formed by cold forging of the housing material 7 '. For example, the die 16 and the rod 18 shown in FIG. 5 and the lower end surface of the upper punch 17 shown in FIG. 5 are omitted in the mold used in this molding process, but the molding corresponding to the thrust bearing surface 7a of the housing 7 to be molded is omitted. It is composed of the surface. In a state where the housing material 7 ′ is constrained in the radial direction by the die 16 and the rod 18, the upper punch 17 is lowered (in the direction of the arrow in the figure), and the molding surface (not shown) of the upper punch 17 is formed on the housing material 7 ′. Press the upper end with a predetermined pressure. As a result, the upper end surface of the housing material 7 'is molded into a shape that follows the molding surface (the thrust bearing surface 7a of the finished product). Further, in this embodiment, although not shown in the figure, the housing material 7 ′ is obtained by using a groove die corresponding to the dynamic pressure groove 7a1 as the dynamic pressure generating portion formed in advance on the molding surface of the upper punch 17. At the same time as the thrust bearing surface 7a is formed, the shape of the dynamic pressure groove 7a1 is formed.

  The housing 7 (see FIG. 2) as a finished product is formed through the above steps (A) to (C).

  In the case of the housing 7 manufactured by the above manufacturing method, the perpendicularity of the thrust bearing surface 7a based on the inner peripheral surface 7c or the outer peripheral surface 7e can be finished to 20 μm or less (preferably 10 μm or less).

  Further, the coaxiality of the seal surface 7d based on the inner peripheral surface 7c or the outer peripheral surface 7e can be finished to 20 μm or less (preferably 10 μm or less).

  Further, the coaxiality of the outer peripheral surface 7e with reference to the inner peripheral surface 7c can be finished to 20 μm or less (preferably 10 μm or less).

  Further, the perpendicularity of the thrust bearing surface 7a with respect to the axis of the seal surface 7d can be finished to 20 μm or less (preferably 10 μm or less).

  Further, the runout of the seal surface 7d with reference to the axis of the inner peripheral surface 7c can be finished to 20 μm or less (preferably 10 μm or less).

  Further, the contour degree of the seal surface 7d can be finished to 20 μm or less (desirably 10 μm or less).

  The hydrodynamic bearing device 1 with improved bearing performance, rotational accuracy, sealing performance, etc. by suppressing the geometric deviation (shape accuracy) between the constituent surfaces of the housing 7 to a value within the above range, or the hydrodynamic bearing device. 1 can be provided.

  The above steps (A) to (C) are merely examples of molds that can be configured, and each shape accuracy (such as squareness and coaxiality) of the molded product is set to a value within the above range. Other mold configurations may be employed as long as they can be set.

  Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. In addition, about a matter common with 1st Embodiment, description is abbreviate | omitted below.

  FIG. 6 shows a configuration example of a spindle motor for information equipment in which the hydrodynamic bearing device 21 according to the second embodiment is incorporated. This spindle motor is also used in a disk drive device such as an HDD, and is opposed to a hydrodynamic bearing device 21 that rotatably supports a rotating member 23 having a shaft portion 22 through a gap in the radial direction, for example. A stator coil 24 and a rotor magnet 25, and a bracket 26 fixed to the outer periphery of a housing 27 of the hydrodynamic bearing device 21 are provided.

  FIG. 7 shows the hydrodynamic bearing device 21. The hydrodynamic bearing device 21 is formed with respect to the housing 27 and the bearing sleeve 28 in a state where the shaft 27 is inserted into the inner periphery of the housing 27, the bearing sleeve 28 fixed to the inner periphery of the housing 27, and the bearing 27. And the rotating member 23 that rotates relative to the main component.

  The rotating member 23 is mainly composed of a shaft portion 22 and a hub portion 29. Of these, the shaft portion 22 is formed in a shaft shape having the same diameter with a metal material such as stainless steel.

  In this embodiment, the hub portion 29 is formed by injection molding a resin material using the shaft portion 22 as an insert part. As shown in FIG. 7, the hub portion 29 includes a disc portion 29a that covers the opening side (upper side in the drawing) of the housing 27, a cylindrical portion 29b that extends downward in the axial direction from the outer peripheral portion of the disc portion 29a, and a cylindrical shape. A disk mounting surface 29c and a flange part 29d provided on the outer periphery of the part 29b are provided. The hub portion 29 may be made of, for example, metal. In that case, the hub portion 29 and the shaft portion 22 may be integrally formed.

  The housing 27 is a forged molded product of a metal material (for example, stainless steel) and is formed in a bottomed cylindrical shape. The housing 27 includes a cylindrical side portion 27a and a bottom portion 27b provided at the lower end of the side portion 27a. The bottom portion 27b is formed integrally with the side portion 27a.

  A thrust bearing surface 27c is formed on the entire or partial annular region of the opening side end surface (upper end surface) of the housing 27. Although not shown as a thrust dynamic pressure generating portion on the thrust bearing surface 27c, for example, FIG. A region in which the dynamic pressure grooves are arranged in the same shape as 4 is formed. This thrust bearing surface (dynamic pressure groove forming region) 27c faces the lower end surface 29a1 of the disk portion 29a of the hub portion 29, and will be described later with the lower end surface 29a1 when the shaft portion 22 (rotating member 23) rotates. A thrust bearing gap of the thrust bearing portion T11 is formed (see FIG. 7).

  On the outer periphery of the upper portion of the side portion 27a, a tapered seal surface 27e that gradually increases in diameter upward is formed. This seal surface 27e and the inner peripheral surface 29b1 of the cylindrical portion 29b provided on the hub portion 29 are formed. Between the two, a tapered seal space S ′ that gradually decreases upward is formed. The seal space S 'communicates with the outer diameter side of the thrust bearing gap of the thrust bearing portion T11 when the shaft portion 22 and the hub portion 29 are rotated. Further, the inner periphery of the lower end of the cylindrical portion 29b of the hub portion 29 is engaged with the housing 27 in the axial direction when the shaft portion 22 (rotating member 23) is relatively displaced in the axial direction, so that the shaft portion 22 is engaged. A locking member 30 for locking is attached.

  The bearing sleeve 28 is formed in a cylindrical shape with a porous body made of, for example, a metal non-porous body or sintered metal, in particular, a sintered metal porous body mainly composed of copper, and bonded (loose bonding or press-fit bonding). And fixed at a predetermined position on the inner peripheral surface 27d of the housing 27 by fixing means such as press fitting and welding.

  In this embodiment, as described above, a thrust bearing gap is formed only between the thrust bearing surface 27c of the housing 27 and the lower end surface 29a1 of the disk portion 29a opposite to the thrust bearing surface 27c. No gap is formed. Therefore, the bearing sleeve 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.

  In the hydrodynamic bearing device 21 having the above-described configuration in which the internal space of the housing 27 including the seal space S ′ and the thrust bearing gap is filled with lubricant, the inner periphery of the bearing sleeve 28 is rotated when the shaft portion 22 (rotating member 23) is rotated. The area (two upper and lower areas) of the surface 28a serving as the radial bearing surface is opposed to the outer peripheral surface 22a of the shaft portion 22 via the radial bearing gap. As the shaft portion 22 rotates, the lubricating oil in the radial bearing gap is pushed toward the axial center side of the dynamic pressure groove, and the pressure rises. The first radial bearing portion R11 and the second radial bearing portion R12 that support the shaft portion 22 in a non-contact manner are configured by the dynamic pressure action of the dynamic pressure groove.

  At the same time, the oil film of the lubricating oil is also applied to the thrust bearing gap between the lower end surface 29a1 of the hub portion 29 and the thrust bearing surface (dynamic pressure groove forming region) 27c of the housing 27 opposed thereto by the dynamic pressure action of the dynamic pressure groove. The thrust bearing portion T11 that supports the shaft portion 22 (the rotating member 23) in a non-contact manner so as to be rotatable in the thrust direction is configured by the pressure of the oil film.

  The housing 27 in this embodiment is also manufactured through three steps, for example, an outer peripheral surface forming step (A), an inner peripheral surface forming step (B), and a thrust bearing surface forming step (C). Although the illustration is omitted, for example, although not shown, in the inner peripheral surface forming step (B), the opening direction when the inner peripheral portion of the housing material is opened is changed from the axial thrust bearing surface 27c side to the anti-thrust bearing. The point is the direction toward the surface 27c.

  The housing 27 (see FIG. 7) as a finished product is formed through the above steps.

  In the case of the housing 27 manufactured by the above-described manufacturing method, the perpendicularity of the thrust bearing surface 27c with reference to the inner peripheral surface 27d or the outer peripheral surface 27f can be finished to 20 μm or less (preferably 10 μm or less).

  Further, the coaxiality of the seal surface 27e with reference to the inner peripheral surface 27d or the outer peripheral surface 27f can be finished to 20 μm or less (preferably 10 μm or less).

  Further, the coaxiality of the outer peripheral surface 27f with reference to the inner peripheral surface 27d can be finished to 20 μm or less (preferably 10 μm or less).

  Further, the perpendicularity of the thrust bearing surface 27c with respect to the axis of the seal surface 27e can be finished to 20 μm or less (preferably 10 μm or less).

  Further, the runout of the seal surface 27e with reference to the axis of the inner peripheral surface 27d can be finished to 20 μm or less (preferably 10 μm or less).

  Further, the contour degree of the seal surface 27e can be finished to 20 μm or less (preferably 10 μm or less).

  By suppressing the geometric deviation (shape accuracy) between the constituent surfaces of the housing 27 to a value within the above range, the hydrodynamic bearing device 21 with improved bearing performance, rotational accuracy, sealing performance, etc., or the hydrodynamic bearing device. A motor with 21 can be provided.

  The first and second embodiments of the present invention have been described above, but the present invention is not limited to this embodiment.

  In the above embodiment, the case where the housing 7 (27) is forged with a relatively hard metal such as SUS is exemplified. However, the case where the housing 7 (27) is forged with a relatively soft metal such as brass is also exemplified. The present invention can be similarly applied.

  Moreover, in the above embodiment, as the dynamic pressure bearings constituting the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2, for example, a dynamic pressure generating portion including a herringbone shape or a spiral shape dynamic pressure groove is used. Although the bearing is illustrated, the configuration of the dynamic pressure generating unit is not limited to this. As the radial bearing portions R1 and R2, for example, multi-arc bearings, step bearings, taper bearings, taper / flat bearings, and the like can be used.

  One or both of the thrust bearing portions T1 and T2, for example, are not shown 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 serving as a thrust bearing surface. It can also be constituted by a step bearing, a so-called corrugated bearing (the corrugated step mold) or the like.

  Moreover, although the radial bearing part R1 and R2 and the thrust bearing part T1 and T2 were comprised by the dynamic pressure bearing in the above embodiment, it can also comprise by bearings other than this. For example, the inner peripheral surface 8a of the bearing sleeve 8 (28) serving as a radial bearing surface is a perfect circular inner peripheral surface not provided with a dynamic pressure generating portion such as the dynamic pressure grooves 8a1, 8a2, and a shaft opposed to the inner peripheral surface. A so-called perfect circle bearing can be constituted by the perfect circular outer peripheral surface 2 a of the portion 2. Of course, the configuration related to the radial bearing portions R1 and R2 or the thrust bearing portions T1 and T2 can be similarly applied to the radial bearing portions R11 and R12 or the thrust bearing portion T11.

  Moreover, in the above embodiment, the inside of the hydrodynamic bearing device 1 (21) is filled, and the radial bearing gap between the bearing sleeve 8 and the shaft portion 2, the space between the bearing sleeve 8 and the shaft portion 2, or Lubricating oil is exemplified as the fluid that forms the lubricating film in the thrust bearing gap between the housing 7 and the rotating member 3 (hub portion 9), but other fluids that can form a lubricating film in each bearing gap, For example, a gas such as air, a fluid lubricant such as magnetic fluid, or lubricating grease may be used.

1 is a cross-sectional view of a spindle motor for information equipment incorporating a fluid dynamic bearing device according to a first embodiment of the present invention. It is sectional drawing of a hydrodynamic bearing apparatus. It is a longitudinal cross-sectional view of a bearing sleeve. It is the figure which looked at the housing from the direction of arrow A. It is the schematic which shows an example of the manufacturing process of a housing. It is sectional drawing of the spindle motor for information devices incorporating the dynamic pressure bearing apparatus which concerns on 2nd Embodiment of this invention. It is sectional drawing of a hydrodynamic bearing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Shaft part 3 Rotating member 4 Stator coil 5 Rotor magnet 6 Motor bracket 7 Housing 7a Thrust bearing surface 7d Seal surface 8 Bearing sleeve 9 Hub part 10 Flange part 11 Lid member 13 Die 13a Molding surface 18 Rod 18a Molding Surface 21 Dynamic pressure bearing device 22 Shaft portion 23 Rotating member 24 Stator coil 25 Rotor magnet 26 Motor bracket 27 Housing 27c Thrust bearing surface 27e Seal surface 28 Bearing sleeve 29 Hub portion 30 Locking members R1, R2, R11, R12 Radial bearing portion T1, T2, T11 Thrust bearing

Claims (9)

A cylindrical forged product, comprising a thrust bearing surface that forms a thrust bearing gap between the rotating member to be supported,
A housing for a hydrodynamic bearing device, wherein a perpendicular angle of a thrust bearing surface with respect to an inner peripheral surface or an outer peripheral surface is 20 μm or less. A cylindrical forged product, comprising a thrust bearing surface that forms a thrust bearing gap between the rotating member to be supported and a seal surface that forms a seal space between the rotating member,
A housing for a hydrodynamic bearing device, wherein the coaxiality of the seal surface with respect to the inner peripheral surface or the outer peripheral surface is 20 μm or less. A cylindrical forged product, comprising a thrust bearing surface that forms a thrust bearing gap between the rotating member to be supported,
A housing for a hydrodynamic bearing device, wherein the coaxiality of the outer peripheral surface with respect to the inner peripheral surface is 20 μm or less.   The dynamic pressure bearing device housing according to claim 1, wherein a dynamic pressure generating portion is formed on a thrust bearing surface.   The housing for a hydrodynamic bearing device according to any one of claims 1 to 3, wherein the housing is opened at both ends in the axial direction, a thrust bearing surface is provided on one end side, and the other end side is sealed with a lid member.   A hydrodynamic bearing device comprising the hydrodynamic bearing device housing according to claim 1 and a rotating member.   A spindle motor of a disk device having the hydrodynamic bearing device according to claim 6. Manufactures a housing for a hydrodynamic bearing device that has a cylindrical shape and includes a thrust bearing surface that forms a thrust bearing gap with a rotating member to be supported, and a seal surface that forms a seal space between the rotating member. When doing
A method for manufacturing a housing for a hydrodynamic bearing device, comprising a step of forging an inner peripheral surface after the outer peripheral surface of the housing is forged.   The method for manufacturing a housing for a hydrodynamic bearing device according to claim 8, wherein the forging of the inner peripheral surface is performed by punching the housing material from the axial direction anti-thrust bearing surface side toward the thrust bearing surface side.

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