JP2006105183A - Method of manufacturing hydrodynamic pressure bearing, spindle motor and recording disk driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrodynamic pressure bearing enhancing right-angled accuracy between a radial bearing and a thrust bearing easily at a low cost. <P>SOLUTION: The hydrodynamic pressure bearing 10 is mainly composed of a rotor hub 14, a shaft 13, a sleeve 16 and a bearing housing 17. The shaft 13 is erected on one end side of the rotor hub 14. The sleeve 16 has an inner peripheral surface 16a facing a lower part outer peripheral surface 13c of the shaft 13. The bearing housing 17 fits the sleeve 16 therein. The inner peripheral surface 17a of the bearing housing 17 is formed with a projecting part 15 projected toward the outer peripheral surface 16b of the sleeve 16 and smoothly reduced in the projecting quantity toward both axial sides. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bearing, and more particularly to a fluid dynamic pressure bearing. Further, the present invention relates to a spindle motor using a fluid dynamic pressure bearing, a recording disk drive device, and a method of manufacturing a fluid dynamic pressure bearing.

2. Description of the Related Art Conventionally, fluid dynamic pressure bearings have been employed in small drive devices used for hard disks and the like for the purpose of speeding up and reducing vibration. A fluid dynamic pressure bearing is one in which a bearing fluid is filled between a shaft and a bearing member, and the shaft is supported in a non-contact state with the bearing member by dynamic pressure generated when the shaft and the bearing member rotate relative to each other. . Since such a fluid dynamic pressure bearing supports the shaft in a non-contact state, the vibration and noise are reduced as compared with a conventional ball bearing and the like, the rotation accuracy is improved, and the rotation speed can be increased.
Such a fluid dynamic pressure bearing is unitized for attachment to a member constituting the device. For example, a structure is known in which a sleeve is fitted into a cylindrical or cup-shaped member called a bearing housing, and is attached to a member constituting a device via the bearing housing (see, for example, Patent Document 1). ). More specifically, this fluid dynamic pressure bearing is a cylindrical shaft having a cylindrical shaft having a dynamic pressure generating groove formed on the outer peripheral surface, and an inner peripheral surface facing the outer peripheral surface of the shaft with a small radial gap. And a bearing housing having an inner peripheral surface that comes into contact with the outer peripheral surface of the sleeve and in which the sleeve is fitted and fixed. In this fluid dynamic pressure bearing, when the shaft, the sleeve, and the bearing housing rotate relative to each other, a dynamic pressure is generated in a small radial gap between the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve, thereby constituting a radial bearing.

Further, as a fluid dynamic pressure bearing including a cup-shaped bearing housing, a structure in which an axial end surface of the bearing housing is one surface of a thrust bearing surface is known. That is, in this structure, a shaft having a cylindrical outer peripheral surface, a cylindrical sleeve having an inner peripheral surface opposed to the outer peripheral surface of the shaft with a small radial gap, and an annular outer peripheral surface of the sleeve are included therein. And a cup-shaped bearing housing which is fitted inside the peripheral surface. Further, in this structure, a radial bearing is constituted by the outer peripheral surface of the shaft, the inner peripheral surface of the sleeve, and the dynamic pressure generating fluid held in the minute radial gap therebetween, and is fixed to the axial end surface of the bearing housing and the shaft. A thrust bearing is constituted by the axially flat surface of the shaft base and the dynamic pressure generating fluid held in the minute axial gap therebetween.
In the fluid dynamic bearing having such a configuration, in order to obtain high rotational accuracy, it is required to improve the right-angle accuracy between the radial bearing and the thrust bearing.
JP 2000-175399 A

In order to meet the above requirements, it is conceivable to improve the component accuracy of the sleeve and the bearing housing. That is, it is conceivable to improve the processing accuracy of the outer peripheral surface of the sleeve and the processing accuracy of the inner peripheral surface and the axial end surface of the bearing housing. However, since there is a demand for cost reduction, it is difficult to employ such processing that improves the accuracy of parts.
Therefore, an object of the present invention is to provide a fluid dynamic pressure bearing with improved accuracy in the right angle between the radial bearing and the thrust bearing at a simpler and lower cost. Another object of the present invention is to provide a spindle motor using a fluid dynamic pressure bearing, a recording disk drive device, and a method of manufacturing a fluid dynamic pressure bearing.

A fluid dynamic pressure bearing according to a first aspect includes a shaft base, a shaft, a sleeve, and a bearing housing. The shaft is erected on one end side of the shaft base and has a cylindrical outer peripheral surface. The sleeve has an inner peripheral surface that opposes the outer peripheral surface of the shaft with a small radial gap. The bearing housing has a sleeve fitted therein. An axial end surface is formed at the other axial end of the bearing housing. The axial end surface is opposed to a flat surface formed on one axial end side of the shaft base through an axial minute gap. A radial bearing is constituted by the outer peripheral surface of the shaft, the inner peripheral surface of the sleeve, and the dynamic pressure generating fluid held in the minute radial gap therebetween. A thrust bearing is constituted by the flat surface of the shaft base, the axial end surface of the bearing housing, and the dynamic pressure generating fluid held in the minute axial gap therebetween. Either one of the outer peripheral surface of the sleeve or the inner peripheral surface of the bearing housing is formed with a protruding portion that protrudes toward the other and whose protruding amount smoothly decreases toward both axial sides.
Here, the bearing housing is, for example, a member for attaching a sleeve to a rotating member or a stationary member of a device including a fluid dynamic pressure bearing. In addition, a protruding portion that protrudes toward the other is formed on either the outer peripheral surface of the sleeve or the inner peripheral surface of the bearing housing. Thereby, the outer peripheral surface of the sleeve is formed in a substantially bowl shape, for example, and the inner peripheral surface of the bearing housing is formed in a substantially drum shape, for example.

In the fluid dynamic pressure bearing of the present invention, the outer peripheral surface of the sleeve and the inner peripheral surface of the bearing housing are in contact with each other at the protruding portion. The protrusion is formed on either the outer peripheral surface of the sleeve or the inner peripheral surface of the bearing housing, protrudes toward the other, and the amount of protrusion smoothly decreases toward both axial sides. For this reason, the sleeve and the bearing housing are swung with the protrusions in contact with each other, and the right angle accuracy between the inner peripheral surface of the sleeve constituting the radial bearing and the axial end surface of the bearing housing constituting the thrust bearing is adjusted. It becomes possible to do. That is, it is possible to provide a fluid dynamic pressure bearing in which the accuracy of the right angle between the radial bearing and the thrust bearing is improved without increasing the processing accuracy of the outer peripheral surface of the sleeve and the inner peripheral surface of the bearing housing.
A fluid dynamic pressure bearing according to a second aspect is the fluid dynamic pressure bearing according to the first aspect, wherein the projecting portion extends in the circumferential direction on either the outer peripheral surface of the sleeve or the inner peripheral surface of the bearing housing. It is formed continuously.
In the fluid dynamic pressure bearing of the present invention, a portion having a large outer diameter is formed at one axial position on the outer peripheral surface of the sleeve, or a portion having a small inner diameter is formed at one axial position on the inner peripheral surface of the bearing housing. Is done.
A fluid dynamic pressure bearing according to a third aspect is the fluid dynamic pressure bearing according to the first or second aspect, wherein the bearing housing is formed by pressing.

A feature of press working is that it is difficult to improve machining accuracy at a low cost. For this reason, in the conventional fluid dynamic pressure bearing, it is difficult to obtain a high right-angle accuracy between the inner peripheral surface of the sleeve and the end surface in the axial direction of the bearing housing while using press working for the bearing housing.
In the fluid dynamic pressure bearing of the present invention, high perpendicular accuracy can be obtained between the inner peripheral surface of the sleeve and the axial end surface of the bearing housing without depending on the accuracy of the press working. For this reason, it is possible to provide a fluid dynamic pressure bearing with higher accuracy in the right angle between the radial bearing and the thrust bearing at a lower cost.
A fluid dynamic pressure bearing according to a fourth aspect is the fluid dynamic pressure bearing according to the first or second aspect, wherein the bearing housing is formed of a resin.
The processing accuracy of the member formed of resin is easily affected by the accuracy of the mold, and it is difficult to obtain high processing accuracy.
In the fluid dynamic pressure bearing of the present invention, high perpendicular accuracy can be obtained between the inner peripheral surface of the sleeve and the axial end surface of the bearing housing without depending on the processing accuracy of the bearing housing formed of resin. For this reason, it is possible to provide a fluid dynamic pressure bearing with higher accuracy in the right angle between the radial bearing and the thrust bearing at a lower cost.

A fluid dynamic pressure bearing according to a fifth aspect is the fluid dynamic pressure bearing according to any one of the first to fourth aspects, wherein the sleeve is formed of a sintered metal.
When the sleeve is formed by sintering metal powder, the sleeve is porous and lubricating oil can be held in the sleeve, which is suitable for a bearing member. On the other hand, since it is difficult to manage dimensions, a dimension matching process called sizing is required.
In the fluid dynamic pressure bearing of the present invention, for example, even when a protrusion is formed on the outer peripheral surface of the sleeve, it is possible to process the protrusion in the sizing step. For this reason, it becomes possible to process a protrusion part, without the fall of workability | operativity, a raise of cost, etc.
A fluid dynamic pressure bearing according to a sixth aspect is the fluid dynamic pressure bearing according to any one of the first to fifth aspects, wherein the sleeve and the bearing housing include an outer peripheral surface of the sleeve and an inner peripheral surface of the bearing housing. It is fixed by filling the radial gap formed by the adhesive with an adhesive.
A radial gap formed by the outer peripheral surface of the sleeve and the inner peripheral surface of the bearing housing is formed so as to expand from the protruding portion toward both axial ends.
In the fluid dynamic pressure bearing of the present invention, since the adhesive is filled in the radial gap that expands toward both ends in the axial direction, a sufficient amount of adhesive can be held in the radial gap. This makes it possible to increase the fastening strength due to the adhesion between the sleeve and the bearing housing.

A fluid dynamic pressure bearing according to a seventh aspect is the fluid dynamic pressure bearing according to any one of the first to sixth aspects, wherein the flat surface of the shaft base is orthogonal to the shaft.
Here, the shaft base is, for example, a rotor hub that constitutes a rotating member of a spindle motor on which a fluid dynamic pressure bearing is mounted.
In the fluid dynamic pressure bearing of the present invention, a radial bearing is formed between the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve, and a thrust bearing is formed between the axial end surface of the bearing housing and the flat surface of the shaft base. The The right angle accuracy between the inner peripheral surface of the sleeve constituting the radial bearing and the axial end surface of the bearing housing constituting the thrust bearing can be adjusted by the action of the protruding portion. That is, the right angle accuracy between the radial bearing and the thrust bearing can be adjusted.
A spindle motor according to an eighth aspect is disposed to face the rotor magnet, the fluid dynamic pressure bearing according to any one of the first to seventh aspects, a rotor magnet that rotates integrally with either the shaft or the sleeve, and the rotor magnet. And a stator.
In the spindle motor of the present invention, it is possible to obtain the same effect as that of the fluid dynamic pressure bearing according to any one of claims 1 to 7, and the right angle accuracy between the radial bearing and the thrust bearing can be achieved more simply and at low cost. It is possible to provide a spindle motor including an enhanced fluid dynamic pressure bearing.

The recording disk device according to claim 9 is a housing and a spindle motor fixed to the housing, and rotates a disk-shaped recording medium on which information can be recorded. And an information access means for writing or reading information at the position.
In the recording disk device of the present invention, it is possible to obtain the same effect as that of the spindle motor according to claim 8, and a fluid dynamic pressure bearing in which the right angle accuracy between the radial bearing and the thrust bearing is improved more easily and at a lower cost. It is possible to provide a recording disk device comprising
The method of manufacturing a fluid dynamic pressure bearing according to claim 10 includes a shaft having a cylindrical outer peripheral surface, a sleeve having an inner peripheral surface opposed to the outer peripheral surface of the shaft with a small radial gap, and an inner sleeve. A fluid dynamic pressure bearing manufacturing method including a bearing housing to be fitted, which includes a fitting step, an adhesive application step, and a right angle accuracy adjustment step. The fitting step is formed on either the outer peripheral surface of the sleeve or the inner peripheral surface of the bearing housing, and protrudes toward the other, and the protruding portion in which the protruding amount decreases smoothly toward both sides in the axial direction, Fit in contact with the other. In the adhesive application step, an adhesive is applied to at least one of the outer peripheral surface of the sleeve and the inner peripheral surface of the bearing housing. In the right angle accuracy adjustment step, the right angle accuracy between the inner peripheral surface of the sleeve and the axial end surface of the bearing housing is adjusted.

With the manufacturing method of the present invention, it is possible to adjust the right angle accuracy between the inner peripheral surface of the sleeve and the axial end surface of the bearing housing not by improving the processing accuracy of the members constituting the fluid dynamic pressure bearing but by improving the structure. It becomes. For this reason, it becomes possible to manufacture a fluid dynamic pressure bearing with improved right-angle accuracy between the radial bearing and the thrust bearing at a simpler and lower cost.
The fluid dynamic pressure bearing manufacturing method according to claim 11 is the fluid dynamic pressure bearing manufacturing method according to claim 10, wherein the right angle accuracy adjusting step includes the inner peripheral surface of the sleeve and the axial end surface of the bearing housing. And adjusting the right-angle accuracy with a jig, and curing the adhesive to fix the sleeve and the bearing housing.
With the manufacturing method of the present invention, it is possible to increase the right angle accuracy of the fluid dynamic pressure bearing by increasing the accuracy of the jig, not by improving the processing accuracy of the member. For this reason, it becomes possible to manufacture a fluid dynamic pressure bearing with improved right-angle accuracy between the radial bearing and the thrust bearing at a simpler and lower cost. Furthermore, since the right angle accuracy is adjusted by the jig, it is possible to suppress the variation in the right angle accuracy in the manufactured fluid dynamic pressure bearing.

  According to the present invention, it is possible to provide a fluid dynamic pressure bearing in which the accuracy of the right angle between the radial bearing and the thrust bearing is improved more simply and at low cost. Furthermore, according to another aspect of the present invention, it is possible to provide a spindle motor using a fluid dynamic pressure bearing, a recording disk drive device, and a method of manufacturing a fluid dynamic pressure bearing.

[1] Configuration of Fluid Dynamic Pressure Bearing <1> Overall Configuration A fluid dynamic pressure bearing 10 as an embodiment of the present invention will be described with reference to FIG. In the description using the drawings, the vertical direction of the drawing is defined as the vertical direction of the axis for convenience, but this does not limit the actual mounting state.
A fluid dynamic pressure bearing 10 shown in FIG. 1 has a bearing housing 17 fixed to a hub 12 provided in a housing 11 of the device, a sleeve 16 fitted in the bearing housing 17, and is rotatable with respect to the sleeve 16. It is mainly composed of a supported shaft 13. Here, the device is, for example, a hard disk device including a spindle motor for driving a recording disk such as a hard disk.
The shaft 13 is a substantially cylindrical member having an upper portion 13b having a small diameter with respect to the lower portion 13a. The shaft 13 is erected downward in the axial direction in a center hole 14a provided at the rotation center of the rotor hub 14 of the spindle motor. More specifically, the flat surface 14b of the rotor hub 14 described later and the axis of the shaft 13 are erected so as to be orthogonal to each other.
The sleeve 16 is a substantially cylindrical member that includes an inner peripheral surface 16 a that faces the cylindrical lower outer peripheral surface 13 c of the shaft 13. The sleeve 16 rotatably supports the shaft 13 by causing the annular inner peripheral surface 16 a to face the lower outer peripheral surface 13 c of the shaft 13 via the radial minute gap 18. Further, the sleeve 16 is fitted and bonded to the inside of the bearing housing 17, and is fixed in a state where the cylindrical outer peripheral surface 16 b and the inner peripheral surface 17 a of the bearing housing 17 are in contact with each other. At this time, the sleeve 16 and the bearing housing 17 are fixed so that the axial position of the annular axial upper end surface 16c and the axial position of the annular surface 21c (described later) of the bearing housing 17 are substantially matched.

The bearing housing 17 is a cup-shaped member, and includes a side portion 19 having an inner peripheral surface 17 a and a disk-shaped bottom portion 20 that is continuous in the radial direction from the lower end of the side portion 19.
A lower outer peripheral surface 19 a of the side portion 19 is formed in a cylindrical shape extending in the axial direction, and is fixed to the hub 12 of the housing 11.
An edge portion 21 having an upper outer peripheral surface 21a having a diameter larger than that of the lower outer peripheral surface 19a is formed on the upper portion of the side portion 19. The upper outer peripheral surface 21a is formed by an inclined surface whose diameter increases toward the upper side in the axial direction, and the lower end thereof is still larger in diameter than the lower outer peripheral surface 19a. Thus, an annular lower end surface 21b extending in the radial direction is formed at the lower end of the edge portion 21 from the lower end edge of the upper outer peripheral surface 21a to the upper end edge of the lower outer peripheral surface 19a.
Further, the annular surface 21 c facing the upper side in the axial direction of the edge portion 21 is opposed to the annular flat surface 14 b of the rotor hub 14 via the minute axial gap 26. Here, the flat surface 14 b is an annular surface that extends in the radial direction from the lower edge of the center hole 14 a of the rotor hub 14 to the annular protrusion 23. Here, the annular protrusion 23 is an annular protrusion that is formed concentrically with the center hole 14 a in the rotor hub 14 and extends downward in the axial direction.
A ring-shaped retaining member 25 is attached to a step portion 23 b formed at the lower portion of the annular protrusion 23. The ring-shaped retainer 25 has the inner peripheral side of the annular axial upper end face opposed to the lower end face 21b of the bearing housing 17, and restricts the movement of the rotor hub 14 and the shaft 13 upward in the axial direction.

On the inner peripheral surface 17a of the bearing housing 17, there are formed projecting portions 15 that project toward the sleeve 16 and whose projecting amount decreases smoothly toward both axial sides. That is, the inner peripheral surface 17a is configured by a convex curved surface in which a cross section including the axis is convex inward in the radial direction. Furthermore, in other words, the inner peripheral surface 17a is formed in a substantially drum shape in which the diameters of the upper end portion and the lower end portion are larger than the diameter of the central portion, and the diameters thereof continuously change in the axial direction.
The inner peripheral surface 17 a is formed so that the diameter of the central portion having the minimum diameter is substantially the same as the diameter of the outer peripheral surface 16 b of the sleeve 16. As a result, when the bearing housing 17 is fitted to the sleeve 16, the respective axes can be substantially matched (coaxiality can be obtained).
The upper end portion and the lower end portion of the inner peripheral surface 17a have a gap between them and the outer peripheral surface 16b of the sleeve 16, and this gap is filled with an adhesive 24. The sleeve 16 and the bearing housing 17 are fixed by the adhesive 24.
<2> Dynamic Pressure Generating Mechanism The fluid dynamic pressure bearing 10 includes a radial bearing portion 35 and a thrust bearing portion 36 as dynamic pressure generating portions. Lubricating oil 38 is filled in the gap formed by the opposing surfaces in each bearing portion and the communication holes 27 formed to communicate with the upper and lower sides in the axial direction of the sleeve 16 at several locations on the outer peripheral surface 16b of the sleeve 16. (There are no parts blocked by air.) The lubricating oil 38 forms an interface and communicates with the outside air only by the surface tension seal portion 39 formed between the inner peripheral surface 23 a of the annular protrusion 23 and the upper outer peripheral surface 21 a of the bearing housing 17. Thereby, in the fluid dynamic pressure bearing 10, what is called a full-fill structure is implement | achieved.

In this embodiment, the full-fill structure is realized. However, the present invention can be applied even to a structure in which the lower end of the bearing housing 17 is opened and an interface is formed vertically. Furthermore, the present invention can also be applied to a dynamic pressure bearing (partial fill structure) having a structure in which the lubricating oil 38 is held only in the bearing portions (radial bearing portion 35 and thrust bearing portion 36).
Hereinafter, the structure of each bearing part will be described. In FIG. 1, each dynamic pressure generating groove, which will be described later, is shown on the cross section, but it is actually formed on the surface of each member.
(1) Radial bearing part The radial bearing part 35 is comprised by the inner peripheral surface 16a of the sleeve 16, the lower outer peripheral surface 13c of the shaft 13 facing the inner peripheral surface 16a, and the lubricating oil 38 between them.
On the inner peripheral surface 16 a of the sleeve 16, herringbone-shaped radial dynamic pressure generating grooves 41 for generating dynamic pressure in the lubricating oil 38 as the shaft 13 rotates are formed in two axial directions. Here, the radial dynamic pressure generating grooves 41 are a plurality of grooves arranged in the rotation direction, and each groove is formed by connecting a pair of spiral grooves inclined in directions opposite to the rotation direction. This is a letter-shaped groove.

In the radial bearing portion 35, the radial dynamic pressure generating groove 41 is formed in a balanced shape, and the fluid dynamic pressure in the radial bearing portion 35 is connected to a pair of spiral grooves that are inclined in directions opposite to the rotational direction. In the department.
In order to prevent the generation of negative pressure in the bearing, the radial dynamic pressure generating groove 41 on the upper side in the axial direction among the radial dynamic pressure generating grooves 41 formed at two locations in the axial direction is located on the lower side in the axial direction. It may be a herringbone having a shape in which the lubricating oil 38 flows.
The radial dynamic pressure generating groove 41 may be formed on the lower outer peripheral surface 13 c of the shaft 13.
(2) Thrust bearing portion The thrust bearing portion 36 is constituted by the annular surface 21c of the bearing housing 17 and the axial upper end surface 16c of the sleeve 16, the flat surface 14b of the rotor hub 14, and the lubricating oil 38 therebetween.
A spiral thrust dynamic pressure generating groove 43 for generating dynamic pressure in the lubricating oil 38 as the rotor hub 14 rotates is formed on the upper outer peripheral surface 21 a of the bearing housing 17. It is supported upward in the axial direction.

The spiral thrust dynamic pressure generating groove 43 is formed so that the lubricating oil 38 of the thrust bearing portion 36 flows inward in the radial direction. Thereby, generation | occurrence | production of the negative pressure in a bearing is prevented.
The thrust dynamic pressure generating groove 43 may have an unbalanced herringbone shape formed so that the lubricating oil 38 flows radially inward.
The thrust dynamic pressure generating groove 43 may be formed on the flat surface 14b.
(3) Surface tension seal portion The surface tension seal portion 39 is a structure for preventing leakage of the lubricating oil 38 from the thrust bearing portion 36, and the inner peripheral surface 23 a of the annular protrusion 23 and the upper outer periphery of the bearing housing 17. It is formed between the surface 21a. In the surface tension seal portion 39, the movement of the lubricating oil 38 to the outside of the fluid dynamic pressure bearing 10 is suppressed by the balance between the surface tension of the lubricating oil 38 held in the fluid dynamic pressure bearing 10 and the air pressure of the outside air. Is done. In addition, contact between the lubricating oil 38 and the outside air can be minimized, and evaporation of the lubricating oil 38 can be suppressed.
[2] Manufacturing Method With reference to FIG. 1 further, a manufacturing method of the fluid dynamic bearing 10 will be described.

In the first step, each member constituting the fluid dynamic pressure bearing 10 is formed.
The sleeve 16 is a sintered oil-containing porous body formed by sintering metal powder. On the inner peripheral surface 16a of the sleeve 16, a radial dynamic pressure generating groove 41 is press-molded. The shaft 13 is a cut metal product obtained by surface treatment of stainless steel. The shaft 13 and the sleeve 16 may be made of ceramic.
The general shape of the bearing housing 17 is formed by pressing a metal plate material. At the same time, a thrust dynamic pressure generating groove 43 is press-formed on the annular surface 21 c of the bearing housing 17. The bearing housing 17 may be formed by cutting a metal or by injection molding a resin.
In the second step, the sleeve 16 and the bearing housing 17 are assembled. At this time, the outer peripheral surface 16 b of the sleeve 16 and the protruding portion 15 of the inner peripheral surface 17 a of the bearing housing 17 are fitted together.
In the third step, an adhesive is filled in the gap between the outer peripheral surface 16 b of the sleeve 16 and the inner peripheral surface 17 a of the bearing housing 17.
In the fourth step, the perpendicularity between the inner peripheral surface 16a of the sleeve 16 and the annular surface 21c of the bearing housing 17 is adjusted using a jig before the adhesive is cured. The inner peripheral surface 17 a of the bearing housing 17 is formed so as to project the axial center portion radially inward, and the bearing housing 17 can be swung with respect to the sleeve 16. As a result, the perpendicularity between the inner peripheral surface 16 a of the sleeve 16 and the annular surface 21 c of the bearing housing 17 can be adjusted.

In the fifth step, each member constituting the fluid dynamic pressure bearing 10 is assembled. First, the upper portion 13 b of the shaft 13 is fixed to the center hole 14 a of the rotor hub 14. Further, the sleeve 16 and the bearing housing 17 assembled in the second to fourth steps are attached with the inner peripheral surface 16 a of the sleeve 16 facing the lower outer peripheral surface 13 c of the shaft 13. Furthermore, a ring-shaped retaining member 25 is attached to the step portion 23b. At this time, lubricating oil 38 is injected into the radial micro gap 18, the axial micro gap 26, and the surface tension seal portion 39.
Note that the order of the second to fourth steps is not limited to the order described above. For example, after the adhesive is applied to the outer peripheral surface 16b of the sleeve 16 and the inner peripheral surface 17a of the bearing housing 17 (third step), the sleeve 16 and the bearing housing 17 may be assembled (second step). . Further, the fourth step may be performed before the adhesive is cured, and after the angle adjustment (fourth step), the adhesive is placed in the gap between the outer peripheral surface 16b of the sleeve 16 and the inner peripheral surface 17a of the bearing housing 17. It may be filled.
[3] Spindle Motor and Hard Disk Device <1> Configuration of Spindle Motor FIG. 2 is a schematic vertical sectional view of a spindle motor 52 including the fluid dynamic pressure bearing 10.

The spindle motor 52 mainly includes the fluid dynamic pressure bearing 10, a rotor magnet 62 that is fixed to the shaft 13 via the rotor hub 14 and rotates integrally, and a stator 63 that is disposed to face the rotor magnet 62. Has been.
Since the configuration of the fluid dynamic pressure bearing 10 has been described with reference to FIG. 1, description thereof is omitted here. The fluid dynamic pressure bearing 10 is attached with a lower outer peripheral surface 19 a of the bearing housing 17 fixed to a hole 12 a formed in the hub 12 of the housing 11.
The rotor hub 14 is a cup-shaped member that fixes the upper portion 13b of the shaft 13 and on which the recording disk is placed on the outer peripheral portion. The rotor hub 14 has a center hole 14a having a diameter substantially the same as the diameter of the upper portion 13b of the shaft 13 at the center thereof. The shaft 13 is fixed to the rotor hub 14 by fitting the upper portion 13b of the shaft 13 into the center hole 14a.
The rotor hub 14 is mainly composed of an annular portion 66 extending radially outward from the center hole 14a and an outer peripheral side portion 67 having an inner peripheral surface 67a extending axially downward from the outer peripheral edge of the annular portion 66. ing. An annular protrusion 23 that is an annular protrusion that is formed concentrically with the center hole 14a and that extends downward in the axial direction is formed at the intermediate portion in the radial direction of the annular portion 66. A rotor magnet 62 is fixed to the inner peripheral surface 67a by an adhesive means. A recording disk is fitted to the outer peripheral surface of the outer peripheral side portion 67.

An annular protrusion 30 is formed on the outer side of the hub 12 of the housing 11 in the radial direction. The annular protrusion 30 is an annular protrusion that is concentric with the hole 12a and extends upward in the axial direction. A stator 63 is fixed to the outer peripheral portion of the annular protrusion 30. The stator 63 includes a stator core and a coil wound around the stator core. Further, a thrust yoke 64 is fixed to the housing 11 at a radial position corresponding to the rotor magnet 62.
<2> Operation of Spindle Motor When the stator 63 is energized, electromagnetic interaction between the stator 63 and the rotor magnet 62 occurs. Thus, the rotor magnet 62, the rotor hub 14 and the shaft 13 (hereinafter referred to as a rotating member) are integrally rotated with respect to the sleeve 16, the bearing housing 17, the housing 11 and the stator 63 (hereinafter referred to as a stationary member). At this time, in the thrust bearing portion 36, the lubricating oil 38 in the gap between the annular surface 21 c and the axial upper end surface 16 c and the flat surface 14 b generates a thrust load support pressure by the action of the thrust dynamic pressure generating groove 43. . In the radial bearing portion 35, the lubricating oil 38 in the gap between the inner peripheral surface 16 a and the lower outer peripheral surface 13 c generates a radial load support pressure by the action of the radial dynamic pressure generating groove 41.
Here, the magnetic center of the rotor magnet 62 and the magnetic center of the stator 63 are arranged so as to be different from each other in the axial direction, and the magnetic attraction force between the thrust yoke 64 attached to the housing 11 and the rotor magnet 62. Thus, it is possible to apply a biasing force that supports the rotor hub 14 and the shaft 13 downward. This biasing force and the thrust load support pressure of the thrust bearing portion 36 are balanced and balanced.

<3> Hard Disk Device A schematic longitudinal sectional view of a hard disk device 50 including a spindle motor 52 is shown using FIG.
The hard disk device 50 is a small and thin hard disk device for rotating a recording disk.
Each part of the hard disk device 50 is contained in the housing 11, and mainly includes a spindle motor 52, a recording disk 53, and a magnetic head moving mechanism 57. The inside of the housing 11 forms a good environment with extremely little dust.
The recording disk 53 is a disk-shaped member that records information by magnetism.
The magnetic head moving mechanism 57 is a mechanism for reading and writing information with respect to the recording disk 53, and includes a magnetic head 56, an arm 55, and an actuator unit 54.
The magnetic head 56 is provided in the vicinity of the recording disk 53 by being provided at one end of the arm 55, and reads / writes the recording disk 53. The arm 55 is a member that supports the magnetic head 56. The actuator unit 54 supports the other end of the arm 55 and moves the arm 55. The actuator unit 54 can swing the arm 55 to move the magnetic head 56 to a required position on the recording disk 53.

In the hard disk device 50, the recording disk 53 rotates as the spindle motor 52 rotates. The actuator unit 54 is driven to swing the arm 55, and the magnetic head 56 is moved to a required position on the recording disk 53. As a result, the recording disk 53 is read and written.
[4] Effect <1>
In the fluid dynamic pressure bearing 10 of the present invention, the outer peripheral surface 16 b of the sleeve 16 and the inner peripheral surface 17 a of the bearing housing 17 are in contact with each other at the protruding portion 15. The protruding portion 15 is formed on the inner peripheral surface 17a of the bearing housing 17 and protrudes toward the outer peripheral surface 16b of the sleeve 16, and the amount of protrusion smoothly decreases toward both axial sides. For this reason, the sleeve 16 and the bearing housing 17 are swung in a state where the projecting portion 15 is in contact with each other, and the inner peripheral surface 16 a of the sleeve 16 constituting the radial bearing portion 35 and the bearing housing 17 constituting the thrust bearing portion 36. It becomes possible to adjust the right angle accuracy with the annular surface 21c. That is, the fluid dynamic pressure bearing 10 is provided in which the perpendicular accuracy between the radial bearing portion 35 and the thrust bearing portion 36 is improved without increasing the processing accuracy of the outer peripheral surface 16b of the sleeve 16 and the inner peripheral surface 17a of the bearing housing 17. It becomes possible.

Further, since there is no need to increase the processing accuracy of the inner peripheral surface 17a, low-cost processing such as press processing can be used for forming the bearing housing 17, and the cost of the fluid dynamic pressure bearing can be reduced.
<2>
In the fluid dynamic bearing 10 of the present invention, the sleeve 16 and the bearing housing 17 are fixed with an adhesive. Here, since the sleeve 16 and the bearing housing 17 have “a portion having a narrow clearance” with which the respective opposed surfaces abut, it is possible to obtain coaxial accuracy. Moreover, since it has “a wide clearance portion” sandwiched between the opposing surfaces at both ends in the axial direction, and this portion is filled with the adhesive, it is possible to obtain sufficient adhesive strength.
<3>
In the fluid dynamic pressure bearing 10 of the present invention, the thrust dynamic pressure generating groove 43 can be press-molded at the same time when the general shape of the bearing housing 17 is press-molded. That is, when manufacturing the bearing housing 17 of the present invention, no special process is required as compared with the case of manufacturing a conventional bearing housing. For this reason, it becomes possible to obtain a fluid dynamic pressure bearing with higher rotational accuracy at the same cost as the conventional one.

Further, since the bearing housing 17 is manufactured using metal press molding or resin injection molding, it is possible to maintain high productivity while keeping the cost of the fluid dynamic bearing 10 low.
<4>
In the fluid dynamic pressure bearing shown in Patent Document 1 described in the background art, a portion where the sleeve and the bearing housing abut is formed in a cylindrical shape extending in the axial direction. In this prior art, it is difficult to adjust the axis of the sleeve and the bearing housing.
On the other hand, in the fluid dynamic pressure bearing 10 of the present invention, the portion where the sleeve 16 and the bearing housing 17 come into contact is small, and the sleeve 16 and the bearing housing 17 can swing relative to each other so that their axes coincide with each other. Adjustable.
Moreover, in the fluid dynamic pressure bearing shown in Patent Document 1, the sleeve is press-fitted and fixed to the bearing housing. In the case of press fitting, the sleeve is likely to be deformed, and it is difficult to adjust the position of the sleeve and the bearing housing. Further, in order to improve the rotation accuracy of the bearing, it is necessary to improve the processing accuracy (perpendicularity, roundness, coaxiality, surface accuracy, etc.) of each member.
On the other hand, in the fluid dynamic pressure bearing 10 of the present invention, the position of the sleeve 16 and the bearing housing 17 can be adjusted, and the rotational accuracy of the bearing can be maintained even if low-cost processing is used.

<5>
Since the spindle motor 52 and the hard disk device 50 of the present invention include the fluid dynamic pressure bearing 10, it is possible to obtain the same effects as the effects of the fluid dynamic pressure bearing 10 described above. For example, it is possible to obtain a spindle motor and a hard disk device that achieve both high rotational accuracy and cost reduction.
[5] Modifications The present invention is not limited to such embodiments, and various modifications or corrections can be made without departing from the scope of the present invention.
<1>
In the above embodiment, the inner peripheral surface 17a of the bearing housing 17 has been described as having the protruding portion 15 protruding radially inward.
Here, the protrusion 15 may be on the sleeve side. This will be described with reference to FIG.
FIG. 4 is a schematic longitudinal sectional view of a sleeve 76 and a bearing housing 77 as a modification. In the figure, the alternate long and short dash line indicates the axis of the fluid dynamic pressure bearing.

The sleeve 76 is a hollow member disposed with the annular inner peripheral surface 76a facing the lower outer peripheral surface 13c of the shaft 13 (see FIG. 1). The outer peripheral surface 76b of the sleeve 76 is formed of a convex curved surface in which a cross section including the axis is convex outward in the radial direction. In other words, the outer peripheral surface 76b of the sleeve 76 is formed in a substantially bowl shape in which the diameters of the upper end portion and the lower end portion are smaller than the diameter of the central portion, and the diameters continuously change in the axial direction. Furthermore, the outer peripheral surface 76b is more preferably a part of a spherical surface having a center on the axis.
The bearing housing 77 is a member having substantially the same outer shape as the bearing housing 17 shown in FIG. The bearing housing 77 is different from the bearing housing 17 in the shape of the inner peripheral surface 77a. The inner peripheral surface 17a of the bearing housing 17 is formed by a convex curved surface that protrudes radially inward, but the inner peripheral surface 77a of the bearing housing 77 is formed in a cylindrical shape that extends in the axial direction. .
A radial bearing is configured by the inner peripheral surface 76a of the sleeve 76, the lower outer peripheral surface 13c of the shaft 13, and the lubricating oil held in the minute radial gap therebetween. A thrust bearing is constituted by the annular surface 77b formed at the upper end in the axial direction of the bearing housing 77, the flat surface 14b (see FIG. 1) of the rotor hub 14, and the lubricating oil held in the slight axial gap therebetween.

With such a configuration, the sleeve 76 and the bearing housing 77 can swing while the outer peripheral surface 76b of the sleeve 76 and the inner peripheral surface 77a of the bearing housing 77 are in contact with each other. For this reason, it is possible to adjust the right-angle accuracy between the inner peripheral surface 76a constituting the radial bearing and the annular surface 77b constituting the thrust bearing.
In this case, when the sleeve 76 is sintered and when the dynamic pressure generating groove is press-formed on the inner peripheral surface 76a, the outer peripheral surface 76b can be formed in a substantially bowl shape. For this reason, a special process is not required as compared with the case of manufacturing a conventional sleeve.
In addition, the modification of a sleeve and a bearing housing is not limited to this. For example, the structure which makes the opposing surface of both a sleeve and a bearing housing convex toward the other party is also considered. Alternatively, one opposing surface may be formed in a convex shape toward the other opposing surface, and a concave shape corresponding to the formed convex shape may be formed on the other.
In the above embodiment, the inner circumferential surface 17a of the bearing housing 17 has been described as being continuously formed in the circumferential direction, but may be formed at a plurality of locations (for example, three locations) in the circumferential direction. .
<2>
In the above embodiment, the configuration in which the shaft 13 is a rotating member of the spindle motor has been described.

Here, even when the shaft 13 is a stationary member of the spindle motor, the present invention can be appropriately modified and applied.
<3>
In the embodiment and the modification described above, the bearing housing 17 (see FIG. 1) or the sleeve 76 (see FIG. 4) has been described as having a protruding portion that protrudes radially inward or outward at the axially intermediate portion. .
Here, the position of the protruding portion in the axial direction may be a position that does not contribute to the shaft support of the radial bearing, or may be a position that contributes to the shaft support of the radial bearing.
For example, in FIG. 1, the axial position of the portion where the bearing housing 17 and the sleeve 16 abut may be the same as the axial position of the radial dynamic pressure generating groove 41, or the radial dynamic pressure generating groove 41. It may be different from the axial position.
<4>
In the said embodiment, the bearing housing 17 demonstrated that it was a cup-shaped member formed integrally.
Here, in the bearing housing 17, the bottom part 20 may be formed as a separate body. In this case, the bearing housing 17 has a structure in which a bottom portion 20 as a cover member (counter plate) is fixed to the lower end in the axial direction of the substantially cylindrical side portion 19.

<5>
Further, the invention described in the above embodiment can be applied to a fluid dynamic bearing having a structure disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-19755.
That is, in the fluid dynamic pressure bearing 10 shown in FIG. 1, a thrust flange extending radially outward is formed at the axial lower end of the shaft 13. The thrust flange extends radially outward from the lower end in the axial direction of the shaft 13 and is disposed in an axial gap between the lower end surface in the axial direction of the sleeve 16 and the upper side surface in the axial direction of the bottom portion 20. Thereby, the axial lower end surface of the thrust flange and the axial upper side surface of the bottom portion 20 face each other to form a thrust bearing.
The fluid dynamic pressure bearing having such a structure is similar in the structure of the fluid dynamic pressure bearing 10 and the radial bearing described in the above embodiment, but is different in the structure of the thrust bearing. However, by applying the present invention to the fluid dynamic bearing having such a structure, the right angle accuracy between the bearing housing 17 having the bottom 20 constituting the thrust bearing and the sleeve 16 constituting the radial bearing is improved. It becomes possible to make it.
The invention described in the above embodiment is applicable to a fluid dynamic bearing having a structure disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-262217.

That is, in the fluid dynamic pressure bearing 10 shown in FIG. 1, a thrust flange extending radially outward is formed at the axial lower end of the shaft 13. The thrust flange extends radially outward from the lower end in the axial direction of the shaft 13 and is disposed in an axial gap between the lower end surface in the axial direction of the sleeve 16 and the upper side surface in the axial direction of the bottom portion 20. Thereby, in addition to the thrust bearing portion 36, the axial lower end surface of the sleeve 16 and the axial upper end surface of the thrust flange face each other to form a thrust bearing.
The fluid dynamic pressure bearing having such a structure is similar in the structure of the fluid dynamic pressure bearing 10 and the radial bearing described in the above embodiment, but is different in the structure of the thrust bearing. However, by applying the present invention to the fluid dynamic bearing having such a structure, it is possible to improve the right angle accuracy between the bearing housing 17 constituting the thrust bearing and the sleeve 16 constituting the radial bearing. It becomes.

  INDUSTRIAL APPLICABILITY The present invention is useful as a fluid dynamic pressure bearing in which the right angle accuracy between a radial bearing and a thrust bearing is improved, a spindle motor equipped with the fluid dynamic pressure bearing, a recording disk drive device, and the like in a simpler and lower cost manner.

Schematic diagram of longitudinal section of fluid dynamic bearing 10 Schematic diagram of longitudinal section of spindle motor 52 Schematic diagram of longitudinal section of hard disk device 50 Schematic of longitudinal section of fluid dynamic pressure bearing as a modification

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fluid dynamic pressure bearing 11 Housing 12 Hub 13 Shaft 14 Rotor hub 15 Protrusion part 16 Sleeve 17 Bearing housing 18 Radial minute gap 19 Side part 20 Bottom part 21 Edge part 23 Ring protrusion part 24 Adhesive 25 Ring-shaped retaining part 26 Axial direction Minute clearance 27 Communication hole 30 Annular protrusion 35 Radial bearing portion 36 Thrust bearing portion 38 Lubricating oil 39 Surface tension seal portion 41 Radial dynamic pressure generating groove 43 Thrust dynamic pressure generating groove 50 Hard disk device 52 Spindle motor 53 Recording disk 54 Actuator Part 55 arm 56 magnetic head 57 magnetic head moving mechanism 62 rotor magnet 63 stator 64 thrust yoke 66 annular part 67 outer peripheral side part

Claims (11)

A shaft base;
A shaft erected on one end side of the shaft base and having a cylindrical outer peripheral surface;
A sleeve having an inner peripheral surface facing the outer peripheral surface of the shaft with a small radial gap;
A bearing housing in which the sleeve is fitted,
An axial end face is formed at the other axial end of the bearing housing,
The axial end surface is opposed to a flat surface formed on one axial end side of the shaft base through an axial small gap,
A radial bearing is configured by the outer peripheral surface of the shaft, the inner peripheral surface of the sleeve, and a dynamic pressure generating fluid held in the minute radial gap therebetween,
A thrust bearing is constituted by the flat surface of the shaft base, the axial end surface of the bearing housing, and a dynamic pressure generating fluid held in the minute axial gap therebetween,
Either one of the outer peripheral surface of the sleeve or the inner peripheral surface of the bearing housing is formed with a protruding portion that protrudes toward the other and whose protruding amount smoothly decreases toward both axial sides.
Fluid dynamic pressure bearing. The protrusion is formed continuously in the circumferential direction on either the outer peripheral surface of the sleeve or the inner peripheral surface of the bearing housing.
The fluid dynamic pressure bearing according to claim 1. The bearing housing is formed by pressing.
The fluid dynamic pressure bearing according to claim 1. The bearing housing is made of resin.
The fluid dynamic pressure bearing according to claim 1. The sleeve is made of sintered metal,
The fluid dynamic pressure bearing according to claim 1. The sleeve and the bearing housing are fixed by filling a radial gap formed by the outer peripheral surface of the sleeve and the inner peripheral surface of the bearing housing with an adhesive,
The fluid dynamic pressure bearing according to claim 1. The flat surface of the shaft base is orthogonal to the shaft;
The fluid dynamic pressure bearing according to claim 1. A fluid dynamic pressure bearing according to any one of claims 1 to 7,
A rotor magnet that rotates integrally with either the shaft or the sleeve;
A stator disposed opposite to the rotor magnet;
Spindle motor with A housing;
The spindle motor according to claim 7, wherein the spindle motor is fixed to the housing and rotates a disk-shaped recording medium capable of recording information.
Information access means for writing or reading information to a required position of the recording medium;
A recording disk drive comprising: A fluid dynamic pressure bearing comprising: a shaft having a cylindrical outer peripheral surface; a sleeve having an inner peripheral surface facing the outer peripheral surface of the shaft with a small radial gap; and a bearing housing in which the sleeve is fitted. A manufacturing method comprising:
A protruding portion formed on either the outer peripheral surface of the sleeve or the inner peripheral surface of the bearing housing and protruding toward the other and whose protruding amount decreases smoothly toward both axial sides contacts the other. A mating process for mating, and
An adhesive application step of applying an adhesive to at least one of the outer peripheral surface of the sleeve and the inner peripheral surface of the bearing housing;
A right angle accuracy adjusting step for adjusting a right angle accuracy between the inner peripheral surface of the sleeve and an axial end surface of the bearing housing;
A method of manufacturing a fluid dynamic pressure bearing. The right angle accuracy adjusting step includes a step of adjusting a right angle accuracy between the inner peripheral surface of the sleeve and the axial end surface of the bearing housing by using a jig, curing the adhesive, and the sleeve and the bearing housing. And fixing the
A method for manufacturing a fluid dynamic pressure bearing according to claim 10.

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