JP2003343547A - Fluid bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve reduction of the weight and costs. <P>SOLUTION: The housing 17 is formed by molding a metal material by making a bearing sleeve 18 comprising a sintered metal as an insert part, and is provided with a cylindrical side 17b, an annular seal 17a integrally extended from the upper end of the side 17b to the inner diameter side, and a bottom 17c continually integrated to the lower end of the side 17b. The inner peripheral face 17a1 of the seal 17a faces the outer peripheral face 12a1 of a shaft member 12 via a prescribed seal space. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic bearing device for supporting a shaft member in a radial direction in a non-contact manner with an oil film of lubricating oil generated in a bearing gap. This bearing device is an information device, for example, a magnetic disk device such as an HDD or FDD, a CD-RO
M, CD-R / RW, DVD-ROM / RAM, and other optical disk devices, MD, MO, and other magneto-optical disk devices, spindle motors, laser beam printer (LBP) polygon scanner motors, or electrical equipment such as axial flow. It is suitable for small motors such as fans.

[0002]

2. Description of the Related Art In addition to high rotation accuracy,
Higher speed, lower cost and lower noise are required.
One of the components that determines the required performance is a bearing that supports the spindle of the motor, and in recent years, as a bearing of this type, the use of a fluid bearing having characteristics excellent in the required performance has been studied, or It is actually used.

This type of hydrodynamic bearing includes a so-called dynamic pressure bearing having a dynamic pressure generating means for generating a dynamic pressure in the lubricating oil in the bearing gap, and a so-called true circular bearing (bearing surface) having no dynamic pressure generating means. Bearings that have a perfect circular shape).

For example, in a hydrodynamic bearing device incorporated in a spindle motor of a disk device such as an HDD or a polygon scanner motor of a laser beam printer (LBP), a radial bearing portion for supporting a shaft member in a non-contact manner so as to be rotatable in a radial direction, A thrust bearing portion that rotatably supports the shaft member in the thrust direction is provided, and as a radial bearing portion,
A dynamic pressure bearing having a groove (dynamic pressure groove) for generating dynamic pressure on the inner peripheral surface of the bearing sleeve or the outer peripheral surface of the shaft member is used. As the thrust bearing portion, for example, both end surfaces of the flange portion of the shaft member, or surfaces facing the end surface (end surface of the bearing sleeve,
A dynamic pressure bearing in which a dynamic pressure groove is provided in an end surface of a thrust member fixed to a housing) or a bearing (so-called pivot bearing) having a structure in which one end surface of a shaft member is supported in contact with a thrust plate or the like is used.

Usually, the bearing sleeve is fixed at a predetermined position on the inner circumference of the housing, and a seal member is arranged at the opening of the housing to prevent the lubricating oil injected into the inner space of the housing from leaking to the outside. Often set up.

[0006]

The fluid dynamic bearing device configured as described above is composed of parts such as a housing, a bearing sleeve, a shaft member, a thrust member (or a thrust plate), and a seal member, so that the performance of information equipment is further improved. Therefore, in order to ensure the high bearing performance required, the efforts are being made to improve the processing accuracy and assembly accuracy of each component. On the other hand, as the price of information equipment has become lower, demands for cost reduction of this type of hydrodynamic bearing device have become more and more strict.

In view of the above circumstances, Japanese Patent Laid-Open No. 11-2181
In No. 25, the bearing member and the bearing support frame are formed by aluminum die-cast insert molding, so that the bearing member can be fitted and fixed to the bearing support frame in a simple process to improve productivity. To reduce costs.

In the technique described in the above publication, in order to prevent the bearing holder (12) constituting the bearing support frame from falling off in the axial direction, an annular groove (13b) is formed on the outer peripheral surface side of the bearing sleeve (13). ) Is provided, the annular protrusion (12b) on the inner peripheral surface side of the bearing holder (12) formed by aluminum die-cast insert molding is connected to the annular groove (13) of the bearing holder (13).
The fixed state of both is strengthened by fitting the concave and convex in (b). However, the annular groove (13
In the case of b), it is necessary to separately form the outer peripheral surface of the bearing sleeve (12) by machining such as cutting, which increases the number of processing steps, which is one of the factors that hinder the cost reduction.

An object of the present invention is to provide a hydrodynamic bearing device that is even lower in cost.

[0010]

In order to solve the above problems, the present invention provides a housing, a bearing sleeve fixed to the inner circumference of the housing, a shaft member, an inner peripheral surface of the bearing sleeve and an outer circumference of the shaft member. In a hydrodynamic bearing device that is provided between the bearing surface and a radial bearing portion that supports the shaft member in the radial direction in a non-contact manner with an oil film of lubricating oil generated in the bearing gap, the bearing sleeve is formed of sintered metal, and Provided is a configuration in which a housing is formed by molding a metal material using a bearing sleeve as an insert part.

As the above metal material, for example, aluminum alloy, magnesium alloy, stainless steel, etc. can be used. Further, as the above-mentioned mold molding, a molding method such as die cast molding or injection molding can be adopted.
By molding the housing using the bearing sleeve as an insert part and molding the housing with a metal material, it is possible to omit the step of fixing the bearing sleeve to the housing and reduce the manufacturing cost. In particular, since the bearing sleeve is made of sintered metal, a part of the molding material (metal material in a molten or semi-molten state) is formed on the surface of the bearing sleeve (inside the porous structure of the sintered metal) during molding. From the site where pores are formed by opening on the surface), they penetrate into the internal pores and solidify. Then, the solidified portion in the internal pores firmly adheres the housing and the bearing sleeve to each other by a kind of anchor effect, so that a relative positional shift between them does not occur and a stable fixed state is obtained.

By using a magnesium alloy as the metal material for molding the housing, the weight of the hydrodynamic bearing device can be further reduced. Magnesium alloy is the metal having the smallest specific gravity among practical metals, and its specific gravity is about 1.8, which is about one-fourth that of iron and about two-thirds of the weight of aluminum alloy. Further, it has excellent thin-wall formability as compared with aluminum alloys and the like.

Further, the magnesium alloy has a good heat dissipation property, and the fluid bearing device of the present invention provided with the housing made of the magnesium alloy is particularly suitable for the rotation supporting portion of the spindle motor mounted in the information equipment. For example, in a personal computer, as the clock frequency of a CPU (central processing unit) is rapidly improving, heat is easily accumulated inside the personal computer, and the operating environment of a fluid dynamic bearing device incorporated in a disc drive device is also The severity is increasing. Further, as the speed of the disk drive device and the like increases, the internal heat generation amount of the bearing itself tends to increase. On the other hand, when heat is accumulated inside the hydrodynamic bearing device, deterioration of the lubricating oil is promoted, which is one of the causes of shortening the life of the bearing. By forming the housing of the hydrodynamic bearing device with a magnesium alloy having good heat dissipation, it is possible to prevent heat from being accumulated inside the hydrodynamic bearing device and prevent the bearing life from being shortened.

Further, the magnesium alloy has little deterioration in quality due to remelting and refining and is excellent in recyclability. Therefore, forming the housing of the hydrodynamic bearing device from a magnesium alloy is also preferable from the viewpoint of reducing the environmental load.

When injection molding a magnesium alloy or the like,
For example, the thixomolding method can be adopted. In the thixomolding method, magnesium alloy chips are heated in a cylinder to a semi-molten state, stirred by a screw, and made into a slurry form and injection-molded from a nozzle. The thixomolding method is a process that is friendly to the global environment because it can produce parts with high dimensional accuracy and does not require a flameproof gas such as SF ₆ gas.

In the above structure, the radial bearing portion may be a dynamic pressure bearing for generating a dynamic pressure in the lubricating oil in the bearing gap.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 1 shows an example of the configuration of a spindle motor for information equipment in which a fluid dynamic bearing device 1 according to this embodiment is incorporated. This spindle motor is used in a disk drive device such as an HDD, and includes a hydrodynamic bearing device 1 that rotatably supports a shaft member 2 in a non-contact manner, a disk hub 3 mounted on the shaft member 2, and a radial direction, for example. It is provided with a motor stator 4 and a motor rotor 5 which are opposed to each other via a gap. The stator 4 is attached to the outer circumference of the casing 6, and the rotor 5 is attached to the inner circumference of the disc hub 3. The housing 7 of the hydrodynamic bearing device 1 is mounted on the inner circumference of the casing 6. The disk hub 3 holds one or a plurality of disks D such as magnetic disks. When the stator 4 is energized, the exciting force between the stator 4 and the rotor 5 causes the rotor 5 to rotate, whereby the disk hub 3
And the shaft member 2 rotates integrally.

FIG. 2 shows a hydrodynamic bearing device (fluid dynamic pressure bearing device) 1. The hydrodynamic bearing device 1 is composed of a housing 7, a bearing sleeve 8, a shaft member 2, and a thrust member 10 as constituent parts.

A first radial bearing portion R is provided between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a of the shaft member 2.
The first radial bearing portion R2 and the first radial bearing portion R2 are axially separated from each other. Further, a first thrust bearing portion S1 is provided between the lower end surface 8c of the bearing sleeve 8 and the upper end surface 2b1 of the flange portion 2b of the shaft member 2, and the end surface 1 of the thrust member 10 is provided.
0a and the lower end surface 2b2 of the flange portion 2b, the second thrust bearing portion S2 is provided. For convenience of explanation, the description will proceed with the side of the thrust member 10 as the lower side and the side opposite to the thrust member 10 as the upper side.

The shaft member 2 is made of, for example, a metal material such as stainless steel, and has a shaft portion 2a and a flange portion 2b integrally or separately provided at the lower end of the shaft portion 2a.

The bearing sleeve 8 is made of, for example, a porous body made of a sintered metal, particularly a porous body of a sintered metal containing copper as a main component, and is formed in a cylindrical shape at a predetermined position on the inner peripheral surface 7c of the housing 7. It is arranged.

A bearing sleeve 8 made of this sintered metal
The inner peripheral surface 8a is provided with two upper and lower regions, which are the radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2, axially separated from each other. Bone-shaped dynamic pressure grooves are formed respectively.
The dynamic pressure groove may have a spiral shape, an axial groove shape, or the like.

On the lower end surface 8c of the bearing sleeve 8 which is the thrust bearing surface of the first thrust bearing portion S1, a dynamic pressure groove having, for example, a spiral shape is formed. As the shape of the dynamic pressure groove, a herringbone shape or a radial groove shape may be adopted.

The housing 7 is formed, for example, by molding (die casting or injection molding) a metal material such as a magnesium alloy using a bearing sleeve 8 made of a sintered metal as an insert part, and has a cylindrical side portion 7b. And the side part 7b
And an annular seal portion 7a integrally extending from the upper end to the inner diameter side. The inner peripheral surface 7a1 of the seal portion 7a has a shaft portion 2
It faces the outer peripheral surface 2a1 of a through a predetermined seal space. The inner peripheral surface 7c of the side portion 7b has a straight shape in the axial direction.

The housing 7 and the bearing sleeve 8 are fixed to each other by the above-mentioned molding without undergoing a separate fixing step. In particular, since the bearing sleeve 8 is made of sintered metal, the housing 7 and the bearing sleeve 8 are firmly brought into close contact with each other for the above-mentioned reason, and a stable fixed state between them can be obtained.

The thrust member 10 is formed in a disk shape, and is fixed to the lower end portion of the inner peripheral surface 7c of the housing 7 by appropriate means such as press-fitting / adhesion, laser beam welding, and high frequency pulse bonding. A herringbone-shaped dynamic pressure groove is formed on the end surface 10a of the thrust member 10, which is the thrust bearing surface of the second thrust bearing portion S2. The thrust member 10 may be made of magnesium alloy or the like. When the thrust member 10 is formed by die-cast molding of magnesium alloy or injection molding (metal injection molding or thixomolding), the dynamic pressure groove of the end surface 10a is formed at the same time as molding (transferred by a molding die).
can do. Further, as the shape of the dynamic pressure groove, a spiral shape, a radial groove shape or the like may be adopted.

The shaft portion 2a of the shaft member 2 is inserted in the inner peripheral surface 8a of the bearing sleeve 8, and the flange portion 2b is formed in the bearing sleeve 8.
It is housed in the space between the lower end surface 8 c and the end surface 10 a of the thrust member 10. Lubricating oil is supplied to the internal space of the housing 7 sealed by the seal portion 7a.

When the shaft member 2 rotates, the regions of the inner peripheral surface 8a of the bearing sleeve 8 which serve as the radial bearing surfaces (upper and lower two regions) respectively pass through the outer peripheral surface 2a1 of the shaft portion 2a and the radial bearing gap. opposite. Further, the region of the lower end surface 8c of the bearing sleeve 8 serving as the thrust bearing surface is the flange portion 2
The upper end face 2b1 of b is opposed to the lower end face 2b2 of the flange portion 2b via the thrust bearing gap, and the region of the end face 10a of the thrust member 10 serving as the thrust bearing face is opposed to the lower end face 2b2 of the flange portion 2b. Then, as the shaft member 2 rotates, dynamic pressure of the lubricating oil is generated in the radial bearing gap,
The shaft portion 2a of the shaft member 2 is rotatably supported in the radial direction in a non-contact manner by an oil film of lubricating oil formed in the radial bearing gap. As a result, a first radial bearing portion R1 and a second radial bearing portion R2 that rotatably support the shaft member 2 in the radial direction in a non-contact manner are configured. At the same time, a dynamic pressure of the lubricating oil is generated in the thrust bearing gap, and the flange portion 2b of the shaft member 2 is rotatably supported in both thrust directions in a non-contact manner by the oil film of the lubricating oil formed in the thrust bearing gap. . As a result, a first thrust bearing portion S1 and a second thrust bearing portion S2 that rotatably support the shaft member 2 in the thrust direction in a non-contact manner are configured.

FIG. 3 shows a hydrodynamic bearing device 1'according to another embodiment. The hydrodynamic bearing device 1'of this embodiment is different from the hydrodynamic bearing device 1 of the above-described embodiment in that a bottom portion 7d 'is integrally provided at the lower end of the housing 7'.

The housing 7'is made of, for example, a bearing sleeve 8 made of a sintered metal as an insert part, and a metal material such as a magnesium alloy is molded to form a cylindrical side portion 7 '.
b'and an annular seal portion 7a 'integrally extending from the upper end of the side portion 7b' to the inner diameter side, that is, the bottom portion 7
It is once formed into a form without d '. Then, after assembling the respective parts into a form similar to that of the hydrodynamic bearing device 1 of the above-described embodiment, the portion shown by cross-hatching in FIG. 3 is molded again with a metal material such as a magnesium alloy to form the housing 7 ′. A bottom portion 7d 'is integrally provided at the lower end portion.

FIG. 4 shows a hydrodynamic bearing device 11 according to another embodiment. The hydrodynamic bearing device 11 includes a housing 17, a bearing sleeve 18, a shaft member 12, and a thrust plate 20 as constituent parts.

A first radial bearing portion R11 is provided between the inner peripheral surface 18a of the bearing sleeve 18 and the outer peripheral surface 12a of the shaft member 12.
And the second radial bearing portion R12 are provided apart from each other in the axial direction. A thrust bearing portion S11 is provided between the lower end surface 12b of the shaft member 12 and the end surface of the thrust plate 20. For convenience of explanation, the description will proceed with the side of the thrust plate 20 as the lower side and the side opposite to the thrust plate 20 as the upper side.

The shaft member 12 is made of, for example, a metal material such as stainless steel, and its lower end surface 12b is formed in a convex spherical shape.

The bearing sleeve 18 is formed of, for example, a porous body made of a sintered metal, particularly a sintered metal porous body containing copper as a main component, in a cylindrical shape. On the inner peripheral surface 18a of the bearing sleeve 18 made of this sintered metal, two upper and lower regions, which are the radial bearing surfaces of the first radial bearing portion R11 and the second radial bearing portion R12, are provided axially separated from each other. The
Herringbone-shaped dynamic pressure grooves are formed in the two regions, respectively. The dynamic pressure groove may have a spiral shape, an axial groove shape, or the like.

The housing 17 is formed, for example, by molding (die casting or injection molding) a metal material such as a magnesium alloy using a bearing sleeve 18 made of a sintered metal as an insert part, and has a cylindrical side portion 17b. An annular seal portion 17a integrally extending from the upper end of the side portion 17b toward the inner diameter side, and a bottom portion 1 integrally continuous with the lower end of the side portion 17b.
7c and. Inner peripheral surface 17a1 of the seal portion 17a
Faces the outer peripheral surface 12a1 of the shaft member 12 via a predetermined seal space. In this embodiment, the seal portion 17
The outer peripheral surface 12a1 of the shaft member 12 that faces the inner peripheral surface 17a1 of a and forms a seal space is formed in a taper shape that gradually decreases in diameter upward (outward of the housing 17). When the shaft member 12 rotates, the tapered outer peripheral surface 12a
1 also functions as a so-called centrifugal seal. The shaft member of the above-described embodiment may be provided with such a tapered outer peripheral surface.

The housing 17 and the bearing sleeve 18 are
By the above mold molding, without undergoing a separate fixing step,
Fixed to each other. In particular, since the bearing sleeve 18 is made of sintered metal, the housing 17 and the bearing sleeve 18 are firmly brought into close contact with each other for the above-mentioned reason, and a stable fixed state between them can be obtained.

The thrust plate 20 is made of a low friction material, for example, a resin material, and is disposed on the bottom portion 17c of the housing 17.

The hydrodynamic bearing device 11 of this embodiment can be assembled by mounting the thrust plate 20 and the shaft member 12 on the housing 17 and the bearing sleeve 18, which are fixed to each other by the above-mentioned molding. . That is, the thrust plate 20 is disposed on the bottom 17c of the housing 17 through the inner peripheral surface 17a of the seal portion 17a of the housing 17 and the inner peripheral surface 18a of the bearing sleeve 18, and then the shaft member 12 is disposed on the inner peripheral surface 1 of the bearing sleeve 18.
8a, and the lower end face 12b thereof is brought into contact with the end face of the thrust plate 20. Then, lubricating oil is supplied to the internal space of the housing 17 which is sealed by the seal portion 17a.

When the shaft member 12 is rotated, the regions of the inner peripheral surface 18a of the bearing sleeve 18 which serve as the radial bearing surfaces (upper and lower two regions) are respectively separated from the outer peripheral surface 12a of the shaft member 12 by a radial bearing gap. opposite. And the shaft member 12
With the rotation, the dynamic pressure of the lubricating oil is generated in the radial bearing gap, and the shaft member 12 is rotatably supported in the radial direction by the oil film of the lubricating oil formed in the radial bearing gap in a non-contact manner. As a result, the first radial bearing portion R1 that rotatably supports the shaft member 12 in the radial direction in a non-contact manner.
1 and the 2nd radial bearing part R12 are comprised. At the same time, the lower end surface 12b of the shaft member 12 is attached to the thrust plate 2
Contact supported by 0. As a result, the thrust bearing portion S1 that rotatably supports the shaft member 12 in the thrust direction.
1 is configured.

FIG. 5 shows a hydrodynamic bearing device 21 according to another embodiment. The hydrodynamic bearing device 21 of this embodiment differs from the hydrodynamic bearing device 11 shown in FIG. 4 in that the bottom of the housing 27 is made of a low-friction material such as a resin bottom member 28. The side end face 12b is attached to the bottom member 2
This is the point of being contact-supported by 8.

The housing 27 is formed by molding a metal material using the bearing sleeve 18 made of, for example, a sintered metal as an insert part, and integrally extends from a cylindrical side portion 27b and an inner diameter side from an upper end of the side portion 27b. And an annular seal portion 27a. Then, the bottom member 28 made of resin is fixed to the lower end of the side portion 27b by an appropriate means. In this embodiment, an annular rib 27b1 is formed on the lower end of the side portion 27b, an annular recess 28a is formed on the end surface of the bottom member 28, and the recess 28a is fitted into the rib 27b1. Is attached to the lower end of the side portion 27b and fixed by ultrasonic welding or induction heating. The bottom member 28
In order to solidify the fixed state of the rib 27b1, it is preferable to form at least one of the inner peripheral surface and the outer peripheral surface of the rib 27b1 with a thread-shaped concavo-convex or a concavo-convex formed by knurling. The ribs 27b1 and the recesses 28a may be discontinuous in the circumferential direction as long as they fit into each other.

FIG. 6 shows a modification of the embodiment shown in FIG. In this modification, the resin bottom member 28 is press-fitted and fixed to the inner circumference of the lower end of the side portion 27b of the housing 27.

FIG. 7 shows a hydrodynamic bearing device 31 according to another embodiment. The hydrodynamic bearing device 31 of this embodiment differs from the hydrodynamic bearing device 11 shown in FIG. 4 in that a housing 37 is provided with a resin seal member 38. The seal member 38 includes an inner peripheral surface 38b that faces the outer peripheral surface 12a1 of the shaft member 12 and forms a seal space.

The housing 37 is formed by molding a metal material using the bearing sleeve 18 made of, for example, a sintered metal as an insert part, and a cylindrical side portion 37b and a bottom portion 37c which is integrally continuous with the lower end of the side portion 37b. And is formed into a form having. After that, a resin sealing member 38 is fixed to the upper end of the side portion 37b by an appropriate means. In this embodiment, an annular rib 37b1 is formed on the upper end of the side portion 37b, and
An annular recess 38a is formed on the end surface of the seal member 38, and the seal member 38 is attached to the upper end of the side portion 37b with the recess 38a fitted to the rib 37b1 and fixed by ultrasonic welding or induction heating. There is. In order to strengthen the fixed state of the seal member 38, it is preferable to form screw-shaped unevenness or unevenness by knurling or the like on at least one of the inner peripheral surface and the outer peripheral surface of the rib 37b1. Further, the rib 37b1 and the recess 38a may be discontinuous in the circumferential direction as long as they are fitted to each other.

According to the present invention, it is possible to provide a fluid bearing device which is much lower in cost and lighter in weight.

[Brief description of drawings]

FIG. 1 is a sectional view of a spindle motor having a hydrodynamic bearing device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a hydrodynamic bearing device according to an embodiment of the present invention.

FIG. 3 is a sectional view showing a hydrodynamic bearing device according to another embodiment of the present invention.

FIG. 4 is a sectional view showing a fluid dynamic bearing device according to another embodiment of the present invention.

FIG. 5 is a sectional view showing a fluid dynamic bearing device according to another embodiment of the present invention.

6 is a sectional view showing a hydrodynamic bearing device according to a modification of the embodiment shown in FIG.

FIG. 7 is a sectional view showing a fluid dynamic bearing device according to another embodiment of the present invention.

[Explanation of symbols]

1, 1 ', 11, 21, 31 Hydrodynamic bearing device 2,12 shaft member 7,7 ', 17,27,37 Housing 8, 18 Bearing sleeve R1, R11 1st radial bearing part R2, R12 2nd radial bearing part S1 First thrust bearing part S2 Second thrust bearing part S11 Thrust bearing part

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Claims (3)

[Claims] 1. A housing, a bearing sleeve fixed to the inner periphery of the housing, a shaft member, and a bearing gap provided between the inner peripheral surface of the bearing sleeve and the outer peripheral surface of the shaft member. A hydrodynamic bearing device comprising a radial bearing portion that supports the shaft member in a radial direction in a non-contact manner with an oil film of lubricating oil, wherein the bearing sleeve is formed of sintered metal, and the housing and the bearing sleeve are insert parts. A hydrodynamic bearing device characterized by being formed by molding with a metal material. 2. The hydrodynamic bearing device according to claim 1, wherein the metal material is a magnesium alloy. 3. The hydrodynamic bearing device according to claim 1, wherein the radial bearing portion is a dynamic pressure bearing that generates a dynamic pressure in the lubricating oil in the bearing gap.