JP2002147443A - Fluid bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin-type fluid bearing device having superior impact resistance and hardly causing unstable vibration even in changing the using environment. SOLUTION: A spindle motor is provided with a shaft 13 having a flange portion 15 integrally formed in one end, sleeves 12 opposed to each other in the shaft 13 via a fluid bearing clearance of a radial fluid bearing R, and a center hole 20 in the end surface on the side provided with the flange part 15 in both end surfaces of the shaft 13. The center hole 20 is closed by filling the center hole 20 with filler.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information device,
For hydrodynamic bearing devices used in video equipment, office machines, etc.
In particular, the present invention relates to a hydrodynamic bearing device most suitable for a magnetic disk device (hereinafter referred to as HDD), an optical disk device, and the like.

[0002]

2. Description of the Related Art Conventional hydrodynamic bearing devices of this type include:
For example, there is a spindle motor for HDD as shown in FIG. This is a cylindrical part 10 erected on a base 101.
A cylindrical housing 100 having a bottom plate 100a is inserted inside 1a, and these are integrally fixed. A cylindrical sleeve 102 is inserted into the inner peripheral surface of the housing 100 and is integrally fixed.

Further, a shaft 103 is rotatably inserted through the sleeve 102. An inverted cup-shaped hub 104 is integrally attached to the upper end of the shaft 103, and a disk-shaped thrust plate 105 is fixed to the lower end of the shaft 103 by press-fitting. This thrust plate 10
5 are the thrust receiving surfaces 10 of the thrust fluid bearing S.
5 s and 105 s. The lower end surface of the sleeve 102, which is a mating member, faces the upper thrust receiving surface 105s via a fluid bearing clearance of the thrust fluid bearing S, and the lower end surface of the sleeve 102 is opposed to the thrust bearing surface 102s of the thrust fluid bearing S. Have been.

On the lower thrust receiving surface 105s,
The upper surface of the bottom plate 100a of the housing 100, which is the mating member, opposes through the fluid bearing clearance of the thrust fluid bearing S, and the upper surface of the bottom plate 100a is the thrust bearing surface 100s of the thrust fluid bearing S. The thrust receiving surfaces 105s, 105s and the thrust bearing surface 102
s and 100s are provided with a herringbone-shaped or spiral-shaped groove for generating dynamic pressure (not shown) to constitute a thrust fluid bearing S.

[0005] Further, a pair of radial receiving surfaces 103r, 103r are formed on the outer peripheral surface of the shaft 103 at an interval above and below. Further, on the inner peripheral surface of the sleeve 102, the radial bearing surfaces 103r, 103r are opposed to the radial bearing surfaces 103r via the fluid bearing clearance of the radial fluid bearing R.
r and 102r are formed. Then, the radial receiving surfaces 103r, 103r and the radial bearing surfaces 102r, 102r
The radial fluid bearings R, R are provided with at least one of herringbone-shaped or spiral-shaped dynamic pressure generating grooves 107, 107.

A stator 108 is fixed to the outer peripheral surface of the housing 100, and a drive motor M is formed facing the rotor magnet 109 fixed below the inner peripheral surface of the hub 104 via a gap. The shaft 103 and the hub 104 are integrally rotated by the drive motor M. When the shaft 103 rotates, dynamic pressure is generated in a small amount of lubricant filled in the fluid bearing clearances of the fluid bearings S and R by the pumping action of the dynamic pressure generating grooves of the thrust fluid bearing S and the radial fluid bearing R. Thus, the shaft 103 is not in contact with the inner peripheral surface of the sleeve 102 and the upper surface of the bottom plate 100a and is supported.

In such a conventional spindle motor, the thrust plate 105 is not formed integrally with the shaft 103, but is formed separately from the shaft 103. That is, after machining the shaft 103, the thrust plate 105 is press-fitted into the shaft 103 and attached.
In the case of a shaft with a flange (a shaft and a thrust plate are integrally formed), a center hole necessary for grinding the outer peripheral surface of the shaft serving as a bearing surface is provided on the end surface of the shaft. Must be provided. However, a rod-shaped shaft (straight shaft) that does not have a flange as described above
In the case of (1), since grinding can be performed using a centerless grinding machine or the like, it is not necessary to provide a center hole on the end face of the shaft.

[0008]

In recent years, HDDs have been required to have higher recording densities, and the width of tracks for recording information has become narrower. Therefore, the use of fluid bearings with high rotational accuracy has been studied. ing. Further, HDDs mounted on portable devices such as notebook computers are required to be thinner and have excellent portability (800
There is a demand for a hydrodynamic bearing device having high shock resistance (G or more) and high reliability (unstable vibration hardly occurs even when the use environment changes).

As a method for realizing the reduction in thickness, there is a method of reducing the height of the apparatus by reducing the thickness of the thrust plate 105. However, when the thickness of the thrust plate 105 is reduced, the fixing strength when the thrust plate 105 is pressed into the shaft 103 tends to be weak. Therefore, if a large impact is applied to the spindle motor during transportation or the like, the thrust plate 105 may fall off the shaft 103.

As a method for solving such inconvenience,
There is a method of integrally forming the shaft and the thrust plate. If the shaft and the thrust plate are integrated, there is no danger of falling off even if an impact is applied. However, in a shaft having such a flange portion, in order to grind the outer peripheral surface of the shaft serving as a bearing surface using a grinder or the like, it is necessary to provide a center hole in the end surface of the shaft as described above. There is. Then, the shaft can be ground using a cylindrical grinder, an angular grinder, or the like.

On the other hand, a method of filling a lubricant in a conventional spindle motor is as follows. First, a lubricant is injected into the housing 100 (on the upper surface of the bottom plate 100a). Subsequently, the shaft 103 is inserted into the housing 100,
As shown in FIG. 2, the plane of the thrust plate 105 (the lower plane in FIG. 2) faces the upper surface of the bottom plate 100a. Thereafter, the sleeve 102 was inserted into the housing 100 while the shaft 103 was inserted through the sleeve 102, and the sleeve 102 was fixed to the housing 100 by press fitting.

Therefore, when the shaft is provided with a center hole in the end face, if the lubricant is filled by such a method, air may be trapped in the center hole and may remain. Therefore, in a use environment in which the atmospheric pressure or the temperature changes, the remaining air expands and moves and turns inside the fluid bearing clearance, so that unstable vibration is likely to occur during rotation.

In other words, if the shaft and the thrust plate are integrally formed to reduce the thickness and improve the impact resistance, the spindle motor is liable to generate unstable vibration due to a change in the use environment, resulting in poor reliability. There was a problem. Therefore, the present invention solves the problems of the conventional hydrodynamic bearing device as described above, and is thin, excellent in impact resistance,
It is another object of the present invention to provide a hydrodynamic bearing device in which unstable vibration hardly occurs even when the use environment changes.

[0014]

In order to solve the above-mentioned problems, the present invention has the following arrangement. That is, the hydrodynamic bearing device of the present invention includes a shaft having an integrally formed flange portion at one end or in the vicinity thereof, and a mating member opposed to the shaft via a fluid bearing clearance. In the hydrodynamic bearing device provided with a concave portion on an end surface of the both end surfaces on the side where the flange portion is provided, the concave portion is filled with a filler to close the concave portion.

With such a configuration, when the lubricant is filled in the hydrodynamic bearing device, the possibility that air remains in the concave portion is small. Therefore, even when the use environment of the fluid dynamic bearing device is an environment in which the atmospheric pressure or the temperature changes, unstable vibration hardly occurs during rotation. In addition, since the shaft and the flange portion are integrally formed, the hydrodynamic bearing device is excellent in impact resistance and is easily thinned.

The type of the filler is not particularly limited as long as it can close the recess and does not easily fall off, but an adhesive or a sealant is preferably used. Can be

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the hydrodynamic bearing device according to the present invention will be described in detail with reference to the drawings. FIG.
1 is a longitudinal sectional view of a thin HDD spindle motor which is an embodiment of a hydrodynamic bearing device according to the present invention. First,
The structure of the spindle motor will be described.

This spindle motor comprises a shaft 13 to which a hub 14 is fixed, and a sleeve 12 through which the shaft 13 is inserted. A radial fluid bearing R is interposed between the shaft 13 and the sleeve 12. Have been. The sleeve 1
Reference numeral 2 is inserted and fixed in a cylindrical housing 10. Further, a flange portion 15 is integrally formed at one end of the shaft 13, and a thrust fluid bearing S is provided between both surfaces of the flange portion 15 and the sleeve 12 and the housing 10 facing the flange portion 15. I have. The sleeve 1
The housing 2 and the housing 10 correspond to a mating member which is a constituent element of the present invention.

A stator 18 is provided on the outer peripheral surface of the housing 10.
Are fixed, and the drive motor M is formed facing the rotor magnet 19 fixed to the inner peripheral surface of the hub 14 via a gap. Then, the hub 1 is driven by the drive motor M.
When the shaft 4 and the shaft 13 are driven to rotate integrally, the shaft 13 is rotatably supported by the sleeve 12 by the thrust fluid bearing S and the radial fluid bearing R.

Next, the structure of the spindle motor of this embodiment as described above will be described in more detail. Base 11
A cylindrical housing 10 having a bottom plate 10a is inserted inside a cylindrical portion 11a standing upright, and these are integrally fixed. A cylindrical sleeve 12 is inserted into the inner peripheral surface of the housing 10 and is integrally fixed.

A shaft 13 is rotatably inserted through the sleeve 12. The material of the shaft 13 is not particularly limited as long as it is a material having high hardness and excellent corrosion resistance. For example, a martensitic stainless steel or an austenitic stainless steel is subjected to a heat treatment to harden the surface. Or plated or diamond-like carbon (DL
C) Surface treatment with a film to cure the surface.

The upper end 13a of the shaft 13 has a smaller diameter than the other portion. The small upper end 13a is press-fitted into a hole provided in the center of a shallow inverted cup-shaped hub 14 so that the shaft 13 has a smaller diameter. And the hub 14 are integrally fixed. Since the lower surface of the hub 14 abuts on the upper end surface 13b of the large-diameter other portion formed at the boundary between the small-diameter upper end portion 13a and the large-diameter other portion, the shaft 13 and the hub 14 are sufficiently separated from each other. With sufficient strength to ensure high impact resistance.

At the lower end of the shaft 13 projecting from the lower end of the sleeve 12, a disk-shaped flange portion 15 is formed integrally with the shaft 13. Since the flange portion 15 is formed integrally with the shaft 13, there is no possibility that the flange portion 15 will fall off the shaft 13 even if it receives a strong impact (excellent impact resistance). In addition, since the height of the apparatus can be reduced by reducing the thickness of the flange portion 15, the thickness of the spindle motor can be easily reduced.

The lower surface of the flange portion 15 is a bottom plate 1 of the housing 10 which is a mating member and corresponds to a counter plate.
0a, and the opposite surfaces are in contact when the spindle motor is stopped. The upper surface of the flange portion 15 is opposed to the lower end surface of the sleeve 12 which is a mating member. Both upper and lower planes of the flange portion 15 are thrust receiving surfaces 15s, 15s. The lower end surface of the sleeve 12 faces the upper thrust receiving surface 15s via the fluid bearing clearance of the thrust fluid bearing S, and faces the lower thrust receiving surface 15s via the fluid bearing clearance of the thrust fluid bearing S. The upper surface of the bottom plate 10a of the housing 10 is formed as thrust bearing surfaces 12s and 10s, respectively, and at least one of the opposing thrust receiving surfaces 15s, 15s and thrust bearing surfaces 12s, 10s has, for example, a herringbone shape or a spiral shape. The thrust fluid bearing S is provided with a dynamic pressure generating groove (not shown).

The method of forming the dynamic pressure generating grooves on both planes (thrust receiving surfaces 15s, 15s) of the flange portion 15 is not particularly limited.
Chemical etching, electrolytic etching and the like can be mentioned. The coining process, which is plastic working, is a method of stamping the dynamic pressure generating groove by pressing a mold against the flange portion 15 using a press or the like. Cost.

Almost the entire inner peripheral surface of the sleeve 12 is opposed to the outer peripheral surface of the shaft 13. A corner at the upper end (outside air side) of the inner peripheral surface of the sleeve 12 is chamfered as shown in FIG. 1 to form an inclined surface 12a. As a result, the uppermost portion (outside air side) of the clearance formed between the outer peripheral surface of the shaft 13 and the inner peripheral surface of the sleeve 12 gradually becomes wider toward the outside air (upward). It has a tapered shape.

With such a configuration, it is possible to prevent the lubricant from leaking out of the fluid bearing clearance to the outside when the spindle motor is stationary or rotating. As can be seen from FIG. 1, the groove 17 for dynamic pressure generation is not provided in the tapered clearance, and therefore, the tapered clearance is formed by the fluid in the radial fluid bearing R. There is no bearing clearance.

In this embodiment, the slope 12
a is provided on the inner peripheral surface of the sleeve 12,
May be provided on both the inner peripheral surface of the sleeve 12 and the outer peripheral surface of the shaft 13. Slope 1
2a is provided on the outer peripheral surface of the shaft 13, the sleeve 12
Is provided on the part closest to the outside air among the parts opposed to the inner peripheral surface of the element.

The inclined surface 12a of the sleeve 12 and a portion of the outer peripheral surface of the shaft 13 facing the inclined surface 12a
When an oil-repellent treatment such as applying an oil-repellent (having the property of repelling a lubricant) is applied, the lubricant is repelled to the oil-repelled portion. It is possible to more effectively prevent the lubricant from leaking outside beyond the treated portion.

On the other hand, a pair of radial receiving surfaces 13r, 13r is formed on the outer peripheral surface of the shaft 13 at an interval in the axial direction, and the radial receiving surfaces 13r, 13r are provided with the fluid of the radial fluid bearing R. Radial bearing surfaces 12r, 12r facing each other via a bearing clearance are formed on the inner peripheral surface of the sleeve 12. And, the radial bearing surfaces 12r, 1
The radial fluid bearings R, 2 are provided on the 2r with hydrodynamic pressure generating grooves 17, 17 having a substantially U-shaped herringbone shape. However, the dynamic pressure generating grooves 17, 17 may be provided on the radial receiving surfaces 13r, 13r, or may be provided on both the radial receiving surfaces 13r, 13r and the radial bearing surfaces 12r, 12r.

The processing method for providing the dynamic pressure generating groove 17 is not particularly limited, and the same conventional method as described above is employed. When the dynamic pressure generating groove 17 is formed on the radial bearing surface 12r, that is, on the inner peripheral surface of the sleeve 12, the dynamic pressure generating groove 17 can be formed by plastic working such as ball rolling or cutting with a cutting tool which is excellent in mass productivity. Therefore, it is preferable. Ball rolling is a method in which a rolling jig in which a plurality of steel balls are held in a hollow outer cylinder fitted on the outer periphery of a shaft is pressed into the sleeve 12 to perform processing.

That is, after the sleeve 12 is cut on a lathe, the rolling jig is pushed into the sleeve 12 and relatively moved while slowly rotating the main shaft of the lathe forward and backward, thereby forming a herringbone shape (substantially) on the inner peripheral surface. The groove processing is performed in the shape of a letter (shape), and thereafter, finishing processing such as finishing cutting or ball threading for removing a bulging portion around the groove is performed as necessary. Needless to say, the sleeve 1 is not fixed on the lathe but fixed by rotating the rolling jig right and left using the rolling device.
2 to form a herringbone groove.

Dynamic pressure generating grooves 17, 1 provided at two locations
It is preferable that the groove 7 located on the outside air side be an inward asymmetric groove pattern whose groove length is slightly shorter on the inner side than on the outside air side for the following reasons. In other words, since the pressure that pushes the lubricant in from the outside air side to the inside acts as the shaft 13 rotates (pump-in), the lubricant in the fluid bearing clearance of the radial fluid bearing R is centrifuged by the rotation of the shaft 13. It is prevented from being scattered to the outside by the force.

This will be described in more detail. The dynamic pressure generating groove 17 is composed of a plurality of substantially rectangular grooves arranged at predetermined intervals along the circumferential direction of the shaft 13. 2
Of the dynamic pressure generating grooves 17 provided at the two locations, the dynamic pressure generating groove 17 (the upper dynamic pressure generating groove 17 in FIG. 1) located on the outside air side has an axially asymmetric pattern. Shape. The other dynamic pressure generating groove 17 (FIG. 1)
In the above, the pattern of the lower dynamic pressure generating groove 17) is formed in a shape symmetrical in the axial direction.

That is, in the dynamic pressure generating groove 17 located on the outside air side, the width from the bent portion to the end on the outside air side of the axial width of the substantially U-shaped groove is set to the inside from the bent portion. Shall be larger than the width up to the end. In the present embodiment, the outside air side is opposite to the side of the shaft 13 facing the outside air of the spindle motor (upward in FIG. 1), that is, the side on which the thrust fluid bearing S is provided. It means side. The inside means the side opposite to the outside air side, that is, the side on which the thrust fluid bearing S is provided.

Further, in order to reduce bubbles from being caught in the lubricant in the fluid bearing clearances of the thrust fluid bearing S and the radial fluid bearing R during rotation, it is necessary to provide the thrust fluid bearing S and the radial fluid bearing R with dynamic fluid. It is desirable that the pressure generation groove has a groove angle (an angle formed with respect to the rotation direction) of 30 ° or less, preferably 25 ° or less, and the number of grooves is 10 or more, preferably 12 or more.

In particular, when the bearing width of the herringbone-shaped dynamic pressure generating groove 17 provided on the radial fluid bearing R (the axial width of the dynamic pressure generating groove 17) is smaller than the shaft diameter, the groove angle is reduced. It is desirable that the angle is 25 ° or less, and the number of grooves is 12 or more, preferably 16 or more. When air bubbles are caught in the lubricant, unstable vibration during rotation is caused, and rotation accuracy is likely to be deteriorated.

In order to reduce the torque of the spindle motor, the inner peripheral surface of the sleeve 12 (the outer peripheral surface of the shaft 13 or the inner peripheral surface of the sleeve 12 may be interposed between the upper and lower radial fluid bearings R, R). The clearance groove may be provided on both the surface and the outer peripheral surface of the shaft 13). The clearance groove may be formed of a tapered circumferential groove whose clearance decreases toward the fluid bearing clearance of the radial fluid bearing R.

Further, the axial position of the rotor magnet 19 and the stator 18 constituting the drive motor M is slightly shifted, so that an axial attraction force acts, and the load is mainly shared on the lower end surface side of the sleeve 12. In addition, by designing the effective area of the lower thrust receiving surface 15 s of the flange portion 15 to be smaller than the effective area of the upper thrust receiving surface 15 s (designing the effective bearing diameter to be smaller), May be reduced. Then, the power consumption of the spindle motor can be reduced.

Further, although not provided in the spindle motor of the present embodiment, an annular clearance formed of a tapered surface is provided between the outer peripheral surface of the sleeve 12 and the inner peripheral surface of the housing 10 to reduce the annular clearance. It may be used as a lubricant reservoir. Sleeve 12 forming inner surface of lubricant reservoir
At least one of the outer peripheral surface and the inner peripheral surface of the housing 10 is a tapered surface, so that the clearance of the lubricant reservoir gradually decreases toward the lower thrust fluid bearing S.

Further, the lower end of the lubricant reservoir is open toward an annular gap formed between the outer peripheral surface of the flange portion 15 and the inner peripheral surface of the housing 10 which is a member opposed thereto. A lubricant supply path is provided. The opening of the lubricant supply passage communicating with the fluid bearing clearance of the thrust fluid bearing S is substantially equal to or slightly larger than the fluid bearing clearance of the thrust fluid bearing S, and is based on the surface tension. Due to the capillary phenomenon, the lubricant is easily introduced from the lubricant supply passage into the fluid bearing clearance of the thrust fluid bearing S.

The entire lower portion of the lubricant reservoir may form a lubricant supply passage (that is, the lubricant supply passage has an annular clearance shape), but a slit is formed in one portion of the lower portion of the lubricant reservoir. May be provided (that is, the outer peripheral surface of the sleeve 12 is in contact with the inner peripheral surface of the housing 10 and the other portions are closed), and slit-shaped lubricant supply passages are provided at a plurality of locations. A lubricant supply path may be provided.

A vent hole communicating with the outside air is opened above the lubricant reservoir. For example, it may be provided so as to extend horizontally from the upper part of the lubricant reservoir, bend upward in the middle, and open to the upper end surface of the sleeve 12 (ie,
The housing 10 is provided so as to form an axial slit in a fitting surface of the housing 10 with the sleeve 12), extends vertically from the upper portion of the lubricant reservoir, and opens to the upper end surface of the sleeve 12.

In such a lubricant reservoir, the lubricant is held by capillary action based on surface tension. And
The lubricant is sucked into the narrow gap by the surface tension, while the residual air bubbles entrained at the time of assembly are separated into the wide gap and discharged through the ventilation holes. If the operation of the spindle motor is performed for a long time and the lubricant held in each fluid bearing clearance gradually evaporates or scatters and becomes insufficient, the lubricant does not have bubbles in the lubricant pool. The lubricant is sucked into the narrower gap while being guided by the tapered surface according to the shortage, and is replenished until the lubricant is filled in each fluid bearing gap. That is, as the lubricant in each fluid bearing clearance decreases, it is sucked by capillary action into each fluid bearing clearance with a narrow clearance via the lubricant supply path, and at a position where the surface tension of the tapered surface of the lubricant reservoir is balanced. Stabilize. Thus, the lubricant is automatically replenished by the reduced amount of the lubricant.

As described above, when the lubricant reservoir is provided, the lubricant is automatically and reliably supplied to each fluid bearing clearance, and is always filled with the lubricant, so that the spindle motor can be used for a long time. Even so, it has high reliability and excellent durability. Therefore, even if the injection amount of the lubricant is excessive or insufficient, the possibility that the lubricant is scattered to the outside or the lubricant in each fluid bearing clearance is depleted during a long-term use is small.

Next, a method for filling the spindle motor with a lubricant will be described. The filling of the spindle motor with the lubricant is performed during the assembly of the spindle motor. First, in the housing 10 (on the upper surface of the bottom plate 10a)
Inject lubricant. Then, the shaft 13 is placed in the housing 10.
And the flat surface of the flange portion 15 (the lower flat surface in FIG. 1) is opposed to the bottom plate 10a as shown in FIG. Thereafter, while the shaft 13 is inserted through the sleeve 12,
Is inserted into the housing 10, and the sleeve 12 is fixed to the housing 10 by press fitting.

At this time, a center hole 20 is provided on the end face of the both ends of the shaft 13 where the flange portion 15 is provided.
Is provided. Note that the center hole 20 corresponds to a concave portion which is a constituent element of the present invention. Such a center hole 20 is not necessary for a straight shaft, but for a shaft having a flange portion, the outer peripheral surface of the shaft serving as a bearing surface is ground by a grinding machine such as a cylindrical grinder or an angular grinder. It is necessary to perform using.

In the spindle motor of this embodiment, the center hole 20 is filled with a filler, and the center hole 20 is closed. The type of the filler is not particularly limited as long as it can close the center hole 20 and does not easily fall off, and examples thereof include an adhesive and a sealant. Specifically, an epoxy adhesive or the like can be used as the adhesive, and a silicone resin or the like can be used as the sealant.

In order to prevent the filler from protruding from the center hole 20 and adhering to the lower thrust receiving surface 15s when the filler is filled into the center hole 20, for example,
It is preferable to form a shallow annular groove 21 (a groove having a depth H in FIG. 1) continuously around the center hole 20. Then, even if the filler protrudes from the center hole 20, the filler is stored in the annular groove 21, so that there is little possibility that the filler adheres to the lower thrust receiving surface 15s.

When the center hole 20 is provided on the end face of the shaft 13 and the lubricant is filled by the above-described method, there is a high possibility that air is trapped in the center hole 20 and remains. Then, in a use environment in which the atmospheric pressure and temperature change, the remaining air expands and moves and turns inside the fluid bearing clearance, so that unstable vibration is likely to occur during rotation.

However, in the spindle motor of the present embodiment, since the center hole 20 is previously closed with the filler, no air remains in the center hole 20 during assembly of the spindle motor and injection of the lubricant. . For this reason, unstable vibration due to the influence of bubbles is less likely to occur during rotation. In addition, since even a small amount of air bubbles may cause unstable vibration, use a lubricant that has been vacuum-degassed in advance, or use a spindle The motor may be placed in a vacuum chamber, and the lubricant may be filled in each of the fluid bearing gaps while vacuum degassing.

The injection of the lubricant into the spindle motor may be performed by the following method. That is,
A through hole having a through hole in the thickness direction may be provided at the center of the bottom plate 10a, and after assembling the whole, a lubricant may be injected from the through hole using a dispenser or the like. After the lubricant is injected into the spindle motor, a ball, a cylindrical member, or the like is pressed into the through hole to seal the through hole.

In such a spindle motor, when a hub 14 and a shaft 13 on which a magnetic disk (not shown) to be rotated is mounted on the outer periphery by a drive motor M are integrally rotated, the thrust fluid bearings S and Due to the pumping action of each dynamic pressure generating groove of the radial fluid bearing R, dynamic pressure is generated in the lubricant filled in the fluid bearing clearance of each fluid bearing S, R, and the shaft 13 is moved to the sleeve 12 and the housing 1.
The base plate 10a is not in contact with the bottom plate 10a and is supported. Since the magnetic disk is screwed with a clamp member, the magnetic disk is fixed with sufficient strength to ensure sufficient impact resistance.

The present embodiment is an example of the present invention, and the present invention is not limited to the present embodiment. For example, a spindle motor is
A shaft rotation type or a shaft fixed-sleeve rotation type may be used. Further, the position of the flange portion 15 provided on the shaft 13 is not limited to the shaft end, and may be near the shaft end or at the center of the shaft.

Further, in the spindle motor of the present embodiment, a bottom plate 10a which is a member (corresponding to a counter plate) forming a thrust fluid bearing S facing the lower surface of the flange portion 15 is integrated with the housing 10. ing. However, it goes without saying that a configuration in which the bottom plate 10a is separate from the housing 10 instead of such a configuration may be used. Further, a configuration in which the housing 10 and the base 11 are integrated with each other does not matter at all.

Further, the structure of the hydrodynamic bearing, the pattern of the groove for generating dynamic pressure, the detailed structure of the spindle motor, and the like are not limited to the present embodiment, but are necessary if the object of the present invention can be achieved. Can be changed as appropriate. Furthermore, the dynamic pressure generating groove is not limited to a herringbone shape or a spiral shape, and any groove pattern may be used as long as it functions as a hydrodynamic bearing. In addition, etching, electrolytic etching, plastic processing, cutting, laser processing, ion beam processing, shot blast, or the like can be applied to the groove according to the material and the required accuracy.

Further, the materials of the members constituting the spindle motor such as the shaft 13 and the sleeve 12 are not particularly limited, and metals (stainless steel, copper alloy, aluminum, etc.) usually used for the members constituting the spindle motor are not limited. Alloys), sintered metals, sintered oil-impregnated metals, plastics, ceramics and the like can be used without any problems. That is,
It may be a combination of stainless steel or copper alloy,
A combination of dissimilar metals such as iron and copper alloy, iron and aluminum alloy, or a combination of metal and plastic may be used. Of course, a surface treatment such as plating or a DLC film (diamond-like carbon coating) may be applied to the fluid bearing surface as necessary to improve the slidability at the time of starting and stopping.

Further, in this embodiment, the spindle motor has been described as an example of the hydrodynamic bearing device. However, the present invention can be applied to various other hydrodynamic bearing devices.

[0059]

As described above, the hydrodynamic bearing device of the present invention is thin, has excellent impact resistance, and does not easily generate unstable vibration even when the operating environment changes.

[Brief description of the drawings]

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

FIG. 2 is a longitudinal sectional view of a conventional spindle motor.

[Explanation of symbols]

 Reference Signs List 10 Housing 12 Sleeve 13 Shaft 15 Flange 20 Center hole R Radial fluid bearing S Thrust fluid bearing

Claims (1)

[Claims] A shaft having an integrally formed flange at one end or in the vicinity thereof; and a mating member opposed to the shaft via a fluid bearing clearance. A fluid bearing device comprising a concave portion on an end surface on a side provided with a flange portion, wherein the concave portion is filled with a filler to close the concave portion.