JP2002130258A - Hydrodynamic bearing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrodynamic bearing unit, having no deformation of a base and a counter member, when adhered them and further minimizing the chance of a lubricating agent filled up in the inside from flowing out of a fixed portion between the base and counter member. SOLUTION: In the hydrodynamic bearing unit provided with a shaft 13, having a thrust plate 15 at an end, a sleeve 12 facing the shaft 13 via clearance of a hydrodynamic bearing of a radial hydrodynamic bearing R, a counter plate 16 facing one part of a plane of the thrust plate 15 via clearance of a hydrodynamic bearing of a thrust hydrodynamic bearing S, and a base 11 for attaching the counter plate 16, a guide face arranged the counter plate 16 at a prescribed position of the base 11 is provided in the counter plate 16 and clearance 30A and 30B is also provided between the counter plate 16 and the base 11. An adhesive agent A, firmly fixing both the counter plate 16 and base 11, is filled in the clearance 30A and 30B.

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 An example of such a hydrodynamic bearing device under development is a spindle motor for an HDD as shown in FIG. A cylindrical sleeve 2 is inserted inside a cylindrical portion 1a erected on a base 1 of the spindle motor, and these are integrally fixed. And
The shaft 3 is rotatably inserted into the sleeve 2, and a hydrodynamic bearing is interposed between the shaft 3 and the sleeve 2.

[0003] An inverted cup-shaped hub 4 is integrally attached to the upper end of the shaft 3, and a disk-shaped thrust plate 5 is fixed to the lower end of the shaft 3 by press-fitting. Both planes of the thrust plate 5 are thrust receiving surfaces 5s, 5s of the thrust fluid bearing S. The lower end surface of the sleeve 2 is opposed to the thrust receiving surface 5s on the upper surface via a thrust fluid bearing clearance, and the lower end surface of the sleeve 2 is the thrust bearing surface 2s of the thrust fluid bearing S.

[0004] Below the thrust plate 5, a counter plate 6, which is a mating member, is arranged and fixed to the base 1. The upper surface of the counter plate 6 faces the thrust receiving surface 5s on the lower surface side of the thrust plate 5 via a thrust fluid bearing clearance, and forms a thrust bearing surface 6s of the thrust fluid bearing S. At least one of the thrust receiving surfaces 5s, 5s and the thrust bearing surfaces 2s, 6s is provided with a herringbone-shaped or spiral-shaped groove for generating dynamic pressure (not shown), and a thrust fluid bearing S is provided.
Is configured.

[0005] Further, a pair of radial receiving surfaces 3r, 3r are formed on the outer peripheral surface of the shaft 3 at an interval vertically. A radial receiving surface 3 is provided on the inner peripheral surface of the sleeve 2.
Radial bearing surfaces 2r, 2r are formed so as to oppose r, 3r via a radial fluid bearing clearance. At least one of the radial receiving surfaces 3r, 3r and the radial bearing surfaces 2r, 2r is provided with a herringbone-shaped or spiral-shaped groove 7 for generating dynamic pressure, so that the radial fluid bearings R,
R is configured.

A stator 8 is fixed to the outer peripheral surface of the cylindrical portion 1a, and a driving motor M is formed facing the rotor magnet 9 fixed below the inner peripheral surface of the hub 4 via a gap. The shaft 3 and the hub 4 are integrally rotated by the drive motor M. Axis 3
Rotates, a 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. The shaft 3 is not in contact with the sleeve 2 and the counter plate 6 and is supported.

In such a spindle motor under development, the counter plate 6 is fixed to the base 1 by caulking. That is, after inserting the counter plate 6 into a hole provided at the center of the lower surface of the base 1, a ring-shaped caulking jig is fitted into an annular groove 1c provided outside the hole, and the hole and the annular groove 1c are inserted. The counter plate 6 is caulked and fixed to the base 1 by plastically deforming the projection 1d formed between the base plate 1 and the inner side (toward the center) by a caulking jig.

By fixing in this manner, the counter plate 6 has sufficient fixing strength even with a limited thickness, and the impact resistance of the entire apparatus has been improved.

[0009]

The HDD mounted on a portable device such as a notebook personal computer is required to be thinner and lighter and to have an improved recording density. Therefore, adoption of a fluid bearing is being studied. However, if the counter plate 6, which is the mating member, is fixed to the base 1 by crimping as described above, it is necessary to increase the pressing load during crimping in order to improve the shock resistance of the entire apparatus. It has been found that there is a problem that deformation of the counter plate 1 and the counter plate 6 cannot be avoided.

That is, in order to make the spindle motor thinner and lighter, the base 1 made of aluminum die-cast has a thinner bottom plate 1b. Therefore, it is inevitable that the bottom plate 1b is deformed by the pressing load at the time of caulking. Also, even if the thickness of the bottom plate portion 1b is slightly increased,
There is a problem that the thrust bearing surface 6s formed on the upper surface of the counter plate 6 is deformed by the pressing load at the time of caulking, and the flatness of the thrust bearing surface 6s is reduced.

Further, in the fixing by caulking, the base 1
Incomplete prevention of the lubricant from flowing out from the fixed portion (joint portion) between the motor and the counter plate 6 causes the lubricant filled in the spindle motor to flow out from the clearance of the fixed portion during rotation of the spindle motor. It turned out that there was a problem that there was a risk of doing so. Therefore, the present invention solves the problems of the hydrodynamic bearing device under development as described above, and there is no deformation of the base and the mating member at the time of fixing, and the lubricant filled inside is equal to the base. An object of the present invention is to provide a hydrodynamic bearing device that is less likely to flow out of a portion fixed to a mating member.

[0012]

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, a shaft having a flange portion at one end,
A sleeve opposed to the shaft via a fluid bearing clearance of a radial fluid bearing, a mating member opposed to one plane of the flange portion via a fluid bearing clearance of a thrust fluid bearing, and a base to which the mating member is attached And a guide surface for disposing the mating member at a predetermined position on the base is provided on at least one of the mating member and the base, and between the mating member and the base. A gap is provided, and an adhesive for fixing the mating member and the base is filled in the gap.

In this way, if the base and the mating member are fixed by bonding, as in the case of fixing by caulking,
Since no load is applied to the base and the mating member at the time of fixing, no deformation occurs to the base and the mating member. Also, since the gap is filled with the adhesive, the fixed portion between the base and the mating member is sealed with the adhesive,
It is less likely that the lubricant filled in the hydrodynamic bearing device will flow out of the fixed portion during rotation of the hydrodynamic bearing device.

The fixing between the base and the mating member may be performed by using a set screw in addition to the adhesive. Then, the fixing strength can be significantly improved as compared with the case of using only the adhesive. Further, the base may be fixed to the mating member by using a pin in addition to the adhesive. If the adhesive is filled between the base and the pin and between the mating member and the pin, the bonding area becomes large, so that the fixing strength between the base and the mating member is significantly improved.

Further, when the adhesive has fluidity, it is preferable that an adhesive reservoir communicating with the clearance is provided adjacent to the fixed portion between the base and the mating member. Then, since the gap is filled with the adhesive when the adhesive is injected into the adhesive pool, the operation of filling the gap with the adhesive becomes easier, and has a fluidity. The adhesive can be prevented from diffusing to the surroundings until the adhesive solidifies.

[0016]

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.
Is a fluid dynamic bearing device according to an embodiment of the present invention.
FIG. 2 is a sectional view of a spindle motor for D, and FIG.
FIG. 6 is an enlarged cross-sectional view showing a portion fixed to the fixing member 6.

First, the structure of the spindle motor will be described. This spindle motor includes 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. . Further, a thrust plate 15 is provided at one end of the shaft 13, and a thrust fluid bearing S is provided between both planes of the thrust plate 15 and the sleeve 12 and the counter plate 16 opposed thereto. In addition, the thrust plate 15 corresponds to a flange portion which is a component of the present invention, and the counter plate 16 corresponds to a mating member which is a component of the present invention.

The base 11 to which the sleeve 12 is fixed
A stator 18 is fixed to the outer peripheral surface of the cylindrical portion 11a, and a driving motor M is formed so as to face the rotor magnet 19 fixed to the inner peripheral surface of the hub 14 via a gap. When the hub 14 and the shaft 13 are integrally rotated by the drive motor M, the shaft 13 is rotatably supported on the sleeve 12 by the thrust fluid bearing S and the radial fluid bearing R. I have.

Next, the structure of the spindle motor of this embodiment as described above will be described in more detail. Base 11
A sleeve 12 having a cylindrical shape with a flange is inserted inside a cylindrical portion 11a provided upright at a central portion of the cylindrical portion, and is integrally fixed by the flange 12f. As a result, a lubricant reservoir 22 having an annular clearance is formed between the outer peripheral surface of the sleeve 12 and the inner peripheral surface of the cylindrical portion 11a. The structure of the lubricant reservoir 22 will be described later in more detail.

A shaft 13 (solid shaft) is rotatably inserted into the sleeve 12, and the shaft 13 has a concave portion on its upper end surface, and a female screw 13f is formed on the inner peripheral surface of the concave portion. . The recess and the female screw 13f may not be provided. Further, the shaft 13 may be a hollow shaft. 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 form a surface. A cured product or a product obtained by performing surface treatment with plating or a diamond-like carbon (DLC) film to cure the surface may be used.

The upper end 13a of the shaft 13 has a diameter smaller than that of the other portion, and the small upper end 13a is press-fitted into a hole provided in the center of a shallow inverted cup-shaped hub 14 to thereby form the shaft 13a. 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.

A disk-shaped thrust plate 15 is fixed to the lower end of the shaft 13 projecting from the lower end of the sleeve 12. That is, the lower end portion 13c of the shaft 13 has a smaller diameter than the other portion similarly to the upper end portion 13a, and the lower end portion 13c having the small diameter is press-fitted into a hole provided in the center portion of the thrust plate 15 so that the shaft 13 is pressed. And the thrust plate 15 are integrally fixed.

Since the upper surface of the thrust plate 15 is in contact with the lower end surface 13d of the large diameter other portion formed at the boundary between the small diameter lower end portion 13c and the large diameter other portion.
The thrust plate 3 and the thrust plate 15 are fixed with sufficient strength (unloading load) to secure sufficient impact resistance. In addition, as a method of attaching the thrust plate 15 to the shaft 13, besides the press-fitting described above, a conventional fixing method such as screwing, bonding, welding or the like can be adopted. Alternatively, a member in which the shaft and the thrust plate are integrally formed may be used.

As an example, a method of fixing the thrust plate 15 to the shaft 13 by screwing will be described. The thrust plate 15 is fixed by a set screw screwed to a female screw provided on the inner peripheral surface of the hollow shaft 13, and the shaft 13 and the thrust plate 15 have strength enough to secure sufficient impact resistance. (Extraction load).

At this time, the shaft 13 has a screw mounting portion having a cylindrical surface having a diameter larger than its inner diameter on the lower end surface, and a set screw is provided between the head and the tip having a male screw. The screw mounting portion and the cylindrical portion have substantially the same diameter as a hole for inserting a set screw provided at the center of the thrust plate 15. Since the thrust plate 15 is mounted on the shaft 13 by fitting the cylindrical portion into the hole and the screw mounting portion, the inner peripheral surface (cylindrical surface) of the screw mounting portion passes through the cylindrical portion of the set screw. Acting as a guide surface for guiding the thrust plate 15 coaxially with the shaft 13, the thrust plate 15
Mounted with a coaxiality of μm or less.

Further, the thrust plate 15 is arranged in such a manner that the upper surface of the thrust plate 15 is in contact with the lower end surface of the shaft 13.
Is attached to the shaft 13, so that the end face of the thrust plate 15 has a small run-out even if the thickness of the thrust plate 15 is small. Further, when the thrust plate 15 is attached by screwing, sufficient fastening strength is secured, and unlike the case of attachment by press fitting, the thrust plate 15
A material such as a copper alloy having a low Young's modulus can be used.

As the shape of the head of the set screw, besides a flat head, a round head such as a round head screw, a countersunk head such as a flat head screw, and the like can be used. When the thrust plate 15 is fixed to the shaft 13 by screwing, it is preferable to provide a recess for accommodating the head of the set screw at the center of the upper surface of the counter plate 16 (at a position directly below the shaft 13). Then, it is not necessary to mount the set screw in the form of being immersed in the thrust plate 15, and the processing of the thrust plate 15 becomes easy.

When a set screw for fixing the thrust plate 15 is mounted in a state where the head is immersed, or when the thrust plate 15 is press-fitted and fixed to the shaft 13, a recess for accommodating the head of the set screw is provided. Need not be provided. The lower surface of the thrust plate 15 is opposed to the upper surface of the counter plate 16 attached to the center of the base 11, and the opposed surfaces are in contact when the spindle motor is stopped. Also, the upper surface of the thrust plate 15
It faces the lower end surface of the sleeve 12.

Both upper and lower planes of the thrust plate 15 are thrust receiving surfaces 15s, 15s. The lower end surface of the sleeve 12 facing the thrust receiving surface 15s on the upper surface via the thrust fluid bearing clearance, and the upper surface of the counter plate 16 facing the thrust receiving surface 15s on the lower surface via the thrust fluid bearing clearance. The thrust bearing surfaces 12s and 16s, respectively, and at least one of the opposed thrust receiving surfaces 15s and 15s and the thrust bearing surfaces 12s and 16s are provided with a herringbone-shaped or spiral-shaped groove for generating dynamic pressure (not shown). ) To constitute the thrust fluid bearing S.

In particular, the herringbone-shaped dynamic pressure generating groove provided on the thrust receiving surface 15s or the thrust bearing surface 16s is formed so that the groove length on the outer peripheral side from the groove top is shorter than the groove length on the inner peripheral side from the groove top. It is preferable to have a slightly asymmetric groove pattern facing outward in the direction. Then, since the pumping action generated by the rotational drive is smaller on the outer peripheral side than on the groove top than on the inner peripheral side, the lubricant is sent out from the central part toward the outer peripheral part.

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

In particular, when a copper alloy having a low hardness is used for the thrust plate 15, plastic working by coining is easy, so that there is an advantage that mass productivity is excellent.
It is preferable that the sleeve 12 and the counter plate 16 have high hardness because they require strength. On the other hand, a pair of radial receiving surfaces 13r, 13r are formed on the outer peripheral surface of the shaft 13 at an interval in the axial direction and are opposed to the radial receiving surfaces 13r, 13r via a radial fluid bearing clearance. The radial bearing surfaces 12r, 12r are formed on the inner peripheral surface of the sleeve 12. A radial fluid bearing R is provided on at least one of the radial receiving surface 13r and the radial bearing surface 12r, for example, with a U-shaped herringbone-shaped groove 17 for generating dynamic pressure. 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 is formed by plastic working such as ball rolling or cutting by a cutting tool which is excellent in mass productivity. Is preferred because it can be processed. 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 to the outer periphery of a shaft is pressed into a sleeve.

That is, after the sleeve 12 is cut on a lathe, the rolling jig is pushed into the sleeve 12 while slowly rotating the main shaft of the lathe forward and backward, thereby forming a herringbone shape on the inner peripheral surface. After that, a finishing process such as finish cutting or ball-through for removing a raised portion around the groove is performed as necessary. Of course, instead of using a lathe, the rolling jig may be pressed into the fixed sleeve 12 while rotating the rolling jig forward and backward in the left and right directions to form a herringbone groove.

Groove 1 for generating dynamic pressure of this radial fluid bearing R
It is preferable that 7 is an inward asymmetric groove pattern in which the groove length is slightly shorter on the inner side than on the outer side for the following reasons. In other words, the pressure that pushes the lubricant from the outside air side to the opposite side acts with the rotation of the shaft 13 (pump-in), so that the centrifugal force caused by the rotation of the shaft 13 causes the inside of the fluid bearing clearance of the radial fluid bearing R to move. Lubricant is prevented from scattering to the outside.

This will be described in more detail. The dynamic pressure generating groove 17 is composed of a plurality of substantially V-shaped grooves arranged at predetermined intervals along the circumferential direction of the shaft 13. .
Of the dynamic pressure generating grooves 17, 17 provided at 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 a pattern in the axial direction. The shape is asymmetric. Then, the pattern of the other dynamic pressure generating groove 17 (the lower dynamic pressure generating groove 17 in FIG. 1) is changed to
The shape is 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 width in the axial direction of the substantially U-shaped groove is reversed from the bent portion. It is larger than the width up to the side 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.

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) is sandwiched between the upper and lower radial fluid bearings R, R. The clearance groove 21 may be a tapered peripheral groove whose clearance becomes narrower toward the bearing clearance of the radial fluid bearing R on both the surface and the outer peripheral surface of the shaft 13).

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 is applied, 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 thrust receiving surface 15s on the lower surface side of the thrust plate 15 to be smaller than the effective area of the thrust receiving surface 15s on the upper surface side (designing the effective bearing diameter to be small), the anti-load can be reduced. The bearing torque on the side may be reduced. Then, the power consumption of the spindle motor can be reduced.

Next, the structure of the lubricant reservoir 22 will be described. An annular clearance is interposed between the outer peripheral surface of the sleeve 12 and the inner peripheral surface of the cylindrical portion 11a, and the annular clearance forms a lubricant reservoir 22. The inner peripheral surface of the cylindrical portion 11a forming the inner surface of the lubricant reservoir 22 is formed as a tapered surface 24, whereby the clearance of the lubricant reservoir 22 gradually decreases toward the lower thrust fluid bearing S.

However, the tapered surface 24 is not always formed on the inner peripheral surface of the cylindrical portion 11a, but may be formed on the outer peripheral surface of the sleeve 12, or the outer peripheral surface of the sleeve 12 and the inner peripheral surface of the cylindrical portion 11a. May be formed on both.
The tapered surface 24 may be tapered to the position where the counter plate 16 is located. At the lower end of the lubricant reservoir 22, an opening is formed toward an annular gap formed between the outer peripheral surface 15a of the thrust plate 15 and the inner peripheral surface of the cylindrical portion 11a which is a member opposed thereto. A lubricant supply passage 25 is provided.

The opening of the lubricant supply passage 25, which communicates with the fluid bearing clearance of the thrust fluid bearing S in close proximity,
Is approximately equal to the fluid bearing clearance of the thrust fluid bearing S,
Alternatively, the lubricant is slightly larger, so that the lubricant is easily introduced from the lubricant supply passage 25 to the fluid bearing clearance of the thrust fluid bearing S by a capillary phenomenon based on the surface tension.

In the present embodiment, the entire lower portion of the lubricant reservoir 22 having an annular clearance forms a lubricant supply passage 25 (that is, the lubricant supply passage 25 has an annular clearance shape). A slit-shaped lubricant supply passage 25 may be provided at one position in the lower part of the agent reservoir 22 (that is, in the other portions, the outer peripheral surface of the sleeve 12 and the inner peripheral surface of the cylindrical portion 11a are in contact with each other. And a slit-shaped lubricant supply passage 25 may be provided at a plurality of locations.

In this embodiment, the cylindrical portion 11
The entirety of the inner peripheral surface of the a
A part of the tapered surface 24 is used as a lubricant supply passage 25, and an annular clearance formed between the outer peripheral surface 15a of the thrust plate 15 and the inner peripheral surface of the cylindrical portion 11a has a tapered surface 24.
Is communicated directly. However, the upper portion of the inner peripheral surface of the cylindrical portion 11a is a tapered surface 24, and the lower portion is a surface parallel to the outer peripheral surface of the sleeve 12, and an annular clearance formed by this parallel surface forms the lubricant supply passage 25. Such a structure may be adopted.

In the upper part of the lubricant reservoir 22,
An exhaust hole 23 communicating with the outside air is open. Exhaust hole 23
Extends vertically from the uppermost portion of the lubricant reservoir 22 and opens at the upper end surface of the sleeve 12. Of course, the exhaust holes 23
May be provided so as to form an axial slit on the surface of the cylindrical portion 11a to be fitted with the sleeve 12. Further, a corner at the upper end (outside air side) of the inner peripheral surface of the sleeve 12 is chamfered. 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 is tapered such that the clearance gradually increases upward (outside air side). It has a shape.
At this time, the angle formed by the tapered shape, that is, the angle formed between the inclined surface of the chamfered portion and the outer peripheral surface of the shaft 13 is α
And

Then, the angle α formed by the tapered shape is
Is larger than the angle formed between the outer peripheral surface of the sleeve 12 (that is, the tapered surface 24) and the inner peripheral surface of the cylindrical portion 11a (hereinafter, referred to as the inclination angle of the tapered surface 24). With such a configuration, since the surface tension acts strongly on the narrower gap, the lubricant is more strongly sucked into the lubricant reservoir 22 than the tapered gap of the chamfered portion, The liquid level of the lubricant located at the chamfered portion can be lowered and can be maintained below the chamfered portion.

Further, the volume of the lubricant reservoir 22 is
Of the gap formed between the outer peripheral surface of the sleeve 3 and the inner peripheral surface of the sleeve 12 is a tapered portion at the uppermost portion (that is, the inclined surface of the chamfered portion and the shaft 13).
If the volume of the outer peripheral surface is larger than that of the portion facing the inclined surface (the portion surrounded by the inclined surface), excess lubricant is retained in the lubricant reservoir 22.

Therefore, even if the amount of the injected 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 reduced. Therefore, the long-term reliability of the spindle motor is excellent. In order to sufficiently exhibit the above-described effects, it is preferable that the inclination angle of the tapered surface 24 is 0 ° or more and less than 45 °, and the angle α formed by the tapered shape is 45 ° or more. In particular, the inclination angle of the tapered surface 24 is set to 10 °
When the following conditions are satisfied, the above-mentioned effect is more sufficiently exhibited. In addition, in order to suction and hold the excess lubricant in the lubricant reservoir 22 by surface tension, in practice, the angle α formed by the tapered shape is set to be larger than the inclination angle of the tapered surface 24 by 15 ° or more. preferable.

In order to widen the bearing span, which is the distance between the two radial fluid bearings R, R within the determined device height, the outer peripheral surface of the shaft 13 and the inner peripheral surface of the sleeve 12 must be widened. The length of the tapered portion of the gap formed between them, that is, the axial width of the inclined surface of the chamfered portion needs to be smaller. On the other hand, since it is necessary to retain as much excess lubricant as possible in the lubricant reservoir 22, the angle α formed by the tapered shape is set to 4 °.
It is desirable that the width of the inclined surface in the axial direction be 5 mm or more and 1 mm or less, preferably 0.5 mm or less. further,
In order to increase the long-term reliability, it is necessary to secure a sufficient amount of the lubricant that can be held in the lubricant reservoir 22. Therefore, the axial width of the tapered surface 24 is set to 2 times the axial width of the inclined surface.
It is preferable that the number be twice or more.

The width (radial width) of the widest part of the tapered clearance of the chamfered part
Is larger than the width (radial width) of the widest part of the lubricant reservoir 22, and is held by the lubricant level located in the chamfered portion and the lubricant reservoir 22. The liquid level of the lubricant is at a position where the surface tension is balanced. Accordingly, the liquid level of the lubricant located in the chamfered portion can be maintained below the chamfered portion, and the lubricant is prevented from scattering from the chamfered portion to the outside with the rotation.

In this embodiment, the inclined surface is provided on the inner peripheral surface of the sleeve 12 (that is, the chamfered portion is provided on the inner peripheral surface of the sleeve 12).
It may be provided on the outer peripheral surface of the shaft 13 or the sleeve 12
And the outer peripheral surface of the shaft 13 may be provided. When the inclined surface is provided on the outer peripheral surface of the shaft 13, the inclined surface is provided on the outermost air side portion among the portions facing the inner peripheral surface of the sleeve 12.

Further, an oil repellent (having a property of repelling a lubricant) is applied to the inclined surface of the chamfered portion of the sleeve 12 and a portion of the outer peripheral surface of the shaft 13 facing the inclined surface. When the oil repellent treatment is performed, the lubricant is repelled to the portion subjected to the oil repellent treatment, and the lubricant leaks outside the part (the chamfered part or the like) when the spindle motor is stationary or rotating. Can be more effectively prevented.

Next, a method of injecting a lubricant into the spindle motor will be described. The lubricant is injected into the spindle motor by using a dispenser or the like through a through hole 26 formed in the center of the counter plate 16 and having a through hole in the thickness direction after assembling the whole. As described above, since the lubricant can be injected from the outside through the through hole 26, the injection operation of the lubricant is easy. Further, the lubricant injected from the through hole 26 gradually spreads and fills the respective fluid bearing clearances by utilizing the surface tension, so that the lubricant is injected into the inside of the device (in each fluid bearing clearance). Air bubbles are less likely to get caught in the air. In order to more reliably deaerate the bubbles, a lubricant that has been previously vacuum degassed may be used, or the spindle motor may be put into a vacuum chamber and deaerated after the lubricant has been injected.

The injected lubricant fills each of the fluid bearing clearances of the thrust fluid bearing S and the radial fluid bearing R by the surface tension, and excess lubricant is supplied to the lubricant supply passage 2.
5 and is accumulated in the lubricant reservoir 22 and is held on the tapered surface 24 by capillary action based on surface tension. Therefore, even if the injection amount of the lubricant is excessive, there is no problem because the excess lubricant is stored in the lubricant reservoir 22. Further, even if the spindle motor is inverted during transportation or handling, the lubricant in the lubricant reservoir 22 does not flow out.

Further, since the size of the clearance of the lubricant reservoir 22 becomes narrower toward the lower lubricant supply passage 25 due to the tapered surface 24, the lubricant scattered by the external impact does not flow out. Are naturally collected in the lubricant supply passage 25 having a narrow clearance in the lubricant reservoir 22. The air bubbles collected at the upper part (the one with a larger gap) of the lubricant reservoir 22 are discharged to the outside through the exhaust holes 23.

After injecting lubricant into the spindle motor,
By press-fitting the ball 27 into the through hole 26, the through hole 26 is sealed. The ball 27 may be a cylindrical member or the like. In order to prevent the press-fit ball 27 from falling off due to an external impact and preventing oil from leaking from the clearance of the ball press-fit portion, a sheet member, an adhesive seal member, or the like is bonded to the lower surface of the counter plate 16 after the press-fit of the ball 27. (Not shown). However, since the through hole 26 does not necessarily need to be sealed in terms of the performance of the fluid bearing, it may be used for venting air after it is used as a lubricant inlet.

The injection of the lubricant into the spindle motor may be performed through the exhaust hole 23 during the assembly of the spindle motor. In this case, the through hole 26 need not be provided. Further, when the hollow shaft 13 is used, the shaft 13
May be performed from a hole (a hole penetrating the shaft 13 in the axial direction) of the shaft. However, when the thrust plate 15 is screwed, it is necessary to provide a hole through the set screw in the axial direction so that the lubricant can be injected through the hole of the shaft 13.

The drive motor M causes the hub 14 and the shaft 1 on which a magnetic disk (not shown) to be rotated is mounted on the outer periphery.
3 and the thrust fluid bearing S
Further, due to the pumping action of each dynamic pressure generating groove of the radial fluid bearing R, a dynamic pressure is generated in the lubricant filled in the fluid bearing clearance of each fluid bearing S, R, so that the shaft 13 becomes the sleeve 12 and the counter plate. No contact with 16 and it 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.

When a centrifugal force acts upon the rotation, the lubricant in the lubricant reservoir 22 descends along the tapered surface 24,
The lubricant reaches the lubricant supply passage 25 having a narrow clearance and is held there.
Then, the lubricant is reliably supplied from the lubricant supply passage 25 to the clearance of the fluid bearing by a capillary phenomenon. Also, even if there are bubbles remaining in the fluid bearing clearance, the bubbles are immediately released to the outside air via the exhaust holes 23 opened in the lubricant reservoir 22.

When the lubricant retained in the fluid bearing clearance gradually evaporates or scatters and runs short over a long period of operation, the lubricant is retained in the lubricant reservoir 22 by capillary action based on surface tension. The lubricated lubricant is sucked into the narrower gap while being guided by the tapered surface 24 according to the shortage, and is replenished until the lubricant is filled in the fluid bearing clearance. That is, as the lubricant in the fluid bearing clearance decreases, the lubricant is sucked by the capillary bearing via the lubricant supply passage 25 into the fluid bearing clearance having a smaller clearance, and the surface tension of the tapered surface 24 of the lubricant reservoir 22 is balanced. And stabilized. Thus, the lubricant is automatically replenished by the reduced amount of the lubricant.

As described above, in the spindle motor according to the present embodiment, since the annular clearance of the lubricant reservoir 22 is tapered, the lubricant is sucked toward the narrower clearance by the surface tension, while the residual air bubbles that are entrained during assembly are collected. Is separated and discharged to the larger gap. Accordingly, a lubricant having no air bubbles is automatically and reliably replenished to each of the fluid bearing clearances, and is constantly filled with the lubricant. Even when the lubricant is used for a long time, the reliability is high and the durability is excellent.

Therefore, even if the amount of the injected lubricant is excessive or insufficient, there is little possibility that the lubricant will be scattered to the outside or the lubricant in the fluid bearing clearance will be depleted during a long-term use. In such a spindle motor of the present embodiment, the counter plate 16 and the base 11
Are fixed by an adhesive. This fixing method will be described with reference to FIGS. 1 and 2A.

The counter plate 16 is mounted in a hole 11 b provided at the center of the base 11. This counter plate 16 has a step on the outer periphery,
The outer peripheral portion is thinner than the other portions. That is, as can be seen from FIGS. 1 and 2A, the counter plate 16 is a plate-like member having a two-stage structure having a large outer diameter on the upper surface side and a smaller outer diameter on the lower surface side. The vertical cross-sectional shape of 16 is substantially convex. In the following description, a portion having a large outer diameter on the upper surface is referred to as a "large diameter portion", and a portion having a small outer diameter on the lower surface is referred to as a "small diameter portion".

Since the counter plate 16 has the above-described structure, when the counter plate 16 is mounted on the base 11, the adhesive pool 28 formed of an annular groove is formed in the center hole of the base 11. 11b and the outer peripheral surface 16a of the small diameter portion of the counter plate 16
The adhesive reservoir 28 is arranged on the lower surface side of the counter plate 16 adjacent to the fixed portion (joining portion).

As shown in FIG. 2A, the outer diameter of the large diameter portion is smaller than the diameter of the hole 11b.
When the counter plate 16 is attached to the base 11, a gap 30A is formed between the inner peripheral surface of the hole 11b and the outer peripheral surface 16b of the large diameter portion of the counter plate 16. Further, since the concave portion 16 c is provided at the outermost peripheral portion of the upper surface of the counter plate 16, a gap 30 B is formed between the bottom surface 11 c of the hole 11 b and the upper surface of the counter plate 16.

The gaps 30A and 30B communicate with the adhesive pool 28. When the adhesive A is injected into the adhesive pool 28, the adhesive A is filled in the order of the gap 30A and the gap 30B. Clearances 30A and 30B like this
Is provided, a large bonding area is secured, so that the fixing between the base 11 and the counter plate 16 is strengthened, and the fixing part is sealed by the adhesive A. After the adhesive A is filled, 70 to 100
C. to completely cure the adhesive A by heating to
It is preferable to secure the fixing strength.

Since a part of the upper surface of the counter plate 16 is in contact with the bottom surface 11c of the hole 11b, the counter plate 16 is disposed in the hole 11b in a horizontal and stable posture. Therefore, a portion 16 d of the upper surface of the counter plate 16 that is in contact with the bottom surface 11 c of the hole 11 b has a function as a guide surface of the counter plate 16.

This guide surface (the portion 16 of the upper surface of the counter plate 16 which is in contact with the bottom surface 11c of the hole 11b)
d) and at least one of the bottom surface 11c of the hole 11b and the portion in contact with the guide surface is subjected to an oil-repellent treatment such as applying an oil-repellent agent (having the property of repelling a lubricant). Since the lubricant is repelled to the portion subjected to the oil-repellent treatment, the lubricant is prevented from entering the gap of the contact portion due to the capillary phenomenon. Therefore, the clearance 30A, 30
Even when the adhesive B is not sufficiently filled with the adhesive A, the lubricant filled in the spindle motor hardly flows out from the fixed portion.

In the present embodiment, the clearance 30
Although A and 30B are formed, the gaps 30A and 30B may be formed by forming the base 11 in the following shape. That is, the outer diameter of the large-diameter portion is made equal to the diameter of the hole 11b, and a recess is formed in a portion of the inner peripheral surface of the hole 11b facing the outer peripheral surface 16b of the large-diameter portion, thereby forming the gap 30A. Also, instead of providing the concave portion 16c at the outermost peripheral portion of the upper surface of the counter plate 16,
By providing a recess in the bottom surface 11c of
B may be formed. Alternatively, counter plate 1
The gaps 30A and 30B may be formed by forming both the base 6 and the base 11 as described above.

Note that such clearances 30A, 30B
May be provided over the entire circumference of the counter plate 16 or may be provided on a part thereof. When the concave portion 16c is provided on the bottom surface 11c of the hole 11b instead of providing the concave portion 16c on the outermost peripheral portion of the upper surface of the counter plate 16, the counter plate 1
6 is the counter plate 1
6 has a function as a guide surface.

As described above, since the base 11 and the counter plate 16 are fixed by the adhesive A, the base 11 and the counter plate 16 are fixed as in the case of fixing by caulking.
No load is applied to the base 11 and the base 11 and the counter plate 16 are not deformed. Therefore, the problem that the thrust bearing surface 16s formed on the upper surface of the counter plate 16 is deformed and the flatness of the thrust bearing surface 16s is reduced does not occur.

The base 11 and the counter plate 1
6 is filled with the adhesive A and sealed with the adhesive A, so that the lubricant filled in the spindle motor flows out of the fixed portion during the rotation of the spindle motor. There is little fear. When the adhesive pool 28 is provided as described above, the adhesive A can be easily filled into the fixed portion, and the adhesive A diffuses to the surroundings during the heating and curing of the adhesive A. Can be prevented. Further, the sealing of the fixed portion with the adhesive A is more complete, and the prevention of the lubricant from flowing out from the fixed portion can be further improved. Adhesive pool 28
When the sealing is performed with the adhesive A without providing the adhesive, the adhesive A does not completely penetrate into the fixed portion, and the outflow prevention of the lubricant may be incomplete.

It is to be noted that the type of the adhesive A can provide sufficient fixing strength, and if the fixing portion can be sealed to prevent the lubricant filled in the spindle motor from flowing out, There is no particular limitation. For example, an epoxy-based adhesive, an anaerobic adhesive, an ultraviolet-curable adhesive, or an adhesive in which a plurality of these are used in combination is used.

In the present embodiment, the adhesive reservoir 28 is provided on the outer periphery of the counter plate 16.
If the fixed portion can be sealed with the adhesive A filled in the adhesive pool 28, the fixed portion may be provided on the inner peripheral surface of the hole 11b at the center of the base 11 or on the outer periphery of the counter plate 16. It may be provided continuously on both the portion and the inner peripheral surface portion of the hole 11b.

The counter plate 1 made of an adhesive
It is preferable to use a set screw in combination with the fixing of the base 6 and the base 11 because the fixing strength can be further improved. FIG. 2 (b)
FIG. 4 is an enlarged cross-sectional view showing a fixed portion when an adhesive and a set screw are used together for fixing the base 11 and the counter plate 16. The outer peripheral portion of the large diameter portion of the counter plate 16 and the bottom surface 11 of the hole 11b of the base 11
The counter plate 16 is screwed to the base 11 by providing a plurality of screw holes in c and screwing a set screw 31 into the screw hole. The head of the set screw 31 is housed in the adhesive reservoir 28.

Since the fixing between the base 11 and the counter plate 16 is performed by using both the bonding and the screwing, the bonding strength can be remarkably improved as compared with the case where only the bonding is performed. Also, base 11 and counter plate 1
6 is filled with the adhesive A and sealed, so that the sealing effect of the lubricant is not impaired. Further, since the periphery of the set screw 31 is covered with the adhesive A, the set screw 31 is prevented from being loosened due to external vibration or impact.

Note that a pin may be used instead of the set screw 31. If a pin is used, the gap formed between the pin and the hole into which the pin is inserted is also filled with the adhesive, so the bonding area increases and the bonding strength is significantly higher than when only the pin is used. Can be improved. Also,
When an axial load is applied to the counter plate 16, only the shearing force acts on the adhesive filled in the gap formed between the hole into which the pin is inserted and the pin. This is the reason why the fixing strength is remarkably improved as compared with the case where 11 is fixed only by bonding (a peeling force is exerted when an axial load is applied).

Also, unlike the case of screwing, it is not necessary to tapped the hole into which the pin is inserted, so that the hole can be easily formed. This is particularly advantageous when it is necessary to design a small hole diameter due to dimensional restrictions. However, even if the hole for inserting the pin is tapped,
No problem. Further, a set screw 31 may be inserted into a hole where tapping is not performed, instead of the pin.

Further, it is not always necessary to use the same adhesive for filling the gaps 30A and 30B and the adhesive filling the gap formed between the pin for inserting the pin and the pin. Therefore, any one of the adhesives may be used as the sealant. However, considering the work efficiency, it is desirable to use the same adhesive. The material and shape of the set screw 31 and the pin, and the shape of the hole into which the set screw 31 and the pin are inserted are not particularly limited, and may be appropriately changed as needed if the object of the present invention can be achieved. It is possible.

The present embodiment is an example of the present invention, and the present invention is not limited to these embodiments. For example, a spindle motor is
A shaft rotation type or a shaft fixed-sleeve rotation type may be used. Also, a thrust plate 15 provided on the shaft 13
Is not limited to the shaft end but may be near the shaft end.

Further, the structure of the fluid bearing, the structure of the exhaust hole 23, the lubricant reservoir 22, the lubricant supply passage 25, the pattern of the dynamic pressure generating groove, the detailed structure of the spindle motor, and the like are limited to the present embodiment. However, if the object of the present invention can be achieved, it can be appropriately changed as needed. For example, the tapered surface 24 forming the lubricant reservoir 22 may have various curved surfaces as long as the lubricant reservoir 22 has a shape in which the clearance gradually narrows toward the fluid bearing clearance. Further, the groove for generating dynamic pressure is not limited to a herringbone shape or a spiral shape, but may be any groove pattern as long as it functions as a hydrodynamic bearing. Also,
Etching, electrolytic etching, plastic working, cutting, laser processing, ion beam processing, shot blasting, and the like can be applied to the groove according to the material and required accuracy.

Further, the material of the members constituting the spindle motor such as the shaft 13 and the sleeve 12 is not particularly limited, and metals (stainless steel, copper alloy, Materials such as aluminum alloys), sintered metals, sintered oil-impregnated metals, plastics, and ceramics 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.

When the shaft 13 and the sleeve 12 are made of a combination of copper alloys having different hardnesses, for example, the shaft 13 is made of a combination of high hardness beryllium copper or aluminum bronze, and the sleeve 12 is made of lead bronze or phosphor bronze. The dynamics and the cutting workability can be satisfied. In this case, it is preferable to provide a groove for generating a fluid shunt on the fluid bearing surface of lead bronze or phosphor bronze having a low hardness because the mating member is less likely to be damaged.

Further, the material of the base 11 is not particularly limited, and may be an aluminum die cast, an aluminum forged product,
In addition to metals such as magnesium alloys, it is also possible to use plastics which are usually difficult to caulk. Further, in the present embodiment, the spindle motor has been described as an example of the hydrodynamic bearing device, but the present invention can be applied to other various hydrodynamic bearing devices.

[0087]

As described above, in the hydrodynamic bearing device according to the present invention, the base and the mating member are fixed with the adhesive.
The base and the mating member are not deformed as in the case of fixing by caulking. Also, since the fixed portion between the base and the mating member is sealed with the adhesive, the lubricant filled in the fluid bearing device flows out of the fixed portion during rotation of the fluid bearing device. There is little possibility that it will occur.

[Brief description of the drawings]

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

FIG. 2 is an enlarged view of a main part of the spindle motor of FIG. 1;

FIG. 3 is a sectional view of a spindle motor under development.

[Explanation of symbols]

 Reference Signs List 11 base 12 sleeve 13 shaft 15 thrust plate 16 counter plate 28 adhesive reservoir 30A, 30B clearance 31 set screw A adhesive R radial fluid bearing S thrust fluid bearing

Continued on the front page (72) Inventor Ikuki Sakatani 1-5-50 Kugenuma Shinmei, Fujisawa City, Kanagawa Prefecture Inside NSK Ltd. In-house F term (reference) 3J011 AA12 BA06 BA08 CA02 DA02 JA02 KA02 KA03 MA24 SB03 5D109 BB03 BB12 BB18 BB21 BB22 5H605 AA08 BB05 BB10 BB19 CC01 CC02 CC03 CC04 DD05 EA02 EB06 EB21 FF03 GG07 BB07 BB07 BB03 JJ04 JJ05 JJ06 KK00

Claims (1)

[Claims] 1. A shaft having a flange at one end, a sleeve opposed to the shaft via a fluid bearing clearance of a radial fluid bearing, and a fluid bearing clearance of a thrust fluid bearing on one plane of the flange. In a hydrodynamic bearing device comprising an opposing counterpart member and a base to which the counterpart member is attached, a guide surface for arranging the counterpart member at a predetermined position on the base includes at least one of the counterpart member and the base. And a gap is provided between the mating member and the base, and an adhesive for fixing the mating member and the base is filled in the gap.