JP2002122134A - Fluid bearing device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A fluid bearing having excellent moment resistance, which is important for achieving excellent portability, low power consumption, high reliability, and extremely small influence of bubbles remaining inside the bearing. Provide equipment. SOLUTION: A flange portion 1 is provided at both ends or in the vicinity thereof.
Shafts 13 and 14, and a fluid bearing clearance C
And a sleeve 12 opposed to the shaft 13, the flange portions 15, 15 are formed in a substantially conical shape, and the convex direction of the conical surface 15 f is directed toward the center of the shaft 13.
And a lubricant reservoir 2 for holding the lubricant.
2 is provided in communication with the fluid bearing clearance C, and the lubricant pool 2 is provided.
2 has a shape in which the clearance gradually narrows toward the fluid bearing clearance C. Further, an exhaust hole 23 communicating with the outside air is provided in a portion of the lubricant reservoir 22 where the clearance is wider.

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 As a conventional hydrodynamic bearing device used for such applications, there is, for example, a spindle motor for HDD provided with a thrust hydrodynamic bearing and a radial hydrodynamic bearing as shown in FIG. In this device, a cylindrical housing 100 having a bottom plate 100a is inserted inside a cylindrical portion 101a erected on a base 101, and these are integrally fixed. A cylindrical sleeve 102 is inserted into the inner peripheral surface of the housing 100.
They are 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 flange portion 105 is integrally formed at the lower end of the shaft 103. Both planes of the flange portion 105
Thrust receiving surfaces 105s, 105s of thrust fluid bearing S
It has been. And the thrust receiving surface 105s on the upper surface side
, The lower end surface of the sleeve 102, which is a mating member, faces through a thrust fluid bearing clearance, and the lower end surface of the sleeve 102 is the thrust bearing surface 102s of the thrust fluid bearing S.

[0004] The upper surface of the bottom plate 100a of the housing 100, which is a mating member, faces the lower thrust receiving surface 105s via a thrust fluid bearing clearance, and the upper surface of the bottom plate 100a faces the thrust bearing of the thrust fluid bearing S. The surface is 100 s. And the above-mentioned thrust receiving surface 1
05s, 105s and thrust bearing surface 102s, 100s
And at least one of them has 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 102r, 102r are opposed to the radial receiving surfaces 103r, 103r via a radial fluid bearing clearance.
Are formed. In addition, at least one of the radial receiving surface 103r and the radial bearing surface 102r has a herringbone-shaped or spiral-shaped groove 107, 10 for generating dynamic pressure.
7 to form radial fluid bearings R, R.

In order to reduce the torque of the spindle motor, the inner peripheral surface of the sleeve 102 (the outer peripheral surface of the shaft 103 or the inner peripheral surface of the sleeve 102 may be interposed between the upper and lower radial fluid bearings R, R). Surface and the outer peripheral surface of the shaft 103).
Is provided. A stator 108 is fixed to the outer peripheral surface of the cylindrical portion 101a, and a driving motor M is formed to face 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 driven to rotate by the drive motor M.

When the shaft 103 rotates, a small amount of lubricant filled in the fluid bearing clearances of the fluid bearings S and R is pumped by the pumping action of the dynamic pressure generating grooves of the thrust fluid bearing S and the radial fluid bearing R. When pressure is generated, the shaft 103 comes into non-contact with the inner peripheral surface of the sleeve 102 and the upper surface of the bottom plate 100a and is supported.

[0008]

In recent years, HDDs have been required to have higher recording densities, and track widths for recording information have become narrower. Therefore, adoption of fluid bearings having high rotational accuracy has been studied. I have. Furthermore, HDDs mounted on portable devices such as notebook personal computers are required to be thinner, and a hydrodynamic bearing device with low power consumption, excellent portability, and high reliability is required.

However, in the conventional hydrodynamic bearing device (spindle motor) as described above, if the height of the device is reduced for thinning, the bearing span of the radial hydrodynamic bearing R becomes small, and the proof stress against moment load (hereinafter, referred to as “spindle motor”) is obtained. Moment proof stress) is weakened. Therefore, when the device is swung by transportation or the like, the bearing portions may come into contact with each other and be damaged. In other words, when the bearing is carried while rotating, the gyro moment acts on the rotating body when swinging, and a large moment load acts on the bearing, so that the bearing surfaces may come into contact with each other and be damaged.

On the other hand, if the bearing span is small, it is difficult to reduce the bearing torque while securing the required moment resistance, which is an obstacle to practical use from the viewpoint of power consumption. Further, since the conventional spindle motor is provided with substantially four hydrodynamic bearings in total as described above (two thrust fluid bearings S and two radial fluid bearings R are provided), The bearing torque is larger than that of a spindle motor with two ball bearings. Especially when the ambient temperature is low, the viscosity of the lubricant increases, so an increase in the bearing torque cannot be avoided. Was an obstacle.

When the spindle motor is filled with a lubricant, the lubricant is usually filled during the assembly of the spindle motor. That is, the housing 10
An appropriate amount of lubricant is previously injected on the bottom plate 100a of No. 0, and the shaft 103 is inserted therein. After that, the sleeve 102 is pressed into the inner peripheral surface of the housing 100 to assemble the spindle motor.

Therefore, since the lubrication of the fluid bearing is performed only by the clearance of the fluid bearing and a very small amount of lubricant held in the vicinity thereof, in a long-term use, the fluid bearing clearance is caused by evaporation and scattering of the lubricant. There is a problem that the lubricant in the inside gradually decreases and is liable to be depleted, and eventually there is a risk of seizure, and the reliability of the hydrodynamic bearing device is poor.

Further, when the lubricant is filled, air bubbles tend to remain in the center hole 111 and the relief groove 110 necessary for machining the shaft. If air bubbles remain in the clearance of the fluid bearing or in the space near the bearing, there is a problem that the rotation of the bearing is likely to be unstable (NRRO, which is the fluctuation of the rotation asynchronous component during rotation, increases).

Accordingly, the present invention solves the problems of the conventional hydrodynamic bearing device as described above, and is excellent in moment resistance, which is important for realizing excellent portability, with low power consumption and reliability. It is an object of the present invention to provide a hydrodynamic bearing device which is high and has an extremely small influence of bubbles remaining inside the bearing.

[0015]

In order to solve the above-mentioned problems, the present invention has the following arrangement. That is, a hydrodynamic bearing device of the present invention is a hydrodynamic bearing device including a shaft having a flange portion at both ends or in the vicinity thereof, and a mating member opposed to the shaft via a fluid bearing clearance, wherein the flange portion is provided. A substantially conical or substantially hemispherical shape, and the convex direction of the conical surface or spherical surface is disposed on the shaft so as to face the center of the shaft, and a lubricant reservoir holding lubricant is communicated with the fluid bearing clearance. Wherein the lubricant reservoir has a shape in which the clearance gradually narrows toward the fluid bearing clearance, and further, an exhaust hole communicating with the outside air is provided in a portion where the clearance of the lubricant reservoir is wider. And

In a hydrodynamic bearing device comprising a shaft having a flange at both ends or in the vicinity thereof and a mating member opposed to the shaft via a fluid bearing clearance, the flange is substantially conical or substantially conical. A hemispherical shape, the conical surface or spherical surface of which is disposed on the shaft with the convex direction facing the center of the shaft, a lubricant reservoir for holding a lubricant, and the fluid bearing provided at one end of the lubricant reservoir. A lubricant supply path communicating with the gap, and the lubricant reservoir is formed such that the clearance gradually narrows toward the lubricant supply path,
Further, the fluid bearing device may be characterized in that an exhaust hole communicating with outside air is provided in a portion where the clearance of the lubricant reservoir is wider.

Since the flange portion is formed as a substantially conical or substantially hemispherical member and the conical surface or spherical surface is disposed on the shaft with the center of the shaft facing the center of the shaft, a bearing surface (the flange portion and the The surface facing the opposing member) is disposed obliquely to the axial direction. A hydrodynamic bearing device having such a hydrodynamic bearing can have a large bearing span even when the height of the hydrodynamic bearing is limited, so that the hydrodynamic bearing device is excellent in moment resistance and the number of hydrodynamic bearings is reduced. Can be greatly reduced (for example, halved). Therefore, such a hydrodynamic bearing device has low bearing torque and low power consumption.

Further, when the shape of the lubricant reservoir is tapered as described above, the lubricant injected into the hydrodynamic bearing device is held in the lubricant reservoir by surface tension, and the lubricant reservoir is formed. From the fluid bearing clearance. Therefore, even if the hydrodynamic bearing device is used for a long period of time, the possibility that the lubricant in the hydrodynamic bearing clearance is depleted is small, and thus the hydrodynamic bearing device has high reliability.

Even if air bubbles remain inside the hydrodynamic bearing device (the space around the hydrodynamic bearing clearance or the vicinity thereof), lubricant collects in a narrower portion of the lubricant pool due to surface tension, and the air bubbles are removed by the lubrication. The air bubbles are discharged to the outside air from the exhaust holes because the air bubbles are collected on a wider side of the agent pool. Therefore, the rotation of the bearing is less likely to be unstable.

[0020]

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. (First Embodiment) FIG. 1 is a sectional view of a spindle motor for an HDD, which is a first embodiment of a hydrodynamic bearing device according to the present invention.

First, the structure of the spindle motor will be described. The spindle motor includes a shaft 13 to which a hub 14 is fixed, and a sleeve 12 through which the shaft 13 is inserted. The shaft 13 and the sleeve 12 are opposed to each other via a fluid bearing clearance C. That is, the fluid bearing F is interposed between the shaft 13 and the sleeve 12, and the fluid bearing F has both functions of a radial fluid bearing and a thrust fluid bearing. The sleeve 12 corresponds to a mating member which is a constituent element 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 fluid bearing F
Are rotatably supported on the sleeve 12.

Next, the structure of the spindle motor of this embodiment as described above will be described in more detail. Base 11
A cylindrical sleeve 12 is inserted inside a cylindrical portion 11a erected at the center of the body, and both are integrally fixed. A shaft 13 is rotatably inserted into the sleeve 12.

At both ends of the shaft 13, flange portions 1 are provided.
5, 15 are provided. This flange portion 15, 15
Has a substantially conical shape, and is provided on the shaft 13 so that the convex direction of the conical surface 15 f faces the center of the shaft 13.
That is, the center axis of the cone is coaxial with the axis 13, and the apex of the cone is provided toward the center of the axis 13. Therefore, the shaft 13 has a cylindrical shape with a small diameter at the center, and has a shape in which the diameter gradually increases from both ends toward the upper and lower ends.

The lower flange portion 15 is formed integrally with the shaft 13, and the upper flange portion 15 is fixed by a conventional fixing method such as screwing, press fitting, bonding, welding, or the like.
It is fixed to the shaft 13. However, both flange parts 1
5, 15 may be fixedly attached. The upper end 13a of the shaft 13 having such a shape is cylindrical, and the upper end 13a is press-fitted into a hole provided at the center of a shallow inverted cup-shaped hub 14 so that the shaft 13 and the hub 14 are formed. And are integrally fixed.

The inner peripheral surface of the sleeve 12 into which the shaft 13 is inserted has a shape corresponding to the shaft 13 having the above-described shape, and has a shape facing the shaft 13 via the fluid bearing clearance C. Has become. That is, the portion of the inner peripheral surface of the sleeve 12 facing the flange portion 15 (the upper and lower portions of the sleeve 12) is a slope 12f facing the conical surface 15f of the flange portion 15 in parallel. The part facing the central part of the shaft 13 (the small cylindrical part)
It is substantially parallel to the shaft 13 and faces the same. However, axis 1
A lubricant reservoir 22 is provided in a portion facing the central portion of 3, and is not strictly parallel to the axis 13.
The detailed structure of this part will be described later.

As described above, the inner diameter of the upper and lower portions of the sleeve 12 is large, the inner diameter is gradually reduced from the upper portion to the central portion, and the central portion is substantially parallel to the shaft 13 (substantially trapezoidal cross section). ). Both flanges 1
5, 15 conical surface 15f and sleeve 12 opposed thereto
Of the conical surface 15f and the inclined surface 12f, for example, a substantially herringbone-shaped (or spiral-shaped) dynamic pressure generating groove (not shown). ) To constitute the fluid bearing F.

Since the fluid bearing surface constituting the fluid bearing F is arranged obliquely to the axial direction, the fluid bearing F functions as both a radial fluid bearing and a thrust fluid bearing. Has both. With a spindle motor equipped with such a fluid bearing, a large bearing span can be taken even when the device height is restricted, so that the spindle motor is excellent in moment resistance and the number of fluid bearings is smaller than in the past. Significantly reduced (eg, halved). Therefore, such a spindle motor has low bearing torque and low power consumption.

In order to secure the radial load capacity required for practical use, the angle θ of the conical surface 15f with respect to the axis 13 is preferably 50 ° or less, more preferably 45 ° or less, and further preferably 40 ° or less. ° or less. On the other hand, if the angle θ of the conical surface 15f is less than 25 °, the angle θ of the conical surface 15f is preferably 25 to 40 ° because the axial dimension becomes too long and the starting torque becomes too large.

It is preferable that the dynamic pressure generating grooves of the fluid bearing F have an asymmetric groove pattern in which pressure acts inwardly for the following reasons. That is, a pressure is applied to push the lubricant from the outside to the opposite side with the rotation of the shaft 13 (pump-in), so that the lubrication in the fluid bearing clearance C of the fluid bearing F is caused by the centrifugal force caused by the rotation of the shaft 13. The agent is prevented from scattering to the outside.

This will be described in more detail. The dynamic pressure generating grooves are a plurality of substantially V-shaped grooves arranged at predetermined intervals along the circumferential direction of the conical surface 15f of the flange portion 15. It is configured. Then, the grooves for generating the dynamic pressure are formed in a groove pattern in which a pressure for pushing the lubricant in acts. In this embodiment, the inside and the inside are defined as the shaft 13.
Means radially inward around
Similarly, it means radially outward.

The method of forming the dynamic pressure generating groove on the fluid bearing surface (at least one of the conical surface 15f and the inclined surface 12f) is not particularly limited, and examples thereof include plastic working, cutting, and etching. Can be The coining process, which is a plastic process, is a method of stamping the groove for generating dynamic pressure by pressing the mold against the flange portion 15 or the sleeve 12 using a press or the like, so that it is superior in mass productivity as compared with the etching process. And low cost.

In particular, when a copper alloy having a low hardness is used for the sleeve 12, plastic working by coining is easy, so that there is an advantage that mass productivity is excellent. Since the flange portion 15 needs strength, it is preferable that the hardness is high. A counter plate 16 is provided at the center of the base 11.
Is attached, and covers the opening of the cylindrical portion 11a. The counter plate 16 is screwed, press-fitted,
It is attached to the base 11 by a conventional fixing method such as bonding or welding. This counter plate 16
Is provided to prevent foreign matter from entering the fluid bearing clearance C, but may be omitted.

Next, the lubricant reservoir 22 will be described. An annular clearance is interposed between the central portion (small-diameter cylindrical portion) of the shaft 13 and a portion of the inner peripheral surface of the sleeve 12 facing the central portion, and the annular clearance forms the lubricant reservoir 22. Has formed. The inner peripheral surface of the sleeve 12 forming the inner surface of the lubricant reservoir 22 is formed as a tapered surface 24 tapering from the center toward the upper and lower ends (fluid bearing clearance of the fluid bearing F). The reservoir 22 has a tapered shape in which the center is the widest and the clearance gradually narrows toward the upper and lower ends.

However, the tapered surface 24 is not always formed on the inner peripheral surface side of the sleeve 12 and may be formed on the outer peripheral surface side of the shaft 13 (the small cylindrical portion). It may be formed on both the peripheral surface side and the outer peripheral surface side of the shaft 13. Further, at both upper and lower ends of the lubricant reservoir 22, a lubricant supply passage 25 which is open toward the fluid bearing clearance C of the fluid bearing F is provided. And
The opening of the lubricant supply passage 25 communicating with the fluid bearing clearance C of the fluid bearing F is substantially equal to or slightly larger than the fluid bearing clearance C, and the lubricant is formed by capillary action based on surface tension. Is easily introduced from the lubricant supply passage 25 into the fluid bearing clearance C.

In the present embodiment, the lubricant reservoir 22 is provided on the entire inner circumferential surface of the sleeve 12 in the circumferential direction (that is, the lubricant reservoir 22 has an annular clearance shape).
However, a slit shape may be provided at one or a plurality of locations on the inner peripheral surface of the sleeve 12 (that is, the other portions are
There is no tapered clearance, and the inner peripheral surface of the sleeve 12 and the outer peripheral surface of the shaft 13 are parallel.

In this embodiment, the sleeve 1
2 is a tapered surface 24, and a part of the tapered surface 24 of the lubricant reservoir 22 is a lubricant supply passage 25.
The tapered surface 24 is directly connected to the fluid bearing clearance C. However, the center of the inner peripheral surface of the sleeve 12 in the vertical direction is a tapered surface 24, and both upper and lower ends are surfaces parallel to the outer peripheral surface of the shaft 13, and an annular clearance formed by these parallel surfaces defines the lubricant supply passage 25. It is good also as a structure which comprises.

At the center of the lubricant reservoir 22 in the vertical direction (the portion having the widest clearance), an exhaust hole 23 communicating with the outside air is provided.
Is open. The exhaust hole 23 extends horizontally from the inner peripheral surface of the sleeve 12 (the vertical center of the lubricant reservoir 22),
It is open on the outer peripheral surface of the sleeve 12. The exhaust hole 23 may be provided in the shaft 13 instead of the sleeve 12. That is, the shaft 13 may be provided so as to extend horizontally from the outer peripheral surface (the vertical center of the lubricant reservoir 22), bend upward in the middle, and open at the upper end surface of the shaft 13.

Next, a method of injecting a lubricant into the spindle motor will be described. The injection of the lubricant into the spindle motor is performed from the exhaust hole 23 using a dispenser or the like. That is, when a lubricant is injected into the lubricant reservoir 22 by inserting a dispenser injection needle or the like into the exhaust hole 23, the lubricant is charged by the surface tension.
The bubbles collect in the narrower gap, and in the wider gap.
Then, since the lubricant gradually spreads and fills the fluid bearing clearance C, there is little possibility that air bubbles are trapped inside the device (in the fluid bearing clearance C) when the lubricant is injected.

Therefore, even if the lubricant is injected in the atmosphere, entrapment of air bubbles can be prevented. Of course, the lubricant may be injected in a vacuum, or after the injection, the spindle motor may be put in a vacuum chamber and deaerated. Further, in order to more reliably deaerate bubbles, a lubricant which has been previously vacuum degassed may be used, if necessary. If the inner peripheral surface of the exhaust hole 23 is subjected to an oil-repellent treatment such as applying an oil-repellent (having a property of repelling a lubricant), the lubricant is repelled to the portion subjected to the oil-repellent treatment. Thus, it is possible to effectively prevent the lubricant from flowing out of the exhaust hole 23 to the outside when the spindle motor is carried or the like.

The injected lubricant fills each of the fluid bearing clearances C of the fluid bearing F by the surface tension, and excess lubricant is accumulated in the lubricant reservoir 22 via the lubricant supply passage 25 and is based on the surface tension. Tapered surface 24 due to capillary action
Is held. 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 is reduced toward the upper and lower lubricant supply passages 25 by 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 center in the vertical direction of the lubricant reservoir 22 (a wide gap) are discharged to the outside through the exhaust holes 23.

Further, on the outermost sides of the fluid bearings F, F,
A taper seal 27 is provided to prevent the lubricant from flowing out and scattering from the fluid bearing clearance C of the fluid bearing F by surface tension and centrifugal force. That is, the substantially conical flange portions 15 and 15 have a shape in which the diameter gradually increases from the center to the end of the shaft 13, while the outermost portion gradually decreases in diameter, and Is tapered so that the clearance gradually narrows toward the fluid bearing clearance C.

By providing such a tapered clearance in communication with the fluid bearing clearance C, the lubricant in the fluid bearing clearance C is less likely to flow out and scatter. That is, the lubricant is collected toward the fluid bearing clearance C by the surface tension when the spindle motor is at rest and by the centrifugal force when the spindle motor is rotating.

The drive motor M drives the hub 14 and the shaft 1 for mounting a magnetic disk (not shown), which is a rotating body, on the outer periphery.
3 is integrally rotated, a dynamic pressure is generated in the lubricant filled in the fluid bearing clearances C, C by the pumping action of the respective dynamic pressure generating grooves of the fluid bearings F, F, and the shaft 1
3 is not in contact with the sleeve 12 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.

When a centrifugal force acts upon the rotation, the lubricant in the lubricant reservoir 22 rises and descends along the tapered surface 24 and reaches and is held by the lubricant supply passage 25 having a narrow clearance. Then, the lubricant is reliably supplied from the lubricant supply passage 25 to the fluid bearing clearance C by capillary action. Further, even if bubbles remain in the fluid bearing clearance C, the bubbles are immediately discharged to the outside air via the exhaust holes 23 opened in the lubricant reservoir 22.

If the lubricant retained in the fluid bearing clearance C gradually evaporates or scatters and runs short over a long period of time, the lubricant pool 22 will be filled in the lubricant reservoir 22 by capillary action based on surface tension. The retained 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 C. That is, as the amount of the lubricant in the fluid bearing clearance C decreases, the lubricant is sucked by the capillary bearing via the lubricant supply passage 25 into the fluid bearing clearance C having a small clearance, and the surface tension of the tapered surface 24 of the lubricant reservoir 22 decreases. Stable at equilibrium position. 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 removed. Is separated and discharged to the larger gap. Therefore, each fluid bearing clearance C is automatically and reliably replenished with a lubricant having no bubbles, communicates with the lubricant reservoir 22, and is always filled with the lubricant. High 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 the fluid bearing clearance C is depleted during a long-term use is small. In the spindle motor of the present embodiment, the sleeve 12, the shaft 13, and the flange 1
The portion (fluid bearing portion) composed of 5 and 15 may have an integrated unit structure as shown in FIG. Since such a fluid bearing unit can be incorporated into the spindle motor at one time, manufacture and assembly of the spindle motor are easy.

Also, since the fluid bearing unit is manufactured in advance by a bearing maker (assembly and injection of lubricant) and can be completed in the spindle motor by the spindle motor maker, there is an advantage that the production can be easily shared. is there. In the example of FIG. 2, the conical surfaces (fluid bearing surfaces) 15f, 15f of the flange portions 15, 15 are crowned, the generatrix shape is slightly convex, and the conical surface 15f is a convex spherical surface. . With such a shape of the fluid bearing surface, the area where the opposed fluid bearing surfaces are in contact with each other at the time of startup can be reduced, so that the startup torque of the fluid bearing can be reduced. The crowning may be applied to the slope 12f of the sleeve 12, or to both the conical surface 15f and the slope 12f.

(Second Embodiment) FIG. 3 is a sectional view of a spindle motor for HDD which is a second embodiment of the hydrodynamic bearing device according to the present invention. The structure of the spindle motor of this embodiment is almost the same as that of the first embodiment described above, and therefore only different parts will be described, and description of the same parts will be omitted. In FIG. 3, the same or corresponding parts as those in FIG. 1 are denoted by the same reference numerals as those in FIG.

The lubricant reservoir 22 is formed by a clearance interposed between the lower end surface of the shaft 13 (the lower surface of the lower flange portion 15) and the upper surface of the counter plate 16. Counter plate 1 forming the inner surface of lubricant reservoir 22
6 has an upper surface extending from the center to the outer edge (lower fluid bearing F).
Is formed in a tapered surface 24 which is tapered toward the fluid bearing clearance C).
The center portion is the widest and has a tapered shape in which the clearance gradually decreases toward the outer edge.

However, the tapered surface 24 is not always formed on the upper surface of the counter plate 16 and the shaft 13
May be formed on both the upper surface of the counter plate 16 and the lower surface of the shaft 13. Unlike the first embodiment, the lubricant reservoir 22 is
, The central portion of the inner peripheral surface of the sleeve 12 (the portion facing the small-diameter cylindrical portion of the shaft 13)
Are completely parallel to the axis 13.

A lubricant supply passage 25 is provided at the outer edge of the lubricant reservoir 22 and opens toward the fluid bearing clearance C of the lower fluid bearing F. In the present embodiment, the lower end of the lower flange portion 15 has a cylindrical shape in order to facilitate the measurement of the largest diameter portion (lower end portion) of the lower flange portion 15. This columnar part 1
5a and the inner peripheral surface of the cylindrical portion 11a are parallel to each other, and an annular clearance formed between the outer peripheral surface of the cylindrical portion 15a and the inner peripheral surface of the cylindrical portion 11a forms the lubricant supply passage 25. Make up. However, the annular clearance may be omitted, and the lubricant reservoir 22 may directly communicate with the fluid bearing clearance C.

An exhaust hole 23 communicating with the outside air is opened at the center of the lubricant reservoir 22 (the portion having the widest clearance). The exhaust hole 23 extends vertically from the lower end surface of the shaft 13,
The shaft 13 is open at the upper end surface. In addition, this exhaust hole 23
May be provided on the counter plate 16 instead of the shaft 13. That is, at the center of the counter plate 16,
An exhaust hole 23 penetrating vertically through the counter plate 16 may be provided.

Next, a method of injecting a lubricant into the spindle motor will be described. Exhaust hole 2 passing through shaft 13
When the lubricant is injected from 3, the lubricant collects in the narrower space of the lubricant reservoir 22 and the bubbles in the wider space due to the surface tension. The lubricant is applied to the lower fluid bearing clearance C and the outer peripheral surface of the shaft 13 (the central small-diameter cylindrical portion).
(The clearance portion) between the fluid bearing and the inner peripheral surface of the sleeve 12, and the upper fluid bearing clearance C is filled in this order.

The air bubbles collected at the center of the lubricant reservoir 22 (a wide area of the clearance) are discharged to the outside through the exhaust holes 23. As described above, in the spindle motor of the present embodiment, the operation of injecting the lubricant is easy, and it is difficult for air bubbles to be trapped in the fluid bearing clearance C and the clearance of the relief portion. (Third Embodiment) FIG. 4 is a sectional view of an HDD spindle motor which is a third embodiment of the hydrodynamic bearing device according to the present invention. The structure of the spindle motor of this embodiment is almost the same as that of the first embodiment described above, and therefore only different parts will be described, and description of the same parts will be omitted. In FIG. 4, the same or corresponding portions as in FIG. 1 are denoted by the same reference numerals as in FIG.

The spindle motor of this embodiment has a shaft 13 having a structure in which a small-diameter cylindrical portion at the center of the shaft 13 in the first embodiment is omitted, and upper and lower flange portions 15, 15 are directly connected. Thus, this is an example in which the height of the apparatus is reduced. The shaft 13 may be a hollow shaft or a solid shaft. A vertical surface 29 that is parallel to the axial direction is provided at the center in the vertical direction of the inner peripheral surface of the sleeve 12, and the smallest diameter portion at the center of the shaft 13 and its periphery (the upper and lower flange portions 15, 15 are connected). Near the boundary, hereinafter referred to as a connected portion). And
The clearance formed between the vertical surface 29 of the sleeve 12 and the connecting portion of the shaft 13 forms the lubricant reservoir 22.

The shaft 13 forming the inner surface of the lubricant reservoir 22
The outer peripheral surface of the connecting portion is provided with upper and lower flange portions 15, 1
5 is tapered toward the upper and lower ends (fluid bearing clearance C of the fluid bearing F) from the boundary where the lubrication reservoir 5 is connected, whereby the lubricant reservoir 22 has the widest center at the center and the clearance gradually increases toward the upper and lower ends. It has a tapered shape that becomes narrower.

A disk-like cover member 28 having a hole at the center is fixed to the upper and lower ends of the sleeve 12 by bonding, laser welding, or the like. Then, one plate surface of the cover member 28 is opposed to the end surface (the bottom surface of the cone) of the flange portion 15 via a clearance. The end surface of the flange portion 15 is a tapered surface, and the clearance formed between the cover member 28 and the end surface of the flange portion 15 gradually increases outward (the fluid bearing clearance C of the fluid bearing F). The shape is such that the clearance is narrow. The taper seal 27 is formed by such a clearance.

The tapered surface may be provided on the plate surface of the cover member 28, or may be provided on both the end surface of the flange portion 15 and the plate surface of the cover member 28. The operation and effect of the taper seal 27 are the same as in the first embodiment. Further, the tapered clearance constituting the taper seal 27 also has a function as a lubricant reservoir, and the lubricant reservoir 22 that can hold a small amount of lubricant is provided.
Assists the function of.

(Fourth Embodiment) FIG. 5 is a sectional view of a spindle motor for HDD which is a fourth embodiment of the hydrodynamic bearing device according to the present invention. First, the structure of the spindle motor according to the present embodiment will be described. The spindle motor of the present embodiment is different from the spindle motors of the first to third embodiments in that a shaft 13 is integrated with a base 11 and a sleeve 12 supported on a fixed shaft 13 thereof via a fluid bearing F. Is a method of rotating with the hub 14, that is, a spindle motor of a shaft fixed / sleeve rotating type.

However, description of the same parts as in the first embodiment will be omitted, and only different parts will be described. In FIG. 5, the same or corresponding parts as in FIG. 1 are denoted by the same reference numerals as in FIG. A counter plate 16 is fixed to the center of the base 11, and a shaft 13 is provided upright at the center of the counter plate 16.
Flanges 15, 15 are provided at both upper and lower ends of the shaft 13. The upper flange portion 15 is formed integrally with the shaft 13, and the lower flange portion 15 is formed integrally with the counter plate 16 and is fixed to the shaft 13 together with the counter plate 16.

The shaft 13 is rotatably inserted into a cylindrical sleeve 12. This sleeve 12 is press-fitted into the center of an inverted cup-shaped hub 14 on which a magnetic disk (not shown) is mounted on the outer periphery. Is fixed by the conventional fixing means. Center part (small diameter part) of shaft 13 and sleeve 1
An annular clearance is interposed between the inner peripheral surface of the inner peripheral surface 2 and a central portion in the vertical direction, and the annular clearance forms a lubricant reservoir 22. The inner peripheral surface of the sleeve 12 that forms one of the inner surfaces of the lubricant reservoir 22 is a vertical surface parallel to the axial direction, while the outer peripheral surface of the other shaft 13 is vertically moved from the center thereof (fluid of the fluid bearing F). The lubrication reservoir 22 has a tapered surface 24 which is tapered toward the bearing clearance C), whereby the lubricant reservoir 22 has the largest width at the center and gradually narrows up and down. .

However, the tapered surface 24 is not necessarily the shaft 13
Is not necessarily formed on the outer peripheral surface side, and may be formed on the inner peripheral surface side of the sleeve 12 or on both of them. Further, at both upper and lower ends of the lubricant reservoir 22, lubricant supply passages 25, 25 which are open toward the fluid bearing clearance C of the fluid bearing F are provided. In the present embodiment, the lubricant supply passage 25 is not formed in a tapered shape, but is formed by a parallel clearance. That is,
In the portion where the lubricant supply passage 25 is formed, the inner peripheral surface of the sleeve 12 and the outer peripheral surface of the shaft 13 are parallel.

However, even when the tapered lubricant supply passage 25 is provided as in the first to third embodiments (that is, the lubricant reservoir 22 directly communicates with the fluid bearing clearance C).
There is no problem at all, and there is no particular difference in the effect depending on the shape. An exhaust hole 23 communicating with the outside air is opened at the center of the lubricant reservoir 22 (the portion having the widest clearance).
The exhaust hole 23 extends horizontally from the outer peripheral surface of the shaft 13 (the center of the lubricant reservoir 22), bends downward in the middle, and opens at the lower end surface of the shaft 13. When the opening of the exhaust hole 23 is covered with the air-permeable filter 30 made of a porous member, it is possible to prevent foreign substances from entering the inside of the apparatus from the outside. The filter 30 may be provided so as to fill the inside of the exhaust hole 23.

Further, the lower fluid bearing F is provided with the same taper seal 27 as in the first embodiment. A disk-shaped cover member 28 having a hole at the center is fixed to the center of the hub 14 by bonding, laser welding, or the like. Then, the plate surface (lower surface) of the cover member 28
Is opposed to the upper end surface (the bottom surface of the cone) of the upper flange portion 15 via a clearance. The plate surface of the cover member 28 is tapered, and the cover member 28 and the flange 15
The clearance formed between the first and second end faces is shaped such that the clearance gradually narrows outward (the fluid bearing clearance C of the fluid bearing F). The taper seal 27 is formed by such a clearance. The operation and effect of the cover member 28 and the taper seal 27 formed by the cover member 28 are the same as in the third embodiment.

Each embodiment shows an example of the present invention, and the present invention is not limited to these embodiments. For example, the flange portion 1 provided on the shaft 13
5 is not limited to the shaft end but may be near the shaft end. When the overall length (height) is longer than the inner diameter of the sleeve 12, if the sleeve 12 is made of a material having a larger coefficient of linear expansion than the shaft 13, the sleeve 12 will be deformed more than the shaft 13 at high temperatures ( Elongation), it is possible to make the fluid bearing clearance C narrow at high temperatures. that way,
A decrease in the load capacity of the fluid bearing due to a decrease in the viscosity of the lubricant at a high temperature can be reduced. Therefore, even if the ambient temperature changes, the change in the bearing torque is small, and a spindle motor with low power consumption as a whole can be obtained.

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 groove for generating dynamic pressure, the detailed structure of the spindle motor, and the like are limited to the embodiments. 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 is formed by the lubricant reservoir 22 having a fluid bearing clearance C.
If the shape gradually narrows toward
Various curved surfaces may be used.

Further, a small circumferential groove may be provided at the boundary between the outer peripheral surface of the shaft 13 and the conical surface 15f which is a fluid bearing surface as a relief portion for facilitating machining. It may be omitted as in the form. Further, the shape of the flange portion 15 is not limited to a substantially conical shape, and may be a substantially hemispherical shape. That is, the fluid bearing surface may be a spherical surface instead of a conical surface.

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. 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 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, 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.

If 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, in each of the embodiments, 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.

[0075]

As described above, the hydrodynamic bearing device of the present invention has excellent moment resistance, which is important for realizing excellent portability, low power consumption and high reliability, and remains inside the bearing. The effect of the generated bubbles is extremely small.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of a hydrodynamic bearing unit used in the spindle motor of FIG.

FIG. 3 is a sectional view of a spindle motor which is a second embodiment of the hydrodynamic bearing device according to the present invention.

FIG. 4 is a sectional view of a spindle motor which is a third embodiment of the hydrodynamic bearing device according to the present invention.

FIG. 5 is a sectional view of a spindle motor that is a fourth embodiment of the hydrodynamic bearing device according to the present invention.

FIG. 6 is a sectional view of a conventional spindle motor.

[Explanation of symbols]

 12 Sleeve 13 Shaft 15 Flange 15f Conical Surface 22 Lubricant Pool 23 Exhaust Hole 25 Lubricant Supply Path C Fluid Bearing Clearance F Fluid Bearing

Continuing on the front page (72) Inventor Takenobu Otsubo 1-5-50 Kugenuma Shinmei, Fujisawa-shi, Kanagawa Prefecture Nippon Seiko Co., Ltd. F term in reference (reference) 3J011 BA10 BA11 CA03 DA02 JA02 KA04 MA07 MA24 QA03 QA04 RA03 SB02 SB03 SB04 SB19 SB20 SC01 SD01 SE02

Claims (1)

[Claims] 1. A fluid bearing device comprising: a shaft having a flange portion at both ends or in the vicinity thereof; and a mating member facing the shaft via a fluid bearing clearance, wherein the flange portion is substantially conical or substantially conical. A hemispherical shape, the conical surface or the spherical surface of which is arranged on the shaft with the convex direction facing the center of the shaft, and a lubricant reservoir for holding a lubricant provided in communication with the fluid bearing clearance; A fluid reservoir having a shape in which a clearance is gradually narrowed toward the fluid bearing clearance, and an exhaust hole communicating with the outside air is provided in a portion of the lubricant reservoir where the clearance is wider. .