JP2001289247A - Fluid bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spindle motor of high durability and reliability by mounting a lubricant reservoir capable of surely supplying a lubricant to a bearing clearance to compensate the reduction of the lubricant, and having a function to easily discharge residual bubbles in the lubricant. SOLUTION: In this fluid bearing device comprising a shaft 3 having a thrust plate 11 on its one end, and a sleeve 2 opposite to the shaft 3 through a radial fluid bearing R and a thrust fluid bearing S, an annular clearance to be used as the lubricant reservoir 12 is formed on an outer peripheral side of the sleeve 2, and a lubricant supply path 13 communicated to an outer peripheral face 11g of the thrust plate 11 is formed on its one end. A clearance of the lubricant reservoir 12 is gradually narrowed toward the lubricant supply path 13, and a clearance of the lubricant supply path 13 is equal to or slightly larger than a clearance C between the outer peripheral face 11g of the thrust plate 11 and its counterpart 1a to solve the problems.

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 fluid bearing devices for video equipment and office equipment,
The present invention relates to a fluid bearing device having excellent durability and reliability applicable to a magnetic disk device, an optical disk device, a fan motor, and the like.

[0002]

2. Description of the Related Art Conventional hydrodynamic bearing devices of this type include:
For example, there is a hydrodynamic bearing device for a magnetic disk device as shown in FIG. 4, in which a sleeve 2 is fixed to a base 1 and a shaft 3 is rotatably inserted through the sleeve 2. A hub 4 on which a magnetic disk is mounted is integrally attached to the shaft 3.

[0003] The lower end surface of the shaft 3 is a thrust receiving surface 3s,
A counter plate 6 as a mating member having a thrust bearing surface 6s opposed to the thrust receiving surface 3s is fixed to the base 1, and at least one of the thrust receiving surface 3s and the thrust bearing surface 6s has, for example, a spiral motion. A thrust fluid bearing S is provided with a groove 7 for generating pressure.

On the other hand, a pair of upper and lower radial receiving surfaces 3r are formed on the outer peripheral surface of the shaft 3 at an interval in the axial direction, and a radial bearing surface 2 facing the radial receiving surface 3r.
r is formed on the inner peripheral surface of the sleeve 2 as a mating member, and at least one of the radial receiving surface 3r and the radial bearing surface 2r is provided with, for example, a herringbone-shaped groove 8 for generating dynamic pressure. A bearing R is configured.

The hydrodynamic bearing device constructed as described above is incorporated in a spindle motor of a magnetic disk drive, and comprises a stator 9 fixed to the outer periphery of the base 1 and a rotor magnet 10 fixed to the inner diameter surface of the hub 4. The shaft 3 and the hub 4 are integrally driven to rotate by the driven motor M. When the shaft 3 rotates, the thrust fluid bearing S and the radial fluid bearing R
Due to the pumping action of the respective dynamic pressure generating grooves 7 and 8, dynamic pressure is generated in the lubricant in each bearing clearance, and the shaft 3 is not in contact with the sleeve 2 and the counter plate 6 and is supported.

[0006]

However, in a spindle motor employing a hydrodynamic bearing device provided with such a thrust fluid bearing S and a radial fluid bearing R as a bearing, the spindle motor is held in the bearing clearance when used for a long period of time. The lubricant gradually decreases due to evaporation and scattering during rotation, resulting in poor lubrication, and the bearing may be seized in an attempt to extend the life of the bearing.

When the shaft 3 is inserted into the sleeve 2 and assembled, a predetermined amount of lubricant is injected in advance into a closed cylindrical surface in a space surrounded by the inner peripheral surface of the sleeve 2 and the counter plate 6. Then, insert the shaft 3. Therefore, air is easily entrained, and slight air bubbles are apt to remain in the bearing clearance. The remaining air bubbles may expand due to a change in air pressure that may occur when the assembled product spindle motor is transported by, for example, an aircraft, or a rise in temperature during rotation of the spindle motor, which may push out the lubricant in the bearing clearance to the outside. There was a problem. .

Accordingly, the present invention has been made in view of such an unsolved problem of the prior art, and a lubricant is surely supplied to a bearing clearance to compensate for a decrease in the lubricant and to reduce the amount of the lubricant. An object of the present invention is to provide a spindle motor having excellent durability and reliability by providing a lubricant reservoir having a function of easily discharging residual air bubbles.

[0009]

In order to achieve the above object, the invention according to claim 1 comprises a shaft having a thrust plate at one end and a sleeve opposed to the shaft via a fluid bearing. In the hydrodynamic bearing device provided with the above, an annular clearance serving as a lubricant reservoir is provided on the outer peripheral side of the sleeve, and a lubricant supply passage communicating with the outer peripheral surface of the thrust plate is formed at one end of the annular clearance. It gradually narrows toward the agent supply path.

That is, a tapered surface is provided on at least one of the outer peripheral surface of the sleeve or the inner peripheral surface of the mating member opposed to the outer peripheral surface of the sleeve via the annular clearance so as to narrow the clearance toward the lubricant supply passage. To provide a lubricant reservoir. The size of the clearance of the lubricant supply passage is equal to or slightly larger than the clearance between the outer peripheral surface of the thrust plate and its mating member.

The hydrodynamic bearing device of the present invention is provided with the lubricant reservoir, so that the lubricant can be automatically replenished for a long period of time. In addition, at least one of the outer peripheral surface of the sleeve and the inner peripheral surface of the mating member opposed to the sleeve via the annular clearance is provided with a tapered surface in which the clearance decreases toward the lubricant supply passage. And replenishment to the bearing clearance can be ensured. In addition, bubbles are less entrained during assembly, and the entrained bubbles remaining in the lubricating oil are separated by the lubricant pool and discharged.

Further, the size of the clearance of the lubricant supply path is
The gap between the outer peripheral surface of the thrust plate and the mating member is equal to or slightly larger than the clearance between the outer peripheral surface of the thrust plate and the mating member. Bubbles do not remain or collect, so that the phenomenon that the shaft swings slightly during rotation is prevented.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of one embodiment of a spindle motor incorporating a hydrodynamic bearing device according to the present invention. In the drawings, the same or corresponding parts as those in the related art are denoted by the same reference numerals, and detailed description is omitted.

First, the structure will be described. The flange 2f of the sleeve 2 is attached to the inner surface of the rising cylindrical portion 1a of the base 1.
Is fixed. As in the prior art, the shaft 3 is rotatably inserted into the sleeve 2, and the radial bearing surfaces 2 r, 2 r on the inner peripheral surface of the sleeve 2 correspond to the radial receiving surface 3 on the outer peripheral surface of the shaft 3.
r, 3r, and at least one of the radial receiving surface 3r and the radial bearing surface 2r is provided with, for example, a herringbone-shaped groove m for generating dynamic pressure.
Is configured.

A cup-shaped hub (rotor) 4 is integrally press-fitted and fixed to the upper end of the shaft 3.
At the lower end of the shaft 3 protruding through the through hole, a donut-shaped thrust plate 11 is fixed by press-fitting or press-fitting, and faces a counter plate 6 disposed below the thrust plate 11. That is, both planes of the thrust plate 11 are formed as thrust receiving surfaces 11 s and 11 s, respectively, and a herringbone-shaped or spiral-shaped groove (not shown) for generating a dynamic pressure is machined. The thrust bearing surface 6 on the upper surface of the counter plate 6 is provided on the thrust receiving surface 11s on the lower surface side.
s opposes, while the thrust bearing surface 2s, which is the lower end surface of the sleeve 2, opposes the thrust receiving surface 11s on the upper surface side, thereby forming a thrust fluid bearing S.

In the case of this embodiment, an annular clearance is provided between the sleeve 2 and the rising cylindrical portion 1a of the base 1, which is the mating member, and a lubricant reservoir 12 is formed up to the annular clearance. . At the lower end of the lubricant reservoir 12, a lubricant supply passage 13 is opened in an annular shape and communicates with the outer peripheral surface 11g of the thrust plate 11. In addition, an air passage 14 communicating with the outside air is opened above the lubricant reservoir 12. This ventilation path 14 is provided in a bent shape that extends horizontally from the uppermost portion of the lubricant reservoir 12 and rises vertically to the joint surface with the base rising cylindrical portion 1a. As shown in FIG. And an opening at the upper end surface of the joint between the base and the cylindrical portion 1a. When the ventilation path 14 has such a bent shape, there is an advantage that even if a large external impact acts, the lubricant in the lubricant reservoir 12 is unlikely to scatter and flow directly to the outside from the ventilation path 14.

The size of the clearance of the lubricant reservoir 12 is made to gradually decrease toward the lubricant supply passage 13. Here, the outer peripheral surface 2g of the sleeve 2 is tapered. Of course, the inner peripheral surface 1n of the rising cylindrical portion 1a of the base may be tapered, and both surfaces 1n and 2g may be tapered. Thus, the lubricant is smoothly and automatically supplied to the bearing clearance for a long time by capillary action,
The reliability of the device is improved by preventing the depletion of the lubricant in the bearing clearance.

The size of the opening of the lubricant supply passage 13 (the size of the opening clearance) is determined by the outer peripheral surface 11g of the thrust plate 11 and the inner peripheral surface 1n of the rising cylindrical portion 1a of the base 1, which is the mating member. Is equal to or slightly larger than the clearance C between the two. Specifically, for example, the clearance of the lubricant supply path 13 and the clearance C are preferably designed in a range of about 50 to 400 μm. For example, assuming that the clearance C is 50 to 200 μm, the opening of the lubricant supply passage 13 is equal to or larger than 150 μm.
３００300 μm. In consideration of the processing accuracy, it is more preferable that the clearance C is set to 100 to 200 μm, and the opening of the lubricant supply passage 13 is set to a slightly larger size of 150 to 300 μm.

In this manner, the lubricant is easily sucked from the opening of the lubricant supply passage 13 toward the clearance C narrower by capillary action. On the other hand, air bubbles that remain in the device when the lubricant is injected or that collect in the clearance C due to centrifugal force during rotation of the device are replaced with the lubricant to form the lubricant supply passage 13. Since the lubricant moves from the opening toward the lubricant reservoir 12 having a large clearance, no air bubbles remain in the clearance C.

On the outer periphery of the rising cylindrical portion 1a of the base 1,
A driving motor M is formed by fixing a stator 9 having a laminated silicon steel sheet and a winding wire, and facing the rotor magnet 10 fixed to the inner peripheral surface of the hub 4 with a rotor magnet 10 via a gap. It is the same as the conventional one. Next, the operation will be described.

When the hub 4 and the shaft 3 are integrally rotated by the drive motor M, the thrust fluid bearing S and the radial fluid bearing R are pumped by the respective dynamic pressure generating grooves so that the lubricant in the bearing clearance of each fluid bearing is removed. When the dynamic pressure is generated, the shaft 3 floats up and comes out of contact with the sleeve 2 and the counter plate 6 and is supported. In the first embodiment, the lubricant is held on the tapered surface of the lubricant reservoir 12 by capillary action due to surface tension. When the lubricant in the bearing clearance runs short, the lubricant is sucked from the lubricant supply passage 13 toward the narrower clearance, that is, toward the bearing clearances of the thrust fluid bearing S and the radial fluid bearing R, and is introduced into the bearing clearance. Top up until the lubricant is filled.

That is, as the amount of the lubricant in the bearing clearance decreases, the lubricant in the lubricant reservoir 12 is removed from the lubricant supply passage 1.
The lubricant is sucked by a capillary phenomenon into the bearing clearance having a small clearance via 3 and is stabilized at a position where the surface tension of the tapered surface of the lubricant reservoir 12 is balanced. Therefore, the lubricant is automatically replenished by the reduced amount. In this case, since the clearance of the lubricant reservoir 12 is tapered, the lubricant is sucked by the surface tension toward the narrower clearance, that is, toward the bearing clearance. On the other hand, the residual air bubbles entrained during assembly and the centrifugation during rotation. Bubbles gathering in the clearance C between the outer peripheral surface 11g of the thrust plate 11 and the inner peripheral surface 1n of the mating member by force move toward the larger clearance, that is, toward the lubricant reservoir 12, and are separated.
The air is discharged from the air passage 14 to the outside. Therefore, a phenomenon in which the shaft 3 is minutely touched during rotation due to the influence of air bubbles is suppressed. As a result, a reliable spindle motor with high rotation accuracy can be obtained.

Further, since the lubricant reservoir 12 has a tapered shape, even when the apparatus is turned over during transportation or use, the excess lubricant retained in the lubricant reservoir 12 can be prevented from flowing out. can get. FIG. 3 is a view showing a second embodiment of the hydrodynamic bearing device according to the present invention, and is supposed to be provided as a hydrodynamic bearing unit that can be incorporated in a spindle motor.

The hydrodynamic bearing device of this embodiment is different from the first embodiment in that the sleeve 2 has a dual inner / outer structure. That is, a bottomed outer sleeve 2B as a mating member facing the inner sleeve outer peripheral surface 2Ag via a gap is integrally provided outside the inner sleeve 2A, and the outer sleeve 2B and the inner sleeve 2A are disposed between the outer sleeve 2B and the inner sleeve 2A. , A lubricant reservoir 12 having an annular gap is provided. The inner peripheral surface 2Bn of the outer sleeve 2B is a tapered surface.

As described above, the inner peripheral surface 2Bn of the outer sleeve 2B
Is a tapered surface, the size of the opening of the lubricant supply passage 13 is always larger than the clearance C between the outer peripheral surface 11g of the thrust plate 11 and the inner peripheral surface 2Bn of the outer sleeve 2B which is the mating member. . On the other hand, since the size of the clearance C increases as the size becomes closer to the lubricant supply path 13, there is an advantage that bubbles remaining on the outer peripheral surface 11 g of the thrust plate are more reliably discharged toward the lubricant supply path 13. is there.

In addition, in this fluid bearing unit, in order to facilitate the injection of the lubricant, an oil supply hole 16 is provided separately from the ventilation passage 14 and communicates directly above the lubricant reservoir 12 from above. The ventilation path 14 is formed in a bent shape as in the first embodiment, so that the lubricant is hardly scattered from the lubricant reservoir 12 to the outside when receiving an impact. It is easier and more advantageous to insert the needle of the dispenser from above. Also,
After refueling, the lubrication hole 16 is sealed with a ball 17 such as a steel ball or a plastic ball, so that even when an external impact acts, the lubricant does not easily flow out of the lubricant reservoir 12.

Other structures, operations and effects are substantially the same as those of the first embodiment. Note that the specific structure of the hydrodynamic bearing device of the present invention is not limited to the above embodiment, and can be appropriately modified and implemented. Further, the hydrodynamic bearing device of the present invention is not limited to a spindle motor for a magnetic disk device, but can be widely applied to various information devices, audio / video devices, office equipment, etc., such as an optical disk device and a fan motor.

[0028]

As described above, according to the present invention,
It is possible to obtain a highly reliable hydrodynamic bearing device in which the replenishment of the lubricant is ensured, the durability is excellent, the assembly is easy, and the influence of bubbles is small.

[Brief description of the drawings]

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

FIG. 2 is a plan view of the sleeve portion.

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

FIG. 4 is a cross-sectional view of a spindle motor incorporating a conventional hydrodynamic bearing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base (partner member) 2 Sleeve 2A Inner sleeve 2B Outer sleeve (partner member) 3 Shaft S Thrust fluid bearing R Radial fluid bearing 11 Thrust plate 11g Thrust plate outer peripheral surface 12 Lubricant reservoir 13 Lubricant supply path C Thrust plate outer peripheral surface And the gap between the mating member

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ikuki Sakatani 1-5-50 Kugenuma Shinmei, Fujisawa City, Kanagawa Prefecture Nippon Seiko Co., Ltd. (72) Inventor Katsuhiko Tanaka 1-5-50 Kugenuma Shinmei, Fujisawa City, Kanagawa Prefecture No. N-Seiko Co., Ltd. F-term (reference) 3J011 CA02 JA02 KA04 MA03 MA12 MA23

Claims (1)

[Claims] 1. A fluid bearing device comprising: a shaft having a thrust plate at one end; and a sleeve facing the shaft via a fluid bearing, wherein an annular clearance serving as a lubricant reservoir is provided on an outer peripheral side of the sleeve. At one end thereof, forming a lubricant supply passage leading to the outer peripheral surface of the thrust plate, and gradually narrowing the clearance of the lubricant reservoir toward the lubricant supply passage,
A hydrodynamic bearing device wherein the clearance of the lubricant supply passage is equal to or slightly larger than the clearance between the outer peripheral surface of the thrust plate and its mating member.