JPH03260415A - Hydrodynamic bearing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydrodynamic bearing device with excellent durability used in information equipment, audio equipment, etc.

[Conventional technology]

In recent years, as the density of magnetic disks has increased, there has been a tendency for higher track densities to be required. Along with this, in bearing devices for magnetic disks, instead of conventional rolling bearings, hydrodynamic bearing devices with small fluctuations in non-rotational speed synchronous force are being considered.

As a conventional hydrodynamic bearing device for a high-density magnetic disk, one shown in FIG. 5, for example, is known. In this case, a shaft 3 is fitted into an inner diameter surface 2 of a housing l. On the inner diameter surface 2 of the housing 1, cylindrical radial bearing surfaces 4 are provided at two locations spaced apart in the axial direction. On the other hand, the shaft 3 is provided with radial bearing surfaces 5 at two locations spaced apart in the longitudinal direction.
and the radial bearing surface 5 are opposed to each other with a radial bearing clearance 6 interposed therebetween, and constitute a radial bearing R. A herringbone-shaped groove 7 for generating dynamic pressure is provided on at least one of the radial bearing surface 4 and the radial bearing surface 5 (radial bearing surface 5 in the figure). Moreover, on the inner diameter surface 2 of the housing 1, there are 2
Between the radial bearing surfaces 4 and 40, the radial bearing surface 4
A relief portion 8 having a larger diameter is provided.

The lower end of the shaft 3 is a flat thrust bearing surface 9, which forms a thrust bearing S opposite to a thrust bearing surface 11 provided on a thrust plate 10 fixed to the housing 1.

A groove 16 for generating dynamic pressure is provided in the thrust bearing surface 11, and a relief portion 14 having a larger diameter than the lower radial bearing surface 4 is provided at the lower end of the inner diameter surface 2 of the housing. A hub 12 is fitted to the upper end of the shaft 3 so as to be able to rotate integrally with the shaft 3, and a magnetic disk (not shown) is attached to the hub 12.

The axial length L of the radial bearing surface 4 is longer than the axial length l of the dynamic pressure generation groove 7 (L>f), and the dynamic pressure generation groove 7 communicates with the relief part 8. I haven't. This hydrodynamic bearing device is lubricated with an extremely small amount of lubricant held in the radial bearing gap 6 by capillary action.

Note that an air vent hole 1 is provided in the relief part 8 between the radial bearing surfaces 4 and 4, which passes through the housing 1 and communicates with the inside of the hub 12.
3 is provided, and an air vent hole 15 communicating with the outside of the housing 1 is provided in the relief portion 14 on the thrust bearing surface 11. These air vent holes 13, 15 maintain the same air pressure inside and outside the housing 1 even if there is a temperature change, and prevent the lubricant in the bearing clearance from leaking to the outside.

[Problem to be solved by the invention]

In the case of a hydrodynamic bearing device for a magnetic disk, extremely long durability is required, which can last for many hours. However, in the above-mentioned conventional hydrodynamic bearing device, the extremely small amount of lubricant held within the radial bearing clearance 6 evaporates or is scattered when the device is started or stopped, and over time. There is a problem that it gradually disappears and lacks durability.

Therefore, the present invention aims to solve the problem of insufficient durability due to loss of lubricant from the bearing.

[Means for Solving the Problems] In order to achieve this object, the hydrodynamic bearing device of the present invention includes a cylindrical radial bearing, the shaft of which fits into the inner diameter surface of the housing, and which is provided on the inner diameter surface of the housing. The surface faces a radial bearing surface provided on the shaft via a radial bearing clearance, and at least one of the radial bearing surface and the radial bearing surface is provided with a groove for generating dynamic pressure.

The magnetic fluid seal attached to the housing faces the shaft via the magnetic fluid in the seal gap, and a fluid reservoir larger than the radial bearing gap is provided between the radial bearing gap and the magnetic fluid seal. The fluid reservoir communicates with the groove for generating dynamic pressure.

[Effect]

Since the fluid reservoir provided between the radial bearing clearance and the magnetic fluid seal communicates with the groove for generating dynamic pressure, lubricating fluid is supplied from the fluid reservoir to the bearing clearance. In addition, the lubricating fluid does not continue to be lost from the bearing clearance even over time, resulting in good durability.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. Note that the same or equivalent parts as in the conventional art are given the same reference numerals, and redundant explanations will be omitted.

FIG. 1 shows a first embodiment of the invention.

On the inner diameter surface 2 of the housing I, fluid reservoirs 20 each having an inner diameter larger than the radial bearing clearance 6 are provided on the axially outer side of the radial bearing surfaces 4, 4 at two locations. Furthermore, a magnetic fluid seal 21 is attached to the axially outer side of the fluid reservoir 20. This magnetic fluid seal 21 includes a ring-shaped permanent magnet 22 having magnetic poles in the axial direction, and a pair of yokes 23 made of ring-shaped steel plates that are in close contact with both end surfaces of the permanent magnet 22. The inner diameter surface faces the outer diameter surface of the shaft 3 with a seal gap 24 in between. The magnetic fluid 25 filled in the seal gap 24
is a permanent magnet 22. The seal gap 24 is closed by being restrained by a magnetic circuit formed between the yoke 23 and the shaft 3.

The above-mentioned fluid reservoir 20 is sealed on the outside in the axial direction by the magnetic fluid 25 in the seal gap 24, and the radial bearing gap 6 side in the axial direction communicates with the groove 7 for generating dynamic pressure.

Further, in this embodiment, the axial length l of the groove 7 for generating dynamic pressure is equal to the axial length L of the radial bearing surface 4 (L-
1) Groove 7 for generating dynamic pressure, fluid reservoir 20 and relief part 8
are in communication. Further, the air vent hole 13 provided in the relief portion 8 is connected to the air vent hole 1 through a communication hole 27 provided in the axial direction.
5 and is open to the outside below the housing 1. In addition, in order to prevent lubricant from leaking from the air vent hole 13, the groove 7 for generating dynamic pressure in the radial receiving surface 5 is
An asymmetric herringbone groove pattern is adopted in which the groove lengths of the eight escape parts are longer than the groove lengths of the 21 magnetic fluid seals than the bent part 7a.

The shaft 3 and the hub 12 are rotationally driven by a drive motor M. A cylindrical rotor magnet 30 constituting the rotary drive motor M is attached to the inner diameter surface of the hub 12 so as to be able to rotate integrally therewith. A stator coil 31 facing the rotor magnet 30 is fixed to the cylindrical outer diameter surface of the housing 1 .

The case (not shown) attached to the housing 1 is the hub】2
A magnetic disk (not shown) attached to the magnetic disk is covered and sealed.

A lubricant exists in the bearing clearances of the radial bearing R and the thrust bearing S, respectively. Lubricant is also stored in fluid reservoir 20. The lubricant for the radial bearing R may be the same magnetic fluid as the magnetic fluid present in the magnetic fluid seal gap 24 (magnetizable lubricating oil, magnetizable grease, etc.), or a lubricant that is not a magnetic fluid or a magnetic fluid may be used. Grease may also be used. As the lubricant for the thrust bearing S, the same lubricant as that for the radial bearing R may be used, or a different lubricant may be used. For example, it is possible to use grease with little scattering for the thrust bearing S, and use lubricating oil that is easy to inject for the radial bearing R, and so on.

Next, the action will be explained.

When the stator coil 31 of the rotary drive motor M is energized,
Rotational force is generated in the rotor magnet 30, and the hub 12 and shaft 3 rotate integrally. When the shaft 3 rotates, dynamic pressure is generated by the pumping action of the groove 7 for generating dynamic pressure in the radial bearing R, and the pressure of the lubricant in the radial bearing clearance 6 increases, causing the shaft 3 to move against the radial support surface 4 of the housing L. is supported in the radial direction without contact with the On the other hand, in the thrust bearing S, dynamic pressure is generated by the pumping action of the groove 16 for generating dynamic pressure on the thrust bearing surface 11, and the shaft 3 is supported by floating.

Since the dynamic pressure generation groove 7 communicates with the fluid reservoir 20, the lubricant in the fluid reservoir 20 is pumped by the herringbone-shaped dynamic pressure generation groove 7 at the bent portion 7a of the groove.
flow into. The lubricant filling the bent portion 7a of the groove passes through the radial bearing gap 6, moves to the fluid reservoir 20, and circulates therein.

Therefore, the radial bearing clearance 6 is continuously supplied with lubricant from the fluid reservoir 20.

In the thrust bearing S as well, the lubricant is circulated by the pumping action of the herringbone-shaped (or spiral-shaped) groove 16 for generating dynamic pressure.

Further, the groove for generating dynamic pressure is an asymmetrical herringbone-shaped groove, and the longer groove in the axial direction communicates with the relief part 8, so that the fluid reservoir 20 is directed from the relief part 8. The lubricant acts to push the lubricant toward the air vent hole 13. Communication hole 27° prevents air from flowing out through the air vent hole 15.

Also in the thrust bearing S, if the groove 16 for generating dynamic pressure is an asymmetrical herringbone (or spiral) groove, the lubricant in the relief part 14 can be prevented from flowing out through the air vent hole 15. be able to.

The magnetic fluid seal 21 prevents the lubricant from scattering to the outside of the radial bearing clearance 6 when the shaft 3 is started or stopped, and also prevents the lubricant from evaporating to the outside.

Thus, according to this embodiment, the problem of insufficient durability due to loss of lubricant from the bearing can be effectively solved.

Furthermore, since the air vent hole 13 of the relief part 8 is communicated with the outside of the housing 1 to which a closed case (not shown) is attached, together with the sealing action of the magnetic fluid seal 21, the cleanliness required for the magnetic disk device can be improved. can.

Note that the radial bearing clearance 6. is not provided without providing the air vent hole 13 that communicates the relief portion 8 with the outside. The fluid reservoir 20 and the relief 8 may be completely filled with lubricant. In this way, there are no air bubbles in the relief portion 8°, the fluid reservoir 20, and the radial bearing clearance 6, so no lubricant leaks to the outside even if there is a temperature change. Further, the groove pattern of the grooves 7 for generating dynamic pressure provided in the radial bearing R does not necessarily have to be asymmetrical. However, the relief part 8. Assembly without air bubbles in the fluid reservoir 20 and the radial bearing gap 6 requires performing the assembly in a vacuum or in a magnetic fluid, which increases the assembly cost.

FIG. 2 shows a second embodiment.

This embodiment differs from the first embodiment in that a groove 7A for generating dynamic pressure of the radial bearing R is provided in the radial bearing surface 4.

Other configurations and effects are similar to those of the first embodiment.

A third embodiment is shown in FIGS. 3 and 4.

In this embodiment, the lower end of the shaft 3A is fixedly supported on a base 43,
The upper end is fixedly supported by a case 35 attached to a base 43 to increase support rigidity, and is particularly suitable for magnetic disk drives that require high density.

The hub 12 is provided with a cylindrical portion 12A in the center,
A pair of sleeves 36 are vertically fitted onto the inner diameter surface of the cylindrical portion 12A. Therefore, the housing l is the hub 12
and a pair of sleeves 36. each sleeve 3
The inner diameter surface 6 is a radial bearing surface 4 that faces the radial bearing surface 5 with a radial bearing clearance 6 in between. The axially inner end surface of each sleeve 36 is a flat thrust bearing surface 37, and a herringbone (or spiral) groove 38 for generating dynamic pressure is formed therein.

On the other hand, a magnetic fluid seal 21 is attached to the housing 1 on the axially outer side of each sleeve 36 .

Further, a collar 39 having a larger diameter than the radial bearing surface 5 is provided between the upper and lower radial bearing surfaces 5 of the shaft 3A, and both side surfaces of this collar 39 serve as thrust bearing surfaces 40, and the thrust bearing surface 3
7 with a thrust bearing clearance 41 in between.

Note that the groove 7 for generating dynamic pressure formed in the radial bearing surface 5 of this embodiment is an asymmetric herringbone groove, and its axial length l is smaller than the axial length L of the radial bearing surface 4. length<(L<f)L.

Now, when the stator coil 31 (attached to the base 43 via a member 42) of the rotary drive motor M is energized, rotational force is generated in the rotor magnet 30 and the hub 1
2 rotates integrally with the sleeve 36. When the sleeve 36 rotates, dynamic pressure is generated by the pumping action of the groove 7 for generating dynamic pressure in the radial bearing R, and the radial bearing clearance 6 is increased.
The pressure of the lubricant increases, and the sleeve 36 is supported in the radial direction without contacting the radial bearing surface 5 of the shaft 3A.

On the other hand, in the thrust bearing S, the thrust bearing surface 37
Dynamic pressure is generated by the pumping action of the groove 38 for generating dynamic pressure, and the sleeve 36 is supported without contacting the thrust receiving surface 40 of the tail portion 39 of the shaft 3A.

Since the groove 7 for generating dynamic pressure of the radial bearing R communicates with the fluid reservoir 20, the lubricant in the fluid reservoir 20 is absorbed by the bending part of the groove by the pumping action of the herringbone-shaped groove 7 for generating dynamic pressure. 7a. The lubricant filling the bent portion 7a of the groove passes through the radial bearing gap 6, moves to the fluid reservoir 20, and circulates therein. For this reason, the radial bearing clearance 6 is continuously filled with fluid from the fluid reservoir 20:! 4 Lubricant is replenished.

In the thrust bearing S as well, the lubricant is circulated by the pumping action of the herringbone-shaped (or spiral-shaped) groove 38 for generating dynamic pressure.

According to this third embodiment, in order to receive the thrust load near the center of the shaft 3A, the thrust bearing S is replaced with the radial bearing R.
I try to sandwich it between the two. Therefore, when the thrust bearing S is provided at the shaft end, the axial span between the relative axial bearings R can be widened, and the moment rigidity is improved. Further, even if thermal deformation occurs between the shaft 3A and the hub 12 due to a change in ambient temperature, there is an advantage that the change in the thrust bearing clearance 41 can be minimized because the distance between the two upper and lower thrust bearing surfaces 37, 37 is small.

In this third embodiment, all spaces within the hydrodynamic bearing device are filled with a lubricant that is a magnetic fluid, and the thrust bearing S and the radial bearing R are lubricated with the same lubricant. Therefore, there is no need to provide an air vent hole, and it is easy to prevent lubricant leakage and contamination of the magnetic disk. Furthermore, the grooves for generating dynamic pressure in the radial bearing R may be either symmetrical or asymmetrical, but an asymmetrical herringbone groove pattern that pushes lubricant toward the thrust bearing S as in this third embodiment may be used. Then, the pressure of the lubricant in the thrust bearing clearance 41 becomes high, and the lubricant is easily circulated in the thrust bearing clearance 41, which is preferable because it is possible to prevent a small amount of air bubbles contained in the lubricant from accumulating in the thrust bearing S. .

Note that the groove for generating dynamic pressure in each of the above embodiments may be provided on the shaft, the housing and the thrust plate, or may be provided on both. However, if the groove for generating dynamic pressure of the radial bearing R is provided on the shaft or housing where the fluid reservoir 20 is not provided, the groove 7 for generating dynamic pressure and the fluid reservoir 20 as shown in FIGS. Since these can be made to face each other in the radial direction, there is an advantage that communication between the groove 7 for generating dynamic pressure and the fluid reservoir 20 can be ensured.

Further, the groove pattern of the grooves for generating dynamic pressure is not limited to a herringbone shape, but may be a spiral shape.

Further, the fluid reservoir 20 may be provided on the shafts 3, 3A. However, it is preferable to provide it in the housing 1 from the viewpoint of space and prevention of deterioration of shaft rigidity.

〔Effect of the invention〕

As explained above, according to the present invention, a magnetic fluid seal is attached to the housing into which the shaft fits, and the magnetic fluid seal faces the shaft via the magnetic fluid in the seal gap, and the magnetic fluid A fluid reservoir with a clearance larger than the radial bearing clearance is provided between the seal and the fluid reservoir, and the fluid reservoir is configured to communicate with a groove for generating dynamic pressure.

Therefore, lubricant is supplied from the fluid reservoir to the bearing clearance. Furthermore, the lubricant is not lost over time and has good durability.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of the first embodiment of the present invention, FIG. 2 is a longitudinal sectional view of the second embodiment, FIG. 3 is a longitudinal sectional view of the third embodiment, and FIG. 4 is a longitudinal sectional view of the third embodiment. FIG. 3 is an enlarged step view of the main part, and FIG. 5 is a longitudinal sectional view of a conventional hydrodynamic bearing device. 1 is the housing, 2 is the inner diameter surface, 3.3A is the shaft, 4 is the radial bearing surface, 5 is the radial bearing surface, 6 is the radial bearing clearance, 7.7A, 16.38 is the groove for generating dynamic pressure, 20 is the A fluid reservoir, 21 is a magnetic fluid seal, 24 is a seal gap, and 25 is a magnetic fluid. Σ

Claims (1)

[Claims] (1) A shaft is fitted into the inner diameter surface of the housing, and a cylindrical radial bearing surface provided on the inner diameter surface of the housing faces a radial bearing surface provided on the shaft via a radial bearing clearance,
A groove for generating dynamic pressure is provided in at least one of the radial bearing surface and the radial bearing surface, and the magnetic fluid seal attached to the housing faces the shaft via the magnetic fluid in the seal clearance, and the radial bearing clearance A fluid dynamic bearing device in which a fluid reservoir larger than the radial bearing clearance is provided between the magnetic fluid seal and the fluid reservoir communicates with a groove for generating dynamic pressure.