JPH1069714A - Bearing device for magnetic disk - Google Patents

Abstract

(57) Abstract: A magnetic disk bearing device capable of preventing a lubricant of a hydrodynamic bearing from scattering and adhering to a magnetic disk. SOLUTION: A hub 25 is mounted on a base 2 through a thrust bearing S and two radial fluid bearings R separated in an axial direction.
In the magnetic disk bearing device supported by 1, the lubricating oil reservoir 27a between the two radial fluid bearings R,
The ventilation from the lubricating oil reservoir 27a to the outside is shut off between the two radial fluid bearings R and the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a magnetic disk bearing device used for information equipment and the like.

[0002]

2. Description of the Related Art A conventional magnetic disk bearing device of this type is disclosed, for example, in JP-A-1-120418. As shown in FIG. 3, a hub 3 on which a magnetic disk (hard disk) D is mounted is supported by a fluid bearing so as to be rotatable around a fixed shaft 2. That is, the fixed shaft 2 erected and fixed to the base member 1 by means of shrink fitting or the like has herringbone grooves 2A and 2B, which are grooves for generating dynamic pressure, formed on the radial receiving surface on the outer periphery.
The hub 3 has a bearing hole 3A through which the fixed shaft 2 is inserted. The inner peripheral surface of the bearing hole 3A is a radial bearing surface, faces the radial receiving surface via a lubricant, and constitutes a dynamic pressure radial fluid bearing.

[0003] Between the herringbone grooves 2A and 2B, there is provided a ventilation hole 3D penetrating the wall surface of the bearing hole 3A. This is to prevent the lubricant from leaking from the lower end of the hydrodynamic radial fluid bearing due to the expansion of air in the space between the fixed shaft 2 and the hub 3.

[0004] Above the hub 3, a thrust bearing member 4 is provided. The lower surface of the thrust bearing member 4 is a thrust bearing surface, and has a spiral groove which is a groove for generating dynamic pressure. And it opposes the end surface 2C of the said fixed shaft 2 via a lubricant, and comprises the dynamic pressure thrust fluid bearing. In order to facilitate the assembly of the bearing device, the ventilation holes 3C
Is provided.

As a lubricant for the above-mentioned hydrodynamic radial fluid bearing and hydrodynamic thrust fluid bearing, synthetic hydrocarbon oil or a grease using the oil as a base oil is used, and conductivity is imparted as required. Carbon black and the like are added.

When the hub 3 rotates, the hub 3 is radially supported without contact with the outer peripheral surface of the fixed shaft 2 by the pumping action of the herringbone grooves 2A and 2B. Further, in the thrust direction, the spiral shaft provided in the thrust bearing member 4 is floated and supported in a non-contact manner with the end face 2C of the fixed shaft 2 by a pumping action.

[0007]

However, in the above-mentioned conventional magnetic disk bearing device, when starting and stopping the rotation, a small amount of lubricant is present from the ventilation holes 3C and 3D, the gap at the lower end of the hub, and the like. Are scattered, reach the surface of the external magnetic disk D, and adhere thereto. There is a problem that the attached lubricant stains the lubricant previously applied to the magnetic disk surface and adversely affects sliding between the magnetic disk and the head.

In order to prevent the lubricant from being scattered, a magnetic fluid seal may be provided adjacent to the fluid bearing. However, in that case, the axial height of the entire magnetic disk bearing device is increased. Another problem arises.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to prevent a lubricant of a hydrodynamic bearing from scattering and adhering to a magnetic disk. Providing bearing devices for magnetic disks,
It is to solve the above-mentioned conventional problems.

[0010]

SUMMARY OF THE INVENTION The present invention provides a magnetic disk bearing device in which a hub is supported on a base via a thrust bearing and two radial fluid bearings separated in an axial direction. The ventilation from the lubricating oil reservoir to the outside is shut off between the lubricating oil reservoir between the two radial fluid bearings and the outside of the two radial fluid bearings.

According to the present invention, the lubricant in the lubricant reservoir between the two radial fluid bearings does not scatter outside the radial fluid bearings because the ventilation is blocked as described above. This does not adhere to the magnetic disk and does not impair the slidability between the magnetic disk and the head.

In addition, there is no need to provide a magnetic fluid seal adjacent to the fluid bearing, so that the height of the magnetic disk bearing device can be reduced and made compact, and the cost can be reduced.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of the first embodiment of the present invention. A shaft 22 is erected at the center of the base 21. An outer diameter surface of the fixed shaft 22 is a radial receiving surface 23, and herringbone-shaped grooves 24A and 24B for generating dynamic pressure are formed at two positions separated in the axial direction. A sleeve portion 26 is formed at the center of the cup-shaped hub 25 which is turned down. The sleeve part 2
6, a radial bearing surface 2 opposed to the dynamic pressure generating grooves 24A and 24B of the radial receiving surface 23 is provided on the cylindrical inner surface.
7 are provided. Reference numeral 27a denotes a lubricant reservoir at an intermediate portion between the two radial bearing surfaces 27. This radial receiving surface 2
3 and the radial bearing surface 27, the hydrodynamic radial fluid bearing R
Is composed. In this embodiment, the hub 25 is not provided with a ventilation hole.

A disc-shaped thrust plate 29 is fixed to the recess 28 at the upper part of the hub 25. The upper end surface of the shaft 22 is a flat thrust receiving surface 31. On the lower surface of the thrust plate 29 opposed thereto, a thrust bearing surface 32 in which a spiral dynamic pressure generating groove (not shown) is formed is provided. The thrust receiving surface 31 and the thrust bearing surface 3
2 together form a hydrodynamic thrust fluid bearing S. In addition,
In this embodiment, since the thrust bearing is formed separately by using the thrust plate 29, assembly is possible without providing a ventilation hole, and the ventilation hole is not provided in the hydrodynamic thrust fluid bearing S.

Inside the hub 25, a rotor 33 and a stator 34 constituting a motor for driving the rotation of the hub are provided. The rotor 33 is fixed to the inner surface of the hub 25 via a yoke 35. On the other hand, the stator 34 is fixed on the base 21 so as to face the rotor 33 in a plane.

A plurality of magnetic disks D are mounted on the outer periphery of the hub 25 via a mounting member 36. A lubricant is applied to the surface of the recording medium portion of these magnetic disks D. This is because when the head that is in contact with the magnetic disk D in a stationary state and floats in a non-contact state during steady rotation comes into contact with the surface of the magnetic disk D at the start or stop of the rotation of the magnetic disk D, or When contacting the surface of the magnetic disk D during rotation due to some disturbance,
This is for improving the slidability. As the lubricant to be applied in advance, a derivative of a fluoro oil having a polar group (for example, a perfluoroalkyl polyether having a polar group such as carboxylic acid, amine, ester, alcohol, and isocyanate) is preferably used. . Hereinafter, this lubricant is referred to as a magnetic disk coating lubricant.

The space between the hub 25 and the thrust plate 29 and the shaft 22 of the magnetic disk bearing device thus constructed is filled with a lubricant. The lubricant is the same fluorine oil as the magnetic disk coating lubricant.

Next, the operation will be described. When a coil of the stator 34 of the driving motor is energized, a rotational force is generated in the rotor 33. As a result, the hub 25 rotates integrally with the magnetic disk D. Then, the hub 25 is supported in the radial direction by the pumping action of the dynamic pressure generating grooves 24A and 24B in the dynamic pressure radial fluid bearing R while the sleeve portion 26 thereof is kept out of contact with the shaft 22. At the same time, due to the pumping action of the groove for generating dynamic pressure in the hydrodynamic thrust fluid bearing S,
The hub 25 floats in the thrust direction, and is supported without contact with the shaft 22.

Thus, while the hub 25 is rotating normally without contact with the shaft 22, the self-sealing action of the dynamic pressure generating grooves in the dynamic pressure radial fluid bearing R and the dynamic pressure thrust fluid bearing S causes lubrication. The agent hardly scatters outside the bearing. Further, when the rotation of the hub 25 is started and stopped, a small amount of the lubricant passes through the inside of the hub 25 from the lower end portion of the sleeve 26 and scatters outside the bearing, and adheres to the magnetic disk D on the outer periphery of the hub 25. Since the attached lubricant is the same fluorine oil as the lubricant for coating the magnetic disk, the magnetic disk D
There is no risk of impairing the slidability between the head and the head.

Therefore, it is not necessary to provide a magnetic fluid seal for preventing the scattering of the lubricant adjacent to the fluid bearing, so that the height of the device in the axial direction can be set low and the cost can be reduced.

Further, in this embodiment, unlike the conventional example, since neither the dynamic pressure radial fluid bearing R nor the dynamic pressure thrust fluid bearing S is provided with a ventilation hole, when the hub 25 rotates, The lubricant in the bearing is not scattered from the vent hole as in the above. In addition, the hub 25 and the entire space between the thrust plate 29 and the shaft 22 can be filled with the lubricant so that the assembly can be performed so that no air remains.
Therefore, the lubricant does not leak out of the bearing due to the expansion of the air due to the temperature rise.

Further, in this embodiment, since the planar motor is used as the drive motor, a magnetic attraction acts between the magnet of the rotor 33 and the stator 34, that is, between the base 21 and the hub 25. . Therefore, the hub 25 does not come off the shaft 22 during transportation or operation even if the shaft 22 and the hub 25 are not particularly secured.

FIG. 2 shows a second embodiment. In this embodiment, a sleeve portion 40 is provided on the base 21 and a shaft 41 is integrally formed downward at the center of the hub 25 so as to rotate the shaft. Further, the thrust bearing S is provided at the lower end side of the shaft 41, and the ball 43 mounted below the shaft insertion hole 42 of the sleeve portion 40 contacts the shaft end surface 41 a of the shaft 41 to support the hub 25. Is formed. The thrust bearing S is provided with a vent hole 44 for venting air during assembly. This ventilation hole 44
It is open outside the base 21, that is, outside the magnetic disk device covered by an external case (not shown). Therefore, slight scattering of the lubricant from the ventilation hole 44 is allowed.

No vent hole is provided between the two dynamic pressure radial fluid bearings R, and the space inside the sleeve portion 40 is filled with a lubricant to assemble. The lubricant used for the dynamic pressure radial fluid bearing R and the thrust bearing S of this embodiment is another fluorine oil having a lower viscosity than the above-described fluorine oil which is a lubricant for coating a magnetic disk (for example, a linear oil lubricant). This is a mixed lubricant obtained by adding the same fluorine oil as a lubricant for coating a magnetic disk to (fluoroalkyl polyether). Generally, a relatively high-viscosity lubricant is used as a magnetic disk coating lubricant, but by making the viscosity of the bearing lubricant lower than that, there is an advantage that the friction torque of the bearing portion can be reduced. .

As the driving motor, a circumferentially opposed motor is used. A rotor 33 is provided on the inner peripheral surface of the hub 25 via a yoke 35.
A is mounted, and a stator 34A is mounted on the outer peripheral surface of the sleeve portion 40 of the base 21. The rotor 33A is slightly shifted upward in the axial direction with respect to the stator 34A so that a magnetic attraction force acts to prevent the hub 25 from coming off the base 21.

In the second embodiment, since the shaft 41 and the hub 25 are integrally formed, there is an advantage that accuracy deterioration due to assembling as in the case of a separate body is prevented, and that no assembling is required. .

The thrust load capacity is increased by using grease for the dynamic pressure thrust fluid bearing S, and the same lubricating oil as the grease base oil of the dynamic pressure thrust fluid bearing S is used for the dynamic pressure radial fluid bearing R. Alternatively, the friction torque may be suppressed. If the friction torque does not matter, the reverse may be applied.

Further, by making the viscosity of the lubricant of the hydrodynamic thrust fluid bearing S higher than the viscosity of the lubricant of the hydrodynamic radial fluid bearing R, it is possible to reduce the friction torque of the radial bearing while increasing the axial load capacity. Alternatively, the friction torque of the entire magnetic disk bearing device may be reduced as much as possible.

When it is desired to increase the radial load capacity, the viscosity of the lubricant of the dynamic pressure radial fluid bearing R may be made higher than the viscosity of the lubricant of the dynamic pressure thrust fluid bearing S.

In each of the above embodiments, an earth may be provided for bringing the rotating hub 25 into contact with a case (not shown) as necessary. Alternatively, a conductive composite lubricant mixed with carbon black, metal particles, or the like may be used as the lubricant for the bearing.

[0031]

As described above, according to the present invention, since the lubricant in the lubricant reservoir between the two radial fluid bearings is blocked from the ventilation as described above, the lubricant outside the two radial fluid bearings is removed. Therefore, there is an effect that this does not adhere to the magnetic disk and slidability between the magnetic disk and the head is impaired.

Further, there is no need to provide a magnetic fluid seal adjacent to the fluid bearing, and the height and the size of the magnetic disk bearing device can be reduced and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a first embodiment.

FIG. 2 is a longitudinal sectional view of a second embodiment.

FIG. 3 is a longitudinal sectional view of a conventional magnetic disk bearing device.

[Explanation of symbols]

 21 Base 22, 41 Shaft 24A, 24B Groove for generating dynamic pressure 25 Hub 26, 40 Sleeve portion 27a Lubricating oil reservoir D Magnetic disk R Radial fluid bearing

Claims (1)

[Claims] 1. A magnetic disk bearing device in which a hub is supported on a base via a thrust bearing and two radial fluid bearings separated in an axial direction, wherein the two radial fluid bearings are arranged between the two radial fluid bearings. A bearing device for a magnetic disk, wherein ventilation between the lubricating oil reservoir and the outside is blocked between the lubricating oil reservoir and the outside of the radial fluid bearings.