JPH0366915A - Hydrodynamic bearing device - Google Patents

Abstract

PURPOSE:To prevent partial abuting of a bearing surface and contamination due to oil mist by composing a thrust shaft face and a bearing surface of projected and recessed spherical surfaces while providing lubricant, and forming dynamic pressure generating grooves on one of radial shaft face and a bearing surface while providing air. CONSTITUTION:A radial bearing face 23 is formed on an outer diameter face of a shaft 21, while a recessed spherical thrust bearing face 25 is formed on a recession 24 of an upper face center part of the shaft 21. A rotary member 34 is composed of a steel ball 31 and a hub 28. Dynamic pressure generating grooves 39 are formed on a radial recessing face 38 and air exists there. When the rotary member 34 rotates, air pressure in a gap 37 is increased and the hub is supported without contact. Pressure of lubricant in a gap 35 is increased to float the hub 28. Recessed and projected spherical surfaces shows self-aligning function, to prevent partial abutting. Splush of lubricant is captured by the radial bearing to prevent contamination due to oil mist.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a magnetic disk drive (HDD).

The present invention relates to a hydrodynamic bearing device used in a rotary drive device for magneto-optical disks, optical disks, etc.

[Conventional technology]

As a conventional hydrodynamic bearing device of this kind, there is one shown in FIG. 7, for example. This prior art is a hydrodynamic bearing device for a rotational drive device of a magnetic disk drive, and a housing 1, which is a fixed member, has a cylindrical shaft IA in the center, and a cylindrical hole 2 is formed in the axis of the shaft IA. have. A radial bearing surface 4 is provided on the inner diameter surface of this cylindrical hole 2 . A shaft 5 is fitted into the cylindrical hole 2, and a radial bearing surface 6 facing the radial bearing surface 4 is provided on the outer diameter surface of the shaft 5. A groove 7 for generating dynamic pressure is formed in at least one of the radial bearing surface 4 and the radial bearing surface 6 to define a radial bearing length.

Further, a roller 8 is press-fitted into one end of the cylindrical hole 2, and a flat thrust bearing surface 9 is provided on the upper end surface of the roller 8.
is provided. A thrust bearing surface 10 is provided on the lower end surface of the shaft 5 facing the thrust bearing surface 9 .

These thrust bearing surfaces 9 and thrust bearing surfaces 10
A groove 11 for generating dynamic pressure is formed in at least one of the
A thrust bearing S is configured.

A motor stator 12 is attached to the outer diameter surface of the cylindrical shaft IA of the housing 1, and the motor stator 12 is attached to the inner diameter surface of a hub 13 that is integrally fixed to the upper end of the shaft 5.
A motor rotor 14 is mounted opposite to the motor rotor 2.

Bearing clearance of radial bearing length 15 and thrust bearing S
The bearing clearance 16 is filled with lubricating oil or grease as a lubricant.

When the motor stator 12 is energized, the motor rotor 14 rotates together with the hub 13 and shaft 5.

Due to the pumping action of the grooves 7.11 for generating dynamic pressure accompanying this rotation, the pressure of the lubricant in each bearing clearance 15.16 increases, so that the shaft 5 maintains non-contact and moves in the radial and vertical directions. Supported.

[Problem to be solved by the invention]

However, in the conventional hydrodynamic bearing device described above, a perpendicularity between the radial bearing length and the thrust bearing S is required due to its structure.

In the event that the thrust bearing S is installed at an angle with respect to the radial bearing length, there is a problem in that the thrust bearing surface 9 and the thrust bearing surface 10 come into uneven contact, resulting in abnormal wear and abnormal rotation. - Furthermore, since lubricant is used for both the radial bearing length and the thrust bearing S, there is a problem in that it is difficult to completely prevent oil mist from scattering to the outside as the shaft 5 rotates.

As a countermeasure, the problem of contamination due to oil mist could be solved by using gas lubrication for the entire structure, but in that case, the load capacity would be insufficient because the viscosity of gas is extremely small compared to oil, etc., and the bearing device would have to be larger. It is necessary to compensate for the lack of load capacity.

The present invention has been made in view of these conventional problems, and its purpose is to provide self-aligning properties to prevent uneven contact on the bearing surface, and to prevent contamination due to oil mist. It is an object of the present invention to provide a hydrodynamic bearing device that does not cause any trouble.

[Means to solve the problem]

A first aspect of the present invention is that the fixed member has a cylindrical radial bearing surface provided on the outer diameter surface and a thrust bearing surface provided radially inward from the radial bearing surface, and the fixed member is fitted into the fixed member. The rotating member has a radial bearing surface facing the radial bearing surface with a radial bearing clearance therebetween, and a thrust bearing surface facing the thrust bearing surface with a thrust bearing clearance therebetween,
One of the thrust bearing surface and the thrust receiving surface is a concave spherical surface and the other is a convex spherical surface, and at least one of the radial bearing surface and the radial receiving surface is provided with a groove for generating dynamic pressure, and the thrust A groove for generating dynamic pressure is provided in at least one of the bearing surface and the thrust bearing surface, gas is present in the radial bearing clearance, and lubricant is present in the thrust bearing clearance.

In a second aspect of the present invention, the fixing member has a cylindrical radial bearing surface provided on the outer diameter surface and one alignment seat provided radially inward from the radial bearing surface, and the one alignment seat is provided on the outer diameter surface. The thrust bearing member disposed on the center seat has a thrust bearing surface provided on the upper surface and the other centering seat provided on the lower surface, and either one of the above-mentioned one centering seat or the other centering seat is a convex spherical surface and the other is a concave surface, the thrust bearing member is tiltably mounted on one alignment seat via the other alignment seat, and the rotating member fitted to the fixed member is a radial bearing. The radial bearing surface has a radial bearing surface that faces each other through a radial bearing clearance, and the thrust bearing surface has a thrust bearing surface that faces each other through a thrust bearing clearance, and dynamic pressure is generated in at least one of the radial bearing surface and the radial bearing surface. A groove for generating dynamic pressure is provided in at least one of the thrust bearing surface and the thrust receiving surface, gas is present in the radial bearing clearance, and a lubricant is present in the thrust bearing clearance.

[Function] A lubricant-lubricated thrust bearing with a groove for generating dynamic pressure, which has a large unit load capacity and can be made compact, is provided at the center of the fixed member, so that a sufficient load capacity can be achieved with low torque.

The thrust bearing may be configured such that the thrust bearing surface and the thrust bearing surface are tiltable with a convex spherical surface and a concave spherical surface, or alternatively, the thrust bearing surface and the thrust bearing surface are formed with an alignment seat of a convex spherical surface and a concave spherical surface. It has a self-aligning function because it is configured to be tiltable with the aligning seat facing each other. Therefore, even if the thrust bearing S is tilted relative to the radial bearing length, it will be guided by the radial bearing and an alignment effect will act on the thrust bearing, thereby preventing uneven contact between the thrust bearing surface and the thrust bearing surface. .

On the other hand, a radial bearing with a gas-lubricated groove for generating dynamic pressure, which has a small unit load capacity but does not generate environmental pollutants, is installed on the outer diameter side of the cylindrical fixed member with a large diameter, resulting in low A sufficient load capacity can be achieved with torque, and the lubricant of the thrust bearing is effectively prevented from scattering to the outside.

〔Example〕

FIG. 1 is a longitudinal sectional view of a first embodiment of the present invention, in which the present invention is applied to a magnetic disk drive (HDD).

A fixing member 22 is constructed by integrally attaching a large diameter cylindrical shaft 21 to a base 20. Cylindrical radial bearing surfaces 23 are provided on the outer diameter surface of the shaft 21 at three locations spaced apart in the axial direction. Further, a recess 24 is formed at a position spaced radially inward from the radial bearing surface 23, that is, at the center of the upper surface of the shaft 21,
A thrust bearing surface 25 made of a concave spherical surface is provided in the recess 24 .

On the other hand, an inverted cup-shaped hub 28, which is a rotating member, is fitted onto the outer diameter surface of the shaft 21.

A short shaft 29 is protruded from the inner surface of the center of the hub 28, and a steel ball 3 is inserted into the lower end of a through hole 30 passing through the center of the shaft 29.
1 is press-fitted and fixed with a part of the spherical surface protruding. The hub 28 and the steel ball 31 constitute a rotating member 34. A thrust receiving surface 33 is formed by providing a spiral groove 32 for generating dynamic pressure on the protruding convex spherical surface of the steel ball 31.

The thrust bearing surface 33 having a convex spherical surface is inserted into the recess 24 of the shaft 21 of the fixed member 22 and faces the thrust bearing surface 25 with a thrust bearing clearance 35 in between. The concave spherical thrust bearing surface 25 and the convex spherical thrust bearing surface 33 constitute a hydrodynamic thrust bearing S called a so-called spherical spiral group bearing (SGB). In this embodiment, a lubricant 36 such as lubricating oil or grease stored in the recess 24 is present in the thrust bearing clearance 35 .

A radial bearing surface 38 that faces the radial bearing surface 23 with a radial bearing clearance 37 in between is provided on the inner peripheral surface of the hub 28 as a rotating member. A herringbone-shaped groove 39 for generating dynamic pressure is formed in this radial receiving surface 38. The radial bearing surface 38 and the radial bearing surface 23 constitute a hydrodynamic radial bearing length. Gas (air in this case) exists in the radial bearing clearance 37, and gas lubrication is provided.

A rotor 40 is attached to the lower edge of the outer surface of the hub 28 constituting the rotating member. On the other hand, the stator 41 is attached to the inner peripheral surface of the recess of the base 20 that constitutes the fixing member 22.
are attached to the rotor 40 so as to be circumferentially opposed to each other.

One or more magnetic disks D are attached to the outer diameter surface 28A of the hub 28 of the hydrodynamic bearing device configured as described above via attachment members 42.

Next, the effect will be explained.

When the coils of the stator 41 are energized, rotational force is generated in the rotor 40. As a result, the hub 28, which is a rotating member, rotates together with the magnetic disk D.

With this rotation, the pressure of the air in the radial bearing clearance 37 increases due to the pumping action of the herringbone-shaped groove 39 for generating dynamic pressure formed in the radial bearing surface 38 of the hub 28, and the hub 28 It is supported in the radial direction while maintaining non-contact.

In this case, the inner diameter of the hub 28 constituting the radial bearing length is large, and the effective diameter of the bearing is large. Therefore, despite gas lubrication, sufficient radial load capacity is obtained.

In addition, in a magnetic disk drive device, the magnetic disk D
It is necessary to ensure highly accurate coaxiality between the outer diameter surface 28A of the hub 28 to which the radial bearing is attached and the inner diameter surface of the hub 28 that constitutes the radial bearing surface 38 of the radial bearing length. Regarding this point as well, since it is the inner and outer surfaces of the hub 28, it can be easily machined with high precision, and it is possible to reduce fluctuations in the rotational speed component and also to suppress inclination.

On the other hand, in the thrust bearing S, at the same time as the hub 28 rotates, the pumping action of the spiral dynamic pressure generating groove 32 formed in the spherical thrust bearing surface 33 lubricates the thrust bearing clearance 35. The pressure of the agent 36 increases, and the hub 28 floats and is supported in the axial direction without contacting the shaft 21.

In this case, since the thrust bearing S is lubricated using lubricating oil or grease, a large axial load capacity and a radial load capacity can be obtained even though the bearing is compact.

Furthermore, since the thrust bearing S is a spherical bearing, it has alignment properties. Due to the alignment function, even if the radial bearing surface 38 of the radial bearing length is tilted, the phenomenon of uneven contact of the thrust bearing S and deterioration of bearing performance due to unevenness of the thrust bearing clearance 35 is prevented.

As the hub 28 rotates, it is inevitable that oil mist is generated from the lubricant 36 of the thrust bearing S, but in this embodiment, the thrust bearing S is located inside the gas-lubricated radial bearing length. Therefore, the oil mist is caught by the airflow in the radial bearing clearance 37, and is not scattered outside the bearing device, and is removed from the magnetic disk D and the hub 28.
The outer diameter surface etc. are kept clean.

FIG. 2 shows a modification of the thrust bearing S in the first embodiment.

In this case, the steel ball 31 is welded to the shaft 21.

It is fixed by a fixing means such as adhesive, and the fixing member 22
is equipped with a steel ball 31. The thrust bearing surface 25 is a convex spherical surface having a groove 32 for generating dynamic pressure, and the thrust bearing surface 33 opposing this is formed as a concave spherical surface on the end surface of the shaft 29 of the rotating member 34.

This thrust bearing S also has the same self-aligning function as described above.

FIG. 3 shows a second embodiment of the invention.

This embodiment differs from the first embodiment in the configuration of the thrust bearing S and the attachment of the drive motor.

That is, a recess 24 is formed at the center of the upper surface of the shaft 21, and a concave spherical concave surface that becomes one of the alignment seats 50 is formed at the center of the recess 24. A hemispherical body serving as a thrust bearing member 51 having a convex spherical surface and serving as the other alignment seat 52 is tiltably placed on this concave surface 50 . The flat upper surface of the hemisphere 51 serves as the thrust bearing surface 25, on which a spiral groove 54 for generating dynamic pressure is provided, as shown in FIG. 4, for example.

On the other hand, the hub 28 has a cylindrical shaft 55 at the center of the rotation axis.
The shaft 55 and the hub 28 constitute the rotating member 34. The free end surface of the shaft 55 is a thrust bearing surface 33 which is a plane that faces the above-mentioned thrust bearing surface 25 with a thrust bearing clearance 35 in between. This thrust bearing S also has an alignment function with a concave surface 50 and a convex spherical surface 52.

The rotor 40 is attached to the lower end surface of the hub 28. The stator 41 is attached to the upper surface of the base 20 so as to face the rotor 40 in a plane.

Other aspects of the structure, operation, and effects are the same as those of the first embodiment.

FIG. 5 shows a modification of the thrust bearing S in the second embodiment.

In this modification, a combination of a sphere and a disk is used instead of the hemisphere 51 and concave surface 50. That is,
In the hemispherical recess 59 provided in the recess 24 of the shaft 21,
A steel ball 31 is fixed by a fixing means such as welding or adhesive, and the fixing member 22 is provided with the steel ball 31. The upper convex spherical surface of the steel ball 31 serves as one alignment seat 60. On the other hand, a conical concave surface, which is the other alignment seat 62, is provided on the lower surface of the disk as the thrust bearing member 61, and the disk 6
1 has a spiral groove 54 for generating dynamic pressure.
is formed to form the thrust bearing surface 25. The disk 61 of this thrust bearing member is tiltably placed on the convex spherical surface 60 of one of the alignment seats via the conical concave surface 62 of the other alignment seat, and the thrust bearing surface 25 has a thrust bearing clearance 3.
The thrust bearing S
is formed. In this case, the convex spherical surface 60 and the conical concave surface 62 provide an alignment function.

FIG. 6 shows a third embodiment.

In the thrust bearing S of this embodiment, the shaft 21
The upper surface 21A is formed into a conical or spherical surface with a downward slope toward the center to provide a lubricant reservoir. The center portion constitutes a thrust bearing surface 25 having a spherical concave surface, and a thrust bearing surface 3 consisting of a convex spherical surface of a steel ball 31 of a similar spiral group bearing shown in FIG.
3 are facing each other.

Also in this case, an alignment function is provided by the thrust bearing surface 25 made of a concave spherical surface and the thrust bearing surface 33 made of a convex spherical surface.

In each of the above embodiments, the groove pattern of the groove 39 for generating dynamic pressure in the radial bearing length is a dogleg-shaped herringbone groove. However, in addition to this, it may be a ring-bone groove in the shape of an angular shape, or it may be a spiral groove.

Moreover, although the grooves 39 for generating dynamic pressure are formed in two rows spaced apart in the axial direction, they may be formed in one row.

Further, the groove 39 for generating dynamic pressure for the radial bearing may be provided on either the radial bearing surface 23 or the radial receiving surface 38, or may be provided on both.

Similarly, the groove 32.degree. 54 for generating dynamic pressure for the thrust bearing may be provided on either the thrust bearing surface 25 or the thrust bearing surface 33, or on both.

[Effects of the Invention] As explained above, according to the present invention, a radial bearing having a groove for generating dynamic pressure using a gas lubrication system, which has a small unit load capacity but does not cause the generation of environmental pollutants, In addition to being provided on the outer diameter side of the large cylindrical fixing member, a thrust bearing with a groove for generating dynamic pressure using a lubricant lubrication system that has a large unit load capacity and can be made compact is provided in the center of the fixing member. In addition, the thrust bearing may be configured such that the thrust bearing surface and the thrust receiving surface are formed by a convex spherical surface and a concave spherical surface and are combined so as to be tiltable, or alternatively, the thrust bearing surface and the thrust receiving surface are formed by aligning the convex spherical surface. The seat and the concave alignment seat are made to face each other and are configured to be tiltable. Therefore, both radial bearings and thrust bearings have sufficient load capacity, low torque, and self-aligning properties to prevent uneven contact on the bearing surface.In addition, gas lubrication prevents lubricant from scattering on the thrust bearing. It is possible to provide a hydrodynamic bearing device that does not cause problems such as contamination due to oil mist that is trapped in the radial bearing portion of the oil mist.

Moreover, since the coaxiality between the outer circumferential surface of the rotating member and the radial receiving surface can be improved, the runout of the rotating member can be reduced.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of the first embodiment of the present invention, FIG. 2 is a vertical cross-sectional view of a thrust bearing of a modification thereof, FIG. 3 is a vertical cross-sectional view of the second embodiment, and FIG. A plan view of the bearing surface, FIG. 5 is a longitudinal sectional view of a modified thrust bearing shown in FIG. 3, FIG. 6 is a longitudinal sectional view of the third embodiment, and FIG. 7 is a longitudinal sectional view of a conventional hydrodynamic bearing device. FIG. In the figure, 22 is a fixed member, 23 is a radial bearing surface, 25 is a thrust bearing surface, 32 is a groove for generating dynamic pressure, 33 is a thrust bearing surface, 34 is a rotating member, 35 is a thrust bearing clearance,
36 is a lubricant, 37 is a radial bearing clearance, 38 is a radial bearing surface, 39 is a groove for generating dynamic pressure, 50.60 is one alignment seat, 51° 61 is a thrust bearing member, 52.62 is the other one Adjustment seat.

Claims (2)

[Claims] (1) The fixed member has a cylindrical radial bearing surface provided on the outer diameter surface and a thrust bearing surface provided radially inward from the radial bearing surface, and the rotating member that fits into the fixed member has a radial bearing surface. The surface has a radial bearing surface that faces each other through a radial bearing clearance, and the thrust bearing surface has a thrust bearing surface that faces each other through a thrust bearing clearance, and one of the thrust bearing surface and the thrust bearing surface is a concave spherical surface. and the other is a convex spherical surface, at least one of the radial bearing surface and the radial bearing surface is provided with a groove for generating dynamic pressure, and at least one of the thrust bearing surface and the thrust bearing surface is provided with a groove for generating dynamic pressure. A hydrodynamic bearing device in which a groove is provided, gas is present in the radial bearing clearance, and a lubricant is present in the thrust bearing clearance. (2) The fixed member has a cylindrical radial bearing surface provided on the outer diameter surface and one alignment seat provided radially inward from the radial bearing surface, and is arranged on one alignment seat. The thrust bearing member has a thrust bearing surface provided on the upper surface and another alignment seat provided on the bottom surface, and one of the one alignment seat and the other alignment seat is a convex spherical surface, and the other is a convex spherical surface. is a concave surface, the thrust bearing member is tiltably mounted on one alignment seat via the other alignment seat, and the rotating member fitted to the fixed member is mounted on the radial bearing surface via a radial bearing clearance. a radial bearing surface that faces each other and a thrust bearing surface that faces each other with a thrust bearing clearance therebetween; a groove for generating dynamic pressure is provided in at least one of the radial bearing surface and the radial bearing surface; A dynamic pressure bearing device, wherein a groove for generating dynamic pressure is provided in at least one of a thrust bearing surface, a gas exists in the radial bearing clearance, and a lubricant exists in the thrust bearing clearance.